Affections of the cornea include inflammation, which is sometimes followed by suppuration, or the development of "matter" between the layers of the cornea, and ulceration. In all these morbid conditions the conjunctiva necessarily participates.

Inflammation of the cornea is invariably attended with more or less opacity, and may even proceed to the formation of an abscess, as it is sometimes termed; but it is necessary to note that the deposit of pus in the structure of the membrane is only indicated by a diffused yellowness in certain parts of it, and not by the ordinary form of swelling, gradual softening, and finally bursting of the sac and discharge of its contents. It would, however, be expected that whenever pus is formed a permanent opacity of the cornea in that portion will be the consequence (fig. 252).

Ulceration of the cornea is not uncommon in the dog, in one form of distemper, but it seldom occurs in the horse.

Fig. 252. - Opacity of Cornea.

Fig. 253. - Staphyloma a, The grape-like tumour.

An alteration in the form of the cornea, consisting of a protrusion of the central portion in the form of a grape-like tumour (fig. 253) (Staphyloma) associated with distension of the globe of the eye, has been met with occasionally as the result of inflammation. It is obvious that no treatment which can be employed would prevent the loss of sight in such a case, but when the appearance of the organ is objected to, the tumour may be dissected off with a reasonable probability of the wound closing, or the eye may be entirely extirpated by an operation which is very easily performed and is generally successful.