The cornea is the outer portion of the eye ball and in horses it is commonly affected with disease. The most common problem of the equine cornea is the superficial loss of tissue from the surface called corneal ulceration. Corneal ulceration is usually caused by foreign bodies, such as pieces of hay, getting in the eye and causing irritation. Because the objects that cause the problem are typically covered with bacteria and fungi, infection of the ulcer is common and it can lead to permanent loss of sight if not treated aggressively. For this reason, any time your horse is squinting an eye or has ocular discharge, call your vet immediately as this is not a wait and see condition.
Treatment of these ulcers can either be quick and easy with antibiotic ointment for 5 to 7 days or it can take months for an ulcer to heal. It depends on the horse and type of infection. Severe infections require treatment every 2 hours, which can be difficult unless the horse is in hospital staffed 24 hours a day. Because many horses resist this lengthy treatment, a tube can be placed in the eye to assist in treatment.
Regardless, some of these eyes will rupture and result in blindness. If an eye ruptures, surgery may be required. A new technique has been developed using amnion, which is part of the afterbirth when a foal is born. This tissue is saved after a c-section on a mare, then processed and frozen until needed. Amnion is sutured over the damaged cornea to protect the cornea and aid in healing. Dr. Leslie Easterwood from Texas A&M indicates that after thawing, the amnion tissue is sutured directly over the corneal defect on the eye. A study at Florida showed 90% of the horses were visual after this treatment.