Uveitis is a general term that refers to inflammation of the part of the eye known as the uvea.
The uvea is a relatively thick, strong layer of fibrous tissue that encloses and protects the eyeball. It consists of three parts: the iris, the ciliary body, and the choroid.
There are three types of uveitis, classified according to the part of the uvea that is affected. Anterior uveitis, which affects the front part of the eye, is also sometimes called iritis since the iris is part of the front of the eye. Intermediate uveitis, also known as pars planitis or cyclitis, refers to inflammation of tissues in the area just behind the iris and lens of the eye. Posterior uveitis, also known as choroiditis, refers to inflammation of the choroid, the back part of the uvea. Posterior uveitis may affect the retina and/or the optic nerve, and may lead to permanent loss of vision.
Posterior uveitis is the rare form of the disorder and is the type of uveitis most associated with loss of vision. The other two forms are more common, and more frequently result in acute symptoms, but only rarely cause vision loss.