Cats

Keratoconjunctivitis Sicca

Keratoconjunctivitis sicca (KCS), also called keratitis sicca, xerophthalmia, dry eye syndrome, or simply dry eyes, is an eye disease caused by decreased tear production or increased tear film evaporation commonly found in humans and small animals. Keratoconjunctivitis sicca is Latin and the literal translation is "dryness of the cornea and conjunctiva".

The disease in humans

Symptoms

In humans, the typical symptoms of keratoconjunctivitis sicca are burning and a sandy-gritty eye irritation that gets worse as the day goes on. The symptoms are often caused by a loss of water from the tears that results in tears that are too "salty" or hypertonic.

Treatment

The best treatment strategies are designed to rehydrate the tears and eye surface, and include hypotonic, electrolyte-balanced tears, punctal plugs, and moist chamber spectacles. The inflammation that occurs in response to tears film hypertonicity can be suppressed by mild topical steroids or immunosuppressants such as cyclosporine, but these treatments have not been shown to help symptoms.

Causes

Keratoconjunctivitis sicca usually occurs in people who are otherwise healthy. It is more common with older age, because tear production decreases with age. In rare cases, it can be associated with rheumatoid arthritis, lupus erythematosus, Sjögren's syndrome and other similar diseases. It may also be caused by thermal or chemical burns, or (in epidemic cases) by adenoviruses. A number of studies have found that those with diabetes are more at risk for KCS. (PMID 15767060, PMID 15663232, PMID 15218664)

The disease in dogs

Keratoconjunctivitis sicca is common in dogs. Most cases are caused by a genetic predisposition, but chronic conjunctivitis, canine distemper, and drugs such as sulfasalazine and trimethoprim-sulfonamide also cause the disease. Symptoms include eye redness, a yellow or greenish discharge, ulceration of the cornea, pigmented cornea, and blood vessels on the cornea. Diagnosis is made by measuring tear production with a Schirmer tear test. Less than 15 millimeters of tears produced in a minute is abnormal.

Tear replacers are a mainstay of treatment, preferably containing methylcellulose or carboxymethyl cellulose. Cyclosporine stimulates tear production and acts as a suppressant on the immune-mediated processes that cause the disease. Topical antibiotics and corticosteroids are sometimes used to treat secondary infections and inflammation. A surgery known as parotid duct transposition is used in some extreme cases where medical treatment has not helped. This redirects the duct from the parotid salivary gland to the eye. Saliva replaces the tears. Dogs suffering from cherry eye should have the condition corrected to help prevent this disease.

The disease in cats

Keratoconjunctivitis sicca is uncommon in cats. Most cases seem to be caused by chronic conjunctivitis, especially secondary to feline herpesvirus. Diagnosis, symptoms, and treatment are similar to dogs.

References

• Gelatt, Kirk N. (ed.)(1999). Veterinary Ophthalmology (3rd ed.). Lippincott, Williams & Wilkins. ISBN 0-683-30076-8

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