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Siatasese aSceee oe seca ie 505656 ee83 sears e ae se eS ss a sae: 2 Case ic Cone 7 ae is ae ehatetess oe Sia sede Leese aSeca deeds Regen CS o Oe es re tee Poised i ae i Bee : eee Se ae aS teas < Pes esse OS aes ee ee ae co a a eS) Se Sasa ‘ Sissiesss ae aes ea Sie > ae oF ae es eSaiaiekeagse oe ee ets Scie ee Ss ies essa sass Sess: eres piste se ody Sai esis oe ae ees Besnae tied ae ee a i : oe ee ace ieee eens Mosernie ee oe ae fy ated he _ he eager ee oe / 5 - / ee a a fe ee oF SAM eh 2S CORNELL UNIVERSITY. THE Koswell P. Flower Library THE GIFT OF ROSWELL P.. FLOWER FOR THE USE OF THE N. Y. STATE VETERINARY COLLEGE. 1897 co University Library RE 46.F44 eases of the eye and ophthalmosco {HNN I DISEASES OF THE AND OPHTHALMOSCOPY A HANDBOOK FOR PHYSICIANS AND STUDENTS BY DR. a. EUGEN FICK UNIVERSITY OF ZURICH AUTHORIZED TRANSLATION BY ALBERT B. HALE, A.B, M.D, ONE OF THE OPHTHALMIC SURGEONS TO THE UNITED HEBREW CHARITIES; CONSULTING OPHTHALMIC SURGEON TO CHARITY HOSPITAL, CHICAGO; LATE VOL. ASST. IMPERIAL EYE CLINIC, UNIVERSITY OF KIEL WITH A GLOSSARY AND 158 ILLUSTRATIONS MANY OF WHICH ARE PRINTED IN COLORS PHILADELPHIA P, BLAKISTON, SON & CO. IO12 WALNUT STREET 1896 CopyricHT, 1896, By P. BLAKISTON, SON & Co. ——_——_—__——__ PRESS OF WM. F. FELL & CO.) 4220-24 SANSOM STREET, PHILADELPHIA, PREFACE, He who writes a book is accustomed to make apology for him- self in the preface. To this justly beloved custom I also yield, and, for my own apology, I wish to say that our best text-books of ophthalmology are too exhaustive; at least, this complaint is not seldom heard from the pupil to whom their purchase is sug- gested. So it seems that for a compactly written book, in spite of the number of others already at hand, there is still a place. A text-book may be short and yet complete only at a sacrifice of some detail; the author should, perhaps, confine himself to a dry narrative of facts and rules; but to write such a book would cer- tainly be no pleasure to me. I imagine rather a book that would present the connection of things, the whys and the wherefores. Something must be left out, however, and, in deciding on this something, I concluded that pathological statements or hypotheses should receive mention only so far as they were necessary for illus- tration of diseased conditions ; and, further, that a text-book could not replace but could only supplement the clinical study of diseases and operations and the uses of the ophthalmoscope, and that a merely introductory idea of many subjects must be sufficient. I have omitted authorities, since a complete list would be too heavy a ballast, and an incomplete one, as often seen—half a dozen brack- etted names after a statement,—is certainly, at least for the reader, without value. Only when a name came unbidden to my pen or needed mention as a voucher for accuracy, have I woven it in. To make the book easier for the reader I have used a goodly number of colored illustrations and have introduced them into the text; this was a difficult matter, and the reader will probably under- stand why I have not been altogether successful in reproducing the exact colors with perfect accuracy. vii viii PREFACE, [In writing the book, I had a particular pleasure in omitting super- fluous words; but I was soon obliged to decide to put many of them back again in order to make the sense clear. Generally speaking, therefore, I have used only those Germanized words which Hirschberg and other friends of ophthalmological purity of speech have authorized. (This refers, of course, to the German edition. — TRANSLATOR). | A. E. Fick. ZURICH, June, 1894. VORWORT DES VERFASSERS. Im Frihjahr 1895 schrieb mir Herr Dr. Hale, dass er mein Lehrbuch der Augenheilkunde ins Englische zu tibersetzen wiinsche. Mit Vergniigen erklarte ich mich einverstanden, nicht bloss weil die Uebersetzung eine Anerkennung meiner Arbeit ist, sondern weil ich auf diese Art Gelegenheit fand, an meinem Buche dies und jenes zu andern und Erfahrungen zu verwerthen, die seit der ersten Niederschrift von mir oder Anderen gemacht worden sind. Die englische Ausgabe ist also eine Uebersetzung des von mir vermehrten und theilweise gednderten deutschen Textes. Hoffent- lich ist es mir gelungen, die Aenderungen so zu treffen, dass sie gleichzeitig Verdesserungen sind. A. E. Fick. ZuRicH, Juni, 1896. ix TRANSLATOR’S PREFACE. I am responsible for the translation of this work. Except for the few pages relating to heterophoria, I have tried to translate the author’s language so as to convey in English the exact idea expressed by the German. I hope the profession will criticize both the German and the English impartially, so that we may add to the accuracy of oph- thalmology. But I may say that my own best criticism of the book, which, of all German literature on Diseases of the Eye, seems to me to be most suitable for English-speaking students, is evidenced by the fact that I have assumed the loving labor of translating it. My thanks are especially due to Dr. George Reuling, of Balti- more, for his many courtesies, to Dr. W. Franklin Coleman, of the Chicago Post-Graduate Medical School, for his encouragement, and to my cousin, Mr. William Buel Hale, for his kindly aid in helping the book through the press. ALBERT B. HAtg. Cuicaco, August 16, 1896. Venetian Building. CONTENTS. PART FIRST. THE METHODS OF EXAMINATIONS. Introductions soa Gwe SO CR ar ER we I. Acuteness of Vision, Refraction, and Accommodation, . . . 6 Re BOS 1. The Principles of Vision, ... .. Bh EAE A ae eek ae 2; Accommodation; . 3 6.5 ~ 6 ee RR aE ON Oak hs 3. Shortsightedness, Myopia, Acuteness of Vision,. . ....... 4; Flypéermetropia, ce pe a we ee ee 5. Range of Accommodation and Presbyopia, Re yey af Bele 6. Astigmatism, ........ ele ga ge Ti. UightsSense, 2.008 so) ee ae 4 baw gle ~ eae ee a III. Color-Sense, ......-.2-050 24 ok Fhe a esc IV. Indirect Vision and Field of Vision,. .... ene» Gi Ii es savings a Site aes V. Binocular Vision and Squint,. . 2 00... ee ee ee ee 1. Projection of Retinal Images, ....... 0 8... wwe 2. Eye Movements,... ..... ae tk HA Ga sae 3. Strabismus (Squint), . 2... 6... ee eee B. OBJECTIVE METHODS OF INVESTIGATION. I. Reflection from the Cornea—Keratoscopy, ......... +0548 0886 II. Focal or Oblique Illumination, .. 6. 2... we ee ee ee III. The Ophthalmoscope, . .. - 6 ee eee eee ee es eS 1, “Theory; 3 3. #3 ee dee ee gos ee 22k we = we 2. Description of the Ophthalmoscope, a eR ee aps a as er er er 3. Use of the Ophthalmoscope,. . 2... 2. 0 1 ee ee ee (A) Transillumination, . ‘etal Saat (B) Examination of the Fundus of the Eye, . be a (C) Estimation of Refractive Conditions,. ......... (D) Demonstration of Differences of Level in the Fundus, IV. Measurement of Tension, ........ Ca ae ah ee tae Sumi A. THE FUNCTION TESTS. PAGE 15 IOI IOI 114 117 118 II19g 125 135 137 Xil CONTENTS. PART SECOND. THE DISEASES OF THE EYE. TMtHOGUCHONS, ou, Gly ehs el eae ee Rs a eee ae nd ae L. Diseases of the Lids, 6 ee we ee ee I. Diseases of the Skin of the Lid, .... be aati teat Joa aek 1 2. Diseases of the Lid Edge,. . . 2. 0. 0 ee ee ee 3. Diseases of the Tarsus, 4. Malpositions of the Lids and Lid Edges, | ae : eo ; . ; 5. New Growths,. 232 6 2 2 ee 2 e Bw ew eee eS LL, Diseases of the Lacrimal Apparatus, 6s we ee ee ee 1. Diseases of the Lacrimal Glands,. . ... . be eR 2. Diseases of the Lacrimal Passage, LIL, Diseases of the Conjunctiva, . . 6 ee ew ee eee ee es 1. Diffuse Infammations, ....... ROMEUMOTSS eg i Me te we A ee ee . Extremely Rare Diseases,. «2. 2... AnpWN Diseases of The Conneds: sn 4 a Gee BSA SR SS I. Inflammations of the Cornea, . ... 00. 1 ee ee et ee tr, ‘General Considerations,. ss s+ 62 # a ee Be 2. Inflammations With the Formation of Ulcer, . . . 3. Inflammations Without the Formation of Ulcer,. .. .... DY Tapa ess. 35) arse Seas Sop SH ee aE RS HH ae Tae sp RAE pean as Se Mis WOU Sn 5 wah redes ser vege tasi Recta Soe skh GRE LE Taha EN Gan 2. Foreign Bodies (Corpora Aliena), ..........24.- Si BUTTS) ee eye dy gee ee ad BR ks Se Re cape BP eee ae a 4. Frigeration, . 2.0 a 8 aw 6 eH 4 erOiden Gt, ee ae aed ze III. Corneal Opacities of a Non-Inflammatory Nature, . . . IV. Protrusions of the Cornea,. ......... Diseases of the SCler Gs: ea Gh ee Ew eo i OS 1, Sifaeerationts, «<6 ee % % % * & w 2, Protrusions, «ss 6 + «6 so 4 Ge Wade = sea eoe ep yes as a ee eae 4, New Growths; < 6 # oe ew @ 8% SER Boe es Diseases of the Middle Tunic of the Eye (Tunica Media, Tunica Uvea), 1. Anatomical Introduction, ..........0..0.02804 2. Physiological Introduction, ...........-2204- A. CDiséases of thé-Iris,, 3: ceca Gee Gee cde ks Ne Da os eo Sw Bw Se ty Dnt PAY PETeM Ay, gs v2.0 ey cay see 38288 eS con nk a os 2. Inflammations, Rate oatetd oh op. t Nex oo ee Pant oe 3. Injuries and Foreign Bodies,. . . . .. Wn icde Sas ae GER 8. 4. New Growths, jo os 0% = Ge ee ew a ww , 5. Congenital Malformations,. .. .........24. 6. Changes in Size and Motility of the Pupil,. . 2... 2. B. Diseases of the Ciliary Body, ............. SP aasuas 1.0 a: @ychitisy cos. gh Bee Re ee Srey fiesta dane 2. Paralysis and Spasm of the Ciliary Muscle,. . ... . Inflammations With Formation of Follicles, ae . Circumscribed Diseases, lor tae Hiss Ulan Wik Ra 8 gaa ate aah Ba ae) . Injuries and Their Consequences, .. 1... 2. ee eee PAGE 141 143 143 149 154 156 165 167 169 170 181 183 196 206 214 218 219 220 221 221 222 240 247 247 249 251 251 251 257 262 262 263 265 265 265 265 268 271 271 271 280 282 283 284 286 286 288 C. Diseases of the Choroid, . ....... . Sclerochoroiditis Anterior,. . . . . . Choroiditis Exudativa, . Chororetinitis Syphilitica (Foerster), . Choroiditis Suppurativa,. . .... OO OY ANHWNH _ OO WI ANAY Nm Io. B. Diseases 2. 3 4. CONTENTS. Tuberculosis of the Choroid,. . .. ..... Sarcoma of the Choroid, ......... Rupture of the Choroid, ...... . Detachment of the Choroid, 4 . Congenital Defects in the Choroid (Coloboma Choroidese), ed a . Nodules (Warts), 2. 2. 2... 2. ew, ‘ Diseases of the Retina and Optic Nerve, 6... ew eee Introduction, ........... A. Diseases of the Retina, ... 6... ee ee eee Hyperetiia, oe 4 oe ea we a ‘ eee oh Retinal Hemorrhage,. . 2... 2... 7. eee sh eee Inflammations, 54 2.86 3 4 @ 8 ng eB 8 ee aR RS Occlusion of the Retinal Vessels,. ........ Bye AeiGS Pigment Degeneration (Retinitis Pigmentosa), Detachment of the Retina, . ...... Glioma Retine, . 2... 2. eee ee So etn Unjuniesy(.; 7. a. eras Gn re ow ilelat as Seis eA Changes Due'toAge,. 5. 26 6 bee Fe ea Medullated (Opaque) Nerve-Fibers, .. .......0.. of the Optic Nerve,. . .. BS aah a NR ae ea ase GP RGR Sa as . Choked disc (Guanaapepepilic), Bopcb) ey ak ty LIL “Ra ioe, de ee Inflammation of the Optic Nerve (Neuritis Optica, Papillitis),. - Retrobulbar Neuritis,. . 2... 2... ee ee fee Atroplys i e's 4 & ae se Oe ee gS Reet tea ee Diseases of the Lens, se i eee caw was ace; TRETOCGCHOMN, x, a. cdyee Gee. see BI SR es . I. Cataract, o I. 2 3 4. 5 6. II. Aphakia, . . . Generali 5.2 hs So eae Ge thie farsi Sse ok See S . Different Forms of Cataract,. ........ 3 gol et) . Causes of the Formation of Cataract, . . . pie & & 6 Be es Treatment of Cataract, . ....... . Treatment—Before and After, .. 2... 2... eee ee Cataracta Secondaria,. . 2... 1. eee ee ee ee III. Changes of Position of the Lens,. . . 2... 6 1 ee ee eee ee Diseases of the Vitreous; 6 6 0 ee eee ee ee ee ee Jntréduétion;. <¢ 6.2 oe ee Ae ew ee ee eK SE RS Errors of Refraction, . 6 ee ee ee ee ee ee I. Hyperopia (Farsightedness),. .-....+++.. Mee 2 Oh ee II. Myopia (Shortsightedness), 2... - ee e000 te ee es III. Astigmatism, ©... 1 eee ee ee ee I. 2. 3. Regular Astigmatism,. . - - - see ees Irregular Astigmatism, ©. 600 6 te eee ee ce Anisometropia, 2. 6 6 6 ee ee ee ee Amblyopia and Amaurosis, 6 6 0 ee ee ee ee ee ee I. 2. 3. Amblyopia without Lesion, .....-+..- i shenaies titkadss ie ee oe Tntoxications; «246 a 4 ee Xe pe ee 4G Fh Se Weaksightedness as a Sign of Cerebral Disease, ........ 322 322 324 326 327 331 331 333 333 335 343 344 351 354 356 358 360 362 363 XIV CONTENTS. PAGE Cla cOmt a yk se Bose ee Bn ce. HR ER RR a er ee BH 392 Ts Antroductiony. 4 ig a aes. Sa wa we Le » 392 2. Varieties of Glaucoma, . .. 1... ee eee et et - 395 (A) Primary Glaucoma,. . . 2... 6. 1 ee eee + 395 (B) Secondary Glaucoma, . . 2... 1. ee ee ee eee 400 3. Pathological Anatomy, . .. 0 ...-. ws. eee + + « 401 4. Theories,...... Se. GES Ree. te oes - 402 5- Prognosis and Treatment, SLOSS vad wah Way Jant tee set et Vs uae igs Ges Sar ase Gee ae 403 Lntozoa—Parasites in the Eye, . 6 ew ee 407 I, Gysticereus, 2. en sx iy jae ae eer sae Gee Sie jee” ser Se ite Ga) Men cae UNS 407 Il. Filaria (Thread-worms), . OH Aca wees @ eR Blace + = If we remember, more- * N and F in this formula signify Near and Far points. RANGE OF ACCOMMODATION AND PRESBYOPIA. 43 over, that the hypermetropia of an eye is equal to the reciprocal value of the distance of its far point ( = + ), and the myopia of I . another eye = —,’ then we can express A for each particular case in the following manner :— Awe) = Agny — we M Aw = 37 + 4, or, in words: The range of accommodation of an emmetropic eye is equal to 1 divided by the distance of its near point; the range of accommodation of a myopic eye is equal to 1 divided by the distance of its near point minus its myopia; the range of accommo- dation of a hypermetropic eye is equal to 1 divided by the distance of its near point plus its hypermetropia. How do we get the near point of aneye? The simplest method is obviously to approach a test-type to the eye till it can no longer be read; the shortest distance from the principal plane at which a letter can be read must be the near point, but since large type can be read by an eye even when it is not exactly accommodated for it, we must select a letter suitable to the supposed near point and proportionate to the estimated acuteness of vision. Suppose we find that an eye can read Snellen 0.5 (that is, Snellen’s type which a normal eye reads at 0.5 m) at even 15 cm., we must test again with perhaps Jaeger’s Mo. z, or with “ diamond type,” such as is seen onthe second-hand of watches. If we find that such fine type cannot be read at 15 cm. we conclude that the near point lies somewhere beyond the 15 cm. The principal point lies close to the plane which passes through the sclero-corneal border. We can therefore measure the distance from the corneal margin when the eye is looking straight ahead, and call it the distance of the near point. In all text-books of ophthalmology and physics that I have examined, the statement is found that the near point is at ‘‘ some distance in front of the eye.’’ This is too in- definite. Donders! measured to the near point from the anterior nodal point. I consider this incorrect, for my analyses on Af. 2z e¢ seg. have clearly shown that only the (ante- rior) principal point is to be considered. v. Graefe devised a special instrument for the estimation of the near point, the rod-optometer. It consists of a frame in which several 1 Anomalien der Refraktion und Accommodation,’’ II. Auflage, S. 26 u. 32. 44 THE FUNCTION TESTS. black wires are stretched parallel to each other. On the frame is a tape-measure which can be wound up on a spool by a spring. The spool is held at the temple of the eye to be examined, and the frame is approached to the eye till the wires can no longer be distinguished ; then it is withdrawn to the point where they become clearly visible again, and this distance from the edge of the cornea is read off on the tape measure. Another kind of optometer is in more general use than v. Graefe’s, for it furnishes a short cut to the estimation of the refraction of the eye as well as of the visual acuity. Most of these consist of a convex lens of known strength and a series of photographically reduced test- types. fig. rz explains the principle: SS is aconvex lens of zo.0 D. Sucha lens has a focal distance of 74; m., that is 0.7 m. or zo cm. Suppose at the point /, zo cm. from the lens, we place the test-type ; now an emmetropic eye behind the lens can see the print distinctly without using accommodation. If the eye cannot read unless the type is brought ‘nearer to the lens, then the eye must be myopic, and the myopia must be the stronger the nearer the print must be brought to the lens. Again, if the type can be read further from the lens than at / (toward the left in Aig. rr), the eye must be hyper- opic. For example, an eye can read that type corresponding to his Vat g cm. from & (to the left), that is, at a distance of +4 cm. from the lens; the image of the letters pro- duced by S S must be then 35 cw. to the right of the lens, for if f is the focal distance H Ss Ff Fic. 11.—PRINCIPLE OF THE OPTOMETER. of a lens, @ the distance of the object, and 4 that of the image, by applying the formula - = = + 3 we have the following equation :— (1) Pe ok oie SE 10 14 Xt , r I t4—10_ 4 70 If x£ I40 £40 35 The distance of the lens, S'S, from the principal plane, 47 H/, must be considered, but if we make this just zo cm. the problem becomes very simple. In that case every centi- meter that the type is moved from / toward the right indicates 7.0 D of myopia, every centimeter of / toward the left indicates s.0 D of hyperopia. In the example above, for instance, the image lies 35 evr. to the right of S S, or 25 cm. behind the principal plane, /? H, consequently the refractive condition of the eye = = = 4.0 D H, or with test-type g cm. to the left of / refraction equals g.0 D of H. That this rule is universally applicable can be shown as follows : in (1) 4 is the distance of the image from the lens, SS, and equals (2) __@X r0 (3) = roo 3 i += 6+ 10 Therefore = 6=>>F 70+ 400. J RANGE OF ACCOMMODATION AND PRESBYOPIA. 45 Consequently (4)” aX £0 roo a@— 10 Sa rie yy aX 10 r 4)” {eee (5) Y =%4— 10 or — a. The practical significance of the range of accommodation lies in the fact that the range of accommodation is dependent,! not upon the refractive condition of the eye, but upon the age. Foras age increases, the range of accommodation decreases, this decrease in the range of accommodation with increasing age depending upon the changes in the lens mentioned on /. 38. These changes are, to be sure, only completed in advanced life, but they commence in childhood. The contents of the lens capsule grows denser and stiffer and the result is that the lens grows porportionately sluggish and shows less tendency to assume a spherical shape when the Zone of Zinn is relaxed during contraction of the muscle of accommoda- tion. We see, consequently, a decrease in the range of accommo- dation already beginning at a time when the rest of the body, including also this muscle of accommodation, has not yet reached maturity, not to mention passing beyond it. The following table shows the relation of range of accommodation to age :— Age in years. A in Diopters. Age in years. A in Diopters, LO ee, es OR ew 14 AG: 2 eA ak 2. ah ie Gees 15h Mo 0 wR ae SA ee 12 GOs lhe oe a8 20, . da) BRO a ar eS Io FSi « Ge? ae Se ae Saw oe E75 255. 2% ite fe ee OR OOs se este TB! le eg al 30, 3 ‘ a al 7. os ee ap OMG ae ee 2 6 we Ce BS POE. Be os er ae ok + 0.25 4Oy ek oR we A eS OS wa we ee eS) If we can guess at the range of accommodation from a man’s age we ought conversely to guess his age from his range of accommo- dation, and this can be done, although such conclusions are not of rigid or official trustworthiness. The above figures are merely averages and do not exclude deviations, either upward or downward, in individual cases. This is plain when we study the not uncom- mon fact that in some persons the range of accommodation in one eye differs from that in the other.? 1 Only in very high degrees of Ametropia is A less than might be expected from the patient’s age. 2 Schmidt-Rimpler, Arch. f. Ophth., XIV, I, p. 119. 46 THE FUNCTION TESTS. The decrease in range of accommodation by increasing age has, as a consequence, a withdrawal of the near point from the eye (the far point, too, is withdrawn, but only in advanced lifeand toa slight extent). As soon as the near point reaches a distance of 25 cm. the working power of the eye begins to suffer; one holds anything a little further off in order to see it clearly, one prefers to read books and to look at objects in a good, strong light, for then the pupils contract and rays of dispersion are shut out,—in fact, a man whose near point is withdrawn to 25 cv. suffers from that condition called oldsightedness, or presbyopia. It is evident that presbyopia can begin at different periods of life in different conditions of refraction. An emmetrope at about forty- two years becomes presbyopic; a hyperope with 2.0 D at thirty- four years, a myope with 2.0 D not till fifty-four years. Indeed, a myope with M = 4.0 D never becomes presbyopic, for even after the loss of the total range of accommodation where the near and far points coincide, he can yet see distinctly at 25 cz. The troubles of oldsightedness can be removed by extending their sphere of accommodation. Take, for example, an emmetrope of forty-two and forty-three years. He can accom- modate from infinity to 25 cw. (equal to g.0 D); at a distance of 37 cm. he could see plainly if he had accommodative power of a = 3.0 D, this being 3/ of his entire range of accommodation. Now an eye can read continuously and without trouble only at a distance that requires at the most about 24 of its accommodative power. In the above case, therefore, we give a convex lens of 7.0 D. By the aid of this, which brings his far : 100 : : . . point to —— = soo cm., added to his accommodative power of 3.0 D, his near point 100 is brought to ; = 20 em. ; to read at 237 cm. demands an adjustment equal to 3.0 D, but if z.o D of this is supplied by the lens, the patient need use only 2.0 D of accommo- dation, that is, '2 of his range of accommodation. The above explanations show clearly that the same range of accommodation may have a very different significance according as it belongs to an emmetropic, a myopic, or a hyperopic eye. For example, an emmetrope with 4 = 5.0 D controls all space from in- finity to i= 0.2 m. = 20 cit. in front of his eye; his sphere of accommodation is therefore endless. A myope of J7= y.0 D with A = 5.0 D controls only the small interval from his far point at + m, to his near point, = m., that is, 0.25 m.to O.7r m., or fron 25 to rz cm, his field is therefore only rg cm, Finally, a hyperope of H = 4.0 D with A = 5.0 D controls all space from his far point, I hi : I . . _;, to his near point, oy that is, from 25 cm. behind his eye to ASTIGMATISM. 47 everything in front of his eye within roo cm. Every hyperope can therefore accommodate for all objects between infinity and zoo cm., the field of his accommodation, like that of the emmetrope, is immeasurably large, but does not come closer than zoo cm. to his eye, and is consequently defective at just those distances for which exact adjustment is of prime importance. Indeed, when a hyperope is fifty years old and has still an A — 2.5 D at his disposal, his whole range of accommodation does not suffice to adjust his eye for infinity (parallel rays), to say nothing of anything nearer to him. Such a condition is called absolute presbyopia. Many presbyopics do not even ask for glasses. Nature helps them out in this by making the pupil grow narrow and narrower with increasing age, a condition that, in spite of false dioptric adjustment, produces a tolerably sharp vision. The fact that the pupils grow narrower with increasing years can perhaps be explained thus: anyone having a range of accommodation of g.o D reads at 73 cm. distance from the eye by using 4 of this range of accommodation, but with only g.0 D of accommodation at his disposal he must use for the same purpose 3 of his energy. The contraction of the pupil which takes place during accommodation proportions itself doubtless to the impulse given by the will to the ciliary muscle, but is not related to the effect of this impulse on the form of the lens. It is therefore plain that, neglecting other conditions, the pupils will be the narrower the smaller the range of accommodation is. 6. ASTIGMATISM, As. Astigmatism indicates that condition in which a homocentric pencil of rays falling on the eye will not form an image at all, neither in front of, nor at, nor behind the retina. There may be several causes for this. A slight haziness or any such unevenness in the cornea or lens suffices to distort rays from their prescribed course ; such irregular astigmatism, as it is called, will be discussed later. We are now treating of that condition which depends on a distinct deviation of one or all of the refractive surfaces from the spherical form, which is called regular astigmatism. To get an idea of this deviation, take a symmetrically shaped egg (an ostrich egg is a good one), cut it through both lengthwise and sidewise ; the surface of that half cut lengthwise is an ellipse, of that half cut sidewise is a circle. The circumferences of the ellipse and of the circle cross each other at two points; at one of these points put one leg of a compass and describe a circle on the surface of the egg. The shell circumscribed by this. circle is only a small part of the whole, but we can speak of its two principal meridians, although strictly speaking one of them describes an ellipse. Now 48 THE FUNCTION TESTS. notice that the diameters of each of these two principal meridians are different; such a surface is therefore called “ meridionally asym- metrical.” If we image that this meridionally asymmetrical piece of egg-shell is the refracting surface (the cornea) between air and aqueous, such an eye would have a regular astigmatism. We may further suppose the above meridian-asymmetrically curved cornea, with its sharper curved principal meridian, pf, fig. 22, to be perpen- dicular and the weaker curved principal meridian, £4, horizontal; now let us determine what is the refraction of a homocentric pencil of rays in passing through this cornea. The object lies toward the left at infinity on the optical axis of the eye; a pencil of rays parallel to this axis falls on the cornea, pxph; the rays that fall on the hori- zontal meridian, 4%, are marked in red; their meeting point is at /”’. The rays that fall on the sharper curved perpendicular meridian, p/, P h = gta omiecciadkgromia c= Cs. Fic. 12.—Course oF Luminous Rays THROUGH AN ASTIGMATIC SYSTEM. The images of the lines and the ellipses are for the sake of clearness drawn below their true position, obviously must have their meeting point at a shorter distance, say at f’. The question now is, what kind of image appears if we col- lect all the rays passing through the cornea on a screen (the retina at /’) or some other point on the axis of the eye at f” ? The answer to this question can be found by mathematical investi- gation, but as this is rather complicated, we must be satisfied with the answer alone, convincing ourselves of its correctness by a simple experiment with a spherico-cylindrical lens. We find that the rays coming from the left in passing through the meridian- asymmetrical cornea are so refracted that there results a horizontal line on a screen placed at /’, “ the anterior linear focus,” and on a screen at f’’ a perpendicular line, “the posterior linear focus.” If the screen be placed anywhere between /’ and f” there results a circle as at 3 or an ellipse as at 4, but never a true image, and also ASTIGMATISM. 49 the same thing results in case the screen is in front of, as at 7, or behind, as at 6. If the object is approached with uniform speed from infinity, the lines, p’’ and h’h’, separate from each other toward the right, at first very slowly but with increasing speed. This unavoidable separation of these “linear foci” from the retina can, however, be compensated for by accommodation, that is, by shortening the focal distance so that near objects can throw their image lines on the retina, or at least very close to it; this is also the case when the object lies not on the axis, but reasonably close to it. We can give an idea, but not a demonstration, of the origin of ‘‘ linear foci” in the following manner: Imagine the cornea, “php, Fig. rz, cut into segments by perpendicu- lar planes, all of which pass through the middle point of the arc, 44. These segments are all perpendicular, all have the same diameter as #/, and are placed the more obliquely to the optic axis the further they lie away from 4. The pencil of rays which falls upon the principal meridian, 4, will form an image at /’, a second pencil which falls on a segment of the cornea lying to the right of Af likewise forms an image at the same distance, £’, not, however, in the plane of the entering rays but rather inward from it; the more inward the stronger the curvature of 24 is, or, in other words, the more obliquely the perpendicular corneal segment is to the entering plane of the pencil. The result is that near /’ is a series of images which lie the closer to each other the less the difference in curvature between /f and 24. If this distance is o, that is, if the refract- ing surface is spherical, then all these points of the single pencil of rays must unite at /’, or the pencil forms an image! A similar process of reasoning shows that at /’” there results a perpendicular linear focus, only that here the focal points of the rays entering above 7% form images below f’’, and those of the pencil beneath form images above //’. If we remember the statement (at g. 77) that acute vision is possible only in case every object forms a geometrically exact image on the retina, it is clear that an astigmatic eye must see in- distinctly, no matter where the receiving screen (the retina) may be; but the distortion of the retinal images differs greatly according to the forms of the object and according to the relation of the retina to the focal area. Let the luminous object be a horizontal line at infinity and place the retina at the position of the anterior linear foci; in such a case the horizontal line will obviously appear nearly as distinct as to a normal eye. Then every point of the linear object will form a linear image, f’p’; these linear images lie one over the other and produce a complete image, which, apart from its being somewhat lengthened, is of exactly the same shape as in the normal eye. If, however, the object is a perpendicular line it will 4 50 THE FUNCTION TESTS. appear of normal length but distorted in width by £f; consequently a square appears oblong and a circle an ellipse. The relation of the retina to the focal interval of the meridian- ally asymmetrical system distinguishes the kind of astigmatism and its classification. If the retina is to the right of /” (Fig. 72), we have to do obviously with an eye generally myopic in both meridians but of different degree in each; such a condition is called “compound myopic astigmatism” (astigmatismus myopicus compositus). If the retina is at /’’, there is emmetropia in the hori- zontal meridian and myopia in the perpendicular, simple myopic astigmatism (astigmatismus myopicus simplex). If the retina is in front of or at’, we have in the first case compound hyperopic astigmatism (astigmatismus hyperopicus compositus), and in the second case simple hyperopic astigmatism (astizgmatismus hyperopt- cus simplex). Finally, if the retina lies between /’ and /’’, we have myopia in one meridian (here the perpendicular) and hypermetro- pia in the other meridian (here the horizontal),—a condition called mixed astigmatism (astigmatismus mixtus). Astigmatism can be diagnosticated in the following manner: In Snellen’s test-cards there is one with groups of lines, each group having three lines of the same size parallel to each other and with the spaces between of the same width as each line; at each group is a number designating the distance at which the line of that par- ticular thickness ought to be perceived at an angle of 5’. For example, the thinnest lines are marked 6.5, designating that a nor- mal eye ought to distinguish these lines from each other at 6.5 m., no matter whether they are placed perpendicular, horizontal, or diagonal. With astigmatism it is otherwise! An eye suffering from simple myopic astigmatism, having the retina at f’” (Fig. 72), in looking at the card from 6.5 m. can count the lines distinctly only when they are perpendicular. If the card is turned go”, bring- ing the lines horizontal, they appear to this eye to run together as blurred lines. If astigmatism is thus proved to be present, the next step is to find the direction of the principal meridians. Snellen provides for this purpose the card of rays or spokes, as in /vg. 73. If this card is approached from a distance toward an eye with, say, com- pound myopic astigmatism, a certain position will be reached where the posterior linear focus (1 /’ of ig. 12) which at first lay in front of the retina will now fall on it; at this moment the perpendicular ASTIGMATISM. 51 ray appears black (because clear), but all the rest seem gray (be- cause they are blurred) ; and more gray and blurred the nearer the ray approaches the horizontal. The ray that first appears clear and sharp indicates the direction of the principal meridian of greater refraction. If some oblique ray instead of the perpendicular one is the first to become clear, it indicates an exceptional case of astig- matism where the principal meridians are oblique. The test with the figure of rays is obviously applicable to all cases of astigmatism, since each astigmatic eye can be made myopic by holding an ordinary spherical convex lens in front of it ; that is, a compound myopic astigmatism can be induced. Finally, the astigmatism must be measured. From what has been already said, it is evident that the measure of astigmatism must be the difference between the degrees of refraction in the two principal meridians. If, for example, one meridian has M = 1.0 D and the other H = 1.5 D,then As= 2.5 D. The gee TS most direct way to measure astigmatism would be to meas- ure the refraction of each meri- dian separately, and as a matter of fact we can do this by means ofthe stenopaic slit, “Thi little. *e: ts Swetum’s Cane now Tastee Asma. instrument consists of a piece of metal formed like a spectacle glass, with a small slit in it. If this slit is held in front of the eye, all rays are shut out except that thin pencil entering through the slit and through a segment of the cornea corresponding to it. We estimate by means of ordinary spherical lenses the refraction of one meridian, turn the slit around go°, and repeat in the same way the measurement for the second meridian thus exposed. It is evident that in choosing the width of this slit we lie between Scylla and Charybdis ; if the slit is too narrow, say z mm. or less, then too much light is shut out and very disturbing phenomena of diffraction occur ; if the slit is wider, say 2 mm., then one meridian is not altogether isolated, but a segment is exposed in which the asymmetry of this meridian becomes active again. We conclude from this that another method is more serviceable, namely, that astigmatism is measured by the neutralizing cylindrical lens. Figs. 14 and zs show these lenses. Imagine the retina to be at the first 52 THE FUNCTION TESTS. linear focus of the dioptric system (/’ in Fig. 72), and let it be de- sired to form an image of the red rays likewise at /’. It is plain that this can be accomplished by placing in front of the cornea a convex cylindrical lens with its axis perpendicular, because lumi- nous horizontal rays (from right to left) in passing through such a lens are refracted toward the axis, while those from above down- ward (perpendicular) are not refracted ; and in case the lens has a focal distance of x (where = = ra — a all rays will consequently be united at 7’. The rule, therefore, for estimating astigmatism by means of neutralizing cylindrical lenses runs as follows: After deter- mining the presence of astigmatism and the position of the princi- pal meridians in the manner above mentioned, and after determining by a preceding test ! whether myopia or hypermetropia is present, try on a myopic eye a concave cylinder with axis perpendicular to the meridian of greater curvature; the cylinder with which the Fic. 15.—A Concave CyLinpgER. CYLINDER. best V is contained measures the degree of myopic astigmatism present. Try on a hypermetropic eye a convex cylinder with axis perpendicular to the meridian of lesser curvature; the cylinder with which the best is obtained measures the degree of hyper- opic astigmatism present. If there is mixed astigmatism, concave and convex cylinders must be tried with axes as above, till the best V is obtained. Such examinations require patience and a grasp of the theory of - the subject on the physician’s part. In many cases, especially of hyperopic astigmatism, a good result cannot be obtained without atropin or homatropin, since every effort of accommodation, though it may not change the astigmatism itself, must alter the relation of the image to the retina; a given lens will therefore seem to effect a good result at one moment and a bad result at another. 1 Generally we use for preliminary tests as to the nature of a case the objective methods of examination described on /. 97. LIGHT SENSE, 53 II. LIGHT SENSE. By light sense we mean that ability of the eye to distinguish different intensities of light,and it is therefore the essence of all vision, since even the letters and figures of a Snellen’s test-card are obviously recognized by the difference between the black of the letters and the white of the background. Consequently, the acuteness of vision of an eye cannot be estimated without call- ing the light sense into play. The converse, however, is possible, for we can estimate the light sense without reference to the acute- ness of vision. Since Fechner’s time a distinction is customarily made between the sense of stimulation and the sense of contrast. The sense of stimulation expresses the power to distinguish the effect produced by the smallest possible quantity of light when all else is absolutely dark. The sense of contrast expresses the power to distinguish the effect produced by the smallest possible differ- ence in intensities between two unequally illuminated objects. This has been called a superfluous refinement, as the ability to distinguish a shade of light from absolute darkness is only a step in the functional distinction of more from less light; but it is. worthy of consideration that to a certain extent there is an influ- ence of one illuminated area of the retina upon another, and it is therefore a different matter whether I compare the illumination of two objects or whether I distinguish one single bright spot in an otherwise absolutely dark space. Moreover, it is maintained (though disputed by some) that in certain diseases absolute and relative functional activities are modi- fied quite independent of each other, but the most convincing argu- ment against any essential unity between them lies in the fact that the sense of stimulation becomes greater with a decrease in the illumination. The sense of stimulation can be tested by Foerster’s photometer. This consists of a box $ m. long, + m. broad, and 4 m. high, painted black on the inside. On one side are two peek holes, @ a, for the eyes to be tested, witha curtain, 4 4, to shut off either eye at will. Next to these holes is a window, ¢, covered with oiled paper and so arranged by movable shutters, dd, that by turning the screw, e, a square hole of any desired size is adjusted at the window. The size of this hole can be read off on the scale, f, which is connected rigidly to the upper shutter and slides on a standard below. The 54 THE FUNCTION TESTS. little window, c, admits light from a candle placed in a separate com- partment, g, so that no light is thrown directly upon the eye under examination. On the wall opposite the peek holes there are black marks, 44h, on a white ground. The test consists in determining that size of window at which the black marks on the white ground become noticeable. The size of the window is the measure of the amount of light entering the box, and this amount of light that makes the marks visible measures the sense of stimulation of the retina. For example, if one eye can see the black marks when the size of the window is 2 sg. mm., while another does not see them till the window is 20 sg. mm., the functional activity of this last eye is Fic. 16.—Forrster’s PHOTOMETER. Represented here with the doors open. When in use both doors are closed. ten times greater, its light sense ¢ez times smaller than that of the first eye. In experimenting with this instrument it will soon be noticed that the retinal activity in the same eye is distinctly affected by the conditions of illumination under which it was placed immediately before the trial. If a patient is led from daylight into the dark room where the instrument is, and tested at once, the size of the window (c) must be quite large in order to make the marks visible, but at every repetition of the test the opening will be smaller, until finally, after something like half an hour, each test will give approx- imately the same result. We conclude from this that with the LIGHT SENSE, 55 exclusion of all extraneous light a change takes place in the eye, consisting of an increase in the sensitiveness to light (measured as above). This change in the eye implies an adaptation to extrane- ous illumination, or the lack of it. In passing from light to dark- ness this adaptation takes place at first very quickly, but soon be- comes slower, though an essential equilibrium is never obtained even after prolonged seclusion in darkness. The same conclusion is reached from the circumstance that even in complete darkness we are conscious of continually changing subjective light phenomena. This act of adaptation every one has doubtless observed in his own case. In going some summer’s day from the brightness of sunlight into a dark room protected by cur- tains and blinds, one can at first see nothing at all ; but objects in the room soon become visible, and after a quarter of an hour one can see in the dim light as well as in the day- light before. We have only presumptions of what this adaptation depends on. One circumstance, though probably not the essential one, is the play of the pupil that widens in the dark, and to that extent admits more light into the eye from any illuminated object. It is probable that the essential factor in the process of adaptation is to be found in the retina ; we can imagine on the one hand a movement of the pigment of the epithelial cells (external retinal layer, 7g. 770), and, on the other, a new formation and collection of visual purple in the outer elements of the rods. The sense of contrast ‘of an eye can be measured by Masson’s disk. This instrument is constructed as follows: A black disk and a white one of equal size have in the center a hole through which passes an axle. Both disks have a slit from the center to the cir- cumference, and the disks are movable, so as to admit of forming with the uncovered parts a black and white disk which can be ad- justed to give any required proportion of black or white. Ifnow the axle is revolved with the two disks, the resulting effect is no longer black and white, but gray, and becomes grayer in proportion as white preponderates over black, or vce versa. If a third and smaller black disk is now fastened upon the axle, when this is revolved we see an interior black disk surrounded bya gray edge. The rela- tive functional activity for light perception, that is, the sensitiveness of the retina to contrast, can be measured by the amount of white in the large white disk, which can be left uncovered by the large black disk before the gray edge around the central black disk ceases to be distinguishable. Besides Masson’s disks and Foerster’s photometer, there are other methods for testing the light sense, by which the acuteness of vision is estimated at the same time. A mere mention of the principle must suffice. 56 THE FUNCTION TESTS. In the ordinary Snellen’s test-cards the black letters are about sixty times less bright than the white background.’ Now, this re- lationship can be changed by using, instead of black letters, gray letters of different shades on either white or black ground. The less the difference required between the brightness of the letters and that of the background, to make the letters discernible to the eye, the greater is the sensitiveness of the retina. Finally, the method may be tried of testing by Snellen’s cards in reduced light, either in a darkened room or by placing smoked glasses before the eye to be tested. In these experiments three functions come into play— (1) Veston. (2) Light-sense. (3) Adaptation. At the first glance this might seem inappropriate, but these dif- ferent functional tests admit of determining one condition, or at least of investigating its degree, that is, the condition of hemeralopia or night-blindness. This is present when sight is relatively worse in diminished light than would be the case in a healthy eye with the same illumination. Hemeralopics are therefore about as help- less as the blind in the evening twilight or in the light of street lamps, although in good daylight they may have normal vision. Hemeralopia was formerly called a reduction in the sense of light with slow adaptation, but recently Kuschbert, and especially Treitel, have declared that it depends particularly upon diminished adapta- tion or a total absence of that function. Supposing that this view is correct, the hemeralopic must have in good daylight equally as good contrast sense of the retina as the healthy eye has, that is, he must be able to distinguish as different in brightness two objects which differ only z4_ in their objective illumination ; this does not seem, by any means, to be always the case. The demonstration of hemeralopia is often unnecessary, since the patient probably comes to the physician complaining of night- blindness. 1 According to photometric comparisons between black and white papers made by Aubert. COLOR-SENSE, 57 III. COLOR-SENSE. Color-sense is taken to mean that ability of the visual apparatus to respond with sensations of special and individual character to stimulation by light of various wave-lengths. Light rays with wave-length .00069 mm. give the sensation of red; rays of .00039 give the sensation of violet; rays of wave-lengths between these give sensations of yellow, green, blue, etc. We make the most extensive use of this power of our eye. Not only does the artist who revels in the glorious coloring of a good painting, or the lover of nature who delights in a fair landscape or a gay flower garden, use their color-sense for enjoyment, but others also employ it in soberer professional duties. Mosaic workers, weavers, deco- rators, railway and marine employees can hardly carry on their vocations without the ability to distinguish colors. We can com- prehend, therefore, why the ophthalmologist is often asked whether or not the color-sense is normal. One might suppose that the answer to this question needed no physician’s help, but that it would suffice to lay before the patient any colored objects, like bits of paper, and to have him select the colors by name. This is a great error. Indeed, it is often very hard to detect this failure in color-sense—to demonstrate color-blind- ness or a diminished color-sense, color-amblyopia. The color-blind have learned, often without realizing it, to conceal their shortcom- ings, and by heightened attention and the use of the light-sense to satisfy all the demands of existence with reference to the recog- nition and designation of colored objects. A man, for example, who is incapable of perceiving red—“ red-blind —does not see a beech leaf before him in its real coloring, although when ques- tioned as to its color he may answer “red-brown.” He knows that beech leaves are sometimes red, and recognizes this leaf by its lesser brightness quite as well as the normal person perceives the proper color. It is particularly difficult to unmask color-blind- ness or color-dulness when the patient, through fear of losing some position or other, calls all his wit into play in order to stand the test. It must be noted, however, that the uneducated are easily led astray by embarrassment or perhaps by mere lack of words, and unintentionally give a false name to a color. Most methods of testing for color-blindness, therefore, avoid mentioning the names of colors, but demand that individual colors be distinguished from each other. 58 THE FUNCTION TESTS. A simple and practical, but by no means a very sensitive, method is Seebeck’s+ “ qwool test.” It consists of a collection of various colored worsteds about zo cm. long, and the thickness of the finger. It contains, besides the spectral colors of red, orange, yellow, green, blue, and violet, the mixed colors, purple, rose, and gray, and there are four or five different shades of each color. In good daylight give the patient the bright gveen worsted in his hand with the other skeins scattered on a white or black, or at any rate on a colorless ground, and without calling the colors by name ask him to sort out all the colors like the sample without reference to the degrees of tints. One with normal sense disposes of this problem in a few moments, sorting out all the greens without hesitation or delay. But the color-amblyopic acts quite differently. The greens of the collection that are the same as the sample skein he matches very naturally, but at dark green he stumbles, calls it a match, and puts it back again ; then he picks out a gray, and finally even a red is laid inde- cisively by the green sample. This settles the question. In matching red and green and gray he has shown himself as red- green blind! If, however, he has withstood the first test well, let him proceed to the second and more difficult one, in which he must match all the dark and light shades with a rose skein. Rose is, like purple, a mixture of red and blue. The red-blind patient cannot detect reds, and matches blues with the sample; the blue- blind matches red with it. In the same way a red-blind patient matches blues with violet, the blue-blind matches red with it. A second test, depending upon the confusion of colors consists in having the patient read colored letters on a background of equal brightness in tone but of the complementary color, so that the letters must be distinguished by the specific color effect, not by a background of less or greater brightness. This is a very exacting test to withstand satisfactorily. Stilling, who devised it, was so successful with his pseudo-isochromatic cards that even the normal eye had difficulty in deciphering the letters. The surface of the card is divided into small squares or into quadrate fields with rounded corners (fig. 77). The color of most of the squares is a delicate green, but there are some of a delicate red forming the letter E; there is thus a red E ona green background, which for one who is red-green blind is invisible. 1 Often called Holmgren’s, but Holmgren first applied it extensively. COLOR-SENSE. 59 A third method depends on the fact that a gray object on a red ground appears green, on a green ground red, on a blue ground yellow, and on a yellow ground blue—the effect of contrast giving it the complementary color. This fact can be made use of by means of H. Meyer’s test, which consists in covering with tissue paper a piece of gray paper lying on ECE OCS Meceeecesigtgtetgteene, COD OPO OW OO 04 EMO OM UO, CPO MMV OVODOO4 VO UO OOD WO 0.0 .@ COO COLO. COO, MOM COPD LLL OOO, aeacecorecee, rereresete ces os %. 60 O'8' a LY dos Ase erg SONOS Fic. 17.—EXAMPLE OF a STILLING Carp. a colored background. The “induced” color shines through the tissue paper, often with a greater intensity than that of the primary background, but is apparent only to the eye possessing normal color- sense. This method has been made use of by A. Weber, v. Bezold, and Pflueger as a test for color-blindness. Pflueger’s cards for testing Fic. 18.—EXAMPLE OF «a PFLUEGER CaRD. the color-sense have gray figures, letters, or marks on a colored and equally bright ground (fig. 78). The patient is to decipher these through one or two sheets of tissue paper. The normal eye sees the gray figures by contrast in the complementary color, and recognizes them without difficulty. The color-blind, on the contrary, sees nothing at all of the letters 60 THE FUNCTION TESTS. through the tissue paper. H.Cohn, who has had great experience in testing for color-blindness, declares that Pflueger’s cards are the surest and quickest means of detecting total defect or even dulness of color-sense. The three methods mentioned above are for the purpose, and generally have the result, of determining the presence of color- blindness or color-amblyopia. The ophthalmologist needs at times, however, a method for measuring the color-sense of the patient. Donders has suggested such a method. The principle of it lies in the fact that the color of an object is recognized by a normal eye only when this colored object is seen at not too small an angle. The minimum visual angle is different for different colors; supposing that colored areas are placed on a black ground, the necessary visual angle increases in the direction of the spectrum, that is, for red it is the smallest, for violet the largest. If one places on a blackboard colored squares or disks of equal size, the normal eye recognizes each color at its particular distance, and a color-ambly- opic eye recognizes and names those disks for whose color it has not a normal sensitiveness only at shorter distances and at a greater visual angle. Obviously, then, color-sense is the duller the smaller the distance at which a color is first distinguished. I a? ee Donders expresses this by the formula: & = a X< pr, in which 2 signifies the color discriminating power (to be tested), # the diameter of the test object, d, as in the formula for V, the distance of patient from the test-card; but D loses the significance of the formula V = # and is by Donders used to signify the distance at which a normal eye with 4 = 7 ought to recognize the color of an object of 7 sg. mm. surface area. To these different values of Din the V formula and in the 4 formula are to be ascribed so many confusing statements by authors. Another difference between the formulz for color-sense and for acuteness of vision is the fact that #, d, and D are squared (as above) ; this rests on the circumstance that the essential measure for color-sense is to be found in the amount of color reflected sufficiently to produce a color sensation, and in this case the amount of color reflected increases as the surface of the object, therefore as the square of the diameter. Tonders’ method has been recently taken up, developed, and warmly recommended by Wolfberg. He uses red, yellow, green, and blue cloth disks on a black ground; the smallest red and yel- low circular disks have a diameter of 2 mm., the smallest dark green and blue a diameter of 7 sz. There are other disks of z8 mm. diameter, and finally squares zoo mm. on a side. The abbreviations are respectively: 1°, yl’, gr’, bl’, etc. By means of these colored disks and a table worked out by Wolfberg it is said to INDIRECT VISION AND FIELD OF VISION. 61 be possible not only to measure ina very short time the color-sense present, but also to diagnosticate whether discoverable dulness of color-sense rests upon errors of refraction, or upon cloudiness of refractive media, or upon diseases of the nervous apparatus. For example, an eye with a V = 2 ought to recognize 7” in 3.25 m., and 6d" in 3.5 m., in case the imperfect vision depends upon short- < recognizes 7? and 4/7 only within 2 ut., when the imperfect vision depends upon cloudiness of the > does not é I2 recognize 7 and d/’ further than 2 #. it certainly points to defect of color-sense. It is clear that this method of investigation must be extremely valuable in cases where the question is whether any other disease besides cloudiness of the lens is present, or whether the parts of the eye back of the cloudy lens are healthy or not. Nevertheless, the trustworthiness of the whole method has been strongly denied by Herzog. The personal differences in color-sense, as H. Cohn showed more than twelve years ago, are extraordinarily great—always greater than the differences in vision. If, therefore, the ophthal- sightedness; an eye with V= refractive media; and, finally, if an eye with V = mologist cannot conclude from the V = = that an eye is normal in every respect (for it might have V = 2 with a weak concave or convex lens), then it is still less admissible to conclude that the eye is normal in every respect even though 7 and 4/7 can be recognized at 5.5 m. Wolfberg himself acknowledges that a good daylight illumination is indispensable for the success of his color test, and since this cannot always be controlled, the practical appli- cation of Wolfberg’s tests is essentially restricted. I do, to be sure, make use of this test in cataract cases and in diseases of the fundus, but I confess I do not get the continued good results that Wolf berg claims. IV. INDIRECT VISION AND FIELD OF VISION. In the previous section the dioptrics of the eye and the functions of the retina have been discussed for direct vision only. , An object is seen directly when it lies on a line connecting it with the nodal point and the macula lutea of the eye. In this fourth section we must examine acuity of vision, perception of light, and perception of color for indirect or peripheral vision. 62 THE FUNCTION TESTS. The difference between direct and indirect vision can be illustrated in the following manner: Lay on a printed sheet an unprinted sheet with a point in the center ; look at this point and for an instant draw the unprinted sheet away; if the sheet is moved back and forth quickly enough there is no time, even if the eye is moved, to trace out the whole line or even a word; consequently only so many letters will be recognizable as lie at the spot of clearest vision. Ata distance of about 30 cm. we could read only four or six letters of ordinary type; therefore, in case the glance is directed to the end of a long word the word itself cannot be read. Another experiment, applicable off-hand, will illustrate the importance of indirect vision. Look through a tube of any kind and hold the other eye shut; direct vision has not been impaired, but at the same time one is nearly in the condition of a blind person when it comes to finding one’s way about the room, on account of the complete absence of peripheral illumination. Indirect vision, therefore, serves to give us a general idea of our surroundings and to call our attention to important things that we at once look at and then, by means of direct vision, observe more accurately. The examination of the visual acuity of the peripheral parts of the retina must, in any case, begin by determining the refractive con- dition of the eye with reference to this retinal zone. On Z. 78 it has been explained that in general a centered system of spherical refracting surfaces produces images only of such objects as lie close to the axis of this system. What images result from objects that do not fulfil this condition; that is, that lie at a distance from the axis? The question is relatively easy to answer in the case of an aphakic eye when there is only one refracting surface. The answer is that a homocentric pencil of rays falling on the cornea from the side is refracted astigmatically. In case the object lies at infinity and the cornea has a curvature sufficiently strong to make the eye emmetropic, the posterior focal point of a pencil of rays would fall in front of the retina and only extremely indistinct vision would be possible. Complicated calculations have shown that with the con- ditions that accompany the really emmetropic eye, that is, with the proper refraction at the cornea and at the anterior and posterior lens surfaces, the posterior focus will lie on the retina ; indeed, tak- ing into consideration the fact that the lens is of a stratified struc- ture, the result is that the linear foci fall exactly on the retina; in other words, the eye, thanks to the numerous refracting surfaces, is periscopic—that is, sharp retinal images are produced even from objects lying at one side. With the aid of the ophthalmoscope the INDIRECT VISION AND FIELD OF VISION. 63 peripheral parts of the fundus can likewise be seen clear and undis- torted, a fact that harmonizes with these theoretical deductions. To be sure, one sees quite well the peripheral parts of the aphakic eye, although theoretically this ought not to be the case. In the emmetropic eye the periphery of the retina is easily exam- ined, and, as Parent has found, is somewhat more astigmatic than the region of the macula. Axis myopic eyes may have some hypermetropia at the periphery, a fact easily understood when we consider the smaller transverse diameter of the longer bulbus. In hyperopic eyes, on the other hand, the difference between the trans- verse and the longitudinal diameters is but slight. The first requisite of good vision is therefore complied with, as far as concerns the periphery of the retina, but the acuity becomes proportionally less as the edge of the retina is approached. According to Becker, the retinal image of any surface that is seen at a visual angle of z° covers exactly that part of the retina which has Y= +7. From here toward the peri- phery the acuity of the vision of the retina decreases in the following manner :— 1.5 ° toward the periphery V = 3 2.0° ‘“c “ “ v= ZF 3 ° bce ‘cc “cc or i 2.5 v= These figures correspond to angles above, below, to the right, to the left from the center of the retina. Further toward the periphery V decreases more rapidly above and below than to the right and left. At an area on the retina = 45° from the center V is only iF 100 e Earlier investigators, Foerster and Aubert, have also found a similar reduction of Vin the peripheral areas of the retina. The explanation of the reduced sharpness of vision at the peri- phery lies obviously in the arrangement of the retina, since a great distinctness in seeing side objects is unnecessary for us. Conse- quently but little account need be taken by the ophthalmologist of peripheral vision. It is remarkable that light perception in the retinal periphery is in inverse proportion to the acuity of vision of the same parts. Light sense measured by its function of stimulation from the macula lutea toward the edge of the retina becomes greater in- stead of less. We are convinced of this, if, in coming from day- light into a dark room, we look at a weakly illuminated object, say a small piece of luminous phosphorus. Looked at directly, it is invisible ; but when we turn partly away from it, it springs into view! 64 THE FUNCTION TESTS. This fact has long been known to astronomers, and was referred to by Arago. It was noticed that certain dim stars, the moons of Uranus, for example, were visible only when one directed the tele- scope to one side of them. This weak functional activity of the macula lutea was explained as depending on slow adaptation, but investigation has shown that even after several hours’ rest in a dark room, the light sense of the retinal center still remains the less, that of the periphery the greater. Recently one investigator (Mueller-Lyer) has had the self-denial to keep his head stuck in a dark box for eight hours, and the reward for his endurance was the conviction that even then the retinal periphery remained more sensitive to light than the center. The fact that the center of the retina is less sensitive to light than its periphery depends most probably on the histological structure of the retina itself. In the center of the retina there are only cones. Now, according to J. v. Kries, we have in the rods and cones two distinct apparatuses lying side by side, these differ- ing not only anatomically but functionally. The rod apparatus can conduct only light sensations, but is so perfectly adapted for this purpose that it responds to light stimulations which have no effect on the cone apparatus. The consequence is that the rod apparatus plays its principal part in weak illumination, and is there- fore most completely developed in animals that seek their food at night, like the mouse, bats, cats, moles, and owls. Conversely the cone apparatus is capable of responding both to light and color sensations, but a stronger stimulation is needed for it; for this reason the eye perceives the outer world with the cone apparatus when the illumination is strong, and it appears in all its colors; when the illumination is weak the world is perceived with the rod apparatus and appears colorless, although light waves of various lengths are still sent into the eye. o . : : . $ Quite different results are obtained, as Treitel says, if light perception is measured in daylight by the sense of contrast in the retina. There is in this case a steady decline, as in visual acuity, in passing from the macula lutea toward the periphery. But the suspi- cion arises that in thus measuring light perception some part must always be played by visual acuity. Light perception seems then to have a certain dependence on vision, rising and falling with it. The sense of stimulation of the retina can be estimated quite independently of vision. The color sense decreases with visual acuity from the center to the periphery of the retina. This decrease is so sharp that the INDIRECT VISION AND FIELD OF VISION, 65 color of a green card 7 cm. square at 35 cm. distance is no longer recognized as green if the image falls 30° to the temporal side of the macula lutea. The statement is, therefore, often heard that the periphery of the retina is color blind; the green blind zone is the largest, beginning 30° or 20° from the fovea centralis; the red blind zone is narrower; while the smallest and nearest to the edge of the retina are the yellow and blue zones. All this is true, how- ever, only when it is taken for granted that the test object is of definite size, distance, and strength of light and color. If there is an increase in the visual angle at which the test object is seen, or if the strength of its light and color is increased, or if both conditions are present, then the color-blind zone narrows. Many observers claim that the extreme edge of the retina is sensitive to color if the stimulation is strong enough and the illuminated retinal area large enough. For the ophthalmologist’s purpose the chief question concerns the size, boundaries, and possible localized defects of the field of vision. The field of vision of an eye is that portion of space from which an eye at rest can receive impressions of light. A diagram of this portion of space may be projected upon any desired spherical surface described about the nodal point of the eye. The extent of the field of vision is modified on the one hand by the anatomical struc- ture of the bulb, on the other hand by the surroundings of the eye itself. In regard to the former point, the size of the pupil is first thought of. Investigation has shown that with a wide pupil the field of vision is somewhat (about 2°) larger than with a narrow pupil, other conditions being equal ; this is easy to understand. It is less easy to understand that the field of vision becomes larger when the surface of the iris advances, for instance, during accommodation for a near object. This advance of the iris is, however, connected with a contraction of the pupil that reduces the field of vision. Furthermore, the extent of the retina must be considered. In myopia it happens the luminous rays entering very obliquely reach the fundus, but are not perceived; in this case the border of the field of vision would not be defined by the obliquity of the ray as it enters the eye, but would depend on how far the retina extends toward the front of the bulb. Finally, it must be borne in mind that the fovea centralis does not 5 66 THE FUNCTION TESTS. lie exactly at the center of the retina but somewhat to the temporal side of it. Reckoned from the fovea centralis, the nasal side of the retina is larger than the temporal side; consequently the field of vision from the point of fixation extends more toward the temporal side than it does toward the nasal side; for, as will be explained later in detail, the temporal side of the field of vision refers to the nasal side of the retina, and vice versa. The eye’s surroundings may take up part of the field of vision. A prominent nose or a protruding arch of the temporal bone may usurp the field of vision ; indeed, deep-set eyes may be affected by the maxillary part of the socket. Such modifications may appear as limitations when the field of vision is measured, and care must therefore be exercised to avoid confusion on that score. If the glance is outward, the nose may have no influence upon the field. A droop of the upper lid will effect a noticeable reduction in the extent of it above. Measurements of the field of vision are generally made by Foerster’s perimeter ! or one of its modifications. Originally this was arranged as follows (/zg. 79): Ona standard is fixed a pillar, a, at whose upper end the lower edge of the orbit is leaned. If the right eye is to be examined, the chin is rested against an arm at the left, 0; if the left eye, on anarm at the right; this arm is adjustable, since the distance of the chin from the eye differs in different per- sons. To keep the-eye at rest the patient is told to fix a point on a level with the eye fastened at about 35 cw. distance on another pillar, ¢. This fixation point isat the same time the axis about which is turned the arc of a circle, d d, divided into degrees. This arc has a diameter of about 35 cm.,its middle point lying above the pillar, a, at the nodal point of the eye. If this arc is revolved about the horizontal axis, identical in this case with the visual line of the eye, it describes a spherical surface about the nodal point of the eye. On this arc is adjusted a movable square disk, white or col- ored, and the patient is requested to tell without moving his eye when the disk is visible and when invisible. This test is repeated at various positions of the arc, which can be read off ona scale, s, at its axis; the disk can in turn be placed at every part of the field 1 Aubert was the first to use an instrument for measuring the visual field; this was later perfected by Foerster, who called it a perimeter and introduced it into ophthalmic practice. Foerster’s perimeter has had innumerable modifications, the latest being the so-called “ self-registering,’’ which diagrams the field as it is marked out. INDIRECT VISION AND FIELD OF VISION. 67 of vision. Asa rule, however, it is sufficient to place the arc in only a few positions, say the horizontal, the perpendicular, and four to six oblique ones. The result of each trial of a new position of the arc, that is, the areas where the disk is or is not visible, is en- tered on a diagram such as is shown in Fig. 20. This diagram of the field of vision represents the spherical sur- face described by the arc of the perimeter about the nodal point of Fic. 19.—PgRIMETER. the eye. Around Fare nine circles marked so, 20, 30, to go, cor- responding to the parallels of latitude of a sphere. The middle point, /, of the diagram is the intersection of the lines marked o, 20, 40, 60, 80, to 360, corresponding to parallels of longitude. By means of circles in the one case and the diameters of circles in the other, it is possible to register any point designated on the arc of the perimeter. 68 THE FUNCTION TESTS. In Fg. 20 are shown the outlines of the normal field of vision of the right eye, no allowance being made for the nose or upper lid. As we see, the field extends go° toward the temporal side, and Fic. 20.—Normar Fietp oF Vision oF THE Rint Eye ror WuITE AND THREE Co ors. only 60° toward the nasal side; 55° upward and 70° down- ward. By combining this right visual field with a corresponding left visual field, we get such a result as is shown in Fig. 27, repre- Phystotogecal Scotomate. ZS eo; ° Fixatiqn Point Fic, 21.—CompLete FIELD oF VISION FoR THE Two EvsEs (Lue is the field for the left eye, Red for the right). senting the total field of vision for the two eyes. The Red line indicates the field for the Right eye, the bZue that for the Left eye. The total surface circumscribed by the red and blue lines is the INDIRECT VISION AND FIELD OF VISION. 69 complete field of vision ; but in each separate area is a small portion belonging to one eye alone, the right portion to the right eye, the left to the left eye. At the temporal side of the fixation point (Fig. 20), between zo and 20, a small circle is shown in the diagram. This corresponds to the place of entrance of the optic nerve; as it has no retinal elements and as the nerve fibers alone are not sensitive to light, this appears in the field as the physiological dark spot, scofoma, Mariotte’s or the dlind spot. There are other but smaller blind areas in the visual field which probably correspond to points of division in the retinal vessels. In practising measurements of the field of vision, one must struggle with the difficulty of overcoming the tendency shown by ignorant patients to look at the test disk as soon as their attention is directed to it. As this would destroy all accuracy, it is necessary to keep a constant watch over the patient’s eye, and in order to do this it is best to sit opposite the patient, so as at once to repeat any measurement in case the eye has moved at all from the fixation point. It is also difficult to give the disk an equal illumination at every position. If the patient sits with his back toward the window, sometimes the disk passes into the shadow of his head, and sometimes the light from the window falls on it, not directly, but obliquely. It must be further mentioned that the field of vision is rather larger if the disk is moved from the center to the periphery until it disappears, than if it is moved in the opposite direction. One eye must, of course, be closed while the other is being examined. By means of this method of examination we obtain diagrams of visual field that are in some diseases diagnostic. A field narrowed concentrically is a sign of one disease, a round scotoma of another, a segment scotoma of a third, and so on, as will be illustrated later. Ordinarily, the field for white is taken, but it is often of interest to discover any possible defects in the color fields; in doing this we use a red, a green, a yellow, or a blue disk at the end of the arc, and ask the patient to tell when he sees the color as it approaches the fixation point. The normal fields for color are given in Aig. 20. This diagram shows the outlines for color in Aubert’s right eye, a soft colored paper of 645g. mm. on a black 7O THE FUNCTION TESTS. ground in the daylight at 20 cm. distance from the eye being used as a test object. The color of larger test objects, as, for example, a red disk of 32 mm, square, or 1024 sg. mm. in area, or a blue one of 16 mm. square, or 256 sg. mm., would be detected at the extreme edge of the visual field. It is possible to select shades and tints of red and green disks in such a way that the red and green fields are alike; the same is true for properly selected blue and yellow fields. V. BINOCULAR VISION AND SQUINT. 1. PROJECTION OF RETINAL IMAGES. Any object in space looked at by a healthy eye forms a dioptric image at the fovea centralis of each eye. These images are per- ceived, but the cause of the perception is to be ascribed not to the Fic. 22,—PROJECTION OF THE IMAGE IN Ong Eve. place of sensation, the retina, but to the outer world, and the sen- sation of each eye is projected to the same place ; both sensations are fused so that one single image is perceived. This fact is as easy, or, if you please, as hard, to explain as is the fact that an ob- ject felt with two fingers is perceived as one. It must never be forgotten that our senses are but the raw material from which, by means of personal and inherited experience, conceptions of objects in the outer world are formed. An image is formed, however, not only of the object looked at, but also simultaneously of every other object that appears in the same field of vision. Are the retinal images of objects not looked at also fused into one? Let us examine the case of monocular vision. The point looked at, c (Fig. 22), forms its retinal image at c', the points a and J their images at a’ and J’. The projection takes place exactly in the path of the rays of direction; conse- quently, ¢’ is projected to c, a’ to a, and 0’ to 4, or in general: she PROJECTION OF RETINAL IMAGES, 71 projection of monocular vision is outward on the line connecting image and nodal point. This proposition can be demonstrated by the fol- lowing experiment: shut one eye and place a prism before the other; try now to grasp a finger or any object placed in front of it; the effort will always be made to one side, toward the left if the base of the prism is toward the right; too high if the base is below, and so forth. fig. 23 explains this condition. If the prism were not introduced into the path of the rays, the point c would be imaged as in Fig. 22 at the fovea centralis at f; but in pass- ing through the prism the rays are diverted so that the retinal image is misplaced below to ¢’. When ¢’ is connected with the nodal point 4, and this line is extended outward, c’’ results as the apparent position of the object c. Even if the eye behind the prism is revolved so as to bring the image c’ at the fovea centralis, 7, the same error would be made in outward projection, for after the movement of the eyeball, which would bring the point f to c’’, where the position of the image of ¢ is, the connecting line between the fovea centralis and the nodal point would still give the same result as in 27g. 237, c7 he’’. Fic. 23.—Fa.se PRojecTION THROUGH A Prism. In the projection of the retinal images there must also be con- sidered the impression that is formed of the position of one’s eye- ball, irrespective of the correctness or falsity of this impression. There is very plain evidence of this in some diseases of the eye muscles. If, for example, that muscle which turns the right eye toward the temple is paralyzed, and if the patient attempts to grasp an object at his right when his left eye is closed, he always goes to the side and to the right of it. In consequence of the paralysis of the external oblique the patient makes a disproportionate effort to look at an object by turning the eye toward the right, and as a result his estimation falls too far to the right of a line connecting the retinal images and the nodal point. This is obviously the case not only for the point looked at, but also for everything else within the visual field. Therefore we speak of “ false projection in the visual field.” Retinal images are projected not only in certain directions but also to definite distances. For this distance of the projected image there seems to be some feeling of measurement in that effort which 72 THE FUNCTION TESTS. must be made to adjust the eye for looking at it (that is to say, the convergence connected with accommodation in any eye). How- ever, one can very easily convince oneself that even those objects lying beyond the far point are estimated at their proper distance in monocular vision. This, of course, is possible for us only in the case of well-known objects. The church tower at home, for example, produces on the retina of the observer an image that be- comes greater as he approaches it. From the size of this retinal image the observer estimates very well the distance of the church. But ifan altogether unknown test object is selected, and if in addi- tion care is taken to exclude from the field of vision well-known objects that might serve as a comparison, then estimations of distances without the associated adjustment necessary will be inexact or impossible. We can therefore conclude that the projection of the retinal images, even of one eye, is a very complicated mental process, in which the location of the optical images on the retina, the subjective concep- tion of the eye’s position and accommodation, and finally our know- ledge of the object seen, all play an important part. Still more complicated is the case in binocular vision. Look at a distant object, say test letters hanging on the wall opposite, and place a pencil in the direction of vision: the pencil now appears double, and these false images now appear in a false position. If one eye is covered, one of the false images disappears and the other apparently jumps into the correct position. The above rule con- cerning projection in monocular vision is, therefore, not quite applicable in binocular vision, since the left eye may cause the right one to err, and vice versa. This misleading influence of the covered eye upon the uncovered one may be demonstrated even in monocu- lar vision. The examination of the conditions under which, in binocular vision, only one object is seen, has brought to light the following facts :— (t) Images of a particular object formed on both fovez centrales become fused into only one visual perception; the foveze centrales are therefore cover or “identical points of the retina.” (2) Any other object is seen as one when each of the images it forms upon the retina lies an equal number of degrees above, below, > Helmholtz, “ Physiologische Optik,’’ rst Edition, 4. 6r2. PROJECTION OF RETINAL IMAGES. 73 to the right, or to the left of its fovea centralis. That point in the right eye, then, which lies on the horizontal meridian 10° toward the right, that is, at the temporal side of the fovea centralis, is identical with a retinal point in the left eye which lies 10° horizont- ally toward the right, that is, at the nasal side of its foveacentralis. The easiest way to get an idea of these “identical points” on the retina is to imagine both eyeballs fused into one, so that the fovea centralis of one eye and the perpendicular meridian passing through it fall on the fovea centralis and the perpendicular meridian of the other eye, when all “ identical points” of the retine will lie together. In some positions of the eye it is easy to determine £ those points in space which are referred to the identical points of the two retina. When vision is directed to- ward infinity all points in space at infinity naturally become identical, since rays of direction for the rightand left eyes are parallel and in both eyes lead to points ly- ing equally distant and in the same direction from the fovee centrales. Asa mat- in ter of fact, the distance be- tween the eyes is so small aK that anything beyond SOM, Fic. 24.—Mugrrer’s Horoprer Circe. can beconsideredasinfinity. In the case, too, when the two eyes look at a point lying on the same horizontal plane but at a finite distance, it iseasy to determine the horopter. Zhe horopter ts the geometric figure drawn through all points in space which are imaged at identical points on the retine. In a horizontal plane? the horopter describes a circle which is drawn through the point of fixation, 7,and the nodal points of both eyes, X; and X,, “ Mueller’s horopter,” Fig. 24. Each point a, Ir 1 The geometrical do not correspond exactly to the physiological points, but the differ- ence is so slight that it may be neglected here. 2 In the perpendicular plane there is also a horopter, but it need not be discussed here. 74 THE FUNCTION TESTS. on this circle, a for example, forms images a, and a, at an equal number of degrees distance from the fovez centrales, /; and /,. Angle a A7 # = angle a Ky being angles of the same arc a / of the circle. Angle a A? # = angle fz A? az and angle a Ay / = angle f- Ky ar ; therefore, angle 7 A? az == angle f, Ky ar. For all other positions of the two eyes the matter is very com- plicated and has no immediate significance in this analysis. From what has been said we see that in binocular vision some objects are perceived singly, others double, but that does not as yet give us a general rule for binocular projection. The most important fact in this connection is that projection is made as if from the “double eye” which was imaged as a fusion of the two eyes into one (Fig. 25). If, in this double eye, the retinal images of an object lie at one and the same spot, the object ap- pears single; if the images lie at different spots, the object appears double. Fig. 25 illustrates this. The red or right eye and the blue or left eye fix a point, a, which is imaged on the fovea centralis of the left eye, /7, and of the right eye, f-. In fusing these eyes into the red-blue eye, /7 and /; lie together at fa; @ is seen single and projected correctly through Xz to its proper location. Meanwhile, a point, 4, within the horopter circle, 2 A? A;, is imaged in the left eye at 62, in the right at 4,, and, therefore, further from its fovea centralis. If I now pick up the arc f7 07 and carry it to the double eye (to the right of fy), and do likewise with the arc f+ 4y, I obtain in the double eye two distinct images of the point, 6. Projected through the nodal point, Av, they give the false images, 8, and #y, lying to the left and right of the true object, that is, crossed or heteronymous; in other words, the false image of the right (red) eye lies to the left, and the false image of the left (blue) eye lies to the right. Constructing the same diagram for the point, c, lying without the horopter circle, we get in the double eye the separate images, cy and cz, which are projected through the nodal point, Kg to y, and y, The false image of the right eye lies to the right, that of the left to the left; the images are on the same side of the eye, homonymous. Applying this construction (fig. 25) to ophthalmic examination, there results the rule that odjects between the fixation point and the observer appear double and heteronyinous (crossed ), those beyond the fixation point appear double and homonymous ; or in other words: in eyes converging more than is necessary for monocular fixation an object produces double and homonymous images, in eyes not converging enough or in eyes diverging an object produces double and heteronymous (crossed) images. This proposition forms the groundwork for the study of squint, PROJECTION OF RETINAL IMAGES. 75 and must be for the ophthalmologist as much a matter of memory as is for the mathematician his twice one is two. Just one word more concerning the fact that we are not continu- ally annoyed by double images of objects seen at one side, a con- fusion possible from the above explanation. We have a great abhorrence of double images. We avoid them even by turning the + re Sp Fic. 25.—ProjecTion oF Retinar Imaces. (After Martini.) eyes into an uncomfortable position. But this process is not ap- plicable to the double vision just mentioned. We therefore avoid double images by the simple act of “exclusion”’ of one or the other ofthem. This neglect isa mental process not yet quite explained, the force of which can be appreciated when we consider that many persons are unable to see even physiological double images. 76 THE FUNCTION TESTS. 2, EYE MOVEMENTS. It has just been explained that both visual lines must cross at the fixation point if it is to be seen directly and single. In order to satisfy this condition in the various locations and distances of any fixation point the eyes must be movable. Since the eye, dis- regarding the shape of the cornea, is a sphere, and since displace- ments of the whole sphere are excluded, we need consider only movements of the sphere about its middle point.1 The movements geometrically possible about every straight line passing through the middle point and considered as the axis of rotation, are only in part performed. These movements are accomplished by means of the four rectus and the two oblique muscles: the rectus exter- 50 40 SE —— 40 e rint. Tet. =T= Fic. 26.—Tue Errect or tHe Eve-Muscues. -(A/ter Hering.) nus, internus, superior, and inferior; the obliquus superior and inferior. The action of each muscle, supposing it to act by itself, can be illustrated as follows: let an eye look at a point exactly opposite on a perpendicular wall; if now one of the eye muscles contracts, the eye is moved and looks at another point; the visual line therefore describes on the wall a tracing diagrammatic of the effect of this muscle. zg. 26 shows this diagram when the rota- tion point of the eye is distant from the surface of the paper the length of the line dd. The numerals placed along these lines indi- 1Tn reality, the point of rotation is not at the center of the eye but at a point lying 1.29 mn. back of it. This is true for the emmetropic eye; in the ametropic eye the condition is somewhat different. For practical purposes we may consider the eye as a sphere and its center the point of rotation. EYE MOVEMENTS, 77 cate in degrees the angle through which the eye has moved when it looks at the point indicated by the number. The effect of the internal and of the external rectus is easy to describe, both muscles simply carrying the visual line horizontally inward or outward. It is more complicated in the case of the four other muscles. The line belonging to the superior rectus passes upward and in a gentle curve inward. The oblique mark at the end of this tracing indicates that simultaneously a rotation of the eyeball takes place about the visual line, “circular rotation,” and the position which the previously horizontal meridian assumes in consequence of this circular rotation. The effect of the inferior rectus corresponds to it; it rotates the eye strongly downward, a little inward, and causes a circular rotation in the opposite sense to that of the superior rectus. And, finally, the oblique muscles: The inferior oblique turns the eye upward, strongly outward, and rotates it in a powerful degree in the opposite direction to that of the superior rectus. The superior oblique turns the eye down- ward and outward with a rotation opposite to that of the inferior rectus. In Fig. 26 it will be observed that an absolute elevation of the visual line is not effected by the superior rectus alone, The in- ferior oblique takes part in this result, for the factors of movement outward and inward are thus neutralized, and there remains only the upward movement of the eye. In the same way an absolute depression of the visual line is effected by the combined action of the inferior rectus and the superior oblique. The effects of muscular action change essentially according to the position of the eye. In fig. 27 both eyes are in the primary position, that is, parallel, horizontal, and directed straight ahead.! Suppose the right eye turned 79° outward (to the right), the superior rectus in this new position becomes a pure elevator, its function of circular rotation is lost, and when elevating the visual line from this new position the opposing circular rotation of the in- ferior oblique is not compensated for, and the elevation is consequently not absolute but connected with circular rotation to the right, the so-called positive rotation. ‘The con- trary is seen if the right eye is turned inward (to the left); now the circular rotation of the superior rectus is increased, its power of elevation diminished; since the rotatory factor of the other elevator, the inferior oblique, is at the same time lessened, the eleva- tion of the right eye from this new position is connected with appreciable circular rota- tion to the left, the negative rotation. 1 The exact definition of primary position is somewhat different, but the above is approximately correct and exact enough for our purpose. 78 THE FUNCTION TESTS. These changes in effect, in consequence of a changed position, are of great practical importance in the case of the oblique muscles and the inferior and superior recti, since the diagnosis of paralysis of individual muscles is often possible only by the application of our knowledge of these facts. In the previous section it was shown that both eyes act as a sin- gle organ, so far as projection of retinal images is concerned. The same is true for eye movements. Ifa nervous impulse is given to elevate the left eye, the same impulse goes also to the rectus superior and inferior oblique of the right eye; or if an impulse to the inter- nal rectus causes the left eye to glance to the right, an equal impulse Fic. 27.—Tue Eye-Muscies From Apove. (dccording to Landolt; drawn by L. Schroeter.) A A’, Visual line. DD’. Axis of rotation for the superior and the inferior rectus. OO’. Axis of rotation for the oblique muscles. TT’. Axis for elevation and depression. The point of intersection of these axes is the point of rotation for the eye. goes to the external rectus of the right eye, as these two muscles effect the same purpose in the two eyes. Finally, each eye must be capable of convergence and divergence to assume the position in Fig, 25,for example. The two interni in one case, the two externi in another case, act in harmony. Through the intricate nervous mechanism of the twelve eye muscles the eyes are capable of three kinds of movements and combinations of them :— (1) Movement of the visual line in a horizontal plane— 5 rectus internus of the left eye. (a) to the right { rectus externus of the right eye. rectus externus of the left eye. (2) to the left { rectus internus of the right eye. EYE MOVEMENTS. 79 (2) Elevation and depression of the visual line— (a) elevation, both rectus superior and obliquus inferior act- -ing in common. (6) depression, both rectus inferior and obliquus superior act- ing in common, (3) Convergence and divergence— (a) convergence, both recti interni acting together. (4) divergence, both recti externi acting together. We make the most extensive use of these eye movements. Any- thing noticed to the side of us at once arouses our interest ; invol- untarily, often unwillingly, the eye is turned thither so as to bring the object opposite the fovea centralis. The rapidity and exactness of this movement is astonishing. As a rule, the head is turned at the same time, so that, as Ritzmann has estimated, a movement of 50° toward an object is composed of 30° of eye movement and 20° of head movement. The attempt to look toward an object by moving the eyes alone can by many be accomplished only after several unsuccessful efforts. The movements of convergence and divergence need particular mention. They are inseparably connected with movements of accommodation. For example, if two normal eyes look at a point ly m, away, an effort of accommodation is made in both eyes equivalent to g.0 D, and such a convergence of the eyes takes place that the visual lines cross on the fixation point, even if there is no need of this position, one eye being covered or useless, perhaps. If both eyes look straight ahead and then at a point z m. distant on the plane of the eyes and at the middle line of the body, each of the two visual lines describes an angle called by Nagel wzeter-angle (427A), which is chosen as the measure of that convergence of the visual lines. Expressed in degrees, a meter-angle shows a different value accord- ing as the distance of the eyes from each other is greater or smaller. The distance apart of the rotation points of the eyes is called the basal-line. A basal-line of 64 mm. gives to a WA the value of 7% 50’; of 54 mm. the MA is 71° 32/ 45/’.. The converging power of each eye in looking at a point is inversely proportional to the distance of this point. If the fixation point lies, for example, at % #., the converging power of the eye is 2 MA ; if it lies at 14 m., the converging power is 7 A/4, and so forth. The connection between accommodation and convergence, when binocular fusion is concerned, is quite elastic. If an emmetrope reads fine print 1% mz. off, each eye is capable of accommodation of 4.0 D and a convergence of ¢ WA. The eyes are, however, capable of seeing at 14 m. distance with both convex and concave lenses, that is, they are able to do without accommodation 80 THE FUNCTION TESTS. (with convex lenses), or of intensifying it (with concave lenses), although convergence of the visual axes (to ¢ MWA) remains un- changed. The interval within which this is possible is called relative range of accommodation, that is, the range of accommo- dation available when the eyes are ina definite position. This relative range of accommodation owes its practical importance to the fact that the eyes can, without discomfort, be adjusted much longer for distances at which the positive part of the relative range of accommodation is large in comparison to the negative part. The greatest possible increase in refractive power (measured by a concave lens) with unchanged convergence is called the positive part of the relative range of accommodation; the amount meas- ured by a convex lens is called the negative part. In case the eyes are directed to the far point, there can logically be no negative part present; in case they converge to the near point, no positive part is present. Within the near point for binocular vision accommodation is very slight, though con- vergence is still possible, but the accord between accommodation and convergence ceases. Accommodation is still possible, but it is effected only by means of a conver- gence to a point nearer than that accommodated for. vg. 28 illustrates this, showing at the same time the condition of relative range of accommodation in a normal eye. The abscissee denote degrees of convergence expressed in meter angles. The ordinates denote the power of accommodation expressed in diopters. The points of the diagonal, DD, represent the different powers of accommodation normally belonging to the different degrees of convergence given in the proper abscisse. The line pf’ f’’ represents the relative near points, the line 7 7” 7// the relative far points. The distance apart of any two points on a perpendicular plane of the curves pf’ f’’ and 7’ 7// is the relative range , of accommodation for the degree of convergence designated by the abscisse; f’ is the near point for binocular vision, 4’ the absolute near point. This is attained only with a convergence of 78 A/A, although accommodation amounts to only zo.0 D. The rela- tive range of accommodation at the absolute near point is o. Of course, the measure of the relative range of accommodation varies considerably in different persons according to the use to which they put their eyes. If accommodation can be exercised to a certain degree with un- changed convergence, then convergence can logically take place without accommodation. The extent to which convergence can be increased or decreased with unchanged accommodation is called the range of fusion, The term refers to the circumstance that movements of convergence and divergence are made in the inter- est of fusion, that is, of fusing two retinal images into one mental perception. EYE MOVEMENTS. 81 fig. 28, illustrating the relative range of accommodation, serves also to illustrate the range of fusion. Let us look, for example, at the ordinate marked 6.0 D and the line through it parallel to the abscissa; we notice that this parallel cuts the near point curve, Pp’ p’’, at p, the far point curve, +77 7/’, at x”. In other words, the abscissze belonging to the interval » 7” express in meter angles all those degrees of convergence connected with an effort at accommodation of 6.0 D; the abscissa of the point p = 2,2 MA, that of the point r’ = 10 MA; the range of fusion for an accommodation of 6.0 D is, there- fore, 10. — 2,2 = 7.8 MA, the negative interval being 6.0 — 2.2 = 3.8 MA, and the positive interval being 1o—6=4 MA. The correctness of this can be proved by experiment. A man with normal vision can, in this case, still accomplish binocular fusion even if he looks through aprism. On account of the deflec- Fic. 28.—ReLation BerweEw ACCOMMODATION AND CONVERGENCE. (After Donders.) tion given to the rays by a prism, one eye must turn behind the prism in order to image on its fovea centralis the object looked at by the other eye. This turning behind the prism is the same as an increase in convergence in case the prism is placed with base toward the temple, the so-called “ position of adduction,’ or it is a decrease of convergence when the base is toward the nose, the so-called “‘ posttion of abduction.” The close connection be- tween relative range of accommodation ‘and relative range of fusion finds also a practical expression in the fact that one’s eyes can be continuously used without discomfort only for such distances as 6 82 THE FUNCTION TESTS. leave quite an appreciable interval in which to apply the relative range of fusion. We can speak also of an absolute range of fusion indicating the absolute play of convergence without reference to any condition of accommodation. This, too, has a negative and a positive interval. The negative interval, that is, the possible divergence, is measured by the strongest prism in the position of abduction through which a person with normal vision can still, when looking at infinity, accomplish binocular fusion; on the average this is a prism of 5°, corresponding to a real divergence of 2.5° in the visual lines. The positive part of the absolute range of fusion is decidedly greater ; Fic. 29.—Fretp oF Excursion. (According to Helmholtz.) (bLue for the Left eye, Red for the Aight eye.) in the case represented in Fig. 28, for example, this was equal to 78 MA or 33° of adduction for each of the two eyes (when I meter-angle = 7°.50’). The absolute range of fusion is distin- guished from the absolute range of accommodation by the fact that it is not influenced by age. The impulse to binocular fusion is so strong that even prisms with their bases above or below can be overcome through a com- pensating movement of the eyes downward or upward, but the fusion interval in this direction is a very restricted one and has no practical significance. The territory that we can cover by eye movements alone with- out moving the head is called the field of excursion. According STRABISMUS. 83 to Helmholtz, this excursional field of the eye extends upward and downward 45°, to the right and left 50°. Aubert and Foer- ster obtain somewhat different results, namely: upward 30°, down- ward 57°, inward gg°, outward 38°. The personal differences within physiological limits are obviously considerable and to a great part dependent upon exercise. fig. 29 gives an idea of the extent of this visual excursion for the two eyes, supposing them to be at the distance ac from the surface of the paper; the drawing and distance are therefore reduced in the same degree. The surface bounded by the blue line, ZZ, contains all points looked at by the left eye; the surface bounded by the red line, RR, all points looked at by the right eye. The area covered by both surfaces, ZZ and RR, represents the excursion of binocular vision; the two colored surfaces indicate the lapses caused by the prominence of the nose. 3. STRABISMUS (SguinT). In normal binocular vision the visual axes intersect at the fixa- tion point. It sometimes happens, however, that only one eye fixes while the visual axis of the other misses the fixation point. This condition is called strabismus (squint). The angle made by the squinting or deflected axis with the line it would assume in normal vision is called the angle of squint. Ordinarily the angle of squint is described as the angle between the actual position of the visual line and what ought to be the normal line in that particular case. By visual line is understood the line connecting the rotation point, D, and the fixation point, fF (the # in Fig. 30 is supposed to lie at infinity to the right). The visual line and the visual axis can, moreover, be considered as identical without appreciable error. In what follows, therefore, we shall cease to use the term visual line, for the determination of which a point in the outer world is needed, and confine our attention to the visual axis, which can always be determined by two points in the eye, the nodal point, A, and the fovea centralis, /. The visual axis is the physiological axis of the eye. It does not coincide, as might be expected, with the anatomical or symmetrical axis, but lies more or less to one side of it. It is a rule that the physiological axis cuts the cornea at a point lying to the nasal side of the center of the cornea. The matter is still more complicated by the fact that the sym- metrical axis of the eye does not exactly coincide with the symmetrical axis of the cornea, that is, with the longest diameter of the corneal ellipsoid. This last cuts the cornea somewhat more to the temporal side than the symmetrical axis of the eye (see Fg. 30). To this circumstance is to be ascribed the fact that an angle, a (alpha), is distinguished from an angle, y (gamma). By alpha, u, is understood the angle between the physiolog- 84 THE FUNCTION TESTS. ical-axis of the eye and the long axis of the corneal ellipsoid. This definition has Jost somewhat in market price, since it is now known that the cornea is by no means in every case curved as an ellipsoid. By gamma, 7, is understood the angle between the visual line and the symmetrical axis of the eye. Since the visual line and the visual axis are parallel to each other (if the fixation point lies at a distance), and since the deviation of the long axis of the corneal ellipsoid from the symmetrical axis of the eye may amount to several angular minutes, it is therefore quite permissible for all practical purposes to consider angle a and angle y as indentical, that is, as the angle between the physiological and the anatomical axes. On the average this angle amounts to 5°, but can be larger or smaller, or even nega- tive, that is, the physiological axis may, in an exceptional case, cut the cornea at the tem- poral side of its center. In emmetropia angle a (or angle y) on the average = 5°, in hyperopia = 6.5°, in myopia = 2° to 2.75°. Symmetrical Arts ut lekye — Creatas ALLS of Weed E Ltpasy | Terporabl Side Fic. 30. In order to give a better perception, the angles, a and y, are drawn much larger than is really necessary. The task of the examining physician is now a threefold one :— (1) To prove the presence of squint ; (2) To demonstrate on what the squint depends, that is, what muscle is at fault and what is the diseased condition underlying it; (3) To measure the extent of the squint (the angle of squint). The first problem will often be solved by the patient himself or his relatives, if the squint is at all remarkable. The patient comes to the physician because his environment seems to him distorted. The laity generally distinguish two kinds, inward and outward squint, strabismus convergens and strabismus divergens. There are, however, numerous cases in which the squint is not demonstrable without particular investigation, either because the angle of squint is very small or because the squint is ordinarily suppressed for the sake of binocular vision. This last is called J/atent squint, to distinguish it from manifest squint. If the physician wishes to find out whether he has a case of squint, he proceeds as follows: The STRABISMUS. 85 physician, standing opposite, holds a finger in front of the patient and asks him to look at the end of it. If the patient does not squint, the visual axes of both eyes intersect at the finger in front of him, even if one eye is covered, the nervous association of ac- commodation and convergence providing for this (p. 79). If one eye and then the other be covered in turn, no movement is visi- ble, since the covered eye is always properly adjusted. It is quite different in squint. At the request to look at the finger in front of him, the patient does so with only one eye. If now the fix- ing eye is suddenly covered, then the other—the deviating eye— makes a movement in order to bring an image of the finger on the fovea centralis. This movement of adjustment proves the presence of squint. Suppose the patient to be looking at the finger with both eyes open; if the physician now covers the left eye and notices that the right does not change its position, he concludes that the right eye was properly adjusted. The physician now covers the right eye and uncovers the left, and notices that the left eye makes a downward movement of adjustment; this proves that the left eye had deviated upward—that there was present in the left eye an upward squint (Strabismus sursum vergens). An upward movement of adjustment would have indicated a downward deviation of the left eye, a downward squint (Strabismus deorsum vergens). A downward movement is, however, impossible unless the infe- rior rectus of the other (the right) eye contracts at the same time with equal force; that is, the right eye covered by the hand turns downward, and consequently itself assumes the position of squint with reference to the finger in front of it, the so-called secondary deviation. If the left eye is now covered and the right uncovered, the latter overcomes the secondary deviation by another movement of adjustment upward. This method of investigation supposes the squinting eye to have sufficient acuity of vision to be able to fix the finger in front of it. If such is not the case, a small deviation of the visual axis is of no practical value, and a large deviation is apparent without the test just described. The second problem, the investigation of the muscle at fault, must take into consideration the fact that squint can be caused, on the one hand, by a weak or a paralyzed muscle, and, on the other hand, by an over-powerful muscle. (a) Strabismus paralyticus. Let us consider the first of the 86 THE FUNCTION TESTS. above conditions. Suppose a muscle, for example the internal rectus of the left eye, to be paralyzed; then both eyes in looking straight ahead into space will probably have a correct position ; but as soon as the patient looks to the right or attempts conver- gence, the left eye remains at a standstill and the right eye alone obeys the impulse from the brain; there results an absolute or a relative divergence of the visual axes. This squint, dependent on inaction of a muscle or group of muscles, is called the squint of paralysis, Strabismus paralyticus. From what is said above, we gather that when we suspect a squint from paralysis we must test the extent of movement in each eye separately. The test is a con- tinuation of the finger-test just described. The physician tells the patient to follow the finger with his eye when he moves it horizontally toward the right and left. Under normal circum- stances the eye should be able to follow the finger toward the tem- poral side until the external edge of the cornea reaches the exter- nal angle of the palpebral fissure, or toward the nose until the inter- nal edge of the cornea dips under the lacrimal caruncle. If this is not possible, we assume that paralytic squint is present, especially if the examination of the other eye shows no lack of muscular activity ; that is, we can be sure that the limited excursion of the one eye is not merely an apparent one dependent possibly upon an unusual size of the palpebral fissure. If one internal or external rectus is found to be paralyzed the examination can end here; for to measure the angle of squint is in this case of no service, because it is inconstant in paralytic squint. Squint is not present at all in that territory for which the paralyzed muscle is not called into play, and increases in proportion as the eye endeavors to look toward the side of the paralyzed muscle. This is also true for the secondary deviation of the sound eye. It is greater the more the unsound eye exhausts itself in the effort to fix a point lying within the territory of the paralyzed muscle; it is altogether lacking if the unsound eye can fix a point without call- ing into play this paralyzed muscle. The simplicity of the demonstration of a paralysis of a rectus in- ternus or externus is due to the fact that a movement to the right and left is essentially dependent on these muscles alone. In eleva- tion or depression of vision the relations are otherwise, as we know. Since elevation of the visual axis is carried out by means of the superior rectus and inferior oblique, inaction of one of these mus- STRABISMUS. 87 cles renders only absolute elevation impossible. In case the superior rectus of the left eye is paralyzed and that eye tries to look upward, it will appear to lag behind the other and at the same time will show a noticeable circular rotation. This kind of circular rotation should indicate, theoretically at least, which of the two muscles still func- tionates, but since the circular rotation is not pronounced, and consequently is not very easy to detect in a moving eye, some more sensitive test must be applied; fortunately, we have this in the “ double image test.” If the rule given on /. 74 is inverted and generalized, we obtain the following important deduction that che po- sition of the two eyes can be determined from the position of the double images.” The presence of homonymous double images proves that the visual axes converge to a point lying nearer than the object which appears double; and the presence of heteronymous (crossed) double images proves that the visual axes converge to a point lying beyond the object which appears double, this point being toward infinity either in the positive sense, in front of the eye, or in the negative sense, behind it. If the image of the right eye is lower than that of the left, the right eye must be directed upward, and so forth. A circular rotation of the eye will be betrayed by an oblique position of one of the two double images. In this method of testing much depends on bringing a patient to a clear perception of the double images, usually an easy matter in the case of paralytic squint. This form generally attacks adults who have been accustomed for years to perceive the retinal images of both eyes, and who are therefore not able at once to neglect the image of one eye. The test is made by showing the patient, in rather neutral surroundings say, a dark room, a bright object (a candle is one of the best), held at a distance of 2 or 3 m." To ascertain at once to which eye each image belongs, it is a good plan to place a red glass in front of the eye with the better vision ; this eye sees, therefore, a darker red flame, the other sees a lighter yellow flame, and the difference in acuteness of vision is thus more easily compensated for. If the double images are homonymous, the eyes converge, as has been said. This convergence may depend on paralysis of the right externus as well as on paralysis of the left externus. Which 1 If the double images are very wide apart it is of advantage to bring the candle to about x m. If they are near together, the reverse is true, and the test should be made at gto 6m. 88 THE FUNCTION TESTS. of the two is paralyzed is shown when the candle is moved hori- zontally from right to left, or from left to right. If the candle is moved into the field reached only by the paralyzed muscle, the double images flit apart; if in the other direction, they flit together; but if they remain the same distance apart, the squint is not due to paralysis. If one of the double images stands obliquely to the other and perpendicular one, we know— (1) That the oblique image belongs to the paralyzed eye ;* (2) That a superior or inferior rectus or a superior or inferior oblique must be at fault,? for only these four muscles are con- cerned in circular rotation. There are other signs which distinguish a sound from an un- sound eye. If the candle is moved in the direction of the para- lyzed muscle, one of the double images appears to flit away from the other, the flitting image belonging to the unsound eye. The explanation is plain if we consider that when the candle is moved, its image in the sound and, as we assume, fixing eye always falls upon the fovea centralis, while the image in the unsound eye, either totally or in part unable to continue its fixation, passes across the retina. This test can be a deceptive one, either because the patient does not observe carefully enough to tell which of the double images appears to move, or because he is accustomed to fix with the paralyzed eye. In this case we must make use of the position of the double images to find out which eye is unsound, since that is the unsound eye in which the image is nearest to the edge of the visual field,—that is, the furthest left, if the left half of the field is tested ; the furthest upward, if the glance is directed up- ward, etc. Let us take an example: Suppose a muscle on the left side is paralyzed, the externus of the left eye; then in looking to- ward the left there must be convergence, homonymous images, and the image of the left (the unsound) eye must be the further toward the left. Suppose the right internus is paralyzed; then in looking toward the left there must be divergence and heteronymous images; in this case also the image further to the left belongs to the unsound eye, this time the right one. 1 Exceptions are not unusual and will be explained later. 2 There are exceptions here also. If the patient looks obliquely, ¢. g., upward to the right, or downward to the left, etc., there is a moderate obliquity, even if only an exter- nus or an internus is paralyzed. STRABISMUS. 89 (4) Strabismus concomitans. It has been said that squint may be due to the action of a too strong or of a too weak muscle. In cases of this kind the visual field of the squinting eye is not re- duced but remains unchanged or displaced. For example, in inward squint due to a too strong internus, the eye cannot be turned so far outward as it would be normally, but the adductive power of this eye is increased by a certain amount, so that the total area covered appears about normal horizontally. Squint with normal or only displaced field is called concomitant or muscular, Strabis- mus concomitans. If the first test (~. 8g) proves that squint is present, and if the double image test ( . 88) proves that it is not due to paralysis, we can be sure that the squint is muscular or concomitant. To decide whether this is manifest or latent squint, we proceed as fol- lows: The patient must fix the finger in front of him; now cover one eye. If the open eye is quiet while the covered eye makes a movement that is corrected as soon as it is again uncovered, there is obviously a latent squint, for if the movement of correction is made by the covered eye when the fixation point remains un- changed, the conclusion must be drawn that the eye squints when covered, in order to restore muscular equilibrium ; when it is uncov- ered, however, it returns to the usual position for the sake of restor- ing single vision in the two eyes. It is worthy of note that many patients of this class do not perceive the double images, although they should appear at the instant the movement of correction is effected. Since muscular squint is treated by operation, it is important to solve the third problem, that is, to measure the degree of squint. There are two methods used. One attempts to find a linear meas- ure of the deviation and is applicable to manifest squint; the other measures by neutralizing prisms and is preferably applied to latent squint. The linear measure is taken as follows: Suppose the case is of muscular, manifest, inward squint; let the patient fix the finger with the right eye; while the fixation is quietly maintained, make an ink mark on the under lid of the left eye exactly below the external edge of the cornea. Now cover the right eye; then the left eye, which has hitherto deviated inward, makes a movement of correction outward, and as it continues to look at the finger, held, of course, in the same place, make a second mark on the lower lid go THE FUNCTION TESTS. also exactly under the external edge of the cornea. The distance of these two points from each other measures the amount of squint present; we call a squint, therefore, one of 3 or of 6 mm., etc. This measurement can also in the same way be applied to the other non-squinting eye; in doing this we measure the secondary deviation of the sound eye, which in muscular squint is just as great asin the primary deviation of the squinting eye. A somewhat purer and more accurate result can be obtained by measuring the squint with the Laurence strabometer, /zg. 37. This is held under the squinting eye, and the line in the millimeter scale lying exactly below the external corneal edge is noticed; then the squinting eye is made to fix, thus inducing the external edge to lie above another line in the scale; the distance between these two lines can then be read off and indicates in milli- meters the degree of squint. A third method of measurement is that of Hirschberg. At about 35 cm. hold a candle exactly in front of the patient’s face, and while looking over the flame observe its reflections on the two cornez. If the patient fixes with both eyes, an image of the flame is seen in each eye at the middle of the cornea, but if one eye devi- ates inward, the image in this eye lies outward from the middle of the cornea; if the image lies at the edge of the cornea, there is a squint of 6 s2., for half the width of the cornea is just 6 m2. Fic. 31.— STRABOMETER. It must be understood that all these methods give only approximate results, though they are sufficiently accurate for all practical purposes. ‘lo obtain greater exactness the angle of squint must itself be measured. For this purpose we need a perimeter, and the corneal image of the candle flame just mentioned. The squinting, that is, the left, eye is placed at the middle point of the perimetric arc, while the sound eye looks straight ahead at infinity. If no squint were present, the left eye would look exactly at the fixation point on the perimetric arc; but if there isa squint, we can, by advancing the flame along the arc until it is reflected exactly at the center of the cornea, find out that point of the circle toward which the eye is directed on account of its squint. The position of the flame is read off on the perimetric arc and gives immediately the angle of squint. In this method, as well as in that of Hirschberg, it is assumed that the visual axis passes exactly through the center of the cornea. This is not the case (see Avg. 30, p. 84). In both methods there is, therefore, a radical error which can occasionally exert a disturbing influ- ence. Measurements made with the strabometer are free from this error. In order to understand the method of measuring squint with neutralizing prisms, we must call to mind certain physical facts. In STRABISMUS. gli a prism the angle opposite the base is called the refracting angle (4 in ig. 32). Its size determines the amount of deviation experienced by luminous rays in passing through a prism when the angle of entrance of the rays and the refractive index of the glass are given. For prisms of ordinary glass with a small refracting angle (2) the angle of deviation equals half the angle of refraction (@= % 2), assuming that the rays fall perpendicularly upon the side of the prism, Let us suppose that the left eye (Z, Fig. 33) is looking straight ahead at a fixation point at infinity, and that the right eye deviates inward. The object fixed by the left eye will be imaged in the right eye to the inner side of the fovea centralis, f,, say at a, Fic. 32.—DeviaTIon oF Luminous Fic. 33.—NEUTRALIZING THE SQUINT BY Rays THROUGH A Prism. MEANS OF A Prism. and in the double eye (fig. 25, p. 75) will be displaced toward the right. If now a suitable prism is placed with the edge inward in front of the right eye, then the luminous rays will be refracted to- ward the right, and will form an image at the fovea centralis, f. Consequently the eyes, in spite of the squint, will see this distant object as asingle image. But, as can be seen in /zg. 33, the most suitable prism is the one in which the angle of deviation is equal to the angle a K, f,, obviously the angle of squint. We conclude, there- fore, that within certain limits the position of squint is neutralized by a prism with a refracting angle double the squint angle. The measure is taken as follows: After the diagnosis has shown g2 THE FUNCTION TESTS. the presence of a muscular, latent squint, either upward, down- ward, outward, or inward, the physician places in front of one of the eyes prisms of increasing strength, the apex toward the direc- tion of the deviation (Fig. 33). That prism with which the two eyes obtain normal vision, that is, the prism in looking through which there is no deviation when the eye is covered and no move- ment of correction when the eye is uncovered, is the neutralizing prism, and as such is a measure of the squint. This method is called A. Graefe’s equilibrium test. There is another equilibrium test introduced by Graefe the elder, the v. Graefe’s equi- librium test. It is made as follows: A strong prism apex upward or downward is used to overcome single binocular vision. The person to be tested, since he cannot overcome such a strong prism in this position, sees double, and the double images stand one exactly above the other, if muscular equilibrium is maintained; if it is not maintained, the eyes will now assume either a convergent or a divergent position, since there is no necessity for a proper convergence to the fixation point. Consequently the double images are seen displaced not only perpendicularly but also horizontally. The amount of horizontal dis- placement can now be measured by a second prism. For this purpose prisms of increas- ing strength are held before one eye, with the apex toward the temple if the images are heteronymous (crossed) and toward the nose if homonymous, until the patient says that the images are again perpendicular one above the other. The prism giving this result measures the amount of horizontal displacement. This test is not always trustworthy, because in many persons the displacement of the false images in a deviating eye is a very uncertain quantity. [American ophthalmologists, led by Dr. Stevens, of New York, have developed and perfected the old v. Graefe equilibrium test, not so much for the purpose of detecting latent or dynamic squint, as in the hope of demonstrating some weakness in muscle balance which could cause many of the symptoms, like headache, eye- strain, and exhaustion, classed under the term “ muscular asthenopia,” in contradistinction to the analogous symptoms due to accommoda- tive asthenopia. The test is conducted by prisms, the same prin- ciple applying here as in the method explained above. The nomenclature also has been elaborated by American oph- thalmologists, but is devised to illustrate the direction in which the visual lines tend, rather than the simple effect of the muscles themselves. It is assumed that in a normal person the visual lines of the two eyes are parallel, and that binocular single vision (fusion) results, when fixation takes place for objects at and beyond 6 zz. ; this condition is called orthophoria. Now, in certain states of the physical system,—bad health, irregularity of the orbit or of the in- sertion of a muscle, or when there is a refractive error,—this paral- STRABISMUS. 93 lelism may be lost, and one visual line will then be in a different relation to the other ; this general deviation is called heterophoria. A tendency of one visual line outward is called exophoria ; inward, esophoria ; upward, hyperphoria. (Hypophoria is not used, for, al- though theoretically probable, the alternate position of the other eye, hyperphoria, is always treated.) Before testing, all refractive errors should be corrected; atropin may or may not be used. Elaborate apparatus has been devised by Stevens and others, but the prisms furnished in a good case of lenses suffice for establish- ing a diagnosis. The patient is placed as for the examination of the visual acuity, but instead of letters a light (candle) at 6 m. is used, which is to be fixed by the patient. I tis best to place a red disk before the right eye (unless this be very amblyopic), since the contrast aids the patient in making accurate statements. Now place before the left eye a prism of 5° to zro°, base downward. The eye is rarely able to overcome a vertical prism, and all effort at fusion being thus destroyed, the result is diplopia, the two images of the candle-flame not lying in the same horizontal plane in any case, and lying in the same vertical plane only when parallelism of the visual lines is maintained—orthophoria. The red image is correctly projected and belongs to the right eye. Suppose the other image lies above and to the side of the red image. Applying the rule of projection on . 74, it is evident that if the white and upper image (left eye) lies to the right of the red image (heteronymous diplopia), the visual lines must tend away from each other—exo- phoria—and the condition is weakness of adduction in the interni. If the white image lies to the left of the red image (homonymous diplopia), the visual lines must tend toward each other—esophoria— and the condition is weakness of abduction in the externi. Now place prisms of varying strengths in front of the right eye, base in (abducting) for exophoria, base out (adducting) for esophoria, until just that prism is found which causes the two images to lie exactly in the same vertical plane; parallelism of the visual lines is re- stored, and the prism effecting this is said to measure the muscular inefficiency.’ 1 The expression “ to measure” is incorrect, since there is no constant loss of muscle equilibrium. The action of muscles is always relative and inconstant, and the test shows only the tendency of the equilibrium to be lacking or excessive by so many degrees. 94 THE FUNCTION TESTS. The simplest test for hyperphoria is with the Maddox rod, which consists of a small glass cylinder in an opaque disk, made to fit a trial frame. (A very neat Maddox rod is now made of red glass, the cylindrical portion being cut out of the glass; the disk thus combines in one both red glass and rod.) This disk is placed in the trial frame, and if the rod is horizontal, the candle-flame will be changed into a vertical beam of light; if the rod is vertical, the beam of light will be horizontal. Suppose the rod is placed verti- cal; there are now two lights, the beam belonging to one eye, the natural light to the other. Ifthe beam passes directly through the center of the flame (or if the flame lies at the center of the beam), there is no upward or downward deviation. If the two lights are not in the same horizontal plane, there is hyperphoria, the lower light belonging, of course, to the eye which has the greater ten- dency to deviate upward. By placing the rod horizontal, the verti- cal beam may discover exophoria or esophoria, but the absence of signs therefore does not imply orthophoria, since a latent tendency to deviation may have been so overcome in the interest of fusion that the beam passes through the flame. The term hypereso- phoria—tendency upward and inward—expresses the condition of homonymous diplopia with the two images in different horizontal planes. Hyperexophoria expresses the condition of heteronymous diplopia with the images in different horizontal planes. All these preceding deviations are assumed to depend upon lack of equilibrium between the recti muscles. A similar disparity be- tween the obliqui may be unmasked, as some ophthalmologists claim, by Savage’s test, in which a double prism of several degrees each is used, mounted with bases together, in a trial-frame disk. This is held with axes vertical before one eye, while the other eye is covered. The object of fixation is a horizontal line 50 cm. The line is distorted so as to appear as two parallel lines. When the other eye is uncovered, it should see between these two a third line parallel to them. Any loss of balance between the oblique muscles is said to be indicated if this third line is not parallel. Suppose the double prism to be before the right eye; there is left hyperphoria if the middle line is nearer the bottom; there is exophoria if it is more to the right and less to the left; there is esophoria if it is more to the left and less to the right. There is said to be insufficiency of the left superior oblique if the right ends of the middle and lower lines converge; insufficiency of STRABISMUS. 95 the left inferior oblique, if they diverge. By changing the double prism the right eye may be similarly tested. As the last trial is conducted at a distance of 50 cwz., it is well to repeat the preceding prism tests for equilibrium, at the same (near) distance, using instead of the candle a small white cross on a black ground. The results thus found may or may not coincide with those found at 6 m. These examinations should be supplemented by testing in each eye the strength of the prism that can be over- come by adduction (base out), and by abduction (base in), before double vision occurs. Muscular power varies, of course, in different eyes and on different occasions, but adduction will be from 25° to 50°; abduction from 5° to zo°.—H.] B. OBJECTIVE METHODS OF INVESTIGATION. I, REFLECTION FROM THE CORNEA.— KERATOSCOPY. The surface of the cornea, being a separating surface between two transparent media, air and cornea, is a mirror, and on account of its curve a convex mirror that reflects virtual images of lumi- nous objects; these images are upright, diminished, and lie appa- rently behind the cornea; they are commonly but improperly called reflexes. The size of such a reflection (mirror image) depends upon the size of the object, its distance, and upon the cur- vature of the corneal surface. The further off the object and the smaller the radius of the cornea, the smaller is the image. The shape of this image depends upon whether or not the corneal sur- face is spherical; if it is so, then the image is geometrically identical ; if the cornea is astigmatic, that is, asymmetrically curved in any meridian, the image is regularly distorted. Finally, the sharpness and clearness of the image is proportional to the smoothness of the cornea, and is affected by any depressions or elevations in it. In case there are any holes, fissures, or vesicles, the image is irregularly distorted and dim. We can, therefore, on the one hand, recognize by means of these corneal reflections any small roughness, excavation, or prominence, and, on the other, estimate from the size, length, and breadth of the image the varia- tions in radii. ; To study any roughness or unevenness in the corneal surface, the physician turns his back to the window and places the patient in front of him; he then sees the reduced image of the window and window bars reflected from the patient’s cornea. The patient is now asked to look at a finger held in front of him; by moving the finger in various directions the eye is brought into various posi- tions so that gradually the physician has seen the image of the window reflected from every portion of the corneal surface. In this way the whole cornea is tested, and as any roughness would be apparent to the finger, in the same way an unevenness of the corneal surface is betrayed by an irregularity in the reflected 96 REFLECTION FROM THE CORNEA. 97 image, and the smallest loss or unevenness of the epithelium can be recognized without difficulty. The second step, finding the corneal curvature, is carried out by means of various instruments and for various purposes. In prac- tice it is seldom of value to determine the actual dimension of the radius of curvature; but, on the other hand, it is doubly important to know whether and in what degree the cornea is meridionally asymmetric. For this purpose the keratoscope was devised, that of Wecker-Masselon being perhaps the most used (Fig. 34). It con- sists of a blackboard z& cm. square, bordered by a white stripe about 75 mm. broad. There isa hole in the center to look through. It is held by a handle about which the board turns at its middle and in its own plane, the amount of this rotation being read from Tg eae Masses) ao kee a scale on the back of the board. The instrument is held about 20 cm. in front of the eye. If the cornea is normal the reflected image of the white frame is a square, measuring on each side not quite + of the corneal diameter, but if the cornea is meridjonally asymmetrical the image of the frame loses its square shape; if the sides of the square frame are not parallel to the principal meri- dians of the cornea, the image is a rhomboid. By turning the board on its handle the white frame will finally take a position from which a rectangular image is reflected. When this position is found we have the direction of the principal meridians. The instrument is handled as follows: The physician sits oppo- site the patient and adjusts the keratoscope so that the white square, illuminated from a window or a lamp, is imaged on the 7 98 OBJECTIVE METHODS OF INVESTIGATION. cornea. The physician looks with one eye through the hole in the keratoscope at the eye of the patient, who is requested to look at the hole from his side of the instrument. If the image is rectan- gular it is compared with a series of ten rectangles printed on an accompanying card (fig. 35) that illustrates the corneal images in astigmatic condition from o to zo.0 Diopters. The rectangle (the first one being a square) showing the closest resemblance to the corneal image may be taken as a measure of the corneal astigmatism present. This Wecker-Masselon keratoscope can be had in a perfected form. If a square is reflected from an astigmatic cornea as a rectangle, then there must be some rectangle the image of which on this cornea will appear as a square. The square of the white frame may be changed by means of a screw adjustment into a parallelogram. This screw is turned until the image which first appears as 9 parallelogram is now reflected as a square, the change effected in the frame being the measure of the astigmatism present. In order to read in diopters without farther trouble the astigmatism thus found, the frame is arranged with an empirical scale and an indicator connected with the screw. In many scientific problems it is of interest to determine the actual size of the cornea, that is, the radius of its curvature. This can be done by applying the following rule: If the distance of an object from a convex mirror is equal to infinity, the image lies at the (virtual) focus, that is, at one-half the radius (1% 7) behind the reflecting surface. When the corneal curve is sharp, objects at a few meters distance are images close to the focus, and the radius of the cornea may therefore be estimated by a simple proportion :— If a, the size of the object, 6, its distance from the cornea, and c, the size of the image, have been measured, we then have this ratio: a:c= 3d: = 3 consequently 7 = 2 = It is easy to measure a and 4, while « can be measured by the Helmholtz or the more modern Javal-Schiotz ophthalmometer. This instrument and its use is explained in text-books of physiology or in exhaustive works on ophthalmology. Many ophthalmologists use the ophthalmometer for purely practical purposes, especi- ally for determining objectively the presence of astigmatism. I prefer to use the Shadow Test, 9. v. II. FOCAL OR OBLIQUE ILLUMINATION. If two completely transparent media touch each other, a reflec- tion of luminous rays occurs only at the surface of separation. But in case one of these media is not completely transparent, part of the rays will be reflected from within the medium itself, and the reflected rays will therefore be visible. For that reason corneal scars, on account of their opaqueness, appear as gray blotches. In many cases, however, there is so little light reflected that the lack of FOCAL OR OBLIQUE ILLUMINATION. 99 transparency cannot be detected unless special methods are used. The method most suitable for these cases is a strong oblique illumi- nation. By means of a lamp anda convex lens a very powerful light can be thrown upon the suspected area, and there are enough of the diffused rays returned to the observer to show him a gray spot which would be invisible with a weaker illumination. As the examination takes place in a dark room no other light falls upon the cornea except that from the lamp through the convex lens; there is, therefore, a strongly illuminated area on the cornea sur- rounded by an area of weaker illumination, this contrast favoring the recognition of any places from which the reflection is weak. And, finally, one’s own eye can be aided by magnifying glasses, convex lenses of short focal distance being used for this purpose. The most desired magnification with a large field is obtained, how- ever, only by lenses of special construction. The Hartnack spheri- cal lens seems to me particularly commendable; it is small, handy, cheap, has a refractive strength of about 35 Diopters, and magni- fies objects three to four dimensions. More complete still, although dearer and less easy to handle, is the Zehender-Westien binocular lens, which magnifies objects ten- fold and at the same time gives us stereoscopic vision. Aubert’s binocular lens does the same thing. To make this examination with oblique illumination we need a moderately dark room and such a source of light as is ordinarily furnished by a lamp or an adjustable gas bracket. The patient sits at 1% m. from the lamp, which is in front of him and a little to the left. The physician sits or stands in front of the patient and at his right. With one finger of his left hand he raises the upper lid of the eye under examination, holding the lens between his index finger and thumb. With the right hand he holds a convex lens of about 20 Diopters so as to throw an inverted reduced image of the flame exactly upon the surface of the cornea, bringing it, therefore, at the focus of the lens—hence the name, “focal wlumination.” 1 If the lens is approached to the eye the apex of the cone of rays falls upon different layers of the cornea. If the lens is moved up- ward, downward, to the right or to the left, any desired spot on the surface of the cornea can be illuminated focally. When the condition ” 1 This is not exactly the proper term, for ‘ focus” really means the focal point of an object lying on the axis at infinity. 100 OBJECTIVE METHODS OF INVESTIGATION. of the cornea in all its parts has been investigated, the lens can be approached still closer to the eye in order to throw light into the aqueous, upon the iris, into the lens, and, if the pupil is wide enough, even into the vitreous. Many diseased changes of the cornea stand out clearly by mediate illumination. For example, corneal blood-vessels lying in a faintly clouded cornea can be seen best if the iris behind these spots is illuminated. The luminous rays are thus reflected from the iris and penetrate the cornea from behind forward. In such manner small cell masses on the posterior surface of the cornea can be dis- covered, the so-called deposits on Descemet’s membrane. If these are illuminated directly, their appearance will be obscured by the light thrown back from the corneal surface and from what cloudy areas there may be within the cornea; but they are seen with ex- traordinary clearness when illuminated from behind in the method just described. In making use of oblique illumination we see certain phenomena of light in their physiological relations. These are, in part, images reflected from the three refracting surfaces of the eye, the cornea, anterior and posterior lens surfaces ; and, in part, light diffusely reflected from the corneaand lens. The difference between these depends upon the fact that an area reflecting diffused light sends luminous rays in all directions, and they are thus visible to the observer irrespective of his relative position; while a mirror image sends out a definite cone of rays and is constantly visible to an observer only when his eye lies within its path. Another difference is this: Any part of the cornea or Jens reflecting diffused light appears a delicate gray, or in some diseased conditions even white ; while a mirror image, particularly that of the cornea, is quite bright—the very image of the yellow flame itself is seen. Whether the observer sees the images or is attracted more by the areas reflecting diffused light, depends somewhat upon the distance of the convex lens from the eye under examination. If, for example, the convex lens is so held that the image of the flame is focused in the air nearly in front of the cornea, no diffuse reflection is seen, but the images from the three refracting surfaces, the so-called Purkinje-Sanson images, appear more distinctly than in any other method of physiological demonstration. Oblique illumination is therefore undoubtedly the best method of demon- strating these three mirror images. If the convex lens is approached closer to the eye, the small and distinct mirror image from the posterior lens surface is changed to an indistinct yellow reflection, particularly apparent in the eyes of old persons, and called in many text-books, improperly, as I take it, “‘ nuclear-reflex.”? This reflection is not from the lens nucleus, but from the posterior lens surface, and the yellow color is due to the amber-like appearance of the senile nucleus. If the convex lens is held so close to the eye that the image of the flame falls in or behind the crystalline lens, one sees a gray phosphorescent streak of light in the depth of the pupil. This streakiness, as well as Purkinje-Sanson images, may be used to prove the presence of the lens. The cause of this streakiness has been explained as being due not only to the stratified structure of the lens, but also to the fact that the lens of itself is not absolutely transparent. THEORY. IOI Ill. THE OPHTHALMOSCOPE. 1. THEORY. The cornea and aqueous being transparent, it is easy to see the iris lying behind them. The lens and vitreous are also transparent, and yet the pupil is black, the background of the eye invisible. Why is this? Until the ophthalmoscope was devised the answer ran as follows: Luminous rays entering the eye through the pupil form an optical image on the retina and are completely retained within the eye, partly because they are used up in creating sensa- tions of light, but chiefly because they are absorbed by the pig- ment cells of the retina and choroid. As a proof of this teaching there was adduced the fact that the pupils of so-called albinos, white rabbits, for example, did not appear black, but were red, therefore luminous, This doctrine is easy to disprove, for the pupils of albinos appear red, not on account of light that has entered the eye through the pupil, but by means of luminous rays that have pierced the opaque coats of the eyeball, the sclera, choroid, and retina. To prove the above statement, take a white rabbit, put a hemispherical watchglass over its eye, and fill the space between glass and cornea with water. The glass should be blackened till transparency is destroyed, except over a spot corresponding to the pupil. If now the old doctrine were true, the pupil would appear just as bright as before; but such is not the case, for the pupil is black, although perhaps not so black as the pupil of an ordinary rabbit. Now scratch the blacking off the edge of the glass in a semicircular spot about 4 mz. diameter, making the cornea visible behind it. By means of a convex lens throw on this scleral area a strong beam of light (in a dark room) from a lamp; the pupil immediately appears bright red. Or any eye, not an albino, may be illuminated thus: Take a rabbit, dilate the pupil with atropin, and put the animal into a box holding the body rather firmly, but allowing the head to project somewhat as from a tight collar. In front of the rabbit’s head place a lamp with an untransparent chimney, but make a spot on it so that a beam of light can be thrown from the lamp in one direction only (in a thoroughly dark room, of course). The lamp flame and the orifice in the chimney are so adjusted that rays from the flame strike the rabbit’s eye from below upward. If the observer places his head close to the lamp chimney and looks as nearly as possible in the direction of the connecting rays into the rabbit’s pupil, he will find not only that the pupil appears red, but that the blood- vessels are visible within it. The fact that any eye is illuminated if the observer looks in the same direction as luminous rays entering it from a flame was dis- covered in 1846 by Cumming, and independently in 1847 by Bruecke. v. Erlach and his friend Brunner in the winter of 1846-47 a 102 OBJECTIVE METHODS OF INVESTIGATION. observed that they could illuminate the pupil with their specta- cles when conditions were such that the person under examination saw in the spectacles of the observer the reflection of a lamp ina dark room. These phenomena were explained in 1851 by Helm- holtz, and the ophthalmoscope was thereby discovered. It is a universal law that a reciprocity exists in a dioptric system between the object and its image; that is, ifthe image be considered as the object, luminous rays will traverse the same path backward that they originally took, and consequently the image will be pro- duced at the place of the original object. In the eye’s dioptric system—cornea, aqueous, lens, vitreous—the image of an object falls upon the retina if the adjustment is correct. Since luminous rays are by no means totally absorbed by retina and choroid, that part of the fundus of the eye covered by the image of a point of Fic. 36.—TLLUMINATION IN AN Eve. The luminous rays entering the eye under examination are shown black, those returning from it are shown red. light becomes in its turn a luminous object, light emerges from it, escapes in part through the pupil, and produces at the location of the original object an inverted, magnified, though very faint image of the illuminated area of the fundus of the eye. If by ordinary daylight we look into the pupil of an eye, our own pupils take the place of the bright object just mentioned ; but since our own pupils are not a source of light, that very area of the eye’s fundus which should reflect an image back into our pupils remains dark, and conse- quently the pupil of the person under examination cannot appear luminous. It is obvious that there are two methods of making the patient’s pupil luminous. One way is that of the experiment with the rab- bit just described. The atropinized rabbit’s eye is hyperopic, and therefore not adjusted for the flame, // (Fig. 36). The location of the flame’s image is behind the retina at 7/7’. On accountof circles THEORY. 103 of diffusion there is on the retina an illuminated area, ¢c. ‘This area, considered as object, emits rays diverging as if they came from the far point of the hyperopic eye; for example, the point, a, sends out rays (marked red) which appear to come from a’: consequently they do not allreturn to their source at the flame, but some of them strike the observer’s eye placed near the flame.? Indeed, Fig. 36 teaches us that the observer, if he accommodates for a’, ought to see a part of the fundus distinctly. The first method of making the pupil luminous consists in illumi- nating the fundus by means of a source of light for which the eye under examination is not adjusted. The second method consists in making one’s own pupil luminous by any physical artifice, that is, by making it the source of light for the eye under examination. We can do this by means of a reflect- ing glass disk and a lamp flame. The observer (Od, Fig. 37) and L¢, Fic. 37.—ILLUMINATION OF THE Eye py Means oF a Grass Disk. The figure is supposed to be in the horizontal plane. the patient (Pa) are opposite each other, and the flame (/7) is in the same plane with their eyes. The observer holds the glass disk before the eye in such a way that a line perpendicular to the sur- face of the glass passes midway between Fa and f7Z, Some of the luminous fays falling from #7? upon the glass are, according to the known law, reflected as if they came from //’ ; these pass, there- fore, into the pupil of Pa, appearing to come from the pupil of Od. But since only a part of the rays from // are reflected from G/ (another part passes through G/, and can, therefore, be neglected in this experiment), and since, moreover, the rays entering the eye, Pa, are partly absorbed by the pigment cells, and still others of those returning from Fa are again reflected by G/, it is evident that but 1 If we trace the luminous pencil returning from the upper part of the illuminated field (the upper c), we find that 04 can be at quite a distance from the flame without, getting outside the range of the returning cone of rays. 104 OBJECTIVE METHODS OF INVESTIGATION. littlelight finally reaches the observer, and that the pupil of Pa will be but faintly luminous. Nevertheless, the experiment with a bright flame and a well-dilated rabbit’s eye is easy to make. Here, again, it is possible to see the fundus distinctly if the eye of Od is adjusted for the place from which luminous rays appear to come. We can, therefore, say that the fundus of the patient’s eye is distinctly visible if the luminous rays appear to come from the pupil of the observer when his eye is adjusted for the appar- ent location of the fundus of the eye under examination. The devices for illuminating the fundus to be examined will be referred to on p. rzr4, “ Description of the Ophthalmoscope.” Therefore, in the following theoretical explanations we may assume this illumination as already provided for. We need only discuss here the general conditions under which the fundus of an eye can be seen in its upright image. Upright image. Direct method. The dioptric apparatus of the eye acts as a convex lens of short focal distance (79.87 mm). If the retina lies within the focal distance (fig. 38, H) the eye is hyperopic, rays of exit from the fundus are at the cornea divergent, the image of the fundus, a’ 0’, is virtual, upright, and magnified. The observer can see it if he accommodates for the location of the image. If the posterior focal point, f, lies exactly on the retina (Fig. 38, £) the eye is emmetropic, all rays emerge from the cornea parallel, an image is formed at infinity (that is, not at all). The observer can, however, see the fundus if he is emmetropic and does not accom- modate, for in such a case all rays in passing through the refractive media of the eye form an image on the retina of his own eye. Finally, if the retina lies behind the posterior focal point (ig. 38, M) the eye is myopic, all rays emerge from the cornea converging to the far point of the eye under examination. The observer, sup- posed to be close in front of the cornea of the patient’s eye, can receive on his own retina the image of the other's fundus only when he, himself, is hyperopic, and only when the (virtual) far point of the hyperopic observer coincides with a’, the actual far point of the myopic eye under examination. Therefore, to be able to examine the upright image of the fundus of any eye, the observer must be capable of making his own eye emmetropic, hypermetropic, or myopic, at will. The last is the easiest. With the aid of accommodation the hyperope and the THEORY. 105 emmetrope and, of course, the myope can adjust the eye for a near object, because the mechanism of accommodation can perceive by instinct that adjustment which will give the clearest vision. The myopic observer can make himself emmetropic by a neutralizing concave lens; the hyperope can accomplish the same result by a convex lens or by a proper effort at accommodation. Moreover, if the eye under examination is myopic, the emmetropic observer needs a concave lens to make him proportionally hyperopic; a Fic. 38.—EXAMINATION OF THE UPRIGHT ImaGe, In HyperorrA, Emmgrropia, AND Myopia. fis the posterior focal point, the red line is the axis. myopic observer needs for the same purpose a concave lens increased in strength by the amount of his own myopia; a hyperopic observer must increase his own hyperopia by such a concave lens or decrease it by such a convex lens as will make his (negative) far point coincide with the far point of the eye under examination. Fig. 38 shows us that the refractive condition of the eye under examination influences the magnification at which the. fundus of that eye appears to the observer. The stronger the hyperopia, the 105 OBJECTIVE METHODS OF INVESTIGATION. closer to the actual fundus lies the virtual image of the fundus seen by the observer, and the less is the difference to him between the size of the object and the size of the image. In case the eye under examination is myopic, the relations are not quite so evident, but it can be shown by a simple construction that in this case the mag- nification is more pronounced than when the eye is emmetropic. In Fig. 39, Pa is the eye of the patient and is at first emmetropic; the red arrow pointed downward represents an area of his retina. One ray from the tip passes appa- rently unrefracted through the nodal point, 4; all others emerge from the cornea of Pu parallel to the first one. These rays, if they enter the pupil of an observer’s eye adjusted for infinity, must intersect at a point of the retina of Od, which is found by drawing through 4¢ a line (dotted red) parallel to the ray (continuous red) of entrance. Suppose Pa is now myopic; the black arrow pointed downward represents an area of his retina ; rays passing out from the arrow tip would form an image, 7, at the far point if the observer did not intercept them, but on passing through the refractive media of Od, whom we assume now to be proportionately hyperopic, they form an image on his retina which must lie on the line of connection between 4; and ,. We see now, that the black upright arrow is decidedly larger in Od than the red one, that the former must be relatively increased in size the nearer y is ; that is, the stronger the myopia of Pua. Fic. 3y.—CoMPARISON OF THE MAGNIFICATION IN AN Emmetroric Eye anv 1n a Myopic Eve. Inverted Image. Indirect Method.—Fig. 38 (J7) shows us that we can see the fundus of a myopic eye without concave lenses. The observer need only retire (to the right) from the patient till he is beyond the image, a’ 0’, which is in the air, inverted, actual, and magnified, when he will perceive it if he uses his accommoda- tion for the location of this image. He sees an inverted image, and on this account the method is called the “examination of the inverted image.” It is evident that this examination is possible without the use of other means only when the myopia is of a high degree, for the lower the myopia, the larger and consequently the dimmer will be the aerial image, a’ 0’, and, therefore, the smaller will be the area of the fundus, whose image is at one time visible to the observer. But there is a very simple method of making any eye artificially myopic; for this purpose we use a convex lens. Ruete first introduced this practice into ophthalmology, and _ since THEORY. 107 then the examination of the inverted image has been generally applied. /zg. 4o illustrates the principle for the three cases—hyper- opia (77), emmetropia (£), and myopia (J). The drawing indicates that the refractive condition of the eye under examination has an influence on the size of the resulting in- verted image. The rays from the myopic eye, JZ, already conver- gent when they strike the convex lens, S S, are the soonest to be united at a focus, and, therefore, the smallest image is the result. Nr" Fic. 40.—ExaMINaTION OF THE INVERTED IMAGE, IN HypgropiaA, EMMETROPIA, AND Myopia. 7 is the posterior focal point, the red line is the axis. The rays from the hyperopic eye, /7, divergent when they strike the convex lens, S S,are the last to be united, and therefore the largest image is the result. The rays from the emmetropic eye, 4, are parallel when they strike the convex lens, S S, and the result is an. image of a size midway between the two others. Amount of magnification of the upright image. The upright image is a virtual one ; consequently its size cannot be compared with the size of the actual image without some explanation. This comparison is, however, not essential, since we obtain a good answer to the question as to the ophthalmoscopic magnification by comparing the visual angle at which an object (the optic disc, for example) appears, if it is in one case examined at a ‘ 108 OBJECTIVE METHODS OF INVESTIGATION. definite distance as an anatomical preparation, and in another case as a living object seen through the refractive media of the eye under examination ; that is, in the upright image. This ‘definite distance ” should be the distance of the observer’s near point. At the near point of our eyes objects appear under the greatest practical visual angle; but the near point differs in different individuals according to the age, and we are accustomed by experience to bring objects that we wish to examine most exactly not precisely to the near point, but to a distance of 20 to 70 cm., youthfulness of the observer being assumed. The question as to the ophthalmoscopic magnification becomes therefore the following: What is the relation of the visual angle under which the virtual image of the optic disc appears, to that visual angle under which the disc itself appears at a distance of 25 cm. ? In case the patient (Pe, /zg. gr) and the observer (Od, Fig. gr) are both emmetropic, the answer will be as follows :— Let a (fig. gz, 77) be 250 mm. from the principal plane, HW 7, and the size of the object, a 4, be 7.5 mm. The object then appears under a visual angle of - * 3__. since on the one hand, we have assumed the distance of the nodal point from the principal plane to be 5 #m., and on the other hand we can use the trigonometrical tangent instead of the angle itself, all angles being so small in this instance. But if @ 4 is looked at through the Le May 7A Fic. 41.—MaGniFICATION OF THE UpriGHt IMAGE IN aN Emmgtropic Eye. dioptric apparatus of the eye under examination (/%y. gz, 7) acting as a lens, then,-as the t £ figure shows, the wae agele is equal to x “ ; Thesimilarity of the triangles, d’ a” A’ andéa kK, makes 57 # = x = 3 . This last equation is 77 times greater than 1.5 255 In the second case (Fg. 42), when the patient’s eye is axis myopic, let the myopia be of 50D. Then the disc lies 7.6 mm. behind the posterior principal focal point, 7, and the far point, @ ’, is 200 mm. in front of the principal plane, HH (fig. g2). Let the observer (00) be go mm. away from the patient (Pa). Under these conditions the hyper- opic Od, having a virtual far point at a’, sees the arrow, a 4, at a visual angle, an — a’b/ K/a’ 155 mm., if we take the distance of the nodal point, A’’, from the principal plane, 7” H’, to be 5 mm. The numerator can be cebrnennd Pes means of a pair of equal triangles, as , and the iaenieston is, therefore, a seventeenfold one. The denominator, A’ a’, with our assumption above, is equal to 200—go—5 — he in the figure (a6 K = a/b’ K’) to be 6 X 205 mm. The equation then reads a 23. x = = i . Since a 4, ata digtenee i 250 is appen to 06, wathont the magnification of the PAHERE 9 eye, at a visual angle of i aap and since 3S is 20.5 3 times greater than a we find the desired magnification to be 20.5. THEORY. 109 By a corresponding process we find the magnification for a case where the patient has 5.0 D hyperopia and the (myopic) eye is zo mm. distant from Pa to be a fifteenfold one. Amount of magnification of the inverted image. Assume the patient to be emmetropic. To obtain the inverted (aerial) image use a convex lens of 20.0 D (S m. = 50mm.) focal distance. Since rays emerging from an emmetropic eye are parallel, the aerial image, a’ b/’, Fig. 43, falls at the focal distance, A’ a’, of the lens; and since, with the above ak Pa. iM. 0b H. Fic. 42.—MAGNnIFICATION OF THE Upricur ImaGe From A Myopic Eyes. assumptions, the ray of direction, 6 X,in the emmetropic eye, Pa, is parallel to the ray of direction, A’ 6’, of the lens, S S, the triangle a 6 & being thus equal to the triangle ab rye 3 a/b’ K’, then Se = Sage and since ab=1ns mm. aKk>=15 mm. a’ K’=s0 mm., then a@’6/ = a3. << 50 = 5 mm.,; in other words, the aerial image of Od is 5 mm. in size, about 3.3 times larger than the object, the disc. Since we are treating here of actual and directly comparable images, there is no need of considering the visual angle, and we can say at once that, with the above assumptions, the magnification is a 3.3-fold one. By 7g. 47 we can further perceive that the distance of the lens, S S, from the emme- tropic eye, a, is immaterial, and that the magnification increases with a weak lens and decreases with a strong one. Suppose a lens at A’’ with twice the refractive power of Fic. 43.—MaGniFICATION OF THE INveRTED IMAGE. SS; then the image, 4 /” a’’, falls at K?’ a’, just half the distance of A’ a’. There- fore the image, 4 ’” a”, is half the size of 0’ a 7,and the magnification only one and a half that of SS. If 2a has a myopia of 5.0 D and the lens (20.0 D) is go mm. from the principal plane of Pa, by the same reasoning we find an aerial image of the disc to be 44mm., about a threefold linear magnification. With hyperopia of 5.0 D, and the lens at zo mm. distance, the aerial image of the discis 5.6 mm. long, a 3.7-fold magnification. If the lens, SS, is placed so far from a that its focal point coincides with the anterior focal point of Pa, the refractive condition of Pa will have no influence upon the magnifi- cation; in emmetropia, hyperopia, and myopia it is the same. With the focal point of S S falling outside the focal distance of Pa the conditions change, the magnification is 1IO OBJECTIVE METHODS OF INVESTIGATION. weakest in hyperopia and strongest in myopia. (Farther analysis is unnecessary, since such problems are seldom applied in ophthalmoscopy. ) Ophthalmoscopic Field of Vision.— (1) Upright image. (2) /nverted image. (z) Upright image. That part of the patient’s fundus which the observer is able to see at one and the same time is called the ophthalmoscopic field. The question of its size can be best an- swered by applying the law of reciprocity. Every point in the patient’s fundus sends luminous rays into the observer’s pupil, every point of the observer’s pupil receives these rays if they are luminous; in short, the ophthalmoscopic field is coincident with that diffusion image of the observer's pupil which is made upon the fundus of the patient’s eye. To construct the image of the pupil, Pp (Fig. 44), wpon the fundus of the patient’s eye, draw lines from Pand p of O6 through the nodal point X to the retina of Pa, Then g’ P'is the image of /, in case Pais adjusted for Pf, which is obviously not always so. Consequently every point of Pp may Fic. 44.—THE OrutHatmoscoric FieLp or Vision, Upricut ImaGeg. produce on the patient’s fundus a diffusion circle instead of an exact image. The red lines represent the diffusion circle z 2’ of the point &, assuming the patient to be emmetropic and free from accommo- dation. If this is taken for granted, it is a simple matter to deter- mine the four conditions which influence the size of the ophthal- moscopic field. (a) The size of the observer's pupil must be considered, since the greater FP? is, the greater will be the image f’ P’ on the fundus of the patient’s eye. Asa matter of fact, the size of the observer’s pupil becomes of no consequence by reason of the small hole in the ophthalmoscope that is always placed before the observer’s eye. This hole in the mirror, therefore, plays the part of the observer’s pupil in Aig. 44. (0) The distance of observer from patient is of great significance; THEORY. III because, as the patient is approached, the hole in the mirror is brought closer and allows a larger image to be thrown on the patient’s fundus. The practical rule, then, in the examination of the upright image takes no account of the size of the observer's pupil, but emphasizes the importance of approaching as close as possible to the patient. (c) The size of the patient's pupil is also of great significance, It must be as dilated as possible, by closing the other eye, shutting off unnecessary light (dark room), excluding light from the most sensitive part of the fundus (macula lutea), or, if necessary, by the use of a mydriatic. That the ophthalmoscopic field is enlarged and the examination facilitated by a dilated pupil is seen in Fig. gg. A narrow pupil in the patient cuts off some of the rays and diminishes the size of the diffusion circle, z 2’. (2) The position of the point for which the patient's eye is accom- modated has the most direct influence upon the size of the diffusion image of /,and therefore upon the size of the field. Obviously the diffusion increases equally as the point of accommodation in the patient’s eye is withdrawn (toward the right in the figure ); if this reaches infinity, that is, if the patient is emmetropic, the field is greater than that of any myopia; in hyperopia it is the greatest, the point of accommodation being beyond infinity. Hence we may conclude that 7 the examination of the upright image the ophthal- moscopic field increases with increasing hyperopia and decreases with increasing myopia. In this study of the size of the ophthalmoscopic field it is always taken for granted that the entire fundus of the patient’s eye emits light. This is not always so. In practice we find, often enough, that only a small part of the field is illuminated, or consequently luminous and visible. The character of the mirror, the size and distance of the flame, are here the most important factors. The increase of the field with corresponding decrease in magnification of the image can be demonstrated as follows: On the atropinized eye of a rabbit place a small glass cylinder whose base is covered with a sheet of mica; fill the space between cornea and mica with water. The cornea is thereby obliterated (optically) and the eye made strongly hyperopic ; we see now a large area of the fundus scarcely magnified at all. Since the virtual image of the fundus lies relatively close behind the actual fundus, the most inex- perienced observer can easily accommodate for this image. The experiment is a good introduction to the study of ophthalmoscopy. The conditions are the same after cataract operations; but as the lens has only one- fourth the refractive power of the cornea, the hyperopia is not so great as it is when the cornea is obliterated. 112 OBJECTIVE METHODS OF INVESTIGATION. (2) Inverted Image. In this, also, the ophthalmoscopic field is coincident with the (diffusion) image of the observer’s pupil on the fundus of the patient’s eye ; but, on account of the interposi- tion of the convex lens, it is much larger than in the examination of the upright image. If the lens is held properly the size of the patient’s pupil has no influence, the size of the observer’s pupil very little influence, so that it is unnecessary to study these factors further. But the size of the lens and its focal distance and the refractive condition of the patient’s eye are of the greatest import- ance. This is easily perceived in Fig. 45. Here the pupil of the observer is assumed to be a point. A pen- cil of rays proceeding from it would, on account of the relatively great distance between Od and the lens, S S, be united close behind f, the focus of SS. If now the lens is so held that its focal point falls just in front of the plane of the patient’s pupil, the image of p will lie at or close behind this plane ; and, consequently, p’ P’ will be Fic. 45.—THEeE OrytHatmoscoric Fierp, INverTED IMAGE. the diffusion image of /, if the patient is hyperopic, or p’’ P” if he is myopic. Without going further, it is seen that the size of the patient’s pupil is without significance if the point of intersection, d, lies near the pupillary plane, and that the ophthalmoscopic fields, p’ P’ and p" P’’, become somewhat larger when the observer’s pupil is dila- ted. Every point of his pupil will then produce just such a field, p’ P’, and the individual fields will only in part be coincident. The influence of the size of S Sis shown in the coloring in Fig. 45. If S S is made small by reducing it to S’ S’, then only the areas, xn! or x’ x’’, receive rays from p and are perceptible. The influ- ence of the focal distance can be recognized by the fact that witha shorter focal distance the lens, S S, would have to be approached closer to the patient in order to throw the image of the observer’s 1 For the sake of clearness, it is assumed that the rays converging to the point, @, pro- ceed further in astraight line. As a matter of exactness this is correct only when d coin- cides with the nodal point. But there is obviously no radical error in using this license in a text-book. . THEORY. 113 pupil on to or close to the patient’s pupil; but the nearer S S is to the patient, the greater is the angle at d, and therefore the greater tf! P*. The influence of the refractive condition of the patient’s eyecan be seen in the fact that 2’ x’ is smaller than z’'2’’, and p’ P’ is smaller than p’’ P’’. The hyperopic eye (p! z'z’ P’) admits of a smaller ophthalmoscopic field, ceteris paribus, the myopic eye (p!/x’’ x’ P'’) a larger ; the emmetropic eye a medium field—she 'stze of the ophthalmoscopic field increases with increasing myopia, diminishes with increasing hyperopia. In practising the examination of the inverted image the proper distance for the lens is found by observing the image of the pa- tient’s iris. If the convex lens is held too far from the patient, that is, if its focal point falls in front of his eye, the observer sees an inverted image of the iris; if it is held too near, he sees a vir- tual upright image; and if it is held just right, that is, so as to throw the focal point the smallest distance in front of the pupillary plane, he sees noiris image. It is best, therefore, to move the lens back and forth till the iris image disappears, when the largest field will be visible. When it was said that if the lens were held properly the size of the patient’s pupil had no significance, it had reference only to the theoretical ophthalmoscopic field, it being taken for granted that the entire fundus of the patient’s eye emitted light. This assump- , tion is practically not fulfilled. On the contrary, the ordinary concave mirror illumi- nates only a part of the ophthalmoscopic field and makes it perceptible. Practically, then, the size of the patient’s pupil plays an important part in the examination of the inverted image. The beginner finds it hard or even impossible to see the fundus of the patient’s eye if the pupil be small. The principal reason for this lies in the fact that, as the pupil contracts, the brightness of the illuminating field (in the fundus of the patient’s eye) decreases, while the quantity of light reflected from the cornea remains unaltered. The corneal reflex, therefore, rather obscures the image of the fundus. From what has been said, especially from the examples given, we see that the ophthalmoscopic magnification is decidedly larger in the examination of the upright image than in that of the in- verted image; and further, that this magnification on the one hand, and the extent of the field on the other, stand somewhat in opposi- tion to each other. A good working rule may be deduced from this—first, to examine the inverted image of the fundus to get the largest possible view of it and its condition, and then to proceed to the examination of the upright image in order to study the details with the highest possible magnification. 8 114 OBJECTIVE METHODS OF INVESTIGATION, 2, DESCRIPTION OF THE OPHTHALMOSCOPE. Although Helmholtz’s original ophthalmoscope is now used only for particular purposes, we should honor its discoverer by describing his instrument first (77g. 46). It consists of a disk of three reflecting glass plates, 2, which form the oblique end of a brass tube, 4, and of an adjustment at the other end for putting in place a concave lens,c. The whole is held by a handle (not shown in the figure). The observer at d looks into the square end of the tube through the glass plates toward the patient’s eye. The visual axis cuts the glass plates at an angle of 30°. In order that the luminous rays coming from the lamp may be reflected in this direction, they must have an incident angle of 60°, an arrangement possible only when the lamp is placed quite at one side. This inconvenience must be put up with for the sake of the ad- vantage gained by the strongest pos- sible illumination of the fundus with the weakest possible reflex of the cornea. Helmholtz’s ophthalmoscope gives, however, under the best of circum- Fic. 46.—HetmHoitz's OpHTHALMO- score in Hoxizontat SECTION. stances, but feeble illumination. For The arrows indicate the path of the inci- B : dent rays. this reason Epkens used a glass disk with a coating on the back, a genuine mirror, in which a small hole was scratched for the observer to look through; but since there was still a reflex from the uncovered bit of glass, which, while it absorbed light, also confused the observer by throwing part of this reflex into his eye, the method was adopted of boring a hole through the glass itself. This hole formed a small canal through the thickness of the glass, and its walls had to be well blackened in order to avoid any confusing reflex from them. This could not be completely overcome unless the canal were made very short, which was possible if a polished plate was used instead of glass. Even with these improvements the plane mirror is still of feeble illumination. For this reason Ruete, to whom we also owe “the examination of the inverted image,” made use of the stronger con- cave mirror. This gives in front of its reflecting surface an in- DESCRIPTION OF THE OPHTHALMOSCOPE. II5 verted, reduced, actual image between mirror and patient; the plane mirror, on the contrary, gives an upright, virtual image be- hind the mirror, that is, an image at a greater distance from the patient. It is evident, then, that the concave mirror throws a greater quantity of light into the patient’s pupil, although this does not imply that the retinal area illuminated by the concave mirror is brighter than can be obtained by the use of a plane mirror. The circumstances influencing this condition are, however, too numer- ous to be disposed of in a few words. The concave mirror most used, on account of its handy shape and small price, is that of Liebreich (fig. 47). Its focal distance is generally between 7g and 20 cm. On the blackened frame sur- Fic. 47.—LigBreIcH’s OPHTHALMOSCOPE. rounding the mirror is a small adjustable arm, a, bearing a semicircular clip, 4, into which 6 lenses of different strengths, c, can be placed. The case provided with the instrument usu- ¢ ally contains five of these. There are, besides, two convex lenses of 73.0 D and 20.0 D, which can be used both for examination of the inverted image and for focal illumination. Asa rule, the weak plane mirror is to be preferred to the strong concave mirror. Jaeger devised an ophthalmoscope in which either a plane or a concave mirror could be introduced at will. Coccius obtained the same result by combining a plane mirror with a convex lens, the latter being replaceable by one of stronger or weaker focal distance as might be required, and according to choice, the effect of a concave mirror of great or small focus was produced. If the convex lens was removed there remained only the action of a plane mirror. 116 OBJECTIVE METHODS OF INVESTIGATION. Zehender accomplished a similar result by combining a convex lens of about zo.o D with a convex mirror; in this ophthalmo- scope changing the distance of lens from mirror produced the same effect as changing the lenses in Coccius’ instrument. An essential advance was marked by the introduction of the refraction ophthalmoscope. ig. 48 illustrates one of the best of its kind. The principle of it is the same as that of the simple Gi pr Fic, 48.—REFRACTION OPHTHALMOSCOPE. Liebreich instrument. It has the added advantage that behind the sight-hole there can be introduced lenses of varying strength mounted in a rotating disk. There are innumerable ophthalmoscopes. Many are but modi- fications of the above; some introduce other optical principles ; others, such as the instrument to examine one’s own eyes, or the binocular ophthalmoscope, serve a particular purpose. They need no description here. USE OF THE OPHTHALMOSCOPE. 117 3. USE OF THE OPHTHALMOSCOPE. The ophthalmoscope serves four purposes— (A) To discover and to deterinine the location of opacities in the re- fractive media ; (B) To study the fundus ; (C) To determine the refraction condition ; (D) To demonstrate differences in level in the fundus. In using the ophthalmoscope the observer sits in a dark room about 4o cm. in front of the patient. By the side of and somewhat behind the eye to be examined is the source of light, which may be an oil lamp or a gas flame; the flame should be large in any case. The source of light, the eyes of observer and patient, should all be in about the same horizontal plane; it is therefore of advan- tage to have lamp and stools for the physician and patient that can be raised and lowered. It is advisable for the physician to accustom himself, when making examinations of the upright image at least, to use his right eye for the patient’s right eye, and his left for the patient’s left eye, since this is the only way to get closest to the eye, and the discomfort of rubbing noses is thereby avoided. It must be acknowledged, however, that most ophthal- mologists do examine the patient’s left eye with their right. Another good plan is for the patient to turn his face toward his right while continuing to look straight ahead, since in this way his nose is brought to the side of the nose of the examiner. The patient is now asked to stare vacantly at the physician’s right ear if the patient’s right eye is to be examined, at the left ear if the left eye is to be examined; by doing this his pupil remains dilated and there is no effort at accommodation if the stare is a vacant one. Then the physician places the ophthalmoscope before his eye, and moves it about somewhat till the bright beam of light strikes the patient’s pupil, a proceeding that often enough mis- carries with the inexperienced observer, who fails to illuminate even the body, let alone the eye of the patient. The pupil appears bright red, and, of course, contracts somewhat under the stimulus of the light. This contraction is insignificant, because, if the atti- tude above mentioned is maintained, the light does not strike the most sensitive area of the fundus, the macula lutea, but falls on a portion of the retina which is less apt to cause a reflex pupillary reaction, 118 OBJECTIVE METHODS OF INVESTIGATION. (A) TRANSILLUMINATION. If a foreign body or an opacity is present in the pupillary area, it appears as a dark spot ona red ground. If this opacity is not very dense, a nebecula cornez, for example, it appears as a mere shadow on a bright ground. Any spot appearing black or dark by transillumination seems white, or lighter than its surroundings by focal illumination. The explanationis easy. Opaque spots are only partially or not at all transparent ; luminous rays proceeding from the fundus and falling on the opacities (from behind) are returned to the fundus and are not seen by the obser- ver. The reverse is true of focal illumination; rays reflected from opaque spots do not reach the retina of the patient, but are thrown into the eye of the observer. In locating an opacity one fact must always be remembered, that spots on the cornea and lens are immovable, while anything in the Fic. 49.—LocaLizaTIOoN OF OpaciTiIES IN CoRNEA AND Lens. vitreous is generally movable. If the patient be asked to look with jerky movements upward and downward, to the right and left, these unsettled cloudinesses of the vitreous continue to float within the pupillary area after the eye has ceased to move, till they slowly sink out of sight by their own gravity. They may have the shape of threads, clouds, lumps, or misty films. Opacities of the cornea have no movement independent of the eyeball. To distinguish them, in addition to focal illumination (~. 98) we use the phenomenon of parallactic displacement. Let the point a, Fig. 49, be an opacity of the cornea, the point 4 an opacity in an anterior layer of the lens about in the pupillary plane, USE OF THE OPHTHALMOSCOPE, IIg the point ¢ an opacity on the posterior surface of the lens. Then the observer, looking in the direction of the optical axis into the patient’s pupil, sees only one opacity, as is illustrated in u, Azg. 49. Now ask the patient to look downward; all the opacities now become visible, the corneal opacity lying below, the posterior lens opacity above, the opacity in the middle. This last, apparently, has not changed its place; the posterior one seems to have risen. (As a matter of fact, they have all three descended somewhat.) An apparent movement in a direction opposite to the actual movement of the patient’s eye is a proof that any opacity lies behind the pupillary plane; an apparent movement in the actual direction of the patient’s eye indicates a position in front of the pupillary plane. If the patient’s eye remains still and the observer himself moves, the opposite is true; that is, opacities lying in front of the pupil seem to move in the opposite direction, opacities behind the pupil in the same direction. The extent of this apparent movement gives us aclue to determine the distance of the opacity either in front of or behind the pupillary plane. The examination of corneal and lens opacities by transillumination can be completed by placing behind the sight-hole of the ophthalmoscope a convex Jens which allows the observer to approach closer to the opacity, and which magnifies it at the same time. Hirschberg and Magnus have developed this method and devised special instruments for it; the strong lenses of the refraction ophthalmoscope can, however, be used for the same purpose. Transillumination effects more than focal illumination in a case, for example, where an attempt is made to discover a small hole in the iris through which a splinter of iron may have passed into the eye. A luxation of the lens, or a movable lens, can best and easiest be recognized by transillumination. (B) EXAMINATION OF THE FUNDUS OF THE EYE. It is advisable for the beginner to commence with the examina- tion of the upright image of an atropinized eye. A rabbit is a good subject for experiment, since it remains still if placed in a suitable receptacle, has hyperopic eyes, and does not complain of blindness or discomfort at long seances. Moreover, its fundus has a very characteristic structure, whose lines and colors are easily de- scribed and drawn. The first effort consists of obtaining a view of the optic nerve entrance (papilla nervi optici). The observer, in examining a rabbit’s eye, looks from below upward and back- 120 OBJECTIVE METHODS OF INVESTIGATION. ward; he knows he is in the right direction when he sees that the usual red appearance of the fundus has changed to a white shim- mer. To be sure, the medullary fibers also return a white reflex, but much has been accomplished when even this is discovered, The best method is to begin at a distance of about 20 cm., and to throw the light from the mirror in various directions on to the pupil till a white reflex appears, then to approach as close as pos- sible to the eye under examination. If this effect is lost by inex- perience, begin over again in the same way, till the eye can be ap- proached very closely without losing this white reflex from the pupil. The next is the hardest task—to find the proper focal adjustment for the location of the virtual image of the fundus. As the observer knows that the object he is examining lies just in front of his eye, he accommodates instinctively and thereby prevents the most accurate vision; he must therefore try to imagine that the object of his attention lies far off, or in case this does not suffice he must neutralize his accommodation by concave lenses. On account of this instinctive accommodation the beginner is often able to see the fundus the easier, the more hyperopic the patient is, that is, the nearer the virtual image of the fundus lies to the actual fundus. If all this is successful, let the student take pencil and paper and try to reproduce what he sees in a drawing, even if it be imperfect ; this sharpens the attention decidedly and protects the student from many errors to which he might otherwise fall a victim. If the first difficulties are overcome and the student can see the upright image, the papilla, the retinal vessels, and the medullary nerve fibers in the rabbit’s eye, let him make the more difficult attempt to see the inverted image of the fundus (/7g. Zo, p. 107). Let us suppose that this attempt is made on man; we must then try to see the optic disc, first, because this spot on the fundus is the brightest and the easiest to describe, second, because it is insensi- tive to light, its illumination neither blinding the eye nor causing contraction of the pupil. On page 69 we saw that the papilla in man lies about 72° to 75°, reckoned from the nodal point, toward the nasal side of the fovea centralis. We must, therefore, after having induced the patient to gaze in a certain direction, look into the eye at that angle measured from the visual axis outward (toward the temporal side). The observer is now at about go cm. distance from the patient, USE OF THE OPHTHALMOSCOPE, 121 and he illuminates the pupil back and forth until it appears white, or at least a paler red. Then, holding the convex lens between his index finger and thumb, he introduces it into the path of the lumin- ous, rays, taking care that the left hand does not tremble,in the air but is supported by the little and ring fingers resting on the patient’s forehead. Generally the beginner sees nothing at the first attempt but reflexes—images of the mirror reflected from the con- vex lens or from the cornea, but by tilting the lens a little from the optic axis, the observer learns to obliterate from his visual field these disturbing images. Itshould not be forgotten, however, that if the lens is held too obliquely the fundus may be astigmatically distorted, and therefore the lens should be tilted only to the mini- mum extent necessary. If light has not been by this means diverted from the patient’s pupil, the last and hardest step comes now—for the observer to accommodate for the image in the air. Since the beginner generally has the impression that the object he is looking at is in the eye, he accommodates for that distance ; but the aerial image for which he should accommodate lies in front of the eye and in front of the convex lens, and, therefore, by accom- modation for the actual location of the fundus he cannot obtain a perfect view of the image. To learn how to conquer this difficulty, one can practise reading print held upside down and looked at through a convex lens, The convex lens gives an inverted image of the inverted print, that is, it gives an upright image between the lens and the reader, and the print is unreadable so long as the observer cannot bring about the adjustment neces- sary for the location of the aerial image between his eye and the lens. This adjustment can be more easily acquired by holding a needle at about the spot where he expects the image to be. If he cannot find this aerial image, let him try with a convex lens of 2 or 3 diopters, such as is found in any refraction ophthalmoscope. After the disc has been seen and an opinion formed concerning its normal or pathological condition, the student proceeds to exam- ine the fundus in detail. The neighborhood of the nerve sheath and the spot most necessary to vision (the macula lutea) can be brought into view by moving the convex lens; the rays emitted from the fundus pass in that case through the periphery of the lens, which acts asa prism to deflect these rays toward the base, and consequently the observer does not see that portion of the fundus which lies exactly opposite the lens, but other areas lying some- what to the side. To view the fundus at a still greater distance from the disc, the patient changes the direction of his gaze, or the physician moves 122 OBJECTIVE METHODS OF INVESTIGATION. ‘his own head and looks at the fundus from above, from the right and from the left ; but the upper half of the retina can be seen only when the patient looks upward. Although the various pathological changes in individual diseases will be discussed later, this is the best place to introduce a short description of the normal fundus. On the red ground is seen the lighter papilla with the retinal vessels arising from it. As to the ground itself, its color changes from yellowish-red to reddish-brown according as the individual is light or dark haired. Boll, the dis- coverer of the visual purple, ascribes the red of the fundus to the presence of a retinal purple, but this view is not tenable. Visual purple is a quite different red (rose, blue-red, hence the name pur- ple) and can be bleached out without materially changing the color of the fundus. Undoubtedly the red of the fundus is due to the blood of the choroid. The capillaries of the choroid are covered only by the transparent retina and the translucent but not trans- parent pigment-epithelium. The abundance of pigment in the epi- thelium has, consequently, the illumination being the same, the greatest influence on the color of the fundus. This abundance of pigment directly corresponds also to the pigmentation in other parts of the body; in the negro it is so great that the bloodredness of the choroid can scarcely be distinguished. The papilla nervi optict is the most remarkable spot of the fundus, and is the area at which every ophthalmoscopic examination begins. The name would indicate that something protrudes above the surface of the fundus, but that is not the case. Anatomically the condition is as follows (fig. 50): the choroid has a hole in it extending through the sclera; this aperture is crossed by a net- work of fibers from the scleral tissue. The optic nerve fibers have their normal medullary sheath as far as this network, the so-called lamina cribrosa (7g. 50), but inside this network, that is, within the sclera, the medulla is lost. After the naked axis cylinders have passed through the opening in the choroid they bend nearly at right angles and spread out as the innermost retinal layer as far as the periphery of the fundus. There is, therefore, no reason for call- ing it a prominence (papilla). The external border of the optic nerve sheath (Fig. 57) is a black circular line called the choroidal ring, because it bounds the open- ing in the choroid through which the optic nerve enters into the eyeball. Next the choroidal ring inward is the scleral ring (Figs. USE OF THE OPHTHALMOSCOPE. 123 5o and 57), and the hole in the choroid being greater than that in the sclera, the latter is therefore visible. The choroidal and scleral Fic. 50.—Secrion THROUGH Optic Nerve anp Papitia. (After Flemming.) Branches of the Vena nasalis Vena tempo- inferior. ralis inferior. Macula lutea. Branches of the Branchesof the Vena nasalis Vena tempo- superior. ralis superior. Fic. 51.—THe Normar Funpus 1n tHe Inverted Imace. (A/ter Jaeger ) The choroidal ring can be distinguished along the whole circumference, the scleral ring only on the right side. rings are, of course, not so exact as circles drawn by a compass ; in fact, the deviation from the circular form is so noticeable that the 124 OBJECTIVE METHODS OF INVESTIGATION. optic nerve sheath ought rather to be called egg-shaped. This may be the result of astigmatism (/. 728) or of an anatomical peculiarity of the sheath. In many eyes no exact rings can be found at all, or the choroidal ring is present only as small collec- tions of pigment at intervals. The real nerve sheath, thus bounded by two rings, is on its nasal half less sharply bordered and has a darker color; while on the tem- poral and larger half the color is lighter and the border more distinct. In the middle of the sheath is a lighter spot, the funnel-shaped depression, from the nasal side of which spring the arteria and vena centralis retina. This excavation sometimes extends over to the temporal side of the sheath and is therefore called the physiological cup (Figs. 143 and 745). The arteria and vena centrals retine while.yet within the cup are each divided into an ascending and a descending branch (fig. 57); each of these branches again, either within the sheath or just out- side of it, divides into nasal and temporal branches which spread out, tree-like, into the smallest twigs. Hence we distinguish an arteria nasalis superior and inferior, temporalis superior and inferior, the veins being the same. The arteries are known by their smaller caliber, their more extended course, their brighter color, and the so-called reflex—a bright line in the middle of the vessel. The veins are known by their greater thickness, more tortuous course, darker red, smaller and less bright central streaks (they may be entirely absent). The reflexes are clearly seen, however, only in the examination of the upright image. The nature of the reflexes is still a disputed point. One authority explains them as reflex from the vessel wall, another as from the blood column. Dimmer, who has lately taken up the subject anew, ascribes the narrow reflex of the veins to the play of light on the surface of the blood column, and the broad reflex of the arteries to that on the “‘ axis stream ’’—that is, to the rebound of light from the blood corpuscles flowing rapidly in the channel of the vascular tube. Only small vessels appear on the temporal and nasal side of the nerve sheath. These should be used in making the examination of the upright image (the direct method) as a test object for the proper refraction. About one and a half to two times the width of . the nerve sheath toward the temporal side is an area in which there are no blood-vessels, or at least none visible to the ophthal- moscope. This is called the yellow spot, macula lutea, with the fovea centralis, the area of most distinct vision. It varies in appear- USE OF THE OPHTHALMOSCOPE. 125 ance according as it is viewed in the upright or in the inverted image. In the upright image it appears about the size of the disc, distinguishable from the surrounding fundus by being somewhat darker in color; in the middle of it is a sickle or fan-shaped or rounded point of light. In the inverted image (zg. 57) the yellow spot in young persons appears to be bordered by a line describing an egg-shaped figure with its long axis horizontal. These phenomena can be thus explained: The light thrown on the fundus is partly returned as diffused, that is, each point of the fundus returns luminous rays diverging in all directions; each point, therefore, is luminous. Some of these rays reach the observer’s eye and enable him to see vessels, pigment spots, differences of level, etc. But on the inner surface of the retina there are regularly curved areas that act as concave or convex or cylindrical mirrors according to their curvature, and consequently rays proceeding from the ophthalmoscope are returned to form small reflected images—actual if in front of the retina, virtual if behind it. These images of the ophthalmoscope are seen by the observer only when a narrow cone of light from an image reaches his eye. The fact that the yellow spot, round anatomically, appears egg-shaped to the observer is explained by Johnson to be a distortion caused by the mirror and convex lens. There are other differences besides those given here, and the beginner is apt to call them pathological, although they are only modifications of a healthy fundus. One of the most common is the visibility of the choroidal vessels; they may be distinguished from the retinal vessels by their ribbon-like appearance, their arrange- ment in parallel groups, and their lack of branches. Again, the pigmentation may not be regular, so that the fundus loses its uni- form appearance and seems parceled off into divisions. One sees dark spots with bright red streaks between ; the streaks are chor- oidal vessels, the dark spots are the “intervascular spaces.” Finally must be mentioned the reflexes along the vessels, giving to the retina a peculiar glittering appearance, but easily distinguish- able from retinal opacities, which are constant and immovable, by the fact that the reflexes seem to be moved and displaced when the mirror is turned. (C) ESTIMATION OF REFRACTIVE CONDITIONS. Even when illuminating the refractive media (f. 278 et seg.), we may often determine whether the patient is hyperopic or myopic. In many cases retinal vessels are visible at quite an appreciable distance ; if now we find an actual, inverted aerial image in front of the patient’s eye, the condition must be myopia; if, on the other hand, the image is virtual, upright, and behind the patient's eye, the 126 OBJECTIVE METHODS OF INVESTIGATION. condition must be hyperopia. It is easy to decide which of the two is the case. Let the observer move his own head toward his right; if he sees the vessels, and if they make an apparent movement toward the left, that is, in an opposite direction, they belong to an image of the fundus inverted and in front of the pupil, and the eye is myopic. If, however, the vessels appear to move with the observer’s head, they belong to an image which is upright and behind the pupil, and the eye is hyperopic. In emmetropia or any trifling degree of myopia and hyperopia, the vessels of the patient’s eye are not visible at the usual distance because the ophthalmo- scopic field is too small ( f. zo9). To understand the principles of these apparent movements it must be remembered that these images of the fundus are projected by the observer toward the pupil of the patient, whose eye therefore seems to be at rest while the images of the fundus seem to move. That the movement appears to go with the observer’s head when the image is upright, against it when the image is inverted, we can understand when we turn to the explana- tions of the apparent displacement of corneal opacities in front of the pupillary plane, and of lens opacities behind the pupillary plane (f. 778). The point a (/%g. 4g) corre- sponds to the inverted image, the point c to the upright image. Obviously, it does not suffice to have determined whether the patient’s far point lies close in front of his eye (strong myopia) or close behind it (strong hyperopia), or at some distance from his eye (moderate myopia, moderate hyperopia, or emmetropia); our task is rather to measure the refractive condition. This can be carried out in three ways, namely :— (a) by the upright image (the direct method); (8) by the inverted image (the indirect method) ; (vy) by skiascopy (the shadow test). (a) The estimation of the refraction by the upright image is carried out by means of the refraction ophthalmoscope (/ig. 48). The emmetropic observer first tries to see the papilla without any lens at all; if he is not successful he introduces successively behind the sight hole of the mirror by revolving the disk a series of concave or convex lenses until he finds the lens with which he can see the patient’s fundus most clearly. This lens measures the amount of refractive error present, assuming that neither the observer nor the patient makes an effort at accommodation, and taking care that the distance of the lens from the patient’s eye is negligibly small—a condition admissible only in errors of low degree. In errors of high degree a distance of the neutralizing lens from the patient’s eye of five or more centimeters is of considerable importance, USE OF THE OPHTHALMOSCOPE, 127 since without taking this distance into consideration myopia might be found too great and hyperopia too small. Let us take an example. In Fig. 52, Pa is the patient’s eye, and has a myopia of ro.o D, therefore luminous rays emitted from the fundus of Pa will produce an inverted, * enlarged image, a’ 6’, at 745 m. = so cm. in front of the principal plane. Let the eye, Od, be 5 cm. from Pa ; supposing this observer’s eye to be emmetropic and free from accom- modation, it will see distinctly the fundus of Pa when using a concave lens which makes parallel the rays converging to 4’, in other words, a lens whose (negative) focus is equal to the distance between ZZ and a’ é’. If this concave lens is at 7 ev. in front of the principal plane of O4, that is, ~ cm. in front of the principal plane of /a, then the focal 100 cm. Sem 16.66— Diopters; the neutralizing lens is therefore 6.66— D stronger than the myopia of Pa. A corresponding example shows that an emmetropic observer free from accommoda- tion sees distinctly the fundus of an eye of zo.o D hyperopia at a distance of 5 cm. with a convex lens of 7. D placed 7 cm. in front of the principal plane of O4, that is, g cm. in front of the principal plane of Pa. The error is consequently 2.9 Diopters. Such palpable errors ought not to be made. If they cannot be avoided they can at distance of the lens would have to be 6 cm. and its refractive power ee Ze a2 : “] L fu. Fic. 52.—Errect oF THE Distance Between PATIENT AND OsSBRVER, IN THE ESTIMATION OF RzFrACTION BY THE UpriGuT IMaGE. least be modified if the neutralizing lens is placed close to the patient’s eye, rather than close to the observer’s own. Supposing in the above example of myopia of zo.o D the neutralizing lens is placed 7 cm. in front of the principal plane of /a, the lens should then have a focal distance of g cm., a refractive power of z7.zs— Diopters, in order to give to the emmetropic observer Od a distinct view of the fundus of Pe. The error in this case is only z.z7—Diopters. Since one must thus sacrifice the very advantages peculiar to the refraction ophthalmoscope, it is best, therefore, in cases of high degree of ametropia, to use another method, the shadow test, which, even at the worst, makes an error of only about 7.0 Diopter. If the observer himself has any refractive error, he must either correct it with a suitable lens during the examination, or make allowance for this error when estimating the patient’s condition. In any case he must take the refractive condition of his own eye into account. Suppose the observer is hyperopic 7.0 D and finds that —2.0 D gives him the best view of the patient’s fundus (the lens being at a negligible distance from the patient’s eye). The patient must then have a myopia of (—2.0 D) + (—3.0 D), that is, of 5.0 D,; for in this case luminous rays emerging from the patient’s cornea are not made parallel, but are only weakened enough in their convergence to intersect each other at the 128 OBJECTIVE METHODS OF INVESTIGATION. (negative) far point of the hyperopic observer, that is, 4% m., 33.3 cm. behind the principal plane of O4. It would require a concave lens strong enough to overcome this converg- ence, than is, the lens already found plus a second lens of — 3.0 Z, before the rays could be made parailel; this lens is therefore the real measure of the myopia. Or suppose the observer with myopia of 37.0 D sees the fundus of the patient’s eye with —2.0 D, then the patient has obviously 7.0 D —2.0 D= 1.0 D of hyperopia; for- a myopic observer of 3.0 D, with lenses of —2.0 D is changed to a myope of 1.0 D. He now sees (without accommodation) everything lying at z . in front of him. The virtual image of the fundus must therefore have lain sz m. in front of the observer (the distance between the two being neglected) or z #. behind the patient. An eye with negative far point of 7 7. is hyperopic to the extent of z.0 D. A general rule may be thus expressed: If the patient’s refractive condition is of a character opposite to that of the ametropic observer, the latter’s refractive error expressed in diopters ts added to that lens which neutralizes the error found. Tf the patient's refractive condition “4s of the same character as that of the ametropic observer, the latter's refractive error expressed in diopters 1s subtracted from that lens which neutralizes the error found. Suppose the observer is hyperopic, and that, without correcting his own ametropia, he finds the patient to be myopic; the myopia thus found must be increased by the amount of the observer’s hyperopia. Or, suppose the observer is hyperopic, and without correcting his own hyperopia finds the patient also hyperopic; the observer then subtracts his own hyper- - opia from that of the patient. And so forth. If there is astigmatism, the proper correction for both principal meridians cannot be made at the same time with spherical lenses. The retinal vessels parallel to one principal meridian are sharp, those perpendicular to it are hazy. The astigmatism might now be measured by selecting the lens correcting the error in one prin- cipal meridian, and then the lens correcting the error in the other principal meridian: the difference between these lenses would be the measure of the astigmatism present. The lens with which one sees distinctly horizontal retinal vessels measures the defect of the perpendicular meridian. But, unfortunately, retinal vessels are not always so obliging as to run exactly parallel to the principal meri- dians; therefore we may try to neutralize the astigmatism by means of cylindrical lenses. If we succeed and the proper correc- tion is obtained, the retinal vessels of both principal meridians must obviously be seen with the same distinctness. This method is warmly recommended by Parent. Ophthalmoscopes provided with cylindrical lenses are, however, very expensive, and the decision as to which is the neu- tralizing lens cannot always be depended on. Besides, it is most important to remember USE OF THE OPHTHALMOSCOPE. 129 that the distance of the lens from the principal plane of the patient’s eye will be a source of still greater error than that found in the measurement by means of spherical lenses. In any case we possess in the shadow-test a method which is much cheaper and more easily applied than that just mentioned. It is advisable to combine the examination of the upright with that of the inverted image (Schweigger’s method). Any astigma- tism, even if it cannot be measured, can be detected thereby with great speed and confidence if it is not too small. The method is as follows: If the optic nerve sheath of the patient’s eye is anatom- ically round, it appears, if the eye is astigmatic, to be an ellipse— an ellipse placed perpendicularly if the perpendicular meridian has the stronger curvature, and an ellipse placed horizontally if, as is seldom the case, the horizontal meridian has the stronger curvature, If now we use a convex lens? to examine an astigmatic eye in the inverted image, the diameter of the image of the disc must appear shorter in its perpendicular principal meridian, because the refraction in this meridian is greater (p. 709). The disc conse- quently appears to be a horizontal ellipse in the inverted image. The conclusion is unavoidable that there must be astigmatism if the shape of the disc is different in the upright image from that in the inverted. Any small departure in the shape of the disc from the circular form in only one method of examination does not warrant the diagnosis of astigmatism, because the disc anatomically is as often egg-shaped as round. (8) Estimation of the refraction by the inverted image (indirect method). This method, developed and particularly recommended by Schmidt-Rimpler, depends upon the following fact: An image, 4/’ (of the flame, 47), reflected from a concave mirror, Sp (Fig. 53), will be imaged distinctly on the fundus of an eye only when the location of the image, //’,and the fundus of the patient’s eye are conjugate foci; in other words, when 1If this is not at once clear, let the student read the section on ‘‘ Magnification of the Upright Image” (f. so7 ef seg.). If even this fails to make it clear and intelligible, the student may make use of an experiment to convince himself of the practical correct- ness of the statement, at least. For this purpose, let him take from the case of test lenses a convex spherical and a convex cylindrical lens of about +6.0 D and +4.0 De respectively. He then puts the two together, one over the other, and looks through this meridian-asymmetric system at the optic nerve sheath in “ig. 57. He will then notice that the optic nerve sheath, actually round, now appears elliptical, the long axis of the ellipse being perpendicular to the axis of the cylinder; in other words, the long axis of the ellipse lies in the same plane as the meridian of strongest curvature in the meridian- asymmetric system. 2 The lens must be placed so close to the eye that the anterior principal plane lies within the focal length of the lens. 9 130 OBJECTIVE METHODS OF INVESTIGATION. the far point of Pa, made artificially myopic by a convex lens, S.S, coincides with 7/7’. If now the refractive power of SS and its distance from the principal plane of Pa are kept permanently the same, then the spot where #/ should be thrown in order to produce in Pa a distinct #// depends only upon the refractive condition of Pa. If we know the location of #/’, we can determine by its distance from SS the refractive condition of Pa. To simplify this determination, Schmidt-Rimpler uses a convex lens of zo.0 D placed 7o cm. in front of the principal plane of Pa. If the patient is emmetropic, 7” must lie at the focus of the lens, zo cv. in front of it, in order to produce a clear image in Pa. If Pa is myopic, F/ must lie within the focal distance of the lens ; and if Pa is hyperopic, Fl/ must lie beyond this focal distance; every centimeter toward the lens indicating +.o D of myopia in Pa, and every centimeter from the lens indicating s.o D of hyperopia in Pa. In the practical application of this method the observer must (1) Estimate at what distance his mirror must be placed in order to reproduce a clear image, £7’, on the fundus of Pa, and (2) Measure where the image, 77”, lies at the instant that 7//’ is most distinct. The first problem can be solved only by an observer whose eye is corrected for the Pak. Fic. 53.-—ScHMmipt-RimpLer’s MetHop For MeasurinG REFRACTION. location of 7. The image, AV’, has itself become an object, and therefore reproduces an enlarged, inverted image, /7’/’, exactly upon 7/7’, and—neglecting the intensity of the illumination—coincides with it point for point. Although the observer cannot see 7/’ because the luminous rays proceed from him, he is able to see the coincident image, #/’/’, in case he is dioptrically corrected for the location of it. The second problem, to find out where “#/ (or rather F/’/’) lies, is solved in two steps: (1) by measuring the distance of the mirror, Sf, from the lens, SS, at the instant that 77’ is seen distinctly ; and (2) while the distance of the flame, //, remains unchanged, by throwing the image, 7/7’, on a screen and then measuring how far the screen must be removed from the mirror in order to make // perfectly distinct. The difference between these two distances is the desired distance of 77 and F7/’’ from SS, and gives at once the refractive condition sought. As is seen, this method is extremely ingenious, but not so very simple. According to Schmidt-Rimpler’s experience, it may be learned by any one who can use the ophthalmo- scope and who possesses good accommodative power, and it gives as good results as does the examination of the upright image, that is, to within 7.0 D of error. He advises a small and handy instrument (refractometer), with which the fixation of SS at zo cm. in front of the principal plane of the patient’s eye, as well as the measurement of the dis- USE OF THE OPHTHALMOSCOPE. 131 tance of the mirror from SS, is easily determined; also, instead of the ordinary gas flame, he advises the use of some other luminous object whose image admits of the recognition of the smallest errors of accommodation. (7) Estimation of the refraction by the Shadow test. Skiascopy. When an observer, Ob (fig. 54, A, B, C), sits opposite a patient, Pa, and looks at the pupil, PZ, of Pa with proper correction, there is formed on the observer’s retina a reduced and inverted image, P’ 7’. All luminous rays proceeding from the fundus of Pa through the pupil, g P, either do not reach the eye of Od at all, or they strike the Fic. 54.—EsTimMation oF THE REFRACTIVE CONDITION BY SKIASCOPY. fundus of Od between P’ and g’. For example, all rays from the point, f, irrespective of whether they come from one point or from several points of the fundus of Pa, must unite at p’ of Od, assuming, of course, that they are intercepted by the pupil of OJ. Let there be a luminous point, a, on the fundus (Fig. 54, A) of Pa,and let Pa be myopic; then at the far point of Pa and on the connecting line be- tween a and the nodal point there will be an aerial image, a’. The rays diverging from a’ will in part reach the pupil of Od beyond this a’, and in passing through the refractive media will be so united 132 OBJECTIVE METHODS OF INVESTIGATION. that the image, a’’, would result if the rays were not intercepted by the fundus of OJ. On the upper part of P’ f’ there is a bright dif- fusion circle, while the lower part of P’ p’ remains unilluminated. Now, since our retinal images are projected into the outer world as inverted, OS must therefore see the pupil of Fa bright below and dark above. If the luminous point, a, in Pa descends, say to 4, its aerial image must ascend to 4’, and there results a bright spot below in P’p’ of Ob, consequently the observer sees in the pupil of Pa a bright area passing from below upward fs when the lu- minous point in the fundus of Pa passes from above downward yr. The condition is exactly the reverse if OJ is within the far point of Pa (Fig. 54,8). It is seen that @ would produce its image at a’, but on account of the refractive media of Od this image is really at a’’, that is, in front of the retina, because the observer is corrected for rays diverging from p P while receiving convergent rays. The object point, a, produces therefore in this case a diffusion circle below at /” p’, and the result is that Od sees the pupil of Pa bright above and shaded below. Ifthe object, a, in Pa passes downward, say to J, a’’ passes upward to 6’’,; consequently the observer sees in the pupil of faa bright area passing from above downward in the same direction as the luminous point in Fa. And, thirdly, let the pupillary plane of Od lie exactly at the far point of Fa (fig. 54, C); then the object point, a, produces its image, a’, exactly in the pupil of Ob. Since the ray, pa’, is refracted to g’ and the ray Pa is refracted to P’, the entire area, pf’ FP”, is illuminated, and consequently the entire pupil of Pa appears luminous to Od. Movement of the object point, a, to @ in this case has no effect ; the entire area, ’ P’, remains luminous, and consequently the entire pupil, PZ, is bright. Not until @ passes downward still further than 4 does the image, 0’, lie on the iris of Od, in which condition no luminous ray whatever can reach pf’ P’, and at one stroke the whole pupil, Pf, becomes dark. If we apply what has been said for one object point, a, of Pa to the whole field of light, we obtain the following rule for the shadow test: If an observer looks at the pupil of a patient from a greater distance than that of the patient’s far point, and if the luminous area in the fundus of the patient’s ‘eye passes downward, the observer sees in the patient’s pupil aluminous area passing upward, that is, in the opposite direction to that actually taken by the lumi- nous area. If, however, the observer is within the patient’s far USE OF THE OPHTHALMOSCOPE. 133 point, then he will see in the patient’s pupil a luminous area passing in the same direction as the actual movement of the luminous area in the fundus. Finally, if the pupillary plane of the observer’s eye lies at the patient’s far point, then the observer sees no movement at all, but a sudden illumination of the patient’s entire pupil followed by an equally sudden shadow. In this we have, then, a method of finding the far point of any eye (free from accommodation) by approaching or withdrawing our own eye to or from the patient’s eye, until the movement of the light and shadow in the same direction with, or in the opposite direction to, the movement of the luminous field ceases, and is replaced by an instantaneous change from total light to total dark- ness. In order to apply this method generally in all refractive condi- tions, we must, first, be able to establish a common far point at about 30 ogo cm. This is made possible by means of the lenses of the oculist’s test case. Hyperopia we change into myopia, strong myopia we change into moderate myopia, by concave glasses, We must, second, be able to obtain a play of light in definite direc- tions upon the fundus of the patient’s eye. This is made possible by means of a lamp and a p/ane mirror. The plane mirror gives a virtual, upright image of a flame lying behind the observer; this upright image becomes an inverted image in the patient’s eye. Consequently a downward movement of the mirror image effects an upward movement of the luminous area in Pa (fig. 54). If the mirror is turned upward, the virtual image behind the mirror moves downward, while the illuminated area in Pa moves upward, a move- ment in the same direction with the movement of the mirror. If a concave instead of a plane mirror is used the conditions are reversed; that is, if the mirror is rotated upward, the luminous area on the patient’s retina moves downward. In putting the shadow test into practice the physician sits opposite the patient at about 50 cm. distance, and asks him to look toward a remote object on the nasal side of the eye to be tested. Then with the plane mirror light is reflected into the eye, and a few movements are given to the mirror to decide whether it is within or without the far point. This is literally the work of a flash! If the pupil is partly dark and partly bright, it is a proof that the pupillary plane of the observer does not lie at the far point of the patient. A movement of the visual area in the same direction as the mirror indicates that the far point is behind the observer ; if 134 OBJECTIVE METHODS OF INVESTIGATION. against the direction of the mirror, the far point lies in front of the observer. In the last case the observer approaches closer, rotating the mirror occasionally, until the light and shadow do not seem to pass across the pupil at all, but complete illumination gives place to total shadow. At this instant, by means of a tape-line already at hand, the distance of patient from observer is measured: a tape divided into centimeters (700 cm. == 1 1.) will show in diopters the amount of myopia present. lf the light and shadow move in the same direction as the move- ment of the mirror, indicating a far point behind the observer's eye, an effort must be made to reach this far point by receding from the patient, or in case this is impracticable, by placing convex lenses before the patient’s eye until the far point is brought nearer. The strength of the lens to be chosen can be approximately esti- mated by the appearance of the light and shaded parts of the pupil. If there is weak myopia, emmetropia, or weak hyperopia, the pupil shows a flat, circle-like area of light, which changes rapidly with slight movements of the mirror—a lens of +3.0 D may be tried. If, on the contrary, a high degree of hyperopia is present, the area of light is of smaller diameter and moves slowly with moderate rotation of the mirror—for this try a lens of + 5.0 to +7.0 D. Whatever convex lens has been used to bring the far point to the convenient distance of 30 to 50 cm., it must obviously be deducted in the final estimation. Suppose a lens of +. 5.0 D has displaced far point to 42 cm.; then we have a myopia of 199 = 2.5 D (approximately), or allowing for the convex lens, we have (-++5.0) + (—2.5) = 2.5 hyperopia. The shadow test performs the best service in measuring astig- matism, since in applying it one’s attention is often instinctively called to the presence of that condition. Suppose the far point is in front of the observer; he now approaches the patient with slight movements of the mirror upward and downward until he can no longer recognize the direction of the movement on the pupil. He now rotates the mirror toward the right and left; if the horizontal meridian does not have the same refractive condition as the perpen- dicular, there are still noticeable distinct movements in the shadow— movements in the same direction with the mirror if the far point of the horizontal meridian lies behind the observer, that is, if the hori- zontal is less myopic than the perpendicular meridian. The move- ment is against the mirror if the far point of the horizontal meridian USE OF THE OPHTHALMOSCOPE, 135 lies in front of the observer, that is, if the horizontal is more myopic than the perpendicular meridian. If the principal meridians of an astigmatic eye are not perpendicu- lar and horizontal (they usually are so), we shall notice, when the mirror is rotated around its perpendicular or horizontal axis, an obliquity of the light and shadow in the patient’s pupil, making the determination of the principal meridians an easy matter, since the direction of these movements will become parallel to those of the mirror when the latter is rotated in the planes of the principal meridians, Since the shadow test gives us the far point of the meridian of greatest curvature and the far point of the meridian of least cur- vature, we see that it shows not only the degree of astigmatism, but also its character; skiascopy, therefore, does better service than keratoscopy. The latter is undoubtedly more accurate, but it measures only one condition, the meridian-asymmetry of the cornea, while skiascopy ascertains the complete error in the eye, whether due to corneal astigmatism, to lens astigmatism, or to a disproportion in the length of the eyeball. The errors in the shadow test are probably as great as in any other objective method for estimating the refractive conditions. For an easy application of the shadow test, various ophthalmologists have devised various instruments. In order to make a rapid change of the lenses in front of the patient, some use a wheel in whose edge a series of lenses is placed. Others, in meas- uring the distance between patient and physician, attach a tape measure to the lenses placed in front of the former. There is nothing in all this essentially necessary, since a plane mirror, a case of test lenses, and a tape measure suffice to carry out the shadow test with all desirable accuracy. (D) DEMONSTRATION OF DIFFERENCES OF LEVEL IN THE FUNDUS. The optic nerve sheath does not always lie at the surface of the fundus. A depression in the middle has already been mentioned as the physiological excavation (~. 72Z). But the whole sheath may lie ata greater depth, a condition that is always pathological and of great diagnostic import. The presence of an excavation can be demonstrated in two ways :— (z) By the phenomenon of the parallax. For this purpose, look at the inverted image of the fundus and move the convex lens in its own plane upward and downward, to the right and to the left. If an excavation of the papilla is present, we see, when the lens is 136 OBJECTIVE METHODS OF INVESTIGATION. moved, an apparent movement of the papilla’s edge against the ground of the disc, the edge seeming to be displaced over the ground. This is illustrated in Aig. 55. Let Pa be an emmetropic eye with an excavated disc. Then from the point 4 (imaginary in this case), lying in the retinal surface, a pencil of rays (not shown in the figure) will emerge from the cornea parallel; rays from the point a, on the contrary, will emerge convergent. The image of a, therefore, lies at 7. If the observer puts a convex lens, S.S, in front of the eye, the image of ais produced at a shorter distance—say at a2’, and the image of J, which otherwise lies at infinity, is now at 47. For both images, or rather for their pencils of rays, 6 a’ 7 is the ray of direction. This is changed at once if the lens, SS, is displaced—say into the position marked in red. The eye and the lens are now decentered. In each pencil of rays there is ‘a new ray of direction, and these two new rays of direction are not coincident. In the first pencil, whose rays emerge from the cornea parallel to the axis, d 4’7, is the ray of direction; in the second pencil, whose rays emerge from the cornea convergent, the ray passing through the nodal point of the red lens is the ray of direction. Consequently the point 6’ moves to 6’7, the point a” toa@’’. An observer who is toward the right, at the pro- . a Outer Eage te F | Postertor or Inner Lge 7 F of Lia. ——___—. Duct ofa Mecbomiar Gland. fp 7A EER Lilermerginal Lorton of the Lia Fic, 57.—SECTION THROUGH THE Upper Lip. (A/ter Waldeyer and L. Schroeter.) A rigid adherence to this procedure will save the beginner many a blunder. How often has it happened that a sore eye is treated with all manner of washes as a catarrh until the patient goes to some other physician, who pulls from the lid the irritating lashes overlooked by the first one, whose attention had been attracted by the redness of the eye itself. DISEASES OF THE LIDS—-HERPES ZOSTER OPHTHALMICUS. 143 I. DISEASES OF THE LIDS. Anatomical Introduction. fig. 57. The eyelid is developed in the embryo from a fold in the skin. During development the inner surface of the lid loses the histological construction of the outer skin and becomes mucous membrane, the conjunctiva palpebra. A plate of thickened connective tissue, the cartilage of the lid, ¢avszs, gives to the lid a certain degree of stiffness. Between this cartilage and the outer skin lies the closing muscle of the eye, musculus orbicularis palpebrarum. Between this muscle and the external skin lies a relaxed, elastic connective tissue, poor in fat. Since the skin of the lid is very tender and thin, it is easy for extravasations of blood, effusions of blood and of water (edema), and such like to take place. The external surface of the lid ends with the rounded-off anterior lid edge; the inter- nal surface of mucous membrane ends with the abrupt posterior lid edge. Between these two lid edges lies the intermarginal space, which is 2 to 7 mm. broad, becoming smaller toward the angles, especially toward the outer one. Along the posterior lid edge one can often with the naked eye and always with the magnifying glass see a row of about 20 fine points, the exit ducts of the A/ezbomian glands, whose secretion serves to lubricate the lid. The anterior lid edge carries the lashes, c7/a, the upper lid having z00 ¢o 150, the lower lid half as many. In the hair bulbs there are little fat glands, some large and some small, the A/o//ian glands, whose exit ducts are at the side of the hair shafts on the intermarginal space. The edges of the upper and lower lids unite at an angle, in the canthus externus (Fig. 64) and again at the canthus internus, which has the shape of a horseshoe, embracing a small mass of metamorphosed skin, the caruncula lacrimatis. The lids in winking act as a moist cloth to wash away all dust, mucus, and tears from the outer to the inner angle into the tear sac, from which everything fluid is conducted through the nasal duct into the nose, leaving everything solid at the inner canthus to be removed as opportunity offers by the fingers or by washing. ‘The lids protect the eye from dryness and from accidental touch by involuntary closure; the lashes of the upper lid form a rake to catch any dust falling from the air. 1. DISEASES OF THE SKIN OF THE LID. All diseases described in any text-book of skin diseases are occa- sionally found on the skin of the lid, but I will limit this descrip- tion to those few having especial interest to the ophthalmic sur- geon. We may discuss them, therefore, according to their order in the different layers of the skin. (2) Herpes Zoster Ophthalmicus.—This disease is an acute febrile one, and begins as such with general systemic disturbance, prostration, headache, and loss of appetite, followed by chill and a ‘fever. Certain nerves, particularly the nervus supraorbitalis, n. supratrochlearis and infratrochlearis, are painful, the pain growing so intense as to radiate over the entire side of the head. Less often is the territory of the nervus infraorbitalis (second branch of the trigeminus) involved. These introductory pains last some time in one case, a few hours in another, or may even extend over months 144 DISEASES OF THE LIDS, inathird. In the end the skin disease discovers itself in the form of red spots that are confined closely to the territory of the diseased nerve. One or two days later small, watery blisters appear upon these red spots; this fluid becomes richer in cells and more like pus. Finally the blisters dry up, leaving a crust behind, under which, in many cases, a superficial layer of the true skin melts away, so that when these crusts are thrown off, healing takes place with the for- mation of a scar. The healing of the eruption is by no means the end of the disease, for nerve pains, hyperesthesia, or anesthesia may remain for a long time afterward. The essential location of the disease is in the nerve itself and that part of the Gasserian ganglion belonging to it; in a few autopsies these have been found in a condition of pronounced inflammation. The cause of the disease is not well known. It is recognized by the eruption along the course of the nerve, it being a particularly diagnostic point that the eruption does not pass the middle line of the forehead and nose. The prognosis is good, assuming that the nerve twigs supplying the cornea are not af- fected. If they are, the result may be ulcers and scars of the cornea. Treatment should be confined to suppressing the pain by morphin, and by powdering the diseased skin area with a mixture of zinc oxid and starch (Zinc. oxid. 5.0, Amyli 20.0), in order to hasten the drying up of the blisters. If crusts have formed, they can be softened by borated vaselin or any other mild salve. (6) Eczema.—This is a protean disease. It begins as a shot- like, a vesicular, or a pustular eruption. This dries in scales or crusts. Beneath the scale lies the reddened skin, either moist or dry, its tissue being more or less infiltrated, and sometimes super- ficially eroded or necrosed. The most prominent subjective symp- tom is itching. Eczema is seen on the lids in all its manifestations, being as a rule only the continuation of an eczema on the face or about the nose and ears; or it may be the result of some disease of the con- junctiva and cornea which has caused an abundant secretion of tears. Tears have in themselves irritating properties, as may be seen in any case of eyes ‘red wept.” To besure, the skin is rather more resistant than the mucous membrane of the eyes and nose, but the skin of the lid is much thinner than the skin of the rest of the body, and it is particularly delicate in blond, scrofulous children. When such children rub away with their little hands ABSCESS, 145 the tears welling up from the eyes, the combination of the softening effect of the moisture with the mechanical effect of the rubbing will easily produce an eczema. Of special interest to the surgeon is that eczema, relatively seldom, I am sure, produced by a wet bandage saturated with antiseptic fluid (sublimate eczema). The treatment consists in protecting the skin and oiling the lids with vaselin or some simple salve. If there are scales they can be gently removed after softening them with warm oil. Moist spots can be protected with a paste of salicylate of zinc (Zinc. oryd. 70.0, acid. salicyl. 0.1, Vaselin 10.0), or with a salve of white precipitate ointment (Aydrarg. precipitat. alb. 1.0, Vaselin 10.0). If there is a superficial erosion beneath the scales, painting with a two per cent. solution of nitrate of silver is of value. (c) Abscess.—If in addition to the four known signs of inflam- mation (calor, tumor, rubor, dolor) we find fluctuation as a fifth, there is an abscess. On the lids the signs of an abscess appear in certain diseases quite distinct from each other, but which may be treated by one method. The differentiation into furuncle and abscess is doubtless pathologic, but is only of academic interest to the physician as well as to the patient. (a) FuruncLE.—The disease begins with a pricking pain, the painful spot being hard to the touch, owing to inflammatory infiltra- tion. The skin is red with a full capillary injection. All this vascular hyperemia and infiltration produces a swelling. The center of the diseased area dies, and is thrown off with a slough of some part of the surrounding surface of the skin, which is replaced by a connective-tissue scar. Necrosis of a bit of tissue is therefore diagnostic for furuncle. When necrosis attacks a hair sheath with its adjacent sebaceous glands (the cutis itself), we speak of follicular furuncle ; if necrosis begins beneath the skin, we speak of cellular furuncle; if the necrosis includes a large section of the skin, we call the disease anthrax or carbuncle. This is always severe and may lead by sepsis of the whole body to death itself. Particu- larly in the severest form of furuncular anthrax it is usually possible to demonstrate the cause as an infection with an animal poison. An anthrax carbuncle produced by inoculation with anthrax bacilli gives a type of the condition. Inoculation is generally brought about by the dirty hands of the patient himself; an actual wound of the skin is scarcely necessary, since the hair sheaths are, as C. Hueter states, mouths in the skin through which any infection may be carried. Here and there inoculation may be brought about by the bite of insects that have settled on diseased cattle or any other infectious object. It may be added, too, that many tropical insects carry in themselves such a strong (chemical) poison that their bite or sting can produce a furunculous inflammation. In our country the greatest evil of this kind is the sting of bees or wasps, which can lead, however, to no more than a severe inflammatory swelling. 10 146 DISEASES OF THE LIDS, The majority of furuncles are at the edge of the lid, and will be spoken of later under hordeolum, though there are, less often, however, genuine furuncles on the skin itself. (@) PHLEGMoN, PSEUDO-ERYSIPELAS.—Lid abscess in its narrower sense is most usually seen in children, and generally appears on the upper lid. The lid is hot, red, and painful. A spot, at first hard, but later softer, assumes after a few days a yellow color, and finally points with escape of pus. The diagnosis from furuncle lies on the one hand in the absence of necrosis, and on the other in the more diffuse character of the diseased process, and in the more apparent evidence of fluctuation. Itis scarcely possible to draw a distinction between cellular furuncle and abscess. A lid abscess results gener- ally from injury, especially a bruise; but how the infecting germs obtain entrance beneath the skin cannot always be demonstrated. Prognosis of furuncle and abscess depends upon the nature and amount of infection. As we cannot estimate this circumstance, we must judge by the appearance and size of the area involved. Treatment consists in making an incision as early as possible and with antiseptic precautions, a removal of diseased tissue, and an antiseptic bandage. (2) Hemorrhage, Hemophthalmos externus.—A hemorrhage into the lid depends— (z) Upon an injury to the lid itself or to the adjacent tissue. (2) Upon injury to remote parts, and (3) Upon a general dyscrasia, scorbutus, for example, where there is no actual rupture of any vessel, the blood corpuscles merely escaping through the uninjured but abnormally relaxed vessel wall. If a blood-vessel in a lid is ruptured a large quantity of blood may be poured out on account of the yielding nature of the tissue. The lid appears bluish-red or black, and the swelling is so great that the patient practically loses the use of his eye. Laurence says that in the ordinary fist ight of Englishmen the seconds are accus- tomed to make occasional incisions into the puffy lids of the fighters and to squeeze out the blood, so that the fight may proceed. The first kind of hemorrhage can be caused (a) By a dull instrument. (2) By minor surgical operations or by leech bites in the vicinity of the lids, or (c) By rupture of a blood-vessel by severe coughing, sneezing, or vomiting. EDEMA. 147 The second kind can be caused by fracture of the skull. For example, a fracture of the roof of the orbit, or of the base of the skull, may lead to a hemorrhage into the cellular tissue of the orbit. This blood becomes visible in the conjunctiva of the eye- ball and on the inner surface of the lid, and shows itself on the outer surface only when it has passed through the tarso-orbital fascia—the tissue connecting the lid with the circumference of the orbit. The ¢dzrd, hemorrhage by diapedesis, has no real interest for the ophthalmic surgeon. If a patient is seen with a “ black eye” which he cannot open on account of the swelling, it is of first importance to determine whether or not the eyeball is injured. If it is not, then treatment is scarcely necessary; the blood will disappear of itself in two or three weeks after having assumed various shades of color. If the patient insists on treatment, lead water compresses and a pressure bandage may be prescribed. (e) Edema.—The lids are the favorite seat for any fluid deposits, and they may become so abundant that the patient finds it impossible to open his eyes, and he is much distressed thereby. The most significant sign is the persistence of a small dimple when the swelling is gently pressed by the point of the finger. These collections of a 5 3 . Fic. 58.—DesMARRES” lymph in the skin and the tissue beneath it are Lip Exevator. only in part of an inflammatory nature. When they are so they must be considered as indicating a local disease. For example, a lid edema is a regular accompaniment of a furuncle or abscess, and disappears very quickly when exit is given to the pus. Again, lid edema is a very grave sign when there is an in- flammation of the conjunctiva or bulb or of the cellular tissue of the orbit. Since it is generally painful and sometimes mechani- cally impossible to open the lids when an inflammatory edema is present, the significance of such an edema is often incorrectly in- terpreted. It is a good rule to follow, therefore, first to feel of the lid itself{—a hard and particularly sensitive spot indicating furuncle or abscess; then to open the lids, if necessary, by means of a Desmarres’ lid elevator (Fig. 58). In case the edema can be traced to some disease of the lid, the 148 DISEASES OF THE LIDS. conjunctiva will be only slightly or not at all inflamed, the eyeball normal and easily moved. If, on the other hand, the edema is of graver significance, the conjunctiva is found inflamed and swollen, the deep vessels of the bulb are injected, the bulb itself prominent and scarcely movable. (The significance of this sign will be dis- cussed later.) Non-inflammatory edema is also as a rule a sign of disease, though the disease may not always be so easy to find. In some cases the edema must be called the disease itself. If a patient is seen with edema of the lids for which no local cause can be found, search must be made for some disease of the heart, kidneys, or liver. The general dropsy of kidney disease shows itself with par- ticular preference on the lids; a light edema, after scarlet fever, for instance, being a hint for the physician to think of scarlet fever nephritis. Again, a lid edema may be a sign of trichinosis, appear- ing toward the end of the first week of the disease. It is scarcely necessary to treat a lid edema locally after some cause has been discovered, but in cases where the edema must be called idiopathic we may use a pressure bandage and massage or, at the worst, an excision of small strips of skin. witH SHARP HooK FOR TEARING THE CAPSULE. This procedure gradually drove from the field the method of depression that had alone ruled to the middle of the eighteenth century. Brilliant results were obtained by it, but certainly in one- Fic. 128,—Davigv's Fiap Incision. tenth of the cases there was suppuration of the cornea, or, at least, an inflammation in the eye that led to complete and hopeless blind- ness. As the suppuration was explained by the separation of the flap, v. Graefe decided to avoid a corneal flap by (z) making the inci- sion in the sclera, and (2) carrying it along a great circle of the sphere ; but since in such a cut the iris prolapsed,an accompanying excision of the iris became imperative. To prevent the aperture in the iris V. GRAEFE’S PERIPHERAL LINEAR EXTRACTION. 349 from admitting too much light, incision and iridectomy were made above, where the upper lid could cover them. The result justified expectation. Suppuration of the cornea became noticeably less, while the failures and losses were reduced one-half. On the other hand, chronic iritis and cyclitis were more frequent than before, and led occasionally to sympathetic inflammation of the other eye. (4) V. Graefe’s Peripheral Linear Extraction.—Instruments: Lid speculum, fixation forceps, v. Graefe’s cataract knife, iris forceps and scissors, hook, two Daviel’s spoons, Weber’s scoop (/’%g. 729) or lens spoon (/#g. 730). The surgeon stands at the patient’s head for the right eye, he sits or stands at the left side for the lefteye. For the first step, the zvcis¢on, the knife is entered at a (Fig. 737) toward the center of the anterior chamber, in order to make the wound on the inner surface of the sclera as large as that on the -outer surface. When the point of the knife has reached the center of the pupil it is directed toward the spot of exit, 6, and the cut is completed by a sawing motion. If the knife were held parallel to the plane of the iris, it would cut its way out in the red dotted line; but since this is not the intention, the knife must, during the cut, be turned on its long axis so as SNCS NZLINAN anos77zuwan (|S gradually to bring the edge more and 7 ae ; Lens § more forward (or upward). When the a "Shoe: Cnty perro neersent sclera is pierced, the blade is again turned so as to lie parallel to the conjunctiva, in which position the conjunctiva is separated from the sclera; after this has been accomplished for the distance of 270 37 mm. the blade is again turned forward and the conjunctival flap completed. This serves to effect an immediate closure of the scleral wound. Fic. 131.—V. GrazFe’s PERIPHERAL LINEAR EXTRACTION. The cut is not absolutely linear, that is, it does not coincide with a great circle ; it is rather an incision with the formation of a very small flap of 7.5 to 2 mm. breadth. The second step, the z7dectomy, is now made. Occasionally the iris is floated out by the aqueous as it escapes after the incision is completed. The iris is in any case seized by the iris forceps (zg. 89), pulled from the wound, and cut with one stroke of the 350 DISEASES OF THE LENS. scissors curved on the flat, the scissors being beld parallel to the scleral wound and pressed firmly against the eyeball, The third step, cvs¢o/onzy, consists in opening the lens capsule. For this purpose a capsule hook (/%g. 727) is introduced into the wound at the angie to the right and passed obliquely to the left till it reaches the edge of the iris, and is then turned to bring the point toward the capsule, over which it is drawn in a horizontal direc- tion ; the point of the hook is thus made to cut a flap in the anterior capsule. The fourth step is the de/ivery. For this purpose one Daviel’s spoon is placed at the upper lip of the wound parallel to it, and a second is pressed gently against the lower third of the cornea until the greatest diameter of the lens has passed beyond the wound. Pressure is then stopped, and the lens is pushed out from below. Any remaining fragments of cortex may be expelled by stroking the cornea with the Daviel’s spoon. Care must be now taken that the iris is not engaged in the wound; if it is, it must be pushed back into the anterior chamber, or if this is not successful, it must be picked up again in the iris forceps and cut off. If vitreous presents in the wound before the lens is delivered, all instruments that might cause pressure on the eyeball must be removed, and the lens extracted by the wire scoop (/%g. 12g) or by the spoon (Fig. 130). In the last twenty years we have learned that in suppuration of the cornea, it is not bad nutrition of the flap but infection which plays the principal role! Since at the present day we can with almost absolute certainty prevent infection, the dispute over Daviel’s and v. Graefe’s operations (long ago decided in favor of v. Graefe’s) has broken’out anew. In favor of Daviel’s operation is the retention of a round and movable pupil, which looks better, causes no dazzling, and to a certain extent offsets the lack of accommodation by the fact that it is reflexly contracted when near objects are gazed at; peripheral vision is also better with a round and contracted pupil than with an iris coloboma; and the danger of sympathetic inflammation in the other eye is less in Daviel’s operation. On the other hand, the danger of iris prolapse and its attendant evils is greater in Daviel’s. Landolt has instituted inquiries among ophthalmic surgeons of all countries. As the result of his questions, and of his own ex- perience, Landolt has formulated the rule that the operation with- out iridectomy is suitable only for the best cases, that is, for cataracts in which a smooth and complete delivery of the lens may be anticipated in patients of a healthy, calm, and intelligent disposition. I have myself always operated with an iridectomy, and shall for the present stick to it. I acknowledge that ‘‘complete success’’ with Daviel’s method is of more value to the patient than the same visual acuity obtained after a v. Graefe’s operation, but that the chances are less to attain this result in Daviel’s operation. Moreover, the danger of making v. Graefe’s incision too peripherally is essentially reduced by using /acodson’s zctston at the corneal limbus. (7g. 132.) TREATMENT—BEFORE AND AFTER, 351 The length of the incision depends upon the size of the nucleus. In case this cannot be correctly estimated in advance, it is best to allow room for the passage of a very large nucleus, say from 7 ¢o & mm. The ideal of a cataract operation is without doubt the delivery of the lens in an unruptured capsule. This method has been de- veloped and recommended by the Pagenstecher brothers. It de- viates from v. Graefe’s extraction only in this: that after the iri- dectomy is completed a spoon is passed behind the upper edge of the lens, and by gentle pressure on the lower third of the cornea the lens is encouraged to come out. If this does not succeed, the spoon is passed still deeper in, up to the posterior pole, and the lens is slipped out by pressing it lightly against the inner surface of the cornea. This method is applicable if the capsule is tough, the Zonula Zinnii (suspensory ligament) weak, and if there is any fluid between vitreous and lens. Experience teaches that in over- Fic. 132.—Jacopson’s INCISION. ripe cataracts the capsule is tough and the ligament relaxed. Loose- ness of the lens in the saucer-shaped depression of the vitreous may be expected in cataracta accreta and in overripe cataracts coupled with glaucoma. The few cases in which I have operated by Pagenstecher’s method have been among my most successful ones, 5. TREATMENT—BEFORE AND AFTER. In a cataract operation the greatest danger comes from infection. The surgeon must therefore exercise all his skill to find any sources of infection and to counteract them. Particular attention must be given to the lacrimal passages and the nose, the conjunctiva and lids. Diseases of these structures must be treated and cured according to principles already given. Unfortunately, in diseases of the lacrimal apparatus this is a wearisome task, and many surgeons prefer to shut off the tear sac from the conjunctiva, either by Eversbusch’s method of ligating the duct, or by Haab’s method 352 DISEASES OF THE LENS. of sealing the punctum by the galvano-cautery; others either ex- pose the sac and fill the space with iodoform gauze, or extirpate it. Chronic conjunctival catarrh in old people can be merely bettered, not cured. In such cases a radical disinfection immediately before the operation must be relied on. The general health of the patient needs attention as well. We know that old, and particularly poorly nourished persons, are prone to hypostatic congestion of the lungs during continuous rest in bed. We know also that:the closure of both eyes may induce physical disturbances, alcoholics being noticeably affected. Many old persons suffer from chronic bronchial catarrh and cough, or bladder troubles, all being conditions in which rest in bed is an aggravation or an impossibility. In such cases we must be content with a shorter or less constant period in the recumbent position. To alcoholics it is best to give a modicum of beer or wine. Active catharsis must be induced in all cases before the operation. The immediate preparation of the patient consists of a good soap and water bath to the whole body including the head, and a wet bandage of sublimate over the eye to be operated on. This band- age is to be removed on the operating table, the head enveloped in a cloth wet in sublimate solution, the vicinity of the eye thoroughly washed in sublimate z-zo00, and a second sublimate cloth, with a hole cut in it for the eye, is to be spread over the face. The eye is now cocainized with a drop of a five per cent. solution applied five times at intervals of one minute; the entire conjunctiva, especially the caruncles and the adjacent tissue, is to be wiped off with cotton wet in sublimate z ~ 7000, followed by a copious douche of sublimate solution 7.5000. The operation is now begun. During it no more sublimate is used for fear of provoking corneal opacities, but the eye is repeatedly flushed with a fresh and warm dhree per ceut. boric acid solution. In case the conjunctiva or lacrimal passages are not absolutely healthy, the wound and the inner canthus of the eye are powdered with sterile iodoform.' It is assumed that the cocain solution, the dropper, the instru- ments, surgeon’s and assistants’ hands are aseptic. The instru- ments are taken directly from a four per cen¢. carbolic acid solution ? The sterilization of the iodoform I leave to the druggist. About 5.0 gm. of iodo- form are placed in a wide-mouthed flask with about s0.0 ¢. ¢. of sterilized water, and boiled on a water bath for an hour. The water is then poured out of the flask and the moist iodoform dried on the water bath in the same flask corked with cotton. TREATMENT—BEFORE AND AFTER. 353 and the adherent fluid shaken off. The bandage consists of cotton dipped in 7 - ooo sublimate, and gauze. To avoid entropion the under lid is kept in place by a sausage-shaped roll of moist cotton, The dreaded suppuration in the wound may be avoided with cer- tainty by following these precautions. According to my experi- ence, the same cannot be said of iritis and cyclitis. These condi- tions are seen in cases where the wound was closed and remained so after the first change of bandage, the wound itself not being infected. In such cases we must assume that with some one of the instruments germs have been introduced into the interior of the eye without finding a resting-place at the scleral wound. It must also be remembered that inflammation may be produced by chemi- cal irritation, or by the swollen lens substance not yet removed. An iritis or a cyclitis may even result mechanically by rupture of an adherent remnant of capsule or iris. As a matter of routine I open the bandage on the afternoon of the second day, that is, thirty hours after the operation, because a moderate adhesive iris causes no particular pain, and may be present with no complaint from the patient. IfI find the bandage dry, the lid edges not reddened, no photophobia in the eye, I assume that no wound infection has taken place, even if the eye itself is quite red and the conjunctiva somewhat swollen (chemotic)—this last might be due to thesublimate alone. Sterile atropin solution is‘now dropped in, and a bandage reapplied. The same treatment is continued on the next day. Ifall goes smoothly the patient may sit upin bed the third day, and stand the fifth or sixth. The healthy eye is kept band- aged with the eye operated on for about five days. At the begin- ning of the second week the bandage may also be omitted from the eye operated on. Dark glasses should be used for protection against strong light, and the ciliary muscle with. the iris must be kept at rest by continuing the atropin. After two or three weeks the patient may be dismissed if the vicinity of the cut on the eye has meanwhile become pale. The eye is not to be used yet. Cata- ract glasses with permission to use the eye must not be given till two months after the operation. If healing does not take place kindly—if iritis, cyclitis, or suppuration in the wound appears—the eye must be treated according to circumstances. Energetic atro- pinization and warm compresses with boric acid solution are the principal remedies for iritis and cyclitis ; disinfection, or if neces- 23 354 DISEASES OF THE LENS, sary the cautery, is the best remedy for the suppuration. The striated keratitis (f. 252) needs no particular treatment. The results of cataract extraction are very good. In preantisep- tic days the loss was about five to six per cent. An eye was called lost which could not count fingers. Thanks to antisepsis, this pro- portion has noticeably diminished, at the hands of many operators sinking close to the vanishing point. ‘‘ Unsuccessful result” may be entered, if the patient has less than =~ visual acuity ; ‘‘ success- ful result,” if more than —. In nearly one-fourth of the operations a claim is made for V = 11) In a considerable number of cases the visual acuity first obtained will gradually decline. This depends upon the development of secondary cataract. 6. CATARACTA SECONDARIA. After the extraction of the cataract, the fragments of the anterior capsule are drawn out of the pupillary area—if everything goes well—and resting on the posterior capsule they finally become adherent to it. Capsular epithelium and the remnants of the cataract are therefore removed from the irritating action of the aqueous. The nutritive cells at the lens equator do hypertrophy, to be sure, but they are changed into normal lens fibers as far as their physical characteristics, if not their form, is concerned. The contents of the intercapsular space consists of new-formed, trans- parent lens substance, and of cataract debris, called lenticular mem- brane (f7g. 733). Any eye operated on and found in such a condition shows a black pupil, but by focal illumination there is seen behind the pupillary plane a delicate, striated, silk-like, often trem- ulous membrane,—the posterior capsule. Unfortunately, this typical condition is not always present. The fragments of the anterior capsule do not always withdraw from the pupillary area, nor adhere early to the posterior capsule; for this reason the debris of the cataract swells up in the anterior chamber, the epithelium of the capsule continues to grow, and as a result of this activity there is seen in the pupillary area a delicate or tough gray membrane, the simple secondary cataract. Visual acuity may be reduced to 1 It has seldom been my experience that a patient can read line No. 4 at 4 meters without error; but we may record V = =z if one or several of the letters of line No. 4 are named or guessed correctly. i a CATARACTA SECONDARIA. 355 counting fingers. Even this is not the worst that can happen. In many cases the capsular fragments adhere to the iris or to the edges of the wound, a condition termed cataracta secundaria accreta. The contraction in the cicatrix, the movements of the iris and ciliary muscle, all drag continuously on the secondary cataract, which gradually increases in prominence through this irritation; the contraction in the secondary cataract, too, drags on the sus- pensory ligament and the ciliary body, and provokes a chronic cyclitis. In consequence of all this the adherent fragments may develop into a tough membrane, and the eye gradually perish by atrophy. Fortunately, however, the eye in most cases calms down after a few months, so that the operative treatment of the secondary cataract may be discussed. _ ———Anterior Chamber Pastertwor Capsule ~~ Loree of inn, Fic. 133-—CLosurg oF THE Pupit arreR ExTrRAcTIon oF Cataract. (After Pagenstecher and Genth.) The treatment is discission. After thoroughly atropinizing the eye, the largest possible hole inthe membrane should be torn witha discission needle or cut with a Graefe’s knife exactly at the center. If the membrane is so tough that a dangerous dragging on the ciliary body is to be feared, dislaceration should be substituted for discission. Dislaceration consists in piercing the center of the membrane with two needles, and then by a leverage motion in tearing as large a hole as possible from the center toward the edge. Although the injury itself is trifling, there is developed at times after operations on secondary cataract a cyclitis resulting in phthi- sis bulbi, or even panophthalmitis. One must be careful, therefore, not to operate before the irritation caused by the first operation has completely subsided. On the other hand, the delay should not be unnecessarily long, since a recent secondary cataract is more delicate than an old one, and since the contraction going on helps 356 DISEASES OF THE LENS. to keep open a hole made seasonably enough. Ifthe wound from the first operation heals kindly, the proper time for discission of the secondary cataract will be about two months afterward. Many surgeons say that division of the secondary cataract by a fine scissors forceps introduced into the anterior chamber is free from the dangers of discission. I have had no experience in this method. II. APHAKIA. An eye from whose dioptric system the crystalline lens has been removed is called aphakic. All eyes operated on for cataract are therefore in this condition. The absence of lens can be recognized by a depth of the anterior chamber and by a tremulousness of the iris in case it is not adherent to the secondary cataract. The essen- ' tial proof of aphakia lies in the detection of the absence of the Purkinje-Sanson’s lens-images. Since the ophthalmologist can easily demonstrate the presence or absence of these images (f. 700), the detection of aphakia is correspondingly easy. With focal illu- mination we see in the pupil the shimmering striations of the pos- terior capsule or the whitish gray stripes of the anterior*capsule. Even when the lens has been removed in its unruptured capsule there is a moderate reflection at the border between aqueous and vitreous. This must not be confused with the lens-images: there are two of the latter, of unequal size,—the anterior image making the same movements, the posterior image making contrary move- ments, if the illuminating lens is moved back and forth in its own plane. The refractive power of the lens is about zo.0 Diopters, and this amount of power is lost to the eye by a cataract operation. An emmetropic eye becomes therefore in its aphakic condition one of zo.o D Hyperopia. An axis myopic eye of 4.0 D becomes 70.0 — 4.0 = 6.0 D hypermetropic. A hypermetropic eye of 4.0 D becomes 10.0 -- 4.0 = 14.0 D hypermetropic. The manner in which the eye is robbed of its lens has an especial influence on the refractive condition. A horizontal incision almost always flattens the cornea in healing in the perpendicular principal meridian, and the result is a corneal astigmatism, regular in the best cases, irregular in the worst, generally both regular and irregular. An aphakic person, if he did not happen to have a myopia of ro.0 D before the operation, cannot see distant objects distinctly, not to mention near ones; and he must resort to cataract glasses APHAKIA. 357 (p. 38 et seg.). If the astigmatism is regular, the lens must be ground sphero-cylindrical. A moderate degree of regular astig- matism may be overcome by the patient’s adjusting his glasses in an oblique position (f. 379). When the lens is gone the eye loses its ability to accommodate for a near point. To take the place of this the artifice must be resorted to of setting the glasses further away from the eye, or the neutralizing lens must be exchanged for stronger ones. For example, if the aphakic person has a hyper- opia of zo.0 D, his eye with +75.0 D can be adjusted for about +m. Asarule, patients learn this themselves, and they make an adjustment for middle distance by placing the glasses lower down on the nose. The statement that the effect of a convex lens is increased by setting it further from the eye is generally true only under the assumption that the object lies at a greater dis- tance than twice the focal distance of the lens. In aphakic persons this condition is fulfilled; not so in emmetropic presbyopia. In this latter condition, therefore, to set the glasses further off does not increase, but does on the contrary decrease the convergence of the luminous rays. Examples: An emmetrope with the lens removed reads at 25 cm. with + 74.0 D; the book is therefore removed more than twice the focal distance of the lens; for the focal distance is an =7 cm., twice this distance equals rg cv. An em- metropic presbyope reads at 25 cm. with + 4.0 D; the book is therefore not twice the focal distance of the lens, for °° = 25 cm., and twice this equals 50 cm. That setting the glasses further from the eye increases their effect, if the object is removed more than twice the focal distance of the lens, depends upon the following easily demonstrated fact: if the object is to the left at a great distance, the lens throws an image to the right nearly at its focal point. If I move the lens toward the left, the image passes—toward the right if reckoned from the lens, but—in space with the lens toward the left until the distance between object and lens equals twice the focal distance; if the lens is moved still further toward the left, the image passes toward the right away from the lens, so that from now on it passes toward the right in space. The proof of this statement cannot be given in an elementary way. From what has been said above, it is clear that an aphakic person can see as well with the glasses bought of the optician as he sees through the trial lens used by the surgeon only when the spectacles purchased by him are set as far from the eye as the lenses were in the trial frame of the surgeon. We must not neglect, therefore, to give the optician some suggestion concerning the desired distance at which the glasses should rest in front of the eye. This is of particular importance in sphero-cylindrical glasses. The rea- sons cannot be explained in a few words. Visual acuity of an aphakic person appears at the test greater than it actually is, because the letters seem enlarged. The nodal point of the new dioptric system—cataract glass plus aphakic eye —lies further in front of the retina than it does in the normal eye, and therefore everything is presented to the aphakic eye at a larger visual angle. 358 DISEASES OF THE LENS. The aphakic eye suffers at times from dazzling. This is due in part to the aperture in the iris made for the extraction of the cata- ract. Another reason may be found in the reflection produced on the curved surfaces of the cataract glasses. Many patients com- plain about occasional red vision, erythropsia, which appears inci- dentally when looking at bright surfaces. Perhaps red vision may be but a kind of dazzling. It disappears after a time. In one case I noticed rapid improvement after using iodid of potassium. Sug- gestion? III. CHANGES OF POSITION OF THE LENS. 1. Ectopia Lentis (Congenital Dislocation)—This anomaly occurs usually on both sides symmetrically. It is most common upward. Becker explains the condition as due to an unequal Fic. 134.—Downwarp DispLaceMenT OF THE LENS, UNDER TRANSILLUMINATION. (A/ter Jaeger.) development of the suspensory ligament. A displacement of the lens effects a decided disturbance of vision which can be improved in some cases by concave, in other cases by cylindrical lenses. If the pupil is so large or the displacement so pronounced that the edge of the lens presents within the pupillary area (fg. 134), the result is “double vision in one eye,” although it is not necessary that the double images be perceived by the patient’s consciousness. It depends on the distance of the object whether one of the images is more hazy than the other, and whether or not it is therefore neglected or excluded. Luminous rays from infinity striking that part of the pupil which has no lens are focused at a point behind the retina, while, on the contrary, rays passing through the edge of the retina may be focused in front of the retina. If the object fixed lies at a proper distance, rays refracted at the edge of the lens are LUXATIO LENTIS TRAUMATICA—MOVABLE LENS. 359 focused exactly at the retina, and the object is therefore seen dis- tinctly. In some instances a well selected convex glass may serve to unite into a sharply defined image rays passing through that part of the pupil without a lens. The objective examination shows the anterior chamber to be abnormally deep, while the deeper part of the iris trembles at every movement. By transillumination with the ophthalmoscope the lens margin is seen as a black ring (vg. 234). The fundus appears in the upright image of different magnification according as one looks at it past the edge of the lens or (with concave glass) through the lens itself. 2. Luxatio Lentis Spontanea (Spontaneous Dislocation) —The subjective and objective phenomena are the same as in ectopia, transparency of the lens being taken for granted. The origin is different, however. Two modes of origin may be assumed. First, fluidity of the vitreous, syuchysts corporis vitret. It is supposed that the same cause which thins the vitreous leads also to soften- ing of the suspensory ligament. Second, overripeness of a cata- ract. The new-formed tissue of the capsular epithelium contracts and thereby drags on the suspensory ligament adhering to the anterior capsule, which becomes loose and relaxed. An acci- dental sneeze, or vomiting, or any such shock to the body will accomplish the rest. Both cause downward displacement of the lens, because it is specifically heavier than aqueous or vitreous. After the displacement the visual disturbance due to the cataract disappears. Displacement is therefore a natural method of curing senile cataract. 3. Luxatio lentis traumatica (Displacement of the lens by mmjury), with or without injury to the external parts of the eye, may be caused by a blow or fall upon the eye. Displacement is. either complete or incomplete (subluxation). In the complete form the suspensory ligament is torn through a large segment of the circumference, and the lens sinks into the vitreous, or becomes wedged in the pupil, or dislodged into the anterior chamber, or is crowded through a wound in the sclera onto the eyeball beneath the conjunctiva, or may entirely escape through a conjunctival wound caused by the same injury. Any lens displaced from its natural bed will sooner or later become opaque. 4. Movable Lens.—Dislocation of the lens sometimes associates motility with it, irrespective of the cause. Motility may be recognized by the fact that the lens will be 360 DISEASES OF THE VITREOUS. found in various parts of the eye according to the position in which the head is held—in either the anterior chamber, the pupil, or in the vitreous. In other cases a slight tremu- lousness.may be noticed by a change of posture of the head. This condition implies some abnormal length or elasticity of the suspensory ligament, or some incomplete rup- ture in it. Obviously, the optical phenomena differ according to the location and pos- ture of the lens. The unavoidable tension on the suspensory ligament caused by this condition endangers the eye. The treatment of dislocation of the lens is restricted to the use of suitable glasses or to an operation, either iridectomy or extraction of the lens. DISEASES OF THE VITREOUS. INTRODUCTION. The corpus vitreum (v2treous body) consists of 98.6 per cent. water. If the water is pressed out of the vitreous there remains only an extremely small mass of glass-like tissue as solid constituent, which is composed of transparent fibers extending in all directions. Between these are spaces connected with each other and filled with nearly pure water, the vitreous humor. At the periphery of the vitreous are complex and peculiarly formed cells, the ameboid cells, which, according as they are adherent to the fibers or float in the free fluid, are different in form and nature. ‘The latter cells may be perceived entoptically as the ‘“‘mouches volantes.’’ The vitreous is pierced in an irregular sagittal direction by a canal about 2m. in diameter, called the central canal of the vitreous. This begins at the axis nerve sheath and ends at the posterior pole of the lens; it is provided with a lining membrane and filled with vitreous humor. In the embryonic stage there is an artery in this canal, the eterta Avaloidea ov centralis corports vitre’. At times it persists after birth, the avterta hyaloidea persistens, and is then noticeable by the ophthalmoscope as a grayish thread passing from the optic papilla to the posterior pole of the lens. The vitreous is retained in a comparatively firm membrane, the membrana hyaloidea. There arise from it near the ora serrata fine glass-like fibers that pass to the equator of the lens, and have been mentioned as the suspensory ligament ; between ora serrata and equa- tor they rest against the ciliary processes and are adherent to them. The vitreous is but little disposed to independent disease. A pathological condition in it is, therefore, always a reason to examine for disease of the uvea, particularly the ciliary body, since the vitreous is nourished from this source. On the other hand, diseases such as may be caused by an entering foreign body or by a parasite, are inclined to draw the eye as a whole into sympathetic infammation—a con- dition to be discussed later. 1. Myodesopsia (Musce Volitantes, Opacitates Corports Vitret).— It has already been mentioned that microscopic vitreous opacities are of normal occurrence. They are found at the posterior part of the vitreous 0.3 to 3.0 or 4.0 mz. in front of the retina. There is no great difficulty in seeing them in one’s own eye (/f. 79). It often happens, however, that they make themselves too evident, and on that account disturb and distress the patient. Such patients MYODESOPSIA. 361 are usually but not exclusively myopic. They describe their opacities as threads, strings of beads, flakes, spider-webs, or flies, that float about when the eye is moved, and then sink slowly through the field of vision when the eye is at rest. Since every- thing is projected into the outer world inverted (/. 70), we must assume with Helmholtz that these microscopic opacities are specific- ally lighter than the fluid in which they float, and that, therefore, when the eye is at rest they float upward. This is not altogether probable, for we know that vitreous opacities visible by the ophthal- moscope are seen to sink when the eye is at rest. I shall make no attempt to explain this contradiction. The “ flying specks” are not visible by the ophthalmoscope; there is nothing pathological to be found in the eye, and the visual acuity is normal. Treatment consists of assuring the patient that the condition is of no significance. The opacities do not disappear under this treatment, but the patient learns to overlook them. As soon as opacities are rendered visible by the ophthalmoscope, “flying specks” are no longer spoken of, but the term is—vitreous opacities. They are generally movable but may be stationary. Most commonly they appear as threads and flakes, less often as vitreous dust or membrane. The favorite location is the anterior and posterior portion of the vitreous. The center is least affected. Opacities appearing suddenly usually come from blood that has exuded from the ciliary body, papilla, or retina into the vitreous. They naturally alarm the patient exceedingly. Opacities appearing gradually may remain for a long time unnoticed; they have been spoken of as organized ameboid cells. Opacities are always a sign of disease of the choroid, the ciliary body, or of the retina, and usually, too, the only and first, or the only and last sign. For example, if hemorrhage has taken place into the vitreous and gradually disappeared, some kind of opacity generally remains. Or a lesion of the ciliary body may cloud up the anterior part of the vitreous without evidence of other disturb- ance, since the ciliary region is not accessible to the ophthalmo- scope. Visual acuity will be reduced by vitreous opacities only if they intercept luminous rays proceeding to the center of the retina. If the nature of the lesion can be made out, it has of course its influence on prognosis and treatment. If this cannot be done, such opacities must be treated by themselves. Mild salt aperients, 302 ERRORS OF REFRACTION, mercury, iodid of potassium, or a diaphoretic treatment may be tried. The result cannot be foretold. Surgical interference has been attempted by sucking out movable opacities, or cutting out stationary ones by means of a needle properly introduced. The most important point is to use the eyes as little as possible in order to dispel any choroidal inflammation that may be in its incipiency. 2. Synchysis (Fl/wdity)—lIf the fibers of the vitreous are dis- solved, the vitreous changes into a light yellow, stringy fluid. This change in condition brings of itself no disturbance and is betrayed by no special signs. The fluidity is first recognized if opacities are at the same time present, when a pronounced change in location establishes a proof that the normal confines are lacking. There are conditions, however, in which vitreous opacities can be diag- nosticated without added proof,—a high degree of myopia, spon- taneous luxation of the lens, or chronic glaucoma, for example. As cause of this fluidity we assume a chronic inflammation of the choroid or ciliary body. Consequently the treatment, if we may call it such, must begin at these tissues. This fluidity is of great significance in cataract operations, since the danger of loss of vitre- ous is in such a case very much greater than under normal cir- cumstances, Synchysis Scintillans.—In rare cases the ophthalmoscope reveals a picture that may be compared to the shower of sparks in fireworks. This depends upon the presence of minute granules and needles, partly of cholesterin and tyrosin crystals, and partly of phosphates, dispersed here and there in the fluid vitreous. If light is thrown into such a vitreous while the patient moves his eyes, some of these floating crystals reflect the light back again so that the observer sees them as luminous points. If the vitreous is not very fluid, the movement of these bodies is too small to show the phenomenon in its greatest brilliancy. The observer can then make them more apparent by rotating the mirror or by moving his own head. If the pupil is well dilated these golden points of light may be seen by focal illumination. The disease appears in advanced old age, sometimes in otherwise healthy eyes, sometimes in connection with vitreous opacities. In one case of this latter kind I found V=-*. In pure synchysis scintillans normal vision is the rule. ; ERRORS OF REFRACTION. In this and the four next sections diseases of the eye as a whole are discussed. Since refractive errors have already been treated from the standpoint of physiological optics (f. 28 e¢ seg.), they are spoken of here only as. they produce clinical signs and symptoms. HYPEROPIA. 363 I. HYPEROPIA (FarsicHTepness), H. Complaints of farsightedness are various. Many patients seek aid because, after a period of reading and writing, the letters run into one another, and are so confusing as to become illegible. The patients must stop to rub their eyes; but the same trouble comes anew and is intensified by burning, pressure on the eyes, or even headache; these necessary interruptions occur more frequently until the book or work is laid aside. Others complain chiefly of headache, and say that the family physician sent them because he thought that this headache was due to the eyes. Such troubles are called “ accommodative asthenopia.’' They arise from exhaus- tion of the muscle of accommodation, which persists in continued contraction even if the hyperope tries to look at distant objects. If now this hyperope uses his eyes for a near point—reads or writes, for example,—there is demanded of his muscle of accommodation a further contraction, which, this having already approached the maximum, is greater than can be continuously maintained. Indis- tinct vision will be added to the feeling of strain. Asthenopia and indistinct vision appear in many cases earlier than might be expected from what is said above, because the rela- tive range of accommodation ( f. 80 ef seg.) is no longer extensive enough. For example, a person twenty years old with 2.0 D of hyperopia would be able to work (with one eye) at 33 cm. distance without discomfort, since in this case he uses 2 + 3 = 5 Diopters, that is, only one-half of his range of accommodation of zo.o D. But with an accommodative act of 5.0 D there is associated a con- vergence only to a point a m. = 20 cm, distant. Consequently, in that accommodative act of 5.0 D, 2.0 D belong to the positive interval of accommodation which are applied to convergence at a m. Both eyes are fit for use, however, only if the positive interval of the accommodation applied (to convergence at —~ 17.) is considerably greater than 2.0 D. If this is not the case, the patient can avoid asthenopia in two ways: He may give up short dioptric adjustment, and be content with binocular vision while seeing everything with circles of diffusion; or the necessity for 1 There is a muscular asthenopia that produces the same symptoms (/. 368) ; anda conjunctival (f. 783), a nervous (g. v.) or retinal (. 707) asthenopia. 364 y ERRORS OF REFRACTION. accurate vision may predominate, and accurate dioptric adjustment will be obtained, but with deviation of one eye inward, that is, with sacrifice of binocular vision. Since the second way is often (unconsciously) chosen by the patient, hyperopia becomes one of the most common causes of internal squint (g. v.). It has been said that complaints about farsightedness are various. It sometimes hap- pens that the complaint is made, not of farsightedness but of nearsightedness. The patient holds his book or other objects close to his eyes. The explanation is simple. If the hyperopia is pronounced, the range of accommodation is not great enough to neutral- ize it and to adjust vision for a near point at the same time. The patient, therefore, gives up any attempt at exact dioptric adjustment, and prefers to replace it by enlarge- ment of the visual angle. By bringing the object close to his eye this visual angle increases more rapidly than do the circles of diffusion, and the pupils become so con- tracted that the latter dioptric error is somewhat minimized. It happens also that the symptoms do not refer at all to vision, but to burning in the eyes and to their sticking together, all of which is apparently explainable by the inflamed condition of the conjunctiva and lids. The usual treatment for such trouble is, however, futile, because a hyperopia or an astigmatism is at the bottom of it. Donders insisted on examining the refractive condition in every disease of the eye, a step not always taken nowadays by the practising ophthalmologist, but the experienced observer will never neglect such an examination if he finds that a conjunctival or palpebral irritation resists ordinary treatment. The distress from hyperopia drives the patient, who has been far- sighted from his youth, to the physician, at different ages. This depends on several circumstances—the degree of hyperopia first of all. Slight hyperopia up to 2.0 D will be tolerated longer than moderate hyperopia, 2.0 D to 5.0 D, or than pronounced hyperopia of more than 5.0 D. The range of accommodation present, that is, the age of the patient, is the next important factor. The third is the occupation of the individual; the tiller of the soil is less troubled by his hyperopia than the clerk, the seamstress, or the delicate artisan. Finally comes the general health; those who have tolerated their hyperopia without complaint become asthen- opic after an exhausting illness. Anatomy.—It has been said that hyperopia depends upon the shape of the eyeball. The hyperopic eye is smaller than normal in all diameters; it may therefore be considered an incompletely developed organ. The sclera is flat near the cornea, sharply curved near the equator. The anterior chamber is shallow. The visual axis cuts the cornea at a point lying relatively near the nasal side of the center of the cornea; the angle gamma (p. 84) is large, about 7°. Since the position of the two eyes is estimated rather accord- ANATOMY. 3605 ing to the direction of the corneal apices than to that of the visual axes, two eyes with a large angle gamma give us the impression of divergence. The sclera is thick and consequently pure white, in contrast to the bluish appearance of the sclera in a myopic eye. Although a skilled observer may make a guess at hyperopia from these signs alone, the diagnosis must be supported by the objec- tive (¢. 725) and subjective (f. 37) examinations, while the visual acuity can be estimated at the same time. It is a regular result to find that pronounced hyperopia is associated with a reduced visual acuity. The reason lies in the corneal astigmatism, which of itself characterizes the hyperopic eye as incompletely developed. The range of accommodation in pronounced hyperopia may be less than the normal, in consequence of insufficient development of the ciliary muscle; and in the same way the range of movement (ex- cursion) of the two eyes may suffer by faulty development of the eye-muscles, After measuring the visual acuity and hyperopia of each eye separately, the two eyes together should be tested. It will often be found that the manifest hyperopia in two eyes is 0.5, 0.75, or even 7.0 D greater than in each eye alone. The result of the test of both eyes together indicates the glasses to be worn. In myopia also there is found at times a weaker refractive condition, that is, a lower degree of myopia when both eyes are used than with one eye. How can that be ex- plained? Many think that the refractive condition found in one eye alone is the correct one, and that the acceptance of stronger convex or weaker concave lenses at the test with both eyes together rests on an error which is counterbalanced by greater visual acuity of both eyes together contrasted with the lesser visual acuity of a single eye. Others think that the refractive condition found in both eyes together is the correct one, and that the weaker hyperopia or the stronger myopia of the test with one eye alone is confused by a spasm of accommodation. Neither of these views seems to me to settle the question. Another strange fact is the following. It not seldom happens that a hyperope, jn spite of a range of accommodation greater than his hyperopia, and in spite of the closure of one eye, sees with the other eye distant objects very poorly without a convex lens. One would suppose that a hyperope with 2.0 D of hyperopia and 5.0 D range of accom- modation would always be able with one eye to neutralize his 2.0 D of hyperopia by a corresponding effort al accommodation. Why is this not possible for many such hyper- opes? This question is answered by some authorities as follows: When a child has learned to use his eye—that is, in his earliest years—he has a range of accommodation of about 20.0 D. If the child is hyperopic, he is accustomed, when looking at distant objects, to contract his ciliary muscle just enough to neutralize his hyperopia. The degree of contraction necessary for this is said to be exercised instinctively or even against the will, the whole life long, whenever a distant object is looked at. Accord- ingly the entire hyperopia is said to remain latent during life just as it was in youth, 366 ERRORS OF REFRACTION. when the range of accommodation remains unchanged. This cannot be the case, how- ever. Since the range of accommodation does, on the contrary, decrease from year to year (/. 45), the dioptric result of such an unchanged muscular contraction must, in a corresponding degree, decrease ; in other words, only a portion of the total hyperopia is latent, another portion, increasing with years, is manifest. In old age, when the range of accommodation has noticeably decreased, the contraction of the ciliary muscle pro- duces no result worth mentioning, and consequently the entire hyperopia becomes manifest. Undoubtedly the idea here developed is the correct one, but it does not exhaust the subject. As a matter of fact, it is not true that every twenty-year-old hyperope has one- half of his hyperopia latent, the other half manifest. There are plenty of hyperopes who, either with or without the neutralizing convex lens, can adjust their eyes for distant vision; their hyperopia is therefore ‘‘ facz/tative.’’ In others, even in the twentieth year, the entire, or nearly the entire hyperopia is latent. In still others, even in early youth, the entire or nearly the entire hyperopia is manifest. This is all easily explained if we consider that the impulse of the will is not alone determined by what has become habit in early life, but may also be modified later in life by the necessities of occupation and the activity of the muscle itself. Treatment.—A cure of hyperopia by art is impossible. Nature is able, however, to change a young, hyperopic eye into an emme- tropic or even into a myopic eye, in the course of the body’s development. This is not the case in the adult. Treatment must therefore be confined to overcoming the complaints of the patient by suitable lenses. But not every hyperope has symptoms. Young persons with slight hyperopia (up to 2.0 2) can usually see well both near and far objects. They need no treatment. Not until the range of accommodation decreases is asthenopia added to slight hyperopia. Such cases are aided by suitable reading glasses. Until the fortieth or forty-fifth year those glasses which just neu- tralize the hyperopia, will, as a rule, suffice. Beyond the forty-fifth year reading glasses must replace the diminished range of accom- modation, and must therefore be the stronger the older the patient. It is a good rule that the patient should read with his glasses at the usual distance, without calling into play any more than two- thirds of his range of accommodation. For example,a man of fifty years with hyperopia of 2.0 D is accustomed to read his news- paper at 30 cm. distance; he has at that age a range of accommo- dation of 2.5 D. To adjust his eyes for 30 cm. the refractive strength of his eyes at rest must be increased by 2 + = 5.33 D. But with this increase his accommodative mechanism can only take part to the extent of 4 of 2.5 D = 1.75 D (in round numbers). The balance, 5.3 eee = 3.5 D (in round numbers) must be supplied by glasses. MYOPIA. 367 In many cases, especially of moderate (2.0 to 5.0 D), and strong (over 5.0 D) hyperopia, vision is indistinct for distance with both eyes together, either because the range of accommodation is not extensive enough to adjust the eye for parallel rays—adsolute hyperopia, or because such an extensive contraction of the accom- modative muscle prevents a parallelism of the visual axes (/. 79). In this case the patient must wear glasses continuously. If there is presbyopia as well, he must have two pairs of glasses, neutraliz- ing lenses for distant, and stronger ones for near objects. In ordering glasses it must be stated that the distance of each lens from the other equals the pupillary distance, for otherwise an arti- ficial “muscular asthenopia” (f. 368) will result. The stronger the lenses, the greater is the prismatic effect, and therefore the more significance has the distance of the lenses from each other. It takes a long time for some persons to get accustomed to the inconveniences of glasses— the dazzling, the pressure on the nose and behind the ears, and the distortion of objects to one side. This last may be somewhat avoided by using biconvex and biconcave lenses, the so-called meniscus glass, which, according as the convexity 0 eas : : Fic. 135.—(a) CoLiect- (Fig. 135, 2) or the concavity (Fig. 735, 4) is the two, (2) Disesxsinc stronger, acts as a collecting or dispersing lens. Such lenses are called ‘ periscopic,” because sharp retinal images are formed even if lens and eye are not exactly centered. 3 a II. MYOPIA (SHortsiGHTEDNESS), M. Symptoms.—Slight myopia up to 2.0 /) is often tolerated with- out complaint or even suspicion. An accidental examination may be the first means of discovering the shortsightedness, and of show- ing the patient the treasures of nature and art that may have been lost to him. In moderate myopia, 2.0 D to 7.0 D, the visual disturbance is so noticeable that the patient himself must see how defective he is in comparison to his fellowmen. He applies therefore to the physi- cian with the complaint that he sees poorly, or that he needs glasses because he is shortsighted. In other cases it is pain, photophobia, 368 ERRORS OF REFRACTION. and inability to work for which he seeks aid. These symptoms depend partly upon muscular asthenopia, a painful exhaustion of both internal recti. The myope brings everything that he wishes to see distinctly so close to his eyes that it lies at, or even within, his far-point distance. He therefore makes such great demands upon convergence that even normal eyes could not stand such a continuous strain. It happens, moreover, that convergence is very difficult for axis-myopic eyes, on various grounds: First, because of the disproportion between the required accommodation and the convergence (see Causes of Concomitant Squint); second, because of the length of the eyeball, which renders all movements, espe- cially that for convergence, difficult, since long eyeballs would naturally lie with their long axes in the direction of the orbits, which would bring them distinctly divergent. Other cases come to the physician on account of ‘‘ flying specks ;” the myopic eye is to some extent in the condition in which it would be artificially placed if one wished to examine himself for entoptic opacities. Therefore, in many myopes, this seeing of specks ceases when the more diffuse illumination of the retina is changed to sharp images on the retina by concave lenses. In pronounced myopia, from 7.0 D upward, there are symptoms that are partly dependent upon the refractive error itself, and are partly the direct consequence of it. One direct result is the reduced visual acuity, which cannot be improved even by neutraliz- ing lenses. The posterior nodal point of the combined system— eye plus concave lens—lies nearer to the retina than it does in the eye alone; consequently external objects appear under a visual angle, smaller in proportion as the neutralizing lens is stronger, that is, the higher the myopia the smaller the visual angle. But a more important factor is the reduction of visual acuity as a consequence of the stretching of the retina’ and impair- ment of the macula lutea. The appearance of macular changes is often first noticed by the patient as distortion of images, metamor- phopsia, Other occasional symptoms of pronounced myopia may be mentioned, such as the light phenomena or photopsia, disturb- ances of light perception, and dark spots in the field of vision. 1 In a stretched retina the individual optic-nerve cells lie further apart than normal; consequently a retinal image must be larger than normal, in order to cover a sufficient number of these cells. ANATOMY. 369 Anatomy.—The shortsighted eye is enlarged, generally from before backward, less often in all directions. An enlargement of the latter kind is called buphthalmos, An enlarged eye protrudes from the eyeball, and is less movable than the emmetropic or the small, hyperopic eye. An eye enlarged only from before backward is egg-shaped, and may often be recognized in the individual (p~. 30). Donders has demonstrated an increase in the diameter of the eyeball as great as 33 wez., Arlt even to 37 mz., the normal length from corneal apex to posterior surface of sclera being 24.3 mm. At times only the region of the posterior pole bulges out, sclerectasia posterior ; the form of the eyeball is then obviously irregular. Another peculiarity lies inthe fact thatthe angle between visual line and axis passing through the corneal apex (angle gamma) is small or even negative, that_is, that the visual line (and visual axis) passes through the temporal side of the cornea. This condi- tion may simulate convergent squint. The diameter of the pupil in myopia is said to be on the average greater than in other refractive conditions, although this statement has been recently disputed. The lens lies deeper than in emmetropia or hyperopia, as may be recognized by the depth of the anterior chamber, and occasion- ally by tremulousness of the iris. The sclera of the myopic eye is thin, often no thicker than paper at the bulging posterior pole. The vascular coat beneath may shimmer through a thin sclera, so that the “ white of the eye” often appears bluish-white in a myopic person. The ciliary muscle is differently constructed than it is in emme- tropia or hyperopia. It consists almost exclusively of meridional muscular fibers (Bruecke’s muscle, /ig. 94, p. 266), which form a powerful band extending much further backward than normal. In the choroid there are atrophic areas, especially abundant in the immediate neighborhood of the optic nerve, sclero-choroiditis pos- terior (staphyloma posticum,' conus), less frequently at the macula lutea, and occasionally at other places at random, chororditis ais- seminata. The changes in the choroid can be seen with the oph- thalmoscope during life. 1 The name really refers to the bulging of the sclera, but is also used to describe the atrophic areas of the choroid. Staphyloma posticum is, moreover, not restricted to myopic eyes, but is seen, though less frequently, in emmetropic and hyperopic eyes. 24 370 ERRORS OF REFRACTION. The illustrations, igs. 136 and 137, show a sickle-shaped and a cone-shaped staphyloma posticum at the temporal side of the optic disc. In the latter there is a sickle-shaped, white portion sharply demarcated from a cone-shaped, black-spotted portion. Within the area of the pure white crescent, the choroid and pigment epithelium have completely disappeared and the sclera is quite exposed. As it develops, the staphyloma gradually involves the nasal side of the disc, until the crescent becomes a circle. Another common sign in myopia is an egg-shaped pupil, with the long diameter perpendicular. This oval appearance probably depends upon certain anatomical changes,—a contraction of the optic nerve papilla (/zg. 738) and the choroid toward the temporal side. Fic. 136.—SiCKLE-SHAPED STAPHYLOMA Posticum, Upricnt Imace. (After Jaeger.) The vitreous is fluid, and there are floating in it a few fibers and flakes which may be recognized as vitreous opacities with proper magnification in the ophthalmoscope. At times the vitreous is separated from the posterior pole by a layer of fluid, posterior de- tachment of the vitreous (Fig. 138). The vitreous may also be de- tached from the lens in front, anterior detachment of the vitreous (Fig. 738). The optic nerve sheath is reddened, neuritis myopum. The intra- membranous space about the optic papilla is noticeably widened (fag. 138). The retinal vessels have a somewhat emore direct COURSE. a7 1 course, due to the tension of the retina. In the area of a staphy- loma the pigment epithelium and the layer of rods and cones may have disappeared, and a dark spot (scotoma) in the visual field will correspond to such an atrophic retinal area. And finally, retinal hemorrhages and retinal prolapses (f. 375) may be mentioned as results of pronounced myopia. Course.—The anatomical changes just enumerated are not pres- ent in every case of myopia. They develop, however, during the course of years in which slight myopia is progressing into pro- nounced myopia. This point is the most important in the discus- sion of myopia, its tendency to progress. This is strongest from Fic. 137.—Cone-SHAPED STAPHYLOMA Posticum, UrricutT Imace. (A/ter Jaeger.) puberty to about the twenty-second year. Fortunately, the ten- dency ceases at this period in most cases; it becomes stationary. After this, as a rule, nothing pathological can be demonstrated dur- ing life except a staphyloma posticum. Ina few cases, however, myopia continues to develop after the body has reached full matu- rity, and is therefore continuously progressive. During its increase, symptoms like pain, sensitiveness to light, and lack of strength are particularly distressing. The advance of myopia is character- ized not only by the approach of the far point, but also by the appearance, or rather the increase, of the choroidal atrophy and the other changes in the fundus. One may often recognize as a sup- 372 ERRORS OF REFRACTION. plementary condition the various stages of progressive myopia by the various colored or pigmented zones that compose the staphy- loma (Fig. 737). A sharp outline to the staphyloma indicated by a black pigment zone (Fig. 236) denotes a pause in the progression ; small blotches near the staphyloma, on the other hand, denote a continued progression of the disease. In pronounced myopia, particularly if it continues to progress, there finally result, although it may not be till advanced life, these changes in the retina above enumerated, through which complete blindness, or at least destruc- tion of direct vision (macula affection) is accomplished. Pronounced and progressive myopia is, by many ophthalmolo- gists, sharply differentiated from the relatively benignant form of myopia, which becomes stationary in adult life; the former is con- Anterior detachment of Vitreous. Postervor detachment of Vitreous. Displaced Optic Nerve papilla Broadened intermemb) SPace. Fic. 138.—A Myopic Eve. sidered an essential inflammation of the posterior pole, a sclerotico- chorotditis posterior. In favor of this view there is the fact that the malignant, progressive myopia is found among country people, and even in children, who really supply only a small proportion of the ordinary cases of myopia. (See sections on Causes and Extent.) Such a differentiation is, after all, of no practical significance, since benignant myopia may at any time change into the malignant, pro- gressive form. : Diagnosis.—The fact that an eye sees distant objects less dis- tinctly than, but near objects quite as well as, the normal eye, is the proof of the presence of myopia. To complete the diagnosis, the degree of myopia must be estimated. The objective method is given on /. 152, the subjective method on £. 37. Causes and Extent.—Myopia is a very common and wide- spread disease. Native peoples are comparatively free from it, and CAUSES AND EXTENT. 373 in that respect, at least, are “ better men” than we are. In cul- tured races, only the age of childhood is free from myopia. As soon as school-life begins, cases of myopia show themselves, and increase in number the higher in school the children advance. H. Cohn found in 5 village schools, 1.4 per cent. in 20 elementary schools, 6.7 per cent. in 2higher girls’ schools, 7.7 per cent. in 2 grammar schools, 10.3 per cent. in 2 preparatory schools, 19.7 per cent. in 2 colleges, 26.2 per cent, myopic! He found also that the degree of myopia increased with the length of the period of school. Axis-myopia has, therefore, been called school-myopia. It is intended to imply that attendance at school is the cause of myopia because dur- ing the growth and development of the general system, the eye is, at school, compelled to do too much near work. This near work, like reading and writing, acts very harm- fully. Boys who leave school when fourteen years old, to become tailors or watch- makers, continue in the new field of labor to strain the eyes with near work, but experi- ence teaches that, in spite of this fact, myopia is not so frequent among them as it is among their former comrades remaining at school. The essential connection between school work and the lengthening of the eyeball is still problematic. An assumption—unproved as yet—may help to make the matter clear: children, when reading and writing, are accustomed to bend their heads forward to bring them close to the books. In many this is due to poor visual acuity from astigma- tism or corneal opacities, but in others it is only a bad habit. The eyes are made strongly convergent, the visual plane is lowered, and the muscle of accommodation is kept tense. On account of the convergence the interni as well as the superior and inferior recti are kept tense, the obliqui and inferior recti also, by the lowering of the visual field. The other muscles are at least strained. They all press upon the eyeball and increase its in- ternal tension, while the contraction of the ciliary muscle has the same effect. The eye becomes overfilled with blood by the hyperemia from work on the one hand, and, on the other, by the fact that with the head bent forward the return of venous blood from the cranium is retarded. It may be seen that an increased internal pressure causes the eye’s envelopes to yield, although this does not explain why the eye is lengthened from before backward as the result of tension. This may be comprehended by studying the position and the necessary action of both obliqui. They surround the eye, at least when looking straight ahead, like a girdle, and must therefore press it into the shape of an egg if the 1 The statistics are from German sources.—TRANSLATOR. 2 I have just had in my care an eight-year-old boy with a myopia of 5.0 to 6.0 D, very strong for his age. In asking him about it, I discovered that he was going to two schools, the usual elementary school and an Italian night school, for his father was Italian and wished the boy to continue his native tongue. Was this cause and effect? 374 ERRORS OF REFRACTION, contraction is sufficiently strong. In looking toward the median line, this girdle-like action is less marked, but in doing this the eye is drawn forward, and consequently raised from the fat layer in the orbit, against which the recti muscles are trying to press the posterior pole; this posterior pole is therefore robbed of its support, and a bulging is made possible. Not all school children, not even all gymnasium pupils, are myopic. We must there- fore assume that some are, some are not, predisposed to myopia. We say it is con- genital. What is this congenital predisposition? Stilling deserves credit for having attracted the attention of ophthalmologists to the great differences in direction and inser- tion of the superior oblique tendon. The thickness and resistive power of the sclera differ in different individuals. There are probably personal differences in the structure of the ciliary muscles. Even supposing that a ciliary muscle consisting chiefly of meri- dional fibers relaxes the Zonula of Zinn quite as well as one supplied with circular fibers, there can be no doubt that the other mechanical effects of each, the effect upon the sclera, for example, will be quite different. The smallness of the angle gamma is also an anatomical peculiarity that, by making convergence difficult, may become a cause of myopia. Weiss suggests that a longer or shorter optic nerve may have its significance, since, if the optic nerve is short, convergence of the visual axes causes tension at the posterior pole, and aids therefore in the development of myopia. Thus we see that there are numerous reasons for supposing that the inclination to myopia lies in inherited anatomical peculiarities of the eyeball itself. Treatment.—Myopia cannot be cured, but it may be prevented, If the eye is used only for distant vision it will not become myopic (neglecting exceptional cases). Ina cultured people, however, school and a sacrifice of eyes to it cannot be avoided. The school must therefore be so arranged that the number of eyes so sacrificed does not pass the minimum. In Germany and Switzerland this arrange- ment has not up to now been satisfactorily accomplished. The rules that ought to govern house and school are the following :-— (1) The quantity of the customary daily work should be reduced, especially in the high schools. In many ofthese, upper-class students have, besides the six school hours, five to seven hours more of work at home, that is, eleven to thirteen hours of daily near work ! (2) Between hours of work at school and at home there should be suitable intermissions. (3) At home and at school the student should work only in good daylight or in good artificial light. (4) Books should be large enough, and printed in clear, well-de- fined type. (5) Students should have their work at a distance of 35 to go cm. from the eyes, with the visual plane only moderately lowered, and with a natural position of head and body. Benches and type should be properly adjusted for this purpose. The upright is TREATMENT. 375 better than the usual oblique style of writing. This perpendicular writing is particularly advised by Schubert and others. Undoubt- edly upright writing has its advantages, but the most important point is, after all, as Ritzmann observes, that the teacher should have judgment and self-denial enough to insist with an iron per- tinacity that the proper distance from the work be maintained by the students. It is the parents’ duty to see that the children avoid all reading (novels !) and writing which is not indispensable for their advance- ment in school. All these rules must be doubly enforced if myopia is already present. If myopia increases in spite of all, a long rest should be ordered, or the school should be entirely given up. The general health should be looked after, and plenty of fresh air pro- vided. To prevent the advance of myopia some recommend atropin, others the very opposite, eserin. One claims that atropin is no good, another that eserin is of like value. The advantage gained from the use of either remedy does not lie in the remedy itself, Lut in the prolonged cessation from near work. Atropin is useful and indicated when part of the myopia is apparent, and conditioned by spasm of the ciliary muscle. Such a spasm disappears only after continued and energetic application of atropin. The disadvantages of myopia can be, in part at least, neutralized by glasses. Should every myope wear glasses? No; they are often harmful and unnecessary. The following rules will generally ap- ply :-— Myopes of 2.0 D or less, who have no trouble at near work, but wish glasses for distant vision, should wear eyeglasses and not spectacles, and should be advised to use them only for distance. In myopia from 2.0 Dto 4.0 D or 5.0 D, neutralizing lenses for both near and distant work may be used, assuming that the range of accommodation is still large enough, and that the patient is young. Spectacles thus allow the book to be held at a suitable distance (go cm.), and they prevent too strong convergence. Any muscular asthenopia is at the same time combated, first by a de- mand for more powerful accommodation, and the greater call upon the muscles of convergence associated with it; second, by the greater working distance permitted, that is, by a lessened use of convergence ; and third, by placing the lenses further apart, if this seems necessary, since by having the patient look through the inner half of the lenses instead of through their center, we obtain the effect of a prism in the position of abduction ( /. 93). 376 ERRORS OF REFRACTION. In myopia from 4.0 D or 5.0 Dto 7.0 D or 8.0 D, glasses for near work must be ordered which displace the far point to about go cm., and additional eyeglasses for distant vision. Suppose there is myopia of 6.0 D, the far point then lies at only z m = 16.66 cm., which is much too near for comfortable convergence ; if the myopia is reduced by a lens of —}3.5 D so that it remains 2.5 D, the far point now lies at ss m= so cm. At this distance accommodation is not required, and only moderate convergence is necessitated. If the patient intensifies his spectacles by adding eye-glasses of —2.5 D his myopia is neutralized and distinct distant vision is made possi- ble. With myopia higher than 7.0 D to 8.0 D, the same plan may be pursued if no pathological condition within the eye prevents the use of lenses, or if the patient—which is usually the case—is doubly distressed by the lenses. In pronounced myopia it is often neces- sary to give up glasses altogether. Such a condition has induced many ophthalmic surgeons to treat pronounced myopia by extract- ing the lens. This method is still the subject of warm discussion. I have recently resorted to it. My first result was very encourag- ing; a patient had before the operation V = +, with 75.0 D— —2.0 D cyl, after the operation V = + with +27.5 D cyl. When we know that patients often refuse to wear strong concave lenses, although without a lens they may not have even “ of the normal vision, it is plain that the removal of the crystalline lens is of great advantage to the patient. It has been recently stated, by American ophthalmologists particularly, that total neu- tralization of even pronounced myopia was not only possible but even desirable; and that the patient's original repugnance to strong glasses would disappear after using them. My experience is that the glasses disappear before the repugnance does ! II. ASTIGMATISM. As. 1. REGULAR ASTIGMATISM. The normal eye is, to a very slight degree, regularly astigmatic. This can be called physiological astigmatism, so long as it causes no visual disturbances or symptoms. Such a definition must, to be sure, allow an astigmatism of 0.75 D to be at one time physio- logical, at another pathological, since in early life, so long as the REGULAR ASTIGMATISM. 377 range of accommodation is large, this slight astigmatism may cause: no disturbance, but in the thirties it may lead the patient to the physician. Astigmatism of more than z.5 D always causes disturh- ance, even in youth. In physiological astigmatism the perpendicu- lar meridian is the meridian of strongest curvature; the horizontal, that of weakest curvature. This is usually the case, too, in patho- logical astigmatism. It is seldom the reverse, that the horizontal meridian is the stronger refractive, such a case being spoken of as against the rule, astigmatismus perversus. It does, however, happen often enough that the meridians of stronger and weaker curvature are not exactly perpendicular and horizontal, but are more or less oblique. The symptoms of an astigmatic consist of reduced visual acuity or of asthenopic troubles, or of both. The reduction in visual acuity depends upon distortion of the retinal images (f. 9). The asthenopic troubles depend in part upon the effort the individual makes to neutralize his astigmatism by unequal contraction of his ciliary muscle, in part also upon the fact that he brings objects nearer to his eyes, in order to compensate for the indistinctness of these retinal images by increasing the visual angle; but in doing this he uses accommodation and convergence improperly. The increased effort necessitated by working with indistinct retinal images must be somewhat ofa factor also. Finally, there are cases in which the complaints of the patient do not immediately suggest astigmatism, but are classed by the physician among diseases of the conjunctiva (7. 97). Anatomy.—The total astigmatism of an eye depends partly upon meridian-asymmetry of the lens, partly upon meridian-asymmetry of the cornea. Corneal astigmatism being the stronger, decides the condition. In a few cases it is increased by the lenticular ‘astigmatism, but in most cases is reduced by it; astigmatism in the lens is, therefore, as a rule, the opposite of that in the cornea. Corneal astigmatism may be congenital or acquired—usually congenital in eyes highly myopic. In early life astigmatism is, in most cases, “with the rule.” In the course of years the form of the cornea may change essentially so that from adult life on, astig- matism against the rule becomes more and more common. Astig- matism is acquired after certain operations, such as cataract extractions, iridectomy and sclerotomy; some months after the operation it is less than at first, but it never entirely disappears. 378 ERRORS OF REFRACTION. Lensastigmatism—apart from any congenital meridian-asymmetry— may be due to some acquired obliquity of position (. 358), and is then particularly strong. Diagnosis.—In every estimation of hyperopia and myopia by means of lenses, astigmatism must be thought of if perfect visual acuity is not obtained with the ordinary spherical lenses. It is particularly suspicious if in the rows of letters of different sizes some letters are read correctly, others incorrectly. The character of the indistinctness of the retinal image, and the form of the letter itself, will give some clue to the refractive error. For example, if the retina is at f’’ (Fig. 72, p. 48), a small L will be recognized more easily than a large B, because in the L the perpendicular line at any rate is distinct, while the perpendicular line in the B is pro- portionally indistinct on account of the three confusing horizontal elements of the letter. The objective demonstration of astigma- tism may be made by the ophthalmoscope (/. 728), while the posi- tion of the principal meridians and the degrees of their refraction may be determined by the shadow test (/. 734). Simple corneal astigmatism may be determined by the keratoscope (f. 97) and measured by the ophthalmometer(. 98). The difference between total and corneal astigmatism as determined by keratoscope or ophthalmometer equals the lenticular astigmatism. Treatment of astigmatism consists in prescribing the proper neutralizing cylindrical lenses, with the necessary correction, of course, of any hyperopia or myopia present. If there is mixed astigmatism (/. 50), two cylinders are required, one convex and the other concave, their axes being perpendicular to each other. Instead of two plano-cylindrical lenses with their plane surfaces joined, a single glass may be used, with the cylindrical surfaces ground upon it. There is, in general, no contraindication to the use of cylindrical lenses. In spite of this, however, no ophthalmologist can escape the chagrin of seeing a patient neglect the glasses which have been selected with great care and which essentially improved the vision. If the patient is asked why he does not wear these glasses, he will answer that they make his head ache or cause vertigo. The reason for this is not always clear. Much depends upon having the axes of cylindrical lenses correspond exactly with the principal merid- ians of the eye. For this purpose test frames (zg. 739) have been arranged so that the cylindrical lenses in a separate clasp can be IRREGULAR ASTIGMATISM. 379 revolved about the rigid part of the frame, the circumference of ~ which is divided into degrees. The best position for the cylinder must be found by trial, and the position of its axis noted on the. test frame. It is always advisable carefully to see that the physi- cian’s prescription for glasses is followed by the optician in every detail of refraction, position of axes, pupillary interval, and distance from the eyes. Errors are not uncommon. Just as astigmatism may be caused by an obliquity of the crys- talline lens,so may astigmatism be neutralized by holding spherical lenses obliquely before the eyes. Myopes with astigmatism (astig- matismus myopicus compositus) are very often content with simple spherical lenses, for they have noticed by accident that they can see much better when looking obliquely through their glasses, and they make practical use of the discovery by turning the head in one direction and the eyes in the other, thus looking obliquely through the glasses. There is another explanation for the fact that myopes are inclined Fic. 139.—Ropenstocx’s Test FRAME. to look obliquely through their glasses. In many cases the myope does not try to correct astigmatism, but to produce it, in order to acquire better visual acuity. Such amyope has too weak glasses ; the image of a distant object still falls in front of his retina, in spite of his glasses, while on the retina there is an image combined with diffusion circles. If now such a myope looks obliquely through his glasses, he produces an astigmatism in which each luminous point has an anterior and a posterior linear focus, the posterior linear focus falling (under certain conditions) exactly on the retina. Objects whose linear prolongations coincide with the direction of these linear foci are therefore seen more distinctly than if they were looked at directly through the glasses. 2. IRREGULAR ASTIGMATISM. This is understood to signify a condition of the dioptric system in which there is no image formed even by the rays of a homo- centric pencil—that is, by rays falling upon the same principal 380 ERRORS OF REFRACTION. meridian. The normal eye is irregularly astigmatic, although to a slight extent only, This may depend upon “ spherical aberration,” that is, upon the fact that luminous rays in passing through a spherical surface are united the sooner the greater the angle of incidence; in Fig. rgo angle # is greater than angle u, consequently the image 4 is nearer to the refracting surface than the image a, The flattening of the cornea at the periphery reduces the spherical aberration of the eye and makes it to some extent aplanatic, while the exclusion of the excentric incident rays by the iris accom- plishes the rest. The noticeable irregular astigmatism of a healthy eye depends upon the structure of the lens. A star does not ap- pear to us as a luminous point, but as “ star-shaped ”—that is, as a point with rays, the structure of the crystalline lens being responsi- ble for the condition. In the aphakic eye this phenomenon is not present. Irregular astigmatism of pathological nature causes reduction of visual acuity below the normal. Sul- zer assumes that the extraordinarily numerous cases of imperfect visual acuity without visible cause depend upon irregular curvature of the cor- nea. The same is true for the numer- Fic, 140.—SpuenicaL Aperration. OUus cases of regular dstigmatism in ines 4 dicul h . . : ‘The dotted tines areletiee te which perfect visual acuity cannot be obtained even after correction with cylindrical lenses—a combination of regular with irregular astig- matism. A very common cause of irregular corneal astigmatism is a corneal opacity (~. 254); an uncommon cause is keratoconus (2. 259). Irregular lenticular astigmatism is produced by opacities or by clefts in the lens, which precede genuine cataract (p. 336). There is no treatment for irregular lenticular astigmatism. Great optical success has been attained in correcting corneal astigmatism with ““stenopaic glasses” (/. 57), that is, untransparent disks having a small hole in the middle for looking through. The smallness of this hole prevents rays from being received on all but an extremely limited corneal area, the curvature of which may be considered regular; the practical use of stenopaic glasses is, however, decidedly limited by the circumstance that such a small hole admits of only an extremely restricted visual field, and of no excursional field at ANISOMETROPIA., 381 all! ‘Roth tries to overcome this drawback by using disks—“ sieve glasses ’—provided with numerous small holes of 7.4 to 2.2 mum. diameter. The visual field is not narrowed by such a disk, but only interrupted by unimportant shadows; eye-movements are not excluded, since at every change in the position of the eye another hole lies in front of the pupil, which may be used directly to look through. 3. ANISOMETROPIA., Anisometropia is the term used to indicate an inequality of the refractive condition in the two eyes. It may be present in in- numerable modifications—as myopia and hyperopia of different degree, as emmetropia in one eye, myopia or hyperopia in the other, or myopia in one eye, hyperopia in the other. If both eyes are myopic, but in different degree, the right eye has usually the greater error, since even in normal binocular vision the right eye is used for greater precision than is the left.! Occasionally anisometropia of the two eyes is associated with distinct asymmetry of the orbit, forehead, and face. How does the anisometrope see? There are three possibilities to be considered :— (z) He sees with only one eye and completely neglects the other for both near and far objects. This is the case if the visual acuity of one eye is unusually better than that of the other. This may generally be surmised from the position of the eyes, since the eye excluded from vision deviates outward. (2) The anisometrope uses his eyes alternately, that with the weaker refractive power being used for distant objects, the other with the greater refractive power for near objects. In this condi- tion there may be such a correct position of the eyes and such good vision that the patient himself is not aware of any defect, or is, on the contrary, rather proud of an extensive range of accom- modation (when the eye with greater refractive power is myopic). (3) The anisometrope fuses the two retinal images, and has, therefore, binocular vision in the narrower sense of the word. He can do this, even though the retinal images are unequally distinct, or perhaps even of different size. If vision is concerned with an object lying within the range of accommodation of both eyes, exact 1 Other investigators find greater myopia quite as frequently in the left eye as in the right. 382 ERRORS OF REFRACTION. dioptric adjustment in both eyes may be attained by accommodat- ing unequally for each eye. The majority of ophthalmologists, Donders included, consider this impossible. On the other hand, a minority, with v. Graefe,’ are of the opinion that the association of both eyes in an exactly equal accommodation may be to a slight degree dissolved by a natural or artificial difference in refraction. I think that I have offered a proof that unequal accommodation is possible within cer- tain limits and actually does occur in anisometropia, although my proof has been attacked by Greeff, and particularly by Hess. In spite of that I cannot admit that my view has been refuted, and I hope to be able later to contradict the objections raised against it. I had a short time ago a case that seemed to me to demonstrate unequal accommoda- tion in a manner quite free from objections. A woman consulted me on account of asthenopic troubles. The shadow-test disclosed compound hyperopic astigmatism; the test letters showed this condition only in the left eye, while the right eye accepted a cylindrical but no spherical lens. I concluded that in the right and more acute eye there was latent hyperopia, but in the left eye manifest hyperopia as well. Two doses of homatropin proved that my assumption was correct, for now not only the left but the right eye also accepted a spherical lens—on the right a lens of +3.0 D. If this clearly indicated unequal accommodation, it became a certainty when I had occasion eight days later to test the glasses prescribed by me. I examined the patient again with the follow- ing result: while the right eye, with a simple cylindrical lens, was fixing letters (D = 4) at ¢ m., the refractive condition of the left eye was determined by skiascopy ; then the test letters were removed, and as the right eye was gazing into space, the left eye was again tested by skiascopy; in both cases the refractive condition of the left eye remained the same, that is, unchanged, while the refractive condition of the right eye had varied to the extent of 3.0 D. In choosing glasses we must consider which of the three possi- bilities is present. In (z) no attention need be paid to the weaker and neglected eye, and only the refractive error of the better eye need be neutralized by the rules already given. In (2) some cases need no glasses at all, at least so long as the range of accom- modation is not too small. If, for example, the left eye is emme- tropic and the right myopic 4.0 D, and if the eyes are used alter- nately, the patient can cover as much ground with an accommoda- tive range of 4.0 D as can a normal pair of eyes with an accommo- dative range of 8.0 D, that is, from 00 to 4% wm. = 12,5 cm. in front of the eye. Ifthe range of accommodation of this patient sinks to 2.0 D, he will see distinctly with the left eye from oo to % mm, = 50 cm., and with the right eye from } 7. to 4m, that is, from 25 to 77 cm., but between 50 cw. and 25 cm. he will not see distinctly with either eye; a convex lens of 2.0 Din front of the left eye 1 Symptomenlehre der Augenmuskellahmungen. Berlin, 1867. Seite 63. AMBLYOPIA EX ANOPSIA—HEMERALOPIA. 383 would be of service in this case. In (3) the anisometropia should be totally neutralized. If the patient is young and hindered by no latent squint, he will grow accustomed to the glasses after a period of discomfort. Equally strong accommodation on both sides is only desirable in getting accustomed to the neutralizing glasses. If the total correction is not borne, a partial correction of the aniso- metropia must suffice, or the anisometropia left quite uncorrected. I have never had an example of this last. AMBLYOPIA AND AMAUROSIS. Dulness or weakness of vision and blindness are pathological signs with which we are often met. We are accustomed, however, to use the terms amblyopia and amaurosis in a narrower sense, also, for diseases whose anatomical characteristics are either quite un- known or at least productive of no demonstrable changes in the eye itself. 1. AMBLYOPIA WITHOUT LESION. (a) Amblyopia ex Anopsia (Weaksightedness from Disuse).—If a child hitherto healthy begins to squint, he will see double. To obviate this distressing symptom the child learns by a mental act to suppress in the squinting eye the image of the object fixed by the other eye. If this suppression is practised for weeks, months, or years, there results a permanent change in the nervous apparatus of the visual organ, which is recognized as a greater or less reduc- tion in visual acuity, and is called weaksightedness from disuse— amblyopia ex anopsia. It is evident from the above that weaksightedness from disuse does not develop in adults beginning to squint (from a muscular paralysis, perhaps); the nervous apparatus in the latter case is at complete maturity, and the suppression is therefore unsuccessful. It is quite as evident that weaksightedness from disuse does not result in children whose eyes are prevented from seeing by some optical hindrance (corneal opacities or cataract) ; suppression is here not called for; the eyes rather seek to make use of all light pene- trating to the retina. If, on the contrary, an eye is optically of little value, squint almost always results and there is an associated amblyopia of that eye. The development of amblyopia may be prevented by daily com- pelling the squinting eye to perform independent vision, even if only for half an hour, the other eye being bandaged. It must be confessed that this method soon becomes tedious to the patient and the parents, but even an amblyopia already existing may at times be improved by such exercise to the weak eye. (6) Hemeralopia (ighiblindness, night-shadows, pp. 53 et seq.) 384 AMBLYOPIA AND AMAUROSIS. indicates a reduced sensitiveness of the visual organ to a weak stimulation of light. The result of this condition is such that acute- ness of vision and color-sense begin to decline, or are quite obliter- ated in an illumination that permits normal vision toa healthy eye. Nightblindness is either a symptom, and as such has been already mentioned in retinitis pigmentosa, chororetinitis syphilitica, choroid- itis, and prolapse of the retina, or it is a disease of itself. It may be congenital, and is then a rare condition perpetuated unchanged during life; it is, however, oftener acquired and may then be cured in a few weeks, this, as an acute form, being distinguished from the chronic, congenital condition. Nightblindness may be due to two causes :— (1) Overstimulation (blinding) to the eye. (2) Lack of proper nourishment to the general body. If both conditions occur, the disease is more certain to show itself. For example, “ night-shadows”’ are nearly endemic at Easter among Russians of the lower class; these people are greatly impoverished by the rigor of the northern winter and by the severe seven weeks’ religious fast, but they must at that time begin out- door work again and thus expose themselves to the blinding rays of thespring sun. Sailors, after a long cruise, are similarly affected ; the plain sea diet with no fresh meat and vegetables reduces the bodily strength and leads probably to scorbutus; the reflection of the sun’s rays from the sea’s surface is dazzling. Prolonged marches on plains of snow lit by a bright sun (Alpine tours) may cause nightblindness. It must be observed, however, that in this “ snow- blindness” there is not only hemeralopia, but also, and principally, a genuine inflammation of the anterior segment of the eye—conjunc- tiva, cornea, and iris—which is produced through the ultra-violet “chemical” rays of the light reflected from the snow. Since hemeralopia is a symptom of certain retinal diseases, it may justly be assumed that “‘ nightblindness without lesion ”’ is still situated in the retina. The nature of the disease may be imagined as a disturbance of equilibrium between production and con- sumption of visual material. Many ophthalmologists consider dazzling and poor nourishment insufficient to cause nightblindness. They think, rather, that these conditions only incline a person to sicken, but that the essential cause of the disease consists of a miasm (only suspected, to be sure, but not yet demonstrated). Treatment consists— (1) In withdrawal from all bright light by confinement in a dark- ened room or by the use of protecting glasses. COLOR-BLINDNESS—-NERVOUS ASTHENOPIA. 385 (2) In improvement of the general health by proper nourishment, fresh meat, and vegetables ; if the patient wishes medicine, cod-liver oil may be prescribed; it tastes like medicine and is a good food. (c) Color-blindness (ff. 57 ¢¢ seg.)—There is partial or com- plete color-blindness. Complete color-blindness is the inability to distinguish qualitative (color) differences, the spectrum being rec- ognized only as light or dark. Partial color-blindness is the con- dition in which only some of the spectrum waves are recognized as specific (color) sensations. By far the most common form of par- tial color-blindness is Daltonism,' or red blindness. The majority of cases are associated with green blindness. The red-green blind person, or the one whose blindness alternates—either red or green— sees the spectrum in two colors, yellow and blue. What the healthy person perceives as red, orange, yellow, and green, he perceives as different shades of yellow; what the healthy person perceives as blue-green, appears to the latter as colorless, the rest of the spectrum being blue. In a corresponding way the blue-blind person is at the same time yellow-blind; the spectrum is for him composed of only two colors, green and red. Blue-yellow blindness is extraor- dinarily rare. Complete color-blindness implies that no colors at all are seen in the spectrum, and that the entire spectrum appears to be composed of lines of brighter or darker grays. Color-blindness, complete or partial, may be either congenital or acquired. If acquired, it is a pathological sign that in the majority of cases is to be referred to a disease of the optic nerve, less fre- quently to disease of the inner retinal layers or of the brain. Con- genital color blindness is a condition about the cause of which nothing is known. It is commoner in men than in women, and has a tendency to jump over a generation in its inheritance. (2) Nervous asthenopia (Wilbrand) shows itself in many forms. In school children it causes complaint of haziness, dimness of let- ters and lines, occasional double vision, blinding by lamp or even daylight, lacrimation, pain in the forehead and eyes. In examina- ‘ . . : 2 ao, tion we find reduction of visual acuity to —-, or even ge and con- centric narrowing of the visual field growing more prominent as 1 Dalton, an English physicist, suffered from red blindness and was the first (in 1798) to describe the condition accurately. * An examination of the various theories of light and color sensations is not within the plan of this book. 25 386 AMBLYOPIA AND AMAUROSIS. the perimeter is used, a fact explainable as a phenomenon of ex- haustion. This restriction is peculiar in that it appears of varying magnitude according to the size of the test object used. This ex- plains the fact that such children are not in the least hindered in finding their way about the room, a condition that obviously must be noticed in a visual field absolutely narrowed, as in atrophy of the optic nerve, for example. Color sense is normal and the fundus unaffected. The examination of the body in general shows hyper- esthesia and anesthesia of the skin in various localities. A similar condition is found in adult neurasthenics, but in their cases the complaints of eye pain and dazzling are more prominent. The visual acuity is normal; narrowing of the field for white and often for colors can be demonstrated. In pronounced hysteria’ the condition is very marked; Kopiopia hysterica is the name given to it. Besides pain, dazzling, reduction of visual acuity, and narrow- ing of the visual field, usually in one eye, there may be spasm. of the lid, weakness of the ciliary muscle, eye-muscles, and of the levator; greater disturbance of color sense, and, finally, a host of sensible and motor paralyses and pareses in all regions of the body. Before the diagnosis of nervous asthenopia is made from the foregoing subjective symptoms, we must see whether the patho- logical condition does not depend upon some refractive error, such as hyperopia or astigmatism, or upon some conjunctival trouble or weakness of the internal recti. The ophthalmoscopic evidence also must be negative.” In cases where there is a doubt whether reduced vision with concentric narrowing of the field and disturbance of color-sense is due to hysteria or to a deep lesion of the optic nerve, the further course of the disease will explain matters; optic-nerve atrophy leads continuously to the bad; hysterical amblyopia, on the other hand, arises suddenly, remains for some time unchanged, and dis- appears as suddenly as it arose. Opinions differ as to the localization of the disturbances. Knies thinks that they are peripheral, about at the place where the nerves pass through narrow, bony canals and are 1 From 7 iorépa, the uterus. It was once the belief that the chameleon-like disease called hysteria was seen only in women and had its origin in the uterus. It is now known that men, too, are similarly affected. 2 Bernhardt finds that in many cases of nervous asthenopia there is really a slight paleness of the temporal half of the optic disc. SIMULATION, MALINGERING. 387 easily compressed by dilatation of the blood-vessels. Most authorities think that they are central, that is, located in the cerebral cortex. There is a particular tendency to such diseased conditions among hereditary sufferers—persons whose parents have been victims of nervous diseases. As immediate causes may be named over-exer- tion at school or in the struggle for existence, injuries (traumatic neuroses), often of a trifling nature, and diseases of the female geni- tal organs (Kopiopia hysterica). Treatment must be chiefly— (1) Relief to the eyes by rest from work and by the use of dark glasses; these may even restore normal vision for a moment; it may then be assumed that the reduced visual acuity was due to dazzling. (2) Improvement in physique by wet dressings, massage, open- air exercise, and good food. : (3) By suggestion in the form of simple medicines and metallo- and electro-therapy. APPENDIX. Simulation, Malingering.—It occasionally happens that a per- son declares that he is blind or weaksighted in one eye; if this eye is normal, we speak of simulation; if the eye is really ambylopic and the symptoms merely exaggerated, we speak of aggravation. Simulation and aggravation are not really diseases, but as the oph- thalmologist is often concerned with them, they must be briefly considered. Simulants (malingerers) state as a rule that only one eye is weak or blind, since it is easier to play that part than it is to pretend to be weaksighted or blind in both eyes. Their reason for simulation is the wish to escape military service or to get damages on account of an injury from some corporation or insurance company; other simulants, particularly hysterical women, have only the impulse to make themselves interesting. In some cases, especially in chil- dren, no rational cause can be discovered. The physician’s task is to unmask the simulant. Many ingen- ious devices have been used, all depending upon the fact that the normal individual does not, in his visual perceptions, take into account whether they come from his right or from his left eye, or from both. For example, if a pencil is held between a book and 388 APPENDIX. the eyes, the pencil does not obscure the same word or part of it from the right eye as it does from the left ; reading can go on, then, uninterruptedly, the reader being unconscious of which word is seen by the right eye alone, which by the left alone, and which by both eyes together. An individual who claims to be blind or weak- sighted in one eye, is proved to be simulating if he can read unin- terruptedly under the condition just given. The size of the type read is at the same time a test of the visual acuity of the eye assumed to be blind or amblyopic. Another trap—place before the eye asserted to be normal a strong convex lens, say of zo.0 D. Assuming it to be emmetropic, it can then read fine type at {/, 7. from the lens at the most. Now, appearing to pay no attention to the eye asserted to be blind or weak, the test-type is gradually removed beyond the focal distance of the convex lens. If the person is still able to read in spite of this, it is evident that he reads with the blind or amblyopic eye! A third method depends upon the production of double images by prisms, for which certain precautionary measures must be adopted. Simulants suppose that the acknowledgment of double images is equivalent to the confession of binocular vision; they therefore persistently deny double images. It consequently be- comes necessary to convince the person examined that he can see double with only one eye. For this purpose the eye asserted to be blind is covered, and in front of the other eye there is placed a prism so adjusted that it covers only one-half the pupil, the other half being left uncovered. Any object fixed will now appear double, since rays refracted by the prisma produce one retinal image lying beside the image produced by the rays entering the pupil directly. After the person has acknowledged the double images and described their location, the cover of the (asserted) blind eye is as if by chancé withdrawn, the prisma being at the same time advanced so that it now covers the entire pupil of the sound eye. If the person now acknowledges the appearance of double images, it is a proof that he can see with each eye. Still another method depends on the fact that colored letters on a dark ground cannot be seen through glasses of the complement- ary colors,—green-blue letters, for example, are invisible if looked at through red glasses, because the green-blue rays proceeding from the letters are not transmitted through the red glass. If now green-blue test letters on a dark ground are offered to the person INTOXICATIONS—AMBLYOPIA. 3 89 for reading while he wears a green glass over the (asserted) blind eye and a red glass over the sound eye, the sound eye will be pre- vented from seeing the letters, and if the person says he recognizes and reads the letters under these circumstances, it can be done only by the (asserted) blind eye! The size of the letters read is at the same time a test of the visual acuity. 2. INTOXICATIONS. (a) Uremic Amaurosis.—In many diseases of the kidneys, particularly in scarlet fever nephritis and in the nephritis of preg- nant and puerperal women, uremia may result, a pathological condition dependent upon supersaturation of the blood with urinary ingredients. Uremia shows itself in mild cases by headache, dul- ness, oppression, nausea, and vomiting, and by twitchings and tonic contractions of the face and limbs; in severe cases there are also spasms and coma. An occasional result of uremia is uremic amaurosis, that is, total blindness of both eyes, appearing some- times suddenly, sometimes after a day or so of diminished visual acuity. Blindness may be so complete that light cannot be dis- tinguished from dark, or even that the pupils no longer react to light stimulation. If the patient survives an attack of uremia, the blindness may completely disappear in a few days. Since the ophthalmoscopic examination shows a normal fundus, this amau- rosis depends obviously upon some disturbance in the brain. In cases (rare, indeed) where even the pupillary reflex is lost, we must assume that not only is the center for optical perception, but also the region of the corpora quadrigemina, in which lies the center for reflex pupillary action (/zg. 773, p. 305), diseased. (6) Diabetic Amblyopia.—The numerous diseases of the eyes resulting from diabetes include also an amaurosis without lesion. This may lead the patient to the physician before the usual symp- toms—loss of flesh, muscular weakness, great hunger and thirst, increased excretion of urine—have made it clear that there is a deep-seated disease. Nothing positive is known of the cause of diabetic amaurosis, but small hemorrhages or fatty degeneration in the optic nerve have been suspected. (c) Blindness from Malarial Fever and Quinin.—Cases of malarial fever have been reported in which bilateral blindness oc- curred every time at the beginning of the febrile attack, and disap- peared with the critical sweat, after six to eight hours. The remedy 390 APPENDIX. for malaria, quinin, proved itself to be effective against this ambly- opia also. Strange to say, other cases have been reported in which large doses of quinin have produced bilateral amblyopia. An analogous effect of quinin upon the auditory apparatus is a well- known phenomenon, a small dose, even one gram, being enough to produce ringing in the ears and deafness. A reduction of visual acuity by quinin (quinin amblyopia) is not uncommon. In rare cases this amblyopia may go on to complete blindness. The retinal vessels are then seen to be narrow, the discs pale. It may be assumed that quinin amaurosis depends upon ischemia of the retina, 3. WEAKSIGHTEDNESS AS A SIGN OF CEREBRAL DISEASE, (a2) Hemianopsia.—Semi-blindness denotes the obliteration of half the visual field in both eyes, arising from a localized cause common for both eyes, If this obliterated half of the field is the Fic. 141.—Homonymous HemsAnopsiA, RESULTING FROM UNILATERAL CEREBRAL HeMoRRHAGE. The darkened areas indicate the obliterations, The normal areas remaining are contracted. same in both eyes, for example, that half of the field to the right of both eyes, we speak of homonymous hemianopsia. This occurs most commonly in a lateral half of the field, rarely in the upper or lower half of the field. The line of separation between the normal and the obliterated halves of the field in lateral homonymous hemianopsia runs perpendicularly through the fixation point; in many cases, however, it passes to the side of this point, so that the normal portion of the visual field extends 2°, 5°, or even 70° into the territory of affected area. This area is called the “atypical field” (Fig. 7.77). The anatomical reasons for this atypical field are still under dispute. Wilbrand ad- vances the view that fibers from both optic tracts supply the central retinal area. Foer- HEMIANOPSIA. 391 ster has described a case of bilateral homonymous hemianopsia in which complete blind- ness did not occur, as naturally would at one time have been assumed, but there remained a small central field with retention of good visual acuity (about 14). Foerster, therefore, repudiates the theory of a supply to the retina from both tracts, and concludes that that part of the cerebral cortex connected with the center of the retina is more luxuriantly supplied with blood-vessels than is the rest of the cortex, and that, therefore, in spite of thrombosis of the principal vessels, such a part of the cortex would still be nourished with blood. Finally, v. Monakow, who disputes the theory that certain areas of the retina are exclusively associated with certain areas of the cortex, or considers such » theory at least unproven and improbable, explains the escape of the central area of the retina by the assumption that it is in association with a much larger part of the cortex than is any other area of the retina. Visual acuity, color sense, and the edges of the field of the reti- nal halves still functionating, may all be normal. There is, to be sure, a gradual contraction of the field still remaining. A right- sided hemianopsia causes more disturbance than does a left-sided one, because we read and write from left to right. The ophthal- moscopic examination is normal. If both obliterated halves of the visual field are at the temporal side of the fixation point, that is, one to the left side and one to the right, the condition is spoken of as ‘temporal hemianopsia.” A ‘nasal hemianopsia”’ is perhaps possible, but no such case has been described which might not have another significance. It must be supposed that disease of the retinze and optic nerves can produce all possible forms of restrictions in the visual fields, but according to the definition given above (/. 3g0) they are not to be con- sidered hemianopic in their nature. The reason for hemianopsia will be seen by examining figs. 172 and 173 (pp. 304, 305). If the right optical tract or its connec- tions with the cerebral cortex are interrupted, or if the center for optical perception (cortex of the occipital lobe) becomes incapable of functionating, a left-sided hemianopsia must result, and wice versa. Temporal hemianopsia is obviously produced by a lesion at that part of the chiasm where the decussating fibers of both tracts are interwoven. Since the fibers that do not decussate are never in contact with each other, it is scarcely possible that the same single lesion can affect both bundles of fibers and destroy their function of caring for the temporal halves of the retinz (nasal halves of the visual field) at the same time. As anatomical causes of hemianopsia have been found cerebral hemorrhages, emboli, injuries and tumors, seated partly in the cor- tex, partly at the base of the brain. The clinical significance of hemianopsia is of pathological import, since, taken with other signs (hemiplegia, aphasia, hemianesthesia), it may be used for the localization of a brain lesion. 392 GLAUCOMA, (2) Amaurosis partialis fugax, transient hemianopsia, may occur as an attack of blindness lasting usually no more than fifteen or twenty-five minutes. The attack begins with the phenomenon of a dark spot at the same place (homonymous) in both eyes. This scotoma spreads centrifugally but remains confined to the temporal half of one visual field and the nasal half of the other. Flickering shadows are now seen, which move about in a zigzag manner (teichopsia), while the edge of the dark spot expands toward the edge of the visual field. The flickering finally ceases and the dark spot disappears. The disease must be seated in the brain cortex. It is often asso- ciated with unilateral headache (migraine), vertigo, malaise, disturb- ances of speech and of memory, and other like irregularities refer- able only to the brain. It may be assumed that the symptoms are due to arterial spasm, and that the flicker scotomata, malaise, and vertigo refer to such a spasm in the cortex, the unilateral headache to spasm in the dura mater. The first attack distresses the patient very much, but he soon convinces himself of the harmlessness of the symptom. Treatment must consist of regulation of the daily life and restriction in mental exercise. Quinin and bromid of potassium have been advised. GLAUCOMA. 1. INTRODUCTION. Glaucoma! is applied to a disease still obscure in many respects, but characterised by the essential sign of ézcrease in intraocular pres- sure. This does not imply that every eye with increased tension is glaucomatous, or that an eye is not glaucomatous because at a par- ticular instant the tension is normal. The interpretation is rather the following: nearly all pathological signs of glaucoma are directly or indirectly the results of increased tension, but the cause of this tension modifies the diagnosis and is still the starting point for all theories of glaucoma. These theories agree in only one particular, 1The name refers to the greenish discoloration of the pupil; although the same appearance is commonly seen in old and healthy eyes, if only the pupil is dilated enough. The discoloration is, therefore, suggestive of glaucoma only in cases where the pupil is dilated, as it is in glaucomatous eyes, whereas old persons usually have contracted pupils. INTRODUCTION. 393 namely, that increased tension depends upon increase in contents within the eye. The deeper question as to the cause of this increase in contents is, even to-day, an unfailing source of scientific battle. On the other hand, there is general unanimity concerning the changes in the eye which may be considered as resulting from this increasedtension. These changes appear in different forms, accord- ing as the increase in tension is rapid or slow; in the latter case the consequences are less conspicuous, because the eye has time to accommodate itself to the altered relations of tension. (a) Let us assume that there takes place a rapid increase of ten- sion resulting from increase in vitreous in an eye quite healthy up to that time. The immediate consequence will be that the lens is pressed forward and the zonule of Zinn stretched. Theadvance of the lens is shown by shallowness of the anterior chamber, the stretch- ing of the zonule of Zinn by reduction in range of accommodatwn, the contraction of the ciliary muscle being now unable to relax the suspensory ligament completely... A further consequence is a profound change in the circulation in the eye. The blood passes into the retinal vessels only during the systole of the heart, while at the moment of diastole the eye’s internal pressure overcomes the blood pressure and the arterial walls are squeezed together. For this reason an arterial pulse in the retina becomes visible with the ophthalmoscope. The retinal veins are tortuous and swollen in con- sequence of the compression on the spot where the vein bends at right angles in passing from the retina into the optic nerve. Inthe same way the venz vorticose are squeezed by the pressure within the eye just where they pierce the sclera obliquely. The result is that an abnormal amount of blood is discharged from the eye through the anterior ciliary veins and they become therefore dilated and tortuous. A third consequence is a cloudiness of the cornea. Pressure opacity may be produced at any time in the eye of a cadaver or of an animal; it might be supposed, therefore, that the opacity of glaucoma was a purely mechanical pressure opacity explainable by unequal stretching of the corneal fibrils; but the matter is not so simple (compare /, 253), since pressure opacity disappears as soon as the pressure is removed, while glaucoma opacity disappears only by degrees. Nor is the cornea alone 1 Knies explains the reduction in range of accommodation to be due to round-cell infil- tration into the ciliary muscle. 394 GLAUCOMA, cloudy, the aqueous, perhaps even the vitreous, showing the same condition. Further results of rapid increase in pressure impress the ciliary nerves in the form of pain radiating toward the forehead and upon the face (ciliary neuralgia), and the nerve fibers supplying the sphincter pupillaz and cornea (paralysis). A paralysis of the sphincter makes the pupil large and immovable (iridoplegia), and paralysis of corneal nerves makes the cornea insensitive. Finally, a result of rapid increase in tension may show itself as infammation. A purely mechanical explanation of this fact is quite impossible. The inflammation is evidenced by lacrimation, redness, and swelling of the conjunctiva and lids, by cloudiness of the aque- ous (and vitreous ?), and by discoloration of the iris; even posterior adhesions have been observed. The corneal opacities and the pain may, of course, be ascribed to the inflammation itself (f. 702). It is obvious that these changes must severely disturb the visual acuity, which, with a cloudy cornea, may sink even to the mere ability to count fingers. If this reduction in vision depends solely upon opacity of the refractive media, the field of vision will be of normal extent; but if retina and optic nerve are injured by inter- ruption to the blood current, there will be, besides a reduction in visual acuity, a distinct contraction of the visual field. If the in- creased tension is very decided, retina and optic nerve refuse al- together to functionate, the eye cannot even distinguish light from darkness, and is therefore amaurotic. (6) Let us assume another case, in which, by increase in the vitreous, an increase in internal pressure results very gradually. There is no sign of inflammation, pain only slightly or not at all complained of; but the anterior ciliary vessels are dilated and tortu- ous, the anterior chamber is shallow, the pupil moderately dilated, and the iris sluggish in movement. In addition, there is one more sign that is of the greatest diagnostic importance—¢he excavation of the optic-nerve sheath. This sheath is the portion of the fundus offering the least resistance, and has been softened, perhaps, by some inflammatory process (f. so2). As a consequence of continued increase in pressure, the nerve gives way, and in time an excavar tion is produced. Hand-in-hand with the crowding of the optic nerve backward there is atrophy of the nerve fibers. The result is that the field of vision becomes contracted, and the acuity of vision declines till total blindness is the final outcome. GLAUCOMA ACUTUM. 395 Glaucoma as an idiopathic disease usually attacks persons of fifty or beyond, although younger persons are not altogether out of dan- ger; a case of glaucoma has been reported in a five-year-old boy. Hyperopes are more disposed to glaucoma than emmetropes; myopes are least affected; a particular predisposition is found in those who suffer from trigeminal neuralgia. Both eyes are at- tacked, as a rule, although not necessarily at the same time; the interval between the disease in the first eye and that in the second may be only a few hours, or it may be twenty years. 2. VARIETIES OF GLAUCOMA. A. PRIMARY GLAUCOMA. Glaucoma is called primary if it occurs in an eye previously healthy ; secondary, if in an eye already affected by some disease. (2) Glaucoma Acutum (/xflammatory Glaucoma)—Prodromal symptoms usually precede an attack of idiopathic glaucoma. They consist of moderate pain in the eye and its surroundings, haziness or actual cloudiness of the visual field, and the appearance of col- ored rings about flames of light, this last being a phenomenon of diffraction due to a moderately diffused corneal opacity." If occasion offers to examine an eye during such a prodromal stage, it is found to be of moderately increased tension; the con- junctiva is hyperemic, the cornea soft and delicately “smoky,” the aqueous similarly cloudy, the pupil moderately dilated—in short, all the consequences just described of rapid increase in tension of moderate degree. Such symptoms appear at intervals, and each attack may subside without injuring the eye. It may be repeated for weeks, months, or even years, but finally a severe attack occurs, which is the fully developed glaucoma, glaucoma evolutum. A developed glaucoma is easy to recognize during an attack. The association of inflammation and dilated pupil is seen in no other disease of the eye,’ while it may be noted that the redness of glau- 1 Colored rings around flames are seen by any person whose corneal surface is smeared over by a finely diffused conjunctival secretion (see Z. 786). 2 Of course, it is assumed that the dilatation of the pupil is not the effect of atropin. The very first question addressed to any patient with an inflamed eye and dilated pupil must, therefore, always be whether he has not already been treated by a physician. 396 GLAUCOMA. comatous inflammation has its own peculiar somberness. If there is also an increase in tension, the presence of glaucoma can no longer be in doubt. In spite of all this an attack of acute glaucoma is at times mistaken. It may happen that intense headache, fever, and vomiting takes away any suspicion that the eye is in- volved, and leads to the diagnosis of some general systemic disease. Confusion with serous iridocyclitis is also possible, since in the latter the pupil is dilated, though not so noticeably as in glaucoma, and the tension is increased; but in serous iridocyclitis the anterior chamber is deep; in glaucoma, on the contrary, it is shallow. Moreover, the deposits on the posterior surface of the cornea, which are so unusually characteristic of serous iridocyclitis, are never, or only in the most insignificant degree, present in glaucoma. The course of the disease may vary considerably. In the worst, and, fortunately, the rare cases, the result of the first attack may be, within a few hours, total and incurable blindness—glaucoma fulmi- nans. The rule is that the storm breaks after days or weeks of severe pain, but leaves behind it a permanent increase of tension with all its dire consequences. This is shown in excavation of the disc, reduction in visual acuity, and contraction of the visual field. After a time a new attack occurs, producing further impairment, until finally the eye becomes of stony hardness and totally blind; this condition in progressive glaucoma is called glaucoma absolutum. The pathological storm may not calm down, the eye may remain somewhat inflamed and, of course, with increased tension, and this condition is called chronic inflammatory glaucoma, (2) Glaucoma Simplex (Siple Glaucoma).—The essence of sim- ple glaucoma, also, is increase in tension, but this increase develops so slowly that the patient fails to notice its consequences. Gradu- ally, however, after these consequences have made a lasting im- pression, the patient notices some impairment in vision. An ex- amination by the surgeon at this time shows reduction in visual acuity and contraction of the visual field, more or less marked as the disease has been of longer or shorter duration. The form of the visual field is somewhat peculiar ; that is to say, it is contracted with preponderant involvement of the nasal half (Fig. 142, a, left visual field). As the disease progresses the visual field contracts more and more, so that finally there remains only a segment on the temporal side (Fig. 142, 6, right visual field ). The objective examination shows that the visual disturbances are not due to changes in the refractive media, but depend upon the excavation within the optic nerve sheath and upon the asso- ciated atrophy of the nerve fibers. GLAUCOMA SIMPLEX. 397 There are three varieties of excavation of the disc, a physiological, an atrophic, and a glaucomatous. The physiological (Fig. 743) is always bilateral, includes only a part of the surface of the disc, and is to be considered an exaggeration of the physiological cup (4%g. 743) from which the retinal vessels spring into view ; these vessels must, therefore, pass over part of the papilla on a level with the retina before they reach the retina itself Fic. 142.—VisuaL Fietps 1n StmpLte GLaucoma. The darkened areas denote the obliterated portions of the fields. (fig. 145). In atrophic and glaucomatous excavation the condition is quite different ! In both, the entire nerve sheath + is pushed back from the plane of the retina; in the atrophic variety no further than the lamina cribrosa, that is, about as far as the thick- ness of retina and choroid; but in the glaucomatous variety (7g. 744) very much far- ther, since the lamina cribrosa itself is carried backward by the pressure. Consequently, ne FRLOT TALUS Yuaece Be Bes, » Fic. 143.—PHysiotocicat Excavation. (A/ter Pagenstecher and Genth.) The excavation is about one-third as broad as the optic nerve. Just below the excavation are seen cross-sections of two blood-vessels. the blood-vessels at the edge of the disc appear in glaucomatous excavation as if broken off (Fig 16), and in atrophic excavation only moderately bent over or, perhaps, not at all modified. 1 Schweigger declares that pressure excavation may include only a part of the surface of the disc. The distinction between this and physiological excavation would, in such a case, be impossible by mere examination. Other factors would have to be considered, above all, the functionating powers of the eye; normal visual acuity and normal visual field would exclude pressure excavation with certainty. Again, the disc of the other (healthy) eye must be used for comparison. If this disc is flat, an excavation in the diseased eye, even if only partial, would indicate a glaucomatous origin. 398 GLAUCOMA. The degree of excavation can be estimated by the help of parallax (f. 7375), or meas- ured by determining the refraction at the edge of the disc on the one hand, and at the base of the excavation on the other. In pressure excavation there is often to be seen a ‘‘ halo glaucomatosus,”’ that is, a yellowish-white ring surrounding the disc, ophthalmoscopic evidence of the obliterated choroidal ring (/ig. 246). Excavations cannot with cer- tainty be distinguished by their color, for in all three varieties the excavated portion is white and dotted over with fine points, due to the shimmer of the lamina cribrosa. In be Fic, 144.—GLaucomatous Optic-Nerve Excavation. (After Pagenstecher and Genth.) physiological excavation, however, the larger and not excavated portion of the disc appears of a normal color (/%g. 745), while in glaucoma there is a greenish shadow run- ning along the papilla’s edge. The diagnosis of simple glaucoma rests upon three principal signs: zepatred vision, excavation of the disc, and increased tension. If this last sign can be demonstrated or recognized by its results Fic. 145.—OrHTHALMoscopic IMAGE IN Puysio- Fic. 146.—OPHTHALMOSCOPIC IMAGE 1N GLAU- pe Optic-Nerve Excavation. (A/ter ea Optic-NERVE Excavation. (A/ter (shallow anterior chamber, dilated and sluggish pupil, arterial pulse), the matter is easy enough; but tension is not demonstrably in- creased in all cases, and the diagnosis is then rather difficult. There are several reasons why the increase in tension in simple glaucoma is‘not infrequently undetected. First, because the internal pressure has been guessed at by the sense of touch, instead of GLAUCOMA SIMPLEX. 399 measured by a practical tonometer (f. 739), which might have supplied trustworthy evidence. Second, it may be assumed that tension is increased only at intervals; this accords with the fact that in simple glaucoma, also, haziness and the appearance of colored rings around flames are noticed only at intervals. Finally, it must be remembered that there are hard eyes and soft eyes, but that in neither does the tension go beyond the normal; and that the resistance of the optic-nerve sheath is not the same inalleyes. It may therefore happen that a moderate increase in tension in an originally soft eye, with a disc lacking resistive power, may result in an excavation, although the eye appears no more than “ physiologically hard.” All these explanations are still unsatisfactory, since there are cases in which an arti- ficial reduction of tension does not at all check the decline of visual acuity. We must, therefore, assume that occasionally there are cases diagnosticated and treated as “ simple glaucoma,’’ which depend upon accidental coincidence of physiological excavation and some form of optic-nerve atrophy. The difierentiation of these cases may be very difficult. It is relatively easy if the disc of the other eye is smooth, for a deep excavation in the diseased eye must be due to pres- sure—pathological—and cannot be physiological. If this distinction is lacking, continued observation of the patient, or careful study of his own case by himself, will be the only means of furnishing proof that increase in tension does occasionally occur, and that, therefore, the disease is to be considered glaucoma. The preceding description makes it evident that inflammatory and simple glaucoma are only different forms of the same disease, but that for practical purposes it is necessary to consider each as a distinct pathological picture. The intimate connection between them can be seen in various clinical manifestations. For example, cases have been reported where simple glaucoma was found in one eye and inflammatory glaucoma in the other of the same individual ; simple glaucoma has of a sudden changed into the inflammatory form, the obvious reason being that the hitherto moderate tension became suddenly alarmingly increased. The reverse has happened: oftener than the surgeon likes, probably, he discovers that an eye, after an operative cure of an inflammatory glaucoma, gradually becomes hard again, that the visual field becomes narrower, the visual acuity reduced—in other words, that a simple glaucoma has replaced the inflammatory glaucoma supposed to be cured. More- over, it must be observed that there are various stages between the inflammatory and simple (non-inflammatory) glaucoma ; such inter- mediate conditions being sometimes grouped apart as “ chronic inflammatory glaucoma.” (/. 396). 400 GLAUCOMA. (c) Glaucoma Infantile (Glaucoma of Childhood), Ay drophthal- mos or Buphthalmos Congenitus.—Considering the delicacy and tenderness of fetal and children’s tissue, it is easy to see that increased tension will stretch a fetus’ or child’s eyeball. Consequently, in infantile glaucoma a pathological picture is developed which bears but little external resemblance to the glaucoma of adults. The es- sential resemblance, however, is seen in the increased tension and in the gradually resulting excavation of the optic-nerve disc. The earli- est changes will be noticed in the cornea; this becomes larger than normal, the diameter of the circumference at the margin between cornea and sclera being as great as rg mim. The cornea is more or less hazy, and there are blood-vessels at its edge. Such a con- dition may lead to comparison with keratitis parenchymatosa. The tension must therefore be carefully tested, a difficult matter in children, and often impossible without resort to narcosis. The an- terior chamber is extraordinarily deep—7z2.6 mm.in onecase! The iris is dull and lusterless, the pupil dilated, sluggish, or rigid. The lens is small, sometimes cloudy, and insecure, owing to stretching of the suspensory ligament. B. SECONDARY GLAUCOMA. Many diseases of the eye may cause increased tension. This increase in tension is called secondary glaucoma in case it is pro- nounced and lasting enough to influence the visual field and visual acuity. Since it is sometimes difficult or impossible to say in an individual case whether impaired vision is due to the original dis- ease alone, or to the increase in tension, the expression “ secondary glaucoma” enjoys a remarkable elasticity. Secondary glaucoma has, of course, the same effect as primary glaucoma. (2) Among diseases of the zris, total synechia (/. 277) plays the most important part. The reason for increased tension is in this case very evident. The natural current from the posterior to the anterior chamber is blocked, and the fluid secreted by the ciliary body must therefore overfill all this space, as is evidenced by the bulging forward of the iris. Less certain to lead to increased ten- sion are isolated adhesions of the ciliary edge of the iris to the cornea, or to a scar in the sclero-corneal margin. The causal con- nection is nevertheless quite evident. (See Theories, p. 402.) (2) Among diseases of the /exs, injuries and luxations are the principal conditions leading to increased tension. With reference PATHOLOGICAL ANATOMY. 40} to injuries to the capsule the question has already been discussed in the section on traumatic cataract (f. 339). The swollen lens sub- stance is the more certain to cause increased tension, the more capa- ble of swelling the lens is, and the more rigid the sclera. Elderly persons are more in danger than the young, chiefly on account of the rigidity of the sclera. How a luxation of the lens can cause glaucoma is not so clear. The best explanation is that the mova- ble lens irritates the ciliary body by dragging on the zonule of Zinn, exciting it to pathological secretion and to inflammation. (c) Retina.—Atheroma of the retinal vessels not infrequently causes hemorrhage. From two to eight weeks later there is in- creased tension and “hemorrhagic glaucoma.” This form is par- ticularly dangerous, and in spite of prompt treatment usually ends in blindness. (d) Tumors of the interior of the eye, particularly of the ciliary body, may cause increased tension by occupying all the space, and perhaps by hindering the discharge of lymph from the eye. 3. PATHOLOGICAL ANATOMY. The number of glaucomatous eyes that have been examined microscopically is large, but most of them were already blind and were removed for the severe pain they caused. The changes found in them are, therefore, doubtless in great part, not causes but re- sults of glaucoma, and of but little value in support of any “ glau- coma theories.” Leber found droplets in the epithelium of glaucomatous cornee, and Fuchs in both epithelium and cornea proper, particularly in the anterior layers. Fuchs consequently denominates glaucoma- tous corneal opacity as “inflammatory edema” ( f. 253). The neighborhood of the canal of Schlemm is, according to Knies, infiltrated with round cells even before the real disease be- gins, and the same is true of the root of the iris and of the ciliary body. As the disease progresses there may be a circular adhesion of the root of the iris to the posterior surface of the cornea, which would obliterate the recess in the anterior chamber between them and block up the chief channels of the circulation within the eye. Iris and ciliary body show at first round-cell infiltration, and later atrophy ; and this round-cell infiltration has been found in the cho- 26 402 GLAUCOMA. roid, particularly along the veins. Hyaline degeneration of the vessel walls has been described, as well as atheroma of these ves- sels and of those in the retina (hemorrhagic glaucoma). In the optic nerve are found the most important and most regu- larly occurring changes. According to Schnabel they are due to an interstitial neuritis in the part of the nerve still provided with its medulla, that is, behind the eyeball; or to inflammation or mere atrophy of the nervous and connective-tissue elements in the optic- nerve sheath. 4. THEORIES. In speaking of secondary glaucoma it was pointed out that some cases need no theory, that is, no explanation built up from assumptions. As a matter of fact, increased tension resulting from swollen lens substance, or from a tumor increasing faster than the vitreous can decrease, or from total synechia, explains itself. In the first two cases it is the in- crease in the contents of the eyeball, in the last the retarded circulation between posterior and anterior chambers, which causes the increase in tension. But what—in other cases of glaucoma, especially the primary forms—causes the increase in tension? Is it the blood pressure? Then without doubt the tension of the eyeball will be a criterion of the blood pressure. The attempt has been made on ani- mals to raise the eye’s tension by pressure on or ligation of the jugular veins, but this by no means produced glaucoma. Moreover, it is known from observations on men with high blood pressure—fever patients, for example—or on men with low blood pressure—those near death—that the internal tension of the eye is very far from following the variations of the blood pressure. Again, the assumption that disease of the iritic or choroidal vessels can block the circulation and cause stasis needs a much more substantial support of pathological facts than we have as yet. The study of the circulation in the eye (f. 269) has been productive of more fruitful results. In order to retain the internal tension of the eye at a normal equilibrium, there must also be equilibrium between the secretion of the ocular fluid on the one hand, and its escape on the other. Hindrance to the escape of fluid, or increase in its secre- tion, or both together, must cause increased tension. Many ophthalmologists lay par- ticular stress upon the hindrance to the escape of fluid, assuming, with Knies, that the essential and final cause of glaucoma is an inflammatory infiltration at the root of the iris and at the sclero-corneal margin. ‘The resultant cicatricial contracture would block up the angle between iris and cornea, where the principal drainage canal for the aqueous lies. Increased tension with all its consequences would naturally result from it. Other ophthalmologists contend that the shallowness of the anterior chamber stands in direct contradiction to this theory. It is evident that hindrance in the path of a stream must cause backward stasis and a consequent broadening of the path itself. It is, there- fore, more logical to consider the blocking up of the angle to be rather the result of increased tension, the cause being sought in increase in the eye’s contents lying behind the iris and lens. In favor of this ‘‘ secretion theory ’’ it may be adduced that many cir- cumstances indicate that primary glaucoma is connected with disturbances in the nervous system. For example, in many cases trigeminal neuralgia precedes an attack of glau- PROGNOSIS AND TREATMENT, 403 coma; or glaucoma may appear at intervals with the peculiar characteristics of neuralgia ; or glaucoma may often be produced by mental states of shock and anxiety. Again, many of the phenomena of secretion are directly under the influence of the nervous system—the secretion of tears, for example. By artificial stimulation of the cili- ary ganglion in dogs the internal tension of the eye can be noticeably and permanently raised, and we may therefore assume that when this ganglion is stimulated, the secretion of fluid is increased, and that glaucoma depends upon an analogous process. This by no means exhausts the number of glaucoma theories, but there is nothing to be gained by pursuing the subject farther, for theories that appear to one man to solve the problem seem to another as mere fantasies of the brain. It may be mentioned, per- haps, that Schoen, after years of study and investigation, ascribes glaucoma to overexer- cise of the accommodation, and would lay more weight upon prophylaxis of glaucoma by properly selected glasses than upon mere operative treatment. I once performed an irideetomy for the ripening of cataract. Both eyes were soft, the anterior chamber noticeably deep, and there was no suspicion of glaucoma. Imme- diately after the iridectomy the anterior chamber filled with blood. The next day the blood was to a large extent absorbed, and I then gave atropin. When the bandage was again changed it was spotted with blood, there was blood in the conjunctiva and in the anterior chamber. I feared an injury, but on the next day the blood was again dimin- ished. Unsuspectingly, I again gave atropin. On the next day the eye was as hard as a stone, the cornea cloudy, the chamber full of blood—hemorrhagic glaucoma. With eserin, cocain, and warm compresses the cyclone passed by, with no worse results than a line of delicate posterior synechiz. This case shows that in spite of deep anterior chamber, in spite of softness of tension, in spite even of a preceding iridectomy, an eye may be the victim of glaucoma; the case supports the suspicion, too, that the disposition to glaucoma consists of a pathological character of the blood-vessels, and that an attack of glaucoma is excited by the nervous system; for the effect of atropin upon the smooth muscular fibers in the eye, and there- fore upon the condition of the vascular walls, is probably brought about by paralysis of the peripheral nerve-endings. 5. PROGNOSIS AND TREATMENT. Every case of glaucoma, if untreated, will surely end in complete and incurable blindness. It is, therefore, much to be regretted that many and many a time the error is made by physicians of diagnos- ticating any decline in visual acuity in elderly persons as due to cataract, and that physicians send such patients to the ophthal- mologist only when the neglected “ simple glaucoma” has already approached the stage of incurable blindness. Quite as serious is it to confuse acute glaucoma with iritis, a mistake that would seem impossible if the dilated pupil of glaucoma is considered, and yet it 1 This explains the fact that often enough during operative treatment for glaucoma on one eye, the other sound eye is attacked by the disease. It is advisable, therefore, dur- ing an operation for glaucoma to instil eserin or pilocarpin into the apparently healthy eye. 404 GLAUCOMA. is made again and again. Overlooking the effect of such serious errors, the prognosis is decidedly favorable for acute glaucoma if treated properly, doubtful for simple and infantile glaucoma, and unfavorable for hemorrhagic glaucoma. The aim of treatment 1s the reduction of tension. To reach this goal we have three methods at our command :— (1) Medication, by eserin or pilocarpin. (2) Massage. (3) Operation, by corneal puncture, iridectomy, sclerotomy, and (the newest) incision of the ligamentum pectinatum. The effect of myotics such as eserin and pilocarpin, as well as that of their antagonists, the mydriatics—atropin, homatropin, and cocain—has already been discussed (. 270). We need mention here only their effect on the eye’s internal tension. In the healthy eye they produce no appreciable change in tension. Cocain is an exception, for it has been frequently observed that healthy eyes of elderly persons are made noticeably soft by cocain. The effect may be quite different if there is a pathological increase of tension already present. Myotics reduce tension, but mydriatics, even cocain at times, increase it. To use atropin if there is the least suspicion of glaucoma is, therefore, unconditionally forbidden, and even homatropin or cocain are to be used only with the greatest caution. The connection between dilatation of the pupil and increased tension is not quite clear. Many suppose that the iris when dilated rolls up into the filtration angle and retards the outflow of aqueous, and that contrariwise an expanded iris leaves free the filtration angle, and therefore offers no obstruction to the principal outlet for the eye’s fluids. The fact admits of other explanations, however. Glaucoma cannot be healed, but single attacks may, in favorable cases, be cut short by means of pilocarpin or the stronger eserin. These remedies are therefore of inestimable value, especially if the problem is to obviate the danger of increased tension until the pa- tient can consult an ophthalmologist. Myotics are also of valuein simplifying the performance of a sclerotomy or an iridectomy. And, finally, they are used extensively in the after-treatment. The second method, massage, is used principally in the after- treatment, and in cases of simple glaucoma for which one or more futile operations have been performed, and in which, therefore, the surgeon’s task is to retard as long as possible the unavoidable decline in visual acuity. The result of massage is instantaneous, the hard PROGNOSIS AND TREATMENT. 405 eyeball grows soft under the physician’s finger, so to say, but its effect is not lasting. The patient should, therefore, learn to mas- sage himself, and practice it daily. In massage it is quite prac- tical to use a salve containing eserin and cocain: serin sulf., 0.025 ; Cocain muriat, 0.25; Vaselin, 5.0. Corneal puncture is a method of the moment. As the aqueous escapes the contents of the eyeball is of course reduced, the tension decreases, the consequences of the previously increased tension disappear—for a short time only. The essentially curative method in glaucoma is zridectomy ( p. 280). A.v. Graefe devised it, and it is one of the services he performed for science which renders his name immortal. Preparations to prevent infection are the same as in the operation for cataract (f. 357). If the anterior chamber is shallow (as it usually is) and the iris small, the careful performance of a broad iridectomy extending to the ciliary border is made un- usually difficult and of danger to the lens. It may be somewhat facilitated by instilling eserin in advance, and by making the in- cision with v. Graefe’s cataract knife (fag. 726, p. 348) instead of with the keratome; of course, with the knife the iridectomy can be made only above or below. Iridectomy upward is almost always the rule, since the space left by removal of part of the iris is covered by the upper lid. The incision should lie in the opaque tissue of the sclera. The effect of an iridectomy in cases of acute glaucoma is extra- ordinarily favorable. Tension becomes normal and all visual dis- turbances due to increased tension disappear. Visual acuity may, in the course of time, become normal, even when it has been reduced to counting fingers or to a mere perception of light from darkness. How this effect is produced is at present as much a matter of dis- cussion as is the nature of glaucoma itself. In my experience I have very often seen posterior synechiz (plastic iritis) after an iridectomy, in spite of the most scrupulous antisepsis. I suppose that it is to be ascribed not to infection but to increase in the inflammatory condition which the glaucoma had produced in the iris. The iritis can be antagonized with cocain or, in some cases, with homatropin and with warm compresses of boric acid solution—compresses being used, of course, only after the wound has healed and the anterior chamber filled. Tridectomy makes a hole in the iris which, if it lies below the palpebral fissure, causes dazzling and distortion. There is, as a rule, a change in the shape of the cornea, evidenced by an astigmatism that somewhat influences visual acuity. Not infrequently 406 GLAUCOMA. there are hemorrhages in the retina as the result of the sudden reduction of the internal pressure. In case they are in the center of the retina they cause noticeable visual dis- turbances ; if very numerous, they may be quite destructive, but, as a rule, they are with- out serious effect. They should be avoided by allowing the aqueous to escape very slowly during or after the completion of the incision. The scar in the sclera made for glaucoma is somewhat peculiar; it is broader and strewn with dark spots, while an iri- dectomy in a healthy eye leaves a very narrow, or, perhaps, an invisible scar. These dark spots are from the glistening pigment of the iris or ciliary body. The scar tissue often shows little vesicular elevations; such a scar is called cystoid. In case a cystoid scar does not of itself contract, it may be obliterated by the cautery. In many cases glaucoma is cured by an iridectomy and remains so. In others tension increases again after a longer or shorter interval, and the result is the picture called simple or chronic inflam- matory glaucoma. It is evident that in simple glaucoma iridectomy can be of but little service, since the visual disturbance depends essentially upon the changes in the optic nerve, which, even in the best cases, can be brought to a standstill but not overcome. In oN Fic. 147.—ScLEROTOMY, about one-third of the cases even this result is not obtained. Effort has been made, therefore, to find some other method of treatment, and sclerotomy was resorted to. According to v. Wecker, iridec- tomy is to be replaced by sclerotomy— (1) In certain cases of simple glaucoma. (2) In infantile glaucoma. (3) In hemorrhagic glaucoma. A prime condition is that the pupil can be well contracted by eserin. The operation is performed in the following way: A v. Graefe’s cataract knife is introduced z mm. from the corneal edge (at 2, Hig. 147) into the anterior chamber and is brought out at a corresponding point (at 4) on the other side. The tissue is now cut with saw-like motions, as if a flap were to be formed, but finally a bridge of tissue is left just about as long as each of the two inci- sions. As the knife is withdrawn, its point should be brought into the filtration angle and the “arch of the spaces of Fontana” cut CYSTICERCUS. 407 through. This last step in sclerotomy—the incision of the liga- mentum pectinatum—has been performed by Taylor as an opera- tion of itself for glaucoma, with good results. Sclerotomy is said to make a “filtration scar,” that is, to provide porous tissue for the aqueous. According to this, a cystoid scar ought to be the type of a filtration scar, but even after a cystoid cicatrization, tension may rise again. The good effect of sclerotomy is therefore not yet quiteclear. In the patients I have treated with sclerotomy I have only twice seen a really satisfactory reduction of tension, If the iris tissue is atrophic, iridectomy usually produces no perceptible reduction of tension. The operation may also be incomplete. It may happen that neither iridectomy nor anterior sclerotomy is applicable, because the iris is atrophic, the anterior chamber very shallow, and the pupil unaffected by eserin. In such a case we may try posterior sclerotomy, that is, a meridional section through sclera into vitreous, which allows some fluid, yellowish vitreous, to escape. I have several times resorted to this method with comparatively good success. For example, I have now a patient with visual acuity and visual field about as they were two years ago when she came to me for treatment on ac- count of relapsing glaucoma; during this time I have performed posterior sclerotomy twice on each eye, instilled pilocarpin, and ordered daily massage. The patient stopped the treatment several times on her own responsibility, but the rainbow vision returned, and she was only too glad to begin vigorous massage and pilocarpin treatment once more. ENTOZOA—PARASITES IN THE EYE. I. CYSTICERCUS. The larva of the tape-worm (tenia solium) is called cysticercus cellulose. It may be found in all parts of the human body. These larve cause disturbances chiefly when located in the brain and in the eye, the latter location only being of interest to us. How does the larva reach the eye? It is found in men in whom a tape- worm has already found lodgment, or in those who are bedfellows of tape-worm patients, or in others in whom no tape-worm infection can be demonstrated. A tape-worm host can infect himself, either because the segments reach the stomach from the intestine during vomiting, or because the eggs are carried by dirty fingers and swal- lowed with the food. This may be the same process by which a person becomes infected from a companion. In any case the egg of the tape-worm must reach the stomach. The gastric juice dis- solves the shell of the egg, the embryo is released, pierces the 408 ENTOZOA—-PARASITES IN THE EYE, stomach wall, reaches the blood current, and lodges finally in the eye. The cysticercus consists of head, neck, and body (vesicle) (Fig. 48). The head bears four suckers and a row of hooklets. Head and neck may be withdrawn into the body so that the whole figure looks like a bladder (/7g. 749) of 4 mm. diameter, in which a white, opaque spot may be recognized as the head with its suckers. The parasite floats in a second bladder filled with fluid; it is supposed that this external vesicle—the house of the larva—is sup- plied by the tissue of the host. ete a The larva has been found beneath the skin of with Exrenpven the lids, below the conjunctiva, within the orbit, Heapanp Neck. (A/- i ‘ s p ter Stein.) in the anterior chamber, in the vitreous, and be- hind the retina. The commonest occurrence is that the larva rests at first behind the retina, and during its growth, either with or without the external vesicle, breaks into the vitreous. Such a case is most important, not only on account of its com- parative frequency, but also with reference to its treatment, and is, therefore, used as the basis for the following description :— The first sign of the larva within the eye is a visual disturbance in the form of a dark spot, whose location in the visual field is dependent upon the location of the larva in the eye. Later on, there is distortion and finally cloudiness of the entire visual field, and consequent- ly a reduction of vision, even if the larva lies eccentrically in the fundus. In cases observed by v. Graefe from the beginning with the ophthalmo- scope, there was at first a bluish- gray haziness at a certain spot on the Fic. 149.—Cysticercus, wit Neck fundus. This opacity grew larger Renee (eee ea during the succeeding weeks and protruded distinctly. Then the larva burst out of the apex of the protrusion, into the vitreous; or in other cases it first made a path downward between retina and choroid before it finally broke out. The original location of the larva remained a grayish-blue spot with white, somewhat prominent edges. If the larva is seen while the vitreous is still unclouded, the - Cysticercus. - Head. -- External vesi- cle. CYSTICERCUS. 409 recognition of the disease is easy. The examination in the in- verted image should be made with a strong convex lens (25.0 D) in order, if possible, to see the whole larva at one time. We would find a blue-gray vesicle about four times the diameter of the papilla, the edges of the vesicle being a sharply defined, yellowish-red, glis- tening circumference; the play of color on the circumference is seen most distinctly in the upright image by rotating the mirror. Not unfrequently we may succeed in detecting through the exter- nal vesicle movements of the larva itself; this is particularly easy if the larva is naked, that is, if it lies in the vitreous (Aig. 750) or in the anterior chamber without any second vesicle. We see peri- Fic. 150.—OrHTHALMoscoric ImaGe oF A Livinc CysTICERCUS IN THE VITREOUS. (After Liebreich.) staltic-like movements passing up and down the vesicle, and if they are very active they give a swing-like motion to the whole body. The picture is most fascinating if the animal extends its neck and head with its suckers and moves itself about in an apparently tire- less way. This condition may last for weeks or months, but gradually the parasite or its morphological products will act as a source of irrita- tion ; the vitreous becomes opaque, obscuring the image, but of it- self possessing such characteristics that the condition will establish the diagnosis for one who has had experience. These vitreous opacities are like curtains looped together, extending through the entire vitreous, somewhat transparent and slightly movable, the 410 ENTOZOA—PARASITES IN THE EYE. appearance being quite different from that presented by the torn and untransparent lumps, threads, and shreds of the usual vitreous opacities. On account of their relative transparency they permit for a long period the recognition, at a certain spot on the fundus, of a bright, bluish-gray reflex—the larva. These opacities become denser, the retina finally prolapses, until the diagnosis becomes impossible, or can be only conjectured. Finally, we find numerous signs of a chronic iridochoroiditis. It need scarcely be mentioned that at this stage all vision has been long since obliterated. With varying cessations or relapses of the pain and other symptoms of inflammation the eye becomes soft and contracted. The sensibility of this “ phthisical” eye may be gradually lost, and the eye become permanently quiet. Sympa- thetic inflammation is not to be feared. Prognosis is always unfavorable. Without interference every parasite causes blindness in the eye attacked within chree to fifteen months. Treatment should be prophylactic if possible,—such methods as are used for the prevention of the tenia in general. Since the in- troduction of a municipal meat inspection, cases of the disease in Berlin have become noticeably less. Personal cleanliness, the avoidance of raw meat, ham, and sausage, and the cure of tape- worm in one’s self or in one’s bedfellow, must be insisted on. Ifa larva reaches the eye, it must be removed by operation, which con- sists of a meridional scleral incision for the introduction of a toothed forceps. If the incision has been properly located, the delivery of the parasite is usually an easy matter, provided that it is not float- ing freely in the vitreous, but is attached to the eye-wall, and that the opacity of the vitreous has not already developed beyond the point where a proper localization of the larva is still possible. If the operation is done early enough, that is, particularly before pro- lapse of the retina has resulted, a good vision—even VY = z—may be retained. Here in Ziirich a cysticercus is the greatest rarity. I have seen only one case, proba- bly the first in Ziirich, and I operated on it. The patient was Swiss, but had worked for a long time in Hamburg as a butcher. The eye was already blind. The operation could not, therefore, restore vision, but only prevent inflammation and atrophy. The rarity of the parasite in the eye in many districts is remarkable, considering that in these very districts tape- worm itself is by no means uncommon. For example, in many localities of Switzerland tape-worm is very prevaient, while cysticercus is very rare. The explanation may lie in the fact that not all tape-worms are capable of spreading larvee FILARIA. 411 through the human body. To illustrate, all larvae seen in the eye are from the tenia solium, while the tape-worm so common on Lake Geneva is the bothriocephalus. Il. FILARIA—(Tureap-Worms). It has happened repeatedly that remnants of the embryonic ar- teria hyaloidea have been taken for thread-worms. Thread-worms have, however, been found in opaque lenses removed on that account. Kuhnt has recently described a case in which a thread- worm was seen in the vitreous, by the ophthalmoscope, removed by operation, and demonstrated as an anatomical specimen. The matter would be of little practical interest on account of its great rarity, were it not that, as Kuhnt emphasizes, the possibility ought to be thought of that many cases of retinitis with vitreous opacities and retinal prolapses of unknown origin may be due to undiscov- ered parasites. Independent movements of the questionable object ought to be of great importance in making a diagnosis. INJURIES TO THE EYEBALL. Injuries to individual parts of the eye have been already dis- cussed in previous sections. There remains for discussion the effect of an injury upon the eye asa whole, in other words, how injuries of several parts are associated in one pathological picture. In view of the extraordinary complexity of such pictures a descrip- tion of all of them is scarcely possible, and only a few examples can be made use of. It is therefore unavoidable that something of what has previously been said should be repeated. Those persons are most often injured who have certain danger- ous occupations, stone-masons or bricklayers, for example. Such injuries connected with occupations might be to a great extent avoided if the workmen could be induced to wear protecting spec- tacles. Unfortunately, this is seldom done. Man’s carelessness to the danger of his calling is traditional. A mason, from whose cornea I had repeate dly removed foreign bedies decided finally, at my request, to use protecting spectacles. A short time afterward a large splinter struck one glass and smashed it, but the eye was unirijured, a splendid proof of its efficiency. The mason, however, was in no hurry to get his spectacles repaired, and soon came to me again with another foreign body in his cornea. 412 INJURIES TO THE EYEBALL. 1. INJURIES BY PUNCTURE AND INCISION. Puncture wounds may be made by forks, needles, scissors, thorns, pens, and such sharpimplements ; incisions, by knives, swords, glass, and the sharp edge of any such hard objects. The danger to the eye arising from such a wound depends not only upon the ana- tomical injury, but also upon whether the wound has or has not been infected by pathological germs. The dangers of infection are greater in punctured wounds because disinfection by the physician is, as a rule, impossible on account of depth and narrowness of the traumatic canal. Piercing wounds of the sclero-corneal margin are particularly to be feared, because the ciliary body also is injured, or prolapses into the wound and becomes incarcerated in the scar. Such adhesions of the ciliary body lead most usually to chronic cyclitis or even to sympathetic inflammation of the other eye. The reason of the danger of injury to the ciliary body is not yet satisfactorily explained. ‘We may suppose that the entrance of germs is in this case particularly easy, or, perhaps, takes place subsequently through the very thin scar; or that the contraction of the scar tissue produces a laceration in the sensitive ciliary body which, in its turn, may be the cause of inflammation. A retraction of the scar is always a sign of such an atrophy and is to be considered the eye’s death-warrant. Wounds of the sclera are almost always accompanied by prolapse of choroid and retina and by more or less loss of vitreous. The unprolapsed portion of the retina may be loosened—in which case perception of light is lacking and the restoration of visual energy must be given up. An important question in every injury to the eyeball is as to whether or not the lens is injured. Every injury to the lens cap- sule ends in traumatic cataract (f. 339). Injuries to the lens, therefore, impair the prognosis materially, all other conditions being equal. Treatment consists in radical disinfection of lids and tear sac (if this is diseased), in douching the conjunctival sac with z - 5000 sub- limate solution, closure of the wound with conjunctival suture, dust- ing with finely powdered iodoform, antiseptic bandage, and rest. If the iris has prolapsed, the attempt should be made to replace it by a spatula and to retain it in place by eserin; if this does not suc- ceed, or if, by reason of size and position of the wound, it is irre- placeable, the prolapsed portion must be seized with forceps, drawn out, and cut off. If the lens capsule is injured, atropin and ice INJURIES BY BLUNT INSTRUMENTS. 413 compresses are to be used. In case the retina is completely pro- lapsed on account of loss of vitreous, and if light sense is destroyed, enucleation of the eye should be performed at once. 2. INJURIES BY BLUNT INSTRUMENTS. Severe pressure on the eye may have manifold results. Most of these results I had a chance to study in a case recently treated by me, and I therefore substitute a description of this case in place of a systematic relation of these results. A workman was injured by a severe blow from a heavy chain, On the next day the appear- ance was as follows: there was a gaping, horizontal skin wound above the tear sac; the eye was red, weeping, painful, photophobic ; there was a small conjunctival wound on the nasal side of the cor- nea, the vicinity being ecchymosed; the cornea, particularly below, was both diffused and linearly opaque; the anterior chamber deep; the pupil dilated and motionless—zridoplegia (p. 280); at the edge of the pupil upward and inward there was a small laceration; with focal illumination the lens reflexes were not visible, but the gray lines of light (f. zoo), although very weak, were yet evident enough to prove the presence of the lens; the fundus was invisible, no red reflex being obtainable in the pupil. MV = Fingers at 0.5 m7. After several days the cornea cleared, the irritation subsided, and a second examination showed new discoveries. The nasal half of the iris trembled when the eye was moved—zrizdodonesis ; it was also translucent. The posterior layer of the iris (the pigment layer) had obviously been loosened from the anterior; a remnant of this poste- rior layer hung in the pupil like a loose strand upward and inward, but behind the plane of the iris. The lens reflexes were now visi- ble, the lens being plainly displaced toward the temporal side. The lens trembled when the eye was moved. Some weeks later the eye was nearly, though not quite, free from irritation, the lens was totally opaque, still more displaced and mov- able, and at the same time so revolved on its perpendicular axis that its anterior surface faced toward the nose. The eye was blind beyond mere light perception. There quite gradually developed other disturbances, such as at- tacks of pain and increased tension; at the same time peripheral light projection became uncertain. Rest in bed, bandage to both 414 INJURIES TO THE EYEBALL. eyes, and eserin seemed to remain without effect, and consequently the extraction of the lens was decided on. There was, of course, prolapse of vitreous. Healing progressed slowly ; even in the third week after the operation there was still vitreous in the somewhat contracted wound. In spite of this, douches of warm sublimate solution and abundant use of iodoform powder prevented all suppu- ration. In the fifth week the wound was completely healed, but the eye was still somewhat reddened and sensitive. V = Finger at 0.3 m. Two months after the operation the eye was quiet, but the pupil was shut off by a membrane, the eye blind beyond sensi- tiveness to light. If the effect of a dull instrument is still more powerful than in the above case, the globe may burst; this is generally associated with hemorrhage into the anterior chamber and vitreous. The rent in the sclera always lies parallel to the corneal margin and only a few millimeters from it, opposite the spot where the blow was received by the eye. It occurs most commonly upward, upward and in- ward, or inward, because the eye is least protected downward and outward, and is therefore most apt to be struck in this spot. The process of rupture may be conceived as follows: The instrument causing the blow increases the tension to such a degree that the fibers of the sclera yield at the weak- est spot; the rent takes place, therefore, from within outward. ‘The fact that the vicin- ity of the cornea shows itself to be the weakest depends probably on the direction of the scleral fibers, since the thinnest of the sclera lies, as is well known, somewhat further back, near the equator. The elastic conjunctiva does not necessarily tear as the sclera bursts. Through the opening in the sclera more or less of the con- tents of the eye prolapses—iris, ciliary body, retina, vitreous, and sometimes the lens itself. Ifthe injury occurred to an eye already blinded by a cataract, it may really be of advantage in encouraging the expulsion of the lens. As a matter of fact, cases have been observed in which an accidental blow removed a cataractous lens and thereby restored vision. It may be further mentioned that occasionally the whole iris is torn off at the ciliary margin and escapes from the eye through the scleral wound. Rupture of the eye is caused by blows from the horns of cattle, by falling upon hard, jagged objects, by blows from the fist, canes, or feet, and by similar accidents. The diagnosis of a scleral rent is easy. Either the iris has pro- lapsed into the wound, in which case, besides the wound itself and FOREIGN BODIES WITHIN THE EYE, 415 the iris lying in it, we see an aperture in the iris corresponding to the location of the rent; or the iris has not prolapsed, but the pupil is at least dragged in the direction of the rent. In all cases the eyeball has lost its normal tension ; it is soft. Prognosis is serious; many injured eyes become phthisical. Treatment consists in disinfection, bandage, and rest in bed. A prolapsed iris must be carefully cut off. If the case is not seen early, the iris may be allowed to heal in the wound, the prolapsed portion being destroyed later by the cautery. 3. FOREIGN BODIES WITHIN THE EYE. In every penetrating injury to the eye the question must beasked whether the injuring body—all or any part of it—remains within the eye. In many cases this may be unnecessary, owing to the nature of the accident or to the size and construction of the object. In other cases the answer is easy, since the foreign body may be seen with the naked eye or by means of focal illumination or the ophthalmoscope, either in the anterior chamber, in the lens, in the vitreous, or on the posterior wall; at times there are air bubbles on the foreign body, recognizable as dark, circular areas with a bright point of light in the center. In other cases the answer is very dif- ficult, either because the foreign body lies in a recess of the cham- ber, where it is concealed by the sclero-corneal covering, or because of the rapid opacification of the lens, or of hemorrhage into the vitreous, or of inflammatory exudate, or because the foreign body is located so near the ciliary body that it cannot be seen by the surgeon. In such difficult cases we must question the patient as to the manner of the injury, examine him carefully, and take all the cir- cumstances into coitsideration. There must always be suspicion of foreign body in the eye if, after an accident, there are pain, pho- tophobia, sensitiveness to pressure, and visual disturbance at one time, unexplainable by any visible, external injury. The suspicion increases to certainty if we can find changes in the eye which un- mistakably indicate a canal of passage for a foreign body. We must then examine for a canal of entrance, that is, for a wound or scar in the cornea or sclera. The size of this canal (it is often very minute) will serve as a hint as to the size of the foreign body, at 416 INJURIES TO THE EYEBALL. least in two dimensions. It may be incidentally remarked that the smaller the canal of entrance, the greater is the probability that the foreign body still remains within the eye. We must next look for an aperture in the iris, or in the anterior and posterior lens capsule. If this last can be demonstrated, the foreign body must obviously rest in the vitreous or fundus, since the active force of minute parti- cles is never sufficient to penetrate the eye’s envelopes a second time. Any particle, then, remains adherent or rebounds and sinks in the vitreous to the bottom; in such cases the point of contact in the fundus appears as a bloody or as a white spot. If the patient is not examined till traumatic cataract has already appeared, and the vitreous and fundus are invisible, the physician must content himself with examination of the field of vision, which may be of diagnostic value in spite of the opacity of the lens. Near the foreign body the retina will be incapable of functionating on account of the atrophy of the layer of rods and cones with the ex- ternal granules,’ and consequently the patient will not perceive the light from a candle when it is brought into an area of the visual field corresponding to the neighborhood of the injured area in the retina. The further fate of the eye—apart from the mechanical effect of the foreign body—is influenced by three factors :— (1) The location of the foreign body ; (2) Its chemical nature; and (3) Whether or not disease germs were adherent to the foreign body during the injury. If bacteria were introduced, the result would be an acute abscess of the vitreous passing into panophthalmitis or a subacute inflam- mation, according to the number and pathological character of these germs,—both ending in destruction and atrophy of the eye. Only when the foreign body remains in the anterior chamber, iris, or lens, is our art able, perhaps, to avoid the worst; if germs have reached the vitreous, even an immediate extraction of the foreign body will not help to save the eye. If the foreign body was aseptic, it may be tolerated in the lens in spite of its chemical effect—the result being traumatic cataract, but no necessary inflammation. Cases have been reported in which the removal of the lens revealed a small foreign body, the presence of 1 At least, such was the condition in a case under my observation. FOREIGN BODIES WITHIN THE EYE. 417 which was quite unsuspected by the patient. If the foreign body was of iron, the lens becomes a diffused yellow on account of the oxid of hydrogen; or there are rust-colored points near the foreign body. Splinters of lustrous metal are easy to recognize, even through an opaque body, on account of their bright reflex. In the vitreous and in the fundus uncontaminated bits of iron or copper may retain lodgment, even if the eye at first was more or less irritated. Moreover, even in these favorable circumstances changes in the fundus may take place in a quiet way, especially at the macula lutea, and vision may be damaged. It must be finally mentioned that even if the eye remains absolutely quiet, a foreign ‘body is a veritable sword of Damocles, threatening its own and the other eye, too. The ciliary body is the most sensitive. Foreign bodies chemic- ally unirritating and free from germs may here produce an alarm- ing inflammation. From what has been said it is evident that for “a foreign body within the eye” the prognosis is extremely unfavorable. Left to themselves the majority of cases will end in destruction of one eye and sympathetic inflammation of the other. The prognosis is bad even with proper treatment. An analysis by Weidmann of the cases under Horner and Haab showed the following proportion of losses :— If the foreign body is in the anterior chamber,. ........ o per cent, If the foreign body isinthelens, .. 1... 1. eee we ae 30 per cent. If the foreign body is in the vitreous,. .... 2... ....4. 71 per cent. The prognosis is particularly bad in the case of bits of iron which are chipped off old and fragile instruments used when working ina stony soil and which have lodged in a workman’s eye. The loss in such cases is about 85 per cent. Treatment. Since a foreign body has often enough been seen to find lodgment without causing harm, it is not necessary that every foreign body known to be within the eye must be without ceremony attacked by an operation. It is better to weigh the chances for healing with the danger of the operation. When the foreign body is in the anterior chamber the danger of the operation is slight; consequently it should always be removed, even if long, unirritating residence seems to confer upon it the rights of citizen- 1 The danger may be slight, but not the operation itself! This operation, with that . for the removal of bits of iron, are among the most difficult of ophthalmic surgery. 27 418 INJURIES TO THE EYEBALL. ship. A lens with a foreign body in it must be sooner or later removed on account of the opacity, the foreign body being then extracted with it. The treatment of foreign body in the vitreous depends upon the material composing it. If—as is the case in the majority of such injuries (74 per cent., Weidmann)—the foreign body is of iron, the hope of a cure must be abandoned and imme- diate resort must be made to an operation which, at the present day, has become a comparatively easy and mild one, thanks to the use of the electro-magnet. If the foreign body was a splinter of copper, wood, stone, glass, or china, an inactive treatment may be followed. If the eye does not calm down the sclera should be incised, and through it an attempt made to seize and to draw out the foreign body with forceps. If this is unsuccessful the eye must be removed to avoid danger to its fellow. The credit of introducing the magnet into ophthalmic practice belongs to Hirschberg. His method has already saved innumerable eyes that would have been lost without the <«magnet operation.’’ The conditions for a successful result are : — (1) An accurate localization of the foreign body ; (2) Careful antisepsis ; and (3) An absolutely quiet patient, obtained usually by chloroform narcosis. The approach to the foreign body is obtained either by the magnetic sound, that is, by pushing through the canal of entrance a sound armed with an electro-magnet as the most usual method—by making a meridional scleral incision at the equator and near the for- eign body, through this introducing into the vitreous a properly shaped probe with elec- tro-magnet attachment which must be brought into contact with the foreignbody. If this can be done, or even if the magnet attachment can be brought near enough to the iron, the latter is attracted to the magnet with appreciable force and sound. Haab has quite recently devised a new magnet operation. It depends upon the fact discovered by Knies that by simply bringing the eye into the vicinity of a very strong electro-magnet a bit of iron can be drawn from the vitreous into the anterior chamber, where it may be released in a suitable position and then delivered by a comparatively harmless operation. With Haab’s electro-magnet a bit of iron may even be quite with- drawn from the eye in the tract of the entrance canal, this succeeding, too, as I have myself observed, even when the entrance canal had been closed for several days. Of course the very strongest magnet cannot draw a bit of iron through the intact membranes of the eye. It should be remembered, too, that the iron must not have become lodged in the sclera, nor be retained any place by inflammatory products. 4. SYMPATHETIC INFLAMMATION OF THE EYE. In many cases of injury to an eye the history of the trouble does not by any means end with the injury to or even loss of the eye first involved. It may rather begin the last and most distressing SYMPATHETIC INFLAMMATION OF THE EYE, 419 chapter, the passage of the inflammation to the other eye, sympa- thetic ophthalmia. This consists of a plastic cyclitis or iridocy- clochoroiditis (p. 286). It may be the result of a cyclitis in the other eye from some other than a traumatic origin, but such cases are rare. Usually it is an injury to the ciliary body, or a scleral wound into which ciliary body and iris have prolapsed and become incarcerated—but especially a foreign body within the eye, which causes a chronic cyclitis in the first eye and a subsequent sympa- thetic inflammation in the other. Other diseases also may arise sympathetically, particularly iritis serosa, which is in no way so serious as the sympathetic iridocyclitis plastica. There have also been reported cases of choroido-retinitis, and even diseases of a non-inflammatory nature, such as spasm of the orbicularis and optic-nerve atrophy, ascribed to ‘‘ sympathy ;’’ whether justly so or not is still an open question. The interval of time between the injury and the outbreak of the sympathetic affection is quite indefinite; it usually amounts to four to eight weeks, but cases have been reported serteex days after, and twenty-six or even forty (?) years after ! The disease is announced by premonitory symptoms—moderate photophobia, reduced strength for near work, cloudy vision. Corre- sponding to these symptoms there are a mild pericorneal injection, moderate opacity of the aqueous, and, perhaps, some kind of poste- rior synechia; redness of the disc has been occasionally observed. Gradually these signs of sympathetic irritation pass into those of sympathetic inflammation, the pain and cloudiness increasing, vis- ual acuity decreasing. The internal tension is changed, being at the commencement of the disease noticeably increased, but declin- ing below normal as atrophy begins. It is the rule that after varying improvement and relapse the pupil is displaced by adhesions, the iris adheres to the surface of the lens capsule (f. 287), the vitreous atrophies, the retina pro- lapses, and incurable blindness results. A cure with indistinct vision may be obtained. The nature of the inflammation is not yet explained. Mackenzie, who first described sympathetic inflammation, supposed that it passed from the retina of the injured eye through the chiasma to the retina of the other eye, and that it became now an “iritis sympathetica.’’ This old and rejected view has been recently brought again into promi- nence by Leber and his pupils. Deutschmann thinks he has proved that germs have traveled from the injured eye backward along the optic nerve, have reversed their course at the chiasma, have ascended in the lymph channels along the optic nerve of the other side, and thus caused the direful inflammation in the second eye. This doctrine, so clear 420 INJURIES TO THE EYEBALL. to the mere reader, has found many doubters. In numerous cases of sympathetically dis- eased eyes, examined with the greatest care, no germs could be found. Moreover, it has been shown that all sympathetic inflammations caused by him with bacteria were but a local manifestation of a general infection of the entire animal. In short, Deutschmann’s theory has not as yet been able to depose the hitherto ruling one that the second eye was in some unknown way involved through the ciliary nerves. To be sure, we have no con- vincing proof of this theory, but a series of clinical facts that are in accord with it are un- explainable on the Mackenzie-Deutschmann theory. For example, the fact that sympa- thetic irritation may develop within a few minutes, and that a foreign body on the cornea of one eye may arouse photophobia and injection of the uninjured eye, and that if the tear passage of one eye is sounded and some difficulty is met in reaching the meatus, the eye on the same side becomes red, while the other eye is similarly, although to a less ex- tent, affected. A second indication is the fact that the inflammation in the eye sympathetic- ally affected is at times restricted to exactly the same place which in the first eye was injured or sensitive to pressure. A third indication, observed by Mayweg and Schmidt- Rimpler, is the fact that the sympathetically affected eye becomes at once red if the first eye is pressed on. And, finally, the ciliary nerves would seem to be involved by the fact drawn from experience, that atrophic cicatrices of the ciliary body and atrophic deposits dragging on the ciliary body are particularly prone to produce sympathetic inflammation, while there seems little to be feared in suppuration of the eyeball, in spite of the active bacteria present, presumably because the ciliary nerves are at the same time destroyed. Again, atrophy or even excision of the optic nerve appears to offer no absolute protection against sympathetic inflammation so long as any of the ciliary nerves remain, Treatment must begin by interrupting the nervous connection between the eye first involved and the one sympathetically affected. This can be accomplished in two ways :— (1) By cutting the ciliary nerves. This was proposed originally by v. Graefe, his plan being to sever only the ciliary nerves sup- plied to the injured area and then only from within, by introducing a knife through the membranes of the eye. The operation has found little favor. Snellen has found more followers; he severed the ciliary nerves before their entrance into the eyeball and by this means overcame pain otherwise unbearable. In operating he loos- ened an eye muscle, passed the scissors to the back of the eye, and cut something near the optic nerve, hoping to be fortunate enough to include the proper ciliary nerves in the incision. If it is desired to sever all the ciliary nerves before they enter the eye the optic nerve itself must be cut through—wewrotomia optico- ciliaris. If the theory of inflammation through or along the optic nerve is accepted, a mere cut through the optic nerve will not suf fice, but a piece of it must be excised—xeurectomia opticociliaris. To perform this operation the internal eye muscle must be detached, the eyeball rolled energetically outward, the scissors glided along the sclera till it reaches the optic nerve, which is then severed some SYMPATHETIC: INFLAMMATION OF THE EYE. 421 distance away from the eyeball. It is now possible to rotate the eyeball completely so that the posterior pole lies exposed in the conjunctival wound, when all the ciliary nerves entering at that place can be cut. The optic nerve stump still attached to the eye is now cut off, the eye replaced in its normal position, and muscle and conjunctiva sutured. These different methods of severing the ciliary nerves are not a trustworthy protection against sympathetic inflammation, because all the ciliary nerves do not enter the eye in the vicinity of the optic nerve, and consequently the sensitiveness of the eye operated on is not necessarily destroyed after neurotomia opticociliaris. To be quite sure, the second way must be followed—enucleation. (2) Enucleation of the eye first affected is the most serviceable, prophylactic, and curative remedy for sympathetic inflammation. It is easy to understand why patients should decidedly oppose this mutilating operation. If it is remembered, too, that it must, if pos- sible, be performed before sympathetic inflammation begins, if the desired result is to be obtained and that every iridocyclitis does not necessarily lead to sympathetic ophthalmia, we can see that it is one of the most difficult tasks of the ophthalmic surgeon to decide when and when not to resort to enucleation. The following rules may serve as guide:— (1) If the first eye is blind, painful, and sensitive to pressure, enucleation is to be advised; it is to be urged, if the patient lives away from a surgeon, and thus may be in danger of overlooking the beginning of sympathetic inflammation. If the patient will not consent, he should be told to seek aid at the first sign of visual disturbance or of inflammation in the other eye. (2) If the first eye has a foreign body, is painful and sensitive to pressure, enucleation should be urged even if the eye sees; it is to be supposed, of course, that the foreign body cannot be removed independently (/. 477). (3) If sympathetic irritation or even inflammation appears in the second eye the first must be enucleated at once. If the first eye is not blind but still retains a certain visual acuity and is to some extent quiet, both patient and surgeon will hesitate at such radical proceedings. There is, however, no general rule for such a case; we must carefully compare the visual acuity of the first eye with the degree of irritation in the second ; the more there remains to rescue in the second eye the greater price can be paid by the first. Against fully developed sympathetic inflammation the physician is powerless. A late enucleation is usually of no effect and the inunction method so strongly advised by Wecker is designated by others (Michel)as of novalue. Under such circumstances we must be content to prevent new accidents, to lessen pain by cocain, warm compresses, and to use similar symptomatic remedies. There may 422 INJURIES TO THE EYEBALL. be some hope for the subconjunctival sublimate injections so warmly recommended by French and Italian confréres. My own experi- ences have not been encouraging. Hydrargyrum oxycyanatum has been warmly praised for this purpose in solution of z + 5000. Whrether it is better than sublimate, or better than a quite indifferent solution (the physiological chlorid of sodium solution), is not as yet decided. Months or years must elapse after all inflammatory phenomena have subsided before operations such as iridectomy or cataract extraction can be considered. Noticeable increase in tension forms an exception. If this is present (at the beginning of sympathetic inflammation) repeated corneal punctures or iridectomy may be performed in spite of the inflammation. Fnucleation of an eye is mutilation. The patient should, there- fore, wear an artificial eye of glass or celluloid, which often is so like the real eye that even the nearest associates of the patient may not be aware of the deformity. This glass eye should be movable, since the muscles ought not to be injured in enucleation. The tendons of three recti muscles are separated from the bulb, the eye is then turned around so that the optic nerve can be reached by the scis- sors, the eyeball is luxated and the three remaining eye muscles cut off. These six eye muscles form, after healing, a flat stump covered with conjunctiva, which follows all the movements of the healthy eye and transmits them to the artificial eye resting upon this stump. Ifthe movements of the healthy eye are extensive the artificial eye lags behind, but extensive movements are usually not resorted to. To aid still further the associated movements of the artificial eye, exenteratio bu/bi has been substituted for enucleation. This consists of scooping out the eye, so that cornea, lens, vitreous, uvea, and retina are removed, leaving sclera behind. The cavity closes, and a stump, consisting of scar-tissue, sclera, and muscles, remains. The stump is still better if, after scooping out the eye, an “artificial vitreous” of glass or unoxidizable metal is introduced and allowed to heal in place. Exenteration with the use of an artificial vitreous is, however, so new that at present it is still doubtful whether the cosmetic effect is not purchased at the cost of lessened security against sympathetic inflammation. An artificial eye must produce no discomfort, and the stump particularly must be kept from irritation. Irritation of the stump by an artificial eye has led to sympathetic inflammation of the other eye. At night the artificial eye must be taken out and placed in water. APPENDIX. 423 APPENDIX. The question is often raised after injuries to the eye, how much the injured person is harmed in his ability to earn a living. Accord- ing to the effect on such ability is the compensation to be paid the injured person estimated. If, for example, the injured person suf- fers a loss of 30 per cent. of his working power, and has therefore been injured 30 per cent. in his wage-earning capacity, there should be paid him for the remainder of his life 30 per cent. of his wages (income) as compensation. It is a very difficult task to estimate the injury to wage-earning capacity, because there must be taken into account a number of factors which cannot be measured, but can only be guessed at. The most important factor is, of course, the amount of injury to the two eyes. It must be mentioned at the outset that a mere in- jury is not of itself a justifiable claim for compensation; the injury must be of such a nature as to hinder the patient from pursuing his vocation. It stands to reason that an injury to the visual organ may, in certain vocations, impair the wage-earning capacity, while the same injury may be no drawback to a man in another profes- sion. Itis, therefore, necessary to consider also the optical necessi- ties of the vocation followed by the injured person. Seamen, rail- way employés, mechanics, and those in technical trades, require greater refinement of vision than do day-laborers, miners, coopers, millers, brewers, drivers, etc. Even workmen of the first group have no need for absolute V = 7 in order to be perfectly capable in their vocation. Again, a workman of the second group with possible V = = is completely incapacitated, while a workman of the first group is incapacitated with V no lower than ~~, or even > The damage done to the eyes themselves is a product of three factors :— (1) Visual acuity, (V) (2) Visual field, (6) bana any impairment to them. (3) Excursional field, (2 ) Of course, visual acuity is of more significance for the wage-earn- ing capacity than is the visual field or the excursional field. Con- sequently, each one of these three factors is of different weight in the estimation of damage done. Finally, account must be taken of a fourth (but minor) factor, namely, that a workman finds it less easy to obtain employment after it is known or recognized that his 424 APPENDIX. eyes have been injured. Many factories will not under any circum- stances employ a one-eyed man, although with his one eye he may be able to satisfy all requirements of his trade. The problem just examined has been mathematically presented in the following formula :— 4 x B=VVGXVBXVK £ signifies the earning capacity. V signifies the visual acuity. G signifies the visual field. B signifies the excursional field. £ signifies the competitive element, that is, the capacity for obtaining a situation in the labor market. All these values are either equal to unity (Z = 1), that is, the injured person is not permanently impaired; or he is impaired in working power, and then the values all become real fractions. V . is the most important factor and has no root sign; the other three quantities are represented with increasing root signs proportionate to their decreasing grade (value), since the root of a real fraction approaches closer to unity (that is, it has less influence on the pro- duct £) the higher its root sign. By means of this formula Magnus has worked out a large series of cases of damage through injury. From his results I present in modified tables such cases as are of most common occurrence. Loss of earning power, ove eye being damaged, the other unaffected :— Loss OF WoRKING POWER In vocations demanding tn vocations with but slight V. oF THE DAMAGED EVE. great technical skill and need of acute viston. hence acute vision. 1:0.75 O. per cent. Oo. per cent. 0.7 a4 °. “s 0.6 Tyg. oO. es 0.5 2.3. ts °. oe 0.4 3.4 “ 1.2 0.3 YAO “SES 2.5 et 0.2 6.0 « 4.0 a 0.15 67 4:8 Less than 0.15 Th. * — <«* Less than 0.05 & 15.6 « oO. 31. oe 27. “ APPENDIX. 425 Loss of earning power, ove eye being blind, the other damaged in visual acuity. Technical vocations demanding acute vision :-— V. Loss oF EARNING Power. 0.7 37.8 per cent. 0.6 51.0) « 0.5 63.8. V4 75.8 « 0.3 86.9 « 0.2 96.5“ o.1 100.0 «* LOSS OF EARNING POWER IF THE VISUAL ACUITY IN BOTH EYES HAS SUFFERED; TECHNICAL VOCATIONS DEMANDING ACUTE VISION :— V. of one eye. the other Ito 0.75 0.6 | 4 0.2 eye. : Y | 1 to 0.75 ° 1.3 | 3.4 6 : 5 = ° a 0.6 1.3 27.1 | 29.0 31.3 B ! q . 5 5 0.4 3-4 29.0 61.8 63.7 2 ° Sod ° ws ae 6.0 31.3 637 93-5 DISTURBANCES IN THE MOVEMENTS OF THE EYES.' 1. STRABISMUS PARALYTICUS (Paratytic Sguint). 1. DIAGNOSTIC SIGNS. Those who seek aid for paralytic squint are nearly always adults. They complain, as a rule, of vertigo and diplopia (double vision). 1 To understand this section, an accurate knowledge of, or repeated reference to, Section v., p. 70 ef seg., is indispensable. 426 DISTURBANCES IN THE MOVEMENTS OF THE EYES, The vertigo is the result of a false projection (f. 77), and is con- sequently present only when using the diseased eye. The double vision is the result of the squinting position (/. 72), and, like this position, is present only in those areas of the visual field to reach which the paralyzed muscle must be called into play (/. 85). In many cases double vision is rather masked. The patient complains that objects appear indistinct in some positions, and that at such times he has a feeling of discomfort. This depends upon masked diplopia, and implies that the patient has been at an earlier period accustomed to give particular attention to the images of only one eye, and that, con- sequently, the double images do not make a proper impression on his consciousness. By using a colored glass it is generally easy to change such a masked diplopia into clearly perceived double images (/. 87). The complaints of the patient differ, according to whether the loss of muscular power is complete (paralysis) or incomplete ( faveszs); and according to the importance of the Fic. 151.—-Tue Eve Muscies SEEN FRoM IN Front. (A/ter Merkel.) diseased muscle for covering particular areas of the visual field. In reading and writing, for example, paralysis of a muscle involved in movement to the right (rectus internus of the left or rectus externus of the right eye) causes far more disturbance than paralysis of the muscle involved in movement to the left; in going up stairs (in all motion, in fact), paralysis of the depressor muscles (recti inferiores and obliqui superiores) causes more disturbance than paralysis of the elevators (recti superiores and obliqui inferiores). Often, in looking at a patient making such complaints, an oblique position of the head may be noticed. The patient soon learns, when looking at objects in front of him, to use a position of the eyes in which as little demand as possible is made upon the paralyzed muscle. If, for example, the left rectus externus is paralyzed, the patient turns his head toward the left; his eyes must, therefore, make a compensatory movement toward the right in order to look DIAGNOSTIC SIGNS, 427 straight ahead. Ifa superior rectus is paralyzed, the patient throws his head back in order to bring his eyes under the control of the depressor muscles, the recti inferiores and obliqui superiores. These positions of the head are so significant that of themselves they may betray the condition to the experienced observer. A long con- tinuance in such positions of the head may cause contractures of the neck and back muscles. Cases are reported in which stiff neck (torticollis) has been treated in vain, until the cause for the stiff neck was discovered to be an eye-muscle paralysis. In making a diagnosis it is of the greatest importance to be sure that the double vision is not confined to one eye (f. 358); in such a case, of course, double vision remains when the other eye is closed. It must be further tested to see that the disturbance in movement does not depend on some simple external cause, as a pterygium, a collection of pus or blood, or some new growth be- hind the eyeball. If such causes can be excluded we may assume the squint to be paralytic and try to find out which is the paralyzed eye. In pro- nounced cases a simple test of the excursion of movement in each eye will suffice (p. &5), since the recognition of a lapse in either eye proves that thiseyeis diseased. Butin other cases this method of examination gives no exact results,—either because the paralysis is not complete, and consequently the lapse of movement is too small, or because the paralysis involves muscles, the obliqui, for example, which are of minor importance in performing the visual excursion. In such cases the position of the other eye remaining covered must be compared with the position of the fixing eye. If, for example, the rectus externus of the left eye is half paralyzed and the eye in consequence is unable, even with the greatest effort, to follow to the normal limit of its excursion a finger moved in front of it toward the left, the right and covered eye will pass into the position of extreme adduction and its visual line will finally aim toward the left of the finger followed by the left eye. This is a proof that the same impulse of the will affected the externus of the left eye less than it did the internus of the right eye, and that, therefore, the left is the eye paralyzed. There results from this the general rule that “the more squinting eye is the healthy eye,” because when the diseased eye looks toward the side of the para- lyzed muscle, the healthy eye passes into the deviation of squint (p. 85), which is greater than the primary deviation which the dis- 428 DISTURBANCES IN THE MOVEMENTS OF THE EYES. eased eye assumes if the healthy eye fixes. A further sign is given by the fact that the vertigo ceases when the diseased eye is closed. This sign may have been noticed by the patient, who is accus- tomed, therefore, to squeeze his bad eye shut. To be sure this is not always the case, for it may happen that the diseased eye pos- sesses the better visual acuity, in which case the patient neglects the unparalyzed eye and fixes with the paralyzed one, attempting, meanwhile, to protect himself against false projection of images and the vertigo accompanying it by moving his head. If these meth- ods still leave the diagnosis uncertain, we must resort to the double image test as explained by the rules given on ff. 87, 433. The diagnosis must now be extended to the detection of the paralyzed muscle or set of muscles. This task, so easy in some cases, may in other cases be one of the most difficult in the whole extent of ophthalmology or neurology. In one instance several muscles of one or of both eyes may be paralyzed, in another in- stance the paralysis may attack eyes in which the muscle balance has already been previously disturbed. Finally—a frequent result, too— when the paralysis of one muscle is of long standing, there develops a secondary contraction of its antagonist. It is evident that to keep all these circumstances clear in one’s mind must be an extremely difficult task. We can now examine the simplest cases, namely :— (a) Isolated paralysis of a rectus externus ; (4) Isolated paralysis of an obliquus superior ; (c) Paralysis of the muscle group supplied by the nervus oculo- motorius. These three cases are the commonest and the most practically important. The reason for this will be explained in the discussion of causes. In A. Graefe’s rich experience of eye-muscle paralyses the following were the usual percentages in each 100 cases :— 32 per cent. isolated paralysis of a rectus externus ; 16 per cent. isolated paralysis of an obliquus superior ; 8 per cent. isolated paralysis of one of the four remaining muscles ; 44 per cent. combined paralysis of all these four remaining muscles in one or both eyes. (a) Paralysis of the Left Rectus Externus.!—The patient holds his head to the left. If his right eye is now closed and if he 1 For simplicity’s sake I shall describe a left-sided paralysis in each instance. The student can make out a right-sided paralysis by changing the words in the text. PARALYSIS OF THE LEFT RECTUS EXTERNUS. 429 is asked to walk rapidly about the room, he will grow dizzy enough to fall. Ifa finger is then held toward the right} and if he is asked to fix this finger, both eyes take the proper position with refer- ence to it; but if the finger is now moved over the median line of the patient toward the left, his left eye remains still, or moves only in a jerky manner, with alternate rotatory movements in opposite directions, upward outward and downward outward, this being the result of the contraction of the two obliqui, which are vainly endeav- oring to act in place of the paralyzed externus. The farther the finger passes to the left, the more evident is this lagging behind of the left eye and the accompanying position of convergence caused by it. Fig. 152 illustrates the position of the double images for nine \Ymards bo theleie| Gp to Ue left | 58 aheu| tb the righe othedeftciwnmards| _ downmands cal Fic. 152.—Dousie Imaces 1n Paratysis oF THE Lert Recrus ExTERNUS. A Red mark is the image of the Right eye; a bZue mark that of the Left eye. The words on the chart indicate the areas of the field of vision. different areas of the visual field; they appear as they would to the reader if his left rectus externus were paralyzed. It will be seen that the line separating the field into two parts—one containing double images, the other a single image—is not perpendicular but runs from above and to the left downward and to the right. This depends on the fact that, when looking upward, convergence is phy- siologically favored, and when looking downward, divergence is so favored. This fact is explained by the habit of looking at distant objects with the eyes somewhat raised, but at near objects, the book, for example, with the eyes lowered. It may be added that occasionally a moderate obliquity and inequality of elevation in the two images is admitted. 1 Right and left always refer to the patient. 430 DISTURBANCES IN THE MOVEMENTS OF THE EYES, If the paralysis is incomplete, the dizziness may be quite pre- vented by the patient’s turning his head to the left. The left eye follows the finger more or less toward the left past the median line of the body, but the external edge of the cornea cannot be brought to the outer canthus. If this lapse is too small to establish a diag- nosis, the physician must observe the secondary deviation of the healthy eye, which seemingly exaggerates the disturbances of movement in the diseased eye. The line separating the visual field into parts of single and double images lies rather more to the left than in Jag. 752, in the minimum degree of paralysis the double images may quite escape notice, since by an unequal inner- vation of the two muscles involved in movement toward the left (stronger impulse to the left externus, weaker to the right internus) Qpmarts to the left. Gpraras — \Oprevds loterght! | | | bo the left, serughl lhe right. il ee 2 Fic. 153.—DovusLe IMAGES 1n PaRALysis OF THE LEFT Ostiquus EXTERNUS. A Red mark is the image of the Right eye; a bZue mark that of the Left eye. The words on the chart indicate the areas of the field of vision. a fusion of the images may be accomplished. The desire to fuse, and the range of fusion, differ in different cases. If we wish to make the position of the eyes independent of fusion, we should use a prism, base downward or upward, held before one eye. Fusion will now be impossible, and a latent separation of the images will be easily discovered. (2) Paralysis of the Left Obliquus Superior.—The patient turns his head downward toward the right, that is, about an axis running in the same direction as the line (/zg. 753) separating the field into two parts, from below to the left upward to the right. He thus brings the upper left part of the visual field immediately to the front, this part being usually but little used. This position of the head is therefore particularly noticeable, and is diagnostic of paralysis of the trochlearis. PARALYSIS OF THE LEFT OBLIQUUS SUPERIOR. 431 The restriction in movement is much smaller than in paralysis of the rectus. It is best demonstrated, however, by moving the finger downward and to the right, into the lower right ninth of the visual field; in this case the eye cannot follow the finger; the eye is too high. To understand this, the student should refer to Fig. 27 (p. 78). It will be noticed that if the left eye is rotated sufficiently to the right, the horizontal axis, that is, the axis of rotation for depression, forms a right angle with the direction of traction of the tendon of the superior oblique muscle; consequently to effect a sufficient turn to the right in the left eye, the superior muscle must become a pure depressor. Since the lower right area of the visual field can be reached only by means of the left superior oblique, a paraly- sis of this muscle must cause the left eye to remain the furthest away from this position. The condition is reversed in looking downward to the left. In this direction the rotatory muscle be- comes purely a muscle for circular rotation, and consequently a paralysis of it has no influence upon such available positions of the visual lines. Double images are of particular importance in overcoming the difficulties encountered in perceiving and measuring any restric- tions in movement. They are illustrated in /zg. 753, and corre- spond to the position of the eyes in the diagram. In looking to the right there is seen a difference in elevation, which increases as the candle (the test fixation-point) is lowered. In looking down- ward to the left there is seen the greatest obliquity, an evidence of rotatory movement exaggerated in an eye in which the inferior oblique has lost its antagonist. The image is moderately depressed and removed to the side. In looking straight ahead or directly downward, there is obliquity, depression, and removal to the side, the last condition allowing the recognition of homonymous double images. Since the superior oblique muscle causes abduction as well as depression and rotation, its paralysis must result in adduc- tion or a position of convergence. Many patients assert voluntarily that the lower image—belonging to the diseased eye, therefore,—appears nearer and, perhaps, smaller than the image of the healthy eye. The smallness of the image is to be taken as the result of its apparent nearness. We may decide that two retinal images of the same size belong to two objects of different sizes, in case we choose, for one reason or another, objects at different distances (compare p. 288). The apparent nearness of the image is itself not yet satisfactorily explained, and the views of various authors are not harmonious. ‘Two facts in this connection may be mentioned : first, that the nearness of the lower image is not apparent in trochlear paralysis alone, but 432 DISTURBANCES IN THE MOVEMENTS OF THE EYES. may be produced artificially in the higher image by means of a prism, or displacement of the eye with the finger; and, second, that the surroundings of the double images have a distinct influence on the lower image. For example, a ball hanging on a thread appears as two images exactly over each other, while the same ball on a plate appears as two images, one in front of the other. (Vagel’s experiment.) If the paralysis is incomplete, the obliquity of the images or the restriction in movement will not be evident, or will be demonstra- ble only in the lower right corner of the visual field. The diag- nosis depends then exclusively upon the double images, that is, upon double vision, with predominant elevation to the right below, and with predominant obliquity to the left below. (c) Paralysis of the Muscle Group supplied by the left Ner- vus Oculomotorius.—Aecius supertor and inferior, rectus tnler- nus and obliquus inferior. The recognition of this pathological condition is easy, since a complete paralysis of so many muscles must produce appreciable disturbance. The position of the two eyes when looking straight ahead is one of divergence. The movement of the diseased eye inward, upward and downward, is prevented ; movement outward (to the left) and outward downward (downward to the left) is still possible with the rectus externus and obliquus superior. Consequently, divergence increases decidedly when look- ing toward the right. When the eyes are directed upward there is depression—when downward, elevation—of the diseased (left) eye. In an incomplete paralysis, on the other hand, the visible defects of movement are less apparent, and the diagnosis must be made from the location of the double images. As Fig. 754 shows, these are crossed; in looking upward the image of the left eye is higher, in looking downward, lower, than the image of the right eye; but the difference in elevation is less in looking downward than in look- ing upward, because one of the muscles concerned in depression, the superior oblique, is not affected. The distance between the two images increases in looking toward the right, and disappears in a small area of the visual field lying to the left and below when look- ing in that direction. There is also obliquity of one of the images, but this is usually noticed by the patient only when the images are close together, as in looking directly outward or downward, or to- ward the left downward. In the majority of cases, even in those of hemiparalysis, the diagnosis is essentially simplified through the involvement of other muscles. To make this clear we must understand and apply what SECONDARY CONTRACTURES, 433 is said further on concerning the nature of eye-muscle paralysis,— that in the great majority of cases the condition is of disease of the nerves rather than of the muscles. Since the nervus oculomo- torius supplies a lid muscle, the levator palpebrz superioris, and two internal eye muscles, the sphincter iridis and the musculus ciliaris, as well as the four external eye muscles already mentioned, the typical pathological picture is the following: The upper lid droops and its horizontal folds are obliterated ; if the lid is elevated, the pupil of the diseased eye is found to be moderately dilated and irresponsive to any of the three methods of stimulation ( . 269)— it is rigid. The power of accommodation is lost, causing more or less disturbance of vision according to the refractive condition. When looking: Ypomards to the lef¢. Opwurds pvards nt Oe apt a fo the left. fo the right an | aa ||Ote Ze a a es Fic. 154.—PARALYSIS OF THE LeFT OcuLomoTorivs. A Red mark is the image of the Right eye; a bZue mark that of the Left eye. The black mark is the single image for thé two eyes. Athereitt. B There is some exophthalmos, because three of the four recti muscles which draw the eye backward are paralyzed. The general rule for determining a paralyzed muscle may be deduced from what has been said: place a candle in each of the above-mentioned nine areas of the visual field and ask the patient, his sound eye being particularized by having a red glass disk in front of it, to fix this candle without turning his head. The patient’s responses as to the loca- tion of the double images are to be noted by a red and a blue pencil. From a diagram thus made it is not difficult to form a diagnosis, provided that the action of each muscle (2. 76) is known and that the case is a fresh and uncomplicated one. But since there are some patients in whom the distinct type of an eye-muscle paralysis is obscured, the most important complications need a short analysis. (a) Secondary Contractures.—If the paralysis has lasted some time, the antagonist of the paralyzed muscle is accustomed to drag the eye more and more to its own side, even in a condition of rest, and ‘secondary contracture’? is the result. Consequently, squint and diplopia are present even in those areas of the visual field in which the paralyzed 28 434 DISTURBANCES IN THE MOVEMENTS OF THE EYES, muscle isinactive. If, for example, in the above case of paralysis of the left rectus externus, a contracture of the left rectus internus had supervened, the line separating the visual field into its two parts of areas with and without double images would lie farther to the right or, perhaps, would fall quite at the edge of the visual field; and in the left part of the field the double images would be wider apart than before. The differential sign in the association of paralysis of the left externus with contracture of the left internus depends upon the fact that in looking toward the left the double images flit apart in the left half of the visual field, while in looking toward the right the same distance is maintained in the right half of the visual field. (8) Preexisting Disturbance in Equilibrium of the Muscles.—If a patient suf- fering from latent squint (/. Sg) is attacked by paralysis in the muscles of one eye, the latent squint will change into manifest squint for that part of the visual field in which binocular fusion is now rendered impossible on account of this muscle paralysis. In this case the location of the double images is influenced both by the paralysis and by the latent squint. For example, if a weakness of both internal recti (lateral divergent squint) is associated with paralysis of a depressor muscle, there will be crossed double images in looking downward, irrespective of whether it is the inferior rectus (with its adduction) or the superior oblique (with its abduction) which is paralyzed. For the slight convergence that may be expected as the result of paralysis of the oblique as abductor will be more than neutralized by the preexisting latent, divergent squint now become manifest. How can we distinguish in such a case whether the rectus inferior or the obliquus superior is paralyzed? Now can we be sure whether actual latent squint is present ? The first question is answered by the statement of the fact that the mode of action of an inferior rectus and of a superior oblique is subjected to exactly opposite changes in adduc- tion or abduction of the eye. (See Fig. 27, ~. 78). By a definite movement of the eyes toward the right the rectus inferior of the left eye becomes a pure muscle of rotation and the obliquus superior a pure depressor ; by a definite movement of the eyes toward the left the rectus inferior becomes a pure depressor and the superior oblique a pure muscle of rotation. Consequently, if the candle is moved to the right and then down- ward, the difference in elevation between the double images increases when the obliquus superior is paralyzed, but decreases if the rectus inferior is paralyzed. No attention need be paid to the obliquity of the double images, since the statements of the patient are quite untrustworthy and since the elevation of the images will differentiate as completely as will be necessary. The second question is answered by using a prism before one of the eyes, base down- ward or upward. By this means the desire to suppress the latent, divergent squint is overcome for the upper half of the visual field, and the double images will, therefore, appear in this upper half as well, but obviously without difference in elevation. Paralysis of all the external eye muscles is called, since Mauth- ner, ophthalmoplegia exterior, while paralysis of the sphincter pupil- le and the ciliary muscle is termed ophthalmoplegia interior ; asso- ciation of both conditions is called ophthalmoplegia totalts. 2. LOCATION AND CAUSES. The optical symptoms of an eye-muscle paralysis can be produced by cutting one of the six muscles concerned in the eye’s move- ments. This has often enough been done, as a “myotomy” for LOCATION AND CAUSES. 435 the correction of squint. At the present day, when section of the tendon has displaced section of the muscle, it may yet occasionally happen that the effect of a tenotomy is too strong, and produces a paralysis or hemiparalysis of the incised muscle. In some cases the obliquus inferior is loosened by an accident from its origin—the lateral bony edge of the lacrimal fossa—and is then in reality par- alyzed. We may, however, pass over such cases recognizable by the history or by an external scar, as well as other cases due to hemorrhages, inflammations, or new growths in the orbit, all of which may lead to restriction ineye movements. There still remains the majority of all cases of squint paralysis, in which there is no demonstrable lesion or disease of the muscles themselves; the cause for these must, therefore, be sought for in the nerves of the eye—the oculomotorius, the abducens, the trochlearis—or in their tracts in the brain. It may be mentioned here that an isolated lesion of the individual eye muscles is by no means impossible. Why is it not probable that the same process is at work in the orbit, which here and there affects individual muscles of the extremities and makes them pain- ful and destroys their function by rheumatism? Such a process, considering the inac- cessibility of the eye muscles, would, to be sure, be hard to diagnosticate or to differen- tiate from disease of the nerves. Assuming that a disease of the nerves is present, an exhaustive diagnosis must elucidate a three-fold problem :— (z) The spot in the path of the nerve which is incapable of func- tionating. (2) The nature of the disease-——whether the nerve is idio- pathically affected, whether it is involved in disease of adjacent structures, or whether it is merely mechanically implicated. (3) The ultimate cause of the disease, whether infection, intoxi- cation, or injury. Only in exceptional cases is it possible to demonstrate these three points with satisfaction. The first offers extraordinary difficul- ties on account of the very complicated path of the nerve in the brain, and since many questions of brain anatomy are yet unsettled, the description here given can be only an incomplete one. (z) The most important aid to exact localization of that portion of the nerve deprived of function consists in establishing the presence of other nerve paralyses not necessarily limited to the eye, and con- firmed by a careful examination made by the neurologist. As it may be assumed that such paralyses arise from the same focus in 436 DISTURBANCES IN THE MOVEMENTS OF THE EYES, the brain, we may localize the disease at the spot where the paths of the paralyzed muscles are close together. For example, if paraly- sis of the left abducens occurs with paralysis of the right arm and leg, we may assume a focus in the lower left portion of the pons, since in this spot the abducens for the same side of the body, and the nerves for arm and leg of the opposite side, lie close together. Localization in oculomotor paralysis is particularly difficult, since this nerve in its entrance into the orbit divides into numerous branches and twigs, and since it arises with many roots from its nucleus on the floor of the aqueduct of Silvius (fag. 773, p. 305). There is little difficulty if all muscles innervated by the oculo- motor are paralyzed and if play of pupil, accommodation, most eye movements, and elevation of lid are lacking. In such a case we may assume a disease of the origin of the nerve at the base of the brain. In rare cases a paralysis of all oculomotor branches is to be referred to disease of the nucleus in the medulla, but such a con- dition can be diagnosticated only by the course of the disease. The paralysis of the iris and ciliary muscle appears earlier or later than that of the external eye muscles. The nuclei for the pupil and for accommodation (/ig. 713, p. 305) are quite independent of the others in spite of their great proximity. According to Mauthner this depends upon the fact that these nuclei are nourished by differ- ent terminal arteries, and that the brain area nourished by each ter- minal artery is of itself a focus for an independent lesion. Ifaccom- modation and pupillary action are unimpaired we are, therefore, warranted in assuming an oculomotor paralysis to be a nuclear paralysis. Even if the diseased focus increases in dimension and if paralysis attacks all the external muscles of one or both eyes, those supplied by abducens and trochlearis included, the retention of pupillary action and accommodation warrants the diagnosis of nuclear paralysis, because in the nuclear region the individual ocu- lomotor nuclei are comparatively wide apart, while in the nerve itself all fibers are crowded comparatively close together. For the same reason Mauthner assumes a nuclear paralysis if the inner eye muscles—sphincter pupillz and ciliary muscles—are paralyzed, or if a definite movement, convergence, for example, is impossible. If a single muscle supplied by the oculomotor is paralyzed, we speak at once of nuclear paralysis. It is a question whether or not this is correct. The possibility of disease of the muscle itself has been already mentioned. By neglecting this, there are still other possibilities which must be thought of, especially since the latest investigations have LOCATION AND CAUSES. 437 shown that circumscribed groups of ganglion cells, so-called nuclei, may have the signi- ficance of functionating centers, that is, they may control certain movements through which different muscles are brought into play. This all indicates that a paralysis of con- vergence is a nuclear paralysis. But isolated paralyses of single muscles, say of the in- ternal rectus, may be otherwise explained. The following possibilities may be thought of :— (a) The nerve might be diseased close to the entrance into the muscle ; (4) The fibers to each muscle might be independently diseased in the nerve trunk; a condition well recognized by neurologists, who have frequent opportunity of observing that a toxic neuritis, such as lead or arsenic paralysis, attacks special fibers of a nerve trunk; (¢) The intracerebral roots of the nerve fibers and the ganglion cells belonging to them, though perhaps separated in space, might degenerate independently. Such a case, as well as the one mentioned under 4, might be designated ‘‘ systemic disease’’ in the physiological sense of the word. Whatever may be the conclusion about such possibilities, I am sure that the diagnosis —nuclear paralysis—has been used altogether too freely. Siemerling has recently pub- lished a case of ophthalmoplegia externa, in which anatomical examination showed the oculomotor nucleus normal, while the intracerebral roots, their continuation in the nerve trunk, and their terminal branches, as well as the muscles themselves, were all found diseased. Uhlhoff’s investigations also have shown that it is sometimes going too far when the conclusion is drawn from functional disturbances seen during life that there must be defi- nite anatomical changes. Uhlhoff has found at the autopsy that the oculomotor root at the base of the brain was the seat of the lesion, although only particular muscles of those supplied by the oculomotor were paralyzed during life; and in other cases the muscles supplied by the oculomotor functionated normally during life, although at the autopsy the oculomotor trunk was found diseased. The brain cortex or the track between cortex and nuclear region must finally be mentioned as a location for the lesion. Ifa diseased focus lies here, the condition is to be termed a “conjugate” or “associated” disturbance of movement, and not an eye-muscle paralysis in a restricted sense. This disturbance of movement con- sists of inability on the patient’s part to carry out those associated visual movements which respond to light stimulation, while the same visual movements may'be properly performed either volun- tarily, or through aural or tactile stimulation. As a rule, this con- jugate disturbance of eye movement shows itself as a conjugate deviation. An exception from this is the “cerebral ptosis,” that is, an isolated paralysis of one levator palpebre superioris, the cause of which may be found at the autopsy to be a lesion in the anterior portion of the cortex of the opposite side. (2) As far as concerns the nature of the disease we may distin- guish :— (a) Independent affections in the course of the nerve, as neuritis, 438 DISTURBANCES IN THE MOVEMENTS OF THE EYES. perineuritis, inflammation of the nuclei (polioencephalitis, inflam- mation of the gray matter in the ganglia on the floor of the fourth ventricle and aqueduct of Silvius), with destruction of the ganglion cells, scleroses, and degeneration of individual groups of ganglion cells. (4) Diseases of neighboring tissues which involve the nerves or their roots, as inflammations, new growths, softening, and degen- eration foci. (c) Diseases of remote tissues which, in a mechanical way, inter- rupt or hinder conduction along the nerves, as new growths and hemorrhages. Which of these causes is at work can be found out only by study- ing the history and the general condition of each case. Often enough this does not suffice. Not infrequently paralysis of a lid or eye muscle may be the first and but fleeting sign of a grave brain or spinal cord lesion, such as tabes dorsalis, multiple sclerosis, or progressive paralysis. Tubercular meningitis and tumors of all kinds may produce an eye-muscle paralysis. (3) As essential causes of the brain lesions here enumerated, various infections must bear the blame. Syphilis especially must be charged with causing ten to 20 per cent., or according to v. Graefe 50 per cent. of all cases. Equally as common are the paralyses from tuberculosis of the meninges, other forms of meningitis being less disastrous. Another group of paralyses, those caused by the poison of diphtheria, is of great interest to the ophthalmologist. Usually the muscle of accommodation, less so an external eye muscle, is affected. Finally, Grippe, rheumatism, typhoid and other poisons like nicotin, alcohol, lead, ptomains, carbonic oxide gas, have all been causes. Occasionally an eye-muscle paralysis has been traced to a cerebral hemorrhage due to arterial sclerosis, diabetes, or fractures at the base of the brain. 3. PROGNOSIS. This is favorable in paralyses that result as a sequel to diph- theria or from some mild injury or transient intoxication. It is doubtful in paralyses from some unknown cause, or from what for tradition’s sake we love to call “catching cold.” Such “colds” may return after a time, bringing associated paralyses of other nerves with them, and then the true nature of the disease may be made out. The prognosis is bad in paralyses which are recognized TREATMENT, 439 with the presence of other pathological signs as but a part of some grave spinal cord-or brain lesion, 4. TREATMENT. This should begin by covering the unsound eye to prevent the double vision and the accompanying vertigo, after which the cause of the trouble must be attacked, supposing that it can be discov- ered, If there is syphilis, mercury, diaphoresis by medicine or bath, and large doses of iodid of potassium are to be used. Dia- betes demands the proper diet and hygiene. Injuries must be treated by rest. Diphtheritic paralysis usually heals by proper bodily nutrition, as do also cases due to mild intoxication ; a deep- seated lead palsy, on the contrary, heals neither of itself nor by treatment. In all cases due to some obscure cause, a specific treat- ment is impossible, but we need not, therefore, condemn the numer- ous remedies so warmly recommended for “ paralysis.” Bleeding, cathartics, diaphoresis, large doses of iodid of potassium, exercise to the (half) paralyzed muscle, and electricity—either the galvanic or faradic current—are at our disposal. A trial of iodid of potassium is always to be recommended, even if the patient confesses no syph- ilitic infection and if no signs of it are present. If the paralysis continues in spite of these methods and there is no likelihood of cure, there remains the task of relieving the patient from the severest and most distressing disturbance, the double vision. In some cases this is not present, for, besides the eye muscles themselves, the levator may be paralyzed and the droop- ing lid will, therefore, exclude the unsound eye from its part in vision; or tabes may have progressed so far that the diplopia is no longer perceived because the optic nerve is attacked and visual acuity thus reduced in addition to the oculomotor paralysis. If double images are present to the patient’s discomfort an attempt can be made to fuse them by means of prisms. In spite of the theoretical objection that a special prism is needed for each visual direction or none at all needed when the eye looks toward the healthy side, prisms have shown themselves serviceable in many cases. Such cases have a decided range of fusion. Suppose the left external rectus to be paralyzed and an extensive range of fusion present, a prism of 4°, 6°, or 8°, base outward, may produce single vision for a part of the visual field lying to the left, while in looking straight ahead or toward the right fusion may be main- 440 DISTURBANCES IN THE MOVEMENTS OF THE EYES. tained by contraction of the two interni, that is, by intentional con- vergence, In other but less common cases the harmony of eye movements may be restored by weakening (tenotomy) the power of an associa- ted muscle of the sound eye; much more importance is, however, attached to the use of the eyes than to their excursion. Supposea left superior oblique to be half paralyzed; ought an oblique muscle or the inferior rectus of the right eye to be tenotomized? Obvi- ously the latter, for since both oblique muscles have an abducting factor, it would only increase the tendency to convergence and homonymous double images if a remaining, unaffected oblique muscle were weakened; while to weaken the right inferior rectus, which is an adductor, would decrease the moderate tendency to convergence and still more decrease the difference in elevation of the double images, than would a tenotomy of a right oblique mus- cle—an operation, it may be remarked, very difficult to perform. In studying this rotatory factor we learn that the superior oblique of one eye is associated in movement with the inferior rectus of the other. In the majority of cases of lasting eye-muscle paralysis nothing can be done beyond excluding the paralyzed eye from vision by a bandage or an opaque glass in the spectacle frame. If secondary contracture develops during the disease the treatment is to be that of concomitant squint given on #. 445, but an attempt should be made to oppose the development of this contracture by Michel’s method, which consists in stretching the antagonist of the paralyzed muscle. This is done by seizing a fold of the conjunctiva in fixation forceps and then repeatedly rotating the eye toward the side of the paralyzed muscle. II. STRABISMUS CONCOMITANS, Concomitant SouinT, WITH PaRTICULAR REFERENCE TO CONVERGENT SQUINT. 1. VISION IN STRABISMUS. Convergent squint develops nearly always in early childhood. In the beginning it shows itself only at intervals as strabismus periodi- cus, and, as attentive mothers may observe, usually when the child is looking at a near object. The squinting position becomes more frequent until it has finally, even if after years, become constant. VISION IN STRABISMUS. 441 In case the same eye always deviates, the condition is called sérad- smius untlateralis ; if both eyes are alternately used for fixation, first one and then the other deviating, the condition is called strabismus alternans. The demonstration and the measurement of the eye’s deviation has already been given on g. 89. With reference to the diagnosis only the differences between paralytic squint and concomi- tant squint need be here emphasized. In paralytic squint there is :— In concomitant squint there is :— (1) Contraction of the Field of Vis- (1) Displacement of the Field of Vis- ion; ion, but no contraction ; (2) Secondary deviation greater than (2) Secondary deviation equal to the : the primary ; primary ; (3) Disturbance with double images. (3) No disturbance with double images. The first point needs nothing more than what is said on p. 8&9. The second needs a short, but the third an elaborate explanation. (2) In concomitant squint the position of the eyes in relation to each other is faulty, but the movements of the eyes are quite nor- mal. For example, suppose there is convergent squint with the left eye squinting. If the right (the fixing) eye is turned to the right, an equally strong impulse, according to the rule of association between eye muscles, is sent to the internal rectus of the left eye, and the result is that both eyes are turned toward the right with unchanged degree of convergence. If the right eye is now cov- ered and the left induced to fix, the latter must pass out of its position of squint by an impulse sent to its external rectus. This is not possible without sending an equally strong impulse to the internal rectus of the right eye, in consequence of which the right eye also turns to the left an equal amount, that is,an amount equal to the angle of squint. This“ secondary deviation” of the right eye - is, therefore, just as great as the “ primary deviation ” of the left eye. (3) Having confirmed what has been said (. 70) about projec- tion of retinal images and (/. 428) the conditions in muscle paraly- sis, we might suppose that in concomitant squint there would also be double images—homonymous in convergent, heteronymous in divergent squint. Experience shows that this is not so, but that the patient does not see at all with the squinting eye the object fixed by the normal eye, or, in other words, that the retinal image of the squinting eye remains unperceived. This does not mean that the squinting eye is entirely excluded from participation in the 442 DISTURBANCES IN THE MOVEMENTS OF THE EYES. visual act. It can be easily demonstrated that objects within the visual field of the squinting eye are partly seen, partly not seen,— that there is a “regional exclusion.” At all events, the squinting eye perceives everything lying within that part of the total visual field belonging to the squinting eye alone. Since in divergent squint the individual fields coincide in a smaller area than normal, the total visual field must, therefore, be greater; in convergent squint, for a corresponding reason, it must be smaller than normal. Objects lying within that part of the visual field common to both eyes are not all necessarily excluded from the squinting eye, but only those that would disturb the vision of the healthy eye. For example, many squinting patients say that when reading they see double at the beginning or end of a line, that is, that the image in the squinting eye is not suppressed if it appears on the background of white paper, but that it is suppressed when it appears at a spot where letters are seen by the healthy eye. Reading would, of course, be quite impossible if each eye projected different letters to the same spot in space; diplopia for objects seen at one side causes, however, little disturbance, a condition explainable by what has been said about the presence of physiological double images (~. 75). It is easy to understand, too, that the fixing eye will conquer when there is a struggle between images of different objects for the same spot in space. The normal eye, on the one hand, has a better visual acuity (~. 444), and, on the other hand, it uses in the struggle its most sensitive retinal area, while the squint- ing eye must be content with eceentric vision from a more peri- pheral and less sensitive retinal area. This suppression of retinal images on certain areas is the means adopted by the eye for freeing itself from the disturbance of diplopia. The process is a psychical, although an unconscious one, accomplished by association of action in the two eyes. ‘This, and other conditions also, may be established from the fact that the double images unnoticed by the patient are, in most cases, made perceptible by simple means. Many who squint see double as soon as their attention is called to it. Others may be made to see double by placing a dark-colored glass in front of the eye with the better vision. If this does not suffice, a prism, with base down or up, should be placed in front of the deviating eye, while the dark-colored glass remains in front of the fixing eye. In the deviating eye there will then be formed an image of the object fixed by the healthy eye, this image fall- ing upon a retinal area where retinal images have not as yet been suppressed because they arose from objects seen peripherally by the healthy eye also. We have now a con- dition which the squinting eye has not learned to treat to its best advantage. In some cases double images cannot be produced by any artifice whatever. The preceding statement in no way contradicts the laws of projection already given CAUSES. 443 (/. 70), but only shows that nature can evade such laws in the interest of single vision. There are, however, some squinting persons in whom retinal images are really projected otherwise than ought to be expected from the law of projection. Many such patients, after double vision has been produced by the use of a co ored glass, assert that there is such a distance between the two images as would show a direct contradiction to the actual position of squint, since this distance must be too small for the demonstrable angle of squint. There are even cases with binocular fusion in spite of a squint, that is, cases in which the retinal image on the fovea centralis of the fixing eye is fused with the image formed on a peripheral (unequal and weaker) retinal area of the other eye. It is seen, therefore, that the law of ‘‘ identical retinal areas’’ is anatomically favored by equal visual acuity of identical areas and is perpetuated by use of such eyes, but that this law can be violated by a continued position of squint. Such violation is unnatural. This may be seen in the results of overcoming convergence by an operation; at first crossed double images appear, as if divergence were present instead of the normal position, but this condition does not last long; after a few days the natural association of retinal images masters the acquired association and the double images disappear. 2, CAUSES. The eyes when closed are in a position of equilibrium. The form and direction of the orbits, the length, thickness, and attach- ment of the eye muscles, the shape of the eyeball, in short, the anatomical relations of the eye, its soft and its bony surroundings, all have their influence on this position of equilibrium. As a rule, though not always, these anatomical relations are the same for both eyes. On account of the distinctly appreciable divergence of the orbits this position of equilibrium might also be divergent, but as divergence of the visual axes is not used in vision, the position is rather that of parallelism, or even of convergence for near work. Since the use to which an organ is put has a decided influence on its anatomical structure, it is probable that the eye muscles develop during early childhood so as to make parallelism of the visual axes the position of equilibrium. Parallelism of that exactness requisite for distant vision is, however, confirmed by anatomical relations only in the rarest cases. : From the above it may be deduced that sguint depends upon a deviation of one or both eyes from the normal position of equilibrium. We must, then, find out whether the disturbance of equilibrium is produced by anatomical conditions alone, or by physiological conditions as well, perhaps by an habitually over-strong nervous impulse to the internal muscles. It must be remembered that the need of proper adjustment of the eyes exists only for the sake of binocular single vision. If this need is lacking, or if the eye is influenced by unequal visual 444 DISTURBANCES IN THE MOVEMENTS OF THE EYES. acuity* or unequal refractive condition, it is evident that the least disturbance of muscular equilibrium must lead to squint. Con- versely, if visual acuity and refractive conditions are equal, and if the will power is strong enough, a considerable disturbance of muscular equilibrium may be present without causing squint, because the impulse or, in certain cases, the desire for binocular simple vision can, in a physiological manner, take the place of a muscular equilibrium not supplied anatomically. In this sense we may speak of inequality in visual acuity as direct cause of squint. It must be further remembered that a second influencing factor lies in the association of convergence and accommodation ( p. 79). The proper position of the eyes can be thereby induced, even if, on account of weaksightedness, there is no need for it. But this very factor becomes a cause of squint if refractive error is present. Hyperopia calls out an abnormally strong accommodation with its consequent canvergence, which is greater than is necessary for the distance of the object fixed. Conversely, in myopia the accommo- dation is not so great as normal and the convergence is insuffi- cient, so that a divergent position is assumed in fixing a near objeet. Although convergent squint in hyperopia, or divergent squint in myopia, is often enough prevented by the impulse for binocular fusion (or by the favorable anatomical conditions in the first case), there are, nevertheless, numerous examples of squint caused by refractive errors, the more naturally, of course, the less interest there is for binocular fusion. The question as to the cause of the squint is, therefore, in such cases—and they are the majority— completely answered. There yet remains a minority of cases where refractive errors are not present, or where the form of squint does not correspond to them,—cases, for example, where hyperopia is associated with di- vergent, myopia with convergent squint. Rare cases of upward or downward squint are not of themselves necessarily due to refrac- tive errors. For all such cases we assume that they depend either * Reduced visual acuity in the squinting eye is so common as to be the rule. It de- pends either upon corneal opacities, lens opacities, astigmatism, or—in most cases—has no discoverable cause. Such an amblyopia is either the cause or the effect of the squint, or it may be both. Congenital amblyopia of one eye may as naturally induce squint as acquired amblyopia. Cases have been reported in which the deviating eye was at first normal, but became weak after some years. This is, of course, amblyopia ex anopsia (2. 383). TREATMENT, 445 upon improper innervation, as convergent squint due to an habitu- ally stronger innervation of one or both interni; or upon anatomical conditions, as a greater diameter of the internal or external rectus, and, perhaps, an insertion of the muscle closer to the cornea; or, finally, upon a restoration of normal physiological or anatomical relations, The circumstance that many a squint disappears in sleep, during narcosis, or after death gives support to the assumption that concomitant squint may be caused by improper inner- vation of one or both interni. And since cases have been reported where the squint continued partially or entirely after death, we may likewise derive support for the assump- tion that such cases were due to anatomical causes. Further examples of squint through nervous influences are found in those cases that begin reflexly as the result of conjunctival or corneal irritation. Moreover, cases of concomitant squint developing from paralytic squint (g. 477) are to be indirectly at- tributed to a nervous influence, since a muscle released from the counterbalance of its (paralyzed) antagonist takes a condition of indirect contraction. 3. TREATMENT. Treatment must always, if possible, attack the cause. If the visual acuity of the deviating eye is weak, an attempt must be made to improve it. At times this can be done by neutralizing an astig- matism or by an iridectomy, or in amblyopia without cause by exercising that eye. Exercise of a weak eye is most easily accom- plished by occasionally bandaging the other, but success may be expected only when this exercise is begun in early childhood. In case a refractive error is the cause of squint, we have a remedy for it in neutralizing glasses, and we actually see many a manifest, convergent squint disappear after a few months’ use of neutralizing lenses. If this result is not attained the treatment must be opera- tive. Nevertheless, it must always be remembered that the con- vergent squint of children quite often heals of itself, either because the hyperopia becomes emmetropia or irrespective of it. The operation should, therefore, not be done before the seventh year, and only then if squint has existed some years and has defied treat- ment with glasses. In divergent squint a spontaneous cure does not take place. The operations are :— (1) Tenotomy of the muscle acting too powerfully ; (2) Advancement of the muscle acting too weakly ; (3) A combination of the two. In convergent strabismus of slight to moderate degree—}3 to 7 446 DISTURBANCES IN THE MOVEMENTS OF THE EYES. mm.—tenotomy of one or both interni may not only restore the correct position, but effect the normal mobility of the eyes. If the tendon of a rectus muscle is cut close to its insertion in the sclera it retracts only 3.5 to 5 mm. and heals there; farther retraction is prevented by its peripheral attachments, that is, by the connective- tissue fibers that pass from the side of the muscle or tendon sheath to the eyeball and establish a loose connection with it. Obviously the adduction of the eye decreases by about the amount to which the tendon is set back. This does not signify the actual loss, since the adductive power was above normal, and the loss of adduction will, to a great extent, appear again in the gain of abduction. If the retraction of one internal rectus does not suffice, of course we may resoft to the same operation on the healthy eye, for the association of the two muscles in the horizontal meridian has the effect of giving to the operation on the healthy eye the same result in the mutual position of the two as the same operation has on the deviating eye. In very pronounced squint even a double tenot- omy will not suffice to reproduce the normal position. Under such circumstances the rectus internus must be severed and allowed to retract, and the rectus externus must be advanced, that is, sutured by its tendon closer to the cornea (a) Larse, than the original insertion. It is advisable to nage mall strabismus Herform the advancement of the externus about a week after the tenotomy of the internus, so that the latter will then have firmly healed; the simultaneous perform- ance of both operations allows too much retraction of the tendon of the internus, and the loss of adduction is too great. guswanay | Ss & +) SNOSRZLNAD : = aa SY a Fic. 155. Tenotomy of Rectus Internus.—Instruments (g. 347): lid speculum, fixation for- ceps, dissection forceps without lock, blunt scissors cutved on the flat, the so-called Louis’ scissors, a large (a) and a small (4, Fg. 155) strabismus hook, needles and thread, cocain. Disinfection of physician, assistants, all instruments, and the field of operation. The patient looks straight ahead, and an assistant, with the fixation forceps, seizes a fold of conjunctiva near the external corneal margin and rolls the eye gently outward. The surgeon, with the other forceps, seizes a parallel fold of conjunctiva in front on the insertion of the tendon + of the internus and cuts perpendicularly upon it. Then with 1 The line of insertion of the internus is 70.3 mm. long and 5.5 mm. from the cor- neal margin; of the externus it is 9.2 mm. long and 6.9 mm. from the corneal margin (fig. 151). ADVANCEMENT, 447 short strokes of the scissors beneath the conjunctiva he undermines i it in the direction of the nose. He thus uncovers the anterior end of the internus tendon. Next he passes the larger strabismus hook, held flat against the eye, beneath the tendon, draws it up slightly, and with the scissors severs it from the sclera. He now takes the small strabismus hook and carries it close behind the insertion of the tendon into the upper and lower corner of the wound, in order to find any remaining fibers that ought to be severed. After the operation is finished the result is tested by comparing the loss of adduction (f. 90) with the predominance of adduction that was present before. If the loss of adduction is greater than was intended, the result may be reduced by taking a broad hori- zontal conjunctival suture. Since tendon and muscle are still con- nected with the conjunctiva farther back, such a conjunctival suture will draw forward the muscle which is too much retracted. If the result is insufficient, a second operation may be performed six weeks later. A conjunctival suture may be needed if the sclera has been de- nuded. In case the suture is taken for such a purpose, the result of the operation will not be affected if the edges of the wound are seized very gently or if the suture is carried perpendicularly. Advancement.—A severed tendon may be advanced by a broad and tightly drawn suture through the conjunctiva, and the new in- sertion of the tendon will lie nearer the corneal margin than the original insertion. Tenotomy can, therefore, be changed to an ad- vancement by a proper conjunctival suture. As a rule, however, such a suture is not relied upon, but the tendon itself is sutured, close to the corneal margin, either to the conjunctiva remaining or to the sclera, through the upper layers of which the threads pass. Recently many surgeons have preferred to advance ‘‘ Tenon’s capsule ”’ instead of the muscle itself. This name is used to describe a connective-tissue sheath, in which the eye rests like the end of a bone in its capsule at a joint. This sheath is connected with the eyeball by loose and elastic connective-tissue strands; but near the cornea on the one hand, and near the entrance of the ciliary arteries and nerves at the posterior pole on the other hand, this connection becomes more intimate. The external surface of Tenon’s capsule, that is, the surface from the eyeball, is continued into the connective-tissue envelope of the orbital fat. The eye muscles, therefore, are outside of the capsule, and their tendons must pierce it in order to reach the eyeball. They do not, however, pass through a smooth aperture, but are embraced posteriorly by a fold of this capsule, hence the ex- pression, ‘‘ peripheral attachments’’ (/. 4¢6). To advance Tenon’s capsule, Wecker excises a semilunar flap from the conjunctiva, in front of the insertion of the too weak muscle, 5 7. broad and zo mm.high. Then he cuts into Tenon’s capsule, releases the muscle from its surrounding attachments without separating tendon from sclera, and advances Tenon’s capsule to the corneal margin by means of two sutures that close the conjunctival wound at the same time. 448 DISTURBANCES IN THE MOVEMENTS OF THE EYES. 4. AFTER-TREATMENT AND RESULTS. The operation for squint endeavors to reaccomplish normal, binocular single vision, that is, the fusion into one visual percep- tion of the two retinal images formed of one external object. It can be tested by the stereoscope whether this fusion takes place, by showing parts of a figure to the right eye alone and other parts of the same figure to the left eye alone; for example, a horizontal line to the right eye and a perpendicular line to the left eye; if binocular fusion is accomplished the figure will appear as a cross. This result is, however, not always obtained. The position of the two eyes can, in the best cases, be made about right by one or more operations, but complete restoration of function depends upon the energy of the two eyes to respond to the impulse for binocular fusion. Ifthe visual acuity of the eyes is unequal—as it is in most cases of squint—the prompting to such an effort is lacking and the result of the operation must be restricted to its cosmetic effect, beautifying the patient. That is usually about all she asks for. For complete assurance of the success of the operation we must use methods by which a desire for binocular fusion may be aroused or encouraged. The best visual acuity possible must be obtained by spherical or cylindrical lenses, and exercise in fusion of retinal images must be supplied by astereoscope. Supplementary aid may be given by favoring convergence if the position of the eyes is slightly divergent, or by favoring divergence if the eyes are slightly convergent. Convergence is encouraged by looking at near objects, by stimulating the accommodation with concave lenses, and by lowering the visual plane. Divergence is encouraged by resting the eyes, by relaxing accommodation with convex lenses, and by elevating the visual plane. Lasting success for an operation, no matter how successful it seemed at first, can be expected only when binocular fusion is completely reproduced. If binocular fusion is faulty it often happens that the squint returns after a year or more —the danger being that divergent squint will relapse into its orig- inal condition and that a convergent squint will relapse into the opposite condition and become divergent. It is best, therefore, in operating for convergent squint to do too little rather than too much, especially since a trifling convergence, say of z mz, is not displeasing, or certainly less displeasing than an equal amount of divergence. To complete and to retain the result of an operation, if binocular vision has always been lacking, one must often be LATENT STRABISMUS. 449 content to encourage or to overcome convergence by any of the methods mentioned above. Il]. LATENT STRABISMUS, with ParricutaR REFERENCE To DiverGentr Sournt. By latent strabismus is understood a disturbance of the muscular equilibrium, which is suppressed for the sake of binocular single vision. There may be either convergent, divergent, upward, or downward squint. Latent divergent squint is by far the common- est. Occasionally divergence and convergence may be associated, convergence for distance and divergence for near. Three points must be satisfied to make the squint latent :— (1) Both eyes must be placed correctly when they are used for looking at an object ; (2) One eye must deviate when it is excluded from vision by cov- ering it; (3) There must be no restriction of the muscular excursion. Latent, and especially divergent squint, causes at first no symp- toms, but as the deviation increases the symptoms of “ muscular asthenopia” (. 368) appear ; they finally disappear in turn as latent squint becomes manifest. Causes.—In some cases latent squint depends upon refractive errors (~. 443). Divergence is quite frequently the result of myopia. But latent divergent squint is no rarity in emmetropia or even in hyperopia. The reason for it may be found in a weakness of the recti interni, and many authors designate latent divergent squint as ensupficiency of the interni. That weakness is actually present is seen by the increase of the latent squint when there are such con- ditions as physical exhaustion, lack of sleep, indulgence in alcohol, or illness of any kind, which reduce the tone and energy of the whole body. Whether this weakness is of the muscles, or of the nervous impulse to them, is a disputed point. That it is rather a nervous trouble is suggested by the fact that the internal recti still perform their function to the full extent of peripheral excursions. Treatment.—Every latent squint does not cause symptoms. Very high degrees are occasionally found, which dwindle to very slight degrees when the fixation object is approached to the eye. In such cases treatment is unnecessary. But if latent squint and 29 450 DISTURBANCES IN THE MOVEMENTS OF THE EYES. symptoms of asthenopia (/. 368) exist side by side, it is unwise to conclude at once that there is any causal relationship between the two, but rather that asthenopic symptoms more commonly depend upon refractive errors than upon latent squint. If refractive errors, conjunctival (~. 783) and retinal asthenopia (~. 307) can be ex- cluded, or if the connection between symptoms and squint are made undoubted by the nature of the patient’s complaint (occa- sional diplopia, disappearance of distress when one eye is closed), then treatment should be tried by the prescription of suitable glasses. In the divergent squint of myopia the neutralizing con- cave lenses often suffice, since they demand accommodative effort and thereby increase the instinct to convergence, while they also admit of work at a greater distance, which implies a less claim on convergence. If this remedy is not sufficient, or if, on account of emmetropia or hyperopia, is not suitable, we must abandon the attempt to produce normal convergence, and resort to the use of prismatic lenses (fig. 33, #. gz) in order to bring about binocular fusion with a relatively divergent position. For example, suppose an emmetrope has a latent divergent squint at the usual reading distance of 30 cm., and that this squint can be neutralized by a prism of &° base inward; then with glasses having a prism of 4° on each side the patient will be enabled to read continuously, with- out effort at fusion, at 30 cwz. distance. If the patient wears glasses on account of myopia or hyperopia, a prismatic effect may be added to the lenses by giving them a greater or smaller distance apart than the pupillary interval calls for. Suppose a patient to have myopia of 4.0 J, the neutralizing lenses of g.0 D will diminish the latent divergent squint, but will not altogether overcome it; but if the lenses are placed so far apart that the patient must look through the inner half of them, the effect becomes that of prisms in the position of abduction, the effect being greater the nearer he looks through the edge of the glass. It must be kept in mind, however, that the dispersing power of the edge ofa lens is greater than that of the center. By testing with A. Graefe’s equilibrium test (2. 92), the suitable distance for the glasses may be decided on. It is hardly advisable to prescribe prismatic lenses stronger than 4°, since the glasses are then too heavy and the chromatic aberra- tion too strong. Ifthe squint becomes more pronounced than cor- responds to a prism of 8°, an operation must be performed to allow the externus to retract by section of its tendon. If the muscle TREATMENT. 451 retracts it obviously grows weaker and the question comes up whether the improved convergence for near objects may not have been obtained at the cost of diplopia when looking at distant objects on the side of the retracted muscle. The question may be answered as follows: In looking at distant objects, parallelism, but never divergence, of the visual axes is necessary ; the capability for real divergence—facultative divergence—may, therefore, be sacrificed by retraction of one or both externi without causing any disadvan- tage to the patient. The capability for real divergence is measured by the strongest prism in the position of abduction (base toward the nose) with which binocular fusion can be maintained continu- ously and without effort. The approximate equality between facul- tative divergence for distant objects and insufficiency when looking at near objects (both being measured by prisms) gives a clue for the successful resort to tenotomy. For example, suppose that diver- gence equal to a prism of z6° is possible for distant objects, and at reading distance an equilibrium with prism of 20° in the position of abduction is established; we may, without further investigation, perform a tenotomy on one externus, since experience teaches that the final result of the operation is about equal to the action of a prism of 76°. Parallelism of visual axes will then be possible for distant objects, while for near objects there will be a latent diverg- ence of g°, which may be tolerated without any trouble, or can be corrected by prismatic glasses of 2° on each eye. If the conditions are less favorable, that is, if the facultative diverg- ence is small, or at least smaller than the insufficiency for near objects, it is better to advance an internus without performing tenotomy of the externus at the same time. There is thus no loss but rather a gain in the range of movement. The operation itself is very simple, but success may be difficult to achieve because the difference between the immediate and final results of the operation varies greatly in individuals. The most important data for judging of the condition immediately after the operation are :— (1) The amount of restriction of movement, and (2) Equilibrium in the “ position of election.” This term was used by v. Graefe to describe the direction of vision z5° toward the side of the eye not tenotomized, and 75° below the horizon. At this position, and with the fixation point at least 3 1. distant, equilibrium will be maintained immediately after 452 DISTURBANCES IN THE MOVEMENTS OF THE EYES. the operation, that is, there will be neither convergent nor divergent squint. The restriction of movement in the tenotomized eye should amount to 3 or at most 6.5 77., according to the amount of facul- tative divergence; a greater restriction would require a conjunctival suture to overcome the result proportionately. The final outcome of the operation for latent squint is better than it is in that for concomitant squint, because the desire for binocular single vision is present in latent squint and acts as an important factor in reéstablishing the normal muscular relations. [ Heterophoria.—By reading the two preceding sections and the paragraphs on the methods of examination (J. 92), it will be seen that the condition of squint is closely allied to heterophoria, and that the latter may pass, by nearly imperceptible gradations, into. the former. There is, however, one distinction that must be care- fully made: Squint may always be detected objectively by the ob- server, and it sometimes annoys the patient by the production of diplopia, although in concomitant squint he easily neglects the im- age in one eye; but heterophoria can never be detected objectively, the patient is never aware of diplopia, and there is no suppres- sion of the image in either eye. Squint is, therefore, a condition often detected by the patient, heterophoria a condition diagnosticated only by the ophthalmologist. The causes of heterophoria are the same as those given for latent squint (f. 449), although the tendency’ of the visual lines may be either outward (exophoria), or inward (esophoria), or upward and downward (hyperphoria). Some confusion may arise by finding heterophoria of one kind for near work, and of another kind for far work; but it is best to treat only that kind causing the greater trouble. In exophoria headache and eye-strain are most intense after near work, but the power of ac- commodation may be increased. The ability to overcome adduct- ing prisms varies, but is usually quite pronounced. In esophoria, headache and eye-strain are most apt to appear after excessive use of the eyes in distant work, such as visits to the theater or picture gallery, and after long rides in the cars; the power of accommoda- tion may be lessened, while the ability to overcome abducting prisms is usually pronounced. In Ayperphoria, all sorts of condi- tions may be present, and the statements of the patient may be unsatisfactory and confusing. There is here more amblyopia, however, and more muscular or nervous irritation manifested by HETEROPHORIA. 453 spasm of lids, twitching of facial muscles, neuralgia, and lacrima- tion ; while the ability to overcome a prism (base either up or down) is sure to be increased. Treatment naturally divides itself into— (1) General, (2) Optical, and (3) Operative. (z) Every element which may impair visual acuity or keep the patient’s health below par must be persistently combated. Rest to the eyes, atropin, electricity locally applied, change of occupa- tion and surroundings,—all have their place. (2) Optical treatment implies more than the correction of refrac- tive errors, which must, of course, be the initial therapeutic meas- ure, although it not infrequently happens that the symptoms of heterophoria disappear after the eyes have been relieved of the strain from ametropia. Should these symptoms continue, the use of prisms should be immediately tried; prisms may be prescribed either to be worn constantly, or to be used as a means of exercise. In the former case, the desired result may be obtained either by adding the prismatic effect to correcting lenses by decentering, or by adding an actual prismatic form to the lenses prescribed. In the latter case, the patient is treated by graduated prismatic exer- cise at the physician’s office, or he is given prisms of increasing power which he can use at home to develop the weak muscle by strengthening the impulse to overcome them. “There can be no doubt that ample experience has shown the helpfulness of weak (z’ to 5°) prisms continuously worn for moderate degrees of mus- cular error, and this method should precede the use of gymnastic prisms or of the various other palliative measures. In giving prisms, the rule may be formulated that the base should be placed toward the image whose position is to be corrected; this corre- sponds to the weak muscle, provided the physiological or func- tional activity of the muscle is regarded. The apex of the prism like a knife edge indicates the muscle which should be weakened, and the base denotes the muscle to be strengthened” (Noyes). But in no individual case can an inflexible rule be applied. For a weakness of adduction (exophoria) prisms (base in) would seem @ priori to be indicated, but the expected result is not always obtained, while in rare cases the very opposite prismatic effect (base out) has given relief. The same may be said of weakness of 454 DISTURBANCES IN THE MOVEMENTS OF THE EYES. abduction (esophorja); prisms (base out) are indicated, but do not always relieve, while the opposite prismatic effect (base in) amelio- rates the distress. It is probable that when such contradictory results are obtained there will be found exophoria for distant, and esophoria for near work, and that the relief is experienced because the patient really uses his eyes most in the position for which the prisms meet the indication according to the rule. Every case, therefore, must be treated on its merits, and neither examination nor treatment can be said to be complete until every possible varia- tion in the working power of the muscles has been thoroughly tested. (3) Operative treatment consists of the mechanical (surgical) weakening of the over-strong muscle by a tenotomy. Such an operation may be total, the same as is performed for strabismus (p. 446), or a graduated tenotomy, in which the effort is made to restore equilibrium by section of a few fibers at the insertion of the tendon. A tenotomy for heterophoria does give, in selected cases, the most brilliant results, but the surgeon should always remember that operative interference is the treatment of last resort, not to be undertaken till all other means have failed; that however favorable the momentary results may be, there is apt to follow them a distress- ing diplopia due to weakness of the muscle which was originally too strong ; and that he must be ready, at the time of operating, to control his tenotomy, either by a conjunctival suture (f. 447), or by a supplementary tenotomy of the muscle which becomes over-active after the primary tenotomy. For these reasons it is wise for him to adhere to the following rules: always operate with a local anesthetic only (cocain); sever the tendon at its scleral attachment, rather than the muscular fibers ; divide the total result wished for between the two eyes, so that a muscle of each eye bears only half the correction ; make repeated examinations during the operation to see when the heterophoria has disappeared; and be ready to correct an exag- gerated result at once, by a conjunctival suture, remembering that too radical an operation may have the opposite effect to that which he seeks to correct, while it is always easier to repeat the first operation on the same muscle than to perform a second operation on its antagonist.—H. ] NYSTAGMUS. 455 IV. NYSTAGMUS. Spasmodic, involuntary, jerking movements of the eyes, which do not interfere with, but accompany, the normal, voluntary move- ments of the eyes, are termed nystagmus. Three forms are distin- guished according to the direction of this twitching :— (a) Nystagmus oscillatorius, twitching to the right and left, hori- zontally, or upward and downward, perpendicularly ; (6) Nystagmus mixtus, oblique twitching ; (c) Mystagmus rotatorius, rotations about the visual axis. These may be quite distinct, or in combination with horizontal, perpen- dicular, or oblique twitchings, so as to produce directions of move- ment which, in contradistinction to (a) and (4) are in no sense phy- siological. There is often squint along with nystagmus. Often, too, there is noticeable a moderate shaking of the head in the same direction and with uniform speed with the nystagmus. This shaking of the head has been held to be a compensatory movement for the nys- tagmus, although a compensation for an eye movement to the right by an equally strong head movement to the left cannot be demon- strated in individual cases, on account of the rapidity with which they are made. In certain diseases nystagmus changes remarkably both in rapid- ity and character of the movements; if the patient knows he is closely watched, or if he labors under any excitement, the phenom- ena are increased, while during sleep or narcosis they are lessened or altogether stopped. Many patients can themselves inhibit the movements by taking some definite position for their eyes, say a pro- nounced convergence. Many healthy patients can voluntarily pro- duce a nystagmus. This disorder may be divided into three classes according to the causes :— (2) Nystagmus from Weak Sight in Both Eyes.—This is the commonest form. It begins in early childhood as the result of cor- neal or lens opacities, or of astigmatism, of microphthalmos, of amblyopia without cause. Such pathological conditions cannot be a matter of indifference for position and movement of the eyes in early childhood, since an exact binocular fusion must be of decided significance in the development of normal eye movements. This amblyopia does not, however, explain the nystagmus completely, since there are cases of nystagmus without amblyopia, and cases of 456 DISTURBANCES IN THE MOVEMENTS OF THE EYES. bilateral amblyopia without nystagmus. There must be some fac- tor which influences the eye muscles themselves; an indication for this is found in the fact that at one time the external and internal recti muscles, and at another time the elevator and depressor mus- cles, are to be blamed for the nystagmus; while another fact must be noticed, namely, that certain visual directions are, by means of corresponding movements of the head, preferably used by the patient, because all other directions are more difficult for him. This first form of nystagmus causes no trouble, and especially no apparent movement of the object looked at; therefore no treatment is needed unless it be to improve the visual acuity. (6) Nystagmus of miners comes in paroxysms, and is accom- panied by apparent movement of the object looked at, and by ver- tigo. These paroxysms are caused by exhaustion from trying to see in an insufficiently lighted space (coal shaft), and from uncom- fortable positions of the eyes like exaggerated elevation, less often exaggerated depression of the visual plane. The disease is to be considered asa paresis of the levator muscles due to overstimulation, so that they contract only spasmodically. This paresis is favored by everything that tends to make work for the eyes under such circumstances difficult, such as poor vision, insufficiency of the interni, or physical prostration. The character of eye movement in miners’ nystagmus is usually a circular or elliptical rotation. This may be demonstrated by means of a “reflection test:”’ a luminous point in a dark room will appear to the patient during an attack as a circle or an ellipse, for the same reason that a luminous point rapidly revolved appears as a circle to the healthy person. The distress is often so great that the patient must abandon his vocation. A successful treatment, apart from simple rest, has not yet been devised. (c) Nystagmus from brain disease has only symptomatic sig- nificance. It is of especial importance in the diagnosis of multiple sclerosis, that cerebro-spinal disease characterized by the appearance of numerous gray, fibrillary connective-tissue foci in brain and cord. The three important signs of this disease are :— (1) “Intention trembling ’’—appearing during voluntary, inten- tional movements ; (2) ‘Scanning speech ;” (3) Nystagmus, which may be analogous to intention trembling, since it sets in during fixation and during intentional eye movements. DISEASES OF THE ORBIT, 457 DISEASES OF THE ORBIT. INTRODUCTION. In most cases of diseases of the orbit there is exophthalmos. This term implies a protrusion of the eyeball outside its natural position in the orbit. This depends upon a restriction in the space within, either because the eye is too large for the orbit, as the “ pop-eye” of myopia (f. 369), or because the otherwise normal contents of the orbit has increased, such as the fat tissue in general adiposity, and the quantity of blood if the vessels are dilated, or because bloody, serous or purulent exudations crowd the eyeball forward. The opposite of exophthalmos, retraction of the eye within the orbit, exophthalmos, is at times observed. It depends upon absorp- tion of the orbital fat or upon decrease in blood contents of the orbital vessels, or upon great loss of fluid from the body resulting from intense purging, as in cholera. It is not quite clear to me how enophthalmos depends upon disappearance of the orbital fat. We often see old persons who have grown so thin and “ hollow-eyed ’’ that the finger can be pushed in deep between the eyeball and wall of the orbit, but notwithstand- ing all this, there is no trace of enophthalmos! As the eyeball lies in the orbit, the fat is only a filling, while the connective tissue is the net in which the eye is suspended. To measure the amount of exophthalmos H. Cohn and others have devised special instruments. The exophthalmometer has not become popular, because the position of the eyeball changes within physiological limits so markedly that a statement that the corneal apex is so many millimeters in front of a certain point on the edge of the orbit cannot be taken to mean that a pathological degree of exophthalmos is present. A comparison between the two eyes is of more value. This is obtained by measuring how many milli- meters the corneal apex of each eye lies behind the same point, say the bridge of the nose. There may be differences here, of course, depending upon asymmetry of the cranium, and these would have no pathological significance. As a rule, a simple guess will answer. It must be remembered, however, that a wide pal- pebral fissure may simulate exophthalmos, a narrow fissure or a moderate ptosis may simulate enophthalmos. 458 DISEASES OF THE ORBIT. 1. INJURIES. (a) Injury by a blunt weapon may cause a fracture of the bony wall of the orbit. On account of the concealed position of the bones of the orbit, the well-known signs of fracture—abnormal motility, pain on pressure, crepitation—can be made out only in exceptional cases. Asa rule we must be content with the history of the case and the demonstration of the presence of blood in the orbital cavity. This will be evidenced by exophthalmos and, per- haps, by subsequent subconjunctival and palbebral hemorrhage (p. 746). The diagnosis is established when the fracture is asso- ciated with one of an adjacent air space (the nasal, temporal sinus or the antrum of Highmore), which produces an emphysema of the conjunctiva and lids, or when the injury to the orbit leads to nasal hemorrhage; in this latter case we may conclude that the fracture involves the median wall of the orbit. Injuries by a blunt weapon not infrequently result in inflammation of the bone or periosteum. This is especially the case in scrofulous or syphilitic individuals. Fractures of the orbital wall may be occasioned without direct contact of the weapon, as from a fall upon the back of the head, for example. In such cases life is so endan- gered by other injuries, such as fractures at the base of the skull, that the effect on the eye becomes subordinate. . Quite exceptionally enophthalmos instead of exophthalmos results from injury to the orbit. This ‘ enophthalmos traumaticus”’ is explained in various ways. It seems to me most probable that the cause is to be sought for in a laceration or rupture of connect- ive-tissue fibers that pass from Tenon’s capsule to different points of the orbit, and act as suspensory ligaments of the eyeball. (2) Injury by a penetrating weapon always leads to more or less laceration of the soft parts. The most common objects causing injury are pitchforks, the horns of cattle, umbrellas, canes, knives, and shot of all kinds. In many cases the diagnosis is established by finding adipose tissue exposed in a conjunctival wound. In other cases the injury may be diagnosticated from the nature and extent of the disturbance of eye movement. The character of the weapon causing the injury must be considered in deciding whether it has remained wholly or in part within the wound. To avoid error, it is best to introduce the point of the finger between eye and orbital wall, and to explore the whole orbit. If touch reveals nothing, the wound should be sounded, but with most careful anti- LUXATIO BULBI—PERIOSTITIS ORBITZ. 459 sepsis. If the foreign body has carried any germs with it, there is inflammation, suppuration, and orbital abscess to be feared. Treatment.—Injuries by a blunt weapon are to be treated by rest and cooling compresses. The wound must be disinfected and bandaged. All foreign bodies must be removed. Since they often lodge in the bony wall of the orbit, the extraction sometimes de- mands the use of strong forceps, but in case the foreign body lies at the roof of the orbit, the proximity of the brain should never be forgotten. Small aseptic foreign bodies, like shot, usually heal en- capsulated; they should not, therefore, be removed without good reasons for it. (c) Luxatio Bulbi.—Ifa wedge-shaped foreign body, the thumb, for example, is crowded between eyeball and external wall of the orbit, it can, by using the external wall as fulcrum, squeeze the eye- ball out of its bed. In parts of Bavaria and America (Virginia, among the negroes) this device is resorted to by contestants to ren- der the opponent incapable of fighting. In Uganda, in Central Africa, masters make their slaves one-eyed in this way, the one- eyed appearance serving as a livery. After the luxation the eye lies in front of the orbit, and the lids are closed in a spasm behind it. The muscles are somewhat lacerated, and stretched so much that eye movements are impossible. Vision is lost, either directly through stretching of the optic nerve, or through the anemia caused by this stretching. Treatment consists in reposition and bandage. Vision may return. 2, INFLAMMATIONS. (2) Periostitis Orbitee.—The disease attacks scrofulous chil- dren and syphilitics, in preference. A blow or a fall upon the edge of the orbitis usually the exciting cause. Since the upper outer and the lower outer edges are most exposed to injuries, these points are most commonly the seat of the inflammation. The dis- ease begins with a dull pain increased by pressure upon a certain spot of the orbital edge. A swelling is gradually developed, which is painful, immovable, and strikingly hard. The skin covering the swelling is red and edematous. A small portion of the swelling now becomes soft and fluctuates, and with perforation there is an escape of thin, watery, foul-smelling pus. Ifa sound is introduced into the fistula, it strikes rough bone,—caries. Foul-smelling pus 460 DISEASES OF THE ORBIT. is continuously poured out of the fistula till, after months or years, all necrosed bone is expelled. Cicatrization of the fistula involv- ing the skin, generally that of the lid, follows. Ectropion and ‘its consequences result ( p. 763). Treatment must be antiphlogistic at the beginning. Leeches to the temple (not on the lid, see #. 746) and cold compresses may help to “scatter” the inflammation. This expectation is not unwarranted, and the treatment may succeed if the periostitis is syphilitic, and is subsequently treated with mercury and iodids. If suppuration is unavoidable, however, the treatment should be with heat, incision, and drainage—proper surgical methods. (6) Orbital Abscess.—This distinct form of the disease may develop from a periostitis if the wall of the orbit instead of its edge is involved. With the pain there is then fever, general prostration, swelling, and redness of the lids, particularly the upper one, ptosis, chemosis of the conjunctiva bulbi, exophthalmos, restriction in eye movement, dilatation of the pupil,and visual disturbance. The patient has an appearance that suggests a blennorrhea ( f. 788) or a panoph- thalmitis (~. 296). The lack of discharge from the conjunctiva excludes blennorrhea positively. The unimpaired or relatively nor- mal condition of the interior of the eye (to the ophthalmoscope) is against the diagnosis of panophthalmitis. The pus spreading in the cellular tissue of the orbit, with an increase in all the symptoms, gradually makes its way to the surface and finds an opening either into the conjunctival sac or upon the lids. As soon as the pus escapes the patient obtains relief, but it takes a long time before the normal condition is restored. An unfavorable result is obviously not excluded, since optic neuritis, sloughing of the cornea and even of the whole eye may cause blindness, or if the inflammation reaches the brain, it may end in death. Not only periostitis orbitee, but also any suppurative or even inflammatory process in the vicinity of the eye, may lead to abscess within the orbit. As examples we have empyema of the orbit, sep- tic thrombosis of a cranial sinus from caries of the inner ear, ulcers of the nose, furuncle and erysipelas of the face, and inflammations about the roots of the teeth. A third group is the metastatic orbital abscess, traceable to infec- tion of the general system by glanders, anthrax, or to pyemia. In the second and third group there is usually a number of small abscesses scattered along the orbital veins. DISTURBANCES OF THE CIRCULATION. 461 The fourth and largest group embraces those cases in which the pus-causing germs have been introduced on the weapon or foreign body producing the injury, and in preantiseptic times on the sur- geon’s instruments, as in squint operations. In some cases it is impossible to discover a direct cause. The prognosis depends upon the cause. Metastatic orbital abscesses generally lead to death. In periostitis of the roof of the orbit there is always danger of perforation into the cranial cavity, since the bone in this region is as thinas paper. In other cases the prognosis is favorable. Treatment consists in finding the spot where perforation is to be expected and then in incision and drainage. As a rule an inci- sion must be made before periostitis can be demonstrated by prob- ing for bare bone. 3. DISTURBANCES OF THE CIRCULATION. (2) Pulsating Exophthalmos.— The internal carotid artery, after passing from the carotid canal in the temporal bone and running by the side of the body of the sphenoid, enters the cavernous sinus, a venous space in the substance of the dura divided by fibrous cords into many compartments (Fig. 156). The artery lies on the wall of this sinus and half of its own bulk protrudes unpro- tected into the lumen of the sinus. If the carotid should be lacerated at this spot the result would be a flow of blood into the sinus and spaces connected with it; that is, an aneurisma arterio-venosum would be produced. The most important connections of the sinus are with the brain and orbit. Since the cerebral veins are prevented from any noticeable expansion by the already well-filled mem- branes of the brain, the effect of an arterial hemorrhage into the cavernous sinus makes itself felt in the ophthalmic veins and its branches, producing a pathological picture called pulsating exophthalmos. The nerves of the orbits (abducens, oculomotorius, trochlearis, and ramus ophthalmicus of the trigeminus) also suffer, since they pass in part through the cavernous sinus (Fig. 756), in part above it. Pulsating exophthalmos has the following signs: There is ex- ophthalmos, usually with displacement of the eye downward, pre- sumably because the vena ophthalmica inferior does not enter the cavernous sinus, or because of its connections with the veins in the sphenoidal fissure (Fig. 757) it is not affected by the stasis. The lids are red, swollen, and marked by dilated veins coming from the vicinity of the eye,—there is ptosis. The conjunctiva is very chemotic and marked by strongly dilated veins. The cornea is t 462 DISEASES OF THE ORBIT. normal or faintly cloudy, and its sensitiveness is reduced. The pupil is dilated and rigid or at least sluggish. Carofis : ¢ Spaces of the a 1 SuULs cavernosus Y\~_ Nervus oculomotorius_ Nervus frochlearis.._ 1h > hes of the, yf ‘PF . £3 Wy) pF: oan Hy yf == dae) ij Fic. 156.—FRONTAL SECTION THROUGH THE Sinus Cavernosus. (A/ter Merkel, drawn by L. Schroeter.) 8 Art. Lacrym. es Art supraorttt ~onco Art. Prontal “ort a--- Art ethmotid ant Art ctliaris: ----- m pina aN Art. ctluarts. ---~-~----\. \ &e\--- EINE OGY Muse. rect stp. Art lecrymealis ! Ormuneating brah Gs fos csc tec tis cin othe Prextus, aberyenaaes Coe ean if } Art etlhmoud, post. Art. centrates retiniae Tena gphalmiiie ~~~ -~~---—-- NAA on. Vopth. super i f \ TTT TEES 9" Worvits oplrcus. Art, qolhalaiint-~~--0 7077 =o Fic. 157.—Tue Veins oF THE OrpitaL Cavity. (After Merkel, drawn by L. Schroeter.) If a finger is placed on the protruding eyeball, there is felt a pulsa- tion and at times a thrill with every heart beat. Near the eye there may be a pulsating tumor. A moderate pressure suffices to PULSATING EXOPHTHALMOS. 463 replace the eye within the orbit, but on removing the finger the former condition at once reappears. The third diagnostic sign is discovered by means of auscul- tation on the eye, the forehead, or the temple. With the pulse there is also heard a vesicular murmur that fades away to a faint sigh during the diastole of the heart. The ophthalmoscope shows a thinness of the retinal arteries, great dilatation and varicosity of the veins; and choked disc in many instances. In spite of these changes visual acuity may be normal, but it is often reduced or obliterated. The patient com- plains of pain in the orbit, forehead, and temple, changing in sever- ity, and of subjective noises that may be so loud as to affect hearing and prevent sleep. Compression of the common carotid in the neck may stop the symptoms at once, but, of course, only so long as compression is maintained. What can cause a rupture of the internal carotid within the caver- nous sinus? (z) An injury, either direct,as a puncture through the orbit, ora penetrating shot; or indirect, as a fracture at the base of the brain; (2) Disease of the arterial wall (arterio-sclerosis, syphilis), which yields to an accidental rise in blood pressure produced by move- ment, cough, or the like. The prognosis is doubtful. The eye may be blinded by kera- titis neuroparalytica (~. 238), keratitis e lagophthalmo, or by neuroretinitis or ischemia retine. Life may be endangered by ‘severe and repeated nasal hemorrhages, or by further changes in the brain. The perforation in the carotid may, however, be blocked by a thrombus and healing result. Treatment.—What happens spontaneously in favorable cases— thrombosis of the cavernous sinus—must be produced if possible by treatment :— p (z) Reduction of blood pressure in the internal carotid by quiet living, rest in bed, restricted diet, and avoidance of liquids ; (2) Interference with the circulation by (a) Compression, or (2) Ligation of the common carotid. In many cases, particularly in those resulting without injury, regulation of life, combined with compression, will bring about a cure. Ifthe cause was an injury, ligation of the common carotid must be resorted to. 464 DISEASES OF THE ORBIT. (2) Thrombosis of the Ophthalmic Vein is not a disease but a symptom. There are septic and marasmatic thromboses. Septic thromboses belong or rather lead to the condition of orbital abscess (. 460). The marasmatic thromboses are but symptoms of a sinus thrombosis, which is characterized by coagulation of blood within the cerebral sinuses extending outward from the brain through the veins leading to it, or producing symptoms of stasis in the territory of these veins. Stasis in the territory of the ophthal- mic vein may arise from sinus thrombosis, and this may be assumed if other symptoms are present as well, such as general marasmus of the patient, disturbance of cerebral func- tions, bilateral appearance of the eye symptoms, and edema behind the ear. The dis- position to this bilateral involvement depends upon the fact that both sinuses are con- nected by oblique passages, and that consequently a clot in one sinus can easily spread into the other. The involvement of the region of the mastoid depends upon the fact that the mastoid vein leads to the descending arm of the transverse sinus, which is in direct connection with the cavernous sinus. Sinus thrombosis always leads to death. (c) Exophthalmic Goiter, Basedow’s Disease, Grave’s Dis- ease.—This must be briefly mentioned here, since, although it is not an essential disease of the eyes, it has noticeable eye symptoms of importance to the diagnosis, which often lead the patient to con- sult the ophthalmologist first. The disease has three principal signs :— (z) Rapid pulse; (2) Enlargement of the thyroid gland ; (3) Bilateral exophthalmos. The pulse beats 100 or more to the minute in full bodily and mental repose, while the least physical exertion or mental excite- ment may raise it to 140 and beyond. The large vessels in the neck are dilated and have a pulsation that is quite noticeable in comparison to the weak radial pulse. The area of heart dulness is increased, the apex beat is stronger and labored. The thyroid gland is moderately enlarged, soft, has a visible and palpable pulsation, and shows a systolic murmur on auscultation. This may all be taken as evidence that enlargement depends chiefly upon dilatation of the blood-vessels rather than upon hyperplasia of tissue. The exophthalmos varies, not only in different cases, but at times in the same patient. The eyes may be pressed back into the orbits by gentle pressure, an evidence that the cause of the exophthalmos is a dilatation of the blood-vessels in the orbit. Even where the exophthalmos is not remarkable there is a decided expansion of the palpebral fissure, and winking is incomplete and infrequent, a condition due to lessened reflex sensitiveness of the cornea and conjunctiva—Svellwag’s symptom. In looking downward the upper EXOPHTHALMIC GOITER. 465 lid does not, as it normally should, descend, but lags behind and the “ white of the eye” becomes, therefore, visible above the cornea, giving the patient a peculiar appearance—v. Graefe's symptom. The incompleteness of closure of the lid causes complaints and such danger as comes from irritation or inflammation of cornea or con- junctiva. The exophthalmos makes convergence difficult ; in one of my cases this was the only reason the patient gave for coming to a physician. In high degrees of exophthalmos there is lagoph- thalmos (/. 760), and at times there are disturbances of lacrimal secretion, it being either too much or too little. Besides the symp- toms in heart, neck, and eye there are numerous other disturbances of the nervous and digestive systems which are discussed in the text-books of internal medicine. The nature of the disease we may, with Friedreich and Sattler, assume to be an injury to certain closely approximate nerve cen- ters, particularly the vagus nucleus (heart), the vasomotor centers controlling the blood-vessels of neck and head, and, finally, the cen- ters for the coordination between looking downward and closing the lids, and for reflex lid movements. These centers can be located in the gray matter of the third and fourth ventricles. The nature of the change in these centers is not yet known. The causes of the disease are as little known. It has been noticed that excision of the thyroid gland, or even the production of artificial atrophy by ligation of its arteries, may either cure or, to some extent, improve this disease. On this fact is based the theory that the cause of the disease is to be found in a pathological secretion of the thyroid, a kind of autoinfection. The whole matter is still very obscure, but, according to this theory, the involvement of the thyroid is the first phenomenon, everything else being results of it. The prognosis is doubtful. The majority of cases recover after an illness of years. This is particularly true of women, who are also more frequently attacked than men. In men, especially in advanced life, the prognosis is unfavorable, since the disease not infrequently leads to death from exhaustion. An acute course of the disease has been observed, ending in either cure or death. Treatment consists in good physical nourishment, mental calm, life in the country or at a sanitarium, This is not the ophthalmic surgeon’s province; he has to do only with the affections of the cornea and conjunctiva, with the exophthalmos or lagophthalmos, 30 466 DISEASES OF THE ORBIT. and with the muscular asthenopia, to the sections on which the student is referred. 4. TUMORS. Every appreciable tumor of the orbit must cause an exophthal- mos, and the direction in which the eye is displaced depends upon the seat of the tumor. A second symptom is disturbance of motility, either because the tumor prevents eye movements mechanically, or because muscles and nerves are matted together and thereby prevented from func- tionating. Both conditions may, of course, occur simultaneously. A third symptom is disturbance of vision; not always present, however. When present, it is due to pressure upon or involvement of the optic nerve, or to retinal or choroidal disease. A fourth symptom is pain. If lacking, it implies benignancy of the tumor ; if present, either benignancy or malignancy. Although these four signs support the diagnosis of a tumor, this is not established until the tumor itself is demonstrable to the touch. Tumors of all kinds have been observed. The most usual will be mentioned here. Tumorsof the lacrimal gland are described on p. 169. (2) Tumors of the Orbital Wall. Osteoma is a lumpy, bony growth of ivory hardness. As a rule it arises from the roof of the orbit. The development is slow and-painless. The diagnosis may be made from its hardness, immobility, and connection with the orbital wall. Syphilis has been assumed as cause in some cases. The prognosis is favorable, as far as life is concerned, even if the growth extends into the orbital cavity. The eyeball may be rendered useless by exoph- thalmos or lagophthalmos. Treatment consists in inunctions of mercury, etc., if syphilis is the cause. Extirpation is admissible, according to Berlin, only when the roof of the orbit—separating orbit from brain—is not involved. If removal is out of the question enucleation of the unavoidably useless eye will save the patient much distress. Lncephalocele, brain hernia, is a prolapse of dura through some congenital aperture between ethmoid and frontal bones, or through any congenital aperture in the orbital roof. This sac contains fluid or brain matter and forms a tumor lying, as a rule, at the inner upper angle of the orbit. ‘The diagnosis is confirmed if the tumor can be dispelled by pressure, while at the same time symptoms of pressure on the brain, such as rolling the eyes and other spasms, are produced. Such a pathological condition leads sooner or later to death. If life is still maintained with such a tumor, nothing can be done to remove it. (6) Tumors of the Optic Nerve. Myxoma or myxosarcoma is a jelly-like tumor about a pigeon’s or hen’s egg in size. The diagnosis rests on a slowly increasing exophthalmos, relatively little disturbance of motility (because the tumor is within the funnel of the muscles), early blindness from TUMORS OF THE CELLULAR TISSUE. 407 papillitis or optic nerve atrophy, and the discovery of a tumor near the optic nerve by introducing the finger between eyeball and orbital wall. These tumors are benign and even after incomplete removal are not given to local relapses. Treatment consists in removal, with retention of eyeball, if possible. The best method of operation is Krénlein’s osteoplasty—sawing through and turning back the temporal wall of the orbit. This permits full view of the space behind the eyeball, so that the tumor can be shelled out, after which the dislodged wall of the orbit is carefully replaced. (c) Tumors of the Cellular Tissue. These are cysts, sarcomata, and vascular tumors. Among the cysts, dermoid and echinococcus vesicles are relatively the most common. Dermoid cysts are always congenital, and are, therefore, usually observed on children. Their contents are fluid or gelatinous; the presence of hairs, teeth, and other structures springing from the epidermic layer, proves that the condition is one in which the external skin has been turned in and subsequently incarcerated. The diagnosis of a cyst rests upon the evidence of an orbital tumor and fluctuation. Echinococcus cyst is distinguished from the dermoid only by the fact that the former is not congenital, grows faster, causes pain, and endangers the eye. Treatment consists in extirpation. Vascular tumors are telangiectasia, cavernous angiomata, and aneurysms. Telangiectasia of the orbit is the same as a “birth mark”’ on skin or lid (g. 767). The cavernous angioma lies within the funnel of the muscles, and therefore does little damage to eye movements. The essential sign of it—apart from those characteriz- ing all tumors—is the changing increase and decrease in size, noticed continuously or produced at will, by bending forward, for example, or by forced expiration; in short, by anything that retards the return of blood from the head. The exophthalmos accompany- ing it can be overcome by pressure on the eyeball. Prognosis is good so far as concerns life, but doubtful for the eye. However long the tumor may take in growing, the result is sure to be pressure atrophy of the optic nerve, or inflammation of the eye. Treatment must be extirpation. Aneurysms have the above symptoms with the addition of pulsation. If they are quite large, they may produce the picture of pulsating exophthalmos. In such a case the same treatment is advisable (f. 463). Sarcomata are usually within the eyeball (/. 297) or on its anterior surface (f. 278), and have therefore been already mentioned ; a genuine orbital sarcoma is a great rarity. Its malignancy is betrayed by its rapid growth, pain, and early effect upon health. There is, besides, a disturbance quite out of proportion to the size of the tumor, due, of course, to involvement of the muscles within the growth; an innocent tumor merely pushes the muscles to one side and, therefore, affects movement only mechanically. The prognosis is bad,—the more unfavorable the younger the patient and the richer in cells the tumor is. Treatment consists in evisceration of the orbit, exenteratio orbitee; the operation is performed as follows: the external canthus is split and the lids drawn as widely apart as possible, in order to get space. A knife is then passed around the entire bony circum- ference of the orbit, and the orbital periosteum, beginning at the wound, is loosened by raspatorium or chisel; this is continued until the entire periosteum with all its contents is separated from the bony wall, being left adherent only at the apex of the orbit. A scissors curved on the flat is then introduced, and the stump of this mass of tissue is cut off close to the bone. Hemorrhage from the ophthalmic artery is best stopped by the actual cautery. If the lids are involved in the growth, the first incision should be carried beyond it into healthy skin, and lids removed with orbital contents. APPENDIX A. ABBREVIATIONS USED IN OPHTHALMOLOGY. (Gould’s Itlustrated Dictionary, page x.) Acc . Accommodation. L.M. . Light Minimum. Ah, . Hyperopic Astigmatism. M. . . . Myopia, Myopic. Am . Myopic Astigmatism. m... . Meter. As. . Astigmatism. mm. . . Millimeter. Ax. Axis. O.D.. Oculus dexter—Right Eye. B.D.. . Base (of prism) down. O.S.. . Oculus sinister—Left Eye. But... ge ER Says 0.U.. . Oculi utrique—Both Eyes. B.O.. Se OTE EE Out P. p. . . Punctum proximum, Near Point. BoUss 3 te 8 8 cup, P.r. . . Punctum remotum, Far Point. cm. . Centimeter. R.E.. . Right Eye. Cyl. . Cylinder, Cylindric Lens. Sph. . Spheric, Spheric Lens. D. Diopter. Sym.. . Symmetric. E. . Emmetropia, Emmetropic. Vv. . Vision, Visual Acuity, Vertical. F, . Formula. +,—,= Plus, Minus, Equal to. H. - Hyperopia, Hyperopic, Hori- . Infinity, 20 ft. distance. zontal. ce . Combined with. L.D.. . Light Difference. a . Degree. L.E.. . Left Eye. a FT] TUT TTT IUTPTTT ITTATTTTT ITT ITTTYTITT TTTTYUTTT TTT TTT] TTT HITT nl 44 2) #3} 4 5} 6 66}lhU7])hlU8}l hU8} SCO ns 2 Ayotugn as oddest tlio das toot ae ta PEU[TTTP UTE PTTTPEETP TTT] TT] EEEPEET TTT] ETT] TTP TTT ETT PETE ETT PTET Z 2 3 4, 5 utnibii title Le Fic, 158.—A. Centimeters. B, Inches. 469 Fel 1 € 6x =| z $b1} x v z % z z 9 |1 L I G11) z v I for] 1 £ I She ee Vz, I Z£1 Sar ggi| z L oe . £ Ise L ad * ai ]1 L . Q ea te a for; = fo |° he tr | z 9 < ge Be Qh he Sor a ae 9 . S | S a8. 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ETYMOLOGIES. (Condensed from Gould's Illustrated Medicai Dictionary, 2d Ed.) A Acne [4y77, a point] a disease of the sebaceous glands. Amaurosis [dyavpéecv, to darken] par- tial (or total) loss of vision. Amblyopia [auGAbc, dulled; 7 Swe, the eye] subnormal acuteness of vision. Ametropia [4 priv. ; érpov, a measure ; dyuc, sight] the formation of an im- perfect image on the retina, due to defective refractive power of the media (or to some abnormality of the eye). Amyloid [déyvAov, starch; eidoc, form] starch-like. Anemia [4 priv.; aia, blood] (blood- less); deficiency of blood; gener- ally understood as being due to re- lative reduction in the number of red blood corpuscles. Angioma [dyyeiov, a vessel; dua, a tumor] a tumor formed of blood- vessels, Anisokoria [dvooc, unequal; «xopf, pupil] inequality in the diameter of the pupils. Anisometropia [dévooc, unequal ; pér- pov, a measure; dp, the eye] a dif- erence of refraction in the two eyes. Ankyloblepharon [ay«bdy, a loop; Brédapov, the eyelid] adhesion of the ciliary edges of the eyelids. Anthrax [dv6paé, a coal or carbuncle] inflammation in the cellular tissue, due to a specific bacillus. Aphakia [4 priv.; gaxdc, the crystal- line lens] the condition of the eye without the lens. Aplanatic [@ priv.; wAavdew, to wan- der] rectilinear lens, corrected -for aberration of light and color. Arcus senilis [avcus, a bow; sendlis, of the old]. Asthenopia [a priv.; afévoc, strength] weakness or speedy fatigue of visual power, Astigmatism [4 priv. ; oriyya, a point] rays not brought toa point or focus. Atrophy [a priv. ; tp0¢4, nourishment] a condition marked by wasting or innutrition. B Blennorrhea [GAévva, mucus; péecy, to flow] excessive mucous discharge. Blepharadenitis [@é¢apov, the eyelid; adj, a gland; er, inflammation] inflammation of the Meibomian glands. Blepharitis [G2é¢apov, the eyelid; etic, inflammation] inflammation of the eyelid. Blepharophimosis [SAé¢apov, the eye- lid; ¢izworc, shutting up] abnormal smallness of the palpebral fissure. Bothriocephalus [Gofpiov, a pit ; cedarg, head] a species of tapeworm. Bullosa [éu//a, a blister] with blisters or blebs. Buphthalmos [fovc, an ox; ofbarudc, eye] ox-eyed. Cc Cancroid [cancer, a crab] cancer-like, semi-malignant. Cataract [xatapd«rye, a falling down or over] opacity of the lens or its cap- sule. Catarrh [karappéecy, to flow down] in- flammation of a mucous membrane. Chalazion [yaddgcov, a small hail- stone] a Meibomian cyst. 471 472 Chemosis [yfywore, a gaping] a swell- ing (sub-conjunctival). Choroid [,épiov, skin; eidoc, like] the vascular tunic of the eye. Chromatic [ypoya, color] relating to color. Chromidrosis [ypaya, color; sweat] colored sweat. Coloboma [xoAoBdew, to mutilate] a fis- sure of parts of the eye, congenital or traumatic. Coma [xapya, deep sleep] abnormally deep or prolonged sleep. Corectopia [xép7, the pupil; misplaced] displacement pupil. Cornea [corneus, horny] the anterior transparent segment of the eyeball. Cyclitis [«ixtoc, a circle (around the eye); utc, inflammation] inflamma- tion of the ciliary body. Cysticercus [xbori, a bladder ; xépxoc, a tail] scalex of the tapeworm. Hydatid. idpdc, éxToroc, of the D Dacryocystitis [ddxpvor, a tear; Kboric, a sac] inflammation of the lacrimal sac. Dacryocystoblennorrhea [daxpuov, a tear; xhoric, a Sac; B2Aévva, Mucus; poia, a flow] flow of tears from the lacrimal sac. Dacryolith [ddxpvov, a tear; Alfoc, a stone] a lacrimal calculus. Dacryops [déxpvorv, a tear; oy, the eye] watery eye. Daltonism [Dalton, an English phy- sicist] color-blindness. Dendritica [dévdpov, a tree] tree-like. Dermoid [dépya, skin ; eldoc, like] like the skin. Dialysis [d:4, through ; Ate, to loose] passing through. Diopter [d:d, through ; dwecbac, to see] the metric unit of measurement for optical lenses. Distichiasis [dic, double ; atiyoc, row] double row of eyelashes. E Ectasia [éxraow, extension] abnormal distention or dilatation of a part. Ectropium [éx, out; tpévecv, to turn] eversion (of an eyelid). APPENDIX. Eczema [éx¢éew, to boil over] a ca- tarrhal inflammatory disease of the skin. Edema [oidnjua, a swelling] swelling, due to effusion of serous fluid into areolar tissues. Emmetropia [é», in; yérpov, measure ; ow, eye} normal vision. Emphysema [éy¢voderv, to inflate] ab- normal collection of air in the con- nective tissue. Encephalocele [éyxé¢atoc, brain ; KfAn, tumor] a hernia of the brain through a cranial fissure. Enophthalmos [év, in; d¢6aApdc, eye] recession of eyeball into the orbit. Entozoon [évréc, within ; Cdov, an ani- mal] an animal parasite within an- other animal, Entropium [ev, in; zpérev, to turn] inversion (of the eyelid). Epicanthus [ézi, on; xavOéc, angle of the eye] a fold of skin passing from nose to eyebrow. Epiphora [é7/, on; gepeiv, to bear] a persistent overflow of tears. Erythropsia [épvpéc, red ; dye, vision | red vision. Esophoria [éow (or ciow), within; gop- eiv, to bear] tending of the visual line inward. Exophoria [éw, without; ¢opeiv, to bear] tending of visual line outward. Exophthalmos [Z£, out ; d¢0a%pdc, eye] abnormal prominence of eyeball. F Furuncle [ furunculus, Lat. Sanskrit), to burn] a boil. G Gerontoxicon [yépw», an old man; 7éSov, a bow]. See Arcus senilis. Glaucoma [y/avxéc, sea-green] a dis- ease of the eye; so-called on ac- count of the green color. Glioma [y4ia, glue; dua, tumor] a variety of round-celled sarcoma. H Hemeralopia [jyépa, day; 4, eye] day-vision or night-blindness. (See note under Wyczalopia.) Hemianopsia [yju, half; a _ priv.; éyuc, sight] blindness in one-half of the visual field. (from APPENDIX. Hemorrhage [aiya, blood; pyyviva, to burst forth] bleeding from wounded vessels. Herpes zoster [éprnc, creeping ; Cwo- tap, a girdle] an inflammatory skin disease, characterized by vesicles. Heterochromia [érepoc, different; xpoua, color] a difference in color (in the irides). Heteronymous [érepoc, different; dvuya, name] of a different name or char- acter. Crossed. The opposite of homonymous. Heterophoria [érepoc, different ; dopdc, tending] a tending of the visual lines other than to parallelism. Hippus [izroc, the horse] spasmodic pupillary movements, independent of the action of light. (Natural in the horse.) Homonymous [éudéc, same; dvoya, name] occurring on or within the same lateral half of the body. Hordeolum [ardeum, barley] a stye. Horopter [époc, boundary ; ézryp, an oe a line representing the curve along which both eyes can join in sight. Hyaline [tadoc, glass] glass. Hydrophthalmos [idwp, water; 6¢0aa- uéc, eye] increase in the fluid con- tents of the eye. Hydrops [idpuy, dropsy] an abnormal collection of fluid in any part of the body. Hyperemia [izép, over ; aia, blood] a congestion of blood. Hypermetropia [irép, over; pértpor, measure; oy, eye]. See Wyperopia. Hyperopia [iep, over; Hy, eye]. That condition of the refractive media of the eye in which, with suspended accommodation, the focus of paral- lel rays of light is behind the retina ; it is due to an abnormally short an- tero-posterior diameter of the eye, or to a subnormal refractive power of its media. Hyperphoria [irep, over ; dopdc, tend- ing] a tendency of a visual line up- ward. Hyphema [imé, under ; aiua, blood] a deposit of blood on the floor of the anterior chamber. resembling 473 Hypophoria [ind, under; gopdc, tend- ing| a tendency of a visual line downward, Hypopyon [izé, under; ziov, pus] a collection of pus in the anterior chamber. Hysteria [torépa, the womb] a nervous disorder, once supposed to arise from the womb. I Iridectomy [ipic, iris; éxtouf, excision] cutting out part of the iris. Irideremia [ipic ; épyuia, lack] absence of one or both irides. Iridodialysis |ipi ; deadiecy, to liberate] release of iris at its ciliary border. Iridodonesis [ipic ; dévyorc, trembling] tremulousness of the iris. Iridoplegia [ipec; 7/4, stroke] paraly- sis of sphincter of the iris. Iridotomy [ipic; Tous, a cutting] inci- sion into the iris. Iris [ipec, a colored halo or circle] the anterior portion of the vascular tunic of the eye. Iritis [ipec; etic, inflammation] inflam- mation of the iris. Ischemia [ficyev, to check; blood] bloodlessness. aipa, K Karyokinesis [xdpvov, a nut (= nu- cleus); «iyo, change] changes accompanying maturation of the ovum, Keratitis [xépac, horn (= cornea) ; irc, inflammation] inflammation of the cornea. Keratocele [xépac, cornea; «/27, tumor] a hernia of Descemet’s membrane through the cornea. Keratomalacia [xépac, cornea ; vadakia, softness] softening of corneal tissue. Keratoscopy [xépac, cornea; oxoreiv, to observe] examination of the cor- nea. Kopiopia [xdéroc, straining; op, eye] eye-strain. Weariness of the eyes. Korectopia [xépy, the pupil of the eye (so-called, like the Latin pupzt/a, be- cause an image appears in the eye) ; éxtoroc, misplaced] displacement of the pupil. 474 L Lagophthalmos [Aaydc, hare; d¢Garpdc, eye] inability to close the eyes (from the popular notion that the hare sleeps with his eyes open). Lens [Lat., a lentil] a regularly shaped transparent object refracting lumin- ous rays. Leukemia [Aevxée, white ; aiua, blood] a condition of the blood, character- ized by a relative increase in white corpuscles. Leukoma [Aebcouc, anything white] a white spot on the eye. Leukosarcoma [Aevséc, white; cap- xwua, fleshy tumor] non-pigmented sarcoma. Lithiasis [2/@0c, a stone] a callosity within the eye-lid. Lupus [Lat., a wolf] a skin disease due to the tubercle bacillus. Luxatio [2déZ0c, slanting (Lat., 06- figuus) | dislocation. M Macropsia [waxpéc, large ; duc, sight] apparent increase in the size of ob- jects. Malacia [yaaxia, softening] morbid softening of tissue. Marantic [uapaivay, to make lean] marasmus ; general mal-nutrition. Melanosarcoma [wéAac, black; capé, flesh; dua, tumor] pigmented sar- coma. Metamorphopsia = [yerapopdderv, to change shape; dyuc, sight] appar- ent change in the form of objects. Metamorphosis [yerayopddew] struc- tural change in passing from the embryo to the adult. Microphthalmos [suwxpdc, small ; 6¢6a2.- péc, eye] a small (not pathological) eye. Micropsia [xpdc, small; dic, sight] apparent decrease in the size of ob- jects. Miosis [jeiworc, a lessening] decrease in size of the pupil. Mydriasis [jvdpiaoie ] abnormal dilata- tion of the pupil. Myodesopsia [jzwoecdije, like a fly ; dyc, vision] subjective appearance of muscee volitantes. APPENDIX. Myopia [ytevv, to close ; &W, eye| near- sightedness. Because near-sighted people partially close the lids. Myotomy [yéc, muscle; rou#, cutting] incision of a muscle. Myxoma [yifa, mucus; dua, tumor] connective-tissue tumor. N Nyctalopia [viz, night; oy, the eye] night-vision or day-blindness. Night-vision; the condition in which the sight is better by night orin semi-dark- ness than by daylight. It is a symptom of central scotoma, the more dilated pupil at night allowing a better illumination of the peripheral portions of the retina. Dr. Greenhill and Mr. Tweedy have shown that according to the quite universal usage of modern times, the definitions of the words, myctalopia and hemeralopia, have been the reverse of that of the early Greek and Latin writers. The proper derivation therefore of zyctalopia would be from vié, night, dAadc, blind, oy, eye, the word meaning night-blindness. Hemeralopia was likewise derived from jyépa, day, aradc, blind, &~, eye, and meant day-blindness. The attempt to reinstate the ancient usage can only result in utter confusion, and the words should therefore never be used. See flemeralopia. Nystagmus [vorayydéc, nodding of the head] oscillatory movement of the eyeballs. Oo CEdema. See Edema. Ophthalmometry [d¢fadudc, eye; pér- pov, measure] mensuration of the eyeball, or ef the corneal curves. Ophthalmoplegia [d@Oadrudc; mAnyy, stroke| paralysis of the ocular mus- cles. / Ophthalmoscope [6¢6aAyuéc¢ ; oxoreiv, to observe] instrument for examining the interior of the eye. Ophthalmotonometer [d¢@aAuéde ; Tévoc, tone; uérpov, measure] instrument for measuring intraocular tension. Optogram [ézréc, visible; ypddecv, to write] a faint image stamped on the retina for a brief period. Orthophoria [op6dc, straight; opdc, tending| tending of the visual lines to parallelism. APPENDIX. P Pannus [Lat., cloth] vascularization of the cornea. Panophthalmitis [méc, all; d¢Oadude, eye; cree, inflammation] inflamma- tion of all the tissues of the eye-ball. Parallax [mapd, beside; adAoc, other] apparent displacement of an object. Paralysis [apd ; bev, to loosen] loss of power of motion in a muscle. Paresis [rapd, from ; iévar, to let go] partial loss of motion in a muscle. Periscopic [repi, around; cxozeiv, to see] applied to lenses having a con- cave surface on one side and a convex on the other. Phakomalacia [@axdéc, lens; jadaxia, softness] soft cataract. Phimosis [¢oiv, to constrict] abnor- mal smallness (as of the palpebral fissure). Phlyctenula [dim. of ¢Ab«rawa, blister] a small vesicle or blister. Photometer [¢éc, light ; uérpov, meas- ure] instrument for measuring the intensity of light. Pinguecula [Lat., dzmguzs, fat] a small tumor of the conjunctiva bulbi. Polioencephalitis [rodiéc, gray ; éyxéda- Aov, brain; eric, inflammation] in- flammation of cortical gray matter. Presbyopia [mpécBue, old; &p, eye] old-sight.” Pseudo-iso-chromatic [pevdic, false ; ico, equal; ypua, color] similarly colored only to those with color amblyobia. Pterygium [répvf, wing] a triangular patch of thickened conjunctiva. Ptosis [xréouc, rinrevy, to fall] drooping of the upper eyelid. Pyorrhea [mtov, pus; pola, a flow] a purulent discharge. R Rhinorrhaphy [fvc, the nose ; pag, su- ture] reduction of the tissue of the nose by section. Ss Sarcoma [odpé, flesh; dua, tumor] a connective-tissue tumor. Sarcomatosum [odp, flesh; ya, tumor] of the nature of sarcoma. 475 Scintillans [sczn¢illare, to sparkle] emitting sparks, Scotoma [oxordev, to darken] a fixed spot in the field of vision, corre- sponding to some abnormality in the retina or optic centers in the brain. Seborrhea [sebum, suet; pola, a flow] an increase of sebaceous secretion. Skiascopy [oxia, shadow; oxoreiv, to observe] the shadow-test. Staphyloma [oragvag, grape; sya, tumor] a grape-like protuberance of cornea or sclera. Stenopaic [orevic, narrow; éraioc, pierced] a disk with a narrow open- ing. Strabismus squint. Synchisis [cbyyvovc, a mixing together] a confusing effect. Synechia [cbv, together ; éyev, to hold| a morbid union of parts. T Tarsorrhaphy [rapodc ; padh, suture] an operation upon the eyelids. Tarsus [rapoéc, the tarsus (a flat sur- face) | the cartilage of the eyelid. Teichopsia [reZyoc, wall; dye, vision ] temporary amblyopia, with subjec- tive visual images like fortification angles. Telangiectasis [réAoc, end; ayyeiov, vessel; éxraowc, stretching] dilata- tion of capillaries. Tenotomy [révwv, tendon; réuvewv, to cut] tendon cutting. Trachoma [rpaybc, rough] granular conjunctivitis. Trichiasis [@pig, a hair] abnormal po- sition of the eyelashes. U Uremia [oipov, urine; alya, blood] symptoms of blood poisoning from retained urinary excretions. Uvea [Lat., a grape (from its color) ] the middle tunic of the eye. x Xanthelasma [Earféc, yellow ; éaopa, a plate (lamina) | spots of yellowish discoloration. : Xanthoma [£av6éc, yellow ; dua, tumor] a yellowish new growth on the skin. Xerosis [Efpwouc, dry] a dry condition. [orpaBivew, to squint] INDEX. A Aberration, spherical, 343, 380 Abscess of cornea, 230 ~ of lid, 145 of orbit, 460 Abscission of iris, 258 Accommodation, 17, 25 binocular, 79 decrease of, with age, 45 measure of, 41 paralysis of, 288 by atropin, 270 range of, 41 spasm of, 289 Acne, 152 Acuity, visual, 33 determination of, 34 differences in, 34 of the retinal periphery, 63 Adaptation, 56 Adenoid, of lacrimal gland, 169 Advancement of muscle, operation for, 447 of Zenon’s capsule, 447 Albinism, 283 Alcoholic amblyopia, 327 Amaurosis, 383 from alcohol, 327 from malarial fever, 389 from quinin, 389 from tobacco, 327 from uremia, 389 partialis fugax, 392 progressive, 329 Amaurotic ‘‘ cat’sseye,”” 319 Amblyopia, 383 color, 385 diabetic, 389 ex anopsia (from disuse), 383 from cerebral disease, 390 intoxication, 327 tobacco, 327 Ametropia, 22 Amyloid, of conjunctiva, 219 Anel's syringe, 178 Aneurysm, arterio-venous, 461 of orbit, 467 Angioma of lids, 167 Angioma of orbit, 467 Angle, alpha, 83 gamma, 83 of deviation, 90 of squint, 83 of vision, 34 refracting angle of prism, 91 Anisokoria, 269, 284 Anisometropia, 381 Ankyloblepharon, 156 Anterior capsular cataract, 225 nodal point, 23 synechia, 230 Anthrax, 145 Aphakia, 356 Apoplexia subconjunctivalis, 215 Arcus senilis, 251 Arteria centralis retinz, 124 hyaloidea persistens, 360 Arterize ciliares, 267 Arterial pulse, 305 Artery, embolism of retinal, 311, 312 Artificial eye, 422 pupil (see Iridectomy) Associated movements, disturbances of, 437 Asthenopia— accommodative, 363 muscular, 368, 450 nervous, 385 Astigmatism, 47, 376 irregular, 379 kinds of, 50 measure of, 51 physiological, 376 regular, 47, 376 with and against the rule, 377 Atrophic excavation of disc, 397 Atrophy, descending, 330 optic nerve, 327 simple, 329 Atropin, 270 conjunctivitis from, 98 follicles from, 98 in iritis, 275 in keratitis, 226 to paralyze accommodation, 41 Axis of eye, 83 477 478 Axis of rotation, 78 of vision, 83 Axis-myopia, 373 B Band (ribbon) opacity of cornea, 253 Basedow's (Grave's) disease, 464 Beer's knife, 348 Bettman’s artificial ripening of cata- ract, 345 Binocular lens of Aubert, 99 of Zehender-Westten, 99 vision, 70 Birth-marks, 167, 467 Bladder worm, 408 Blennorrhea, 188 neonatorum, 190 of conjunctiva, 188 Blepharadenitis, 149 Blepharitis, 149 ciliaris, 149 hypertrophica, 149 simple, 149 squamosa, 150 ulcerosa, 149 Blepharophimosis, 156 Blepharospasm, 158 Blinding (dazzling) of retina, 320 Blindness (see also Amblyopia and Amaurosis) color, 385 Blood-vessels in the uveal tract, 267 Body, ciliary, 267 Bothriocephalus, 411 Bowman's membrane, 220 sounds, 176 Bruecke's muscle, 267 Buphthalmos congenitus, 400 Burns of conjunctiva, 216 of cornea, 251 c Canalis Clogueti, 269 Petits, 333 Schlemmit, 269 Cancer (see Carcinoma) Canthoplasty, 158 Canthus externus and internus, 143 Carcinoma of conjunctiva, 219 of lid, 165 Cardinal points, 22 Caruncula lacrimalis, 143 Cataract (see also Cataracta), 333 artificial ripening of, 345 capsular, 333 causes of, 343 complete, 333 INDEX. Cataract, extraction of, 347 in the capsule, 351 linear, 349 forms of, 335 from lightning, 343 naphthalin, 344 salt, 343 sugar, 344 hard, 335 instruments for, 347 lamellar, 342 soft, 339 treatment of, 344, 351 Cataracta accreta, 333 calcaria, 339 capsularis, 333 centralis, 341 posterior, 339 complicata, 333 congenitalis, 339 corticalis, 333 diabetica, 344 dura hypermatura, 338 sypsea, 339 hypermatura, 338 immatura maturescens, 337 incipiens, 337 juvenilis, 339 lactea, 339 lenticularis, 333 matura, 338 membranacea, 339 Morgagniana, 338 nigra, 332 nuclearis, 333 polaris posterior, 341 pyramidalis, 341 secondaria, 340, 354 accreta, 355 senilis, 335 stationaria, 341 traumatica, 339 Catarrhal ulcer of cornea, 234 Catarrhus siccus, 183 “Cat’s-eye,”” 319 Cautery in corneal diseases, 227 Centering of refractive media, 18 Cerebrocele (see Encephalocele) Chalazion, 154 terreum, 156 Chemosis conjunctive, 188 Chiasm, optic, 304 Chloroma, 169 Choked disc, 322 Choroid, anatomy of, 267 coloboma of, 301 detachment of, 300 diseases of, 290 prolapse of, 300 INDEX. 479 Choroid, rupture (laceration) of, 300 sarcoma of, 297 tuberculosis of, 296 warts of, 301 Choroidal ring, 122 Choroiditis areolaris, 293 centralis circumscripta, 293 diffusa, 291 disseminata, 291, 369 embolica, 296 exudativa, 290 metastatica, 296 septica, 296 suppurativa, 295 chronica, 296 Chororetinitis centralis, 293 syphilitica, 294 Chromidrosis, 148 Cicatricial opacity, 253 Cilia (see Lashes) Ciliary body, 267 diseases of, 286 forceps, 150 injection, 222 muscle, 267 paralysis of, 288 paresis of, 288 spasm of, 289 neuralgia, 222 processes, 267 Circular rotation, 77 synechia, 274 Circulus arteriosus iridis minor, 266 major, 268 Circumcision, 242 Cocain, 270 in iritis, 276 opacity from, 252 Coloboma, artificial, 282 of choroid, 301 of iris, 283 of lid, 165 Color amblyopia, 385 blindness, 385 sense, 57 tests for, 58, 59 Commotio retinz, 320 Cones of retina, 301 Conical cornea, 260 Conjugate deviation, 437 Conjunctiva, anatomy of, 181 burns of, 216 diseases of, 181 foreign bodies in, 214 hemorrhage of, 215 hyperemia of, 183 transplantation of, 217 tumors of, 218 wounds of, 215 Conjunctival catarrh, chronic, 183 Conjunctivitis blenorrhoica, 188 catarrhalis, 185 estiva, 206 chronica, 183 crouposa, 193 diphinentiea, 194 eczematosa, 207 follicularis, 196 gonorrhoica, 190 granulosa, 199 lymphatica, 207 membranacea, 193 phlyctenulosa, 207 purulenta, 188 scrofulosa, 207 sicca, 183 simplex, 185 trachomatosa, 199 tuberculosa, 206 Contractures, secondary, 433 Conus, 369 Convergent squint, 84, 440 Corectopia, 283 Cornea, abscess of, 230 anatomy of, 220 burns of, 251 eczema of, 231 facet of, 224 fistula of, 225 frigeration of, 251 inflammations of, 221 injuries of, 247 leukoma of, 254 macula of, 254 nubecula of, 254 opacities of, 251 perforation of, 225 phlyctenule of, 231 protrusions of, 257 puncture of, 228, 405 reflection from the, 96 staphyloma of, 257 transplantation of, 256 tumors of, 261 ulcers of, 222, 234 Corneal ellipse, 48, 84 necrosis, 240 opacities, 251 puncture, 405 ulcer, 234, 235 “Corpus alienum,” 249 Corpus ciliare, 267 vitreum, 360 Cover points, 72 Crab’s eye, 214 Crede’s method, 191 Creeping corneal ulcer (see Ulcus serpens) 480 Cyclitis, 286 plastica, 287 serosa, 287 suppurativa, 288 Cyst of conjunctiva, 218 of iris, 282 of lid edge, 166 Cysticercus, 407 Cystitome, 347 Cystoid scars, 406, 407 D Dacryocystitis, 172, 174 Dacryocystoblennorrhea, 172 Dacryolith, 172 Dacryops, 170 Dacryorrhea, 188 Daltonism, 385 Dark spot, 69 Davtel’s incision, 348 spoon, 348 Dayblindness (see Nyctalopia) Dazzling of retina, 320 Decussation of optic nerves, 303 Deposits on Descemet's membrane, 247 Depression (for cataract), 346 Dermoid, of conjunctiva, 218 cyst of orbit, 467 Descemet’s membrane, 221 deposits on, 247 Detachment of choroid, 300 of retina, 315 Deviation, angle of, 90 primary, 441 secondary, 441 Diabetic amblyopia, 389 cataract, 344 Dieffenbach's operation, 165 Diffusion theory, 317 Dilatator pupillze, 266 Diopter, 32 Diphtheria of conjunctiva, 194 Diphtheritic corneal ulcer, 235 Diplopia (in squint), 425 Disc, optic (see Optic disc) Discission, 340, 346 Dislaceration, 355 Distichiasis, 153 Divergence, facultative, 451 Divergent squint, 449 Double images (in paralysis), 425 e¢ Seg. Douche for eye, 185 Dry catarrh, 183 Duboisin, 270 INDEX. E Echinococcus cyst of orbit, 467 Ectasia, 264 ciliaris, 264 equatorialis, 264 intercalata, 264 of sclera, 263 Ectopia lentis, 358 Ectropium, 163 cicatricial, 164 sarcomatosum, 163 Eczema from sublimate, 145 of conjunctiva, 207 of cornea, 231 of lid, 144 ulcer from, 232 Edema of lid, 147 Egyptian ophthalmia, 199 Election, position of, 451 Embolism of retinal artery, 311, 312 Emmetropia, 22 Emphysema of lids, 148, 458 Encephalocele, 466 Enophthalmos, 457 traumaticus, 458 Entozoa (see Parasites), 401 Entropium, 161 Enucleation, 421, 422 Epicanthus, 165 Epiphora, 170 Episcleritis, 262 migrans, 262 Equilibrium, test for muscular, 92 Errors of refraction, 362 Erythropsia, 358 Eserin, 270 in glaucoma, 404 Esophoria, examination for, 93 treatment of, 453 Estimation of refractive conditions, 12 oun, 467 Excavation of disc, atrophic, 397 glaucomatous, 398 physiological, 124, Exclusion of imdeer ss regional, 442 Excursional field, 82 Exenteratio bulbi, 296, 422 orbiti, 467 Exophoria, examination for, 93 treatment of, 453 Exophthalmia fungosa, 319 Exophthalmic goiter, 464 Exophthalmometer, 457 Exophthalmos, 160, 433, 457 pulsating, 461 INDEX. Exostosis of orbit, 466 Extraction of cataract, 347 Eyeball, injuries to, 411 rupture of, 414 Eye douche, 185 foreign bodies within the, 415 movements of, 76, 425 muscles, action of, 78 F Facultative divergence, 451 Fadchen-Keratitis, 238 False projection, 71 Far point, 30 Farsightedness (see Hyperopia) Fatty tumor of conjunctiva, 211 Fick's tonometer, 138 Field of excursion (see Excursional field) of vision (see Visual field) Filaria, 411 Filtration angle, 269 scar, 407 ‘Fissure, interpalpebral, 156 narrowed, 156 widened, 159 Fistula of cornea, 225 of lacrimal gland, 170 of lacrimal sac, 174 Flarer’s incision,. 162 “Flying specks,” 361 Fluidity of vitreous, 362 Fluorescin test, 222 in wounds of conjunctiva, 216 of cornea, 222 Focal distance of lenses, 32 illumination, 98 interval, 50 line, 48 point, anterior, 21 posterior, 20 Follicular catarrh, 196 Foreign body in conjunctiva, 214 in cornea, 249 in eyeball, 415 in iris, 280 in orbit, 458 Fossa patellaris, 331 Fracture of orbital bones, 458 Frigeration of cornea, 251 Fukala, extraction of lens in myopia, 376 Function tests, 17 Fundus, normal, 123 examination of, 119 Furuncle, 145 Fusion, range of, 80 31 481 G Gaillard’s suture, 162 Galvanocautery in corneal ulcer, 227 Gelsemin, 270 Gerontoxon, 251 Glands, lacrimal, 167 Metbomian, 143 Mollian, 143 Glaucoma, 392 absolutum, 396 acutum, 395 evolutum, 395 fulminans, 396 hemorrhagicum, 403 infantile, 400 inflammatorium, 395 pathology of, 401 primary, 395 secondary, 400 simplex, 396 theories of, 402 treatment of, 403 varieties of, 395 Glioma retinz, 318 Goiter, exophthalmic, 160 Gonococcus of /Vezsser, 190, 464 Graefe’s and v. Graefe’s tests, 92 incision for cataract, 349 symptom, 465 Granulations (see Trachoma) Granuloma of iris, 279 Grave’s disease, 464 Green cataract (see Glaucoma) Gumma of ciliary body, 286 of iris, 279 H Haab’s magnet operation, 418 reflex, 270 ffartnack's lenses, 99 Hemeralopia, 56, 294, 313, 383 Hemianopsia, 390 transient, 392 Hemophthalmos externus, 146 Hemorrhage— into anterior chamber, 280 into conjunctiva, 215 into lid, 146 Hernia, cerebral, 466 Herpes febrilis (/Yorner), 236 zoster cornea, 235 ophthalmicus, 143 Heterochromia, 283 Heterophoria, 93, 452 Hippus, 286 firschberg’s magnet operation, 418 measurement of squint, go 482 INDEX. flolmgren's color test, 58 Homatropin, 270 Hordeolum, 152 Horopter, 73 “ Flutchinson's teeth,” 244 Hyaline degeneration, 220 Hyaloid, 220 Hydrophthalmos congenitus, 400 Hydrops of lacrimal sac, 172, 175 of optic nerve-sheath, 323 Hyoscyamin, 270 Hyperemia of conjunctiva, 183 of iris, 271 of retina, 306 Hypermetropia (see also Hyperopia), 37 Hyperopia, 363 absolute, 367 facultative, 366 kinds of, 37 latent, 4o manifest, 40 Hyperphoria, 93, 452 Hypertrophia epithelialis estiva, 206 Hyphema, 280 Hypophoria, 93 Hypopyon in cyclitis suppurativa, 288 in iritis suppurativa, 278 keratitis, 229 I Identical retinal points, 72 Illumination, oblique or focal, 98 Images, retinal, displacement of, 71 Incision of Davie/, 348 of Flarer, 162 of Jacobson, 351 Infantile glaucoma, 400 Injury to eye as a whole, 411 to orbit, 458 Insufficiency of externi (see Eso- phoria) of interni, 449 Intention trembling, 456 Intermarginal portion of lid, 142 Intoxication amblyopia, 389 Inverted image, 106 Iridectomy—the operation, 280 for glaucoma, 405 for optical purposes, 256 Irideremia, 283 Iridocyclitis, 286 serosa, 277 Iridocyclochoroiditis, 286, 291 Tridodialysis, 280 Iridodonesis, 286, 413 Iridoplegia, 280, 413 Iris, anatomy of, 265 Iris, cysts of, 282 hyperemia of, 271 inflammations of, 271 injuries of, 280 paralysis of, 280 physiology of, 268 prolapse of, 225 tremulans, 286 tumors of, 283 Iris-shadow test, 337 Iritis gummosa, 279 nodosa, 279 papulosa, 275 plastica, 272 purulenta, 272 serosa, 277 simplex, 272 suppurativa, 278 syphilitica, 275, 279 traumatica, 275 tuberculosa, 279 J Jacobson's incision for cataract, 351 Jequirity, 193, 196 K Keratektasia, 261 Keratitis bullosa, 239 dendritica, 237 e lagophthalmo, 239 eczematosa, 231 fascicularis, 231 filamentosa, 238 from pressure, 253 interstitialis diffusa, 243 lymphatica, 231 neuroparalitica, 238 parenchymatosa, 243 circumscripta, 246 phlyctenulosa, 231 punctata profunda, 246 superficialis, 235 scleroticans, 246 scrofulosa, 231 striata, 252 superficialis vasculosa, 232 trachomatosa, 234 traumatica, 248 vasculosa superficialis, 232 Keratocele, 225 Keratoconus, 259 Keratoglobus, 261 Keratomalacia infantum, 240 Keratome, 213, 281 Keratoplasty, 256, 259 INDEX. Keratoscope of Wecker-Masselon, 97 Keratoscopy, 96 Klebs-Leffler bacillus, 195 Kopiopia hysterica, 387 L Lacrimal apparatus, anatomy of, 167 canal, 168 caruncle, 143 fistula, 170, 172 glands, diseases of, 169 passage, diseases of, 170 punctum, 168 sac, diseases of, 172 sound, 176 Lacrimation (see Epiphora) Lagophthalmos, 160 Lamina cribrosa, 122 suprachorioidea, 267 Lashes, diseases of, 149 Laurence’s strabometer, go Lens (crystalline), 331 anatomy of, 331 astigmatism of, 380 capsule of, 331 cataract of, 333 changes of position of, 358 displacement of, 359 embryology of, 332, increase in size of, 337 Lenses, 32 cylindrical, 52, 378 Leukoma adherens, 225 cornez, 254 Level, differences of, 135 Lid, abscess of, 145 anatomy of, 143 cartilage of, 143 coloboma of, 165 diseases of, 143 eczema of, 144 edema of, 147 hemorrhage into, 146 spasm of, 157 Lid edge, diseases of, 149 forceps for, 155 J Ligamentum suspensorium lentis, 333 Light minimum, 53 sense, 53 of the retinal periphery, 63 Lightning, cataract from, 343 Line, visual (see Visual line) Lipoma of conjunctiva, 218 Lithiasis palpebralis, 156, 184 Localization of opacities, 118 of patalyses, 428 Loss of working power in damaged eyes, 423-425 483 Lupus, 166 Luxatio bulbi, 459 lentis, 359 Lymph follicles, 199 M Macropsia, 289 Macula cornez, 254 Maddox rod, 94 Magnet operation of aad, 418 of Hirschberg, 418 Magnification of ophthalmoscopic field in inverted image, 109 in upright image, 107 Malarial fever, blindness from, 389 Malingering (see Simulation) Maritotte's spot, 69 Massage in eczema of conjunctiva, 210 in glaucoma, 404 Masson's disk, 55 Medullated nerve- fibers, 321 Metbomian glands, 143 Membrana pupillaris perseverans, 283, 284 Membrane of Bowman, 220 of Descemet, 221 Meniscus glass, 367 Meridian asymmetry, 48 Meridians, principal, 47 Metamorphopsia, 293, 294, 368 Meter angle, 79 lens, 32 Meyer's (£7,), color test, 59 Microphthalmos, 455 Micropsia, 289 Miotics, 270 in glaucoma, 404 Moll's glands, 143 Morgagnt's cataract, 338 drops, 336 Morphin, 270 Motility of lens, 359 Mouches volantes, 360 Movements of eye, 76 Mueller’s horopter, 73 muscle, 267 Multiple sclerosis, 456 vision, 260 Muscz volitantes, 360 Muscarin, 270 Muscles, action of, 78 Muscular asthenopia, 368, 450 squint, 85 e¢ seg. Musculus ciliaris, 267 Mydriatics, 270 Myelin, 336 Myodesopsia, 360 Myopia, 28, 367 484 Myopia, axis, 373 forms of, 29 measurement of, 31 progressive, 371 school, 373 stationary, 371 Myotomy, 434 Myxoma of optic nerve, 466 Myxosarcoma, 466 N Nagel’s experiment, 432 Naphthalin cataract, 344 Nasal duct, stenosis of, 180 Near point, 35 Nerve, optic, diseases of, 322 Nervous asthenopia, 385 Neurectomia opticociliaris, 420 Neuritis optica, 323, 324 Neurotomia opticociliaris, 420 Nevus (see Telangiectasia) Nictitatio, 157 Night-blindness (see Hemeralopia) shadows (see Hemeralopia) Neurectomy, optico-ciliary, 420 Neuritis descendens, 325 intoxication, 327 myopum, 370 optica, 324 retrobulbar, 326 Neuroglia, 318 Neuron, 302 Neurotomy, optico-ciliary, 420 Nicotin, 270 Nodal point, 23 Nubecula cornez, 254 Nuclear paralysis, 437 sclerosis, 344 Nyctalopia, 326 Nystagmus, 455 from brain disease, 456 from weak sight, 455 of minors, 456 oO Oblique illumination, 98 Cidema (see Edema) “Old-sight”’ (see Presbyopia) Opacitates cornez, 251 corporis vitrei, 360 Opacity in the lens, diagnosis of, 335 Opaque nerve-fibers, 321 Operation of Dreffenbach, 165 of Flarer, 162 of Pagenstecher, 351 INDEX. Operation of Saemisch, 228 Ophthalmometer, 98 Ophthalmoplegia, 434 externa, 434 interna, 434 totalis, 434 Ophthalmoscope, 1a1 of Cocctus, 115 of Helmholtz, 114 of Liebreich, 115 of Zehender, 116 theory of, 101 uses of, 117 Ophthalmoscopic field, 110 in inverted image, IIo in upright image, I12 Ophthalmotonometer, 138 Optic disc, 121 physiological excavation of, 124, 397 nerve, diseases of, 322 anatomy of, 303 atrophy of, 327 inflammation of, 324 neuritis, 324 radiation, 302, 305 tracts, 305 vesicle, primary, 332 Optogram, 321 Optometer, 44 Orbiculus ciliaris, 267 Orbit, abscess of, 460 injuries to, 458 sarcoma of, 467 tumors of, 466 Orthophoria, 92 Osteoma of orbit, 466 Osteoplasty, 467 P Pagenstecher’s operation, 351 salve, 151 Pannus, 240 carnosus, 241 crassus, 241 eczematosus, 242 tenuis, 241 trachomatosus, 242 traumaticus, 242 Panophthalmitis, 288, 296 Papilla nervi optici, 122 Papillary body, 181 Papillitis, 324 Papillo-retinitis, 309, 324 Parallax, 135 Paralysis, nuclear, 437 of accommodation, 288 INDEX. Paralysis of ciliary muscle, 288 of eye muscles, 425 Parasites, 407 Paresis, 288, 426 Pars ciliaris retinas, 267 Pemphigus, 219 Pericorneal injection, 222, 272 Perimeter, 66 Periostitis orbite, 459 Peripheral linear extraction, 349 Petit, canal of, 333 Pflueger’s color tests, 59 Phacomalacia, 339 Phlegmon, 146 Phlyctena pallida, 206 Phlyctenula of conjunctiva, 207 of cornea, 231 pallida, 206 Photometer, 54 Photophobia in iritis, 272 in keratitis, 234 Phthisis bulbi, 226 Physiological excavation, 124, 397 Pigment degeneration, 313 epithelium, 266 Pilocarpin, 270 Pinguecula, 211 Point, far, 30 near, 35 nodal, 23 principal, 22 Polyopia (see also Multiple vision), 260 monocularis, 335 Polypi of conjunctiva, 218 Pop-eye,” 457 ‘Position of election,” 451 Posterior synechia, 230, 273, 287, 405 Presbyopia, 46 Pressure bandage, 227, effect on cornea, 253 Primary deviation, 441 glaucoma, 395 Principal meridians, 47 planes, 22 points, 22 Prisms, 91 refracting angle of, gI uses of, 93, 450, 453 Probe, lacrimal, 176 Processus ciliaris, 267 Progressive amaurosis, 329 Projection of images, 75 Prolapse of iris, 225 of vitreous, 350 Protrusions of the cornea, 257 Pseudo-erysipelas, 146 Pseudo-glioma, 320 Pseudo-isochromatic cards, 58 485 Pterygium, 211 advancing, 212 stationary, 212 Ptosis, 157 Pulsating exophthalmos, 461 Punctum lachrymale, 168 proximum, 35, 41 remotum, 30 Puncture of cornea, 228, 405 Pupil, 265 changes in, 284 closure of, 472 274 contraction of, 266 dilatation of, 266 influence of size of, upon ophthal- moscopic field, 110 Purkinje-Sanson's images, 26, 100, 356 Pyoktanin, 227 Pyorrhea, 188 Q Quinin, blindness from, 389 R Range of accommodation, 41 of fusion, 80 Rays of construction, 21 of direction, 23 Reclination (for cataract), 346 Red blindness, 57 vision after cataract, 358 Reflex from vessels, 124 in fundus, 125 nuclear, 100 of Haab, 270 Refraction, 17 errors of, 362 of lenses, 356 of prisms, 91 ophthalmoscope, 116 Reichert’s membrane, 220 Relation between accommodation and convergence, 81 Relative range of accommodation, 80 of fusion, 82 Retina, anatomy of, 301 detachment of, 315 diseases of, 306 glioma of, 318 hemorrhage from, 307 hyperemia of, 306 inflammations of, 308 injuries of, 320 physiology of, 301 486 Retina, vessels of, 304 Retinitis albuminurica, 308 diabetica, 310 hemorrhagica, 308 leukemica, 310 pigmentosa, 313 syphilitica, 311 Retrobulbar neuritis, 326 Ribbon-like opacities, 253 Rod optometer, 43 Rods and cones, 302 Rupture of eyeball, 414 Ss Saemisch’s operation, 228 Sarcoma of conjunctiva, 218 of choroid, 297 of iris, 283 of orbit, 467 “Scanning speech,” 456 Scheiner’s experiment, 24 Schmidt-Rimpler’s refractometer, 130 School myopia, 373 Sclera, anatomy of, 221 diseases of, 262 protrusions of, 263 tumors of, 265 wounds of, 265 Scleral border, 221 ring, 122 Sclerectasia anterior, 262 posterior, 290, 369 Scleritis, 262 Sclerochoroiditis anterior, 262, 290 posterior, 290, 369 Sclerotomy, 406 Sclerosis of the lens nucleus, 344 Scopalamin, 270 Scotoma, physiological, 69 circumscribed, 294 Seborrhea, 149 fluida, 149 sicca, 149 Secondary contractures, 433 deviation, 441 glaucoma, 400 Seebeck's (Holmgren's) color tests, 58 Senile ectropion, 164 macular changes, 321 Sense of color (see Color sense) Sense of distance, 71 Septic embolism, 312 Serpiginous ulcer, 229 Shadow of iris in diagnosticating cat- aract, 337 Shadow test (see Skiascopy) Shortsightedness (see Myopia) INDEX. Silver, nitrate of, in conjunctivitis, 191, 192 aatahion 387 Sinus cavernosus, 462 thrombosis, 464 Skiascopy, 13! Snellen's suture, 164 Snow blindness, 384 Soft cataract, 339 Sounds, lacrimal, 176 Spasm of ciliary muscle, 289 Spherical aberration, 343, 380 Sphincter pupillee, 266 Spring catarrh, 207 Spud for removing foreign bodies, 250 Squint (see also Strabismus), 70, 83 angle of, 83 convergent, 440 downward, 85 inward, 84 latent, 449 manifest, 84 muscular, 85 e¢ seg. outward, 84 paralytic, 425 upward, 85 Staphyloma, 264 cornez, 257 posticum, 264, 290, 369 sclerz, 264 Stauungspapille, 322 Stellwag's symptom, 464 Stenopaic glasses, 380 slit, 51 Stereoscope, 448 Stiff neck, 427 Strabismus (see also Squint), 83 alternans, 441 concomitans, 89, 440 deorsum vergens, 85 divergens, 449 paralyticus, 85, 425 periodicus, 440 sursum vergens, 85 unilateralis, 441 vision in, 440 Strabometer, 90 Stricture of lacrimal passages, 172 Stricturotomy, 177 Sty, 152 Sublimate eczema, 145 Suction (for cataract), 346 Suppression of retinal images, 75 Suspensory ligament, 333 Suture, Gazllard’s, 162 Snellen’s, 164. Symblepharon, 217 Sympathetic ophthalmia, 418 Synchysis, 362 Synchysis scintillans, 362 Synechia anterior, 230 posterior, 230, 273, 287 totalis, 274 T Tzenia solium, 407 Tapetum cellulosum, 319 Tarsitis, 156 Tarsorrhaphy, 160 Tarsus, diseases of, 154 Tatooing, 255 Tear (see Lacrimal) Teichopsia, 392 Telangiectasia, 167, 467 Tenon's capsule, 447 advancement of, 447 Tenotomy for heterophoria, 454 for paralysis, 440 for strabismus, 445, 452 Tension in glaucoma, 392 measurement of, 137 Tensor choroidez, 267 Test frame, 379 lenses, 32 Thread-worms, 411 Thrombosis, marasmatic, 464 of vena centralis retinz, 313 of vena ophthalmica, 464 septic, 464 Tobacco amblyopia, 327 Tonometer, 139 Torpor retinz, 316 Torticollis, 427 Total posterior synechia, 274 Trachoma, 199 corneal ulcer in, 234 follicles in, 200 Transillumination, 118 Transplantation of ciliary floor, 163 of conjunctiva, 217 of cornea, 256 Traumatic cataract, 339 keratitis, 248 pannus, 242 Trichiasis, 149, 153 Tuberculosis of choroid, 296 of conjunctiva, 206 of iris, 279 of lid, 166 Tumors of conjunctiva, 218 of cornea, 261 of iris, 283 of lid, 165 of orbit, 466 of retina, 318 of sclera, 265 Tunica media, 265 uvea, 265 INDEX. 487 U Ulcer of cornea, 222 of lid-edge, 152 Ulcus cornez, 222 rodens, 230 serpens, 22 Upright image Giveet method), 104 Uremic amaurosis, 389 retinitis, 308 Uvea, 265 Uveal tunic, 265 Vv Vaccination pustule, 152 Vascular network around cornea, 221 Vena centralis retina, 124 Venez ciliares, 268 vorticosz, 268 Venous pulse, 305 Verruce (see Warts) Vertigo in squint, 425 Vision, acuteness of, 17, 33 binocular, 70 indirect, 61 monocular, 365 multiple, 260 principles of, 17 Visual angle, 34 acuity, 33 field, 65, 304 color limits in, 69 line, 83 Visus reticulatus, 295 Vitreous, abscess of (see Panophthal- mitis) anatomy of, 360 central canal of, 269, 360 fluidity of, 362 opacities in, 360 prolapse of (in cataract opera- tion), 350 Vorticose veins, 268 w Warts of choroid, 301 of lid, 166 Weaksightedness, cerebral, 390 Weber's lacrimal sound, 176 Scoop, 349 Wolfberg’s test for color sense, 60 Wool test for color sense, 58 Worms (see Parasites) Wounds of choroid, 300 of conjunctiva, 215 of cornea, 247 488 Wounds of eyeball, 411 of orbit, 458 x Xanthelasma, 167 Xanthoma, 167 Xerosis bacilli, 213 epithelialis, 213 marantica, 240 INDEX. 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No. 6. MATERIA MEDICA, THERAPEUTICS, AND PRESCRIPTION WRITING. Sixth Revised Edition (U.S. P.1890). By SamueL O. L. Porter, M.D., Professor of the Practice of Medicine, College of Physicians and Surgeons, San Francisco, No.7. GYNECOLOGY. A New Book. By Wm. H. WELLS, M.p., Assistant Demon- strator of Obstetrics, Jefferson Medical College, Philadelphia. Illustrated, No, 8. DISEASES OF THE EYE AND REFRACTION. A New Book. Includ- ing Treatment and Surgery. By GreorcGrE M. GouLp, m.D., and W. L. PyLz, m.p. With Formule and Illustrations. No.9. SURGERY, Minor Surgery, and Bandaging. Fifth Edition, Enlarged and Im- proved. By OrviLLe Horwitz, B.s., M.D., Clinical Professor of Genito-Urinary Surgery and Venereal Diseases in Jefferson Medical College; Surgeon to Philadelphia Hospital, etc. With 98 Formule and 71 Illustrations. No. 10. MEDICAL CHEMISTRY. Fourth Edition. 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DISEASES OF CHILDREN. Colored Plate. By Marcus P. HarFiELp, Professor of Diseases of Children, Chicago Medical College. Second Edition, Enlarged. No. 15. GENERAL PATHOLOGY AND MORBID ANATOMY. or Itlustra- tions. By H. NewsBerry HALL, PH.G., M.D., Professor of Pathology and Medical Chem- istry, Chicago Post-Graduate Medical School. Price, each, strongly bound in cloth, .80. Interleaved, for taking Notes, $1.25. Standard Medical Books RECENTLY PUBLISHED. Special Circulars and Sample Pages upon Application. Practice. The Practice of Medicine, with special reference to Treatment. By JAMES Tyson, M.D., Professor of Clinical Medicine in the University of Pennsylvania, etc. With go Illustrations, a number of which are in colors, and two full-page Colored Plates. 8vo. Cloth, $5.50; Leather, $6.50; Half Russia, $7.50 i A Handbook of Materia Medica, Pharmacy, and Therapeu- Therapeutics. tics, including the Action of Medicines, Special Therapeutics, Pharmacology, etc. Including over 600 Prescriptions and Formule. By SAMUEL O. L. POTTER, M.A., M.D., M.R.C.P. (Lond.), Professor of the Principles and Practice of Medicine, College of Physicians and Surgeons, San Francisco; late A. A. Surgeon U.S. Army. Sixth Edition. Revised and Enlarged. goo pages. 8vo. With Thumb Index in each copy. Cloth, $4.50; Leather, $5.50; Half Russia, $6.50 Surgery. A Complete Text-Book of Surgery. By C. W. MANSELL MouLuin, M.A., M.D. (Oxon.), F.R.c.S., Surgeon and Lecturer on Physiology to the London Hospital; formerly Radcliffe Traveling Fellow and Fellow of Pembroke College, Oxford. Third American Edition. Revised and Edited by Joun B. HAMILTON, M.D., LL.D., Professor of the Principles of Surgery, Chicago Polyclinic; Surgeon, formerly Supervising Sur- geon-General, U.S. Marine Hospital Service; Surgeon to Presbyterian Hospital; Consulting Surgeon to St. Joseph’s Hospital and Central Free Dispensary, Chicago, etc. 628 Illustrations, over 200 of which * are Original, and many of which are printed in Colors. 8vo, Cloth, $6.00; Leather, $7.00; Half Russia, $8.00 A Text-Book of Human Anatomy. By Henry Morris, M.D., Anatomy. F.R.C.S. 791 Illustrations (214 of which are colored). Recom- mended in 70 American Medical Schools. 8vo. Cloth, $6.00; Leather, $7.00; Half Russia, $8.00 Diseases of the Eye and Ophthalmoscopy. By Dr. Ophthalmology. EuGEN Ficx, University of Zurich. Authorized ie anele tion by ALBERT B. HALE, M.D., Consulting Ophthalmic Surgeon to the Charity Hospital, Chicago, etc., with a Glossary and 158 Illustrations, many of which are printed in Colors. 8vo. Cloth, $4.50; Leather, $5.50; Half Russia, $6.50 Nervous Manual of Diseases of the Nervous System. A Complete Text- = Book. By WiLLiam R. GOWERS, M.D., F.R.S., Prof. Clinical Diseases. Medicine, University College, London. Physician to National Hos- pital for the Paralyzed and Epileptic. Second Edition. Revised, Enlarged, and in many parts rewritten. With many new Illustra- tions. Two volumes. Octavo. Vou. I. Diseases of the Nerves and Spinal Cord. 8vo. Cloth, $3.00; Leather, $4.00; Half Russia, $5.00 Vot. II. - Diseases of the Brain and Cranial Nerves ; General and Functional Diseases. 8vo. Cloth, $4.00; Leather, #5.00; Half Russia, $6.00 PUBLISHED ANNUALLY FOR 46 YEARS. THE PHYSICIAN’S VISITING LIST. (LINDSAY & BLAKISTON’S.) Special Improved Edition for 1897. In order to improve and simplify this Visiting List we have done away with the two styles hitherto known as the ‘‘ 25 and so Patients plain.’’ We have allowed more space for writing the names, and added to the special memoranda page a column dor the: “Amount”? of the weekly visits and a column for the ‘Ledger Page.’’ To do this with- out increasing the bulk or the price, we have condensed the reading matter in the front of the book and rearranged and simplified the memoranda pages, etc., at the back. The Lists for 75 Patients and roo Patients will also have special memoranda page as above, and hereafter will come in two volumes only, dated January to June, and July to December. While this makes a book better suited to the pocket, the chief advantage is that it does away with the risk of losing the accounts of a whole year should the book be mislaid. The changes and improvements made in 1896 met with such general favor that the sale increased more than ten per cent. over the previous year. CONTENTS. PRELIMINARY MATTER.—Calendar, 1896-1897—Table of Signs, to be used in keeping records—_ The Metric or French Decimal System of Weights and Measures—Table for Converting Apothecaries’ Weights and Measures into Grams—Dose Table, giving the doses of official and unofficial drugs in both the English and Metric Systems—Asphyxia and Apnea—Complete Table for Calculating the Period of Utero-Gestation—Comparison of Thermometers. VISITING LIST.—Ruled and dated pages for 25, 50, 75, and 100 patients per day or week, with blank page opposite each on which is an amount column, column for ledger page, and space for special memoranda, SPECIAL RECORDS for Obstetric Engagements, Deaths, Births, etc., with special pages for Addresses of Patients, Nurses, etc., Accounts Due, Cash Account, and General Memoranda. SIZES AND PRICES. REGULAR EDITION, as Described Above. BOUND IN STRONG LEATHER COVERS, WITH POCKET AND PENCIL. For 25 Patients weekly, with Special Memoranda Page, ..... ...... soe ee). BE OO 50 “ “ “ & ne oo ‘ meg Bo rab ee tee I 25 so. Ol ee eS 7 «2 vols, fin we 2 J ane se te - . 200 75 = 7 . e _ 2 vols. jay te ee : " 7 2:08 Ioo | as Ls a “2 vols. { fay to Bee Ps ee 2 25 PERPETUAL EDITION, without Dates. No. 1. Containing space for over 1300 names, with blank page opposite each Visiting List page, Bound in Red Leather cover, with Pocket and Pencil,. ..-. +--+ - ae ee “PI 25 No. 2. Same as No. 1. Containing space for 2600 names, with blank page opposite, . : ae I 50 MONTHLY EDITION, without Dates. No. x. Bound, Seal leather, without Flap or Pencil, giltedges, - - ss + ee te ee eee 75 No. 2. Bound, Seal leather, with Tucks, Pencil, etc., gilt edges, . . he hes ee * 4 ie toe RG All these prices are net. No discount can be allowed retail purchasers, Circular and sample pages upon application. P. 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