Extraction, the most radical cure for hard or lenticular cataract, is probably the most difficult to perform. The patient should lie on a firm table, and an assistant hold up the upper eye-lid, when the operator, with a cataract-knife, (Fig. 20, Plate DXV.) makes an incision of the lower half of the cornea, entering the instrument at the outer canthus, about a line from the sclerotic coat, and nearly the same distance above the horizontal plane, pushing the knife at once across the cornea, and transfixing the other side, as delineated in Fig. 5 of Plate DXVII., and then cutting downwards and outwards, care being taken not to wound the iris. If the operator cannot force the point of the knife through the opposite aspect of the cornea at once, before the aqueous humour escapes, he should gently press the cornea in front of the knife, which causes the iris to retract, and then proceed with the knife; or he may withdraw the knife, and com plete the incision with David's scissors, which are to be used to enlarge the incision if too limited. After the incision of the cornea, great care is re quired to employ no degree of pressure, otherwise the vitreous humour will protrude; the capsule needle or cataract lance is then cautiously inserted onwards to the cataract, and the capsule lacerated by crucial incisions, the operator previously seeing the pupil distinctly, which if not fully dilated, a curtain should be interposed between the patient and the light. Tue lens generally follows this capsule needle, but if not, the most gentle motion of the eye upwards, together with very delicate pressure on the lower eye-lid, discharges it; but if this does not take place, David's scoop should be inserted between the cornea and the iris, and the lens assisted by its pressure. The operator should carefully investigate if the section of the cornea be large enough, and the capsule of the lens sufficiently lacerated. All fragments of lens should be carefully removed with the scoop, the patient put to bed, the eyes covered with a handkerchief, and warm applications, and otherwise treated anti phlogistically, according to the state of the in flammation. When the right eye is the seat of the cataract, the section of the cornea should be up wards. Extraction is recommended in hard cata ract, keratonyxis for soft and capsular cataract. Capsular cataract frequently follows extraction, and then keratonyxis is requisite. There are a number of circumstances mentioned by authors, in terdicting extraction, which appear frivolous. Con genital cataract is almost always the capsular, and should be removed by keratonyxis, when the child is six months old.
Glaucoma, (from yhaumos, bluish green), consists, first, in an alteration of the texture of the vitreous humour and its membrane, ultimately involving the retina, choroid coat, and lens; the vessels of the choroid being varicose. The eye has an unhealthy appearance, and feels firm and hard, the cornea is turbid, the sclerotic of a bluish or yellow tinge, with tortuous varicose vessels piercing this tunic at a distance from the cornea, leaving the latter surrounded with a white circle; the iris, if naturally blue, becomes gray, and if black, a dirty brown; the pupil is dilated, irregularly angular or oval, and immoveably fixed as it were to one canthus. The individual cannot distinguish light from dark ness. As the disease advances, the green colour increases; the lens swells and presses the iris forwards into the anterior chamber of the aqueous humour, when it is termed glaucomatous cataract.
The treatment consists in local blood-letting, blisters applied to the temples, moxas, issues and setons to the nape of the neck, laxatives, mild diet, and the avoiding of all exciting causes.
Amaurosis, or gutta serena (from C11.4CIU pee, to ob scure), is generally consequent on a diseased af fection of the retina and optic nerve, since the function or structure is deranged. The patient sees in the light gnats, or flies, or threads or spots flying before his eyes; while in the dark he per ceives fiery sparks, or balls, and flashes of blue, yellow, or red; and often sees double and squints. The flame of a candle appears to change from white to yellow, red or green; the halo also ap pears of these colours; at last total blindness en sues. When the eye is examined, it is either clear or cloudy, the cloudiness being deep in the eye, the bottom of which is of a pale greenish colour resembling horn. The pupil is very variable, commonly irregular, angular and fixed. This dis ease is sometimes slow, at other times rapid, and is even congenital, being more hereditary than cataract; and its causes are exceedingly various, from which it is either temporary or permanent, depending either on a deranged function of the eye itself or the brain, or some more distant organ, or even on an organic affection of them all. When it originates from diseased function it is sometimes capable of being cured, but when from diseased structure incurable; and none of the diseases of the eye so completely baffles the skill of the surgeon. `When diseased function is the cause, it is generally from pressure of the blood on the internal carotid or its branches, particularly the opthalmic artery on the optic nerve; also from the arteries dis tributed on the choroid coat when varicose pressing on the retina. In these cases, blood-letting, blisters, moxas and issues to the nape of the neck, pedi luvium, shower-bath, powerful cathartics, and low diet occasionally cure it. When suppressed dis charges are the cause, they require to be restored, or others to be substituted; when it arises from over-excitement, it is generally easily cured, and it. is a peculiar circumstance in this case that the patient can see while under the influence of a glass of wine. When narcotics, it is curable; emetics are recommended, but they should never be administered, as vomiting is a common cause of the disease, and as calomel with other cathartics removes the diseased secretion of the stomach, and more effectually prevent regurgitation of the bile. When hydrocephalus, tumours in the course of the optic nerve, exostosis at the basis of the cra nium, thickening of the retina, shrinking or atrophy of the optic nerve cause the disease, the case is hopeless. It is often very difficult to ascertain from what this disease originates. In northern and tropical climates, from the glare of the sun or snow, a variety of amaurosis occurs, which, if it produces blindness during the day, is named Nyc talopia; if during the night, Hemeralopia. A third variety exists, in which the individual is blind all day until a certain hour, when he sees dis tinctly, or he sees and is blind every alternate day, or is only blind one day in the week, fortnight, or month. These varieties are treated by purgatives, by removal from the effulgence of light, blisters to the temples, moxas to the nape of the neck, elec tricity, and nourishing diet with tonics.