Horses have prominent eyes that are susceptible to injury. Tree branches, hay stalks, and other foreign bodies may scratch or lacerate the cornea leading to infection and ulceration. If the condition is not recognized and treated early, the horse may risk going blind in the eye and suffering a lot of pain along the way.
The cornea is the clear membrane that encapsulates the front of the eyeball. It is comprised of numerous layers of tissue not unlike the layers of an onion. When an outer layer is compromised by a foreign body, bacterial contamination may be introduced between the subsequent layers of the membrane. Infection will lead to tissue necrosis and sloughing. Eventually, the full thickness of the cornea may be jeopardized, allowing the inner membrane of the eye to protrude. This condition is called a desmetocele, and it is very fragile. The horse risks losing its eye in this situation.
A severe eye injury would probably be noticed immediately, but a tiny corneal scratch may go undetected, at least at first. It doesn’t take long for a small injury to turn into a complete disaster, however. In a few days, the problem may threaten the horse’s eyesight. Swelling of the eyelids, conjunctivitis (red inflamed tissue around the eye), photophobia (avoidance of bright light and guarding of the eye), increased tearing of the eye, and cloudy areas on the cornea are all reasons to suspect an injury may have occurred. If any of these symptoms exist, contact the veterinarian immediately.
Do not apply medications to the eyes before the doctor has a chance to examine the horse. Ophthalmic ointments can contain corticosteroids that may accelerate corneal ulceration. Also, medications used previously for other eye problems may introduce infection into the eye.
The veterinarian will apply a fluorescein stain to the cornea which will only adhere to damaged tissue if present. The healthy cornea is normally so slick and non-porous that the stain is easily rinsed away with saline. A lesion will appear as a bright green area of stain uptake when the doctor shines a black light called a wood’s lamp onto the cornea.
Eye ulcers are extremely painful. If not treated, they may lead to permanent scarring or rupture of the cornea. If a foreign body remains trapped in the eye, the horse may require sedation to facilitate removal of the contaminant. Medications that may be prescribed will include a topical pain reliever, a drop or ointment that dilates the pupil, and an antibiotic preparation for the eye. Dilating the pupil will help prevent adhesions from occurring between the inflamed cornea and the iris. If drugs are used to dilate the pupil, precautions should be used to make sure the eye is protected from sunlight and watch for colic as a side effect of the drug. If there is no corneal damage, a steroid drop may be used to treat redness and swelling.
The prognosis for even minor injuries to the eye depends on swift recognition, assessment, and diligent treatment. All eye injuries should be considered emergencies and be immediately examined by a veterinarian.