and Carcinoma of the Eye. 299 



thickening of tBis tunic, or by a morbid accumulation of 

 aqueous humour behind it. I believe, in general, both 

 these circumstances combine to produce the disorder ; the 

 cornea becoming not only opaque, but both softer and 

 thicker than in iis natural texture ; and in consequence of 

 this, the aqueous humour. behind the cornea pushes it for- 

 ward, and thus enlarges the anterior chamber of this hu- 

 mour. I have sometimes seen the whole cornea sloughed 

 ofl'during an acute purulent ophthalmy, and a while opaque 

 substance gradually effused from the ulcerated surface, suf- 

 ficient to form a complete cover to the iris ; after which thrs 

 opaque body has gradually projected in a conical shape, 

 until at leneth it has become so pron)inent as to hinder the 

 eyelids from closing over it. I have at othertimes seen the 

 projecting cornea partly opaque, end partly transparent; 

 the pupil being distinctly visible through the transparent 

 part, but the power of vision wholly destroyed. Sometimes 

 the circumference of the opaque cornea projects, its central 

 part appearing depressed, and resembling the bottom of a 

 plate or dish ; and sometimes, near to the centre of the 

 opacity, in the case last mentioned, there is an irregular 

 black appearance, which a cursory observer might mistake 

 for a pupil. No part of tliis aperture, however, is percep- 

 tible on a careful inspection, and the eye of course is de- 

 prived of all useful vision *. 



' So long as the projection of the opaque cornea can be 

 covered by the eyelids without painfully stretching them, if 

 it be not accompanied with an irregularity in the surface of 

 the cornea, and the sight of the other eye continue perfect, 



• The cornea not unfrequently projects without losing its transparency, 

 assuming a conical shape instead ot that which is spherical ; in consequence 

 of which change the eye at first becomes myopic ; but when the projection 

 is more advanced, it causes so unequal a refraction in the rays of light as to 

 destroy correct vision. In cases of this description I have repeatedly dis- 

 charged the aqueous humour, and endeavoured afterwards, by moderate 

 pressure, to prevent the return of tlie projection ; but on the reproduction 

 of the aqueous humour the conical projection has always reappeared. If 

 only one eye be thus affected, the sight of the o:her remainin r perfect, all 

 llie purposes of vision will beobt lined from this alone; but, if the cornea of 

 boih eyes be conical, much advantage may be obtained from wearing spec- 

 tacles the rings of which are filled with an opaque substance that has a small 

 hole in its centre, not more than the tenth or twelfth part of an inch in dia- 

 meter, the smallness of which aperture, by lessening the pencils of the rayj 

 of light, will prevent the confusion that must othervrise be occasioned by 

 their unequal refraction. Persons who have a projecting cornea should be 

 particularly careful to avoid blows on the eye ; since the projection is usually 

 accompanied with a preternatural thinness of this tunic, which renders it 

 easily ruptured : when this happens, the iris is liable to be involved in the 

 ■wound, and the sight to be more or less injured by the derangement that 

 takes place in the figure iuid size of the pupil. 



the 



