The uveal tract is a continuous vascular structure consisting of the iris, ciliary body, and choroid. It is convenient to subdivide inflammation of the uveal tract into anterior uveitis (iritis and iridocyclitis) and posterior uveitis (choroiditis and choroidoretinitis). This chapter relates to anterior uveitis or, more simply, iritis; for the related entity chorioretinitis please also see Chapter 14, Retinitis.

Exogenous iritis may follow injury or surgery to the eye or may have a local intraocular cause, which usually is obvious from history or examination. Endogenous iritis may be regarded as a symptom of some widespread infection or multisystem disorder.

Iritis may be the presenting feature of a systemic infection or merely “another organ” involved by an already diagnosed infection. However, the ocular fluids are relatively easily obtained and their analysis can prove very useful when specific diagnosis of the offending organism has proved elusive. In the clinical setting iritis may be part of an acute or chronic systemic infection or be an immune response to a preceding systemic infection. The presentation of the iritis depends on both the immunity of the patient as well as the nature and the virulence of the organism. On occasions the iritis is the only sign of the infection which is entirely localized to the eye.