Corneal Ulcer Correction and Improving Visual Outcomes: Scar Wars

"My job is to help horses see better, and to help you guys to help horses see better," said Dennis Brooks, DVM, PhD, Dipl. ACVO, a professor of ophthalmology at the University of Florida at the fourth annual Promoting Excellence Symposium of the Florida Association of Equine Practitioners (FAEP), held Sept. 25-27, 2008, in San Juan, Puerto Rico.


Ulcer before
Patched ulcer
Fully healed

A melting corneal ulcer when presented (top), treated with a patch of amnion membrane (center), and two months postoperatively (bottom).

Brooks reviewed a variety of treatment and management strategies for corneal ulcers, with a focus on not only resolving the ulcer in each case, but maintaining the horse's vision.

Brooks noted that he was originally taught that the horse's cornea heals poorly. He's since found that to be untrue--as long as the treating veterinarian knows what they're doing. The equine cornea is strong, he noted, as are the diseases that affect it. Practitioners need to be aggressive to fight them.

A practitioner has a good chance of maintaining the horse's vision in the affected eye when faced with a variety of foes; new methods, such as amniotic grafts and serum, in concert with tried-and-true treatments, including antibiotics and atropine (the latter used to relieve pain and dilate the pupil) when indicated, make this possible.

Brooks expressed enthusiasm for the use of amnion--a material taken from the sac surrounding embryos that has antimicrobial, antifungal, and antiprotease (thwarting damaging enzymes) properties.

Amnion is a strong avascular (not supplied by blood vessels) material. Neutrophils and bacteria attack it instead of the ulcer, giving the eye a chance to heal. Brooks wants the amnion graft to stick for five to seven days, then fall off. His current goal is to develop a blood-based glue to attach these grafts in the standing horse.

"'This is going to change everything," Brooks said. "It already has."

The use of serum is another recent advance in equine ophthalmology. Produced by spinning down the patient's own blood, Brooks said serum is a relatively cheap option for reducing protease activity. He prefers not to refrigerate the serum, which he said has lasted and retained efficacy for eight days in trials. In a clinical setting he replaces the stock every week.

He advises clients to put in the serum as often as they can work it in with the other applications in the patient's treatment.

"The more the merrier," he said. "You can't overdo it, that I've seen."

Brooks noted that he occasionally sees horses in which serum seems to have a pain-relieving effect. He has also, rarely, seen horses react to it. He asked practitioners to contact him if they see either, so it can be documented.

Another new development in ophthalmology is problematic, although it's been noted in multiple areas of equine medicine--resistance to medications. Brooks noted both fungal and bacterial resistance to treatments, meaning some treatments that worked as recently as two years ago simply aren't effective anymore, and "bugs" in different areas of the country are changing in different ways. He said there isn't one cookbook approach that will work everywhere, emphasizing the need for specific diagnostics, including culture, cytology, and deep corneal scrapings prior to treatment in order to target the specific trigger and initiate pinpointed treatment.

Some other points of interest from Brooks' talk on corneal ulcer care:

  • The top layer of the eye, the epithelium, increases from eight to 15 cell layers per day. We know that the speed of epithelial migration is about 1mm/day. Therefore, a 7mm deficient will appear healed in about seven days, barring complication (and remembering that the process it slowed by the use of non-steroidal anti-inflammatory drugs). But it takes a while for the cells to adhere--so when the ulcer looks clear via flourescin stain, remember that it's not really healed yet.
  • Atropine, used to dilate the eye, is a necessary evil. You know topical atropine has gone systemic if both eyes dilate when you're only treating one. In these case, be careful, understand it will affect gut motility, and remember that it lasts in the system for two weeks. Brooks noted that sunlight will not damage a dilated horse's retina unless he stares directly at the sun for an hour--it's safe to exercise these horses.
  • The frequency and combination of treatments impact effectiveness. Some things can be used, or might even be more effective, in combination. Others should not be mixed. Some require a set number of treatments per day, and some should be given as often as the client can manage it. Brooks said he works his clients hard. There is some research into subpalprebral lavage systems, which allow constant doses of medicine directly to the eye.
  • Stem cell treatment might be the next big thing. "It's definitely something that going to influence what we do in the eye," Brooks said.

In conclusion, he expressed hope that practitioners these days are better equipped to fight eye problems in horses than they have been in the past. "Things are changing for the better," he said. "It's taken a long time, but we're finally making progress."

About the Author

Erin Ryder

Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care.

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