CATARACT.
Senile cataract is the most commonly met with type of opacity of the lens. It can only be remedied by operation, as no known agent exerts any influence in preventing the progressive blindness, though when the opacity is greatest in the nuclear part of the lens some improvement of vision may be maintained by keeping up dilatation of the pupil by the use of tinted glasses and Atropine, and should myopia have occurred from increase in the refractive power of the lens distant vision may be considerably improved by using weak concave glasses.
Plans for hastening the ripening of the cataract by tapping the anterior chamber and inducing changes in the epithelium of the anterior capsule whereby the aqueous humour may cause disintegration of the fibres of the lens arc seldom resorted to; the best practice is to wait till the ripening process has spontaneously advanced to such a degree as will justify opera tion.
The patient having been put into the most favourable condition of health by judicious dietary, &c., and a mild purge having cleared out the bowel, the operation is now usually performed under the local anmsthesia of a 2 per cent. Cocaine solution. Of the numerous operations in use, the most satisfactory one for general purposes is the combined operation, which consists of a flap operation and an iridectomy, so-called in contra distinction to the simple operation, in which the lens is extracted without section of the iris. After the conjunctival sac has been thoroughly flushed by sterilised saline solution, an incision is made by entering the point of the cataract knife at the visible margin of the cornea through the anterior chamber, and after the exit of its point at the opposite corneal margin a semicircular flap is cut upwards, the curved portion being constituted by the margin of the transparent cornea. A portion of the iris is next removed with the view of preventing prolapse and subsequent incarceration of the iris in the corneal wound; the capsule of the opaque lens is freely incised by the cystotome, after which by gentle pressure the lens is extracted.
The wound is finally cleansed and a dressing consisting of a pad of dry lint adjusted evenly over the eye and secured by bandage; the patient must be kept as quiet as possible after the operation, till healing has become established; atropine should be instilled on each daily removal of the dressing; he may he permitted to sit up on the third or fourth day, and bandages may be dispensed with at the end of a week from operation and dark glasses worn. Both eyes should he kept bandaged from the first.
In the simple operation the steps are the same, hut the corneal flap is larger; there is no portion of the iris removed, and the circular pupil result ing gives a better appearance. The iris must be watched, however, and if at the end of 24 hours it is found to have prolapsed the corneal wound must be opened up and an iridectomy performed.
M'Keown's irrigation method aims at the removal of the residual cortical debris by means of fluid pressure. A stream of sterilised saline solution is made to gently flush out the interior of the capsule, removing all cortical fragments without the usual assistance of manual pressure, the scoop or massage. The advantage of the method lies in its applica bility to the removal of unripe senile cataracts, which consequently can be operated on at an earlier stage than formerly. The method is used in India, where, however, the favourite operation is extraction of the lens in its capsule—a practice seldom resorted to at home owing to the danger of loss of the vitreous.
Cataracts occurring before the age of 25 years, whether complete or lamellar, may be effectively dealt with by the operation of needling or discission. This consists in inserting a needle through the cornea and lacerating the anterior capsule of the lens so as to expose the lens fibres to the absorptive action of the aqueous humour after the instillation of atropine, care being taken that the iris is left untouched. Repetition of the operation is usually necessary, and atropine must be daily instilled.