Cytomegalovirus (CMV) retinitis is a slow-growing infection of the retina. It is the most common ocular opportunistic infection in patients with AIDS. In addition to occurring in patients with AIDS, CMV retinitis may be found in patients with solid-organ and bone-marrow transplants but is much less common in these populations.

With the introduction of antiretroviral therapy (ART) in 1996, there has been a 75% reduction in the number of new patients with CMV retinitis. Despite this marked decline in incidence, more than 20% of patients respond poorly to ART, are noncompliant, or do not tolerate the regimen. These patients represent a significant population that continues to be at risk for CMV retinitis.

CMV is a double-stranded DNA virus that is ubiquitous in the United States and is easily spread from person to person by direct contact. In healthy people, the virus remains subclinical, but in the immunocompromised, CMV can lead to infections of the lung (pneumonitis), gastrointestinal tract (colitis), brain (encephalitis), and retina (retinitis).

Patients may complain of floaters, blurred vision, or photopsia, but they are often asymptomatic. The retina shows a slowly expanding demarcated area of retinal necrosis and hemorrhage, often near the vasculature. CMV retinitis may respond well to treatment, but it may recur. There is also an increased risk of retinal detachment, which is difficult to repair and can lead to permanent loss of vision. 

Immune recovery uveitis can occur in some patients with pre-existing CMV retinitis after a good response to ART therapy. In these patients, vitreitis and optic disc edema can lead to chronic vision-limiting complications, including macular edema and epiretinal membrane.