26 Sir D. Brewster on the Cause of Cataract, 



luminous image placed at a distance, and the interposition of 

 minute apertures and minute opake bodies of a spherical 

 form, it is easy to ascertain the exact point of the crystalline 

 where the fibres and laminae have begun to separate, and to 

 observe from day to day whether the disease is gaining ground 

 or disappearing. 



" In so far as I know, cataract in its early stages, when it 

 may be stopped or cured, has never been studied by medical 

 men ; and even when it is discovered, and exhibits itself in 

 white opacity, the oculist does not attempt lo reunite the se- 

 parating fibres, but waits with patience till the lens is ready 

 to be couched or extracted. 



" Considering cataract, therefore, as a disease which arises 

 from the unhealthy secretion of the aqueous humour, I have 

 no hesitation in saying that it may be resisted in its early 

 stages, and in proof of this I may adduce the case of my own 

 eye, in which the disease had made considerable progress. 

 One evening I happened to fix my eye on a very bright light, 

 and was surprised to see round the flame a series of brightly 

 coloured prismatic images, arranged symmetrically and in re- 

 ference to the septa to which the fibres of the lens are related. 

 This phaenomenon alarmed me greatly, as I had observed 

 the very same images in looking through the lenses of animals 

 partially indurated, and in which the fibres had begun to se- 

 parate. These images became more distinct from day to day, 

 and lines of white light of an irregular triangular form after- 

 wards made their appearance. By stopping out the bad parts 

 of the lens by interposing a small opake body sufficient to 

 prevent the light from falling upon it, the vision became per- 

 fect, and by placing an aperture of the same size in the same 

 position, so as to make the light fall only on the diseased part 

 of the lens, the vision entirely failed. 



" Being now quite aware of the nature and locality of the 

 disease though no opacity had taken place so as to appear ex- 

 ternally, I paid the greatest attention to diet and regimen, 

 and abstained from reading at night, and all exposure of the 

 eyes to fatigue or strong lights. These precautions did not 

 at first produce any decided change in the optical appearances 

 occasioned by the disease; but in about eight months from its 

 commencement I saw the coloured images and the luminous 

 streaks disappear in a moment, indicating in the most unequi- 

 vocal manner that the vacant space between the fibres or 

 laminae had been filled up with a fluid substance transmitted 

 through the capsule from the aqueous humour. These changes 

 took place at that period of life when the eye undergoes that 

 change of condition which requires the use of glasses, and 



