CORNEA AND AQUEOUS FLUID 79 



cases of slightly inflamed " red " eyes, about the nature of whose 

 condition there may be doubt ; and they may sometimes be 

 found, in very small degree, in eyes which otherwise have revealed 

 nothing suggestive of any organic affection. Very little experience 

 enables an observer to distinguish between " K.P." in its various 

 forms, and other abnormalities due, e.g., to actual changes of the 

 posterior surface, an example of which may be seen in Fig. 40 

 and Fig. 46, C. Fig. 46, B, illustrates a beam of almost square 

 cross-section, formed by cutting down the vertical diameter of 

 the slit, illuminating a large spot of " mutton fat " K.P., of the 

 type seen in those cases of cyclitis which are often somewhat 

 loosely styled tuberculous because many improve on empirical 

 treatment with tuberculin. The long-continued presence of such 

 massive precipitates may exert some influence on the overlying 

 and adjacent epithelial surface so that it displays fine vacuola- 

 tion (9). Some fine precipitates are also depicted in Fig. 46, B ; 

 often K.P. may take the form of only very fine dust-like particles. 

 The importance of slit-lamp examination for the presence of fine 

 K.P. in suspected sympathetic disease of the sound eye following 

 injury to the other eye, cannot be overestimated (16). 



Fig. 46, C, represents the appearance of the posterior corneal 

 face in an earlier stage of the disease in elderly people previously 

 referred to under Fig. 40. Only a beginner could mistake these 

 markings for precipitates on the back face of the cornea. The 

 four bullous or ring-like markings on the anterior face depict 

 droplets of oil such as may be seen if an oily solution of a drug has 

 been used on the cornea ; the illustration would equally serve for 

 pathological elevations or bullae of the epithelium of the anterior 

 face of the cornea. The shadow-streaks in the beam and the 

 optical simulation at the deep face will be noted. 



The onward course of the beam in Fig. 46, B, is readily visible 

 through an aqueous fluid whose relucency is pathologically 

 increased by colloid and cellular products of inflammation. The 

 discrete particles visible in such an aqueous fluid are usually not 

 individual cells, but clumps of cells — white or red blood cells, or 

 pigment cells detached from the uveal layer. The normal aqueous 

 fluid has slight relucency, which is not usually visible with the 



