The equine eye is a complex organ with a vital function. The horse is well-adapted for its existence as a prey species, with horizontally shaped pupils set within eyes situated toward the sides of its head that facilitate an almost 360-degree field of vision. The horse also possesses an exquisite ability to see movement, because of the high number of motion-detecting cells populating the equine retina. For the modern-day domesticated horse, vision might not be as critical for survival, but for peak performance it is very important. Eye injuries, infections, or inflammation not only cause severe pain but also might progress rapidly and affect vision permanently. Therefore, it’s vital that owners quickly identify issues or abnormalities and take appropriate action sooner, rather than later, for the best possible outcome.

Signs to Look Out For

Often the first and most subtle sign you will notice is a change in eyelash position. Look at your horse’s face from the front and at the eyes from the sides. The affected eye’s lashes might begin to point down slightly before the condition progresses to the more obvious squinting. You might notice increased blinking, or the eye could be completely shut. Other signs include swelling of the area around the eye, excessive tearing, or a change in the ocular discharge to a thick consistency that’s yellow or blood-tinged. Look for asymmetry: Horses often will have a condition only affecting one eye; compare the eyes to aid your evaluation. Rubbing an eye continually is another sign of discomfort that might need immediate attention. Pink, wartlike growths originating from any part of the eye could represent a type of cancer called squamous cell carcinoma that can spread if not addressed swiftly.  

Horses have extremely strong eyelid muscles and can keep their eyes shut tightly, often when you approach to investigate. They might also throw their head in the air or try to get away from you. If your horse won’t let you get a good look at his eye, your veterinarian can use sedation and potentially a local nerve block to temporarily numb the eyelid and facilitate detailed examination. If your horse does allow you to look at the eye more closely with a penlight, you might notice general reddening; a red, white, or yellow region; apparent cloudiness; or the eye might even appear blue.  

What to Do

If you see any abnormality in your horse’s eye, contact your veterinarian immediately. Never begin treating with an ointment you have left over from a previous issue or from a friend without talking to your veterinarian first. Some ointments can make certain conditions much worse. For example, if you apply a steroid ointment intended for treating uveitis (inflammation inside the eye) in an eye with a corneal ulcer, the ulcer will likely worsen, which could affect treatment success