October 23, 2017

Dry Eye in Dogs

A close look at keratoconjunctivitis sicca, including research on new treatments that could be curative for this uncomfortable and often chronic condition.
By Don Vaughan

The condition can also be caused by certain medications, such as sulfa drugs; trauma; and environmental conditions. Dr. Gilger noted that dogs living in dry, dusty, windy regions are at greater risk for developing dry eye than are dogs living in less extreme environments. Dogs that enjoy sticking their head out of the car window during drives are also at greater risk.

Dry eye can have a dramatic impact on a dog’s quality of life, which is why it should be diagnosed and treated as early as possible. Mildly uncomfortable in the earliest stages, untreated dry eye can lead to blindness as a result of corneal fibrosis, corneal pigmentation, and potentially excruciating abrasions and corneal ulcerations that can become infected and eventually perforate, Dr. Henriksen said. In addition, the continuous mucoid discharge associated with dry eye can make it extremely difficult for a dog to see clearly, which is why regular cleaning is recommended.

Diagnosis and Treatment
A diagnosis of dry eye is typically based on observed signs, such as mucoid discharge and tissue inflammation, and can be confirmed with certainty using the Schirmer tear test. This simple test involves placing a small piece of filter paper on the patient’s eye for 1 minute and measuring the amount of tears that are produced. Minimal tear production usually confirms dry eye.

Treating dry eye in dogs depends on the type and severity of the condition. In most cases, treatments are very similar to those used in humans. “Mild tear deficiencies can usually be well managed with an OTC lubricant, or artificial tears,” which is the go-to treatment for people as well, observed Dr. Gilger. “It’s a little bit more challenging in a dog,” he added, “because dogs don’t express very well when they have mild irritation, so owners tend to undertreat their pets when using artificial tears.”

Veterinarians usually become involved when dry eye progresses from mild to moderate or severe. The standard of care in such cases is immunosuppressant drugs, such as cyclosporine and tacrolimus, which are typically administered once or twice a day to restore function in the lacrimal glands.

“Cyclosporine has been around for nearly 30 years and is kind of the hallmark treatment that showed that dogs and humans are similar when it comes to this condition,” Dr. Gilger said. “Restasis [a treatment for dry eye in humans] is a form of cyclosporine that was first used in dogs years ago, then was developed for use in people. And since then, almost every product approved for people has gone that route, including lifitegrast, which is the newest drug approved for people.”

A higher concentration of immunosuppressive medication is often required because dogs don’t take up the medication quite as well as people, added Dr. Henriksen. Restasis, for example, contains 0.002% cyclosporine compared with 0.2%, and even up to 1% or 2%, in veterinary compounds.

Research is ongoing into implantable drug-release devices that would eliminate the need for daily drops. At the NCSU College of Veterinary Medicine, for example, Dr. Gilger is involved in the study of a ring that fits under the eyelids and gradually releases an immunosuppressive drug over a period of months. “It’s a very practical approach,” Dr. Gilger said. “The rings are very well tolerated, and so far the results have been promising.”

In addition to immunosuppressive medications, an anti-inflammatory drug may be used temporarily to reduce redness and irritation. However, veterinarians should ensure that the patient does not have ulcerations when prescribing a corticosteroid because of the potential for harmful side effects, Dr. Henriksen warned. When in doubt, she suggested consulting with a veterinary ophthalmologist.

If medication fails, there is a surgical option, said Dr. Gilger—transposing a salivary gland from the patient’s mouth to the affected eye. “The gland will produce a very watery saliva that acts like tears and can make a huge difference in the quality of life for dogs that don’t respond well to other treatments,” Dr. Gilger noted. “It’s a last-resort surgery, but it’s very effective.”

Promising New Research
There are, Dr. Gilger added, some intriguing areas of research regarding the treatment of canine dry eye, including the use of stem cells and gene therapy. “We know that stem cell therapy can help promote the redevelopment of normal lacrimal gland function,” he said, “and we have some ability to provide gene therapy, which can help induce a more natural ocular surface and promote better dry-eye care. The beauty of these therapies is that they are potentially curative; it’s not just about managing the disease.”

Once treatment has been prescribed, it’s the doctor’s role to ensure that the client is compliant when the patient goes home. “Most of my clients are not only very compliant, but [they are] highly motivated people,” Dr. Gilger said. “Care can be a huge challenge, however, because they must give their pets medication every day and return for follow-up exams. Although the medications are not expensive, it’s an ongoing cost because dry eye is usually a chronic condition and sometimes clients can’t afford it or they don’t have the time to treat their pets as frequently as needed. In cases like that, the patient will have persistent discomfort and ultimately could lose its vision. I’m sure there are a lot of dogs out there that lose their eyesight or are euthanized because they are persistently uncomfortable.”

Working in teaching hospitals, Drs. Gilger and Henriksen see dry eye on an almost daily basis—far more frequently than most veterinarians in private practice. Dr. Gilger encourages community practitioners to consider dry eye and test for tear production whenever they see a patient with ocular discharge and redness.

“Sometimes it can take veterinarians several months to make a definitive diagnosis just because they haven’t thought about dry eye,” he says. “The eye doesn’t have to look physically dry for the dog to have dry eye; it can be just slightly dry.”

 
Don Vaughan is a freelance writer based in Raleigh, North Carolina. His work has appeared in Military Officer, Boys’ Life, Writer’s Digest, MAD, and other publications.

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