Cataract

Cataract, an impairment of the natural transparency of the crystalline lens of the eye. This may be the result of inflammation consequent upon injury, in which case the cataract is termed traumatic; or the condition may be congenital, i.e. the infant is born with an opacity in its lens. Lamellar or laminar cataract is a curious variety in which the lens is not opaque throughout, but there is a turbid zone, enveloping a transparent central portion of lens, and enclosed by transparent lens substance. Diabetic cataract occurs in rare instances in the subjects of diabetes. Senile cataract is much the most common variety of cataract; it is rarely met with before middle life, and beyond the fact that it is probably the result of defective nutrition, little can be said with regard to its causation. The detection of senile cataract in the early stages of the disease is not so simple a matter as might be supposed. Since the invention of the ophthalmoscope the diagnosis has been greatly facilitated. The peripheral portions of the lens are usually the first to be involved, and the surgeon often finds it necessary, before pronouncing a confident opinion, to dilate the pupil so as to bring the outlying parts of the lens into view. The pupils of old people always lose to a greater or less extent the blackness they originally possessed, hence it is not uncommon for patients to fear that they may be the subjects of cataract, when really no such thing is the case, and all that is required is a pair of glasses to remedy the defective vision. Again, loss of sight may result from disease of the fundus of the eye, the lens being perfectly clear. The confusion of cases of this kind with cataract is not possible if a careful ophthalmoscopic examination is made.

In the early stages of cataract improved vision often results for a time from the use of atropine; hence have arisen innumerable "cataract cures." The dilatation of the pupil so produced affords, however, only a temporary relief. There is no cure for cataract but by removal of the opaque lens. The old method of effecting such removal was by couching, i.e. forcibly dislodging the lens from its position in the line of vision and causing it to sink down into the vitreous humour. This plan is a rough and dangerous one, and is now completely discarded. The modern operations are of two kinds. In young subjects removal by solution is performed. A cataract needle is introduced and a small puncture made in the anterior capsule of the lens (the pupil having been previously widely dilated). The lens matter gradually protrudes through the wound, and becomes absorbed; a second or even third operation is often necessary before it perfect result is obtained. In older persons the opaque lens is hard, and cannot be dealt with by the method of solution; an extraction operation, therefore, becomes necessary. Before this can be effected the cataract must become mature, and this often, unfortunately, entails a delay of months or even years. In suitable cases, however, thanks to the improvements of the modern ophthalmic art, there are few surgical operations so satisfactory as those for cataract removal. The introduction of cocaine has led to the disuse of anaesthetics in the performance of the extraction, and in skilled hands it is it very rare occurrence for a failure to occur in an uncomplicated case. After removal of the lens it is always necessary for glasses to be worn, in order to replace the loss of refractive power, which absence of the lens entails. Moreover accommodation is also lost, so that glasses of different strengths have to be employed for near and for distant objects.