72 



VETEEINAEY OPHTHALMOLOGY. 



Hypopyon^ 

 Onyx. 



tion becomes changed to pus, 

 wliicli pus shows as a yellow 

 opacity in the corneal tissues. 

 The suppuration maybe limit- 

 ed, or the entire cornea may be 

 involved. If inclosed by corneal 

 tissue, forms an abscess ; if 

 superficial, an ulcer. Some- 

 times the pus sinks down be- 

 tween the layers, forming an 

 onyx from its resemblance to 

 the lunula of the finger-nail. 

 Often will see hypopyon in the 

 anterior chamber, caused by 

 the pus settling to its bottom, 

 These two conditions may co. 

 exist. Vascularity may attend the suppuration, and 

 with acute symptoms, or there may be very little pain 

 and vascularity, which latter form is very dangerous 

 from death of tissue and sloughing. Abscesses may be 

 absorbed or burst open, or pus may undergo fatty or 

 chalky degeneration, leaving dense opacities. An ulcer 

 may be an opened abscess. But, remember, superficial 

 ulcers may occur without a pi'imary abscess. Ulcers 

 are of variable size, shape and depth, and are dangerous 

 according to their location; The crescentic marginal 

 is exceedingly dangerous from its tendency to encircle 

 the cornea and thus deprive the centi-al cornea of riutri- 



Fig. 35. 



