There have been so many eye cases lately I thought we should go over some of the more common causes of equine eye issues. I consider eye problems to be emergencies for the facts that it is often difficult for an owner to identify what is going on, and even a small trauma or infection can result in loss of vision.
The most common reason for owners to call me about an eye is that it is tearing excessively. Although that might not sound like a big deal, it indicates: 1.) a blocked tear duct, or 2.) a painful eye. Sometimes the eyeball is fine, but the tear ducts are blocked and the tears have no place to drain and simply spill over the lower lid. It is common to find this issue in times of dryness and dust, or in an individual with allergies, or a tumor blocking the normal flow of tears. We always stain to cornea to be sure it is undamaged and then insert a flushing instrument into the tear duct to rinse it out and remove the obstruction. There may be a few days treatment with an anti-inflammatory, but usually there is no further problem.
If the horse is tearing because of a painful eye, we need to determine what is causing the pain. Possible causes include an ulcer, laceration, foreign body, or infection – in any of the tissues of the eyeball. Most often we fund an ulcer in the cornea, the clear portion of the eye that we see through. We stain the eye with a substance that will adhere to the deeper corneal layers, but not the intact surface. If anything stains bright neon green, we know that the cornea has been damaged. Visually we can tell an infected ulcer from a non-infected ulcer, and we select an antibiotic. If the infection is severe we may take a culture to send to a lab for determining exactly what bacteria or fungal species in involved so that we know exactly what antimicrobial to use if out first choice does not prove quickly helpful. Ulcers of the cornea can change rapidly so serious attention is required. Horses that will not allow ointment to be applied will have a treatment tube sutured in place to insure the medication is delivered appropriately.
Another thing owners notice other than tearing might be a cloudy appearance. This can be associated with an ulcer or a disease called uveitis; an infection of the front chamber inside of the eyeball. There are several causes of uveitis ranging from bacteria to trauma, and all are serious and require aggressive therapy to avoid vision loss.
Many tumor types can be found in and around a horse’s eye. Horses with pink eyelid skin are prone to squamous cell carcinoma, a common skin cancer, and it actually begins as a red scab on the lid margin, and not a tumor. The small scab stage is the best time to remove the cancer and inject a chemotherapy treatment in the hopes of resolving the disease quickly with no further treatment requirements.
I hope this has made you more aware of the seriousness of eye problems. Next time you are by your horse, gaze into that eye and gain an appreciation for what is normal; only then will you be able to identify subtle early signs of disease. Cheers!
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