Dry Eye

Q My 11-year-old dog has begun to have problems with his eyes lately. Most mornings, they are almost glued shut with a thick, yellow discharge. I took him to the vet and he said the dog has "dry eye." He then prescribed three different eye medications. I am very concerned. Will my dog go blind? Can he be cured? If so, how long will I have to treat him before he is restored?

A It sounds as though your dog is afflicted with keratoconjuctivitis sicca, also known as KCS or "dry eye." In this particular condition, the eye does not produce a sufficient amount of the amount of aqueous (watery) portion of the tears to keep the eye properly lubricated. It is a common condition in older dogs and in older people. Certain breeds are predisposed to KCS because of the shape of their eyes and how they sit in the sockets. For instance, Pugs and Shih Tzu both have large, protruding eyes and are especially susceptible. Previous eye surgery may also predispose the dog to dry eye later on in life.

The normal tears of a dog consist of the aqueous (watery) portion secreted by the lacrimal glands, and the lipid (oily) portion secreted by the meibormian glands. When properly mixed, the tears form a thin coating, or film, that covers all of the exposed portion of the eyeball. When this film becomes insufficient to keep the eye moist, the cornea dries out. The eye then becomes uncomfortable and will eventually develop corneal damage, scarring, and finally blindness. The lipid portion of the tears continues to be secreted and forms a thick, pus-like substance which can "glue" the eyelids closed. In humans, dry eye is treated with artificial tears, applied in drop form whenever the patient feels the eye becoming dry, normally every hour or so. For most dogs, however, this type of schedule is impractical, unless the animal's caregiver is with the patient all during the day. In all other cases, the cornerstone of treatment for dry eye is a drug called cyclosporine, originally marketed as an anti-cancer agent. When it is diluted in oil and applied to the surface of the eye, it frequently stimulates the existing gland(s) to produce tears again.

Cyclosporine does not work for all patients with KCS, but when it does, it is a real miracle cure. Many dogs are then able to maintain vision for years with a single or twice daily application of cyclosporine. Other medications may also be prescribed, such as antibiotics, corticosteroids, or artificial tears to combat concurrent ocular conditions.

There have been some reports of adverse side effects to treatment with cyclosporine (many only after years of successful therapy) so if your dog is being treated with this agent and seems to develop health problems, contact your regular veterinarian as soon as possible. There are a few patients which simply cannot tolerate the prescription in any dosage.

"Cherry eye" is a common inherited condition in some breeds in which the nictitans gland becomes enlarged and projects from under the lower eyelid. It is very unsightly and is usually treated surgically. Historically, the surgery involved total removal of the offending gland, and it was a very quick and simple procedure. Unfortunately, many of these patients developed dry eye later on in life. It was soon discovered that the nictitans gland was an important organ involved in proper tear production which needed to be preserved.

The surgical procedures employed today entail "tucking away" the errant gland and suturing it in place. It is much more difficult and time consuming (i.e. costly) than before, but also much better for the dog in the long run.
KCS can also be caused by a reaction to medications. Sulfonamide antibiotics have been implicated as contributors to this condition.
In summary, KCS (or dry eye) is a condition caused by decreased tear production. Previous eye surgeries or genetic predisposition may influence the manifestation of the syndrome. Most cases are controllable with regular treatment. Except for some instances of drug or allergic reactions, KCS generally requires lifelong management.

by Cynthia Smith, DVM, Reprinted from the ASTC Bulletin