The Latin term for dry eye is keratoconjunctivitis sicca (KCS). KCS arises from inadequate production of watery tears. A potential cause of KCS in dogs is an autoimmune mediated inflammation of the tear glands. Certain drugs can also be toxic to the tear glands, especially sulfa drugs. In some breeds of dogs, congenital underdevelopment of the tear glands can lead to KCS. Trauma and damage to the facial nerve can also cause KCS.
With KCS, drying and inflammation of the surface tissues of the eye can occur. The conjunctiva and cornea become red and inflamed. The cornea may become pigmented and scarred, with decreased vision. Corneal ulceration may also occur. Mucous and oily secretions can build up around the eye and cause the eye to become infected. A classic sign of dry eye is thick ocular discharge. If the onset of KCS is sudden, the eye is often painful. The nostril on the same side may be dry and filled with thick material. The eyelids may be crusted over with discharge.
KCS is confirmed by measurement of tear production using the Schirmer tear test. This is an easy test to perform in the doctor’s office. It takes approximately two minutes. A strip of paper is placed under the eyelid that measures the tear production. In KCS, the strip of paper shows a lack of tear production.
The main goal in treatment is to increase tear production. Cyclosporine is a drug that is commercially available that stimulates tear production. Another drug that is commonly used is called tacrolimus. Either of these drugs are administered twice daily, indefinitely. Tear production is measured two to three weeks after medication is instituted. Artificial tears are also used to keep the eye well-lubricated. Topical antibiotics and anti-inflammatory drugs are often prescribed to combat the severe inflammation and secondary infections due to this condition.
Periodic rechecks, with repeated tear tests, are required for the life of the animal. Continuous and diligent treatment by the owner is key to managing this disease. KCS is usually a lifelong, chronic disease that is controllable but rarely curable.
Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.