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 http://www.archive.org/details/cu31924031388741 
 
BOUGHT WITH THE INCOME 
 FROM THE 
 
 SAGE ENDOWMENT FUND 
 
 THE GIFT OF 
 
 Hetirg W. Sage 
 
 1891 
 
 A. LSLlX'/. dr/u/aV, 
 
 5474 
 
Cornell University Library 
 
 3 1924 031 388 741 
 olin.anx 
 
The appearance of the interior of the back portion of a healthy eye, 
 sometimes called the " luiidus." 
 
THE EYE AND ITS CARE 
 
 BY 
 
 FRANK ^LLPORT, M.D. 
 
 Minneapolis, Minnesota. 
 
 professor of clinical ophthalmology and otology in the minnesota state 
 
 university; president of the Minnesota state medical society; 
 
 secretary of the ophthalmoloqical section of the 
 
 american medical association, etc., etc. 
 
 PHILADELPHIA 
 
 J. B. LIPPINCOTT COMPANY 
 1896 
 
 T 
 
COPTBIGHT, 1896,' 
 
 BY 
 
 J. B. LiPPlNCOTT COSIPANY. 
 
 Electrotyped and Printed by J. B. LiPPfNcorr Company, Philadelphia, U.S.A. 
 
CHAELES A. OLIVER, A.M., M.D., 
 
 OF PHILADELPHIA, 
 
 THIS LITTLE VOLUME IS MOST CORDIALLY AND 
 
 RESPECTFULLY DEDICATED 
 
 BY 
 
 THE AUTHOR. 
 
6 PREFACE. 
 
 such subjects ; but it is hoped they will 
 remember that these portions are written 
 not for them, but for those requiring ele- 
 mentary and easily comprehended instruc- 
 tion. 
 
 Originality, either as to subject matter or 
 pictorial illustration, is not claimed by the 
 writer. An effort has been made to present 
 the topic in a manner that may be readily 
 understood ; and wherever it has been found 
 necessary to borrow ideas or illustrations, it 
 has been done. 
 
 Trusting that the book will accomplish 
 the purpose for which it was written, the 
 writer begs the kind indulgence of its 
 readers for any manifest shortcomings. 
 
 Frank Allport. 
 
 602 Nicollet Ave., Minneapolis, Minn. 
 
CONTENTS. 
 
 CHAPTER I. PAGE 
 
 Anatomy and Physiology 9 
 
 CHAPTEE II. 
 
 Light, Lenses, Ebfraction, and its Ocular 
 Errors 57 
 
 CHAPTEE III. 
 Test-types, Glasses, etc 94 
 
 CHAPTEE IV. 
 The General Care op the Eye 104 
 
 CHAPTEE V. 
 Eefkaction in Schools 119 
 
THE EYE AND ITS CARE. 
 
 CHAPTBE I. 
 
 ANATOMY AND PHYSIOLOGY. 
 
 The eye is a globular body composed of 
 certain coats, and humors of a more or less 
 fluid consistency. Providence has blessed 
 us with two such organs, which is a fortu- 
 nate provision when their delicacy and ease 
 of irreparable injury are remembered. 
 
 The eye rests in a bowl-shaped socket, 
 which is composed of portions of several 
 bones of the skull, joined together. In the 
 rear of the socket are some openings, one of 
 which, called the optic foramen, serves prin- 
 cipally for the admission of the optic nerve 
 as it passes from the brain to the eye. The 
 socket is lined by certain membranes and 
 other tissues, serving as a soft and yield- 
 
10 
 
 THE EYE AND ITS CARE. 
 
 ing bed in which the eyeball, without 
 impairing its integrity, rests and moves. 
 Among these tissues is found a double mem- 
 brane, originating in the posterior portion of 
 
 Tig. 1. 
 
 Section of the skull showing the orbit or socket in which the eyeball 
 moves : A, optic foramen through which the optic nerve passes. 
 
 the socket. Passing forward, it envelops 
 the eyeball, being loosely attached to it 
 at its circumference. It then doubles on 
 itself, passes backward, and becomes reat- 
 tached near the point of its origin. This 
 
ANATOMY AND PHYSIOLOGY. 11 
 
 membranous sac is called Tenon's or Bon- 
 net's capsule, and forms a concavity in which 
 the eyeball is held in a manner analogous 
 to what is known as a ball-and-socket joint. 
 
 Fig. 2. 
 
 1, piece of orbital bone; 2, external straight muscle, with piece cnt 
 out; 3, optic nerve; 4, internal straight muscle; 5, upper straight 
 muscle; 6, lower straight muscle; 7, upper oblique muscle» attached 
 to ball at 8 : 9, lower oblique muscle ; 10, sclerotic ; 11, cornea ; 12, 
 pulley for tendon of upper oblique. (Gray.) 
 
 The eye is moved in different directions 
 by six muscles. Four of these are known 
 respectively as the superior rectus, which is 
 attached at the upper portion of the globe ; 
 the inferior rectus, which is attached at the 
 lower portion ; and the internal rectus and 
 external rectus, which are attached severally 
 
12 THE EYE AND ITS CARE. 
 
 at the inner and outer portions of the eye- 
 ball. Besides these, there are the superior 
 and inferior oblique muscles, which are at- 
 t9,ched at the outer portion of the eyeball. 
 With the exception of the inferior oblique, 
 they all originate around the optic foramen, 
 at the extreme rear of the orbit, and, pass- 
 ing forward through the tissues of Tenon's 
 capsule, become attached as just described. 
 The inferior oblique muscle originates in 
 the lower inner and anterior portion of 
 the orbit, passes along sideways under the 
 inferior rectus, to become inserted under 
 the tendon of the external rectus, thus par- 
 tially encircling the globe. The superior 
 oblique, after originating near the optic 
 foramen, runs forward and inward, and 
 passes through a little pulley at the upper 
 and inner part of the orbital edge. It 
 then turns outward over the upper portion 
 of the globe, under the superior rectus 
 muscle, and is fastened or inserted at the 
 upper and outer part of the eyeball. 
 
ANATOMV AND PHYSIOLOGY. 13 
 
 These are the muscles which move the 
 eye in almost every conceivable direction. 
 The principal movement obtained by the 
 superior rectus is in an upward direction ; 
 by the inferior rectus, downward; by the 
 internal rectus, inward ; by the external 
 rectus, outward ; while the oblique muscles 
 impart principally oblique or rotary im- 
 pulses and movements to the eyeball. A 
 shortening or contraction of one of these 
 muscles is frequently the cause of cross-eye, 
 or strabismus, as it is technically called. 
 Thus, if the internal rectus muscle is 
 shortened or contracted, the eye turns in, 
 producing a condition familiar to the reader. 
 If the external rectus muscle is shortened, 
 the eye turns out, producing " wall-eye," as 
 it is commonly denominated. These un- 
 fortunate conditions, if not corrected by 
 glasses, are remedied by cutting the con- 
 junctiva or enveloping membrane of the 
 anterior portion of the eyeball, picking up 
 the contracted muscle with a hook, and 
 
 2 
 
14 
 
 THE EYE AND ITS CARE. 
 
 severing it from its attachment, thus en- 
 abling the eye to assume its proper position. 
 
 Pig. 3. 
 
 Shows the operation for " cross-eye" or strabismus. The eyeball Is 
 being steadied by a pair of forceps ; the conjunctiva has been cut, the 
 tendon of the internal rectus muscle drawn out on a hook, and the 
 scissors are just about to sever the tendon. 
 
 The eyeball proper is composed of three 
 coats, each of which performs essential func- 
 tions in its healthy or physiological condi- 
 tion. 
 
 The outer coat of the eye is called the 
 sclerotic, and is hard, tough, and unyielding. 
 It is the skeleton of the visual organ, for 
 
ANATOMY AND PHYSIOLOGY. 15 
 
 without it the eye could not maintain its 
 shape, as it is the only firm membrane con- 
 cerned in its composition. It is white and 
 glistening in appearance, and is indicated 
 
 Pig. 4. 
 
 Vertical section through the eyeball : 1, sclerotic ; 2, choroid ; 3, 
 ciliary muscle ; 4, cornea; 5, iris; 6, aqueous humor ; 7, lens; 8, vitreous 
 humor; 9, retina; 10, optic nerve; 11, ciliary or suspensory ligament; 
 12, anterior chamber ; 13, posterior chambers. 
 
 when reference is made to the " white of the 
 eye." To this coat are attached all the 
 muscles which move the eye, and, in fact, 
 it may be said, with reasonable accuracy, 
 that all of the tissues, membranes, muscles, 
 etc., which serve to operate the ocular func- 
 tions, are attached, either directly or indi- 
 
16 THE EYE AND ITS CARE. 
 
 rectly, to this coat. Veritably it is the frame- 
 work upon which the eye is constructed. It 
 practically surrounds the eyeball on all por- 
 tions of its circumference, and in the rear 
 is continuous with the outer sheath of the 
 optic nerve, as the sheath passes through the 
 optic foramen on its way to the cavity of the 
 brain. Even here it is still continuous with 
 the dura mater, or outer enveloping mem- 
 brane of the brain substance. In front the 
 sclerotic coat passes (with some changes in 
 its structure) into what is known as the 
 cornea, so it will be seen that the entire 
 outer membrane of the eye is in reality 
 simply an extension outward of the dura 
 mater of the brain. When the sclerotic 
 merges into the corneal tissue, it loses those 
 elements in its composition which render it 
 opaque, and in this position becomes trans- 
 parent and colorless. The cornea itself 
 projects from the general contour of the 
 eyeball like a bay-window from a house, or 
 a glass crystal from the face of a watch, 
 
ANATOMY AND PHVSIOLOGV. 17 
 
 which, in reality, it resembles. It is best 
 seen in profile, for when viewed from in 
 front the underlying iris is merely brought 
 in view. It is the "window of the eye" 
 through which one sees, and, as its surface 
 is limited and its function so important, the 
 utmost care must be taken to preserve its 
 brilliancy and transjoarency. As, in order 
 to obtain the best view of objects when look- 
 ing through a window-pane, it is necessary 
 that the glass be of superior quality, flaw- 
 less, and unspotted by dirt, frost, etc., so it 
 is with the cornea : it must be as perfect as 
 possible in order to secure good visual re- 
 sults. Hence it is upon account of damage 
 to the cornea that ocular injuries, inflamma- 
 tions, etc., are fraught with so much danger, 
 for if the corneal membrane is roughened, 
 scarred, or impaired, its usefulness will be 
 correspondingly diminished. Therefore, no 
 ocular trouble is insignificant when its possi- 
 ble effect upon the cornea is considered ; and 
 conditions which in other parts of the body 
 
 b 2* 
 
18 THE EYE AND ITS CARE. 
 
 would be hardly noteworthy, here become of 
 the utmost importance. For instance, take 
 a little scratch or ulcer ; if it is on the hand, 
 face, or elsewhere, it attracts little or no at- 
 tention, but should it be situated on the 
 cornea it may assume the utmost gravity. 
 Especially is this so if such conditions 
 spread, and do not quickly disappear, al- 
 lowing at times the entire membrane to be- 
 come involved. In any case, when healing 
 occurs, a white scar will nearly always indi- 
 cate the seat of disease, and proportionately 
 to its extent, position, and density, impair 
 vision. If such a scar occurs directly over 
 the pupil, central vision will be greatly im- 
 paired. If it be situated upon one side of 
 the membrane, the visual result will not be 
 so disastrous. The rest of the eye may be 
 normal, yet if the integrity of the cornea be 
 impaired, correct vision may be impossible. 
 
 Passing inward from the sclerotic the 
 next coat is the choroid, and in this coat 
 is found a material of an entirely different 
 
ANATOMF AND PHYSIOLOGY. 19 
 
 character. It is dark in color and fragile 
 in consistency. It is composed almost en- 
 tirely of blood-vessels, and consequently 
 performs the physiological function of sup- 
 plying nourishment to many portions of 
 the eye, which are otherwise poorly supplied 
 with material sufficient to maintain life. It 
 does not extend back into the brain cavity, 
 but originates in the extreme rear of the 
 eyeball, at the entrance of the optic nerve. 
 At its point of origin it is circular, extend- 
 ing around the optic nerve. From here 
 it spreads out on all sides and lines the 
 sclerotic, to which it is firmly attached at its 
 anterior and posterior portions. As the 
 choroid approaches the anterior portion of 
 the eyeball, its tissues become folded upon 
 themselves in plaits, spreading circularly 
 forward from the central anterior portion of 
 the interior of the globe, like radii around 
 the sun. These duplications are called the 
 ciliary processes, and as they pass forward 
 they become thicker and more muscular 
 
20 THE EYE AND ITS CARE. 
 
 in nature, until at last they are merged into 
 what is known as the ciliary muscle, or the 
 muscle of accommodation, whose physiologi- 
 cal function will be referred to in describing 
 the crystalline lens. The ciliary processes 
 and ciliary muscle together are called the 
 ciliary body, but, in reality, they are all a 
 mere continuation of the choroid. At the 
 extreme anterior portion of the ciliary body, 
 its tissues become thin, change somewhat in 
 character, drop down into view, and are 
 then known as the iris. The three parts, 
 the choroid proper, the ciliary body, and 
 the iris, are sometimes classified under the 
 general name of the uveal tract. 
 
 It is the iris which gives color to the eye 
 and largely imparts expression to the face. 
 Some people have blue, others brown eyes, 
 etc., circumstances which are due to the 
 amount of coloring that is imparted to the 
 iritic tissues. These differing shades are 
 usually consistent with the general color 
 tendency of the individual ; as, for instance, 
 
ANATOMY AND PHYSIOLOGY. 21 
 
 blondes generally have blue, and brunettes, 
 brown or black eyes. The iris of a young 
 Caucasian infant is always blue. The iris of 
 an albino possesses little or no coloring 
 matter, and hence forms but a meagre barrier 
 to the free inspection of the interior of the 
 globe. Owing to the lack of color in the eye 
 of an albino, and the consequent easy ad- 
 mission of light, not only through the pupil, 
 but through the almost transparent iris itself, 
 together with the fact that the choroid is 
 almost devoid of color (thereby occasioning 
 great confusion of vision) , the sight of these pe- 
 culiar " pink-eyed" individuals is necessarily 
 defective, and, not being provided with the 
 usual defence against excesaes of illumination, 
 their eyes are exceedingly sensitive to light. 
 
 The centre of the iris is pierced by a 
 round opening called the pupil, which is 
 enlarged and contracted intuitively, by mus- 
 cular tissues contained in the meshes of the 
 iris. If an individual enters a dark room, 
 the desire for more light is instinctive ; 
 
22 THE EYE AND ITS CARE. 
 
 consequently, the pupil becomes widely ex- 
 panded in order to enhance intraocular illu- 
 mination. If, on the contrary, the sun or 
 other bright light be faced, the muscular 
 fibres produce pupillary contraction, thus 
 excluding detrimental and annoying rays of 
 light. This is a physiological function 
 which is accomplished without volition, and 
 is a beautiful illustration of the marvellous 
 action of the different portions of the body. 
 
 The pupil is simply a hole in the iris, that 
 is similar to the perforation made by a con- 
 ductor's punch in a piece of cardboard, and 
 not, as many people believe, upon account 
 of its darkness, something that is substantial. 
 It appears black because of the lack of 
 intra-ocular illumination, just as the open 
 door- way to a dark closet is black for essen- 
 tially the same reason. If in the latter case 
 daylight be allowed to pass through any por- 
 tion of the closet walls or if we stand upon 
 the threshold of the closet with a lighted 
 lamp in our hand, the black area of the 
 
ANATOMY AND PHYSIOLOOV. 
 
 23 
 
 door-way is lost and the contents of the closet 
 are revealed. 
 
 FiQ. 5. 
 
 Shows the interchange of light rays between the eye of an observer and 
 of the observed. 
 
 An interchange of light rays between the 
 eye of an observer and the object observed 
 is essential to perception, this statement 
 presupposing illumination of the object. 
 Surface objects are therefore easily perceived, 
 while those that are contained in unillu- 
 mined spaces are invisible ; consequently, the 
 pupil of the observed eye appears black, and 
 the interior of the globe is invisible, through 
 lack of intra-ocular illumination occurring 
 in the track of the observer's eye, this being 
 impossible unless the observing eye is 
 located directly in such illumined track. 
 To illustrate : if a lamp is held between the 
 eye of the observer and the observed eye, it 
 
24 THE EYE AND ITS CARE. 
 
 will prevent an interchange of light rays 
 between the two organs. Again, if the lamp 
 is held back of the observer's head, the 
 illumination proceeding therefrom will not 
 reach the observed eye. Therefore, we can- 
 not view the interior of another person's eye 
 because we cannot utilize ordinary intra- 
 ocular illumination. 
 
 The interior of the living eye was as 
 a closed book until the genius of von 
 Holmholtz inspired the practical conception 
 of the ophthalmoscope. By the use of this 
 instrument, the greater portion of the inside 
 of the eye can be inspected with as much 
 closeness and accuracy as the outside, and 
 the intraocular lesions of many diseases 
 that had heretofore been misunderstood were 
 disclosed by this search-light of ophthal- 
 mology. We cannot see into the interior of 
 the eye without this instrument, because we 
 are always in our own light, as it were, but 
 the principle upon which the ophthalmoscope 
 is constructed obviates this difficulty. 
 
ANATOMY AND PHYSIOLOGY. 
 
 25 
 
 Pig. 6. 
 
 The ophthalmoscope is simply a little 
 mirror with a hole situated in its centre. 
 The observer and patient 
 sit facing one another in 
 a dark room, with a strong 
 steady light placed at the 
 side and a little in the 
 rear of the latter's head. 
 The observer takes the 
 instrument, places it in 
 front of his eye, with the 
 mirror toward the light 
 
 Fia. 7. 
 
 Shows the back of the oph- 
 thalmoscope. 
 
 Shows the perforated circular 
 concave mirror in the front of 
 the ophthalmoscope. 
 
 and the patient, and looks through the cen- 
 tral perforation. If this be done properly, 
 
26 THE EYE AND ITS CARE. 
 
 the pupil, whicli but a moment before was 
 black, becomes red, as tbe red reflex of the 
 choroid, shining through the nearly trans- 
 parent retina, is brought to view. From this 
 simple beginning, the complexities and beau- 
 ties of a thorough ophthalmoscopic examina- 
 tion can be obtained by patience and skill. 
 To suit the exigencies of each case, there is a 
 system of changeable lenses situated behind 
 the mirror, by means of which the interior 
 of the eye may be made more plainly visible, 
 and the optic nerve, choroid, vessels, veins, 
 etc., all as accurately observed as if they 
 were placed in the palm of the open hand. 
 The explanation for this is simple and 
 obvious. Rays of light proceed from the 
 lamp to the mirror, which is held in front 
 of the observer's eye, and through which 
 he looks, by means of the central perfora- 
 tion. The light rays are then transmitted 
 from the mirror to the observed eye, and, 
 after passing through the pupil, strike the 
 retina, from which they rebound and pro- 
 
ANATOMY AND PHYSIOLOGY. 
 
 27 
 
 ceed back to the mirror, through the perfo- 
 ration and through the observer's pupil to 
 his retina, thus inducing visual perception. 
 It will therefore be noticed that, inasmuch 
 as the eyes of the observer and the observed 
 are mutually located in the track of the 
 unobstructed light rays, rendered clear by 
 means of the lamp and the location of the 
 
 .Fig. 8. 
 
 Shows how the interior of the eye may be seen through the flame of a 
 candle. (Loring.) 
 
 observer's eye behind the perforated mirror, 
 there is no reason why the intra-ocular 
 structure of the observed eye should not be 
 visible to the eye of the observer. The same 
 
28 
 
 THE EVE AND ITS CARE. 
 
 thing would be accomplished if the eye of 
 the observer was located directly in a flame, 
 or behind a hollow tube immersed in a flame, 
 held between the observer and the observed. 
 
 PlQ. 10. 
 
 Relative position of patient and observer during the so-called indirect 
 method of ophthalmoscopic examination. 
 
 The examination of the interior of the 
 eye is much facilitated by placing a few 
 drops of belladonna or of its active principle, 
 atropine, upon the conjunctival sac. The 
 
ANATOMY AND PHTSIOLOGV. 29 
 
 drag paralyzes the muscular fibres which 
 contract the pupil, thereby producing a 
 pupillary dilatation, and a consequent en- 
 largement of the opening through which the 
 examination is made. 
 
 The retina is the third and innermost coat 
 of the eye, and in importance yields pre- 
 cedence to neither of the other two coats. 
 It is the perceptive coat, without which 
 nothing could be seen. In reality it is an 
 expansion of the optic nerve, by means of 
 which impressions are transmitted to the 
 brain. It is a veritable continuation of 
 brain substance into the eyeball, and, as 
 the sclerotic coat is a prolongation of the 
 dura mater, so the retina takes its origin in 
 the brain. It extends forward as the optic 
 nerve proper (enclosed in an enveloping 
 sheath), passes through the optic foramen, 
 and, after entering the eye, is spread out 
 in a fan-like fashion, lining the interior of 
 the globe, until it becomes lost in the neigh- 
 borhood of the ciliary body. 
 
 3* 
 
30 TSE EYE AND ITS CARE. 
 
 In order that the retina may fulfil its 
 destiny, a thorough integrity of its tissues is 
 indispensable. If any portion of its structure 
 (within range of vision) be impaired, sight 
 becomes correspondingly deficient. The 
 retina corresponds to the paper on the walls 
 of a room, and, like wall-paper, it sometimes 
 becomes loosened from its underlying attach- 
 ment and forms a kind of blister. This is 
 called detachment of the retina, and is a 
 disease that is incident to many cases of 
 extreme myopia, producing practical blind- 
 ness wherever such detachments occur. 
 There are many other retinal diseases, which 
 it is not the province of this book to enume- 
 rate, that impair the integrity of the retina 
 and that are accompanied by a greater or 
 less loss of vision. Such diseases may occur 
 in circumscribed " spots," giving rise to cor- 
 responding " blind areas" before the eye, or 
 may involve the entire membrane, in which 
 event a general defect of vision follows. 
 
 The retina corresponds to the delicate film 
 
AXATOMl' ASD PHYSIOLOGY. 31 
 
 whicli receives the impression of an object 
 and allows it to become stamped upon its 
 surface in a photographer's apparatus. The 
 entire eye, in fact, closely resembles a camera, 
 and, like the camera, is intended to "take 
 pictures." There is the sclerotic, correspond- 
 ing to the box or shell of the apparatus, 
 forming a firm and substantial framework ; 
 the choroid, forming a background, like the 
 black lining to the camera, and absorbing 
 any excessive light, which, by reflection and 
 diffusion, would prevent accurate vision ; the 
 retina, corresponding to the film of the 
 camera, upon which the impression is re- 
 tained ; the pupil, corresponding to the open- 
 ing in the front of the camera, through 
 which the aerial impression of the object 
 passes ; and there are the lens and the aque- 
 ous and vitreous humors, each and all corre- 
 sponding to similar refracting media in the 
 box of the photographer. Striking com- 
 parison ; wonderful similarity ; undoubtedly 
 the art of photography was conceived from 
 
32 THE EYE AND ITS CARE. 
 
 that most marvellous camera of nature, the 
 physiological eye ! 
 
 The retina, however, is dissimilar to the 
 camera's film in one important particular, 
 — that is, it is not limited to one clear im- 
 pression. Its capacity is, in a sense, infinite. 
 Whenever an object is looked at, a picture 
 is made on the retina, which is dissipated in 
 the fractional part of a second, to make room 
 for another. The lightning-like rapidity of 
 this phenomenon is almost incredible, and 
 yet it is known that it exists. At times, 
 however, these impressions are not so quickly 
 removed, as the eye, although turned away 
 from an object upon which it has been fixed, 
 may occasionally retain the impression. For 
 instance, if one looks intently at an incan- 
 descent light and the gaze be turned else- 
 where, the white loop of light may still be 
 seen. This phenomenon is supposed to be 
 the explanation of Macbeth's remark when 
 he said, " Is this a dagger which I see 
 before me?" As may be remembered, he 
 
ANATOMY AND PHYSIOLOGV. 33 
 
 had been standing, holding the weapon in 
 his hand, with his gaze fixed intently upon 
 it, when suddenly he lifted his eyes and 
 thought he saw a dagger floating in the air. 
 Undoubtedly this was meant by the great 
 writer to represent an unabsorbed retinal 
 impression. 
 
 In the fertile brain of a French novelist, 
 some years ago, was developed the theory 
 that the picture of a murderer may be found 
 upon his victim's retina, — and, in view of 
 the wonderful progress in other branches of 
 knowledge, it may not be impossible that 
 ante-mortem retinal impressions may some 
 day play an important part in the detection, 
 conviction, and punishment of criminals. 
 
 The most sensitive part of the retina, — 
 the point admitting of the most perfect 
 vision, — is a spot that is situated directly in 
 the axis of vision. It is called the "yellow 
 spot," because here, after death, the retina 
 assumes a yellowish tinge. This is the sj)ot 
 to which the eye naturally seeks to direct 
 
34 
 
 THE EYE AND ITS CARE. 
 
 rays as they enter the globe, and unless suc- 
 cess in this endeavor be obtained, perfect 
 vision is impossible. Consequently, the eye 
 continually moves from one position to 
 another, seeking to focus the rays that pro- 
 
 FlG. 11. 
 
 Shows how single vision is produced by the proper and simultaneous 
 use of both " yellow spots." 
 
 ceed from objects, not only on the retina, 
 but, still better, on the yellow spot. How- 
 ever, to obtain normal binocular vision, it is 
 necessary to focus rays simultaneously upon 
 both yellow spots. The accurate focussing 
 
anAtomv and physiology. 
 
 35 
 
 must be accomplished in both eyes at one 
 and the same time. 
 
 In this way binocular vision, or vision 
 with both eyes, is obtained, — in contra-dis- 
 
 Pio. 12. 
 
 Shows how double vision is produced when the right eye is turned 
 in or converged, and the image emanating from the right "yellow 
 spot" is thrown off to one side. 
 
 tinction to monocular vision, or vision with 
 only one eye, where the other is blinded or 
 obscured. The reason that binocular vision 
 
36 THE EYE AND ITS CARE. 
 
 is much, better and more satisfactory than 
 monocular is that more sides of an object 
 are seen, and the impressions become more 
 comprehensive. 
 
 It may be asked, inasmuch as both eyes 
 receive an impression of an object, why are 
 not two images seen instead of one ? In 
 fact there are, but when these two impres- 
 sions are exactly focussed upon the yellow 
 spots, they become merged into one ; that is, 
 if the object is not held so near as to render 
 it impossible for the eyes to bring the two 
 foci on the two yellow spots at the same 
 time. If with both eyes one looks at his 
 finger at a distance of two or three feet, and 
 then gradually brings it toward his face, he 
 will, at a certain point, find it impossible to 
 longer merge the two images into one : he 
 will see two fingers. The point at which 
 two fingers became visible is the place at 
 which it became no longer possible to con- 
 verge the eyes sufficiently to focus the image 
 of the finger upon both of the yellow spots 
 
ANATOMV AND PHYSIOLOGY. 37 
 
 at one and the same time. When double 
 vision is obtained in this or any other man- 
 ner, it is called diplopia. Owing to insuf- 
 ficient power of certain of the ocular muscles, 
 many people are naturally diplopic. They 
 overcome this tendency, however, and obtain 
 binocular vision by great taxation on the 
 part of the weakened muscles. This in- 
 creased action produces much pain and dis- 
 comfort, and sometimes requires great skill 
 to overcome, either by an operation upon 
 the muscles, by the fitting of glasses, or by 
 other treatment. 
 
 It is generally supposed that in these 
 phenomena are to be found the causes of 
 " cross-eye" or strabismus. In such cases 
 there is a tendency to diplopia or double 
 vision, with a perpetual effort on the part of 
 nature to merge the two images into one, and 
 produce binocular vision. The task becomes 
 so difficult and constant, that, as a result, the 
 eyes soon give up the effort,' and one eye 
 turns aside, and thus becomes " crossed." 
 
 4 
 
38 THE EYE AND ITS CARE. 
 
 There are three humors or fluids of the 
 eye, — viz., the aqueous, the crystalline lens, 
 and the vitreous. By some anatomists the 
 crystalline lens, owing to its hardness, is not 
 called a humor, but for purposes of conven- 
 ience this classification will be adopted. 
 
 The aqueous humor is situated in the 
 anterior part of the eye, occupying the space 
 between the cornea and the crystalline lens. 
 The iris drops into the fluid like a curtain, 
 and divides the space into two portions 
 which are called the anterior and posterior 
 chambers. The former is situated between 
 the cornea and the iris. The latter is located 
 between the iris and the lens. In reality 
 they are one chamber with a free interchange 
 of fluid through the pupillary space between 
 the two portions. The aqueous humor, as 
 its name implies, is of watery consistency, 
 possessing the fortunate ability, after being 
 partially or wholly lost, of becoming repro- 
 duced with great rapidity. The importance 
 of this phenomenon can be realized when the 
 
ANATOMY AND PHYSIOLOGY. 39 
 
 delicacy of the cornea is remembered and 
 how easily this membrane is ruptured. 
 After a rupture nothing can prevent the 
 escape of the aqueous humor through the 
 corneal opening. If the humor did not be- 
 come resupplied, the usefulness of the eye 
 would be lost, through a joining together of 
 the anatomical parts of the anterior portion 
 of the globe, by adhesive inflammation. It 
 must also be remembered that many of the 
 most important operations on the eye involve 
 a loss of aqueous humor during their per- 
 formance, as, for instance, in the operation 
 for the removal of a cataract, which by some 
 people is thought to be an opacity of the 
 cornea, instead of what it really is, an opacity 
 of the crystalline lens. The removal of a 
 cataract simply consists in removing the lens, 
 and not in scraping away the opacities or 
 incrustations that are sometimes observed on 
 the cornea. 
 
 To accomplish this result, it becomes 
 necessary to cut into the eyeball by way of 
 
40 THE EYE AND ITS CARE. 
 
 the cornea and the anterior chamber, and 
 
 Fig. 13. 
 
 Shows an operation for cataract The knife is seen passing through the 
 anterior chamber. 
 
 then to remove the lens, in order to do 
 away with this obstruction to vision, which 
 
 Fig. 14. 
 
 Shows a later step in the operation for cataract. The opaque lens Is 
 just being expelled. 
 
 procedure involves a complete loss of aque- 
 
ANATOMY AND PHTSIOLOGY. 41 
 
 ous humor. This loss, however, as just said, 
 fortunately is rej)roduced as soon as the cor- 
 neal wound heals, which occurs in about 
 thirty-six or forty-eight hours. To a lay- 
 man the removal of a lens may appear 
 equivalent to the destruction of sight, but, 
 if the other portions of the eye are in 
 healthy condition, good vision may be ob- 
 tained by wearing in a spectacle frame a 
 strong convex glass of a focussing power 
 closely approximating that of the removed 
 convex crystalline lens. 
 
 Just back of the aqueous humor is situated 
 the second humor of the eye, viz., the crystal- 
 line lens, which is enclosed in a transparent 
 and elastic capsule or envelope. The lens in 
 its capsule is suspended at all portions of its 
 circumference by a ligament that is called 
 the ciliary or suspensory ligament. The 
 ligament itself originates in the meshes of 
 the ciliary body, and is firmly inserted at 
 the circumferential edge of the lens capsule. 
 The posterior portion of the lens is lodged 
 
 4* 
 
42 THE ETE AND ITS CARE. 
 
 in a cup-shaped concavity in the anterior 
 portion of the vitreous humor. The lens is 
 a semi-solid double-convex body, shaped like 
 a magnifying glass, capable of contraction 
 and expansion by the action of the ciliary 
 muscle and ligament. The ciliary muscle is 
 sometimes called the muscle of accommoda- 
 tion, from its power of accommodating the 
 eye to all distances and dimensions of ob- 
 jects. Were it not for this power, the eye 
 would be like any other unvarying optical 
 apparatus, capable of clear impressions at 
 only exceedingly circumscribed limits. Take, 
 for instance, a powerful magnifying lens of 
 (say) three-inch focus; place it before the 
 eye, and any one with a knowledge of optics 
 will know that the object at which gaze is 
 fastened must be brought up to just three 
 inches from the lens, in order to produce a 
 focus. If the lens is moved farther away, or 
 if it is brought closer than three inches, a 
 blurred image will be obtained. Or, if the 
 same lens be taken and placed between the 
 
ANATOMY AND PHYSIOLOGY. 43 
 
 sun and a piece of paper, it will have to be 
 situated just three inches away from the 
 paper, in order to focus the rays of light 
 which pass through it. Imagine an opera- 
 glass, a microscope, or a telescope with an 
 unvarying focus or, in other words, without 
 any screw or other device by which the in- 
 strument can be set for differing distances 
 of objects : their uses would be very cir- 
 cumscribed ; for, as just hinted, it is neces- 
 sary, in order that they may be useful, that 
 they possess mechanism and adjustments by 
 which objects of different sizes and dis- 
 tances can be focussed and clearly seen. So 
 it is with the eye, which would be com- 
 paratively useless if it possessed the power 
 of focussing only at one distance, and could 
 not be accommodated or focussed instan- 
 taneously upon any object at which the gaze 
 is fastened. What the little adjusting screw 
 is to the opera-glass, the microscope, and the 
 telescope, the ciliary muscle and ligament 
 are to the eye. If the individual wishes to 
 
44 
 
 THE EYE AND ITS CARE. 
 
 look at a small or near object, the ciliary- 
 muscle, or muscle of accommodation, con- 
 tracts, Ayhich allows the ciliary ligament, con- 
 necting the ciliary muscle and the lenticular 
 capsule, to become slack, which, in its turn, 
 permits the lens fibres to give way to their 
 elasticity, thereby forcing the lens into a state 
 of increased convexity. 
 
 Fig. 15. 
 
 Shows the process of acconmiodation. In the left side of the picture 
 the lens is in a normal condition, in the right side it has been forced 
 into a condition of abnonnal convexity by the action of the ciliary 
 muscle. 
 
 Thus, the power of the lens is increased, 
 and small and near objects become distinctly 
 visible. It is like compressing the sides of 
 a rubber ball, which resumes its most con- 
 vex and normal position when such pressure 
 is removed. By this delicate adjustment, 
 
ANATOMY AND PHYSIOLOGY. 45 
 
 whicli is partly voluntary and partly in- 
 voluntary, the eye becomes exceedingly use- 
 ful and capable of wide and accurate func- 
 tions, which are performed more quickly 
 than the rapidity of thought. This can be 
 readily understood when it is remembered 
 that the focus of the eye changes every time 
 that it looks from one object to another, 
 and we all know with what rapidity this is 
 accomplished every moment of our lives. 
 Truly the " eye is a wonderful structure," 
 and when it is analyzed in all of its delicate 
 and exact complexities, we are inspired to 
 say that " it passeth human understanding," 
 and that it can hardly take its origin in 
 accident or evolution. 
 
 Just back of the crystalline lens is located 
 a large globular body, which occupies about 
 two-thirds of the contents of the eyeball ; 
 this is called the vitreous humor. It is of 
 about the consistency of very thin jelly, and 
 is enclosed in a delicate enveloj)e, called the 
 hyaline membrane. When once it is lost by 
 
46 THE EYE AND ITS CARE. 
 
 rupture of the enveloping coats of the eye, 
 it is never re-formed ; this being the acci- 
 dent which occurs when " the eye runs out," 
 as it is graphically described by the laity. 
 
 It is the vitreous which is largely respon- 
 sible for the form that is maintained by the 
 eye, and without it the globe would collapse 
 into a shapeless mass. In addition, by its 
 inward pressure, it keeps the retina and 
 choroid in position, and thus serves to main- 
 tain the proper relation and location of the 
 other inner structures of the eye. 
 
 It is almost unnecessary to state that the 
 cornea and humors of the eye must be main- 
 tained in a condition of absolute transpar- 
 ency, in order to obtain clear vision. Any 
 deviation from this rule will be followed by 
 a corresponding deterioration of sight; es- 
 pecially is this so if such deviation exist 
 directly in the axis of vision. 
 
 The eyebrows are composed of thickened 
 tissue, covered by coarse short hair. They 
 serve the useful purpose of protecting the 
 
ANATOMV AND PHYSIOLOGY. 47 
 
 eye from perspiration as it trickles down the 
 forehead, — acting as a roof to a house, as it 
 were, in shedding moisture. They also 
 serve to impart expression and beauty to 
 the face. This can be well understood when 
 it is considered what varying emotions may 
 be expressed by raising and lowering them, 
 or bringing them together, as during the act 
 of frowning. 
 
 The eyelids are divided into the upper 
 and the lower. The opening between them 
 through which the eye appears is called the 
 palpebral fissure. Most eyes are about the 
 same size, but they appear larger or smaller 
 in accordance with the size of the palpebral 
 fissure. Some think that their eyes are 
 shrinking away, when, in reality, the open- 
 ing between the lids, by reason of some 
 weakness or disease, is smaller than normal, 
 thus presenting the appearance of a dimin- 
 ished size of the eyeball. At each end of 
 this elliptical aperture, there is an angle 
 which is called, respectively, the internal 
 
48 THE EYE AND ITS CARE. 
 
 cantlius and the external canthus ; the for- 
 mer being towards the nose, and the latter 
 toward the temple. 
 
 The lids move over the eyeball and tend 
 to protect it from injury. Such movements 
 are performed, however, almost exclusively 
 by the upper lid, as the lower one remains 
 practically motionless. The edges of the 
 lids are bordered by a fringe of hairs, called 
 the eyelashes. These curve in a manner 
 that tends to best subserve the purposes of 
 usefulness and beauty. In a measure they 
 act to protect the eye from the invasion of 
 foreign bodies, such as sand, dust, cinders, 
 perspiration, etc. Their loss, which some- 
 times occurs, gives the face a peculiarly 
 barren and unsightly appearance. 
 
 Sometimes the eyelashes become misdi- 
 rected in their growth. They turn inward 
 and scrape the eyeball as the lid moves over 
 its surface. This process produces much 
 pain and discomfort, with consequent dis- 
 ease. The condition is commonly known 
 
ANATOMY AND PHYSIOLOGY. 49 
 
 as " wild hairs," — the lashes being pulled 
 out from time to time, as they irritate the 
 eyeball. It may be a relief to those who 
 are thus afflicted to know that the disease 
 can be cured by a suitable operation. 
 
 The upper eyelid hangs from the bony or 
 orbital ridge over which the eyebrow is in- 
 serted. The outer covering is composed of 
 skin, which is continuous with the integu- 
 ment of the body, and which ends at the 
 edge of the lid where the lashes grow. The 
 inner lining of the lid consists of mucous 
 membrane and is known as the conjunc- 
 tiva. It is thin and almost colorless, except 
 when reddened by inflammation. It extends 
 from the edge of the lid to its extreme inner 
 surface, whence it is reflected on to the eye- 
 ball. Here it rests over the sclerotic, and 
 becomes attached around the circumference 
 of the cornea. The conjunctival mucous 
 membrane is the seat of many of the ordi- 
 nary inflammations of the eye, that are so 
 familiar to the laity, and which range in 
 
50 THE EYE AND ITS CARE. 
 
 severity from a mere hypersemia, or conges- 
 tion, to what is known as " chronic granu- 
 lated lids." When reference is made to what 
 is commonly designated as a " sore eye," it is 
 usually an inflammation of this membrane 
 that is meant. The conjunctiva is con- 
 tinuous with the mucous membrane of the 
 tear-passages which run into the nose. It 
 is, therefore, frequently inflamed during 
 the course of what is known as a " cold in 
 the head." During an attack of jaundice, 
 it is sometimes seen to be yellow, this being 
 dependent upon a deposit of bile pigment in 
 its tissues. 
 
 The conjunctiva is the principal lodging 
 place of the various foreign bodies, such as 
 dust, cinders, etc., that so frequently get into 
 the eye and cause irritation. Some of these 
 become embedded in the cornea, and have 
 to be forcibly removed. The majority, how- 
 ever, are drifted along in the current of 
 tears, as they flow from the external to the 
 internal canthus, and there escape by means 
 
ANATOMF AND PHYSIOLOOr. 
 
 51 
 
 of washing the eye, or other more or less 
 natural processes. Occasionally the intruder 
 remains fastened in the conjunctiva, where, 
 as a rule, it will be found, after everting the 
 lid, midway between the internal and the 
 external canthus, just over the face of the 
 
 Fig. 16. 
 
 Exhibits the method of everting the upper lid. 
 
 tarsal cartilage. Eversion of the upper lid 
 is performed as follows. The patient is 
 asked to look down. The lashes of the 
 upper lid are then grasped and pulled 
 down. A pencil tip is placed between the 
 lashes and eyebrows and a downward press- 
 ure made upon it. At the same time the 
 Jid is to be raised by means of the lashes. 
 
52 
 
 THE EYE AND ITS CARE. 
 
 These done properly, eversion occurs, when 
 the foreign body may be seen and removed 
 by a handkerchief, match, etc. 
 
 Fig. 17. 
 
 Shows the upper hd everted , a shows where foreign bodies can usually 
 be located. 
 
 The inside surface of the upper lid is 
 made up principally of a thin piece of 
 cartilage lying underneath the conjunctiva. 
 This is called the tarsal cartilage, and serves 
 to keep the lid in shape. In the lid itself 
 there is a ligament which originates at the 
 bony ridge of the brow and is inserted 
 in the tarsal cartilage, thus limiting the 
 
ANATOMV AND PHYSIOLOGY. 53 
 
 extent to which the lid may drop. There is 
 also a muscle called the levator palpebrarum, 
 which originates near the optic foramen in 
 the back part of the orbital cavity, and passes 
 forward to be inserted into the cartilage; 
 this muscle performs the function of raising 
 the lid. There is another muscle, called the 
 orbicularis palpebrarum. This muscle pos- 
 sesses circular fibres, and extends like an 
 oblong wheel around the eye, under the skin 
 of both the upper and the lower lids. It 
 serves to close the lids, very much as a string 
 or cord closes the opening in an old-fashioned 
 pouch-purse. In addition to these structures, 
 there are certain glands situated inside of the 
 lid which are called the Meibomian glands. 
 These empty themselves along the border of 
 the lid, near the lashes. They are intended 
 to lubricate the lid margins, and at the same 
 time prevent a continual overflow of tears, 
 by interposing a greasy edge, which acts, 
 except in cases of extreme secretion, such as 
 weeping, etc., in a manner that is sufiicient 
 
 5* 
 
54 THE EYE AND ITS CARE. 
 
 to retain any moisture within the palpebral 
 fissure. 
 
 The lower lid resembles the upper in all 
 essential particulars. The tarsal cartilage, 
 however, is much smaller and of different 
 shape. The muscle corresponding to the 
 levator is much reduced in size, having little 
 or no function to perform. 
 
 The lachrymal apparatus constitutes that 
 series of anatomical elements which manu- 
 facture the tears and drain them into the 
 nose. Among other things, it consists of a 
 gland, known as the lachrymal gland, situ- 
 ated in the upper and outer part of the orbit, 
 and which, as a rule, produces the tears in 
 ordinary quantities. Under the influence of 
 excessive emotion, foreign bodies, etc., these 
 are secreted in large quantities. By means 
 of little ducts which emerge from the side of 
 the gland, the tears are conducted from the 
 gland and pass over the surface of the eye, 
 thus serving to keep it constantly moistened, 
 and allowing the lids to move without irrita- 
 
AXATOMr AND PHYSIOLOGY. 65 
 
 tion over its delicate coverings. In this way 
 the tears flow from the external to the in- 
 ternal canthus, and are there drained into 
 what are called the puncta ; these consisting 
 
 Fio. 18. 
 
 Represents the lachrymal apparatus. The skin of the lids has been 
 removed. 1 and 2, upper and lower lids; 3, 3, lachrymal points; 4, 
 lachrymal sac; 5, 5, lachrymal canals; 6, palpebral fissure; 7, nasal 
 duct ; 8, lachrymal gland ; 9, 9, lachrymal ducts. 
 
 of two little holes that are situated at the 
 apex of a slight elevation, on both upper and 
 lower lid, at the inner angle of the eye. 
 These orifices or openings lead into two 
 canals, one of which is intended for the 
 
56 THE EYE AND ITS CARE. 
 
 upper and the other for the lower lid. As 
 they pass in the direction of the nose they 
 converge toward each other, and empty into 
 a space at the upper part of the nose, which 
 is called the lachrymal sac. This sac, in its 
 turn, merges into the nasal duct. The whole 
 secretory and drainage system is lined with 
 mucous membrane. Thus the tears, from 
 their origin to their destination, pursue the 
 following course : from the lachrymal gland 
 to the lachrymal ducts, to the surface of the 
 eye, to the puncta, to the canaliculi, or lach- 
 rymal canals, to the lachrymal sac, and to 
 the nasal duct. 
 
CHAPTEE II. 
 
 LIGHT, LENSES, REFRACTION, AND ITS OCULAR ERRORS. 
 
 A RAY of light travels in waves or undu- 
 lations, at the rate of about one hundred 
 and ninety-two thousand miles in a second. 
 Were no obstructions presented, it would 
 proceed indefinitely into space. Such ob- 
 structions are either transparent, reflective, 
 or opaque. At present only the first of 
 these will be considered. 
 
 Transparent obstructions to light rays are 
 either of similar, ^greater, or lesser density 
 to the media from which such rays come. 
 If the obstruction is of similar density, the 
 waves of light, called rays, pass through the 
 presenting substances in a straight line, or 
 rather the undulations of light are not bent 
 from their course or changed in their size. 
 
 If the presenting substance is of greater 
 density than the medium from which the 
 
 57 
 
58 THE EYE AND ITS CARE. 
 
 light comes, the forcing of the rays through 
 the obstruction is labored and slower, and 
 hence the waves become coarser and more 
 pronounced. (See Fig. 19, first obstruc- 
 
 FiG. 19. 
 
 Illustrates the passage of a ray of light through media of different 
 densities. (Oliver.) 
 
 tion.) If the presenting substance is of 
 lesser density than the medium from which 
 the light comes, the rays proceed through 
 the obstruction with increasing facility and 
 speed, and hence the waves become more 
 delicate and less pronounced. (See Fig. 19, 
 second obstruction.) 
 
 As the eye with its refracting contents is 
 of greater density than the surrounding air 
 and light, it is with the first of these propo- 
 
ERRORS OF REFRACTION. 59 
 
 sitions that we have to do in considering 
 this subject. 
 
 If rays of light strike a denser medium in 
 a perfectly straight direction, they pass di- 
 rectly through such medium without devia- 
 tion from a straight line, as shown in Fig. 
 20. 
 
 Fio. 20. 
 
 Shows the passage of a right-angled ray through a medium of 
 increased density. (Oliver.) 
 
 If the rays strike such an obstruction in 
 any but a perfectly vertical or horizontal 
 position, such rays are bent or refracted, as 
 it is called, as shown in Fig. 21. 
 
 If the surface of the receiving object be 
 in the slightest degree deviated from a per- 
 fect level, either from its natural shape or 
 
60 
 
 THE EYE AND ITS CARE. 
 
 from being placed in a tilted position, the 
 rays will also be bent or refracted. 
 
 Fig. 21. 
 
 Shows the psissage of an oblique ray of light through a medium of 
 greater density. It also illustrates how the ray is deflected ftom its 
 course. 
 
 If rays of ligbt strike a substance of 
 greater density in anything but a vertical 
 or a horizontal direction, they are bent or 
 
ERUORS OF REFRACTION. 
 
 61 
 
 refracted toward the perpendicular of the 
 obstructing substance. (See Fig. 22.) 
 
 Tio. 22. 
 
 ■ —/—>- 
 
 Shows the refraction of a ray passing from a rare into a dense medium. 
 (Oliver.) 
 
 If rays of light strike a substance of 
 lesser density in any other than a vertical 
 or a horizontal direction, they are bent or 
 refracted away from the perpendicular of 
 the obstructing substance. (See Fig. 23.) 
 
 Let it be remembered that rays will always 
 be bent or refracted toward the thickest por- 
 
62 
 
 THE EYE AND ITS CARE. 
 
 tion of a lens, be it convex or concave 
 spherical, convex or concave cylindrical, or 
 prismatic. 
 
 
 Fio. 23. 
 
 
 
 
 1 
 
 
 1 7^ 
 
 ^Y 
 
 :/ 1 
 
 
 /- 1 
 / \ 
 
 ' 1 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Shows the refraction of a ray passing from a dense into a rare medium. 
 (Oliver.) 
 
 A prism, as applied to optics, is a trans- 
 parent, wedge-shaped medium bounded by 
 two surfaces that are inclined to each other. 
 The point where these two sides meet is 
 called the apex, and the point of their 
 greatest separation, the base. A prismatic 
 lens is therefore shaped as just described, 
 and rays of light that enter one of its 
 
ERRORS OF REFRACTION. 
 
 63 
 
 principal sides must be bent or refracted 
 toward its base, or perpendicularity. (See 
 Fig. 24.) 
 
 Tig. 24. 
 
 Shows the passage of a ray through a prism. (Oliver.) 
 
 All lenses are simply a natural evolution 
 from a plurality of prisms that are joined 
 together. Take, for instance, two prisms 
 placed together base to base, and we have 
 the first step in the evolution of a double- 
 convex lens. Rays of light passing through 
 such a combination pursue the same law or 
 course as if each prism stood alone. Such 
 rays enter the lens, bend toward the base, 
 and pass out, converging as they emerge. 
 As the two prisms lie base to base, and the 
 two sets of rays pursue the same law, the 
 
64 
 
 THE EYE AND ITS CARE. 
 
 rays proceeding from the upper prism pass- 
 ing downward and those from the lower 
 prism upward, they inevitably meet at a 
 certain fixed point that is parallel with the 
 bases of the two prisms. This point is 
 called the focus. It is a point that is de- 
 termined in all cases by the strength or 
 refractive power of the lens. (See Fig. 25.) 
 
 Fig, 25. 
 
 Fio. 26. 
 
 Shows the passage of parallel 
 rays through two prisms that 
 are placed base to base, form- 
 ing a focus. (Oliver.) 
 
 Shows the passage of two parallel 
 rays through two prisms that are 
 placed apex to apex, producing a 
 divergence. (Oliver.) 
 
 Take the opposite condition, viz., two 
 prisms set apex to apex, and the first step 
 in the evolution of a double concave lens 
 
ERRORS OF REFRACTION. 65 
 
 is obtained. Eays of light entering such a 
 combination are amenable to the same laws 
 that govern the previous case, but, the bases 
 in this case being exactly reversed in their 
 position, it will be seen that such rays must 
 be separated, dispersed, or diverged. (See 
 Fig. 26.) The same law which governs the 
 direction of rays in these two instances ob- 
 tains when a number of prisms are placed 
 together in graduated order to resemble a 
 double convex spherical lens. Each prism 
 refracts the entering rays towards its base, 
 and all the rays come together at the proper 
 point or focus. (See Fig. 27.) 
 
 When a series of prisms is placed in appo- 
 sition to one another so as to resemble a 
 double concave spherical lens, the rays are 
 dispersed according to the same law. (See 
 Fig. 28.) 
 
 Such instances are only sections of lenses, 
 and if it is wished to evolve a complete and 
 perfect convex or concave spherical lens, such 
 sections must be put together and joined as 
 
 e 6* 
 
66 
 
 THE EYE AND ITS CARE. 
 
 rio. 27. 
 
 Pig. 28. 
 
 Shows the passage of six 
 parallel rays through six trun- 
 cated prisms with their apices 
 pointing outward, forming a 
 xjompound focus. (Oliver.) 
 
 Shows the passage of six pai> 
 allel rays through six truncated 
 prisms with their bases pointing 
 outward, producing a divergence. 
 (Oliver.) 
 
 Fig. 29. 
 
 Fig. 30. 
 
 Shows a biconvex spherical lens. 
 (Oliver.) 
 
 Shows a biconcave spherical lens. 
 (Oliver.) 
 
ERRORS OF REFRACTION. 
 
 67 
 
 indicated in the drawings, and the surfaces 
 smoothed and accurately graduated. As a 
 result, a convex or a concave spherical lens 
 capable of focussing or dispersing rays is 
 obtained. (See Figs. 29 and 30.) 
 
 A cylindrically shaped lens is evolved in 
 the same manner, except that the completed 
 
 PlQ. 31. 
 
 Fig. 32. 
 
 Shows a biconvex cylindrical 
 lens. (Oliver.) 
 
 Shows a biconcave cylindrical 
 lens. (Oliver.) 
 
 combination is joined together laterally, the 
 prisms are not united around a circle, as it 
 were, but are placed side by side, so that 
 the focus, which in a convex spherical lens 
 is punctated, becomes elongated into a line 
 (see Fig. 33) in a convex cylindrical lens, 
 while the dispersion of rays, which in a con- 
 
68 THE EYE AND ITS CARE. 
 
 Fio. 33. 
 
 Exhibits the formation of a focal line from two parallel planes by a 
 combination of truncated prisms forming a biconvex cylindrical lens. 
 (Oliver.) 
 
 Fig. 34. 
 
 Exhibits the dispersion of two parallel planes by a combination of 
 truncated pnsms forming a biconcave cylindrical lens. (Oliver.) 
 
ERRORS OF REFRACTION. 69 
 
 cave spherical lens is circular, becomes also 
 elongated into a line (see Fig. 34) in a con- 
 cave cylindrical lens. 
 
 These points of dissimilarity inevitably- 
 lead to tbe conclusion that while, with con- 
 vex and concave spherical lenses, the rays 
 becoming converged or diverged are the 
 same, no matter at what axis the lens is 
 held ; with convex or concave cylindrical 
 lenses, the rays, becoming either converged 
 or diverged, being linear and not punctated, 
 must move with the rotation of the lens upon 
 its axis. 
 
 This is in fact the very element that 
 renders such lenses useful in the correction 
 of astigmatism, where the cylindrical shape 
 of the cornea is neutralized by the cylindri- 
 cal shape of the lens, when set at the proper 
 axis in a spectacle frame. 
 
 Having now given a practical, but still 
 sufficiently accurate idea of the anatomy and 
 physiology of the eye, the principles of light 
 and refraction, and also some ideas concern- 
 
70 THE EYE AND ITS CARE. 
 
 ing the evolution of lenses and tlieir func- 
 tions, attention should be turned to those 
 errors of refraction which are incident to the 
 human eye. 
 
 HYPEEMETEOPIA. 
 
 To recapitulate : Light is said to be re- 
 fracted when its rays passing from one 
 medium to another become bent or refracted 
 in different directions in correspondence with 
 the nature and relative position of the 
 second medium. 
 
 If light passes through a convex spherical 
 glass, the rays are refracted in such a manner 
 as to converge, to come together, or to focus 
 at a point that corresponds with the strength 
 of the glass. Therefore, a three-inch con- 
 vex lens focuses light at a distance of three 
 inches from the lens, a two-inch convex lens 
 at two inches, etc. (See Fig. 35.) 
 
 If the surface of the glass is concave and 
 spherical, rays of light as they pass through 
 it are spread or diverged. (See Fig. 36.) 
 
ERRORS OF REFRACTION. 
 
 71 
 
 It can be seen that the eye, being a con- 
 vex medium, converges rays as they pass 
 through it, and brings them to a focus on 
 
 Pig. 35. 
 
 Shows the focussing of paral- 
 lel rays of light that have passed 
 through a biconvex lens. 
 
 Fig 
 
 36. 
 
 
 ^_^- 
 
 
 
 
 
 
 
 
 
 
 ^^^- 
 
 Shows the divergence of paral- 
 lel rays of light that have passed 
 through a biconcave lens. 
 
 the posterior or receiving wall, known as the 
 retina. 
 
 The principle of refraction is intimately 
 involved in the adjustment of glasses, as it 
 is upon this principle that either convex or 
 concave glasses are prescribed. If it is de- 
 sirable to bring rays to a focus sooner than 
 occurs naturally in the eye under considera- 
 tion, a convex glass is used. This is done 
 for the reason that such a lens converges 
 rays. If, on the contrary, it is desirable to 
 throw the rays farther back in the eye upon 
 
72 THE EYE AND ITS CARE. 
 
 account of an elongated eyeball, a concave 
 glass is used. This is done because such a 
 lens diverges or spreads rays. 
 
 Refraction, as referring to the eye, means 
 the bending of rays proceeding from a dis- 
 tant object to focus upon the retina. Normal 
 refraction is where this act is accurately per- 
 formed, and abnormal refraction is where 
 such rays are not naturally so focussed. 
 
 The normal eye is so constructed, as to its 
 length from its anterior to its posterior 
 extremity, that rays proceeding from a 
 distant object are focussed exactly upon the 
 retina without any voluntary or involuntary 
 effort. Any deviation from such an antero- 
 posterior diameter from the cornea to the 
 retina constitutes one of the forms of erro- 
 neous refraction, and will, consequently, be 
 followed by abnormal conditions of vision. 
 If the eye is of exactly the proper length, 
 rays proceeding from an object will focus 
 exactly on the retina. If the eyeball is 
 too short, rays will focus {theoretically) 
 
EREOnS OF REFRACTION. 
 Fia. 37. 
 
 73 
 
 Illustrates the emmetropic eye, and shows how rays focus accurately 
 upon the retina. 
 
 Fig. 38. 
 
 Illustrates the hypermetropic eye, and shows how rays focus (theoreti- 
 cally) behind the retina. 
 
 Pig. 39. 
 
 Illustrates the myopic eye, and shows how rays focus in front of the 
 retina. 
 D 7 
 
74 THE EYE AND ITS CARE. 
 
 behind the retina, and the impression re- 
 ceived upon the retina will be blurred and 
 diffused. If the eyeball is too long, rays 
 will focus in front of the retina, and then 
 crossing one another and diverging will 
 reach the retina in a blurred or diffused 
 condition. The proper point of focussing is 
 fixed and unvarying. If the retina is not 
 there to meet the rays, vision is said to be 
 impaired. 
 
 Normal refraction is called emmetropia. 
 Where the eyeball is too short, or where 
 there is too little focussing material, the 
 condition is termed hypermetropia. Where 
 the eyeball is too long, or where there is too 
 much focussing material, myopia is said to 
 be present. 
 
 In hypermetropia, then, rays proceeding 
 from an object are focussed, at least theo- 
 retically, behind the retina. The retinal 
 plane being advanced farther forward than 
 the proper focal point renders a real focus 
 of the rays impossible, as they cannot pierce 
 
ERRORS OF REFRACTION. 75 
 
 an opaque wall. In consequence, the focal 
 point occupies an imaginary place behind 
 the retina. The result of this error in re- 
 fraction is to produce a blurred and indis- 
 
 PlO. 40. 
 
 Represents a hypermetropic eye. Here the rays focus behind the 
 retina, but the ciliary muscle, or muscle of accommodation, forces the 
 lens into a condition ^of increased convexity, causing the rays to 
 become focussed upon the retina. 
 
 tinct retinal image of the object upon which 
 gaze is concentrated. At least, in the great 
 majority of instances, such would be the 
 case were it not for the intervention of the 
 ciliary muscle and crystalline lens, which 
 come to the aid of the eye and enable it to 
 focus distinctly. Some pages back, it has 
 been shown what constitutes this wonderful 
 physiological process of accommodation. It 
 
76 THE EYE AND ITS CARE. 
 
 ■will be remembered tbat it is accomplished 
 by the exertion of the ciliary muscle, acting 
 upon the lens and forcing it into a condition 
 of increased convexity. So here, in the 
 hypermetropic eye, an involuntary effort of 
 the ciliary muscle is produced and main- 
 tained. In such eyes, however, while such 
 an exertion, when retained within the bounds 
 of physiological limit, is non-injurious, where 
 an excessive and constant effort is effected 
 it becomes a pathological knd abnormal 
 feature. This effort corresponds with the 
 amount of hypermetropia that is involved 
 in each particular individual. If the eye- 
 ball is shortened only to a slight extent, the 
 amount of increased convexity maintained 
 by the lens is correspondingly slight, while 
 in cases of great shortening the lens becomes 
 extremely convex. It therefore becomes 
 essential, if normal sight is produced, to 
 lengthen the eyeball, as it were, and to 
 force the rays to focus upon the retina. 
 As the eyeball itself cannot be lengthened, 
 
ERRORS OF REFRACTION. 77 
 
 it becomes necessary that the antero-pos- 
 terior diameter of the lens (or part through 
 which the image rays pass) should be- 
 come adequately longer, or more convex, 
 which practically amounts to the same 
 thing. In such cases this, the so-called 
 accommodative eflfort, takes place not only 
 when the eye is used for close work, but 
 at all times, except during the hours of 
 sleep. The result of this perpetual over- 
 exertion is rebellion, just as it would be 
 if any other muscle, nerve, or function 
 in the body were abused. For example, 
 were a man to labor continuously twenty 
 hours in the twenty-four, he would soon 
 reach a point where human endurance would 
 cry out against the folly. If strong and 
 healthy, he might endure it several years, 
 but if sickly and debilitated, he would 
 sooner reach the limit of his powers. This 
 is exactly the condition in hypermetropia 
 when the ciliary muscle becomes perpetually 
 overtaxed. No complaint may be made for 
 
78 THE EYE AND ITS CARE. 
 
 years, especially if tlie individual happens 
 to be strong and robust, or if tbe person be 
 young, with a soft and pliable lens that is 
 easily shaped to the will of the ciliary 
 muscle. Sooner or later, however, the ac- 
 commodative apparatus will protest. This 
 is more liable to occur after some long and 
 debilitating sickness, especially if the pa- 
 tients use their eyes for near-work whilst 
 lying in bed during convalescence, before 
 strength has become re-established. Again, 
 it may occur during the course of some slow 
 and exhausting chronic disease. Moreover, 
 it may follow excessive or imprudent use of 
 the eyes in an otherwise healthy individual. 
 Whatever the cause may be, certain symp- 
 toms, which are classed under the one term 
 asthenopia, make their appearance. By this 
 is meant a tired and weary feeling of the 
 eyes and head ; an inability to continue long 
 at any close occupation ; headaches, especially 
 in the front and back part of the head ; a 
 heaviness and apparent roughness of the 
 
ERRORS OF REFRACTION. 79 
 
 lids ; overpowering sense of sleepiness early 
 in the evening, soon after artificial lights are 
 used ; various forms of neuralgia, etc. 
 
 What is to be done to relieve such cases 
 can be readily answered by any one who 
 comprehends the significance of the symp- 
 toms. It has been shown that they indicate 
 a continual and abnormal taxation of the 
 strength of the ciliary muscle in order to 
 add to the convexity of the lens. To relieve 
 this taxation, it is merely necessary, then, to 
 place a lens of sufficient convexity in front 
 of the eye to compensate for the degree of 
 refractive error. By the use of certain 
 tests, the physician ascertains the amount of 
 antero-posterior shortening existing in a 
 given eye. He then prescribes a lens that is 
 sufficiently convex to produce more quickly 
 a suitable convergence of entering rays, 
 and thus compensate for such shortening. 
 In this way a proper length of light ray 
 is established "and the strain is taken off" 
 from the ciliary muscle and crystalline lens. 
 
80 THE EYE AND ITS CARE. 
 
 MYOPIA. 
 
 This term is significant of the opposite 
 refractive condition from hypermetropia. 
 As has already been mentioned, myopia 
 signifies a lengthened axis of the eyeball 
 from the cornea to the retina, or, in other 
 words, too much intraocular focussing mate- 
 rial, so that rays from distant objects, in- 
 stead of forming upon the retina a clear and 
 distinct focus, fall in front of the retina, 
 cross in the interior of the eye, and reach 
 the retina in a diffused or blurred condition. 
 The result is a greater or less degree of in- 
 distinct vision, the amount of diminution of 
 sight being in direct proportion to the degree 
 of abnormal lengthening of the eyeball. As 
 a rule, the condition is not accompanied by 
 any marked asthenopic symptoms. 
 
 Myopia is sometimes expressed by the 
 laity as "near-sightedness." By some 
 "long-sightedness" is supposed to be a term 
 of contradistinction, but this is clearly in- 
 
ERRORS OF REFRACTIOX. 81 
 
 correct, as it frequently happens that many 
 hypermetropic people possess poor distant 
 vision. " Long-sightedness'' might he, and 
 has heen, appropriately used to ex2:)ress 
 presbyopia, or the poor vision of old age, 
 when it becomes uecessarj' to hold print at a 
 long distance in order to read it, but, un- 
 fortunately, the application of the term has 
 become mixed or diverted to express hyper- 
 metropia. 
 
 The last chapter in this book will treat 
 largely of myopia, its extensive existence, 
 causes and relation to school life, etc. ; so 
 that this portion of the subject will be re- 
 served until then. 
 
 It has been said that a myopic eye is an 
 elongated eve, or one with too much focus- 
 sing power, and that the rays which proceed 
 from an object are focussed in front of the 
 retina, and hence reach this membrane in a 
 diffused condition. In hypermetropia nature 
 compels an increased convexity of the crystal- 
 line lens, by taxing the power of the ciliary 
 
82 THE EYE AND ITS CARE. 
 
 muscle. In myopia she allows a relaxation 
 of the ciliary muscle, which, upon account 
 of the elasticity of the lenticular capsule, 
 induces as flat a condition of the lens as 
 possible, in order to throw the focus of rays 
 farther back, and produce clear vision. In 
 other words, the accommodative function is 
 reduced to a minimum, thus accounting for 
 the ordinary lack of asthenopic symptoms in 
 such cases, which, when found, are usually 
 produced by a strain of the internal recti 
 muscles, from inducing convergence of the 
 two eyeballs, which, owing to their elongated 
 shape, is difiicult to accomplish. 
 
 In very mild cases a flattening of the 
 lens to its full extent may assist in miti- 
 gating an existing myopia, but in others its 
 utility is reduced to a minimum. Theoreti- 
 cally, the eye must be still further flat- 
 tened, or at least something must be done 
 (which amounts to the same thing) to throw 
 the rays proceeding from an object farther 
 back, so that the focus will just touch the 
 
ERRORS OF REFRACTION. 83 
 
 retina and produce clear vision. This can 
 be accomplished by a concave glass. After 
 first ascertaining, by certain tests, the degree 
 of near-sightedness, a corresponding strength 
 of concave glass should be placed in front of 
 the eye, thus focussing rays upon the retina, 
 and restoring vision to a normal standard. 
 
 PRESBYOPIA. * 
 
 Presbyopia is one of the ocular evidences 
 of advancing years. In youth the muscles, 
 nerves, joints, and other tissues and constit- 
 uents of the body are strong and pliable, 
 with almost unlimited power and boundless 
 capability ; but as youth is succeeded by 
 middle life, and this by old age, these func- 
 tions become more and more impaired. It 
 is thus found that the possibilities of early 
 life become the impossibilities of maturity 
 and old age. The eye is no exception to 
 this rule. Here it is principally in the 
 accommodative apparatus that such increas- 
 ing feebleness is exemplified. In the early 
 
84: THE EYE AND ITS CARE. 
 
 years of life the ciliary muscle, ciliary liga- 
 ment, lenticular capsule, and crystalline 
 lens respond with alacrity to the slightest 
 need or wish of the individual, but, as the 
 meridian of life is passed (which occurs at 
 about the fortieth year), the ciliary muscle 
 and ciliary ligament become less active, the 
 capsule of the crystalline lens becomes less 
 elastic, and the crystalline lens itself be- 
 comes harder, more compact, and less capa- 
 ble of changing its shape to one of greater 
 convexity when small and near objects are 
 brought into view. In other words, active 
 accommodation becomes more and more 
 difficult, until the individual is obliged to 
 employ stronger illumination for reading, 
 writing, etc., and must hold the object at 
 an increased distance from the eye. The 
 man who has always possessed strong eyes 
 finds that his reading light is no longer as 
 strong as it formerly was, that the print of 
 papers, books, etc., is of inferior quality, that 
 he is compelled to hold the book at some dis- 
 
ERROnS OF REFRACTION. 85 
 
 tance in order to see more or less distinctly, 
 and that his eyes feel tired and weary after 
 use. He worries along in this way, either 
 through ignorance as to the cause, or upon 
 account of an unwillingness to acknowledge 
 the encroachments of age, until he secures 
 a pair of properly adjusted glasses. Peace 
 is then restored, for a period at least. As 
 the presbyopic condition advances, increas- 
 ingly stronger glasses become necessary to 
 meet the emergencies of the case. As the 
 female sex grows old earlier than the male, 
 so presbyopia, as one of the attributes of 
 age, is usually manifested in women about 
 two years earlier than in men. Owing, 
 however, to an unfortunate pride in personal 
 appearance, and an indisposition to acknowl- 
 edge age, women generally refuse to wear 
 glasses until their use is rendered absolutely 
 necessary by a sheer inability to make use 
 of the eyes. 
 
 In testing an eye for presbyopia, a very 
 small and distinct type is used. This is 
 
86 THE EYE AND ITS CAME. 
 
 known as No. 1 Snellen type, and should 
 be seen by tbe normal eye at a point at 
 
 Fig. 41. 
 
 No. 1. 
 
 The eye b a delicate structure, ezceedinglj senaitice, yet performiag an immeiue amoont of labor without 
 aaj appreciable btigue, and adapting itaelf to varioua distances and to varioua intensities of light, so as to 
 astonUh even the most casual observer. Thos. ire can read by the light of the moon, bj twilight, by the light 
 fiom a small taper, etc, and theso lights are by no means to b« compared with the light emanating from the 
 sun. The light from the sun is estimated to be 300,000 times more brilliant than that from the moon ; or 
 equal to that glTen out by 6.000 wax candles of moderate size, supposed to be placed at 
 
 Shows what is known as No. 1 test-type. 
 
 least as near to the eye as ten inebes. The 
 nearest distance at wbicb tbis type can be 
 seen is called tbe " near-point of vision," 
 and tbe fartbest point at wbicb it can be 
 seen is termed tbe "far-point of vision." 
 Tbe "near-point of vision" in youtb is 
 mucb nearer tban ten incbes, but presbyopia 
 is not said to be present until tbe " near- 
 point" recedes fartber tban ten incbes from 
 tbe eye. Presbyopia is tben a recession of 
 the near-point of vision tbat accompanies 
 old age ; and tbe object of fitting a glass is 
 to bring tbe near-point of vision from an 
 abnormal distance, or perhaps an inability to 
 see Xo. 1 Snellen type at all, back to ten 
 
ERRORS OF REFRACTION. 87 
 
 inches. The weakest glass that accomplishes 
 this is usually the one chosen, as, the weaker 
 the glass, the less restricted will be the far- 
 point of vision, and, consequently, the wider 
 will be the range of vision. This is of 
 importance to most people, who find it incon- 
 venient to take off a glass fitted for pres- 
 byopia, in order to see a few feet away. 
 
 After securing a pair of glasses for pres- 
 byopia, patients often inquire as to the 
 length of time that the lenses will remain 
 satisfactory. This is something that cannot 
 be satisfactorily answered, for, while a glass 
 usually answers the purpose for perhaps two 
 years, it sometimes happens that it may last 
 much longer, or, on the contrary, it may 
 require alteration in a few months. In a 
 large measure each patient should be his 
 own guide. As a rule, a glass may be safely 
 worn as long as it produces ease and com- 
 fort, but should be discarded when reverse 
 conditions obtain. After discussing the prin- 
 ciple underlying the correction of hyper- 
 
88 THE EYE AND ITS CARE. 
 
 metropia and myopia, it seems almost un- 
 necessary to suggest the kind of glass that 
 is required for neutralizing presbyopia. In 
 presbyopia there is a flattening of the lens 
 and an inability to bring it to a sufiicient de- 
 gree of convexity to easily discern print, etc. 
 The logical remedy is clearly to increase the 
 convexity of the crystalline lens by artificial 
 means, thus restoring the power for near- 
 work. This is done by placing in front of 
 the eye a convex glass of such a degree of 
 convexity as to bring back the near-point 
 of vision to ten inches, and at the same 
 time to allow as much elasticity to the range 
 of accommodation as possible. 
 
 ASTIGMATISM. 
 
 Astigmatism is a word that is frequently 
 heard upon the lips of people who, whilst 
 knowing little or nothing about the condi- 
 tion, seem to think that it is a very distin- 
 guished and desirable disease. 
 
 Astigmatism is an error of refraction that 
 
ERRORS OF REFRACTION. 89 
 
 is largely dependent upon a more or less 
 cylindrical curvature of the cornea, which 
 should, as already explained, be practically 
 spherical in outline. If an individual looks 
 out through a spherically-shaped cornea, all 
 portions of an object are seen with equal 
 clearness and distinctness. If, on the con- 
 trary, the cornea is cylindrically shaped, 
 objects must appear distorted or be seen 
 with unequal clearness, thus producing 
 various asthenopic symptoms that may cause 
 almost unendurable suffering. 
 
 The reader has doubtless seen cylindrical 
 mirrors, which, when looked at with the 
 long axis of the reflector situated vertically, 
 render the person looking at himself ex- 
 tremely long and thin. When, however, 
 the long axis of the mirror is placed hori- 
 zontally, a short and fat apj)earance of the 
 observer is produced. This experiment will, 
 in an exaggerated way, serve to illustrate 
 the distortion of objects that is occasioned 
 by a cylindrical lens when placed before 
 
90 THE EYE AND ITS CARE. 
 
 the eye. It also serves to illustrate the 
 distorted appearance of objects when seen 
 through a cylindrically-shaped cornea. This 
 is often quite manifest to those who are un- 
 familiar with the subject, but who go to the 
 physician with the voluntary remark that 
 they can see the vertical lines in a brick 
 wall clearly, but are unable to discern the 
 horizontal, or vice versa, etc. etc. 
 
 Astigmatism may appear in several varie- 
 ties and be situated in any axis. For in- 
 stance, it may be vertical (90°), or hori- 
 zontal (0° or 180°), or at any intervening 
 angle. 
 
 Ordinarily there are five varieties of astig- 
 matism. The first and the second are known 
 as simple astigmatism, where one meridian 
 of the eye is either myopic or hypermetro- 
 pic and the other meridian is emmetropic, 
 or normal. The third is known as com- 
 pound hypermetropic astigmatism, where 
 two degrees of hypermetropia are situated 
 at right angles to one another. The fourth 
 
ERRORS OF REFRACTION. 
 
 91 
 
 is known as compound myopic astigmatism, 
 where two degrees of myopia exist at right 
 angles to one another. The fifth is termed 
 mixed astigmatism, because one meridian of 
 the cornea is myopic and the other is hyper- 
 metropic. 
 
 Tig. 42. 
 
 Shows a convex cylindrical 
 lens. 
 
 Fig. 
 
 43. 
 
 
 If' 
 
 
 ll 
 
 t 
 
 
 J 
 
 Shows the form of a concave 
 cylindrical lens. 
 
 When the astigmatism is of a hyperme- 
 tropic character, it generally indicates that 
 there is a cylindrical corneal flattening. If 
 it is of a myopic character, it ordinarily in- 
 dicates that there is a cylindrical corneal 
 elevation. The former variety is to be cor- 
 rected by convex cylindrical lenses, and the 
 
92 THE EYE AND ITS CARE. 
 
 latter is to be corrected by concave cylindri- 
 cal lenses, eacli set at their proper axis. For 
 instance, in a case of simple hypermetropic 
 astigmatism, a simple convex cylindrical lens 
 must be used. For simple myopic astigma- 
 tism, a simple concave cylinder should be 
 employed. For compound hypermetropic 
 astigmatism, a glass that is ground spheri- 
 cally convex on one side and cylindrically 
 convex on the other becomes necessary. For 
 compound myopic astigmatism, a glass that 
 is ground cylindrically concave on one side 
 and spherically concave on the other is to 
 be used. For mixed astigmatism, a glass 
 that is ground convex cylindrically on one 
 side and concave cylindrically on the other, 
 the two axes set at right angles to each 
 other, is the one that becomes necessary. 
 
 It must not be forgotten that astigmatism 
 may coexist with presbyopia, and that its 
 presence must be remembered in fitting a 
 spherical glass for the latter condition. This 
 can be done by combining the necessary 
 
ERRORS OF REFRACTION. 93 
 
 spherical lens with a proper cylindrical 
 lens, the one being ground upon one side of 
 the glass and the other upon the opposite 
 side of the glass. 
 
CHAPTER III. 
 
 TEST-TYPES, GLASSES, ETC. 
 
 A BRIEF description of the methods pur- 
 sued by physicians in testing the eyes of 
 patients may be of interest to the general 
 reader. 
 
 Of the many methods to be pursued in 
 studying ocular refraction, the principal one 
 is accomplished by means of a series of 
 test-types and a set of trial glasses. The 
 latter contains a great variety of spherical 
 and cylindrical lenses, both convex and con- 
 cave in character, arranged according to 
 strength or degree. There is also a pair of 
 trial frames, so constructed that the lenses 
 can be easily slipped into the frames and 
 readily removed. These frames are gradu- 
 ated into degrees of a circle, thus enabling 
 any prismatic or cylindrical glass to be 
 turned to any desired axis. The test-types 
 
 94 
 
TEST-TYPES, GLASSES, ETC. 
 
 95 
 
 are printed upon a card. These letters are 
 of varying sizes, each size situated upon a 
 
 Pig. 44. 
 
 Shows a set of trial glasses. 
 
 corresponding line. According to optical 
 and mathematical calculations, these letters 
 must be seen by a normal eye at certain 
 definite distances. For instance, the largest 
 letter upon the miniature card here shown 
 should, if the card was of natural and not 
 
96 
 
 THE EYE AND ITS CARE. 
 
 FiQ. 45. 
 
 reduced size, be seen at two hundred feet. 
 The next should be recognized at one hun- 
 dred feet ; the next at seventy 
 feet; and the others at fifty, 
 ^C* forty, thirty, and twenty feet 
 
 respectively. In this way it 
 can be quickly ascertained 
 whether vision is normal or 
 not. As a rule, physicians 
 make the line that should be 
 seen at twenty feet their stand- 
 ard of visual measurement. 
 To do this the patient must be 
 placed twenty feet away from 
 the test-types. 
 This rule is, however, purely arbitrary, 
 as any other line might be used, only of 
 course the position of the patient must be 
 accordingly changed. For instance, if a 
 thirty-foot line on a card is used, the patient 
 should be seated thirty feet from the test- 
 types, etc. 
 
 The question is often asked, why do 
 
 T B 
 
 D L N 
 
 P T E R 
 
 r Z B D E 
 
 OS £ ZT C 
 
 Kr oars s 
 
 Exhibits a card 
 of test-types (much, 
 diminished in size). 
 
TEST-TYPES, GLASSES, ETC. 97 
 
 physicians so often use belladonna, or its 
 active principle, atropine, in testing eyes? 
 The answer may be briefly and sufficiently 
 stated for the general reader, as follows : 
 
 Fig. 46. 
 
 Shows the actual size of the test-type which should be seen by the 
 normal or emmetropic eye at twenty feet. 
 
 Owing to the excessive activity on the part 
 of the ciliary muscle — especially in hyper- 
 metropia and astigmatism — the muscle some- 
 times develops a condition of greater or less 
 irritability and spasm, which masks the 7'eal 
 refraction of the eye. Belladonna has the 
 power of paralyzing the ciliary muscle, thus 
 doing away with the activity of the muscle 
 during an examination, which allows the 
 true refraction to be revealed. When this 
 is done the eye can be accurately tested. It 
 must be remembered that each eye must be 
 tested separately, as the refraction of the two 
 eyes may materially differ. 
 
98 THE EYE AND ITS CARE. 
 
 By means of the methods just indicated, 
 as well as by other procedures (which could 
 be appropriately mentioned only in a book 
 designed for medical men), errors of re- 
 fraction may be accurately estimated. Al- 
 though it appears simple, and in reality is 
 easy in many features, yet it may be said 
 of this class of professional labor, that it 
 is the most painstaking, the most difficult, 
 and the most nerve-exhausting that falls 
 within the province of any conscientious 
 physician, and at the same time is the labor 
 that is rewarded by the smallest compensa- 
 tion. There exists a time-honored idea that 
 any one can fit glasses, and that it is foolish 
 prodigality to pay a fee for securing an 
 accurate correction of refraction by lenses. 
 Upon the contrary, such work requires 
 eminent skill, patience and knowledge, and 
 it is to be regretted that any government 
 permits such practices in department stores, 
 fairs, or, in short, in any place outside of a 
 physician's consulting room. 
 
TEST-TYPES, GLASSES, ETC. 9d 
 
 The query is frequently propounded, 
 shall I wear eye-glasses or spectacles ? The 
 answer depends on the nature of the glass 
 required and the shape of the facial features. 
 On general principles it is always better to 
 Avear spectacles, especially if the glass is 
 strong or if it is a cylinder, as such lenses 
 should be accurately placed before the eye, 
 with the centre of the lens opposite the 
 centre of the pupil. If the glass is strong 
 and the two centres do not correspond, the 
 patient fails to acquire the presumed strength 
 of the glass, and hence suffers from a 
 prismatic effect, which by acting improperly 
 on one or more of the extra-ocular muscles 
 may produce injurious consequences. Again, 
 if the lens is a cylinder and is designed to 
 be placed at a certain axis, it should always 
 remain at this axis when on the face. This 
 is best accomplished by spectacles, for the 
 reason that eye-glasses are liable to change 
 of position and consequent misplacement of 
 the cylinder axis. Exceptions are, however, 
 
100 THE EYE AND ITS CARE. 
 
 not infrequently made to meet the emer- 
 gencies of special cases. A patient possessed 
 of a nose that is shaped for the support of 
 eye-glasses may be able to retain them in 
 accurate position. If it is necessary that 
 glasses be frequently removed, or if the 
 question of personal appearance is to play 
 an important role in the consideration of the 
 case, eye-glasses may be permitted, though 
 even then they are not desirable. If, how- 
 ever, the nose is flat, the eyes widely 
 separated, and the glass is strong or cylin- 
 drical, spectacles must be unqualifiedly ad- 
 vised. 
 
 Rimless or skeleton glasses, although 
 popular, possess several disadvantages. They 
 are supplied with four rivets that pass 
 through the glasses. To some eyes these 
 glasses are not only an annoyance, on ac- 
 count of the rivets, but are very liable to 
 breakage. In addition to this latter some- 
 times exasperating and expensive objection, 
 such glasses will inevitably become loose- 
 
TEST-TYPES, GLASSES, ETC. 
 
 101 
 
 jointed and the lenses at once assume dif- 
 ferent angles. If skeleton glasses are worn, 
 they should be ground dull at the edges, 
 so as to prevent the annoying effect of 
 prismatic colors. They should also be fre- 
 quently repaired, in order that they may be 
 kept in proper condition. 
 
 Fig. 47. 
 
 Shows a pair of bi-focal glasses. The upper portion is arranged for 
 looking at a distance, and the lower for close-work, such as reading, 
 writing, etc. 
 
 Occasionally there is a necessity for two 
 sets of glasses, one to be used for distance 
 and the other for reading ; under these 
 circumstances, the example of Benjamin 
 Franklin may be followed, in which he 
 used split or bi-focal glasses, where two 
 lenses (the upper for distance and the 
 
 9* 
 
102 THE EYE AND ITS CARE. 
 
 lower for reading) are contained in a single 
 frame. This arrangement is very con- 
 venient, though difficult to become accus- 
 tomed to ; but when this has once been 
 accomplished, they are much appreciated, 
 as they enable the patient to use one pair 
 of glasses for all purposes. 
 
 Sometimes it is necessary to wear even 
 three pairs of glasses. Especially is this 
 so with musicians, artists, etc., who are 
 compelled to use their eyes accurately at 
 some particular distance, such as a music- 
 rack, an easel, etc. 
 
 Great stress is sometimes laid on the pur- 
 chasing and wearing of what are known as 
 "pebble" glasses. It may be briefly said 
 that the ordinary glass sold by a competent 
 optician is sufficiently perfect. In fact, 
 such glass is usually purchased when peb- 
 ble glasses are paid for, as it requires both 
 skill and experimentation to discriminate 
 between the two varieties. 
 
 The inquiry is often made as to whether 
 
TEST-TYPES, GLASSES, ETC. 103 
 
 it is advisable to wear colored glasses, and, 
 if so, what kind should be worn. Colored 
 glasses should not be employed unless there 
 is a specific reason for their use, such as a 
 diseased eye, or temporary exposure to bright 
 and trying lights. It is therefore not ad- 
 visable to accustom the eye to their use, as 
 eventually the wearing of them becomes 
 almost a necessity. When worn, however, 
 a medium shade of smoke glass, of good 
 quality, is the best form to use. 
 
CHAPTBE IV. 
 
 THE GENERAL CARE OP THE EYE. 
 
 The care of the eye commences at birth, 
 and continues uninterruptedly until death. 
 A large proportion of the inmates of blind 
 asylums are sent there upon account of an 
 inflammation that occurs about three days 
 after birth. This form of ocular inflamma- 
 tion is known as " ophthalmia neonatorum," 
 or the " conjunctivitis of the new-born." It 
 is an inflammation of the conjunctiva of a 
 peculiarly severe type, and often results in 
 impairment of vision. Intelligent physicians 
 should be retained at such important occa- 
 sions, and nurses and parents should strictly 
 follow their advice, for, if such counsel be 
 in accordance with modern science, the per- 
 centage of blindness among new-born babes 
 will thereby be greatly reduced. Even if 
 such an unfortunate disease does not exist, 
 
 104 
 
THE GENERAL CARE OF THE EYE. 105 
 
 nurses and parents should exercise great 
 care of the eyes at such times by keeping 
 them clean and by frequently bathing them 
 in warm water. Occasionally, if the lashes 
 seem scaly, the greasing of the edges of 
 the lids with a little vaseline will prove 
 beneficial. 
 
 Pig. 4a. 
 
 Shows the external appearance of ophthalmia neonatorum, or conjunc- 
 tivitis of the new-born. 
 
 Eyes of young infants should be protected 
 from glaring lights, and it is advisable that 
 their room, while warm, well-ventilated, and 
 cheerful, should not be so situated as to ex- 
 pose the eyes to the direct rays of the sun. 
 The value of this suggestion is not confined 
 to indoor care, for the delicate retina may 
 
106 THE EYE AND ITS CARE. 
 
 easily be injured, by the not unusual prac- 
 tice of allowing a child to lie in its carriage 
 and gaze directly at the sun, without being 
 protected by an umbrella, a veil, etc. 
 
 The attention of an infant should not 
 be directed to objects held close to its face. 
 The reason for this is that marked and 
 frequent convergence of the eyes may be 
 liable to produce strabismus or cross-eyes. 
 As the child grows older, this precaution 
 should not be forgotten, remembering, further, 
 the possibility of producing myopia under 
 the pressure of extreme convergence and 
 close application. Children should therefore 
 be discouraged from playing with small 
 objects, toys, etc., and from poring over 
 story and picture books. They should be 
 encouraged in out-door amusement and sports, 
 where the eyes during these developing 
 periods of life can have wide range and free 
 scope, and where the general physical health 
 and development may take precedence over 
 ocular and intellectual labor. 
 
THE GENERAL CARE OF THE EYE. 107 
 
 Ordinarily, there is a great indisjaosition 
 to wear glasses ; a prejudice that is born and 
 fostered of ignorance. Few misapprehen- 
 sions are more foolish, for the proper adjust- 
 ment of lenses to the improperly refracting 
 eye is one of the greatest boons to humanity. 
 Where glasses are needed, they should be 
 worn, and a failure to do so means deterio- 
 ration of ocular health and functions, and 
 usually produces much unnecessary suffering 
 to the individual. 
 
 After what has been said, it is hardly 
 necessary to further indicate the necessity 
 for glasses for the correction of the different 
 errors of refraction, nor to urge the necessity 
 of consulting a physician upon the approach 
 of obstinate headaches or other asthenopic 
 symptoms, or the discovery of a lack of 
 vision. 
 
 To those who wear glasses, a few words 
 as to their proper use may not be inappro- 
 priate. In the first place, if eye-glasses are 
 worn, they should not be folded together, as, 
 
108 THE EYE AND ITS CARE. 
 
 by SO doing, they soon become misshapen, 
 scratched, or dulled. They should either 
 be hung unfolded on a hook on the outside 
 of the dress, or carried flat in a case, thus 
 keeping their shape and lustre. For the 
 same reason, glasses should not be laid care- 
 lessly upon tables, stands, etc. They should 
 be kept clean. This may be done by 
 rubbing them gently with a clean and soft 
 cloth, it being unnecessary (in accordance 
 with popular fancy) to employ chamois- 
 skin. 
 
 Glasses should not be worn indefinitely. 
 They should be changed or repaired as they 
 become worn, nicked, cracked, and out of 
 shape. All things considered, a gold frame 
 is the best and cheapest that can be 
 purchased. Gold frames are pliable, and 
 yet hold their shape well. They are also 
 durable, and will usually outwear several 
 steel frames. They do not hurt the ears or 
 nose, and are free from rust. These advan- 
 tages, together with the fact that they look 
 
THE GENERAL CARE OF THE EYE. 109 
 
 as well as glasses can, certainly recommend 
 them for use. 
 
 If colored glasses are to be used, a good 
 quality of material should be selected. To 
 do this, it is best to patronize a reputable 
 optician and pay him an adequate price, 
 instead of purchasing them of a street 
 vender or from other irresponsible parties. 
 There is much difference in colored glasses. 
 Some are clear, while others are full of 
 flaws and imperfections. Some are smoothly 
 ground, whilst others have rough surfaces. 
 Some have no refractive power, while others 
 have one that is annoying and, at times, 
 even injurious. 
 
 An important point in obtaining glasses 
 is not only to have the lenses properly 
 prescribed by a physician, but also to see 
 that the frames are correctly adjusted by a 
 competent optician. This is necessary, as 
 there are so many varieties of facial features 
 which require genuine skill and judgment 
 
 to harmonize with lenses and frames, that 
 
 lu 
 
110 THE EVE AND ITS C4.RE. 
 
 the proper fitting of spectacles and glasses 
 requires the combined skill of both the phy- 
 sician and the optician, and the one will be 
 sadly crippled, without the intelligent aid 
 and co-operation of the other. 
 
 One of the most important questions per- 
 tinent to this chapter is that of light. This 
 may seem a matter that can be easily 
 managed, but he who entertains such a 
 sentiment has but little knowledge of the 
 unfortunate circumstances under which a 
 large proportion of the human race work. 
 To say nothing of the improper lighting of 
 schools, which will be referred to in the last 
 chapter, it will only be necessary to remind 
 the optimist of the immense army of people 
 who work at home — in inside court-rooms, 
 by insufficient daylight by day, and by 
 wholly inadequate light at night. Again, 
 there is another class who continue to read 
 after twilight has arrived, and when illumi- 
 nation has become feeble. Again, there are 
 others who read or work by one or two gas- 
 
THE GENERAL CARE OF THE EYE. Ill 
 
 jets in a chandelier situated at a remote 
 distance from the page or cloth. Others 
 work perpetually in banks, office buildings, 
 etc., where good daylight never penetrates, 
 and still others, who not only read on trains 
 by daylight, and are subjected to the jolting 
 of the cars, producing a strain upon the 
 ciliary muscle, which continually establishes 
 new accommodative adjustments, but who 
 foolishly read by the dim and insufficient 
 overhead light that is usually furnished in 
 the cars of most of our railways. If one 
 will or must read on the train at night, he 
 should endeavor to select a road amply 
 lighted by electricity in general and by 
 little incandescent lights in each section, as 
 may be found in the lines operated by the 
 Chicago, Milwaukee & St. Paul Railroad. 
 
 The best light is the diffuse natural light 
 of day, and the best artificial light is that 
 which most nearly approaches daylight. 
 Even daylight may be abused, or, at least, 
 it may be improperly used, for care must be 
 
112 THE EYE AND ITS CARE. 
 
 taken that it reaches the near object gazed at 
 in the right manner. For obvious reasons, 
 a desk should not be situated so that the 
 light comes directly into the face of the 
 worker ; neither should the light come from 
 behind the worker's back, as his body will 
 shade the page ; nor from the right side, as 
 his hand will do the same thing. The light 
 should come from the left side, so that it 
 may be ample and yet not shine directly in 
 the face, and so that it may strike the paper 
 (during the act of writing) without obstruc- 
 tion from the hand. In reading without a 
 desk, the individual should sit erect, with 
 the back held reasonably up, with the light 
 coming from the left side, as in this posi- 
 tion the best and most unobstructed illumi- 
 nation is obtained. These rules are equally 
 necessary and applicable when using the 
 eyes by means of artificial illumination. 
 
 Artificial light should be profuse, white, 
 and steady. Kerosene, gas, and electricity 
 are the principal sources of illumination 
 
THE GENERAL CARE OF THE EYE. 113 
 
 used at present, and it may be said that they 
 are all good, and perform admirable service, 
 if properly controlled. They should be 
 shaded by globes, colored white on the 
 inside, and preferably tinted green on the 
 outside. They should be placed in such a 
 position that they are brought sufficiently 
 near the individual to afibrd ample illumina- 
 tion. 
 
 The chief objection to the incandescent 
 light consists in an annoying and trying 
 shadow (emanating from the heated wire) 
 that is thrown upon the page beneath. 
 This, however, can fortunately be remedied 
 by the use of translucent globes. 
 
 Much of the print thrown upon the 
 market is extremely small, badly impressed, 
 and hence very injurious to the eyes. This 
 is usually found to be the case in sensational 
 papers and novels that are widely rea'd; 
 consequently, the evil effects are felt by a 
 large proportion of the population of the 
 reading world. Newspapers especially are 
 
 h 10* 
 
114 THE EYE AND ITS CARE. 
 
 poorly printed, and, as no other publications 
 are so. freely read, the effect upon the eyes 
 may be pernicious. 
 
 In choosing books too much care cannot 
 be bestowed upon the selection of large, clear 
 type, and, as almost everything worth read- 
 ing can be found well printed, cheap and 
 injurious publications should be eschewed. 
 
 The paper from which we read, or upon 
 which we write, is also of importance. A 
 dull-surfaced, slightly tinted paper is prefer- 
 able to white, and the best tints are delicate 
 shades of gray, neutral tint, or bluish-green. 
 
 A prolific source of eye-strain is reading 
 whilst the body is resting in a recumbent 
 position. Especially is this so during con- 
 valescence following a severe illness, when 
 the temptation is strong, but the general 
 and ocular systems are weak and unable 
 to stand even a limited amount of work. 
 Even in health, owing to the fact that 
 under such circumstances it is practically 
 impossible to hold a book in a favorable 
 
THE GENERAL CARE OF THE EYE. 115 
 
 position where the muscles of the eye will 
 not undergo excessive strain in accommo- 
 dating themselves to the abnormal posture, 
 such a practice is injurious. 
 
 Eyes are not infrequently injured by ex- 
 actions which would never be demanded of 
 any other organ of the body, they evidently 
 being regarded as untiring and exhaustless. 
 This is especially true after a physician has 
 been consulted and glasses procured. Pa- 
 tients appear to consider that after this has 
 been accomplished their ocular functions 
 should have the strength and endurance of 
 steel. It must never be forgotten that the 
 eye is a delicate and exceedingly complex 
 organ, and that, while it is long-suflfering, its 
 endurance has a limit, which, if pressed too 
 far, will rebel and precipitate the most dire- 
 ful consequences. Therefore, the eye should 
 be treated with judgment and forbearance, 
 and not be made to perform more than a fair 
 day's work. Such a resolution would sug- 
 gest occasionally resting the eyes during 
 
116 THE EYE AND ITS CARE. 
 
 working hours by looking from time to 
 time at distant objects througb a window, 
 or by changing occupations as often as may 
 be, — i.e., from reading to writing, and from 
 writing to some other form of employment. 
 Moreover, it must not be expected that after 
 using the eyes all day in an office or a store 
 they can be used the major part of the even- 
 ing at home. Yet many people persist in 
 these practices from year to year, and then 
 wonder what is the matter with their eyes, 
 and, if they consult a physician and pro- 
 cure lenses, they delight in telling him that 
 they have paid him a consulting fee for 
 nothing, and that his glasses are worthless. 
 
 It should always be borne in mind to hold 
 the book, page, sewing, etc., as far away from 
 the eye as is compatible" with good vision, as 
 the farther away such work is held, the less 
 the ciliary muscle is taxed for accommoda- 
 tion, and the less are the internal recti 
 muscles used for convergence. The natural 
 tendency is averse to this rule, but, if faith- 
 
THE GENERAL CARE OF THE EYE. 117 
 
 fully remembered, it will soon become second- 
 nature, and the greatest amount of eye-work 
 performed with the least amount of strain. 
 
 It is wise to use caution in passing sud- 
 denly from a very dark to a very light room, 
 and to avoid looking at any bright object, 
 such as the sun, an incandescent light, white 
 shining snow, etc., for a protracted time, 
 through fear of deleterious effects upon the 
 retina. 
 
 In concluding this chapter it may be well 
 to mention the fact that the general system 
 has much to do with the health of the eye. 
 He who considers that the eye is a little 
 kingdom set off by itself, with separate laws 
 and administration, wall make a grave mis- 
 take. Anything that is generally unhealthy 
 and debilitating can have a corresponding 
 effect upon the eye, and anything that con- 
 duces to health and vigor will assist in 
 maintaining ocular strength and vitality. 
 Let him, therefore, who wishes to keep his 
 eyes in a strong and useful condition, see 
 
118 THE EYE AND ITS CARE. 
 
 that his digestive and eliminative functions 
 are properly conducted ; that his body is not 
 poisoned with drugs, stimulants, etc. ; that 
 he takes an abundance of out-door exercise ; 
 that he has plenty of refreshing sleep, and 
 that he occasionally rests his mind and body 
 by a relaxing vacation. In short, let him 
 be sure that he is obeying sensible laws of 
 hygiene, for, by so doing, not only his 
 general health, but the usefulness of his 
 eyes will be best maintained. 
 
CHAPTEE V. 
 
 KEPRACTION IN SCHOOLS. 
 
 This is an age of prevention rather than 
 of cure. The greatest efforts are being made 
 to prevent disease, rather than cure it. Can 
 anything more distinctly exemplify the dis- 
 interestedness of the physician than his ear- 
 nest and unremitting efforts toward proph- 
 ylactic medicine? Reflect for a moment 
 upon the discovery of vaccination for small- 
 pox, and the vilification endured by its pro- 
 genitors and advocates. Note the active 
 work accomplished by the medical profes- 
 sion in all questions involving sanitary re- 
 form and hygiene. Observe the earnestness 
 of scientists as they endeavor to prevent the 
 existence of diphtheria, tuberculosis, cholera, 
 etc., by laboriously exhausting their very 
 lives over the microscope and test-tube. No 
 
 119 
 
120 THE EYE AND ITS CARE. 
 
 one can deny that the existence of disease is 
 more profitable to the physician than its ab- 
 sence; and yet the proudest member of our 
 profession is he who discovers a prophylactic 
 rather than a curative measure. 
 
 Along this line of thought one of the 
 greatest reforms may be indicated in any- 
 thing that establishes and preserves the 
 health of the coming generation. The 
 present generation is launched for good or 
 for evil, and, while relief to its necessities 
 is most urgent, it surely cannot compare 
 with procedures that are calculated to pro- 
 duce in our descendants a race of people 
 strong and vigorous in mind, body, and 
 heart. It is for this now well-recognized 
 principle that wise and thoughtful philan- 
 thropists are engaging, with accumulating 
 energy, in the establishment of kindergar- 
 tens. Sabbath- and mission-schools, gymna- 
 siums, etc. They recognize the superlative 
 importance of early training, and that the 
 most efficient method of dealing with igno- 
 
REFRACTION IN SCHOOLS. 121 
 
 ranee, vice, and disease is to emancipate the 
 race from their existence. 
 
 The paramount importance of proper and 
 well-regulated school-life becomes, there- 
 fore, clearly apparent, and educators should 
 appreciate that in the sacred and responsible 
 position occupied by them, it is their duty 
 carefully to guard the body as well as the 
 mind of the youthful generation that may 
 be intrusted to their charge. 
 
 Without doubt many of the most distress- 
 ing diseases that are incident to human ex- 
 istence can trace their origin to the school- 
 life of the sufferer. Admittins; that such 
 pathologic changes are not invariably the 
 primary and direct offspring of improper 
 school existence, but may be the result 
 of the submission of an already vitiated 
 and hereditarily changed constitution to 
 improperly-constructed and badly-managed 
 school-buildings and school-life, we cannot, 
 even then, as citizens, advisers, and educa- 
 tors, shirk the responsibility. The ten- 
 
 T 11 
 
122 THE EYE AND ITS CARE. 
 
 dency of modern civilization leads toward 
 education and progress, and such develop- 
 ment should be encouraged. Such advan- 
 tages are shared by the rich and the poor, 
 by the young and the old, the healthy and 
 the sickly, by those whose ancestors were 
 blessed with vigorous minds and bodies, and 
 by those who can only gaze retrospectively 
 at a line of antecedents that were cursed by 
 the presence of dissipation and disease. 
 
 Admitting the existence and operation of 
 a law requiring a proper medical certificate 
 before admission can be obtained to the 
 school, there would still be a large per- 
 centage of scholars who, apparently healthy 
 but burdened by unfortunate inherited ten- 
 dencies, are capable of development under 
 improper and vitiated circumstances. The 
 responsibility of the present generation to 
 the coming one regarding school-life is, there- 
 fore, enormous, and involves such questions 
 as the location of school-buildings, with ref- 
 erence to air, space, and drainage ; the con- 
 
REFRACTION IN SCHOOLS. ] 23 
 
 struction of the building itself with regard 
 to window space and the direction of light ; 
 proper ventilation, plumbing, and drainage ; 
 the necessity for good and sufficient artificial 
 illumination ; the withdrawal of the ten- 
 dency towards overcrowding ; the necessity 
 for medical sanction before admittance to 
 schools may be obtained ; the use of proper 
 drinking-water ; the provision of separate 
 basins, towels, and soap, which is an un- 
 questioned source of contagion, especially 
 of an ocular nature ; the construction of 
 desks of different sizes for different ages, 
 so that the pupil may firmly plant his feet 
 on the floor, and always occupy the same 
 relative position to his desk ; the construc- 
 tion of desks that are of the proper slant 
 and height, and compel an upright position 
 of the body in reading and writing to be 
 taken, thus lessening the tendency to a 
 contracted chest and distorted spine, which 
 are prime factors in the production of con- 
 sumption and spinal disease ; the frequent 
 
124 THE EYE AND ITS CAKE. 
 
 intermission from studies and the change 
 from one study and occupation to another, 
 thus compelling a combined rest of eyes, 
 mind, and body ; the proper regulation of 
 the means of study, such as the distances 
 and color of blackboards, the color of slates, 
 the character of print, and the paper upon 
 which the type is printed ; the necessity for 
 vaccination ; the exclusion of contagious 
 diseases, and the execution of advisable 
 quarantine regulations and proper rules or 
 laws, intended to exercise a beneficent care 
 over the sight and eyes of the rising gen- 
 eration ; these, and many other subjects that 
 are pertinent to the matter under discussion, 
 must appeal to the consciences of those 
 having under their control the health and 
 morals of these young people in whose 
 hands must shortly be placed the future 
 of our country. The scope of this chapter 
 must necessarily preclude the possibility of 
 even a casual discussion of most of these 
 su})jects, and it therefore becomes necessary 
 
REFRACTION IN SCHOOLS. 125 
 
 to limit any remarks to observations that are 
 pertinent to the eye during modern school 
 existenco. 
 
 The deleterious influence of education and 
 intellectual advancement upon the human 
 organism can not be questioned. Not that 
 knowledge invariably goes hand in hand 
 with pliysical retrogression ; but uneducated 
 and untutored races are always superior 
 types of bodily development to those nations 
 tliat are renowned for an insatiable appetite 
 for knowledge. 
 
 The eye is no exception to the principle 
 involved in this statement. The eyes of a 
 people engiiged in rural and i)a.storal occu- 
 pations will demonstrate few, if any, errors 
 of refraction ; and in races of a barbaric or 
 semi-barbaric nature, such pathologic con- 
 ditions may be said to be positively un- 
 known. 
 
 Ramns, wdio made an examination of two 
 
 thousand Mexican school-children, found 
 
 only eighty-eight myopics, sixty hyperme- 
 11* 
 
126 THE EYE AND ITS CARE. 
 
 tropics, and ten astigmatics. He asserts 
 that pure Mexicans rarely show any errors 
 of refraction, and such deviations are almost 
 invariably found in the mixed races. If this 
 be compared with the statistics of the German 
 Empire, the home of the most highly intel- 
 lectual people in the world, it will be found 
 that the most advanced seats of learning 
 show that fifty per cent, of the pupils are 
 afflicted with myopia, to say nothing of 
 hypermetropia and astigmatism ; and, as if 
 this were not enough, one school in Vienna 
 has actually produced seventy-five per cent, 
 of myopic youths. 
 
 Unquestionably, therefore, school-life is 
 disastrously prolific of refractive errors, and 
 should be controlled with every means that 
 is possible by those having such matters in 
 charge. Moreover, while it cannot be denied 
 that myopia is found much more frequently 
 than hypermetropia and astigmatism, still the 
 existence of the latter conditions must not be 
 ignored, for they often exert an important 
 
REFRACTION IN SCHOOLS. 127 
 
 function in the health and character forma- 
 tion of the scholar. However, from the 
 very nature of myopia, and the possibility 
 of its extreme development under adverse 
 circumstances, combined with its influence 
 on heredity, it becomes inevitably the most 
 potential factor in the consideration of the 
 matter under discussion. 
 
 Statistics on this subject are enormous, as 
 from the time of Cohn's investigations in 
 the Breslau schools in 1865-66 to the pres- 
 ent time, more than two hundred thousand 
 pupils have been examined by competent 
 observers for statistical purposes. These in- 
 vestigations have occurred in all civilized 
 countries, and have been made under all 
 circumstances of age, sex, race, cranial for- 
 mation, health, heredity, intellectual ad- 
 vancement, and school architecture and 
 management. Many of these investigations 
 have been so arranged as to follow a cer- 
 tain number of pupils from class to class 
 and from school to school. They all point 
 
128 THE EYE AND ITS CARE. 
 
 to one inevitable conclusion, — viz., that 
 mental culture is obtained at the sacrifice of 
 ocular perfection, and that such imperfec- 
 tions are usually myopic in their nature. 
 
 It is unnecessary to detail the reports of 
 individual investigators, it being sufficient to 
 remember that such men as Cohn, Jager, 
 Riite, Erismann, Loring, Derby, Agnew, 
 Eisley, Hippel, Schmidt-Rimpler, and many 
 others of equal eminence have contributed 
 their time and ability to this work. Neither 
 can additional investigation materially in- 
 fluence the consensus of opinion on the 
 subject. 
 
 Certain facts have thus become established, 
 and, as they cannot be further proved, our 
 duty lies clearly in the line of an earnest 
 and concerted effort tending toward, at least, 
 a material mitigation of an existing evil. 
 These facts may be briefly mentioned as 
 follows : 
 
 The human eye at birth is normally de- 
 cidedly hypermetropic. Herman, who ex- 
 
REFRACTION IN SCHOOLS. 129 
 
 amined the refraction of one hundred and 
 ten children at about the age of three 
 months, found them all hypermetropic with- 
 out exception. Some deviations from these 
 statements are recorded by observers who 
 have detected myopia in very young infants 
 by the ophthalmoscope ; such instances are, 
 however, exceptional, and, while doubtless 
 true, are immaterial. 
 
 The eye which shows hypermetropia in 
 later life probably never reached the emme- 
 tropic line ; but the hypermetropic eye 
 which develops myopia, has at one time 
 assumed a condition of emmetropia, and 
 from this point its axis has elongated by 
 circumstances of heredity, health, and occu- 
 pation. 
 
 The statement that myopia is entirely an 
 acquired disease can hardly be substantiated 
 when we reflect upon the many instances, 
 observed by all ophthalmologists, where 
 myopia will run from father or mother to 
 every child in the family. Such cases can 
 
130 THE EYE AND ITS CARE. 
 
 not be coincidences, neithei* can they result 
 from certain peculiar environments. Dr. 
 Matais, of Angers, France, has examined 
 the families of three hundred and thirty 
 young myopic subjects, and has arrived at 
 the following conclusions : 1, the heredi- 
 tary influence of myopia is manifest ; 2, it 
 exists in two hundred and sixteen out of 
 three hundred and thirty families; 3, 
 hereditary myopia is characterized by its 
 early appearance, its comparatively rapid 
 development, and the high average of its 
 degree; 4, myopia is transmitted from the 
 father to the daughter eighty-six times out 
 of one hundred, and by the mother to the 
 eon seventy-nine times out of one hundred. 
 
 The same author believes that myopia is 
 inherited in sixty-five per cent, of all cases, 
 and that hereditary myopia is more sharply 
 defined than the acquired form. He also 
 says that it reaches a higher degree more 
 rapidly, and that its complications are more 
 frequent. 
 
REFRACTION IN SCHOOLS. 131 
 
 Dr. M. Kirchner, of Germany, who has 
 made exhaustive researches upon the sub- 
 ject, says that children are most liable to be 
 near-sighted when both parents are myopic, 
 less liable when the mother only is affected, 
 and least so when the father is the source of 
 transmission. Boys of myopic parentage are 
 twice and girls are four times as strongly 
 inclined to myopia as the offspring of non- 
 myopic parents. He thinks that girls are a 
 trifle more inclined to myopia than boys. 
 
 Schwalbe believes that the highest degrees 
 of myopia can invariably be traced to 
 heredity. 
 
 M. Francesque Sarcy, the well-known 
 French critic, whose intelligence and ve- 
 racity can not be questioned, has had some 
 interesting personal experience which he re- 
 ports in an interesting manner. He begins : 
 " I was born near-sighted ; many physicians 
 assert that persons are never born near- 
 sighted, but only become so. Science may 
 say what it pleases ; I was born myopic. 
 
132 THE EYE AND ITS CAME. 
 
 One day, prompted by a spirit of mischief, 
 I got hold of the big silver spectacles which 
 my father wore and clapped them on. Fifty 
 years have passed since then, but the sensa- 
 tion I experienced is keen and thrilling to 
 this day. I gave a cry of astonishment and 
 joy. Up to that moment I had seen the 
 leafy dome above me only as a thick green 
 cloth, through which no ray of sunlight 
 ever fell ; now, oh, wonder and delight ! 
 I saw that in this dome were many little 
 brilliant chinks ; that it was made of myriad 
 separate and distinct leaves, through whose 
 interstices the sunshine sifted, imparting to 
 the greenery a thousand forms of light and 
 shade. But what amazed me most, what en- 
 chanted me so that I cannot speak of it to 
 this day without emotion, was that I saw 
 suddenly, between the leaves and far, far 
 away beyond them, little glimpses of the 
 bright blue sky; I clapped my hands in 
 ecstasy, and was mad with astonishment and 
 delight." 
 
REFRACTION IN SCHOOLS. 133 
 
 Sarcy undoubtedly had congenital myopia, 
 and, in later life, he became temporarily 
 blind. In one eye he suffered a retinal de- 
 tachment, and in the other a cataract. The 
 latter eye was operated upon, and he ac- 
 quired better sight in it than ever before. 
 
 The existence, therefore, of absolutely 
 direct congenital myopia, while rare, can 
 hardly be doubted ; and the frequent trans- 
 mission of an inherited tendency in the 
 tissues of the eye, only requiring favorable 
 circumstances for development, is so evident 
 that argument is scarcely necessary. 
 
 The question of the influence of race and 
 nationality upon the development of myopia 
 is one of some importance, and has engaged, 
 without yet reaching a satisfactory settle- 
 ment, the attention of scientists for many 
 years. 
 
 In some races there is a greater proneness 
 to myopia than in others. Such tendencies, 
 however, can usually be traced to a greater 
 intellectual advancement, which necessarily 
 
 12 
 
134 THE EYE AND ITS CARE. 
 
 is indicative of greater eye-strain. Cohn, 
 for instance, when lie examined the Con- 
 stantinople schools found very little myopia. 
 This, he found, was owing to the small 
 amount of writing accomplished by the 
 scholars, and the manner in which it was 
 performed. The contrast between the eyes 
 of the Oriental and the German youth is, 
 therefore, very marked ; but the probability 
 is that the condition is due not to nativity 
 per se, or to cranial formation, as stated 
 by Stilling (who argues that a low, broad 
 orbit favors the development of myopia), 
 but that its absence is dependent upon in- 
 dolence and in appreciation of intellectual 
 advancement, with probable mental per- 
 versity. The view of Stilling can hardly 
 be maintained in view of the fact that 
 Pymska, of Dorpat, Russia, has carefully 
 examined three hundred and thirty-eight 
 scholars, mostly of Esthic nationality, and 
 has found only seventeen per cent, of my- 
 opes. Since these people have broad faces 
 
REFRACTION IN SCHOOLS. 135 
 
 and low orbits, and the proportion of myopes 
 is less in them than it is in the inhabitants 
 of western Europe, Stilling's theory can not 
 be wholly correct. Pymska, on his part, 
 feels that the development of myopia de- 
 pends upon the demands that are made 
 upon the eyes by modern civilization, and 
 that it is not dependent upon the form of 
 the cranium. 
 
 It has been said that the Jews have more 
 myopia than other people. There seems 
 to be no valid ground for this assumption 
 other than can be found in the fact that 
 Jewish vocations, the world over, are usually 
 those of shop-keepers, money-changers, etc., 
 which necessitate close application to books 
 and textures. In countries where the great 
 mass of the inhabitants turn to open-air em- 
 ployments and the Jew naturally gravitates 
 towards commercial life, no surprise need be 
 experienced if an examination of scholars 
 shows a wide discrepancy in the development 
 of myopia. Proof, however, fails to demon- 
 
136 THE EYE AND ITS CARE. 
 
 strate the same variance where Jew and 
 Christian are reared alike, and where in- 
 herited tendencies from one generation to 
 another can be estimated upon a basis of 
 similarity. 
 
 Dor says that "the further south you 
 go, the more normal eyes you find." This 
 statement may not be exactly correct, and 
 has been the subject of debate. Still, when 
 it is observed that in countries approaching 
 the equator, where life becomes progressively 
 indolent, application nears a minimum, the 
 noon-day and other siestas are frequent, and 
 general keenness and intelligence are lack- 
 ing, it becomes easy to believe that those 
 who are nearest the equator may more 
 nearly approach a condition of emmetropia 
 than those who reside further away. 
 
 Callan, of New York, has examined four 
 hundred and fifty-seven negro children, vary- 
 ing from five to nine years of age. In the 
 lower schools only about one and one-half 
 per cent, were myopic, and in the higher 
 
REFRAcrms xy schools. 137 
 
 aboot three and one-half per cent., making 
 the aTerage about two and one-half per cent. 
 In the primary schools lie fannd no myopia. 
 
 Fox has examined the scholars of tiie In- 
 dian schools of Carlisle, and has fennd only 
 an aTerage of two per cent, of myopia. 
 Ssaminadons have been made in Taiioos 
 countries, such as 3^orth and South America, 
 the British Isles, Germany. France, Switzer- 
 land. Sn^a. Italy, the Caucaaan and Ori- 
 @ital Countri^ Xorway and Sweden, Hon- 
 mania, etc The r^ult of these invi^tigations 
 may be stated, in the language of Cohn, to 
 be that " in the whole ciTilized world, in all 
 nalioi^ the number of the short-sighted in- 
 «3¥!as^ with the demands whidi their school 
 mak^ and &om da^ to cla^." 
 
 The percenfaige of school myopes in our 
 country, perha]^ does not exceed an average 
 of tweaity-five per cent., but it is oonstantly 
 inaeasing to eorr^pond with the require- 
 menis <rf an advancing civilization. This 
 oompazalxTe myopic in&equ^icy need not, 
 
 12* 
 
138 
 
 THE EYE AND ITS CARE. 
 
 however, detract from national pride, when 
 reflection is made upon the international 
 character of our citizens. Undoubtedly, 
 statistics taken from native-born Americans 
 would increase the percentage, and enable 
 us to refute the statement that there is on 
 the earth a more industrious and studious 
 race of people than in the United States of 
 America. 
 
 The coincident occurrence of advance in 
 classes and myopia is exceedingly interesting 
 and instructive, combined, as it is, with a 
 diminishing hyperopia in almost exactly re- 
 verse proportions. In this connection the 
 author can not refrain from quoting the 
 figures of Erismann, who, in 1871, ex- 
 amined four thousand three hundred and 
 sixty-eight St. Petersburg scholars. They 
 are as follows : 
 
 Class. 
 
 1. 
 
 2. 
 
 3. 
 
 4. 
 
 6. 
 
 6. 
 
 7. 
 
 9. 
 
 10. 
 
 Myopia .... 
 
 Hyperopia (Hy- 
 
 permetropia) , 
 
 13.6 
 67.8 
 
 15.8 
 55.6 
 
 22.4 
 60.5 
 
 30.7 
 41.3 
 
 38.4 
 34.7 
 
 41,3 
 34.5 
 
 42. 
 32.4 
 
 49.8 
 36.2 
 
 41.7 
 40. 
 
REFRACTION IN SCHOOLS. 139 
 
 The almost invariable increase of myopia 
 and the similar decrease of hyperopia from 
 class to class are striking in their accuracy. 
 The apparent discrepancies in the latter 
 classes may be due to the fact that as a 
 class approaches graduation, its number 
 usually diminishes, thus producing a dif- 
 ferent proportion in percentages. The table 
 of Erismann practically corresponds with 
 others prepared on this subject, and is an 
 impressive comment upon the effect of 
 modern civilization upon ocular refraction. 
 It also tends to confirm the belief that the 
 very cause which produces myopia dimin- 
 ishes hypermetropia. 
 
 If the physical condition of a myopic eye 
 is an elongated axis, the question may be 
 asked what are the abnormal circumstances 
 which produce such elongation, irrespective 
 of whether the eye has a natural myopic 
 tendency or not? Most text-books furnish 
 an explanation of this phenomenon, but the 
 most comprehensive that the author finds is 
 
140 THE EYE AND ITS CARE. 
 
 given by Fenner. I take the liberty to quote 
 bis words : " They (the scholars) usually sit 
 bending over a desk in a stooping position ; 
 the abdominal organs are compressed, pre- 
 venting the free return of the blood from 
 the head ; the insufficient illumination at 
 many schools and colleges necessitates the 
 bringing of the eyes very near the book, so 
 as to obtain a larger visual angle ; and, as 
 the book usually rests on a desk or table, 
 the head has to be bent over; this posture 
 produces an increased flow of blood to the 
 eyes, while the higher degree of convergence 
 necessary causes an increased pressure of the 
 lateral recti muscles on the equator of the 
 globe, thus increasing the intra-ocular press- 
 ure. The congestion of the fundus oculi 
 causes softening of the scleral tissue, which 
 gives way under the increased pressure, and 
 the organ is elongated backward (posterior 
 staphyloma) ; the other portions of the 
 sclerotic coat are supported by the broad 
 muscles. The retina is then pushed back- 
 
REFRACTION IN SCHOOLS. 141 
 
 ward, behind tlie focus of the dioptric appa- 
 ratus. When this condition once begins, all 
 the causes which first gave rise to it act with 
 increased force ; there is a greater stooping 
 posture necessary, because the eyes have to 
 be brought still nearer to the object ; an 
 increased convergence is demanded, and the 
 congestion of the fundus oculi increases ; 
 consequently, the softening processes pro- 
 gressively augment, causing the posterior 
 portion of the sclerotica to yield more and 
 more ; hence myopia is usually progressive, 
 particularly in the higher grades. There is 
 a greater tendency to the development of this 
 condition in youth from the causes above 
 mentioned, because then the scleral tissues 
 are softer, and consequently more yielding 
 than in later life. With the increase of 
 age this coat hardens, becomes firmer and 
 better able to withstand intra-ocular press- 
 ure ; hence it is rare that posterior staphy- 
 loma, giving rise to near-sightedness, begins 
 after the twentieth year of life." 
 
142 THE EYE AND ITS CARE. 
 
 Consideration must now be turned towards 
 those conditions of school-life which encour- 
 age and perpetuate the production and spread 
 of nayopia. The first item that claims atten- 
 tion is, that children should not be placed in 
 school at all unless their general health is 
 sufiicient to endure the strain. It is un- 
 necessary, and space does not permit the 
 author to impress upon physicians the im- 
 portance of this assertion, and the great in- 
 fluence exerted upon the eye by the general 
 condition of the patient. It is, however, 
 unquestionably imperative that medical men 
 should emphasize the truth to the laity, and 
 especially among those families committed to 
 their care. We are, at present, dependent 
 upon personal influence and the intelligence 
 of those people not medically educated, to 
 exclude from our schools those children who 
 are not physically prepared to enter. The 
 time should and undoubtedly will come 
 when every scholar will not only be com- 
 pelled to show a doctor's certificate before 
 
REFRACTION IN SCHOOLS. 143 
 
 entrance, but will find it necessary to pro- 
 duce a similar document at the beffinning of 
 every school year. 
 
 What, then, are the conditions of school- 
 life that directly aid in the encouragement 
 and perpetuation of myopia? First of all, 
 the building itself should be so constructed 
 as to present as few obstacles as possible to 
 the proper exercise of the ocular function, 
 and to give the pupils all the advantages 
 that are possible in the way of location, 
 space (inside and outside), heat, ventilation, 
 plumbing, general cleanliness, water, basins, 
 and soap. 
 
 The building should be lighted properly 
 and sufficiently, as there can be no question 
 that a paucity of illumination necessitates a 
 closer apposition of books, which, in its turn, 
 means increased convergence and an encour- 
 agement of myopia. Just seeks to contro- 
 vert this statement by claiming that there is 
 no decrease in myopia in the new and well- 
 lighted schools of Zittau, Saxony. The ex- 
 
144 THE EYE AND ITS CARE. 
 
 perience of others will scarcely support him 
 in his position. For instance, in Coburg, 
 Germany, two thousand three hundred and 
 twenty-three children were examined in 
 1874, and showed an average of twenty- 
 one per cent, of myopia. The same number 
 examined in 1877, after better lighting and 
 seating had been provided, showed an average 
 of only fifteen per cent, of myopia. De 
 Metz, of Antwerp, has found only about two 
 per cent, of myopia in well-lighted schools, 
 as contrasted with five per cent, in badly- 
 lighted schools. Other statistics, even more 
 striking than these, might be produced to 
 show the importance of proper illumination, 
 but it is scarcely necessary, as the principle 
 must commend itself to the mind of any one 
 who gives the subject even casual atten- 
 tion. 
 
 The light in the school-room should be 
 direct, and not the indirect illumination 
 from the walls of some adjoining building. 
 It must be constant. Dependence should 
 
REFRACTION IN SCHOOLS. 145 
 
 not be placed upon tlie immediate rays of 
 the sun, and, for this reason, the windows 
 should face the north. The most remote 
 portion of the room should be bright, even 
 on dark days, to the extent of receiving an 
 illumination that is equal to ten candle- 
 power. Every scholar should, from his 
 place, be able to see some portion of the 
 sky. Light should come from the left, and 
 as high above the scholars as the ceiling will 
 admit. The total window surface should 
 bear to the area of the floor a proportion 
 of one to five, and the panes should be as 
 large as possible. It would be better if 
 artificial illumination was never used, but 
 if it is, a profusion of incandescent electric 
 lights is the best substitute for daylight. 
 The lights should be amjDle in number. 
 They should be properly shaded, and 
 brought sufficiently close to the desk to 
 afford an abundant illumination. Such 
 artificial light is superior to gas, kerosene, 
 etc., as its color is whiter and it is capable 
 
 a k 13 
 
146 THE EYE AND ITS CARE. 
 
 of uniform distribution and concentration. 
 It does not heat or vitiate the atmosphere. 
 
 The question of the construction of seats 
 and desks is one of great importance. Seats 
 should permit each scholar to rest the feet 
 squarely upon the floor, thus favoring a nat- 
 ural and upright position ; for this purpose 
 it is necessary to provide seats of different 
 sizes for individual pupils, who should be 
 seated according to their height. The desks 
 should have comfortable backs. They must 
 correspond in size to the pupil, and have a 
 slightly slanting top. The tops should be 
 situated far enough away from the head of 
 the scholar (when seated in an upright posi- 
 tion) not to necessitate close approximation 
 of the page of a book to the eyes. Many 
 seats and desks are so poorly constructed 
 for the needs of the individual student as to 
 just allow the head of the patient to emerge 
 from the top of the desk, thus necessitating 
 an enormous convergence when attempts are 
 made to study. These defects are usually 
 
REFRACTION IN SCHOOLS. 147 
 
 observed in primary departments, where full- 
 sized desks are employed by very small pu- 
 pils. Strict rules are enunciated by Fuchs 
 and others as to the relation that should 
 exist between the desk and the seat. Fuchs 
 says that " the proper position is that in 
 which the shoulders and pelvis are parallel 
 with the edge of the desk, and the head up- 
 right or bent but slightly forward. As to 
 the construction of desks and seats, there 
 must be several sizes, to suit scholars of 
 various ages. The vertical distance between 
 seats and desks must be but little greater 
 than the distance between the elbow and 
 the ischial tuberosity. The edge of the 
 desk must overhang the seat about two 
 inches ; the scholar can then sit upright." 
 
 Rohe does not think it necessary for the 
 desk to overlap the seat, but says that " a 
 line dropped from the near edge of the desk 
 should strike the front edge of the seat." 
 
 In any event the object is, if possible, to 
 prevent stooping and to compel the scholar 
 
148 THE EYE AND ITS CARE. 
 
 to study in an upright position. Various 
 apj)aratuses have been constructed for the 
 purpose of forcing an erect attitude, but as 
 yet nothing satisfactory and practical has 
 been proposed. 
 
 Attention should be given to the distance 
 and location of blackboards, to prevent their 
 being placed at so great a distance from any 
 scholar as to necessitate a strain in order to 
 see, and also carefully to avoid a position 
 where rays of light will be reflected upon 
 their surface in such a manner as to obscure 
 the characters that are inscribed thereon. 
 Similar care should be given to the placing 
 of maps, from which scholars from time to 
 time are required to study. Some investiga- 
 tors believe in doing away with the black- 
 boards entirely, and substituting white sur- 
 faces and black crayons, they believing that 
 black writing on white background can be 
 read at a greater distance than the reverse. 
 In some schools the same plan has been 
 proposed and practised with slates ; white 
 
REFRACTION IN SCHOOLS. 149 
 
 slates and black pencils are used on account 
 of lessened reflection. Good results are 
 claimed. Owing to the glistening surface, 
 other investigators believe in not using 
 slates at all. They would substitute paper 
 and pencil or pen, the paper to possess a 
 non-glistening surface and to be thoroughly 
 opaque. 
 
 School-books should be of a size that can 
 be easily handled. The paper should be 
 reasonably thick, of good quality, and have 
 a dulled surface ; some authorities think 
 that yellow instead of white paper is to be 
 preferred. The Latin letters are best for 
 all kinds of reading, and it is certain that 
 if Germany would absolve itself from 
 nationalism sufficiently to declare an eman- 
 cipation from its miserable type, there would 
 be less myopia in that country. The letters 
 should be well printed, and they should be 
 clear, distinct, and large. Cohn insists that 
 all books should be prohibited from schools 
 in which a smaller type than long primer, 
 
 IS* 
 
150 THE EYE AND ITS CARE. 
 
 a less interval between the lines than one- 
 tenth of an inch, a longer line than four 
 and one-half inches, and containing more 
 than sixty letters to a line, are used. 
 
 The question of erect or slanting hand- 
 writing is one that is much agitated at 
 present. In the first place, Ellinger opposes 
 the practice of inclining the copy-book to 
 the right instead of straight ahead, feeling 
 sure that it favors the development of 
 myopia. However this may be, it is certain 
 that there is variety in the opinions that are 
 expressed relative to the preference as to 
 erect or slanting writing, with the drift of 
 sentiment favoring the former. Berlin favors 
 the inclined writing, but he appears to be 
 occupying a somewhat isolated position. 
 Shubert, Manz, Konigshoefer, Seggel, and 
 others endorse vertical handwriting. It is 
 felt that the oblique system favors myopia 
 by an unnatural position of the head, and 
 by the fact that upright writing is usually 
 clearer and more easily read than the ob- 
 
REFRACTION IN SCHOOLS. 151 
 
 lique. As continuous work is detrimental 
 to the health of the eye, this should be 
 avoided in the school by often changing 
 from one occupation to the other, as from 
 desk work to recitations, and by frequent 
 intermissions, during which time the rooms 
 should be thoroughly aired. Matais claims 
 that at the Military Prytanaeum and at the 
 School of Arts and Industry, at Angers, 
 myopia is relatively rare, although the 
 hygiene is not better than in the colleges. 
 He claims that this exemption is dependent 
 upon the frequent interruptions in work, 
 which consist in manual work, games, and 
 active exercise. 
 
 Unquestionably, much harm is done by 
 indiscretion in ocular service at home. 
 Granting that our directors performed an 
 elimination of all existing school evils rela- 
 tive to ocular hygiene, there would still re- 
 main an element in the abuses at home that is 
 beyond their control. Here there is a mere 
 repetition of all the evils that have already 
 
152 THE EYE AND ITS CARE. 
 
 been enumerated as occurring in school-life. 
 Here provisions are not usually made as to 
 proper desks and seats, light, and interrup- 
 tions in work. Children are allowed much 
 latitude as to what, when, and how they 
 read. Poorly-printed novels are absorbed 
 before and after going to bed. They are 
 read whilst the child is either sitting or 
 reclining. Any light that happens to be 
 convenient is used. In view of such in- 
 evitable abuses, especially among the poor 
 and ignorant, the warfare against myopia 
 is not of an encouraging character. This 
 should not, however, absolve us from press- 
 ing the battle whenever an opportunity pre- 
 sents. If perfection cannot be obtained, 
 progress can at least be made, and much 
 benefit will accrue from educating school- 
 directors, teachers, and the laity, who can, in 
 their turn, perform their part in disseminat- 
 ing knowledge upon the subject among those 
 who are less informed than themselves. 
 As a rule, children are sent to school too 
 
REFRACTION IN SCHOOLS. 153 
 
 early in life, and too little attention is paid 
 to the individual adaptability of the child 
 for school-life and its requirements. Again, 
 it is felt that a child must go to school at a 
 certain age, irrespective of his physical con- 
 dition, and such generalizing of educational 
 methods is frequently followed by exceed- 
 ingly detrimental results. 
 
 Children often go into kindergartens with 
 perfect refraction, and acquire myopia even 
 before entering the primary department of 
 a public school. The use of the eyes at a 
 tender age, especially in those children who 
 inherit a myopic, tuberculous, or scrofulous 
 tendency, is exceedingly hazardous. Their 
 tissues are soft, pliable, and yielding, par- 
 ticularly where such parental predispositions 
 exist. In such cases the confinement and 
 bad school hygiene, coupled with the desk- 
 and eye-work that are incident to school- 
 life, unquestionably form a combination of 
 circumstances that conspicuously favor the 
 development of myopia. 
 
154 THE EYE AND ITS CARE. 
 
 Myopia is rare before the eighth year of 
 life. It usually begins about the tenth year 
 and reaches its maximum at about the twen- 
 tieth year. As statistics show that the less 
 educated the nation, the more cases of normal 
 refraction are found, it must be self-evident 
 that these early years of life should be 
 guarded from the refining influences of in- 
 tellectual advancement as much as possible. 
 In other words, it should be borne in mind 
 that it is better to devote the years of youth 
 to laying the foundation of a strong consti- 
 tution, and that the rural child, raised upon 
 the farm, with practically no advanced 
 educational advantages until about the fif- 
 teenth year, often far outstrips his city rival, 
 whose life has been spent in kindergartens 
 and other graded schools. 
 
 The question as to what shall be done with 
 these children of perverted tendencies is one 
 of great importance. Shall they be sent to 
 the public school at the average age, to be 
 thrown into the common receptacle, to be 
 
REFRACTION IN SCHOOLS. 155 
 
 assigned the same lessons, and to be treated 
 in exactly the same way as the youth of 
 untainted health and robust constitution? 
 Common humanity unhesitatingly answers 
 in the negative. Such children should 
 rather be allowed to spend their lives in 
 the open air, with a judicious intermixture 
 of properly-assigned manual labor. Their 
 mental education should be postponed, and 
 every effort made to mitigate the unfortu- 
 nate tendencies of birth, by inducing a 
 physical rather than an intellectual life ; 
 one that should be preferably spent in the 
 country, where the air is good and the sur- 
 roundings are healthy. Systematic study 
 should not be begun until about the fif- 
 teenth or sixteenth year, after the body is 
 thus strengthened, and the ocular tissues 
 have grown firm and better able to resist 
 the encroachments of myopia. Even then 
 it will be better to teach the child at home, 
 or at some private institution, where its 
 student life can be better controlled. 
 
156 THE EYE AND ITS CARE. 
 
 It may be urged that sucli advantages are 
 only for the wealthy, and the question may- 
 be asked as to what must become of the 
 myope situated in humbler circumstances. 
 This query may be exceedingly pertinent, 
 but it must not be forgotten that the com- 
 pensations of life are somewhat evenly di- 
 vided, and that myopia is much more prone 
 to occur among the wealthy and intellectual 
 than among the poor and illiterate. Conse- 
 quently the necessity for such restrictions 
 in the early career of our youth will not so 
 often be required of the latter class. 
 
 Can myopia be cured ? This is a question 
 which is forced upon us, and must be con- 
 servatively answered. When once thor- 
 oughly established, and decided organic 
 changes have occurred, the probability is 
 that with our present knowledge of the 
 disease it can not be cured ; it can only be 
 alleviated. That by improved school hy- 
 giene, education of the laity, and careful 
 and uniform correction of refractive errors, 
 
REFRACTION IN SCHOOLS. 157 
 
 it is susceptible of material mitigation in a 
 community is amply proved by the careful 
 and painstaking investigations of Risley 
 and his associates in Philadel|)hia. It must 
 ever be borne in mind, however, that the 
 only reasonable hope for even partial eman- 
 cipation must necessarily rest in projohylaxis, 
 school hygiene, an intelligent co-operation 
 of the laity, and a proper correction of the 
 refractive error by suitably adjusted glasses. 
 While the subject of myopia in youths is 
 of signal importance, we must not lose sight 
 of another class of cases, — viz., the hyper- 
 metropes and astigmatics. These, it is true, 
 do not possess that element of danger to 
 sight found in malignant myopia, where the 
 disease marches on to posterior staphyloma,* 
 detached retina, and blindness ; but it does 
 mean much in the possible intellectual prog- 
 
 * Posterior staphyloma ia a posterior bulging 
 backward of the eye, found in extreme myopia. 
 In this disease the retina sometimes becomes de- 
 tached from the underlying choroid. 
 14 
 
158 THE EYE AND ITS CARE. 
 
 ress of the individual, and the attainments 
 of those heights of knowledge that are ap- 
 parently demanded by modern civilization. 
 
 The myopic eye is often a strong eye, 
 capable of performing much work at short 
 range ; but the hypermetropic or astigmatic 
 eye possesses attributes that are quite the 
 reverse, — viz., comparative ease in distant 
 vision, but great inconvenience during close 
 work. The hypermetropic or astigmatic 
 youth suffers from symptoms, such as head-r 
 ache, eye-tire, etc., generally classed under 
 the one term, asthenopia, and which have 
 their principal origin in an overtaxed ciliary 
 muscle. He goes to school, but takes no 
 interest in his studies; he is called idle 
 because he gives so little attention to his 
 books ; he is classed as stupid from never 
 knowing his lessons; he is thought to be a 
 complainer because he frequently has head- 
 aches ; he taxes the patience of both the 
 teacher and the parent, whose wonder is 
 excited when the inane, idle, stupid, fault- 
 
REFRACTION IN SCHOOLS. 159 
 
 finding child is transformed into a wide- 
 awake, industrious, healthy student by the 
 aid of a properly-adjusted pair of spectacles. 
 This is an experience that is common to 
 every teacher and physician, and the fre- 
 quency of its occurrence should be an in- 
 centive to active efforts for relief upon the 
 part of those from whom relief is expected 
 to come. An important matter of this 
 nature can not with safety be left to the 
 laity to settle. Some means must be de- 
 vised by which an ocular examination of 
 each scholar shall be a requisite for entrance 
 into a school, and by which a repetition of 
 such an examination must be made at stated 
 intervals during the scholar's school-life. 
 Opinions differ as to the necessary fre- 
 quency of such tests. Some feel that they 
 should be held every six months, and others 
 that an annual examination is sufficient. 
 Either plan would be an improvement upon 
 the present system, where nothing of the 
 kind is required. 
 
160 THE EYE AND ITS CARE. 
 
 In addition to this, provision must be 
 made by which children who shall be ad- 
 judged to possess defective eyes shall be 
 required to produce a proper certificate from 
 a reputable physician before admission to 
 the school is permitted. Such a specification 
 would exclude work so commonly done by 
 opticians, jewelry and department stores, etc. 
 
 One method would be to have a competent 
 physician appointed by the proper authori- 
 ties, whose duties should be to pass upon the 
 eligibility of all scholars, both upon entrance 
 examination and at stated intervals. This 
 would, however, be open to certain objec- 
 tions. It would involve a salary, which the 
 different boards might be unwilling to pay, 
 and would inevitably impair the efficiency 
 of such a law by a degeneration into political 
 jobbery. Besides this, the appointee would 
 undoubtedly be distasteful to many pupils or 
 parents, which would constitute an obstruc- 
 tion to harmony and an embarrassment to the 
 examiner. 
 
REFRACTION IN SCHOOLS. 161 
 
 In case such a method is deemed inadvisa- 
 ble, another plan would be to require of each 
 pupil a proper certificate from a reputable 
 physician, stating the ocular condition of 
 the applicant, with recommendations for 
 relief if necessary. This, again, would be 
 opposed by the people as compelling an 
 ocular examination where it is perhaps un- 
 necessary, thus incurring a useless expense 
 to parents or guardians. It is true that a 
 combination of both of these methods might 
 be adopted, and a law passed requiring that 
 each pupil shall pass an ocular examination 
 by a physician, leaving it optional, however, 
 with the parent or guardian whether the 
 child shall be passed upon by the school- 
 examiner, or taken to a physician of recog- 
 nized standing whom they themselves shall 
 select. This would be a compromise measure^ 
 but would still be open, in mitigated form, 
 to the combined objections of both proced- 
 ures. 
 
 There is another method of dealing with 
 
 I 14* 
 
162 THE EYE AND ITS CARE. 
 
 the subject, elsewhere proposed by the author, 
 which may not be considered sufficiently 
 stringent and scientific for enthusiasts on the 
 matter, but which he believes to be all that 
 can be accomplished at present, and may 
 pave the way for something more energetic 
 in the future. It can be executed at practi- 
 cally no expense to our school treasury, will 
 but seldom cause useless expense to parents 
 and guardians, can be universally applied, 
 and, if thoroughly accomplished, will give 
 general satisfaction. The idea is simply to 
 have a physician of recognized ability de- 
 liver a lecture or talk on the subject to the 
 principals of the city schools once a year, 
 just preceding the opening of the schools. 
 This talk should include plain and compre- 
 hensive remarks upon the anatomy and 
 physiology of the eye, refraction, and how 
 to use, but not abuse, the eyes in school- and 
 home-work. It should also be arranged to 
 instruct the principals how to test the eyes, 
 in accordance with some scheme similar to 
 
REFRACTION IN SCHOOLS. 163 
 
 the subjoined. Besides this, printed direc- 
 tions for testing the eyes, reading something 
 like the accompanying, should be given to 
 each principal. 
 
 INSTETJCTIONS FOE EYE EXAMINATIONS. 
 
 The examination should be made privately 
 and singly, in a room set apart from the 
 general school session. 
 
 A' card of Snellen's Test Types is to be 
 placed on the wall in a good light ; the face 
 of the card should not be covered by glass. 
 
 The line marked xx (20) should be seen 
 at twenty feet, therefore the pupil is to be 
 placed twenty feet away from the card. 
 
 Each eye should be examined separately. 
 
 A card should be held over one eye while 
 the other is being examined. 
 
 The covered eye should not be pressed 
 upon, as the pressure might induce an 
 incorrect examination. 
 
 The pupil should begin at the top of the 
 test-card, and read aloud down as far as he 
 
164 THE EYE AND ITS CARE. 
 
 can ; first with one eye, and then with the 
 other. 
 
 If the pupil can read xx (20) test-type 
 with each eye, and does not, upon inquiry, 
 complain of tired and painful eyes or head- 
 ache, he may be admitted to school ; but if 
 he can not read xx (20) test-type with both 
 eyes, or complains of tired and painful eyes 
 or headache, he should be sent home with a 
 card of information, such as the accompany- 
 ing, to the parent or guardian :. 
 
 ,18— 
 
 Dear , — Tour son, , has been exam- 
 ined by me this day as to the condition of his eyes. 
 
 I believe it to be advisable for him to consult a 
 physician of recognized standing, from whom he 
 should bring a certificate stating that it is wise for 
 him to continue his studies. 
 
 Eespectfully, 
 
 Principal of School. 
 
 The test-cards, the printed cards of in- 
 struction for principals, and the blanks to 
 
REFRACTION IN SCHOOLS. 165 
 
 be sent to parents or guardians would all cost 
 but little ; hence the expense would be un- 
 objectionable. Besides, the test is so simple 
 and so easily accomplished that any princi- 
 pal of a school could soon master it and ex- 
 amine the pupils with such ease and rapidity 
 that a large school could be tested in a very 
 few days. If systematic arrangements were 
 made, an average of two or three minutes 
 to each pupil would be all the time that 
 would be necessary. 
 
 The author is aware that such an exam- 
 ination is not ideal and is open to objections ; 
 but he believes that it is better than nothing ; 
 that it is fairly sufficient ; that it can hardly 
 antagonize interested parties ; that it can not 
 savor of medical favoritism ; that it involves 
 practically no expense; and that it is so 
 simple and practical that it commends itself 
 to all. 
 
II^DEX. 
 
 Accommodation 75, 77 
 
 muscle of 20, 42, 44 
 
 Agnew 128 
 
 Albino 21, 22 
 
 America, Nortli 137 
 
 South 137 
 
 Angers 151 
 
 Antwerp 144 
 
 Artists 102 
 
 Asthenopia 78, 158 
 
 muscular 82 
 
 Astigmatism 69, 88, 97, 126, 157 
 
 compound hypermetropic 91, 92 
 
 compound myopic 90, 92 
 
 mixed ' 91, 92 
 
 simple 90 
 
 simple hypermetropic 92 
 
 simple myopic 92 
 
 Asylums, blind 104 
 
 Atropine 28, 97 
 
 Axis of vision 33 
 
 Belladonna 28, 97 
 
 Berlin 150 
 
 Blackboards 124, 148 
 
 Blindness 30, 157 
 
 Book, copy- 150 
 
 Brain 29 
 
 167 
 
168 INDEX. 
 
 Breslau 127 
 
 British Isles 137 
 
 Callan 136 
 
 Camera 31 
 
 Canthus, external 48, 50, 55 
 
 internal 48, 50, 55 
 
 Capsule of Bonnet 11 
 
 of Tenon 11, 12 
 
 Cartilage, tarsal 52, 54 
 
 Cataract 39 
 
 Caucasian 21, 137 
 
 Certificate, doctor's 142 
 
 medical 122 
 
 Chamber, anterior 38, 40 
 
 Chicago, Milwaukee, and St. Paul K.K Ill 
 
 Children, Mexican school 125 
 
 Negro 136 
 
 Choroid 18, 19, 20, 26, 31 
 
 Ciliary hody 20, 29, 41 
 
 muscle 20, 42, 44, 75, 77, 79, 97 
 
 or suspensory ligament 41, 42, 44 
 
 process 19 
 
 Coburg 144 
 
 Cohn 127, 128, 134, 137, 149 
 
 Coloring matter 21 
 
 Conjunctiva 13, 49, 50 
 
 Conjunctivitis of the new-born 104 
 
 Constantinople 134 
 
 Consumption 123 
 
 Contagious diseases 124 
 
 Cornea 16, 17, 18, 38, 39, 40 
 
 Daylight Ill 
 
 De Metz 144 
 
 Department stores 160 
 
 Derby 128 
 
INDEX. 169 
 
 Desk 140 
 
 Diplopia 37 
 
 Dor 136 
 
 Duet, nasal 56 
 
 Dura mater 16, 29 
 
 Educators 121 
 
 Ellinger 150 
 
 Emmetropia 74 
 
 Equator 136 
 
 Erismann 128, 138 
 
 Examination, ocular 161 
 
 instructions for 163 
 
 Eyeball 12, 13, 14, 29 
 
 Eyebrows 46 
 
 Eye-glasses 99, 107 
 
 Eyelashes 48 
 
 Eyelids 47 
 
 Eye-strain 114 
 
 Eye-tire 158 
 
 Feuner 140 
 
 Fissure, palpebral 47 
 
 Eocus 64, 65 
 
 Eoramen, optic 9, 12, 29, 53 
 
 Eox 187 
 
 Frames, gold 108 
 
 steel 108 
 
 France 137 
 
 Franklin, Benjamin 101 
 
 Fuchs 147 
 
 Gas 112 
 
 Germans 126, 134 
 
 Germany 137 
 
 Glands, Meibomian 53 
 
 Glasses 94 
 
 H 15 
 
170 INDEX. 
 
 Glasses, bi-focal 101 
 
 pebble 102 
 
 skeleton 100 
 
 smoke 103 
 
 Granulated lids 50 
 
 Guardians 162 
 
 Gymnasiums 120 
 
 Hairs, wild 49 
 
 Handwriting 150 
 
 Headaches 78, 158 
 
 Helmholtz 24 
 
 Hereditary 130 
 
 Herman 128 
 
 Hippel 128 
 
 Home abuses 151 
 
 Humor, aqueous 31, 38, 39, 40 
 
 vitreous 31, 38, 42, 45, 46 
 
 Hypermetropia 70, 74, 77, 97, 126, 129, 157 
 
 Illumination 28 
 
 artificial 112, 145 
 
 Iris 20, 21, 22, 38 
 
 Italy 137 
 
 Jager 128 
 
 Jewelry stores 160 
 
 Jews 135 
 
 Kerosene 112 
 
 Kindergartens 120, 153 
 
 Kirchner 131 
 
 Konigshoefer 150 
 
 Lachrymal apparatus 54 
 
 canal 66 
 
 duct 54 
 
INDEX. 171 
 
 Lachrymal gland 54 
 
 sac 56 
 
 Lens, concave 64, 65 
 
 convex 63 
 
 crystalline 38, 39, 41 
 
 crystalline, capsule of 41, 44 
 
 cylindrical 67, 69, 94 
 
 spherical 94 
 
 Levator palpebrarum 63 
 
 Light 70, 110 
 
 electric 112, 113, 145 
 
 " Long-sight" 80 
 
 Loring 128 
 
 Macbeth 32 
 
 Macula 33 
 
 Manz 150 
 
 Matais 130, 151 
 
 Membrane, hyaline 45 
 
 Microscope 43 
 
 Muscles 13, 37 
 
 Musicians 102 
 
 Myopia 30, 74, 80, 106, 126, 129 
 
 malignant 157 
 
 " Near-sight" 80 
 
 Nerve, optic 9, 16, 19, 26, 29 
 
 Newspapers 113 
 
 Norway 137 
 
 Novels 152 
 
 Oblique, inferior 12 
 
 superior 12 
 
 Opera-glass 43 
 
 Ophthalmia neonatorum 104 
 
 Ophthalmoscope 24, 25 
 
 Opticians 109, 160 
 
172 INDEX. 
 
 Orbicularis palpebrarum 53 
 
 Orbit 12 
 
 Orbital edge 12 
 
 Oriental 134, 137 
 
 Parents 162 
 
 Philadelphia 157 
 
 Presbyopia 81, 83, 92 
 
 Principals 162, 163, 164, 165 
 
 Print 124 
 
 Prism 62, 63, 64 
 
 Pulley 12 
 
 Pupil 21, 22, 23, 29, 31 
 
 Pymska 134 
 
 Eamas 125 
 
 Kays 57, 58, 59, 61 
 
 Eectus, external 11, 12, 13 
 
 inferior 11, 12, 13 
 
 internal 11, 13 
 
 superior 11, 12, 13 
 
 Eefraction 71, 94 
 
 Eegulations, quarantine 124 
 
 Ketina 29, 80, 31, 32, 33, 72, 74 
 
 Ketinal detachment 30 
 
 Bisley 128, 157 
 
 Kobe 147 
 
 Eoumania 137 
 
 Russia 137 
 
 Elite 128 
 
 Sarcy 131 
 
 Sehmidt-Eimpler 128 
 
 School board 160 
 
 books 149 
 
 buildings 121, 143 
 
 life 121 
 
INDEX. 173 
 
 School lighting 143 
 
 seats and desks 146 
 
 treasury , 162 
 
 Schools, graded 154 
 
 Indian 137 
 
 mission 120 
 
 Sabbath 120 
 
 Schwalbe 131 
 
 Sclerotic 14, 19, 29, 31 
 
 Seggel 150 
 
 Sewing 116 
 
 Shubert 150 
 
 Siesta 186 
 
 Slates 124, 149 
 
 Snellen's test-type 86, 163 
 
 Socket 9 
 
 Sore-eye 50 
 
 Spectacles 99 
 
 Spinal disease 123 
 
 Staphyloma, posterior 141, 157 
 
 Stilling 134 
 
 St. Petersburg 138 
 
 Strabismus or " cross-eye" 13,37,106 
 
 Sweden 137 
 
 Switzerland 187 
 
 Teacher 159 
 
 Telescope 43 
 
 Test-card 96 
 
 Test-type 94 
 
 Tract, nasal 20 
 
 Type 149 
 
 Vaccination 124 
 
 Vienna 126 
 
 Vision, axis of 33 
 
 far-point of 86 
 
 15* 
 
174 INDEX. 
 
 Vision, monocular 85 
 
 near-point of 86 
 
 "Wall-eye 13 
 
 White of the eye 15 
 
 "Window surface 146 
 
 Yellow spot 33, 34, 36 
 
 Zittau 143 
 
 THE END. 
 
■SSr^Tl.B'Kni