Definition of Uveitis:

Uveitis is swelling and irritation of the uvea, the middle layer of the eye. The uvea provides most of the blood supply to the retina.

Causes, incidence, and risk factors:

Uveitis can be caused by autoimmune disorders such as rheumatoid arthritis or ankylosing spondylitis, infection, or exposure to toxins. However, in many cases the cause is unknown.

The most common form of uveitis is anterior uveitis, which involves inflammation in the front part of the eye. It is often called iritis because it usually only affects the iris, the colored part of the eye. The inflammation may be associated with autoimmune diseases, but most cases occur in healthy people. The disorder may affect only one eye. It is most common in young and middle-aged people.

Posterior uveitis affects the back part of the uvea, and involves primarily the choroid, a layer of blood vessels and connective tissue in the middle part of the eye. This type of uveitis is called choroiditis. If the retina is also involved, it is called chorioretinitis. You may develop this condition if you have had a body-wide (systemic) infection or if you have an autoimmune disease.

Another form of uveitis is pars planitis. This inflammation affects the narrowed area (pars plana) between the colored part of the eye (iris) and the choroid. Pars planitis usually occurs in young men and is generally not associated with any other disease. However, some evidence suggests it may be linked to Crohn's disease and possibly multiple sclerosis.

Uveitis can be associated with any of the following:

• AIDS
• Ankylosing spondylitis
• Behcet syndrome
• CMV retinitis
• Herpes zoster infection
• Histoplasmosis
• Injury
• Kawasaki disease
• Psoriasis
• Reactive arthritis
• Rheumatoid arthritis
• Sarcoidosis
• Syphilis
• Toxoplasmosis
• Tuberculosis
• Ulcerative colitis