The iris and ciliary body together are referred to as the anterior uvea. The iris is the colored portion of the eyeball and is shaped like a flattened donut. It is the structure that controls the amount of light entering the eye. The opening of the iris (called the pupil) is controlled by a set of muscles. One muscle constricts (closes) the pupil and the other one dilates (opens) the pupil. The ciliary body lies immediately behind the iris. A portion of the ciliary body contains fibers that are attached to and support the lens. Another portion of the ciliary process contains blood vessels that secrete a watery fluid called aqueous humor. Aqueous humor is the fluid that lies between the cornea (the transparent front part of the eye) and the lens.

Anterior uveitis is an inflammation of the iris and the ciliary body.

There are numerous causes of anterior uveitis. Some of them include: corneal ulceration, infection, rupture of the lens, and autoimmune problems (allergic-type reaction). Trauma to the eye is the most common cause of anterior uveitis in dogs.

Regardless of the cause, clinical signs of uveitis are similar. Pain, constricted pupil, haze-like appearance of ocular fluid, tearing, and low intaocular pressure are all symptoms of uveitis.

A complete physical examination and history of the animal are essential for determining the cause of anterior uveitis. The history includes any previous eye problems and/or general illnesses. X-rays, blood tests, and urine analysis are often essential for obtaining a diagnosis. Often, a cause is never determined.

Treatment for uveitis is twofold. Nonspecific treatment is necessary in order to control pain and inflammation, and specific treatment is necessary to eliminate the cause.

Cats showing symptoms of uveitis should be tested for Toxoplasmosis.

Anterior uveitis is a major cause of blindness.