The cornea protects the front of the eye and is also important in focusing light on the retina at the back of the eye. Because the cornea is critical for proper vision, it is important to address any disorders or injuries promptly.
Corneal ulcers are common in horses. This disorder has the potential to affect vision unless the cause is promptly diagnosed and treated. Many equine corneal ulcers occur as a result of injury to the eye, with inflammation of the cornea (called keratitis) that ranges from superficial to deep. Superficial ulcers are usually controlled with topical antibiotics and correction of any mechanical factors. In addition, veterinarians often prescribe medications to reduce eye pain.
Corneal ulcers may be complicated by a fungal invasion; this is termed equine ulcerative keratomycosis. The fungus, which is normally present in the conjunctiva, multiplies rapidly after injury to the cornea and causes inflammation and ulcers. The diagnosis is confirmed by identifying the fungus in cells from the cornea. Treatment must begin promptly to avoid vision loss and includes both therapy with antifungal drugs and surgery. Even with aggressive treatment, vision after keratomycosis is lost in about 25% of affected eyes.
Syndromes of very slow-healing and recurrent superficial ulcers also occur in horses. In such cases, a herpesvirus is often the cause. Initial treatment involves removal of the dead, damaged, or infected tissue of the ulcer, followed by prescription topical medication.
Pus-filled sores in the connective tissue of the cornea (corneal stromal abscesses) in horses may be caused by healing ulcers or defects of the cornea and the trapping of bacteria or fungi (or both) within the connective tissue after healing tissue is formed. A white to yellow material in the connective tissue is surrounded by an intense inflammation and swelling of the cornea and formation of blood vessels. In addition, there may be a variable but sometimes intense inflammation of the anterior uvea. Treatments include topical and, in some cases, whole-body antibiotics, antifungal drugs, drugs to reduce pain, and nonsteroidal anti-inflammatory drugs. In addition, surgery may be required.
Minor lacerations of the cornea are common in horses and can usually be treated with topical antibiotics and other drugs as recommended by your veterinarian. Severe lacerations or perforations of the cornea often require surgery and more aggressive therapy. Signs of laceration include swelling or prolapse of the iris, swelling of the ciliary bodies, and blood in the eye.
Last full review/revision July 2011 by Kirk N. Gelatt, VMD; David G. Baker, DVM, MS, PhD, DACLAM; Steven R. Hollingsworth, DVM, DACVO