Tear production is essential to the health and well-being of the entire eye. The lacrimal glands nestled within the eyelids produce tears in order to lubricate and clean the cornea as well as to assist in normal immune functions.
When tear production is decreased, either because of a congenital defect in the lacrimal glands or because of an acquired decrease in normal tear gland production, the resulting condition is referred to as keratoconjunctivitis sicca ("dry eye" or "KCS").
Though it's not clear how this condition is inherited, some breeds of dogs are clearly predisposed to it. It can also occur in any dog as a result of viruses, inflammatory disease processes, drug-related side effects, or diseases that affect the immune system. Dogs whose "cherry eye" condition results in an ill-advised surgical removal of the gland are also predisposed.
Both eyes are almost always affected.
Symptoms and Identification
Dogs who suffer from KCS will typically have greenish, mucoid discharge (the result of an overproduction of mucus as a means to lubricate the eye in the absence of a normal quantity of tears). Redness of the structures surrounding the eye (namely the sclera and the conjunctiva) will also inevitably result. If not addressed quickly, the cornea may also become irritated and swollen, identifiable by a bluish cast of this structure.
If left untreated, bacterial infections of the conjunctiva and corneal ulceration (both due to the lack of the tears' protective mechanisms) will result, leading to chronic pain and irritation and, ultimately, the loss of the eye's integrity. Blindness is not uncommon for dogs whose KCS is allowed to progress unchecked.
Diagnosis of this condition is normally a simple affair. A test called the "Schirmer tear test" uses a small strip of paper to measure the quantity of tears produced by each eye. A dye is also employed during this diagnostic process to determine the integrity of the cornea.
Breeds affected include:
The [very rare] congenital form of KCS may be inherited in the Yorkshire Terrier, Pug, Pekingese, and Chihuahua.
The mainstay of KCS management involves the use of various eye drops to supply artificial tears and increase tear production. Cyclosporine is the most common drug of choice for the purpose of increasing tear production. Unfortunately, KCS cannot be cured; the drops must be continued for the entirety of a dog's lifetime.
Alternatively (though less successfully), a surgical approach may be employed to transpose a salivary duct to the eye margin and thereby achieve a modicum of lubrication. This approach is uncommonly undertaken.
If treatment is undertaken before corneal ulceration occurs, the cost of KCS is largely limited to the cost of its diagnosis (usually had for less than $100) and the medications required to treat it.
Unfortunately, the cost of the cyclosporine eye drops (the drug most commonly utilized) is not insignificant. Owners can expect to spend anywhere from $20 to $50 every month for the rest of the dog's life.
Dogs who suffer KCS should not be bred so as not to pass on this trait to any offspring. Otherwise, there is no known means of prevention.
Gelatt, K.N. 1991. Veterinary Ophthalmology. Lea and Febiger.
Salisbury, M.A. 1995. Keratoconjuctivitis sicca. In J.D. Bonagura and R.W. Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 1231-1239. W.B. Saunders Co., Toronto.