Uveitis, the inflammation of the pigmented vascular layer of the eye, represents a major cause of visual impairment, responsible for up to 20% of cases of blindness.1,2 In part because most cases involve young adults, the economic impact of uveitis likely rivals that of diabetes-associated retinopathy.1
Complications include cataract, the growth of new retinal vasculature, scarring, and more rarely, cystoid macular edema, glaucoma and hypertension, and retinal detachment.3
Rare, often missed and relatively little-studied, uveitis’s associations with disease processes outside of the eye are poorly understood, despite well-developed laboratory animal research models.1,4 Cases may be either infectious (for example, resulting from Herpes virus, tuberculosis, or other pathogens) or, more commonly, noninfectious.5 Uveitis is therefore sometimes categorized as immune (infection)-mediated, or autoimmune, in nature.5 Immune-mediated uveitis results from innate immune inflammatory reactions to pathogens or tissue damage.5 Autoimmune cases result from the presence of autoantigens in the patient’s tissue that provoke immune attack.
Some rare localized eye diseases are also associated with uveitis. Sympathetic ophthalmia uveitis and birdshot chorioretinopathy are examples of local uveitis-associated diseases that are limited to the eyes. Birdshot chorioretinopathy is a genetic disorder strongly identified with major histocompatibility antigen HLA-A29.5 Sympathetic ophthalmia uveitis involves autoimmune granulomatosis in both eyes triggered by injury of either eye.5
Approximately 20% of autoimmune-uveitis cases are associated with systemic autoimmune diseases like juvenile arthritis, systemic lupus erythematosus, Crohn’s or Behçet’s disease, or sarcoidosis, but most cases of autoimmune uveitis are idiopathic—they have no established etiology.2 In rare cases, uveitis can be secondary to CNS lymphoma or another malignancy.5 Overall, the majority of cases (63%) of uveitis are autoimmune in nature, 18.5% are associated with systematic autoimmune disease, and 18.7% appear to be caused by eye infections.4,5
The International Uveitis Study Group (IUSG) classifies uveitis as anterior, intermediate, posterior, or panuveitis, depending on the extent and region(s) of primary ocular inflammation.1,6