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Vet Advice: Dry Eye
Diagnosing and dealing with a common canine ailment
Burwell, Vet Advice for Dry Eye

My first patient of the day is a soft, five-year-old Cavalier King Charles Spaniel named Chelsea. She peers suspiciously at me through half-open eyelids as her family describes the goopy eye discharge that goes away with topical medication but recurs as soon as treatment is discontinued.Chelsea’s not interested in playing ball as much as before, and spends most of her time curled up in her bed snoozing—behavior hardly expected from a champion ball-catcher.

I take a closer look at her eyes with my slit lamp and see thin blood vessels growing within what should be crystal-clear corneas. Instead, they’re a hazy gray, and the conjunctiva—the mucous membrane that covers the exposed portion of the eyeball and lines the inside of her eyelids—is red and puffy. I use special little paper strips divided into millimeter increments to measure Chelsea’s tear production and find that she has less than a third of what she should have. I then apply a topical stain that coats her cornea in a rough and patchy pattern. The combination of Chelsea’s clinical history, her eye exam and the test results gives me a diagnosis: keratoconjunctivitis sicca (KCS), also known as “dry eye.”

KCS is just one of the diseases that can affect the precorneal tear film that keeps the cornea and surrounding eye tissues healthy. The precorneal tear film provides oxygen and nutrition to these tissues and carries away debris from the surface of the eye. Much of the time, KCS is caused by an immune-mediated problem that creates inflammation within the tear glands and reduces the amount or quality of the tears they produce.Some drug interactions and systemic health conditions such as hypothyroidism may also affect the tear film, as can damage to the nerves that stimulate these glands to work properly. Additionally, the movement of the eyelids spreads the tear film across the cornea, so a dog’s inability to fully blink can also affect eye health.

Any dog can develop KCS, but some breeds seem to be predisposed. Shih Tzus, Lhasa Apsos, and Pugs top the list in my practice, but it’s also common in English Bulldogs, Westies, Cocker Spaniels, Yorkies, Pekinese, Boston Terriers and Cavaliers like my new friend Chelsea. The brachycephalic (squishedfaced) breeds often have big buggy eyes that are more exposed to the world, so they need even better tear production and quality than a breed with deeper-set eyes, such as a Standard Poodle or Collie.

What happens if your dog doesn’t produce enough tears? Just like Chelsea, he can develop red, irritated eyes that are painful and inclined toward bacterial infections and corneal ulcerations. Superficial corneal ulcerations can rapidly turn into deep ones that need surgical treatment to save the eye. If KCS is left untreated, the cornea will often become cloudy, with scarring over the surface and blood vessels growing across it. The corneal surface can even pigment and become so opaque that it obstructs vision. Fortunately, there are medications available to control the immunemediated inflammation within the tear glands.Notice I said control, not cure. By suppressing the inflammation in the tear glands, the medication allows your dog to produce more of his own tears.

The most important factors in treating KCS are consistently applying the medications as prescribed and following up with your veterinarian to determine if the treatment plan is working as expected. Don’t give up if you don’t see instant improvement; it may take several weeks of consistent application of medication before you see a difference. Chances are your dog will respond to medication relatively quickly: Don’t stop, reduce or change the medication until you follow up with your veterinarian. Your dog will look better because you’re treating the KCS, not because the KCS is cured. Stopping the medication allows the inflammation to recur, and you’ll have to start all over again. Keep repeating this cycle and those poor little tear glands may scar to the point where they can’t produce the tears needed even with treatment.

As for Chelsea, she went home with medication, and I received a call a couple of weeks later reporting that she was back to her energetic, ball-playing self. That’s news that keeps me happy!

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This article first appeared in The Bark,
Issue 57: Nov/Dec 2009

Rebecca Burwell, DVM, DACVO, practices with Eye Care for Animals in Santa Rosa and Corte Madera, Calif.

Photograph by Joe Potato

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