SAUNDERS' MEDICAL HAND-ATLASES. «o^-o« The series of books included under this title are authorized translations into English of the world-famous Lehmann Medicinische Handatlanten, which for scientific accuracy, pictorial beauty, compactness, and cheapness surpass any similar volumes' ever published. Each vojume contains from 50 to 100 colored plates, besides numer- ous illustrations in the text. The colored plates have been executed by the most skilful German lithographers, in some cases more than twenty im- pressions being required to obtain the desired result. Each plate is accom- panied by a full and appropriate description, and each book contains a con- densed but adequate outline of the subject to which it is devoted. One of the most valuable features of these atlases is that they offer a ready and satisfactory substitute for clinical observation. Such ob- servation, of course, is available only to the residents in large medical centers; and even then the requisite variety is seen only after long years of routine hospital work. To those unable to attend important clinics these books will be absolutely indispensable, as presenting in a complete and con- venient form the most accurate reproductions of clinical work, interpreted by the most competent of clinical teachers. While appreciating the value of such colored plates, the profession has heretofore been practically debarred from purchasing similar works because of their extremely high price, made necessary by a limited sale and an enormous expense of production. Now, however, by reason of their pro- jected universal translation and reproduction, affording international dis- tribution, the publishers have been enabled to secure for these atlases the best artistic and professional talent, to produce them in the most elegant style, and yet to offer them at a price heretofore unapproached in cheapness. The great success of the undertaking is demonstrated by the fact that the volumes have already appeared in nine different languages — German, English, French, Italian, Russian, Spanish, Danish, Swedish, and Hungarian. The same careful and competent editorial supervision has been secured in the English edition a> in the originals. The translations have been edited by the leading American specialists in the different sub- jects. The volumes are of a uniform and convenient size (5 x 7^ inches), and are substantially bound in cloth. (For List of Books, Prices, etc. see back coverJ Pamphlet containing specimens of the Colored Plates sent free on application. QL> ' ATLAS OF THE EXTERNAL DISEASES OF THE EYE INCLUDING A BRIEF TREATISE ON THE PATHOLOGY AND TREATMENT BY PROF. DR. O. HAAB of Zurich AUTHORIZED TRANSLATION FROM THE GERMAN EDITED BY G. E. deSCHWEINITZ, A.M., M. D. Professor of Ophthalmology in the Jefferson Medical College, Philadelphia Consulting Ophthalmologist to the Philadelphia Polyclinic; Ophthal- mic Surgeon to the Philadelphia Hospital and to the Ortho- pedic Hospital and Infirmary for Nervous Diseases. With 76 Colored Plates and 6 Engravings PHILADELPHIA W. B. SAUNDERS 925 Walnut Street 1899 Copyright, 1899, By W. B. SAUNDERS. ELECTROTYPED.BY PRESS OF WESTCOTT & THOMSON, PHILADA, W. B, SAUNDERS. PHILADA. VjIaJ 100 EDITOR'S PREFACE This volume forms an excellent companion-book to Professor Haab's " Atlas of Ophthalmoscopy and Oph- thalmoscopic Diagnosis," and is exactly what might be expected from an author of such wide clinical experience and trained observation. Beginning with the examina- tion of the eye — that is, with functional testing — the student is easily and gradually led from one examination to another, and made familiar with the best methods of investigating the organ of sight for the detection of mor- bid processes. Following this are the chapters on dis- eases of the eye, the most important of which are clearly described and the best therapeutic measures briefly re- corded. As Professor Haab himself has pointed out, there is much difficulty in portraying in colors the ex- ternal diseases of the eye ; but, in spite of this, he has succeeded in furnishing an admirable series of plates, to each one of which a brief clinical history is appended, which thoroughly illustrate the text. Perhaps it is not too much to say that while one is reading this manual he distinctly feels that he is in the atmosphere of a large clinic. 8 EDITOR'S PREFACE. The Editor has compared the translation with the origi- nal, and can testify that although it is not precisely literal, it is none the less singularly accurate, and always conveys with faithfulness the author's meaning. Occa- sional editorial comments are placed in brackets. It is hoped that this book will prove of use not only to physi- cians whose opportunities do not permit them to see large numbers of external ocular disorders, but also to teachers and students of ophthalmology. PREFACE At the request of the publisher I undertook the task of preparing the present atlas and accompanying treatise, although at the time I fully appreciated how difficult it is to give a faithful reproduction of the external diseases of the eye. But after seeing the work of Mr. J. Fink, of Munich, at my clinic last summer, I became convinced of his ability to accomplish anything within the range of the illustrator's art. With the exception of a few pictures which I already had in my collection, the illustrations were all painted from nature, the artist utilizing any suitable cases that happened to come to the clinic. We therefore had to depend largely on chance for a complete collection of suitable clinical pictures ; but we were fortunate enough to obtain and commit to canvas the most important of such diseases as lend themselves to illustration. Some things which cannot be satisfactorily reproduced on paper — as, for instance, certain corneal lesions — were not even attempted ; while other deficiencies in the collec- tion are explained by failure to secure the necessary clinical material. 9 10 PREFACE. In the treatise on pathology and treatment which accompanies the plates I have confined myself to essen- tials — above all, to a detailed description of methods of examination, which I deemed most important to students and practising physicians. For this reason less space has been devoted to operative technique and more to the pathology and to non-operative treatment. I wish to express my sincere appreciation of the pub- lisher's efforts to bring the atlas up to the standard of the excellent series of which it forms a part. O. HAAB. CONTENTS PAGE Examination of the Eye in Disease 17 1. External Inspection by Daylight 20 2. Tension of the Eyeball 36 3. Testing Acuteness of Vision 38 4. Examination with Lateral Illumination 46 5. Examination by Transmitted Light 48 6. Examination with the Inverted Image 50 7. Examination with the Upright Image 50 8. Accommodation 50 9. Measuring the Field of Vision 55 10. Measuring the Light-sense : . . . 59 11. Testing the Color-sense 60 12. Examination for Disturbances of Mobility 62 Detection of Malingerers 74 Diseases of the Lachrymal Apparatus (Plates 1-3) 78 Dacryostenosis, Dacryocystitis, Ectasia of Lachrymal Sac. Diseases of the Eyelids (Plates 4-10) 92 1. Inflammations. Herpes Zoster and Erysipelas 92 Eczema 94 Seborrhea 97 Hordeolum 100 Chalazion 102 2. Anomalies in the Shape and Position of the Eyelids .... 104 Congenital Ptosis 104 Ectropion 105 Entropion 106 3. Injuries of the Eyelids 107 4. Tumors of the Eyelids 108 11 12 CONTENTS. PAGE Diseases of the Conjunctiva (Plates 11-19) 109 A. Confluent Inflammations. 1. Simple Catarrhal Conjunctivitis 109 2. Follicular Conjunctivitis 112 3. Gonorrheal Conjunctivitis 113 4. Diphtheritic Conjunctivitis 119 5. Trachoma 121 6. Spring-conjunctivitis 126 B. Circumscribed Inflammations. 7. Eczematous, Phlyctenular, or Scrofulous Conjunctivitis . . 129 8. Pemphigus 134 9. Variola 135 10. Acne 135 11. Scleritis 135 12. Tuberculosis 136 13. Syphilomata and Leprosy 138 Injuries of the Conjunctiva. 1. Foreign Bodies 138 •J. Ecchymoses 139 3. Burns 139 Pterygium 140 Tumors of the Conjunctiva 141 Diseases of the Cornea I Plates 20-28) 143 A. Diffuse Inflammations. 1. Parenchymatous Keratitis 143 B. Circumscribed Inflammations. 2. Eczematous Keratitis 149 3. Herpes Corneae 155 Herpes Zoster 155 Herpes Febrilis 156 4. Hypopyon Keratitis 159 5. Catarrhal Ulcer 167 Injuries of the Cornea 168 Malformations of the Cornea 169 Diseases of the Sclera (Plate 29) 171 1. Inflammations of the Sclera 171 •J. Injuries of tin- Sclera 173 Diseases of the Iris and Ciliary Body | Plates •':<» ami 31 ) 177 1. Inflammations 177 Symptoms of Iritis 177 CONTENTS. 13 PAGE Symptoms of Cyclitis 179 Causes of Iritis 181 Sympathetic Ophthalmitis 184 2. Injuries of the Iris \s7 3. Tumors of the Iris and Ciliary Body 188 Diseases of the Lens (Plates 32-34) 188 Cataract 189 a. Partial Stationary Cataracts. 1. Anterior Polar Cataract 191 2. Posterior Polar Cataract 191 3. Perinuclear, Lamellar Cataract 192 h. Progressive Cataracts. 1. Senile Cataract 193 2. Congenital Cataract 195 3. Traumatic Cataract 195 4. Complicated Cataract 196 Dislocation of the Lens 197 Diseases of the Vitreous Body (Plate 35) 199 Glaucoma (Plate 36) 203 1. Primary Glaucoma 203 a. Inflammatory Glaucoma 204 b. Non-inflammatory or Simple Glaucoma 207 Infantile Glaucoma 208 2. Secondary Glaucoma 211 Diseases of the Orbit (Plates 37-40; Figs. O, D, E, F) 211 1. Inflammations 211 2. Injuries of the Orbit 215 3. Tumors of the Orbit 216 LIST OF ILLUSTRATIONS. Plate 1. Dacryocystitis. Plate 2. Dacryocystitis with Rupture of the Abscess through the Skiu. Plate 3. Lachrymal Fistula on the Eight Side ; Ectasia of the Lachrymal Sac on the Left; Bilateral Epicanthus. Plate 4, a. Papular Syphilide. Plate 4, b. Eczematous Blepharitis. Plate 5. Meibomian or Internal Hordeolum. Plate 6, a. Eczematous Blepharitis. Plate 6, b. Molluscum Contagiosum and External Hordeolum. Plate 7, a-c. Multiple Chalazion. Plate 8. Blepharochalasis on both Sides. Plate 9. Blepharochalasis. Ptosis. Epicanthus. Plate 10. Subcutaneous Hemorrhage in the Lids after Fracture of the Base of the Skull. Plate 11, a, b. Dermoid Tumor. Plate 12. Gonorrheal Conjunctivitis in the New-born. Plate 13, a, b. Diphtheritic Conjunctivitis. Plate 14, a. Trachoma of the Lower Lid. Plate 14, b. Subconjunctival Ecchymoses (Hyphema Conjunctivae). Plate 15, a-d. Spring-conjunctivitis.' Plate 16, a. Chaff-particle at the Corneal Margin. Plate 16, b. Pterygium. Plate 17. Eczema of the Conjunctiva and of the Face. Plate 18, a. Marginal Eczema-pustule. Plate 18, b. Epithelioma of Cornea and Conjunctiva. Plate 19, a, b. Lime-burn of the Conjunctiva and Cornea. Plate 20. Herpes Zoster Ophthalmicus. Plate 21. Foreign Body on the Cornea and Dermoid Cyst of the Orbit. Plate 22. Eczema of the Cornea and Conjunctiva on Both Sides. Plate 23, a. Perforation of the Cornea by an Eczematous Ulcer, with Adhesion of the Iris. 15 L6 LIST OF ILLUSTRATIONS. Plate 23, b. Macula of the Cornea. Plate 24. Herpes Corneae Febrilis. Plate 25, ". Berpes Corneae Febrilis. Plate 25. b. Hypopyon-keratitis. Plate 26, lace. First, the eyes are carefully dried with absorbent cotton. Wet, slippery eyelids cannot he separated either in adults or in children, because the fingers cannot secure a hold without the use of such force as to provoke spasm. In many cases it is an advantage to wrap the fingers with gauze before attempting to separate the eyelids. If with all these precautions it is found impossible to separate the lids on account of swelling or spasm, or both, they should EXAMINATION OF THE EYE TN DISEASE. 25 be gently and carefully drawn apart with Desmarre's lid- elevator, care being taken that the surface opposed to the eyeball is perfectly smooth, so as to avoid injuring the cornea. The instrument must, of course, be absolutely clean. One elevator for the upper lid is usually all that is needed. If, as often happens in private practice, there is no elevator at hand, the physician can easily improvise one from an ordinary hairpin by bending the closed end so as to form a hook about 1 cm. long, which may then be carefully inserted under the eyelid. The hairpin must be perfectly smooth, and cleaned by heating before it is used. It is much better to resort to this primitive device than to force the lids apart with the unaided lingers, for it requires a very skilful hand to separate such tightly closed eyelids in a struggling child without an instrument and without injuring the cornea. Eversion of the eyelid, on the other hand, is very easy in such children ; indeed, it often occurs when it is not desired. One of the chief uses of the elevator is to prevent eversion, as the object of the examination is usually to inspect the cornea and surrounding parts, rather than the inner surfaces of the lids, and if the latter are everted inspection of the cornea is impossible. It is often necessary to evert the upper eyelid in the examination and treatment of ophthalmia neonatorum. In such cases any injury to the cornea by the finger-nail would be fatal ; the least scratch or the slightest loss of tissue might entail the loss of the eye. Hence the holder should always be used when the eyeball is inspected, especially if the lids are swollen. As has been pointed (Hit, inspection of the inner surface of the lids in such cases is quite easy, because the upper lid usually turns over as soon as the skin is drawn upward. If it fails to do so, however, the operator should wait until the baby cries, when the lid can easily be everted, even in the later stages after the swelling has subsided. Gentle traction of the outer canthus toward the temple assists the eversion and tends to fix the lid in the everted position (ectropion). 26 EXTERNAL DISEASES OF THE EYE. Id treating children with severe blepharospasm the fol- lowing must be borne in mind: Even after the operator lias finally succeeded in opening the lids the cornea can- not always be seen, because it is convulsively rolled upward. Scolding the child only makes matters worse ; the only thing to do is to wait patiently, avoiding all pressure on the parts to be examined and encouraging the child by speaking to it kindly. Usually the eyeball is rolled downward sooner or later, if only for a short time, so that the cornea can be inspected. If the spasm is so severe that the eye fails to rotate downward of its own accord, a few drops of Cocain should be instilled and the result awaited. Forceps should be used only as a last resort ; the parts are first thoroughly cocainized and the instruments must be handled as gently as possible. Always insist on making a thorough examination of the cornea and surrounding parts until a clear view of the entire corneal region has been obtained, no matter how much the child cries and struggles. The greatest care is necessary not to exert undue pressure on the eyeball, for such children often have deep ulcers of the cornea, which are liable to burst from the slightest pressure on the eye, causing permanent injuries by incarceration of the iris, distortion of the pupil, etc. Indeed, rupture of the floor of the ulcer may result in loss of the eye through infection, especially if the crystalline lens is forced through the perforation, an accident which quite easily may happen. So much for the tech nie of the external examination of the eye in children, the importance of which cannot be overestimated. In the inspection of the eyeball, to which we now turn our attention, the following precautions are to be observed: If there is redness, its nature — /. <\, first, its situation and, second, its color — affords an important clue to the seat of the disease, and therefore to the diag- nosis. The following points are to be noted : EXAMINATION OF THE EYE IN DISEASE. 27 A practised eye readily distinguishes between inflam- mation of the conjunctiva, in which the conjunctival vessels are congested, and inflammation of the cornea or iris, although both conditions produce a redness of the eye. The first condition is called conjunctival, the second ri/iari/, congestion. The first, or conjunctival congestion, is characterized by the fact that it is most intense where the blood-vessels are most marked—/, c, at the fornix and in its immediate neighborhood — and decreases in intensity as it approaches the corneal margin, being absent in the immediate neighborhood of the cornea, so that there is a zone about 5 mm. broad in which the blood-vessels are very pale (see Plate 14, a). This centripetal increase in the intensity of the congestion also appears in the marked redness of the caruncle, situated at the inner canthus, and of the plica semilunaris next to it on the temporal side, which is very conspicuous in conjunctival inflammation, and even at a distance betrays the congestion of the con- junctival vessels, as, for instance, in acute conjunctival catarrh. Giliary or circumcorneal congestion, on the contrary, increases as the corneal margin is approached, is most distinct at the corneal margin, and diminishes uniformly at every point as the periphery of the anterior segment of the globe is approached (see Plate 21). The most dis- tinctly congested corneal zone is from 3 to 7 mm. wide, and corresponds approximately to the zone least involved in pure conjunctival congestion. Hence, whereas con- junctival congestion decreases in intensity as it approaches the corneal margin, ciliary congestion diminishes in in- tensity as it recedes from the corneal margin. The blood- vessels concerned in ciliary inflammation are so deeply placed and, in part, so minute that they cannot be seen as well as the conjunctival vessels. Disregarding the question of localization, quite a dif- ference in the color of the two forms of congestion may be observed, if one has a good eye for color. The color of a conjunctival congestion is yellowish or " brick-red ;" that 28 EXTERNAL DISEASES OF THE EYE. of a ciliary congestion is more bluish, "pink," "scarlet/' or " crushed raspberry " (Plates 21 and 30, b). The differences in color and in localization are readily explained by the arrangement and distribution of the blood-vessels concerned in each form of congestion. Conjunctival congestion is due to abnormal distention of the conjunctival vessels, barely visible in the normal eye on account of their tenuity. The vessels in the sclerotic portion of the conjunctiva make their appearance at the fornix, and from all sides radiate forward and out- ward toward the cornea, breaking up into arborizations as they proceed and thereby becoming more and more minute. This enlargement furnishes the anatomical explanation of the diminution of the intensity of a conjunctival conges- tion as it approaches the cornea. As these vessels are very superficial, they show the true color of the blood when overfilled, which in thin layers is a yellowish-red. Moreover, the conjunctival vessels can be recognized by their mobility with the shifting of the conjunctiva, which is but loosely attached to the sclerotic, especially at some distance from the cornea. This mobility is often of ser- vice to clear up any doubts about the nature of such a blood-vessel. The vessels that are responsible for ciliary or circum- corneal congestion are very different in their arrangement and distribution. In the first place, they are situated beneath the conjunctiva. They also are but faintly visible in the normal eye; in fact, only the arterioles are visible, their accompanying venules becoming manifest only when the eye is inflamed. These arterioles proceed from the tendons of the recti muscles, either singly or in pairs, pursue a very tortuous course in radiating lines to the cornea, and suddenly disappear at points several milli- meters distant from the corneal margin, by entering the sclerotic, in which they ramify, and contribute largely to the blood-supply of the ciliary body and iris (ciliary re- gion). Their points of entrance into the sclerotic are often distinctly tinted and plainly visible. They are EXAMINATION OF THE EYE IN DISEASE. 29 called the anterior ciliary vessels, while those which enter the choroid at the back of the eyeball are known as the posterior ciliary vessels. The anterior ciliary vessels, before entering the sclerotic, form ramifications, the branches of which anastomose with one another and form a dense plexus of capillary loops around the cornea. Since both the larger arterial trunks and their more minute branches about the cornea lie beneath the conjunctiva, be- tween it and the sclerotic, 1 they do not move with the shifting of the conjunctiva, and present a bluish (lilac or violaceous) coloration, for the simple reason that the con- junctiva acts as a turbid medium, through which the blood (has a bluish tint. If a thin layer of milk is spread over a black surface, the milk appears blue, and in a similar way the bluish tint which we observe in the ciliary ves- sels is formed. It must be borne in mind that the superficial con- junctival vessels and the deeper ones of the episclera communicate with each other at the corneal margin, so that the conjunctiva receives some of its blood-supply from the ciliary region, through certain small branches which enter it from the episcleral, pericorneal plexus, and which in it (usually in straight lines) run backward (anterior conjunctival vessels). This explains why a ciliary congestion of some duration gradually produces more or less hyperemia of the conjunctival system also, resulting in a combination of the two forms of congestion. The converse, however, is not true : So long as the cornea is not affected a long-continued conjunctival congestion is not apt to induce ciliary congestion. The cornea possesses the peculiarity that as soon as it suffers the least injury from a scratch-wound, the entrance of a foreign body, or inflammation from any cause, the characteristic uniform circumcorneal congestion immedi- 1 Occasionally a ciliary artery, running from without and below, or from without (temporal) inward toward the cornea, is seen lying in part within the conjunctiva and movable with it. Such a branch is derived from the palpebral arteries. \ 30 EXTERNAL DISEASES OF THE EYE. ately makes its appearance and thus brings the lesion promptly to the surgeon's notice. The injury or inflam- mation may be very slight and much time and care may be required for its detection ; hence, in every case of ciliary congestion the cornea should be subjected to a thorough examination. If nothing abnormal is found in the cornea by the methods presently to be described in detail, the cause of the circumcorneal congestion must be sought in irritation or inflammation of the iris or ciliary body (iritis, cyclitis). The foregoing description applies to general congestions affecting the entire area of distribution of each system of blood-vessels ; in addition, we have to consider the local or circumscribed congestions which occur in both systems and which may be limited to a small area. This happens, in the case of the conjunctiva, when there is a local, circum- scribed lesion — for example, a slight wound or localized in- flammation in the form of an eczema-pustule (phlyctenule ) — instead of a general process affecting the entire mucous membrane, as, for instance, in acute catarrh. Under such circumstances the hyperemia, which is superficial and yel- loicish-red in color, is limited to the immediate neighbor- hood of the injury or inflammatory center ; or, to be ac- curate, to the system of vessels in the affected area. In a localized ciliary congestion the appearance is differ- ent. The color is darker and more bluish ; the vessels can scarcely be made out; and the color does not disappear upon pressure with the finger on the eyelid as readily as in conjunctival congestion. Circumscribed ciliary con- gestion is caused by inflammation of the sclera, which usually is circumscribed, or by a deep wound of long standing in the sclera. It is this accurate knowledge of the differences between the various forms of congestion which enables the practised examiner to diagnose a given case with a rapidity which astonishes the beginner. For instance, he recognizes con- junctival catarrh at a glance by the abnormal color at the inner canthus, in the region of the caruncle, plica semi- EXAMINATION OF THE EYE IN DISEASE. 31 lunar is, and adjoining conjunctiva. In another case, guided solely by the ciliary congestion, he promptly locates the seat of the inflammation or injury in the cornea, although the injured spot is barely visible. He then looks for further signs of the morbid process, and in a short time the diagnosis is formulated and even the etiology deter- mined. For instance, a patient enters the room with the characteristic alopecia and red blotches on the forehead, along the line of the hair, strongly suggestive of syphilis. There is a ciliary congestion in one eye ; on further in- spection the pupil is found to be irregular in outline (instead of round) from serrations which encroach on the papillary border, and in the iris there are yellowish-red, thickened areas. The diagnosis of syphilitic iritis is reached in less time than it takes to read this example. Not to anticipate, however, we will proceed to describe the method of examining that important structure, the cornea, which is such a frequent seat of disease. Examination of the Cornea. — We determine two f things : First, the condition of the surface; and, second, the transparency. The surface of the normal cornea acts like a small con- vex mirror in reflecting a sharply defined, small upright image of objects placed in front of it with the usual dis- tortions incident to convex mirrors. Thus the image of window-bars reflected from the corneal mirror of a patient seated before the surgeon appears slightly bent (convex), but clear-cut and distinct. This image of the window- bars is utilized to test the condition of the corneal surface, by allowing it to fall consecutively on different parts of the cornea. The patient is required to follow the uplifted finger as it is moved up and down and to either side while the surgeon watches the reflection in the cornea and is able to detect the slightest inequality in its surface. Such slight irregularities are not uncommon, and may be of several kinds : 1. The image in one part of the cornea, without being at all distorted, may appear somewhat indistinct ; the 32 EXTERNAL DISEASES OF THE EYE. .surface is evidently opaque at this point, it looks as if it had been breathed upon, and, like a moist window-pane, is a poor reflector. Opacities of this kind usually corre- spond to inflammatory areas. Opacity of the entire cornea indicates either a general inflammation or glau- coma. The precise nature of such an opacity will be described later; for the present, suffice it to say that in many cases this opacity alone should lead us at least to suspect glaucoma, and may point the way to a correct diagnosis ; we therefore emphasize the importance of noting accurately the reflecting powers of the cornea. 2. The image of the window-bars may be perfectly clear and distinct, but the distortion may be greater than normal. It may be limited to a portion of the image, or it may be general. In the first case the distorted por- tion of the image is usually found to correspond to an area which, although smooth, is either depressed below, or elevated above the general level, or presents a plane surface. The latter condition is sometimes called a facet. The distortion may be general. Two conditions are possible. Either the entire surface is rough and irregular, or beset with numerous facets, as, for instance, after repeated ulcerations ; or, more rarely, the general distor- tion of the image is due to incorrect curvature of the entire cornea, giving it a more or less conical shape, a condition termed keratoconus. The image is very small at the apex of the cone and increases in width as it approaches the corneal margin, where the lateral portions of the membrane (between the center and the margin) take part in the reflection. Keratoconus is a serious dis- turbance to vision ; it is most surely recognized by observ- ing the nature of the corneal image — another reason for training the eye in the study of corneal changes. 3. Under certain circumstances opacity may be com- bined with irregularity of the surface, as, for example, more or less rough depressions from recent ulcers, or opaque elevations from imprisoned foreign bodies, or a EXAMINATION OF THE EYE IN DISEASE. 3o rough prominence cine to an epithelial neoplasm. Foreign bodies embedded in the cornea are a very common occur- rence in practice ; their presence can always be discovered by the disturbance they cause in the corneal reflections. The following precaution is needful in many cases : Slight irregularities of the cornea, such as follow eczema, for in- stance, are more easily detected if the flow of tears is clucked tor a moment; hence, if it is very copious, the lids must be held open and the fluid allowed to run off, before the inspection is begun. After the condition of the corneal surface has been de- termined in this manner, we proceed to test its trans- parency. This is often disturbed in morbid processes, notably in inflammations. Colorless blood-corpuscles in- vading the corneal tissue produce a general or local opacity, ranging, according to the kind and degree of in- flammation, from an almost imperceptible, bluish-gray film to complete opacity, grayish-white, or, if the inflammation is purulent, even distinctly yellow in color. The eye should be carefully trained to recognize the slightest degree of yellowish discoloration, as it indicates that the disease has assumed a distinctly purulent character and the prognosis is proportionately grave. The yellow color of such an infiltration can be seen better by daylight than by artificial light. Other colorations of a more reddish hue on a gray back- ground sometimes occur in the cornea. Newly formed blood-vessels enter the inflammatory area from the corneal margin and form a delicate plexus which produces a faint reddish sheen. Usually at least the larger branches can be seen with the naked eye. Another form of opacity, with or without blood-vessels, is produced by the scars left by former infiltrations which ended in ulceration. Sometimes these cicatricial opacities are distinctly whitish or grayish-white, so that we speak of white spots or leukomata» When the dots are not very pronounced their grayish color is so like that of a recent infiltration that a beginner finds it difficult to distinguish 3 34 EXTERNAL DISEASES OF THE EYE. between the two forms ; not so the experienced practi- tioner, however, for he knows that a recent inflammatory infiltration, whether it is localized or diffuse, always has a dull surface, whereas an old macula possesses a good reflect- ing surface. Once more the value of studying the reflect- ing properties of the cornea is exemplified, since it is im- portant to be able to distinguish between an old opacity and a recent corneal inflammation. Opacities of long standing usually have a bluish tint, but the surest way to recognize them is by their smooth surface. With the growth of accident-insurance the ability to determine the age of a corneal opacity becomes more and more desirable. It frequently happens that holders of accident-insurance policies attempt to ascribe to a recent accident an opacity which has existed for some time, in the hope of obtaining damages for it along with the recent injury. The following example may serve to illustrate the importance of carefully examining for corneal opacities : A patient exhibits ciliary congestion, suggesting the prob- ability of corneal disease. There is, in fact, a circum- scribed corneal opacity, and the diagnosis of keratitis seems plausible, especially as he complains of pain in the eye ; but on inspection the opaque area is found to be perfectly smooth ; further examination shows that the pupil is not quite round and that the iris is dull and discolored ; in short, it turns out to be a case of iritis. The corneal opacity is due to a former inflammation which the patient had in his youth, and he is, of course, much impressed when we tell him that he had inflammation once before in the same eye. In persons with blue or gray i rides, corneal opacities, being practically of the same color as the iris, cannot be readily distinguished except over the black pupil. Arti- ficial light, presently to be described, is needed — indeed, the information afforded by lateral illumination is so valuable that it must never be omitted, even in the ex- amination of persons with dark irides. In the mean time, we continue the examination by day- EXAMINATION OF THE EYE IN DISEASE. 35 light, examining the anterior chamber and its posterior boundaries, the iris, and the crystalline lens. First we note whether the anterior chamber is of nor- mal depth, abnormal depth, or shallow, by ascertaining the distance of the iris from the cornea in each eye and comparing one with the other. For example, the temporal half of the anterior chamber may be quite shallow, while the nasal half is abnormally deep. This usually indicates that the lens is displaced outward toward the temporal side. If this is the case, a slight tremor of the nasal por- tion of the iris is observed when the eye is moved. The tremor may extend over the entire iris, especially if the lens is absent, as, for example, when it is dislocated into the vitreous body. Abnormal contents of the anterior chamber, such as a .grayish-yellow or yellow exudate, blood, etc., must not be overlooked. A narrow, yellowish band, or mere line in the lowest portion of the anterior chamber, indicates the presence of pus and is considered a serious symptom. The phenomenon is called hypopyon. Foreign bodies are oc- casionally met with in the anterior chamber. Pathologic discolorationsof the iris — in inflammation, for instance — can be seen much better by daylight than by artificial light, which is always more or less yellow. The normal color of the two eyes must be compared, as the color of the two irides may differ in health, although rarely. Comparison of the two pupils in respect to size, shape, and reaction to light is of the highest importance. As is well known, difference in the size of the two pupils may be a very grave symptom, indicating disease which may involve much more than the eye alone ; for example, paresis or tabes. The size of the pupil is also affected by light and con- vergence. A preliminary examination may be made by alternately illuminating and shading the eye with the hand ; but in most cases this must be supplemented by an examination with artificial light. To obtain a correct idea 36 EXTERNAL DISEASES OF THE EYE. of the shape of the pupils they must be examined in a dark room. Abnormal coloration of the pupil, crystalline lens, und vitreous body is best seen by daylight. Bluish-gray or grayish-white dots and streaks in the pupillary region in- dicate cataract. In elderly people a slight, grayish filmi- ness is sometimes observed, apparently in the depths of the lens, which has often led inexperienced men to diagnose cataract ; the phenomenon is produced by the increased reflecting power of the lens, due to the sclerosis of age. Cataract cannot positively be said to exist unless examina- tion with artificial light, in the manner to be described, reveals distinct opacities in the substance of the lens. Finally, the appearances in the deepest portion of the eye, the vitreous body, are noted in the examination by daylight. Every shade of yellow, red, brown, gray, or blue may be seen reflected in its substance. These re- flections are often of grave significance, as, for example, in the condition shown in Plate 38,0, where they indicate the presence of a very malignant tumor on the retina. Similar clinical appearances may be due to inflammatory exudates in the vitreous body or to severe hemorrhages, in which case the color of the blood is more or less pronounced. So much for the examination of the eye by daylight. We may conclude it by testing the 2. Tension of the Eyeball. The degree of intraocular pressure is tested with the finger-tips, just as we test the consistency or fluctuation of a tumor. The patient is told to look straight before him or very slightly downward, so that the tip< of the two index-fingers can be placed close together on the upper lid, over the region between the upper margin of the cornea and the equator of the eyeball. Gentle press- ure is exerted alternately with each finger, the other pre- venting the globe from rolling or moving to one side. The arms should be held in an easy and perfectly sym- EXAMINATION OF THE EYE IN DISEASE. 37 metrical position, so that the muscular tension is the same in both arms, and to do this the operator must stand in front of the patient, not to one side. For similar reasons it is better to use the two index-fingers, instead of the index and middle fingers of the same hand. The patient must be careful to avoid extreme down- ward rotation of the eyeball, as it might have the effect of raising the tension by increasing the pressure of the external eye-muscles. In rotating the globe downward the inferior rectus and superior oblique exert a direct pressure upon it, and the elevators (superior rectus and inferior oblique) do likewise, because they are put on the stretch and thereby brought into close contact with the eye. Slight as it is, this increase in the tension is enough to affect the accuracy of the test. It is not possible to obtain trustworthy results in patients who during the examination tightly close the lids, especially in screaming children. By persuasive and careful examination it is usually possible to accomplish the end in the case of an adult, even when the eyeball is sensitive to the touch. With children it is different, and in cases of suspected increased intraocular tension narcosis may be needed before the examination is satisfactory. The beginner will do well to practise this important part of the examination as much as possible on normal eyes, so as to become thoroughly familiar with the resist- ance of a normal eyeball. This method of estimating intraocular tension with the fingers is, of course, not very accurate, depending, as it necessarily does, on the sub- jective feeling of the surgeon, which is lai'gely a matter of experience. When the tension is excessively high or excessively low there can, of course, be no doubt that the eye is abnormal ; but slight departures from the normal are not always so easy of detection, especially as there are individual variations within physiologic limits. Tbus the eyes in youth are usually less resistant to the touch than in old age, when the sclera has become rigid. Here again "practice makes perfect," and the ex- perienced can, as a rule, dispense with the instruments that have been devised to measure intraocular tension, except in very unusual cases. These instruments, called tonometers, have their fallacies ; some are very complicated and it is not always convenient to use them. The most serviceable, as far as my experience goes, are those designed by A. Fick and Maklakow, both of which yield fairly accurate results if properly 38 EXTERNAL DISEASES OF THE EYE. handled. To obtain accurate results with Pick's tonometer an assistant is needed, and great care is necessary. Maklakow's method is easier and simpler. The ideal way to express the tension would be by the number of millimeters in a column of mercury correspond- ing to the intraocular pressure in each case. Instead, however, as the tension is tested with the finger-tips, we designate increased resistance by T + l, T + 2, T — 3, and decreased resistance by T — 1, T — 2, T — 3, where T + 3 denotes that the finger is unable to produce any appreciable depression in the eyeball, and T — 3, that the finger feels no resistance whatever — the globe is "as soft as mush." The examination is now continued either by artificial light or the examiner proceeds to the functional testing of the eye. The choice will depend on whether the em- ployment of the latter is necessary, or even possible. li\ on account of spasm in the lids, tears, violent pain, or serious injury, it is impossible to test the acuteness of vision, it must, of course, be postponed. In medicolegal cases, however, it is advisable to test the vision of each eye if it is at all possible. Holders of accident-insurance policies do not, as a rule, malinger at the first examina- tion, though they may do so later on, and it is often very useful (in such cases) to know in time the acuteness of vision of the uninjured eye. The functional test is also called the subjective examina- tion, as distinguished from the objective, with which we have been dealing so far, because the examiner relies on the data obtained from the patient. If it is decided to apply this test, the first step consists in 3. Testing Acuteness of Vision. The test is first applied to each eye separately ; later, to both at once. It is well to form the habit of examining the right eye first, and to preserve the same order in writing the history, as it makes it easier to understand at any future reading. Examination of the eve in disease. 39 As the acuteness of vision is usually tested for the purpose of correcting errors of refraction, myopia, hypermetropia, or astigmatism, a set of lenses should be at hand. The first requisite is a good light, to insure sufficient illumination of the signs — usually letters — by the reading of which the acuteness of vision is determined. The type-card is therefore hung in a strong light opposite, or next to a window. If the examiner is able to discern with ease the letters which correspond to his own visual power the light is sufficiently strong. This control-test should never be omitted, as any diminution of the light affects the visual acuity unfavorably. As Schweigger aptly says, the improvement in a patient's eyesight which we observe at successive examinations is very often an improvement in the weather rather than in the disease. If, therefore, the daylight is not strong enough to illumi- nate the type-card properly, artificial light must be used. The source of light may be the same as that used for the ophthalmoscopic examination later on, care being taken to protect the patient's eyes with a shade, so that the light falls only on the type-card. A transparent type-card may also be employed to insure a good illumination of the test-letters. The card is fastened to the window and a mirror is placed opposite at the proper distance, the patient reading the letters as they are reflected in the mirror. This arrangement has the ad- vantage of enabling the examiner to stand near the patient and the type-card at the same time, so as to point to the letters he is to read. In a small room the necessary dis- tance from patient to type-card can best be obtained by this device. The test for acuteness of vision is based on the follow- ing considerations : Suppose we were to test the vision by the simplest possible means, by asking the patient to tell, for instance, how many fingers we had stretched out on the background of our black coat. A normal eye would be able to distinguish such large objects at a great distance ; in fact, we should have to move away 50 meters before the 40 EXTERNAL DISEASES OF THE EYE. fingers would appear indistinct. This would be the limit ; at a greater distance than 50 meters a person with normal eyes could no longer recognize the fingers with certainty. Xow, if another person were unable to count the same fin- gers when placed more than 25 meters away, that person would possess only half the visual power, or Jfj-, because the object to be perceived by him would have to be brought nearer by one-half the distance. If the distance had to be reduced to 10 meters, to enable a person to count the fingers, his vision would evidently be ecpial to one-fifth the normal, or i§ ; and at 5 meters the visual acuity would be y 1 ^-, or -^. The acuteness of vision can therefore be expressed by a fraction in which the numerator indicates the greatest distance at which the person examined is able to recognize an object, and the denominator the e/reedest dis- tance at which a normal eye can recognize the same object — in other words, the normal distance for that object. For the outstretched fingers this distance is 50 meters. Nor- mal vision is therefore represented by |~J, or 1 ; abnormal vision, by some fraction of 1. Now, if we were actually to adopt this plan of testing the acuteness of vision we should find this running back- ward and forward with outstretched fingers over a distance of 50 meters rather troublesome. Therefore, instead of varying the distance from the patient to the object, we vary the size of the object. We use test-objects of vary- ing normal distances. Suppose, for instance, we choose 5 meters once for all as the distance for applying the test; it is evident that an object 10 times smaller than the outstretched fingers will have to be used as the standard. Such an object would be, for instance, a letter 7.5 mm. in height. Letters of this size can just be discerned by a normal eye at a distance of 5 meters; their normal dis- tance, therefore, is 5 meters ; and we place the number 5 over a row of letters of this size which form the lowest line on the type-card. In the next line above, the letters arc twice as large ; a normal eye should therefore be able to read them at twice EXAMINATION OF THE EYE IN DISEASE. 41 the distance, or 10 meters. This row of letters is desig- nated by the number 10, which is their normal distance. If no smaller letters than these can be discerned, vision is ^, or, keeping the same fraction, fa. The letters in the third row are three times as large as those in the first row (which are 7.5 mm. high) ; a normal eve should therefore be able to read them at three times the distance, or 15 meters. This row is marked 15, its normal distance. If an individual cannot read any let- ters smaller than these, his vision is evidently ^, or, keep- ing the same fraction, fa. The letters in the fourth row are four times as large as those in the first row, and are designated by their normal distance, 20 meters. If these letters, which a normal eye can read at four times the distance, or 20 meters, are the smallest that can be discerned, vision is evidently ^, or fa. The letters in the fifth row are six times as large as those in the first row, and above them is a single large letter, ten times as large as the first, which correspond respectively to visions of -^ (or fa) and fa (or -fa). The normal distance at which the sixth row should be read is 6x5, or 30, and it is accordingly marked 30; similarly, the large, single letter at the top is marked 50. The large- letter test is equivalent to the finger-test. Now we can measure visual acuities ranging from fa (or J) to fa (or fa) without changing the position of the type-card, which remains fixed at a distance of 5 meters. Or, the type-card may be fixed at 'a distance of 10 meters, in which case the readings would be t$=1, ijj ~~§? JJ= J, J$=J, according to the letters the patient is able to read. It appears therefore that the numerator in the fraction corresponds to the distance in meters of the patient from the type-card, and the denominator corresponds to the distance at which the type should be read normally. Example : The distance of the patient from the card is 5 meters; if the type marked 15 is discerned the vision is fa, or ^. A simpler way of stating the rule is : Above the line 42 EXTERNAL DISEASES OF THE EYE. put the distance that suits the patient ; below the line, the distance that Suits the norm"/ eye. In the example given above, the patient reads the type which a normal eye discerns at 15 meters, at no greater distance than 5 meters — that is, at a distance equal to ^ the normal distance ; hence his visual acuity is only \. This extremely practical system of testing the acuteness of vision we owe to Snellen, and his type-cards, which we have just described (and which can he bought in any bookstore), are now universally used ; at least his system is always followed, whether his own type-cards or others constructed on the same principle by other authors be used. Some type-cards are designed for even smaller fractions, or decimals are substituted for common frac- tion-, etc. When a transparent type-card is used it is placed beside the patient, and the mirror ö meters away ; the row of letters marked 10 therefore represents the normal type, and the numerator is 10, instead of 5, since the letters are actually 10 meters distant from the patient. For children and illiterate persons forh-like figures, E Id Fl, in various positions, of the same size as the letters, are used. These figures possess the additional advantage of being uniform in shape, whereas some letters, as VOL, are easier to read than others, like B R Z N On the other hand, this quality of not being equally legi- ble is useful in the examination of malingerers. For if a patient reads all the letters in one row easily and with- out hesitation, he is always able to discern one or more of the easier ones in the next row also ; and if he fails to do this, malingering, or at least exaggeration of his condition. may be suspected. As ;i control-test, the vision is tried at various distances. If the answers are given honestly the result will always be approximately the same; for in- stance, , ;; -, ,'-',. -,. when the test is made at the distances of 3, 2. and 1 meter respectively. The malingerer, on the other hand, is apt to claim better, or at least the same, visual acuteness as the type-card is brought nearer; hence EXAMINATION OF THE EYE IN DISEASE. 43 a suspected malingerer should always be tested at various distances. The same plan may be adopted if the patient fails to read even the largest letter, although it is better in such a case to ask him to count the outstretched fingers, the result being recorded as " Counts fingers at 0.2, or 2, or 4 meters," etc. If he is unable to count fingers, we try if lie can see movements of the hand at 0.2, 0.5 meter, etc., and record : " Perceives movement of the hand at . meters." When even this power no longer exists, the perception of light should be tested in a dark room, by alternately covering and uncovering a lamp or candle, noting the dis- tance at which the light is perceived. It is only when (qualitative) light-perception is absent that we speak of blindness or amaurosis. In testing the accommodation for the purpose of select- ing glasses, etc., consecutive texts in varying sizes of type are substituted for the letters. The type-cards (after Snellen) are provided with these text^, which arc compiled on the same principle as the letters. The foregoing description lias been made as easy as possible, and differs somewhat from that usually given, which reads simply: Acuteness of vision is determined by finding the smallest subtended angle in which the eye can recognize the shape of a given object. For objects at the same distance this angle is assumed proportional to the size of the object, which is sufficiently accurate for small angles. For larger angles the size of the object must be taken as equal to twice the tangent of half the angle. Hence the respective letters on the type-card are not exactly 3, or 5, or 10 times as large as the letters which are 7.5 mm. long, but only approxi- mately. In order to express the visual angle in commensurable terms a conventional unit has been selected. For this purpose an angle of 5' (minutes) is taken for the recognition of letters the thichiess of which is one-fifth the height. In the formula V =^ n , d stands for the distance at which the letter can be distinctly recognized; D, for the distance at which the letter subtends an angle of 5' (minutes); and V, the visual acuity. The angle 5' is arbitrary ; it corresponds to the average normal vision. Many persons see quite clearly at a smaller visual angle ; thus, the letters numbered 5 may be discerned at a distance of 7.5, or even 10 meters. Such persons would possess a vision equal to l£ and double the normal respectively. 44 EXTERNAL DISEASES OF THE EYE. It is important to observe the following precaution in testing the aeuteness of vision. When, in the examina- tion of the right eye, for instance, the left eve is to be ex- cluded from the visual field, it must not be covered with the hand or fingers, except possibly with the hollow of the hand, so that the eye can remain open. It is better to use a pair of testing-spectacles in which the left lens is re- placed by a disk of tin or pasteboard, which cuts off the view without closing the eye. Pressure on the eye with the hand or finger, even for a short time, disturbs vision by altering the normal outline of the cornea, so that the aeuteness of vision obtained is incorrect. Any one can convince himself of the truth of this statement by press- ing upon his eye for a short time. Now, suppose the right eye, for example, is to be tested. We first note the visual acuity without glasses — in other words, the uncorrected vision. If this is found to be less than 1, the effect of concave or convex lenses of varying strengths is tried. The weakest concave or strongest convex lens that produces the best vision indicates the degree of subjective myopia or apparent hypermetropia. If spherical glasses fail to bring the vision up to 1, cylindrical glasses must be tried. Cylindrical lenses, plus or minus 1 (or even other cylindrical lenses), are held in front of the eye, in a horizontal, vertical, or either of the two oblique directions, to see whether a combina- tion of spherical and cylindrical lenses, or cylindrical lenses alone, produce the best vision. The direction of the axis of the cylinder is best recorded as follows : Axis vertical, or A. v. or, simply, || ; Axis horizontal, or A. h. or = ; axis x degrees temporal or nasal above — L c, the upper end of the axis deviates x degrees from the perpen- dicular to the temporal or nasal side. The notes of the test for visual acuity would then read something like this : r. ^ _ 1>5 gph. _$_ cy ] t _o.7o || V = 1. L. -$ T) . No improvement with glasses. .- EXAMINATION OF THE EYE IN DISEASE. 45 [Ordinarily, in this country, this record would be as follows : R. E. V=^j- without correction ; with — 1.5 D sph., o — 0.75 D cyl., axis 90° V = f or 1 . L. E. V = -fo ; no improvement with glasses. — Ed.] In this patient's left eye we may have noticed a central corneal opacity, which explains the low visual acuity of y 1 ^ ; or we may find, in another case, upon continuing the examination, that the amblyopia is caused by disease in the fundus. In the above record of the right eye (R.) the uncorrected vision is ^ ; with a spherical lens the visual power is raised to y? an( l finally the effect of the cylindrical lens is to bring the vision up to 1. Ophthalmologists have their own system of numberin spectacle-lenses. Ordinarily a lens is designated by it focal length ; but spectacle-lenses are numbered according to their refractive power. A lens of 1 meter focus is taken as the unit, and, with the exception of lenses 0.5 and 0.75, all others are multiples of the meter-lens, or diopter, as it is also called. A lens of 2 D therefore has a refractive power twice as great as a lens of 1 I), and consequently half the focal length, or 0.5 meter ; a lens of 3 D has three times the refractive power and one-third the focal length of a lens of 1 D (meter-lens or ml), etc., for the refractive power of a lens is the inverse of its focal length. The smaller the focal length the greater the refractive power. To find the focal length of a lens in the dioptric system divide 100 bv the number of diopters. Thus, the focal length of a lens of 3 D is y$ =33.3 cm.; that of a lens of 8 D, 12.5 cm. To find the number of diopters for a given focal length — 10 cm., for example — divide 100 by the number of cm. in the focal length : Xffl — 10 I) ; for 20 cm. the number of diopters is 5, etc. In the old system a lens of 1 inch focus was the unit, and all the lenses in use were fractions of this unit. No. \ had a focal distance of 2 inches ; No. J, a focal distance of 3 inches, etc. The number of the lens gave the focal 46 EXTERNAL DISEASES OF THE EYE. distance (more correctly, the radius of curvature) and the refractive power at the same time, and consequently took the form of a fraction. The diopter (Ml) corresponds to lens fa in the old system. To change from the new sys- tem to the old, divide the number 40 by the number of diopters ; to change from the old system to the new, divide the same number (40) by the denominator of the fraction. For example, a lens of 2 D, new system, is No. fa in the old ; lens No. ^, old system, corresponds to a lens of 5 D in the new system. The lenses in the two systems are practically the same, the nomenclature only being different. The refractive power of the eye, as determined with spectacle-lenses by the so-called subjective test, is not always quite accurate, because accommodation conies into play, whereby myopia may be exaggerated or hyper- metropia diminished. Absolutely correct results can be obtained only by objective examination with the ophthal- moscope, or by the Schmidt-Rirrvpler method, or with the shadow-test. 1 After the acutcness of vision has been ascertained the examination is continued by artificial light in a dark room, the first step being 4. Examination with Lateral Illumination. This part of the examination is important on account of the information it affords as to the condition of the ante- rior segment of the eyeball, which cannot be obtained at all, or but imperfectly, in any other way, especially if a good corneal loupe is employed. The lamp is placed on a table to the right and a little in front of the surgeon, who sits facing the patient. With a convex lens of 15-20 D, which is found in the ophthal- moscope-case, the light is thrown into the eye under ob- servation so as. to focus on the parts which it is desired to examine with special care. The rays collected by the 1 For a full description of the objective methods of testing the refract- ing power of the eye, see the author's Grundriss und Atlas der Ophthal- moskopie. EXAMINATION OF THE EYE IN DISEASE. 47 lens form a small brilliant image of the flame of the lamp at this point. The parts of the cornea, iris, etc., illumi- nated in this way are thus brought into a bright light and stand out in strong relief against the dark background of their surroundings. Suppose, for example, the iris to be discolored, so that a gray opacity in the overlying cornea cannot be seen ; if only the cornea is illuminated, the iris, being in shadow, forms a good background for the opacities in the cornea and they at once become visible. Or, if the cornea is left in shadow and the iris only illuminated, any changes in the latter and in the pupil can be seen. The most minute alterations in the cornea, iris, and crystalline lens, which would escape detection in the strongest day- light, can be discerned by this method. To obtain the best results with lateral illumination a loupe is necessary. HadnaeWs spherical loupe is the best, as it covers a fairly large field. The loupe is held in the left hand, the right manipulating the illuminating- lens. The proper cooperation of the two lenses, on which the success of the method largely depends, is no easy matter to accomplish and requires a great deal of practice. Among other things, this method enables us to locate accurately certain minute depositions on the posterior surface of the cornea which occur in iritis and in cyclitis, and which cannot be detected in any other way. Similar small gray dots occur in the crystalline lens ; but they can readily be distinguished from the former with the aid of a loupe. For when the depositions on the cornea are clear and distinct, the crystalline lens must be out of focus ; and, on the other hand, to make a close examination of the lens the loupe must be held nearer the eye, whereupon the cornea necessarily disappears from the field. (Hence, if depositions on the cornea and grayish dots in the pupil are present at the same time, we can study the two condi- tions separately, which may be of great value.) If even by using the loupe the surgeon finds it difficult to see the depositions on the cornea, let him move his head to and fro (after he has focussed the cornea with a strong light is EXTERNAL DISEASES OF THE EVE. shining on it), and the spots will be seen to follow the motions of the head and become perfectly distinct. Some- times it is difficult to distinguish the depositions from minute dots on the anterior surface <>f the cornea. In that ease a few particles of calomel are applied to the cornea with a camel's-hair brush. The patient will not be inconvenienced if only a very little calomel is applied, which can be accomplished by tapping the brush with the finger after it has been dipped in the calomel. Now the dots on the anterior surface of the cornea can easily be -«■en distinct from those on the posterior surface, especially if the surgeon moves his head from side to side as before, or the particles of calomel are put in motion by the act of winking. If the pupil can be dilated, it is possible with lateral illumination to look into the vitreous body. The light must enter the eye as nearly as possible in perpendicular lines, and the surgeon, standing close to the lamp, directs his gaze along the entering beam of light. In this way foreign bodies, hemorrhages, neoplasms, and detachments of the retina in the anterior portion of the vitreous can be detected and their color studied. The next procedure is the 5. Examination by Transmitted Light. This important part of the examination serves to con- firm and show even more clearly some of the results ob- tained by lateral illumination. It also reveals the faintest reaction of the pupil to light. For the rest, its chief object is to detect opacities in the refracting media, the cornea, lens, and vitreous body. The lamp being placed a little behind and to one side of the patient, the surgeon throws the reflection of the lamp into the eye by means of the ophthalmoscope, illu- minating the pupil so that it appears bright red against the dark background of the eye, which is in shadow. The pupil contracts as soon as the light strikes it, unless EXAMINATION OF THE EYE IN DISEASE. 49 there is pupillary paralysis from any cause. By noting the character of the beam of light as it emerges from the pupil, after being reflected from the fundus, we can detect any opacities there may be in the pupillary area, manifest- ing themselves as more or less intense shadows which intercept the light — especially if they are located in the cornea, lens, or vitreous body. Opacities due to cataract are brought out very distinctly in this way (see Plate 33, b, c), particularly the fainter opacities of lamellar cataract, which often occur in a rudimentary form only. Opacities in the anterior or posterior poles of the crystal- line lens can also be seen, whether the nucleus be clear or opaque. If the patient, while the pupil-area is steadily illuminated, is directed to look up or to one side, an opacity in the anterior pole will move with the pupil, in the center of which it remains fixed. An opacity in the posterior pole, on the contrary, remains stationary, and appears to move downward when the gaze is directed upward, because the pupil moves upward in front of it. A posterior opacity from pigmentary degeneration of the retina can be distinctly seen only by transmitted light. It always lies close to the corneal reflex. To study minute changes in the cornea, anterior cham- ber, and iris a strong convex lens may be used with ad- vantage in the examination by transmitted light. The delicate blood-vessels, which often persist for some time in the cornea after parenchymatous keratitis, are best seen with a "loupe-mirror;" they appear as fine, dark lines against the red background of the pupil, which has pre- viously been dilated, if possible. Deposits on the pos- terior layer of the cornea also become visible. In these examinations a strong convex lens, such as is used under certain circumstances in the later stages of ophthalmos- copic examination, is fixed behind the sight-hole of the ophthalmoscope, and the surgeon approaches so close to the eye under examination that its cornea lies within the focal distance of this convex lens. The lens need not be very powerful (+6 or +8 D), or a lens of -f 15 I) to 4 50 EXTERNAL DISEASES OF THE EYE. + 18 D will answer if the ophthalmoscope happens to contain such a one. [An ophthalmoscope should always be provided with a + 16 or +20 D lens in its series. Examination of the transparent media with such a lens is most important, particularly in the study of late corneal lesions. — Ed.] When the examination by means of transmitted illu- mination has been completed, and not till then, we pro- ceed to the ophthalmoscopic examination proper, begin- ning with 6. Examination with the Inverted Image, which is followed by 7. Examination with the Upright Image. A detailed description of these two methods is found in my Grundris8 und Atlas der Ophthalmoskopie, to which reference has been made. This ends the examination for most, though not for all, patients. It may now be necessary, for instance, to measure the 8. Accommodation. In practice, accommodation is measured by finding the nearest point, P (punctum proximum), at which the small- est readable print can be deciphered. Each eye is first tested separately, by bringing the test-type closer and closer, until the letters become blurred and illegible. This shortest reading-distance is then measured with a rule, the zero-point being held opposite the sclerocorneal junction. When the accommodation is good, as in young eyes, and the test-card can be held very close to the eye, a successively smaller type must be used as the distance is diminished, because large print can be read even without proper accommodation in "diffusion-circles." The small- est readable type should therefore be selected for the test. EXAMINATION OF THE EYE IN DISEASE. 51 In measuring the accommodation the refractive power of the eye must be accurately known, as the formula A = P — R is used in the calculation, in which P and R (punctum remotum) are expressed in diopters. The number of diopters for P is found by taking the number of the lens whose focal length equals the distance of P from the cornea. If, for example, the distance from the near point to the cornea is found to be 20 cm., P is expressed by 5 D, the number of the lens which has a focal length of 20 cm. That we are justified in expressing the distance of the near point from the cornea by the number of a lens appears from the following considerations : Suppose the case of an emmetropic eye having no power of accommo- dation. If an object is placed 20 cm. distant from the cornea no distinct image will be formed on the retina, since the rays of light will be brought to a focus behind the retina, for the shorter the distance of an object from a convex lens or a combination of two convex lenses (such as is formed in the eye by the cornea and the aqueous humor and crystalline lens), the greater the distance from the lens to the image on the other side. In order, there- fore, to obtain a distinct retinal image of an object 20 cm. in front of an eye incapable of accommodation, the rays of light coming from the object must be rendered parallel, since only parallel rays entering the resting, emmetropic eye are collected on the retina. This would be accom- plished by holding a lens of 20 cm. focal length close in front of the eye, since rays coming from the focal point of a convex lens emerge in parallel lines on the other side. A distinct image of the object would, therefore, be formed on the retina ; and the eye is said to be " adjusted " or ac- commodated for such an object by a lens of 20 cm. focal length. In other words, an emmetropic eye is accom- modated for near objects by a lens whose focal length is equal to the distance of the object from the eye, the lens 52 EXTERNAL DISEASES OF THE EYE. being assumed tu be in contact with the cornea. If an eye has the power of adjusting itself to a near object with- out the aid of such a lens, it does so by increasing the refractive power of its crystalline lens, through the act called accommodation, by an amount equal to the refrac- tive power of the artificial lens that would be required. For an emmetropic eye the number of the lens which expresses P at the same time gives the value of A. For, since the distance of R is infinite, R — OD; hence, in the above example, A = 5 D. In myopic and hypermetropic eyes, on the other hand, R represents a certain number of diopters, corresponding to the degree of myopia or hypermetropia present. For ametropic eyes, therefore, the refractive power must first be ascertained by one of the objective methods before the accommodation can be determined. For myopic eyes the number of diopters which express the degree of myopia must be subtracted from the number of diopters which correspond to the distance of the near point. For example : If P is found at 8 cm., — 12.5 D, and myopia = 3 D, then A ~ 9.5 D. For hypermetropic eyes, on the other hand, the number of diopters which express the total hypermetropia is added to the number of diopters corresponding to P. If, there- fore, the near point for an eye of 4 D hypermetropia is found at 10 cm., the accommodation is 14 D. The exact state of affairs in hypermetropia is as follows : In facultative hypermetropia, in which R is virtually behind and P in front of the eye, the formula reads : A = P — ( — R)= P 4" R. In absolute hypermetropia, in which both P and R lie behind the eve — i. e. s both are nega- tive—the formula reads : A = — P— (— R) = R — P; or, in other words, A diminishes the hypermetropia by the amount of P. To ascertain whether a patient has normal accom- modation, it is needful to know the amplitude of accom- modation corresponding to his age ; for the range of accommodation decreases from year to year, because the EXAMINATION OF THE EYE IN DISEASE. 53 elasticity of the lens gradually diminishes. The following table supplies this information : de of the Bange of Accommodation fo r the Different Ages. Near point (P. p.) in meters. Far point (P. r.) Range of accommodation Age. in meters. in diopters. 10. . 0.07 c/> 14 15 . . 0.08 — 12 20. . 0.1 — 10 25 . . 0.12 — 8.5 30 . . 0.14 — 7. 35 . . 0.18 — 5.5 40. . 0.22 — 4.5 Pr. 45 . . 0.28 — 3.5 0.5 50. . 0.4 — 2.5 1.5 55 . . 0.66 -4 (H. 0.25) 1.75 2.5 (2.25) 60 . . • 2 -2 (H. 0.5 ) 1.0 3.5 (3.0) 65 . . —4 -1.3 (H. 0.75) 0.5 4.25 (3.5) 70. . —1 -0.8 (H. 1.25) 0.25 5.0 (3.75) 75 . . —0.5 -0.57 (H. 1.75) 5.75 (4.0) 6.5 (4.0) . . —0.4 -0.4 (H. 2.5) We have two reasons for wishing to know the normal range of accommodation : First, because it enables us to compute the loss of accommodation in disease ; and, second, because when the physiologic decrease in the power of accommodation has reached a certain point it interferes with the power of seeing near objects, a condition termed presbyopia. As age advances civilized man is forced to resort to the use of convex glasses. As long as vision is distinct at a distance of 25-33 cm. — that is, so long as A equals 4-3 D — no appreciable inconvenience is noticed ; but beyond that point the reading of fine print begins to be troublesome, because the book cannot be held close to the eye. Either the individual chooses larger and larger type and a better light, or gives up fine needlework, or the aid of spectacles is invoked to supply the defective accommodation. The strength of the glasses must be regulated according to the kind of work for which they are intended. A cobbler, whose working-distance is 40 54 EXTERNAL DISEASES OF THE EYE. cm., needs only half as strong glasses as does a draughts- man who works at a range of 20 cm. In the table presbyopia is assumed to begin when the near point has receded to a distance of 25 cm. from the cornea ; or, in other words, when A begins to be less than 4 D. The degree of presbyopia and the number of the lens necessary to correct it are readily found by subtract- ing the existing power of accommodation, expressed in diopters, from the working-distance desired. Example : Distance desired, 33 cm. (= 3 D) ; existing accommoda- tion, 2 D ; number of spectacle-lens required, 1 D. The foregoing applies to the emmetropic eye, and in this connection the following facts must be borne in mind : The above table shows that hypermetropic change begins at the age of 55, on account of the lessened refractive power of the crystalline lens. This tendency of the em- metropic eye to become hypermetropic must be taken into account when glasses are prescribed, by increasing the strength of the lenses in proportion to the degree of hypermetropia present. The necessary correction is in- dicated in the column of numbers marked Pr. But if cataract is present, the refractive power of the lens is at first increased, thereby compensating for the hypermetro- pia due to age. For such cases the numbers in the second column, or even lower ones, must be used. For eyes that were originally hypermetropic the spec- tacles prescribed for presbyopia must, of course, be cor- rected for the degree of hypermetropia normally present ; while for myopic eyes the degree of myopia must be sub- tracted from the number of the presbyopia-glasses. Pres- byopia makes itself felt later in short-sighted persons than in those who possess normal vision. [If the patient is astigmatic this refractive defect must be properly neu- tralized. — Ed.] In measuring normal accommodation, or the decrease in accommodation due to disease, the following facts are to be remembered : When the accommodation is very slight, and the distance of the near point correspondingly great, EXAMINATION OF THE EYE TN DISEASE. 55 the patient is unable to read print of any kind, and we have to produce an artificial near point by means of convex glasses. If, for example, it is found that the patient can read fine print with a 6 D lens at a distance of 10 cm., his accommodation is equal to 10 D (the num- ber of diopters which are equivalent to 10 cm.) less the power of the lens, or 4 D. If the patient is 10 years old, his accommodation ought to be 14 D, and he there- fore lacks 10 D. 9. Measuring the Field of Vision. In many diseases of the eye and in a number of ner- vous affections it is necessary to measure the field of vision. Whereas visual acuity depends on the function- ating power of the center of the retina only, the limits of the field of vision are determined by testing the percep- tive powers of the entire surface of the retina, and par- ticularly of its peripheral portions. With perfectly good visual acuity there may coexist gaps in the field of vision, so-called scotomata; or there may be regular or irregular concentric contractions — irregular when the field is con- tracted more in one part than in others. One-half of the visual field may be wanting, usually on both sides, a con- dition termed hemianopsia; or there may be so-called homonymous defects, dark areas of the same size and shape occupying symmetrical portions of both halves of the visual field (for example, absence of the left upper quad- rant on both sides). The limits of the field of vision can be roughly ascer- tained by very simple means, and it is better always to make at least such a superficial examination rather than omit it altogether because no suitable instrument of pre- cision happens to be at hand. The simplest way is the following : The patient, either sitting or lying down — for the examination sometimes has to be made on a patient in bed — is placed opposite the surgeon, at a distance of about 0.5 meter, so that the faces 56 EXTERNAL DISEASES OF THE EYE. of the two are in parallel planes. The patient is then required to fix his left eye, the other being covered, upon the surgeon's right eye, which is directly opposite. Keep- ing his eve steadily fixed on the patient's, the surgeon then gradually brings his outstretched fingers nearer and nearer to the line joining his own eye and the patient's, in a plane midway between them. If, for instance, the right hand is extended with two fingers held up, the fingers can be seen and counted by indirect vision, without diverting the gaze from the patient's face. If the fingers are gradually brought nearer to the line of vision, both sur- geon and patient can keep them in sight, supposing both to possess a normal field of vision; but if the patient's field of vision is small, or much restricted on the temporal side, he will not be able to see the fingers until they are quite near the connecting line. To make sure that the patient really sees the fingers, the surgeon may alternately move them and hold them still and ask the patient to tell him whether they have moved or not. In this way the sur- geon ascertains how far the visual field extends in all directions, by comparing it with the limits of his own field, although, of course, the result cannot be set down in figures. In many cases of very defective vision this simple method is the only one available, as the patient is unable to see any but the coarsest test-objects. If the lens is blurred by cataract the flame of a candle in a dark room, which is a more intense stimulus to the retina, must be used for a test-object. The surgeon screens the light with his hand and brings it successively into the different regions of the field, and, after removing his hand, asks the patient to tell which direction the light comes from. This projection-test, as it is called in contra- distinction to the ordinary method, may also be performed with the ophthalmoscope by throwing on the eye to be examined the reflection of the lam]) from various direc- tions. It forms a very important part of the examination in cataract, as it reveals any pathologic changes in the EXAMINATION OF THE EYE IN DISEASE 57 eye-ground which had been obscured by the disease. If, for instance, the patient fails to locate the light promptly in the upper segment when it is held opposite the upper part of the eye, operation for cataract is not advisable, as there are probably some detachments in the lower portion of the retina. In the exact measurement of the visual field the limits are accurately noted in angular degrees by means of an instrument designed for the purpose. This instrument, called a perimeter, also affords a means of testing the power to perceive colors (color-sense). The perimeter shows us that the normal eye does not distinguish colors clearly in the peripheral portions of the field, where black and white are still perceptible. The limit for black and white forms the outer boundary of the visual field ; next, proceeding toward the center, comes the limit for blue. The power of recognizing blue therefore extends furthest toward the periphery, while the limits for red and green lie successively nearer the center. In using the perimeter the following rules must be borne in mind, or the result will be of no value : 1. The test-objects must be sufficiently illuminated, as in testing the acuity of vision ; white objects must be a pure white, and the color of colored objects perfectly clear and distinct, not soiled nor faded by use. Hence the test- objects are to be made of white or colored paper, about 2 cm. in diameter, and renewed from time to time ; they are then pasted on a small card affixed to a carrier, which can be moved on the arc of the perimeter from the periphery toward the center. 2. It is necessary to keep a strict watch on the patient to see that his eye remains constantly fixed on the center or zero-mark of the perimeter. Unless the patient is unusually intelligent or accustomed to the examination, his eye will have a tendency to swerve from the zero-point and turn toward the approaching test-object, and he will announce that he sees it. It is manifest, however, that he has seen it by direct, not by indirect, vision ; his 58 EXTERNAL DISEASES OF THE EYE. statement is therefore worthless, and the test has to be applied anew for that meridian. To overcome this troublesome and time-consuming tendency on the part of the patient the surgeon must take his stand behind the perimeter, and face the patient and control him with his gaze. 3. When the color-limits are to be determined the patient must not be told the color of the test-object beforehand ; but he is to name the color as soon as he sees the object. When the white mark is used, however, he should be told to pay no attention to the color, but to say " Now " as soon as he sees anything moving. 4. The measurement is not to be made while the patient is tired ; and should therefore occupy as short a time as possible. When the eyes are fatigued the examination is apt to show a narrower field than really exists. Ä record-chart (after Förster), with the outline of a normal field of vision printed on it, is used to record the result of the examination. A great variety of perimeters have been devised. The one recom- mended and first introduced into practice by Förster is both simple and serviceable. It consists of a semicircle, rotating around a central pivot, with a chin-rest at the center of curvature for the support of the patient's chin. A very good instrument, in my opinion, has lately been con- structed by Ascher. It possesses the advantage that the field of vision can be projected and directly outlined on a real hemisphere, without the surgeon's being obliged to give up control of the patient's eyes, as is the oasr with other hemispheres. The hemisphere, which is not very large and easy to handle, is made of transparent celluloid. The test-objects are moved about on the outside of the hemisphere and the limits of the field immediately marked out with soft chalk, the patient holding the instrument himself in a comfortable position. [A self-registering perimeter — for example, McHardy's — is most useful. — Ed.] Abnormalities in the field of vision are often of great significance. Besides indicating functional disturbance in certain parts of the retina, they may lead to the discovery of interruptions in the optic nerve or in any part of the visual tract as far as the cerebral cortex in the occipital lobe, or of disease of the cortex itself. Among eye-affections, separation of the retina from the choroid is a frequent cause of disturbances in the visual EXAMINATION OF THE EYE IN DISEASE. 59 field. Constrictions in the field correspond to the areas of separation, a detachment in the upper portion of the retina producing a constriction in the lower part of the visual field. Pigmentary degeneration of the retina, under certain circumstances, produces marked concentric constrictions. Disseminated scotomata are found in dif- fuse choroiditis; central scotomata in disease of the macula lutea, etc. Atrophy of the optic nerve from any cause is also followed by constriction of the visual field, more par- ticularly of the color-limits, and especially the limit for green. Disease of the papillomacular bundle gives rise to central scotoma. Obscuration of the same half of each visual field (hemianopsia) points to a disturbance behind the chiasm, in the domain of the right tractus, or in the pathway to the right cortex, or in the cortex itself. Speaking generally, homonymous defects in the field of vision indicate disease of the opposite hemisphere, at some point posterior to the chiasm. 1 10. Measuring the Light=sense. The practice of measuring the light-sense, which is necessary in a limited number of cases, was also introduced by Förster, who designed a suitable instrument for the purpose, the photometer. 2 Whereas a normal eye can read the letters on a type- card even when the light is comparatively poor, there are certain diseases in which reading is possible only in a good, strong light. These diseases chiefly affect, not the nervous pathway behind the retina and in the course of the optic nerve, but the perceptive layer itself, the special- ized epithelium, whether they originate in the retina or are secondary to disease of the choroid. In syphilitic choroiditis or in the active stage of simple choroiditis, in 1 A brief survey of the most important disturbances in the field of vision, for clinicians, practising; physicians and students, fully described and illustrated, will be found in my Augenärztliche Unterrichtungstafeln, Magnus Heft v., Breslau, 1893. 2 More correctly, " photoptometer," as the term photometer is applied to instruments for measuring the intensity of a source of light. 60 EXTERNAL DISEASES OF THE EYE. pigmentary degeneration, or in detachment of the retina, the light-sense often diminishes to a hundredth of the normal. The same is true in so-called idiopathic night- blindness (nyctalopia), the cause of which is probably t<> be sought in the retina, but is not well understood. Förster' s photometer consists of an oblong box (30 cm. long, 22 cm. wide, and 17 cm. high), painted black on the in side. One of the short sides is pierced by two sight- holes for the patient's eyes, and a third opening, through which the interior is illuminated by a standard candle enclosed in a case. The size of the opening can be regu- lated by means of a shutter and screw. On the opposite side of the box are a number of vertical black lines of varying thickness on a white background, on which the light can be thrown with varying intensity by the aid of the shutter. The smaller the opening, and consequently the less the amount of light needed to recognize the ver- tical lines, the better the light-sense. The size of the opening is read off on a scale and the light-sense com- puted from it. If, for example, a patient requires an opening 10 times as large as suffices for a normal eye to distinguish the marks, his light-sense is 10 times less, or yL f the normal. It is an essential condition of trustworthy results that the patient's eyes be thoroughly rested and accustomed to the dim light. He should therefore be in a dark room at least ten minutes before the examination is begun. ii. Testing the Color=sense. It has been found that among men from 4 to 5 per cent, are color-blind, although among women the percentage is almost zero. As the most usual form is red-green color- blindness, which disqualifies a man for service as a sailor or railroad employee, it is necessary to test with scien- tific accuracy the power of perceiving color. Many color- blind persons have learned by practice to conceal their infirmity, and are able to name any given color correctly EXAMINATION OF THE EYE IN DISEASE. 61 without really seeing it; hence certain precautions are needful in making an accurate test of the color-sense. If, for example, a color-blind person is given a red and a green object he will, as a rule, be able to distinguish between them by the difference in the amount of light they reflect ; but if the confusion-colors are added he will find it very difficult, if not impossible, to pick out the required color. As red and green appear to a color- blind person like shades of gray, yellow, and blue, he is apt to confuse them with those shades. The follow- ing methods of examination are employed : 1. A large number of variously colored skeins, about as large as the little finger, are prepared, comprising the colors of the spectrum and numerous shades of gray, brown, and rose. The yarns being heaped up before the subject in a confused mass, a light-green test-skein is first laid down beside them in good daylight, on a colorless back- ground (such as a black table). If the subject under ex- amination is blind for red and green he will choose some confusion-colors [■/. e., with or without the greens — grays, drabs, stone-colors, fawns, pinks, yellows]. Next a rose skein is laid on the table : A person with red-green blind- ness will now choose blue shades, because he does not see the red in the rose skein ; while one who is blind for blue and yellow will choose red skeins, because he does not see the blue in the rose. This method was first proposed by Seebeck and more fully developed by Holmgren ; but it fails to detect many cases of color-blindness in individuals who have trained themselves to recognize colors. 2. The so-called tissue-paper contrast-test may be used. If a black or gray letter, on a colored background, is covered with tissue-paper, it appears to have the comple- mental color of the background ; green, for example, if the background is bright red. The greenish tint, however, is very delicate and cannot be perceived by a color-blind person. The thickness of the tissue-paper must be ac- curately regulated, and none but an expert can be trusted to perform the test. [This test is not of much practical 62 EXTERNAL DISEASES OF THE EYE. value. — Ed.] Pflüger's tablets for the detection of color- blindness are constructed on this principle. 3. Another method of detecting color-blindness consists in the use of colored figures on a colored background, con- fusion-colors being used for both figures and background, and the shape of the figures obscured as much as possible by a mosaic arrangement of dots, so that only the color can be plainly perceived. The dots forming the figures must be of the same color as the background. Stilling has utilized this method in his " pseudoisochromatic plates for the detection of color-blindness." The test is a delicate one and quite simple in its application, so that it need not be performed by an expert. By its aid we can detect any diminution in the color-sense for a particular color, as well as total color-blindness. The plates also contain figures for the detection of persons who pretend color-blindness. They are to be commended for the accurate determination of disturbances of the color-sense. 12. Examination for Disturbances of Mobility. In paralysis of the eye-muscles the ordinary test of requiring the patient to look up and down and to either side is not sufficiently accurate, and must be supplemented by a careful study of the double images which occur. Ob- viously, if the left abducens, for instance, is completely paralyzed, it is easy enough to demonstrate that the left eye fails to move to the left when the patient is told to fix an object held in front of him and a little to the left side. In this case there will also be a deviation of the eye toward the nasal side, because the internal rectus prepon- derates (convergent squint) ; but if the paralysis is only partial, w T e must investigate the double images before we can make an accurate diagnosis, especially if, as frequently happens, several muscles are involved. If the paralysis is recent, the patient usually consults an oculist for the diplopia and accompanying visual vertigo ; but as the paralysis progresses, the diplopia becomes less EXAMINATION OF THE EYE IN DISEASE. 63 noticeable, although it is possible even in old cases to detect its presence by using suitable means — holding a red glass in front of the eye, or producing vertical diplo- pia with an appropriate prism. In order to understand the various forms of diplopia which occur in paralyses of the ocular muscles it is only necessary to remember the origins and insertions of the external eye-muscles. The accompanying diagram (Fig. A), which the student can at any time sketch for himself, will help to make the matter clear. x* Bect.e&t». Rectsup^..... Obltnf. „Oblsup. „...RecUTit. .-..Jftectinf. Fig. A. The course of the recti muscles is easily remembered by bearing in mind that they all arise at the apex of the orbit, around the optic foramen, and are inserted into the sclera 7-8 mm. behind the sclerocorneal junction. The plane of the internal and external recti coincides with the horizontal meridian ; while the plane of the superior and inferior recti forms an acute angle with the vertical meridian of the globe, as their insertion is a little more temporal than their origin. The superior oblique (or trochlear) also takes its origin at the optic foramen and proceeds forward parallel to, and a little above the internal rectus until it reaches the trochlea, or pulley of the superior oblique, from which point its direction, backward and outward, really begins. 64 EXTERNAL DISEASES OF THE EYE. Practically, therefore, it passes around the globe in that direction (backward, outward, and downward), beneath the superior rectus, and is inserted behind that muscle, near the horizontal meridian, and a little behind the equator. The inferior oblique arises in front, on the inner floor of the orbit, opposite the lower extremity of the lachrymal crest of the lachrymal bone. It embraces the globe from below, in the same plane with the superior oblique, and is inserted behind and above, on the outer aspect of the globe, between the insertion of the external rectus and the optic nerve. If we imagine a gigantic orbit with a globe of such dimensions that we can just encircle it with both arms, we can imitate the action of the recti muscles by taking a position to the nasal side of the optic-nerve entrance, at the point x on the diagram. By embracing the globe in a horizontal plane we should imitate the action of the in- ternal and external recti ; if, on the other hand, we were to embrace the globe in a vertical plane, we should imitate the action of the superior and inferior recti. Incidentally we should notice that the globe had a tendency to slip side- wavs, as, from our position on one side, we should be holding it obliquely. To imitate the action of the oblique muscles Ave should have to take our stand on the inner portion of the orbit, in front, at the point x x in the diagram, and grasp the globe in a direction from before outward and backward, so that our hands would almost meet on the outer and pos- terior portion. If we further imagine this gigantic eye to be easily movable about its axis we shall obtain a clear idea of the actions of the various muscles by turning it in imagina- tion with our hands, as described. If we imagine our- selves, with our hands on the insertions of the muscles, turning the globe from the three points mentioned, we note the following effects : In the first position, with our arms embracing the globe EXAMINATION OF THE EYE IN DISEASE. 65 in the horizontal meridian, we simply turn it to and fro, the cornea moving from one canthus to the other in a hori- zontal plane. If we imitate the action of the superior and inferior recti, we note that when we tilt the globe upward the cornea does not move directly upward, hut, owing to our somewhat nasal position, slightly inward as well, and the upper extremity of the vertical meridian is inclined slightly inward (toward the nose). If, on the other hand, we exert a downward pull with the arm which represents the inferior rectus, the globe is rotated downward, the cornea is drawn slightly inward, and the lower extremity of the vertical meridian is brought nearer the center of the eye — i. e., inclined inward (toward the nose). If we imitate the action of the oblique muscles (from the position x x), the eye being in the primary position, the pull of the superior oblique gives the cornea an out- ward and downward direction, because the globe is ele- vated behind ; and the pull of the inferior oblique gives the cornea an outward and upward direction, because the globe is depressed behind. But if we suppose the eye to be looking outward (toward the temple) (compare Fig. A), so that the cornea is in the outer canthus, we can readily appreciate that the oblique muscles will have an almost exclusively rotatory action, with very little elevation or depression. If, on the contrary, we suppose the eye to be turned inward (toward the nose) and looking directly at us, the oblique muscles will act almost exclusively as elevators or depressors. As to the direction in which the oblique muscles rotate the eyeball, the effect of the superior oblique is to incline the upper, that of the inferior oblique the lower, extremity of the vertical median inward. By rotation is meant turning of the eye about any axis running from before backward through the lobe. Returning once more to the superior and inferior recti, we can readily understand that this pair is also capable of rotating the eye when it is directed inward, but not as much as the oblique muscles. When the eye is directed 5 66 EXTERNAL DISEASES OF THE EYR outward (toward the temple), the superior and inferior recti act exclusively as elevators or depressors. Evidently, then, we need only to know the course of the various muscles in order to understand their actions and the position they give to the cornea. The internal rectus is an adductor, the external an ab- ductor of the cornea. The superior rectus elevates the cornea and inclines the upper extremity of the vertical meridian inward when the eye is in the primary position. The inferior rectus depresses and slightly adducts the cornea and inclines the lower extremity of the vertical meridian inward when the eye is in the primary position. The superior oblique depresses and abducts the cornea (rotating it downward and outward) and inclines the upper extremity of the vertical meridian inward. The inferior oblique elevates and abducts the cornea (rotating it upward and outward) and inclines the lower extremity of the vertical meridian inward. To draw the cornea directly upward from the primary position, the superior rectus and inferior oblique must cooperate ; to turn the gaze directly down ward, the coopera- tion of the inferior rectus and superior oblique is required ; while adduction and abduction from the primary position are effected solely by the action of the internal rectus and external rectus respectively. Having now firmly fixed the actions of the muscles in our mind, we are ready to take up the analysis of the double images which occur in paralysis. Let us again suppose the left external rectus (abducens) to be par- alyzed. If a test-object — a candle, for instance — is held before the patient in a dark room, in such a position that he must turn his eyes to the left in order to fix it without turning his head, he will tell us that lie sees two images of the flame side by side on the same level. This may be explained as follows : The normal right eye fixes the flame correctly ; but the left eye can- not be turned to the left far enough for the image of EXAMINATION OF THE EYE IN DISEASE. 67 the flame to be formed on the fovea centralis (as in the right eye), and the image falls instead on a point of the retina a little to the nasal side of the fovea centralis. An image formed to the nasal side of the fovea centralis will be projected outward — L e., to the temporal side of the visual line. It is situated in the visual field, on the tem- poral side of the fixation-point, the deviation toward the temple in the visual field being proportional to the devia- tion of the retinal image from the fovea centralis toward the nose. If the light is moved still further toward the left, the right eve will follow it ; while, on the other hand, only the retinal image of the left eye will move nasalward and its false image correspondingly temporal- ward — L e., to the left. The false image (image of the aifected eye) is so called because it is indistinct, for images formed outside the macula lutea are faint, becoming more and more indistinct as the periphery is approached. In the case before us the patient sees the image of the right eye in its proper place ; that of the left eye, on the con- trary, to the left or temporal side — there is homonymous or simple diplopia. If the candle is moved back toward the right on the same level, the two images begin to approach each other ; and when a point directly opposite, or slightly to the nasal side of the center of the eye has been reached, the patient sees single, as he also does when looking still further to the right. It appears, therefore, that diplopia occurs only when the test-object is brought within the field of action of the palsied muscle ; the error can be corrected by turning the head (instead of the eyes) to the left. In paralysis of the left external rectus abducens, which under normal conditions controls the outward movement of the cornea, the false image lies to the left of the real image. For similar reasons, on the other hand, if the internal rectus of the left eye is paralyzed, the false image is displaced to the right — in that case there is heterony- mous or crossed diplopia. If the superior rectus is affected, the eye lags in eleva- 68 EXTERNAL DISEASES OF THE EYE. tion and slightly in abduction, so that the retinal image is formed below, and a little to the outer side of the fovea centralis. Hence the image of the left or affected eve lies above, and a little to the inner side of that of the right or sound eye, its upper extremity being inclined slightly in- ward from failure of the superior rectus to rotate the eve- ball. The absence of rotation becomes more marked as the eye is turned further inward, because the pull of the superior rectus is more oblique in adduction and therefore exercises a more pronounced torsion-effect. If, on the contrary, the eye is turned outward, the torsion-effect <>{" the muscle does not come into play at all, its only effect being to elevate the cornea, and the vertical distance be- tween the two images is therefore increased. Lateral sepa- ration of the images, which is not great, is most pronounced when the eye is in the primary position. If we were to investigate the double images in paralysis of the oblique muscles in the same way, we should arrive at the following general conclusion : The direction in which the false image separates from the true image always corresponds to the direction in which the eye is moved by the affected muscle; or, better: The image of flu affected eye is always projected in the direction toward which (if it wee able to perform its function) the paralyzed muscle would rotate the cornea ; nn