The Basics on Corneal Ulcers

Dr. Caity Cosentino

Horse’s have very expressive eyes. They can let you know they’re happy to see you or mad that you’re 15 minutes late with their breakfast. The transparent window looking into their eyes is referred to as the cornea. The cornea has a tendency to be injured in the everyday life a horse leads. Debris from rolling may get into their eye, hay from a feeder, swishing tails and branches on trail rides. As an owner or manager, it is important to know the common signs of injury to a horse’s cornea, and the appropriate steps that should be taken to prevent a more serious problem that can lead to loss of vision or loss of the eye itself. If you have ever had a scratch on your own eye, you know that damage to the cornea is usually very painful. Horse’s with fresh injuries will usually squint their eye, have drainage/excessive tear production from the effected eye, often have swelling, and sensitivity to light. Once there is a defect or abrasion on the eye’s surface, it is prone to becoming infected with either bacteria or fungi.

The safest thing to do is have a veterinarian out to assess the horse’s eye to see what layers of the cornea are effected and what other structures of the eye may be involved. Your veterinarian will examine the eye’s exterior structures as well as the interior of the eye. The cornea is composed of three basic layers; the outer most layer is the epithelium, the layer underneath that is the stroma, which comprises the bulk of the cornea, and the very bottom layer is Descemet’s membrane which sits atop the endothelium. Fluorescein stain is used to detect abrasions in the cornea. The stain will stick to the stroma and highlight areas where the epithelium has been denuded in bright green. The stain does not uptake on healthy epithelium. If the ulcer is deep enough to be down to Descemet’s membrane, there will be no uptake of stain there either. These ulcers pose a very real threat to the horse’s eye.

Superficial corneal ulcers are the mot common eye injury to occur in horse’s. They are easy to diagnose, and when caught early, are usually easy to resolve. Once a veterinarian has made the diagnosis, medications depending on the severity of the ulcer and the amount of edema in the cornea. A triple antibiotic ointment will be the staple treatment for uncomplicated ulcers. The more frequently the ointment can be applied early on the better, but trying to get at least 3 applications in a day is ideal. The key is preventing the cornea from becoming infected while the eye is in the process of healing itself. If the eye heals over without proper treatment, abscesses may form in the cornea, which can be a challenge to get rid of. Anti-inflammatory drugs, such as banamine, are used as well to reduce inflammation and improve comfort. Some ulcers will have loose epithelium on the surface of the eye and debridement by a veterinarian can be helpful in the healing process and reduces areas that bacteria and fungi have to hide.

As an owner or barn manager it’s a good idea to have a tube of triple antibiotic eye ointment on hand in case you find a horse has a swollen eye and it will be some time before a veterinarian can come out to assess it. If you plan to treat the eye however, it is important to make sure the ointment you have came from a veterinarian and does not contain a steroid, which can make the eye worse. It’s always best to consult with your veterinarian before initiating any treatment. Caution also needs to be taken when administering the ointment topically as well so that further trauma does not occur to the eye with the tip of the tube. If you have horse’s for a long enough period of time, you will likely have to treat a corneal ulcer in at least one of them. There is no need to panic at the sight of a swollen eye, but eye problems in our equine friends should never be taken lightly and are best seen by a veterinarian to assess the extent of the problem. Maintaining a clear window into their souls is a critical part of maintaining our horse’s overall health and comfort.