Keratomycosis is a serious eye disease in horses, caused by changes to the normal ocular flora of the horse. It is caused by invasion of commensal ocular fungi or environmental pathogenic fungi into the corneal stroma. It usually occurs following previous trauma to the eye or bacterial infection. Keratomycosis occurs more frequently in horses living in warm, humid climates.

Aspergillus spp. is most frequently isolated from cases of horses with keratomycosis. There are three basic types of keratomycosis which include superficial ulcerative keratitis, stromal ulcerative keratitis, and stormal abscess.

Superficial ulcerative keratitis is an ulcerated cornea with no stromal loss of malacia and cellular infiltrate in the anterior 50% of the cornea. Stromal ulcerative keratitis is the most frequent type of keratomycosis found in horses and is an ulcerated cornea with stromal loss and/or malacia and/or cellular infiltrate beyond the anterior 50% of the cornea. Stormal abscess is a nonulcerated cornea with stromal cellular infiltrate.