**Originally published during my internship with the American Quarter Horse Journal in 2006.
Through the Equine Looking Glass
Corneal ulcers can do more damage than you think.
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.
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.
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.
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.”
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.
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.”