Glaucoma, a group of diseases resulting from alterations in the formation and drainage of aqueous humor (clear eye fluid), which causes an increase in intraocular pressure above what's compatible with normal function of the retina and optic nerve, was another topic covered by Dennis Brooks, DVM, PhD, Dipl. ACVO, professor of Ophthalmology at University of Florida College of Veterinary Medicine, at the recent AAEP Focus on Ophthalmology meeting.

Brooks told veterinarians who are seeing a lot of uveitis in their equine practice that they are also likely seeing horses with glaucoma. The condition is often noticed by the owner as corneal edema, which appears as a bluish tinting to the cornea, along with dilation of the affected eye. Unlike in humans and small animals, glaucoma in horses does not seem to cause pain, but blindness stemming from atrophy (partial or complete wasting away) of the optic nerve can often develop as a secondary consequence of glaucoma.

Glaucoma in the horse is frequently classified as either primary, secondary, or congenital:

• In primary glaucoma both eyes are usually affected and intraocular pressures are elevated with no obvious ocular abnormality to account for increased pressures. The condition might be heritable.

• Secondary glaucoma typically occurs due to an identifiable reason, such as lens luxation (movement away from normal position), neoplasia within eye, iridocyclitis (inflammation of the anterior chamber of eye in front of lens and behind cornea), and/or chronic uveitis.

• Congenital glaucoma is a condition the animal is born with; it is caused by developmental abnormalities.

Glaucoma in the horse is often difficult to distinguish early in the course of the condition due to the mildness of the clinical signs presented. The discomfort often obvious in small animals and humans with glaucoma is not apparent in the horse