Ganciclovir is preferred over acyclovir in the following condition
Ref-KDT 6/e 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.
Herpes simplex keratitis
Herpes zoster
Chicken pox
Cytomegalovirus retinitis in AIDs patients
Other topics and Adverse effects