Ganciclovir capsules are used to treat cytomegalovirus (CMV) retinitis (eye infection that can cause blindness) in people whose immune system is not working normally. Ganciclovir capsules are used to treat CMV retinitis after the condition has been controlled by intravenous (injected into a vein) ganciclovir. Ganciclovir is also used to prevent cytomegalovirus (CMV) disease in people who have acquired immunodeficiency syndrome (AIDS) or who have received an organ transplant and are at risk of CMV disease. Ganciclovir is in a class of medications called antivirals.