If a dog’s eyesight declines, they may not make noticeable visual mistakes or show signs of discomfort since they primarily rely on smell to navigate the world. Because of this, pet owners need to keep a watchful eye out for common canine ocular diseases, such as dry eye.

An extremely uncomfortable disease, canine dry eye refers to the inflammation of the cornea — or the transparent outer layer of the eye — and the surrounding area caused by an inability to produce a proper amount of tears.

In order to fully understand what causes dry eye, Dr. Lucien Vallone, a clinical associate professor of ophthalmology at the Texas A&M School of Veterinary Medicine and Biomedical Sciences, says that pet owners should first be aware of the role that the tear film plays in the development of dry eye, especially for short-faced dogs who are more susceptible, such as Boston terriers, pugs and shih tzus.

Made of oil, water, and mucus layers, the tear film covers the eye’s surface, protects it from the environment, prevents natural tears from evaporating, and maintains clear eyesight by focusing light properly.

According to Vallone, inflammation and progressive damage to the tear film is considered to be the leading cause of dry eye.

“Common inflammatory culprits like tear film evaporation, trauma, and hair that surrounds the eye rubbing on the eye’s surface can influence tear-producing glands in a negative way, lessening the quantity and quality of the tear film,” Vallone said.

Damage to the tear film also influences dry eye symptoms.

For example, if the water-like quality of the tear film deteriorates and does not produce an adequate amount of tears to keep the eye moist, the eye will make up for it by producing more mucus than normal. Vallone suggests that owners, especially those with more susceptible breeds, be vigilant in watching out for signs of mucus discharge, including crusting around the eye and matting of eyelashes and eyebrows.

“Dogs with dry eye also display signs of inflammation, including pain and redness,” Vallone said. “Pain is apparent when squinting or rubbing is observed, and a distinctive red-eye appearance is caused by reddened conjunctiva (normally the white part of the eye) and new blood vessel formation in the cornea.”

It is crucial for owners to be aware of dry eye symptoms so that they can seek veterinary care for treatment; otherwise, they may risk their dog’s eye health declining further.

“Treatment is most successful when started very early in the disease course, when symptoms begin,” Vallone said. “Otherwise, untreated dry eye can have devastating effects on vision and eye comfort.”

The combination of untreated dry eyes and poor eye health can cause corneal ulcerations, or open sores on the cornea, to spontaneously occur. These corneal ulcers typically require significant medical intervention.

“Corneal ulcers are at an increased risk of infection due to the poor health of the eye’s surface, and this combination of factors brings many dry eye patients into the emergency room for corneal ulcers that often need to be repaired surgically,” Vallone said. “Sadly, some eyes are removed due to severe complications of dry eye.”

However, if owners visit their veterinarian as soon as they notice dry eye symptoms, the veterinarian can confirm the condition and provide treatment for their dog.

“The diagnosis can be confirmed quickly during the course of a physical examination with a veterinarian, who completes a Schirmer Tear Test to assess the tear film,” Vallone said.

The Schirmer Tear Test uses a dry strip of paper that is placed against the eye for a specified amount of time; afterwards, the veterinarian will determine how much moisture is on the paper in order to provide a diagnosis.

If a dog is diagnosed with dry eye, the most common treatment is to apply tear stimulant medications to the eyes twice a day for the remainder of a dog’s life, since there is no cure for canine dry eye, according to Vallone. But these tear stimulants, which are prescribed by veterinarians for dogs, are meant to reduce inflammation and stimulate tear production, easing the symptoms of dry eye and preventing major health complications associated with the condition.

By being mindful of dry eye symptoms, owners can ensure that their furry friend can receive treatment before the disease progresses to a more detrimental stage. Identifying symptoms and taking your dog to their veterinarian early will help bring a happy and healthy lifestyle for your pet into focus.

Pet Talk is a service of the School of Veterinary Medicine and Biomedical Sciences, Texas A&M University. Stories can be viewed on the web at vetmed.tamu.edu/news/pet-talk. Suggestions for future topics may be directed to vmbs-editor@tamu.edu.