Through the Equine Looking Glass

Corneal ulcers can do more damage than you think.

Corneal ulcers can do more damage than you think.

By Megan Arszman in The American Quarter Horse Journal

horse eye
Check your horse's eyes frequently to ensure they are healthy. Journal photo.

One fall morning, my American Quarter Horse mare, Skips Satin Lark (aka “Lark”), didn’t seem to have the same bright eyes that she normally had. I also noticed significant tearing from her left eye. Thinking she just had something in it, I flushed her eye with artificial tears and applied a warm compress. Later that day, it was still bothering her, so I took her to our veterinarian, who diagnosed her with a simple scratch in her eye and gave me some ointment to put in her eye three times a day.

A week later, her eye wasn’t healing, and it began to look cloudy, so once again I hauled her to the veterinarian.

The diagnosis was that she was suffering from a corneal ulcer and needed to be treated by a veterinary ophthalmologist right away. After a two-hour haul to the University of Illinois at Urbana-Champaign Veterinary Teaching Hospital, she underwent extensive examinations and stains. If we had waited until the next day, she might have lost her eye.

Before that night, I had never heard of a corneal ulcer, which is surprisingly common in horses.

What is a Corneal Ulcer?
Corneal ulcers stem from any trauma that occurs in the eye. In Lark’s case, a simple scratch became infected with a fungus. Trauma can be anything from scratches from hay or dust or running into a fence post. Other causes of corneal ulcers include parasites, viruses, eyelashes irritating the eye or lack of tear production.

Diagnosing
The simplest signs of tearing, squinting and sensitivity to bright light are key to knowing something is wrong with your horse’s eye. When I went to the University of Illinois at Urbana-Champaign, Dr. Erica Tolar was a second-year resident in ophthalmology there, and she saw many patients like Lark with eye problems, including corneal ulcers.

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Dr. Tolar says a horse owner who sees any of those symptoms needs to contact his or her local veterinarian for a specific diagnosis immediately.

“Corneal ulcers can deteriorate quickly, even in a matter of hours,” Dr. Tolar said. “It is best not to delay or self-medicate.”

Key factors in diagnosing a corneal ulcer are time and the right medications. Steroids should never be used, because they prevent the body from mounting a good immune response and allow infectious organisms to multiply, which will hinder healing.

Dr. Tolar’s initial examination is a lengthy, meticulous procedure.

“The first step is to get a good history,” says Dr. Tolar, who used fourth-year veterinary students to assist with diagnosis and treatment. “We ask multiple questions to help walk us through what has happened and what the horse has been treated with. It is helpful for owners to bring all medications they use or a list of what they have done.”

To make the exam easier, Dr. Tolar injects a small amount of local anesthetic over a nerve that controls the function of the upper eyelid. Once that has taken effect, the entire eye is assessed with a diffuse light. If an ulcer is suspected, Dr. Tolar takes a culture to determine which bacteria or fungus might be causing the problem.

To get a better look at the ulcer, a fluorescein stain is applied, and a hand-held microscope is used to determine the depth of the ulcer.

“Determining if the horse has an ulcer is the easy part,” Dr. Tolar says. “The difficult part is determining the cause and the appropriate treatment. Depending on the depth, we may recommend medical therapy or surgical therapy.”

Dr. Tolar says that even if a horse is started on medical therapy, he might still need surgery, because the eye can still deteriorate while being treated.

Treatment
Each treatment plan depends on the depth of the ulcer, amount of the cornea affected and how much the owner is able or willing to spend. On one extreme, the ulcer can be superficial and not complicated by any fungus or bacteria. This treatment plan can be just medical therapy and involve topical antibiotics three to four times daily.

The other extreme for medical therapy can involve hospitalization, a tube placed under the upper eyelid to facilitate frequent treatment (subpalpebral lavage tube), topical antibiotic therapy every one to two hours including one to two antibiotics, atropine, topical autogenous serum (which is made by drawing the patient’s blood and drawing off the serum that is used to coat the eye) and anti-fungal therapy.

“Even with doing everything possible and there being no limit on money supply, we may not be able to save the eye,” Dr. Tolar says. “Ulcers that are infected don’t go away on their own.”

Recovery
If the horse is being cared for at home, you can help make him comfortable by keeping him in a darkened stall and limiting exercise. Using a mask like a fly mask or one provided by your veterinarian should protect the eye. Also, it’s recommended that hay be fed from the ground to prevent further damage.

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Full recovery may take weeks or months, depending on the severity of the ulcer. Owners will notice red blood vessels in the cornea surrounding a healing ulcer. This is a good sign that the cornea is starting to heal.

A big concern for all parties involved is how much vision is lost due to the ulcer.

“What is perfect eyesight in animals? Our patients can’t tell us how their vision is to start with,” Dr. Tolar says. “We have a difficult time determining if it is ‘perfect’ to begin with. If the cornea is affected by a large ulcer, or surgery is involved, we have to assume their vision is affected. Does that stop some horses from doing their job? No, not necessarily.”

Unfortunately, there doesn’t seem to be a guaranteed way to prevent corneal ulcers from occurring in your horse.

“It is hard to prevent ulcers, since they are usually secondary to trauma, whether that is a piece of straw, a nail in the stall or a whip lash,” Dr. Tolar says. “Some people feel that trimming the long hairs around the eyes predisposes them to ulcers, but that is hard to prove.”

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3 thoughts on “Through the Equine Looking Glass”

  1. My horse, Docs Divine Dutchess went through a terrible ordeal with her eye. If my veterinarian hadn’t been so diligent and so correct with his treatment of her eye, she would have lost her sight. Since I planned to train her to show, this might have been a detriment to her career. She spent five weeks in the Lake Region Vet. Hospital but she did recover beautifully. Now, two years later she still has a small white scar in her eye. We know that she can see but must see things differently than she does with her left eye. Interestingly enough, this horse is far more comfortable with a rider than she is alone. She must like the security and guidance. Thanks for the wonderful article. I enjoyed it and learned from it!!

  2. My older Quarter Horse, Doc, also went through something like this. He got a piece of hay in his eye like a splinter and ended up with an ulcerated cornea. It took weeks of treating with the topical antibiotics, the blood draws and serums, and atropine four times a day but his ulcer, which grew up to nearly a centimeter across, finally healed leaving a small white scar. His vision was obstructed by that for about two years but it’s nearly gone now and as far as I can tell he can see clearly. Quick and aggressive treatment was definitely important in saving Doc’s eye.

  3. Nine years ago my 13 year old horse developed the same symptoms of tearing and closing the eye. I knew eye injuries were serious with horses but we were on a camping trip, and I waited till I got home to get her to a vet. Upon treating her for a week with all the appropriate drops, etc.,it was determined that she needed more help or she would loose the eye. I took her right away to the University of Florida vet school where they did surgery almost immediately and did a corneal transplant. Then she was in critical care for several weeks at another care facility. She ultimately came out if it with just a scar on her eyeball and still has vision, although she has to see around the scar. I never put her in the pasture anymore without a fly mask. I am so grateful for the excellent surgeon and caregivers at USF Vet School. I still have a beautiful horse.

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