inflammation of the uvea, the middle coat of the eyeball, which is pigmented and contains blood vessels. The uvea consists of three parts: the iris, the ciliary body (containing the muscle that controls the curvature of the lens), and the choroid, the layer of the eyeball between the retina and the sclera (the white outer covering of all except the front part of the eyeball). Anterior uveitis affects only the iris or the ciliary body, or both; posterior uveitis, the choroid. Uveitis is also classified by whether or not it is granulomatous—that is, whether or not there is persistent inflammatory tissue with a granular surface.

Granulomatous uveitis causes impairment of vision, pain, watering of the eyes, and sensitivity of the eyes to light; the nongranulomatous type also causes impairment of vision, but there is less pain and less sensitivity to light. Eventual complete recovery occurs far more often in the nongranulomatous type than in the granulomatous.

Causes of uveitis include systemic infections (e.g., measles, syphilis, and tuberculosis), other systemic diseases (e.g., rheumatoid arthritis), and allergic reactions. In many cases no particular cause can be identified.

Anterior uveitis is called iritis if the inflammation is confined to the iris, cyclitis if it affects only the ciliary body, and iridocyclitis if both structures are involved. Anterior uveitis causes contraction of the pupil and deposition of clumps of cells on the iris and the cornea. The pupillary edges of the iris may adhere to the lens, impeding the flow of the aqueous humour. The resultant increased pressure within the eyeball may injure the optic nerve and cause blindness (see glaucoma). Posterior uveitis usually affects the retina. Blurring of vision results from the retinal involvement and from debris in the vitreous, the jellylike substance that fills the rear portion of the globe. Complications include bleeding with growth of connective tissue into the vitreous, the clouding of the lens, and atrophy of the eyeball.

In some rare cases, there may occur a condition called “sympathetic ophthalmia,” in which symptoms of irritation occur not only in the injured eye but also, sympathetically as a hypersensitive reaction, in the uninjured eye. Insufficient or delayed therapy can result in blindness in both eyes.

Treatment of uveitis is directed toward elimination of infection, reduction of inflammation, and preservation of vision, including that of the eye that may have escaped the uveitis.