CMV retinitis is the most common intraocular infection in patients with AIDS and is estimated to affect 35 to 40 percent of patients with AIDS. Untreated CMV retinitis is a progressive disorder, the end result of which is total retinal destruction and blindness. As of September 1996, drugs approved by the United States Food and Drug Administration (FDA) for the treatment of CMV retinitis were ganciclovir (Cytovene), foscarnet (Foscavir), and cidofovir (Vistide). All systemically administered anti-CMV drugs are given in a similar fashion consisting of initial 2-week high-dose treatment (induction) to control the infection followed by long-term lower dose treatment (maintenance) to prevent relapse. Ganciclovir is available in both intravenous and oral formulations, foscarnet only in an intravenous formulation, and cidofovir is given by intermittent intravenous administration. A surgically implanted intraocular sustained-release ganciclovir device (Vitrasert) is also approved by the FDA for the treatment of CMV retinitis.