Keratoconjunctivitis sicca (KCS), also called
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
The disease in humans
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.
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.
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
are more at risk for KCS. (PMID
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
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.
Gelatt, Kirk N. (ed.)(1999). Veterinary Ophthalmology (3rd ed.).
Lippincott, Williams & Wilkins.