A number of infectious diseases cause uveitis (see table Infectious Causes of Uveitis). The most common are toxoplasmosis, herpes simplex virus (HSV), and varicella-zoster virus (VZV). Different organisms affect different parts of the uveal tract.
(See also Overview of Uveitis.)
Toxoplasmosis
Toxoplasmosis is the most common cause of retinitis in immunocompetent patients. Most cases are acquired postnatally; however, congenital cases occur as well, particularly in countries where infection is endemic. Symptoms of floaters and decreased vision may be due to cells in the vitreous humor or to retinal lesions or scars. Concurrent anterior segment involvement can occur and may cause ocular ache, redness, and photophobia. Laboratory testing should include serum anti-Toxoplasma gondii antibody titers.
Patients with small peripheral lesions that do not directly threaten vital visual structures may be observed without treatment and should begin to show slow improvement in 1 to 2 months.
Paul Whitten/SCIENCE PHOTO LIBRARY
Herpesviruses: HSV and VZV
HSV causes anterior uveitis. VZV does so less commonly, although the prevalence of zoster-associated anterior uveitis increases with age. Both HSV and VZV can also result in posterior uveitis, although this is less common.
Symptoms of anterior uveitis include
Ocular aching
Photophobia
Decreased vision
Signs include
Redness
Conjunctival injection and anterior chamber inflammation (cells and flare), often accompanied by corneal inflammation (keratitis)
Decreased corneal sensation
Patchy or sectorial iris atrophy
Intraocular pressure may be elevated as well, in contrast to the low intraocular pressure typically associated with most forms of uveitis; elevation can be detected by using applanation tonometry with, for example, a Goldmann tonometer, a pneumotonometer, an electronic indentation tonometer, or, if these are not available, a Schiotz tonometer.
Acute retinal necrosis (ARN) is a rapidly progressing form of retinitis that is a much less common manifestation of VZV and HSV infection. ARN typically manifests as confluent retinitis, occlusive retinal vasculitis, and moderate to severe vitreous inflammation. One third of ARN cases become bilateral, and in three fourths of eyes, retinal detachment
Image courtesy of Sunir Garg, MD.
Herpesviruses: Cytomegalovirus
Cytomegalovirus (CMV) is the most common cause of retinitis in immunocompromised patients, but prevalence has decreased among patients with HIV/AIDS receiving antiretroviral therapy (ART). Currently, ≤ 5% of these patients are affected. Most affected patients have a CD4+ count < 100 cells/mcL. CMV retinitis may also occur in neonates and in pharmacologically immunosuppressed patients but is uncommon. CMV can rarely cause anterior uveitis in the immunocompetent person.
Symptoms of CMV retinitis include blurry vision, blind spots, floaters, flashing lights, and vision loss. However, infection is often asymptomatic.
SUE FORD/SCIENCE PHOTO LIBRARY
The diagnosis is largely clinical based on direct or indirect ophthalmoscopic examination; serologic tests are of limited use, although analysis of aqueous fluid can be confirmatory if the diagnosis is in question.
> 100 cells/mcL for at least 3 months). Patients with CD4+ counts < 50 cells/mcL, even if asymptomatic, should be monitored every 3 months for CMV retinitis.
