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The cornea is the dome-shaped window in the front
of the eye. It is optically clear, living tissue that is shaped
precisely so as to focus light on the retina (the nerve layer lining
the back of the eye). Corneal clarity results from having no blood
vessels, and from the regular and precise arrangement of its microscopic
tissue fibers. The cornea is one of the most pain-sensitive tissues
in the body.
The cornea is prone to infection and inflammation
not generally found elsewhere in the body. Bacteria, fungi, parasites
(ACANTHAMOEBA), viruses (HERPES) and autoimmune processes can cause
corneal inflammation (known as KERATITIS). The same autoimmune processes
that cause scleritis can also cause inflammation of the edge of
the cornea, a problem known as PERIPHERAL ULCERATIVE KERATITIS.
Peripheral ulcerative keratitis that is not caused by infection,
and is not caused by a recognized autoimmune process is known as
MOOREN'S ULCER.
Corneal inflammation can result in thinning or
this tissue, occasionally to the point of perforation. At the very
least, inflammation disturbs the microscopic architecture of the
cornea, creating a scar which may distort the normal shape and clarity,
resulting in visual decline.
Treatment of keratitis begins with determination
of the cause. Scrapings from the corneal surface for cultures or
other studies are often helpful for diagnostic purposes, and blood
tests are used to evaluate for autoimmune disease. Corneal infections
require high concentration antimicrobial eyedrops used very frequently
(sometimes every hour), and sometimes oral therapy as well. Autoimmune
corneal infections are treated with systemic medications, similar
to the treatment of scleritis.
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