Keratitis is an inflammation of the cornea, the transparent membrane that covers the colored part of the eye (iris) and pupil of the eye.

There are many types and causes of keratitis, which can occur in both children and adults. Germs can't usually invade a healthy cornea, but certain conditions can allow an infection to occur, such as a scratch or a very dry eye can decrease the cornea's ability to protect itself. Illnesses or other factors that reduces the body's ability to overcome infection, including cold sores; genital herpes; crowded, dirty living conditions; poor hygiene poor nutrition (especially a deficiency of vitamin A, which is essential for normal vision).

Herpes simplex keratitis is a major cause of adult eye disease, and may lead to chronic inflammation of the cornea, development of tiny blood vessels in the eye, scarring, blindness, or glaucoma.

The infection generally begins with inflammation...