<prompt> Ganciclovir is preferred over acyclovir in the following conditionHerpes simplex keratitisHerpes zosterChicken poxCytomegalovirus retinitis in AIDs patients  <response>: Ref-KDT 6e p769 Ganciclovir is the drug of choice for CMV infections. Acyclovir is highly effective against Herpes simplex and Varicellal zoster chicken pox and herpes zoster but it has very little activity against CMV. 