Keratoconjunctivitis Sicca
Dogs
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
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
diabetes
are more at risk for KCS[1]
[2]
[3].
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.
Breeds commonly affected by KCS
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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