Uveitis is an inflammation of the uvea, the pigmented layer of the eye that includes the colored iris. The uvea contains many of the blood vessels which nourish the eye. Inflammation of the uvea can affect the cornea, the retina, the sclera, and other vital parts of the eye. Since the uvea borders many important parts of the eye, inflammation of this layer may be sight-threatening.
Uveitis has many different causes. It may develop following eye surgery or trauma. It may result from a virus (such as shingles, mumps, or herpes), a fungus (such as histoplasmosis), or a parasite (such as toxoplasmosis). Uveitis can also be related to autoimmunity. In most cases, the cause remains unknown.