For this operation chloroform is not at all necessary. Indeed surgeons prefer not to give it if the patients are old enough to keep still.
In children the lens is soft, and cataract., when complete, is dealt with in them by passing a needle through the cornea, and through the capsule of the lens, and stirring up some of the soft lens so that it escapes into the chamber behind the cornea—the anterior chamber of the eye (p. 448). It is gradually absorbed there, and after some weeks, when all evidence of the operation has disappeared, the process is repeated with another portion of the lens. In about three months, by repeated operations, the lens disappears, and sight is restored.
Diseases of the Retina (p. 449), Choroid Coat, and Optic Nerve are numerous, and are the causes of serious defects of vision and of blindness. It is useless to consider them in this work, since their detection requires an oculist. Some features regarding them may be mentioned. Very serious disease may exist in the deep parts, and at the back of the eye, without any evident symptom. The sufferer is aware of something wrong from failing sight, which he in vain strives to benefit by spectacles.
Inflammation of the retina (retinitis), inflam mation of the choroid coat (choroiditis), in flammation (neuritis) and atrophy (wasting) of the optic nerve are the names of some of these affections. They arise from many varied causes. Exposure to cold, changes in the blood such as exist in anaemia and in syphilis, diseases of the brain, and many other causes operate in producing such affections. It is of the utmost importance to observe that excess in spirituous liquors and in tobacco not infrequently leads to failure of sight from changes in the nervous structures of the eye. For such cases total abstinence is the only treatment. In women too prolonged nursing may produce weak sight from affection of the retina and optic nerve.
Separation of the Retina (Dropsy of the Retina).—In this disease fluid is poured out between the retina and choroid coat at the back of the eyeball (p. 449), with the result of partly separating them from one another. The retina is caused to bulge forwards, at least that part of it behind which the fluid is. Blindness more or less complete, according to the extent of the separation, results.
Treatment of various kinds has been tried with indifferent success. Complete rest in the horizontal position for some weeks, the use of warm packs to promote sweating, a calomel and jalap purge twice a week, and light diet are the lines of treatment to be followed imme diately the detachment is recognized. In sonic cases an oculist may deem au operation worth trying.
Glaucoma is the name given to a disease which affects every part of the eyeball and ends in complete blindness. The chief feature of it
is that the eyeball becomes of a stony hardness. It sometimes comes on quickly in an acute form, sometimes it creeps on slowly. The dis ease occurs in old and weak persons, sometimes from exposure to cold, sometimes apparently from fright, and from other causes.
The symptoms of the acute attack are vio lent neuralgic pains in the eyeball, brow, and temple, and perhaps vomiting. Dimness of sight conies on rapidly. The patient sees rays of colour round the flame of a lamp, candle, or gaslight. The eyeball, as Already mentioned, becomes very hard. In chronic cases there are only occasional attacks of neuralgic pain, and the eyeball gradually becomes of a stony hard ness. In time other changes occur in the cornea, lens, &c. In advanced cases the pupil has a greenish look ; hence the name glaucoma, which means green tumour.
The treatment commonly adopted is the per formance of the operation of iridectomy, noted on p. 481. It was first suggested by the dis tinguished German oculist, Von Graefe.
The ophthalmoscope is the instrument by means of which the deep parts of the eye can be examined, and the condition of the nervous coat at the back ascertained. It consists of a small mirror on a handle. The mirror is slightly concave (hollowed). It is held in front of the eye of the examiner, and in its centre is a small hole through which he looks. The patient sits opposite the examiner. Behind his head and to the side is a lamp producing a bright light. The examiner catches the light on the mirror and throws it through the pupil of the eye he is looking at through the small hole in the mirror. The back of the eyeball is illuminated just as one might illuminate a room by throw ing a strong beam of light from a bull's-eye lantern through an opening in one wall. The use of the instrument requires practice ; for unless the examiner's head is in the direction of the light reflected from the eye, the pupil will appear black and lie will see nothing. As soon as he catches the light coming back from the eye, he sees a red glow from the back of the eye, and by gradually bringing his eye, with the mirror in front, nearer, he at last reaches the position from which he sees the opposite wall of the eyeball. The optic nerve entrance, the blood-vessels passing over the retina, &c., are seen, the condition of the humours of the eye is perceived, and one familiar with the healthy appearance can make out change from disease. The instrument was devised by the late Professor von Helmholtz of Berlin. The mirror may be used alone, or with a doubly convex lens.