The eye is shaped much like a tennis ball, hollow inside with three different layers of tissue surrounding a central cavity. The outermost layer is the sclera (the white coating of the eye), and the innermost layer is the retina (the ultra thin, image-gathering tissue in the back of the eye). The middle layer between the sclera and the retina is called the uvea.
Uveitis is inflammation inside the eye, specifically affecting one or more of the three parts of the eye that make up the uvea. These are the iris (the colored part of the eye), the ciliary body (behind the iris, responsible for manufacturing the fluid inside the eye), and the choroid (the vascular lining tissue underneath the retina). Uveitis is the third leading cause of blindness in the U.S. Iritis is a form of anterior uveitis and refers to the inflamation of the iris of the eye.
What is the importance of the uvea?
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 and more serious than the more common inflammations of the outside layers of the eye.
Symptoms of uveitis
Symptoms include increased sensitivity to light, blurred vision, pain, and redness of the eye. Uveitis may be gradual in onset.
Causes of uveitis
Uveitis has approximately 60 different causes. It may result from a virus, a fungus, or a parasite. Uveitis can also be related to disease in other parts of the body, such as arthritis or an autoimmune disease, or come as a consequence of eye injury. Inflammation in one eye can result from a severe injury to the opposite eye (sympathetic uveitis).
In many cases, the cause is extremely difficult to discover and requires a hefty amount of "detective work." Often, the cause goes unknown.
Finding and diagnosing the cause of uveitis can be extremely difficult and may go far beyond a simple eye examination. Since most ophthalmologists do not deal on a daily basis with some of these forms of testing and disease diagnoses, consultation with other medical specialists may be helpful.
Prompt treatment is necessary to minimize any loss of vision. Eye drops, especially steroids and pupil dilators, are medications used to reduce inflammation and pain. For deeper inflammation, oral medication or injections may be necessary. If the uveitis is discovered to be caused by a systemic disease, treatment of that disease may relieve the uveitis.
Complications such as glaucoma, cataracts, or new blood vessel formation (neovascularization) also may need treatment in the course of the disease. If complications are advanced, surgery may be necessary.
Uveitis arising in the front or middle part of the eye is commonly more sudden in onset, generally lasting six to eight weeks. In their early stages, it can usually be controlled by the frequent use of steroid and pupil-dilator drops. Often this type of uveitis runs its course before any specific cause is found. Uveitis in the back part of the eye is commonly slower in onset and may last longer. It is also often more difficult to treat.