12 SIR DAVID BREWSTER ON THE CAUSE AND CURE OF CATARACT. 



Upon this hypothesis, incipient cataract might be cured in two ways : — 



1st, By discharging a portion of the aqueous humour, in the hope that the 

 fresh secretion, by which the loss is repaired, may contain less albumen, and 

 counteract the desiccation of the lens. 



2d, By injecting distilled water into the aqueous chamber, to supply the 

 quantity of humour discharged from it. 



The first of these methods I knew to be practicable and safe, from the fact 

 that a surgeon in the Manchester Infirmary, many years ago, tapped the aqueous 

 chamber of a female patient forty times, in the vain hope of curing a case of 

 conical cornea, which he attributed to an excess of aqueous humour. The frequent 

 repetition of this operation shows how rapidly the humour is secreted, and how 

 reasonable it is to suppose that, in the case of cataract,~a healthier secretion 

 might be produced under medical treatment. 



Although the second method of injecting distilled water into the aqueous 

 chamber presents greater difficulties, yet they do not appear to be insuperable. 

 In 1827, when I happened to be in Dublin, I mentioned this method to the cele- 

 brated comparative anatomist, Dr Macartney, who considered it quite practicable. 

 He mentioned to me that a foreign oculist, whose name I forget, had actually 

 injected distilled water into the eye of a patient with the view of supplying the 

 aqueous humour that was lost during the extraction of the lens. 



My attention was recalled to these suggestions for treating incipient cataract, 

 by the results of a series of experiments on the changes which take place in the 

 crystalline lenses of the sheep, the cow, and the horse, after death. In these 

 experiments, which were published in the Philosophical Transactions for 1837, 

 the lenses were placed in a glass trough of distilled water, and exposed to 

 polarised light ; and the changes thus produced were indicated by variations in the 

 number and character of the polarised rings, and more palpably by the gradual 

 enlargement of the lens. The distilled water passed through the elastic capsule 

 of the lens. The lens increased in size daily, and at the end of several days the 

 capsule burst, leaving the lens in a disorganised state, the outer laminae being 

 reduced to an albuminous pulp by the water admitted through the capsule. 



These experiments have an obvious importance in reference to the cause and 

 cure of the two kinds of cataract to which the human eye is subject. The aque- 

 ous humour is in immediate contact with the capsule of the crystalline lens. 

 When the humour, therefore, contains too little water, the lens has not a sufficient 

 supply of the fluid which keeps its fibres and laminae in optical contact, and 

 hence the laminae separate, and the lens becomes opaque and hard. When, on 

 the contrary, the aqueous humour contains too much Avater, the capsule intro- 

 duces the excess into the lens, and produces the more dangerous affection of soft 

 cataract, in which it is difficult either to depress or extract the lens. 



In order to cure the first of these kinds of cataract, we must discharge a 



