Corneal ulcers follow injuries to the cornea that progress instead of healing; decreased tear production, or entropion. Ulcers which do not heal promptly often become infected. Large ulcers may be visible to the naked eye. They appear as dull spots or depressions on the surface of the corneas. Most ulcers, however, are best seen after the eye has been stained with fluorescein.
Horses with corneal ulcers often have blepharospasm (tight shutting of the eye in response to the presence of an eye irritant or foreign body on the surface of the cornea), epiphora, and often are extremely sensitive to light (photophobic). These horses may also appear head shy and reluctant to allow physical examination of the head region. Corneal ulcers are dangerous and most receive prompt veterinary attention. Early treatment is vital to avoid serious complications or even loss of the eye. Corneal scrapings examined under the microscope will show if the ulcer is infected.
Uncomplicated small surface ulcers respond to topical ophthalmic antibiotic ointment applied 4 times a day. Atropine ointment is used to dilate the pupil.
Deep or infected ulcers require intensive antibiotic therapy by subconjunctival injection, or by the intravenous route. Cultures are taken by corneal scraping and antibiotics selected according to the sensitivities. The eylid may have to be sutured together to protect the eye and keep it from drying out. Soft contact lenses also have been used for this purpose. Eye surgery to create a flap of conjunctiva to cover the cornea may be required in difficult cases. White spots of the cornea may persist after healing. If these scars are large enough to interfere with vision, they can be removed by eye surgery.
Prevention of Corneal Ulcers
All painful eye disorders should receive immediate veterinary attention. In particular, foreign bodies should be removed as soon as possible to prevent corneal damage. Corticosteroids, which are incorporated into many eye preparations used for treating conjunctivitis and inflamed eyelids, should not be put into eye suspected of having corneal injury. This may lead to rupture of the cornea. Horses wearing fly masks must be checked on a regular basis as they may develop ulcers despite the protection. Unless masks are removed daily, ulcers may go unobserved and progress to a severe stage, before the damage is discovered. As a rule, take masks off at night, to avoid this potential complication.