328 Veterinary Medicine. 



proper, the lesions of keratitis, opacities, ulcers and cicatrices will 

 be shown. To complete the examination of the cornea the light 

 should be focused upon the iris so that it may be reflected back 

 through the cornea. This will reveal the most minute blood- 

 vessels, any cell concretions on Descemet's membrane, or any 

 foreign body in the cornea which may have been overlooked. 



Aqueous Humor. Unless the cornea is densely opaque, the 

 anterior chamber can be satisfactorily explored by the oblique 

 focal illumination. The cloudiness or milkiness of iritis or 

 choroiditis furnishes a strong reflection from its free particles of 

 floating matter, its blood and pus globules, and its flocculi of 

 fibrine. The latter have usually a whitish reflection, the blood 

 elements a red (hypohaema), and the pus a yellow (hypopyon). 

 The writhing movements of a filaria scarcely need this mode of 

 diagnosis. Sometimes, and especially in the horse, detached 

 flocculi of black pigment are found floating free in the aqueous 

 and are highly characteristic. 



By this illumination one can easily determine the distance of 

 the cornea from the iris and lens (depth of anterior chamber) 

 which is lessened by the forward displacement of iris and lens in 

 undue tension in the vitreous (glaucoma, retinitis, tumors, 

 bladderworms),or of the iris alone, in irido-choroiditis with accum- 

 ulation of exudate in the posterior chamber of the aqueous. The 

 depth of the anterior chamber may increase in cases of luxation 

 or absence of the lens or softening and atrophy of the vitreous. 



The adhesion of the iris to the back of the cornea may be satis- 

 factorily demonstrated by focal illumination. 



Iris. The lesions of the iris are exceedingly common in con- 

 nection with recurring ophthalmia in the horse, and examina- 

 tions in the intervals between attacks are of the greatest import- 

 ance. The eye should be examined as already stated, at a window 

 or door, and if available by the aid of a mirror. Any changes in 

 form or color, or luster should be carefully noted, any tension of 

 the eyeball, or angularity of the upper lid, and any slight blue 

 opacity round the margin of the cornea. Then the prompt or 

 tardy response of iris and pupil to light and darkness must be 

 made out. To complete the test the eye should be treated with 

 homatropin for three-quarters of an hour and with cocaine for ten 

 or fifteen minutes, and then subjected to oblique focal illumination. 



