With their large, exposed eyes, horses are at risk for diseases of the cornea, the clear outer layer of the eye, said Elizabeth A. Giuliano, DVM, MS, Dipl. ACVO, associate professor of veterinary medicine and surgery at the University of Missouri, at the 2010 Western Veterinary Conference, held Feb. 14-18 in Las Vegas, Nev.

Ulcers are probably the most common corneal disease. These can occur after a trauma to the eye, irritation, or infection. Minor ulcers often heal quickly, without many problems, but more serious ulcers can lead to globe rupture or cause significant scarring that can permanently damage vision.

Some signs of a corneal ulcer include pain and squinting, redness, tearing and discharge. In addition, the cornea, which is clear, might appear discolored: white, bluish, yellow, red, or brown, she said. If a horse has an ulcer, the anima’s owner should call a veterinarian promptly.

Ulcers can be painful, and if not treated properly, the horse can lose its vision. A veterinarian will try to preserve vision and make the animal as comfortable as possible while the eye heals.

During the examination, the veterinarian will probably apply a fluorescent-green dye to the surface of the cornea, and then examine the eye. He or she might also scrape the eye to take a sample for testing to see if there is a bacterial or fungal infection.

Many ulcers are so severe that both topical and oral medications are needed if the eye is to be saved.

Owners need to be aware that horses with corneal disease often require many weeks of therapy, she concluded, depending on how significant the problem is.