5. Glaucoma following extraction occurs as a result of (a) soft lens matter blocking the angle of the anterior chamber. As a rule the tension will usually subside under eserine, but evacuation of the anterior chamber (see [p. 233]) may have to be performed; on the whole the results are satisfactory. (b) The incarceration of the capsule in the wound, pulling forward the iris and blocking the angle of the anterior chamber. Division of the lens capsule is usually sufficient to make the tension subside. Failing this, sclerotomy should be performed; the prognosis is not nearly so good when the increased tension is due to this cause.
6. Striate keratitis usually makes its appearance on the second or third day after operation. The cornea near the line of incision presents a grey striped appearance with the striæ arranged at right angles to the wound. Pathologically the condition is due to an infiltration of the deeper layers of the cornea, the striped appearance being caused by wrinkling of Descemet’s membrane; the condition probably arises from septic infection. As a rule the affection subsides without giving rise to further trouble, but occasionally local suppuration and even panophthalmitis may follow.
A grey horizontal line about the centre of the cornea is sometimes seen after an eye has been too tightly bandaged; this always disappears when the bandage is removed.
7. Erythropsia (red vision) occasionally follows the extraction of the lens, and is probably due to bleaching of the visual purple following the admission to the eye of an unusual amount of light; it usually disappears in a few weeks.
8. Defective vision. Glasses have to be worn after removal of the lens. Usually patients who were previously emmetropic require about + 11 to see clearly for distance and + 15 for near vision.
The section produces some flattening of the corneal curvature at right angles to the line of the incision; this usually amounts to about two diopters.
COUCHING
Couching is the removal of the lens from the pupillary area by depressing it backwards into the vitreous. It is rather a relic of the past than a present-day operation, although it is extensively practised by quacks in India. Under certain circumstances the operation still seems justifiable; it is very simple, and is followed by immediate restoration of vision, but the subsequent risks of irido-cyclitis, retinal detachment, and glaucoma are so great, that, according to some authorities, couching should only be undertaken in preference to extraction when the latter operation has only a chance of one in three of giving satisfactory vision.
Indications. The chief indications for its performance are:—
(i) The presence of a fluid vitreous, the patient having had the lens of the other eye extracted with bad results.