Corneal Ulcers

A large, severe corneal ulcer that has been stained with fluorescein dye.

Have you ever shown up to the barn to find your horse’s eye swollen closed and dripping excessively? Sometimes they bump their heads, or even get flicked in the eye by a neighbor’s tail. No matter what the cause, early and appropriate medical management is crucial for eye injuries. Most veterinarians will not put off an appointment to look at an injured eye- even if the owner reports that it appears mild. So many things can go wrong with eyes, especially when the horse decides to rub the eye repeatedly on the inside of his front legs! Once this cycle starts, what originally was a minor injury can rapidly progress to a very serious condition. Therefore – as vigilant owners, we really have to “keep an eye” on eyes!

Horse’s corneas are vulnerable to injury because of their convex contour. The cornea is the outer most layer of the globe – or the “glassy” surface which we can touch with our fingers. They protrude off the horse’s face in order to accommodate a wide field of vision, but this added benefit of panoramic vision also comes with an increased risk of injury. Horse corneas protrude so far that some veterinarians will joke that “a horse’s cornea enters the room before it does.”

Corneal scrapes (also called ulcers) are nothing to sit on since horses will reliably advance their severity by rubbing their eye. The initial signs of an injury to the cornea are:

· Squinting and sensitivity to bright light (photophobia)

· Excessive tearing (epiphora)

· Swelling of the tissue around the eye (conjunctivitis)

· Pain (blepharospasm)

We can’t always see the injury on the corneal surface just by looking at it. Most of the time, the veterinarian needs to put a special dye in the eye called fluorescein stain. The stain will run off the surface of a healthy, in-tact cornea. But, if any layers of the cornea are scraped away, as is the case with ulceration, the dye will saturate the area and then show up in direct light.

Corneal ulcers are painful and extremely aggravating for the horse (and the owner for that matter!) The pain sensation can be overridden by applying pressure to the eye or by rubbing it. But the trauma induced to the corneal surface by rubbing only results in a worsened condition of the ulcer since it causes more layers of the cornea to peel away. For this reason, it is imperative that owners prevent their horse from rubbing the eye during the ulcer rehab period.

Here are some effective management tips:

1. The veterinarian will usually prescribe antibiotic eye ointment to treat the ulcer. Unfortunately, the eye ointment is not very user friendly and must be given usually 4 to 6 times per day. And by “day”- we mean a 24 hour period! If the antibiotic ointment can be effectively given on a 24-hour basis, the healing period will be shortened significantly. If 24-hour dosing is not possible, then giving doses “first thing in the morning, and last at night” will be of added benefit.

2. When working on the horse, wear gloves. The bacteria on human hands are the strongest on the body, and often are resistant to some antibiotics. If we inoculate these bacteria into the horse’s injured eye during the course of trying to treat it, they will compound the problem and impede healing.

3. Keep your horse in a darker stall since light is a painful stimulus. Use of a fly mask is also helpful. Some people actually place a duct tape patch on the fly mask over the affected eye to provide an additional shield.

4. In addition to eye medications, the veterinarian will put the horse on an anti-inflammatory medication such as banamine. Make sure that anti-inflammatories are given at the exact interval and amount that the veterinarian prescribes. This way, you will maximize the comfort of the horse, and thus minimize the change of him rubbing his eye to alleviate discomfort.

5. Finally – DON’T dig through the tack trunk and find an old tube of eye medication to put in the eye yourself. Not all eye medications are the same and using the wrong one can have disastrous consequences. For instance, did you know that there is a kind of eye medication that, if applied to an eye with an ulcer, will stop the ulcer from healing for several months? In addition, there is another kind of eye medication that can cause severe colic and induce blindness by dilating the eye. Don’t take risks by trying to “self-treat”! Your horse needs his eyes and the risk is unacceptably high if you gamble on mystery medications.

When you find your horse with a squinting and watery eye, get him out of the light, put on a fly mask, stop him from rubbing the eye and call the vet. You and your horse will be glad that you did!

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