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Horse Health 101 : Horse Health Library : Illnesses & Injuries

Understanding Corneal Ulcers With Dr. Tim Ellis

The cornea is an amazing tissue that is clear as glass, but is indeed a living tissue. It allows light to enter the eye, which permits the horse to see. The cornea is approximately 1.5mm thick which is approximately the thickness of a penny. The cornea is exposed to all the elements of our environment and therefore serves as a protective cover, shielding the eye from bacteria and infection.

There are three primary layers to the cornea; the outer layer or epithelium, stroma (the middle, thickest layer), and the endothelium (the interior layer). When the epithelium is scratched or punctured it allows bacteria or fungi access to the inner layers of the cornea. Bacteria and fungi can thrive in this environment and once established can result in the loss of an eye. All of this the result from a minor scratch that breaks the outer barrier, the epithelium, and disease can then set in.

Ulcers can sometimes be seen with the naked eye but ulceration is positively diagnosed using special ophthalmic stains. A healthy cornea is smooth and nonporous and stains will slide off the cornea. When the outer layer of the cornea is breached or damaged it exposes the stroma (the middle layer of the cornea). The Stroma is porous and the stain will adhere to it, exposing the damage. The fluorescein stain strip is orange but the stain on the eye will be bright green. We also use a Rose Bengal stain, which is a deep red color. This stain will not stick to the cornea if the tear film is normal and well adhered to the cornea. The tear film is critical to the health of the eye and an abnormal tear film will seriously compromise an ulcers ability to heal. Again, be aware that any size ulcer in the eye is a serious situation and you should seek immediate medical attention. Prompt treatment could save your horses eyesight or eye.

Catching a corneal ulcer early improves the changes of your horse keeping its' eyesight or even the eye itself. Recognizing the signs your horse's eye is in pain and seeking the help of a professional gives both you and your horse options that might not otherwise be available.

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