Most common eye problem in dogs
Tears have an important role in keeping the eye healthy. They cover the cornea and wash away debris and infectious agents. They even have germ-fighting properties! When the eye’s tear film—the thin but complex layer of fluid coating the eye—does not contain enough tears, dogs (and people) are subject to a condition known as “dry eye.” (The medical term for this condition is keratoconjunctivitis sicca.)
Dr. Bianca Martins, a board-certified ophthalmologist at the University of Illinois Veterinary Teaching Hospital in Urbana, says dry eye is the most common ailment she sees in dogs.
Signs and Causes of Dry Eye
“Dogs with this condition typically have red eyes from irritation as well as some thick mucoid discharge. They will squint frequently and may blink excessively or keep their eyes closed,” Dr. Martins says. Dry eye can be painful, so the animal may paw at the eye more than normal or shy away from the area being touched. These signs often occur in both eyes.
Dry eye usually shows up in dogs that are between 4 and 6 years old, but can happen at any age. Flat-faced breeds, such as shih tzus, pugs, and Boston terriers, are more likely to develop it.
There is a qualitative form of the condition, related to underproduction of a specific type of high-quality tear, but most dogs have a quantitative form of dry eye, in which the eye simply doesn’t produce enough tears.
“Dry eye is most commonly caused by an immune-mediated reaction of the lacrimal glands, the structures that produce tears,” Dr. Martins says. “Immune mediated” means that the body’s immune system attacks the lacrimal glands and shuts them down.
Other causes include certain medications, such as long-term administration of oral antibiotics that contain sulfonamide, and genetic factors, such as a gene that predisposes some dogs to be born with abnormally small glands.
Diagnosis and Treatment
“Most veterinary clinics are able to perform a Schirmer tear test to diagnose dry eye. The test is performed by placing a sterile paper strip on the surface of the eye to measure how much tear is present,” Dr. Martins explains.
If the strip determines that there is decreased tear production, then the dog has the quantitative form of dry eye. If this test does not reveal inadequate tears, a visit to a veterinary ophthalmologist may be required. A specialist can diagnose the qualitative form by using special stains on the cornea.
Treatment focuses on increasing the dog’s quality of life and making sure the dog isn’t in pain. Luckily, if dry eye is caught and treated early, the animal has a good chance of maintaining vision and eye comfort.
Artificial tear drops are sometimes used to treat dry eye, but because the drops don’t stay in the eye for long they aren’t very effective.
“The most common treatment option consists of medicated drops or ointment that goes directly on the affected eye or eyes,” Dr. Martins says. The medication works to decrease the body’s immune response and stimulate the lacrimal glands to produce tears again. Treatment takes up to 4 weeks to start working, and the dog will need the medication lifelong.
If medical therapy is not effective in the patient, doctors may perform a surgical procedure called “parotid duct transposition.” One of the ducts in the mouth that produce saliva is surgically moved to the eye. Although this transposed duct adds moisture to the eye, because the moisture differs from tears in its normal pH and mineral content, this procedure is not curative and leads to chronic problems. For this reason, the surgery is not often done.
Don’t Overlook Dry Eye
Pets that have red eyes or discharge should see a veterinarian right away. Not only does dry eye cause pain and impact the pet’s quality of life, but severe and life-long consequences may occur without prompt veterinary treatment.
“Chronic dry eye may lead to ulcers that may become infected and rupture,” warns Dr. Martins. “Without the proper lubrication on the eye, pigment will build up over the cornea and result in permanent blindness.”
If you have any questions about your pet’s eyes, please contact your local veterinarian.
By Beth Mueller
Feature photo of Dr. Bianca Martins, second from left, teaching a veterinary student to conduct an eye examination, by L. Brian Stauffer