CMV RETINITIS & AIDS RETINOPATHY
Vitreoretinal News for the Medical Community
Early CMV retinitis may resemble cotton wool spots but close observation reveals expansion of margins on serial examinations.
Cytomegalovirus (CMV) retinitis is the leading cause of blindness in patients infected with the human immunodeficiency virus (HIV). Nearly 40% percent of patients will develop CMV retinitis during their lifetime. Cytomegalovirus, a herpes family virus, produces a hemorrhagic retinal necrosis with a "pizza pie" appearance. The lesions of CMV retinitis are characteristic; ophthalmoscopy alone provides a nearly pathognomonic diagnosis. It is rare that microbiologic or histologic confirmation is necessary.
Cotton wool spots and retinal hemorrhages are termed AIDS retinopathy and are quite common in HIV-seropositive patients. They must be differentiated from infectious retinitis. Cotton wool spots usually measure 1/4 to 1/2 disc diameters in size, do not enlarge with time, and often fade within four to six weeks. Early CMV retinitis may resemble cotton wool spots but close observation reveals expansion of margins on serial examinations. Venous sheathing, a mild vitritis and distinctive granularity are also features of CMV retinitis; not seen in AIDS retinopathy. If vitreous cells are present then a careful search of the entire retina is required since CMV frequently begins in the peripheral retina. Ocular syphilis is also common in HIV infected individuals and may manifest a mild vitritis.
AIDS retinopathy usually occurs prior to CMV retinitis however, both may be present at the same time. The CD4 count is a useful marker for CMV retinitis. occurring at a much higher frequency in patients having CD4 counts below 50. This is important since fundus examinations can be scheduled appropriately. A good rule-of-thumb is to examine patients with no retinopathy and high CD4 counts every 6 - 12 months and patients with AIDS retinopathy and low CD4 counts every 3-4 months. Of course, if patients complain of relevant symptoms such as floaters, smoky vision, decreased vision or peripheral visual field defects then an examination should be performed promptly.
Therapy for CMV retinitis requires either ganciclovir or foscarnet. Both are quite effective in stabilizing CMV retinitis. Ganciclovir is usually better tolerated and often the first line drug. Induction is given as 5 mg/kg twice daily for two to three weeks and then reduced to maintenance at 5 mg/kg once daily thereafter. Bone marrow toxicity can produce neutropenia therefore careful monitoring of white blood cell levels is essential. Foscarnet can also be used as a first line drug and is also active against HIV. Induction is given as 60 mg/kg TID followed by maintenance at 90-120 mg/kg daily. Renal toxicity requires good hydration and must be discontinued if creatinine levels rise. Cidofovir,a new investigational drug, is currently being used at CRC to treat those patients showing resistance to either ganciclovir or foscarnet. Ganciclovir may also be delivered by a slow release implant sutured in the vitreous cavity. This device lasts approximately 8 months and is very effective. It does not protect the contralateral eye and there is a higher incidence of retinal detachments.
