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.