Dry Eye

Keratoconjunctivitis sicca (KCS) or “dry eye” is a very common ocular disorder affecting the cornea and conjunctiva of dogs and less commonly cats. This condition is the result of inadequate tear production. Normal tear production is essential to good ocular health, and a deficiency in tears can lead to serious and sometimes permanent eye problems. When left untreated, KCS can be a potentially blinding disease through severe corneal ulceration or pigmentation. However, it is relatively easy to diagnose with a Schirmer tear test strip and usually responds favorably to long-term medical therapy.

What are the signs of KCS?

Pets with KCS have reddened, irritated eyes, often with severe, crusty discharge caked on the eyelids. This discharge is frequently mistaken as excessive tearing, but it actually represents a complete absence of the water component of tears. The tear film is made up of water, fat, and mucus, and in dry eye, the lack of the water component leads to an abnormal accumulation of the fat and mucus components.

What causes KCS?

There are many causes of inadequate tear production. Among the more common include breed predisposition (inherited), immune mediated disorders (caused by the animal’s own immune system attacking the tear gland), neurogenic, use of certain drugs, and some systemic diseases. Breeds most often affected with KCS include West Highland Terriers, Bulldogs, Cocker Spaniels, Boston Terriers, Lhasa Apsos, and Shih Tzus. There is a tendency to see KCS more often in females than males, and it usually occurs in middle to older age dogs.

How is KCS treated?

KCS is usually a treatable disease, however, it requires a long-term commitment from the owner. The exact frequency of medication may vary, but often includes the use of a high quality tear film replacement compound or “artificial tears” to mimic the natural tear film. It may be necessary to instill these drops as often as every two hours in the early course of therapy. These artificial tears are usually used in conjunction with a drug called cyclosporin or tacrolimus.

KCS is a deficiency in the water component of the tears, leaving the fat and mucus components of the tears to accumulate on and around the eye.

When cyclosporin and tacrolimus are administered topically onto the eye, tear production will significantly improve in about 80% of all cases, depending on the cause of KCS. The exact mechanism by which cyclosporin and tacrolimus increase tear production is not fully understood, but we do know these drugs suppress the immune system locally at the tear gland, thereby limiting the damage to the tear production. When administered topically, they are considered to be very safe drugs with no systemic side effects reported.

The increase in tear production usually occurs within the first couple of weeks of therapy. An occasional “late responder” will start to increase tear production within an additional few weeks. Even when tear production returns to normal, therapy must be continued for the life of the patient. In certain cases, the frequency of the artificial tear therapy can be reduced or even discontinued once the full effects of the cyclosporin or tacrolimus have been realized. In many cases, the damage to the cornea and conjunctiva will significantly improve once the tear production is returned to normal.

What if my pet doesn’t respond to therapy?

For the few cases that do not respond to medical therapy, management can become very frustrating for you and your pet. Other treatment alternatives do exist. One option is a surgery called a parotid duct transposition, in which saliva is re-routed into the eye to serve as a replacement for tears. However, this surgery should be considered only after medical therapy has failed. If you would like to discuss additional treatment options for KCS, please contact your regular veterinarian or the Hope Center Ophthalmology Department for more details.