Your pet has been diagnosed as having Dry Eye Syndrome (DES). This disease occurs when your pet’s tear production falls below normal and the eye is left without the protective and nutritional benefits of a good tear film.
The tears perform many functions to help protect the eye. They lubricate the surface of the eyelids to prevent friction from disturbing the cornea (the clear surface of the eye). The help was away dust, debris, and bacteria that may enter the eye. They inhibit the growth of bacteria and they provide nutrition to the cornea itself. When the tears are deficient, the eyes are subject to increased incidence of bacterial infection, ulceration and degeneration.
What are the symptoms of this disease?
DES can vary in its severity. In its mildest form, your pet’s eyes may seem simply reddened and inflamed. As the tear level drops further, you may start to see large amounts of mucus accumulate on the eyes and in the corners of the eyelids. This is due to the fact that tears are made of three layers; water, mucus and oil. About ninety percent of the tears are formed by water. In DES, it is the watery portion of the tears that is most often deficient. Without the watery component, the mucus and oil are left behind to form the discharge that you see.
With time, the lack of tears may allow the growth of bacteria and the discharge may begin to look greenish yellow and pus-like. Many times, the clear cornea will begin to turn black in response to the chronic inflammation caused by the dryness. Ultimately, this pigment may become so dense as to cause blindness in the eye.
Since the cornea is not getting adequate nutrition from the tears, it becomes weakened and may become easily scratched and ulcerated. This tends to be quite painful and you may see your pet squint and/or rub at his/her eyes. If left untreated, the ulcer may penetrate the entire cornea and the eye may be lost.
What causes Dry Eye Syndrome?
There are many theories and many possible causes for DES. The tear glands may get infected or inflamed and stop making tears. In other cases, the body’s immune system may attack the tear glands and cause them to stop working. Finally, in some cases various drugs may cause the decrease in tear production. Sometimes the damage to the gland is temporary, while other times it is permanent. Unfortunately, there is no way of telling how any one animal will respond to therapy in advance of treatment.
What can be done to treat Dry Eye Syndrome?
There are 4 goals to therapy of DES:
- Artificially replace the tear film in the short and sometimes long term.
- Treat the bacterial infection if present
- Decrease the inflammatory reaction in the cornea.
- Stimulate increased tear production.
The first goal is achieved by using artificial tear ointment at least and hopefully 4 times daily. This will protect the cornea and help lubricate the eyelids. Bacterial infections are controlled with the appropriate antibiotic solutions or ointments. The inflammatory reaction (redness, swelling and increased pigment) is controlled with anti-inflammatory drugs such as steroids or cyclosporine. Tear production may be stimulated with an oral drug (pilocarpine) and/or with topical cyclosporine.
It is important to realize that DES is usually a disease that is not totally cured. Instead, with the aid of the drugs listed above, our veterinarians aim to control the disease to maintain your pet’s comfort and good vision. If the administration of drugs 3 and 4 times daily is unfeasible for you, or it does not meet these goals, there is a surgical procedure which can be performed which transplants the salivary gland from the mouth into the eyelid and provides saliva to the eyes as an alternative to true tears.