Viral retinitis is a rare disease that implies involvement of Herpesviridae, a family of double-stranded DNA viruses characterized by latency within the host’s cells after the primary infection, according to J. Fernando Arevalo, MD, PhD, FACS.
Dr. Arevalo is the Edmund F. and Virginia Ball professor of ophthalmology, and chairman of ophthalmology, Johns Hopkins Bayview Medical Center, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore.
The viruses implicated include herpes simplex virus (HSV), varicella zoster virus (VZV), herpes zoster viruses, cytomegalovirus (CMV), and perhaps Epstein Barr virus.
The CMV retinitis virus is the most frequently occurring ocular opportunistic infection in patients with AIDS. Before the advent of combination antiretroviral therapy, CMV retinitis developed in 30% of these patients and afterward in less than 1%.
Patients with AIDS are not the only group in which CMV retinitis can occur. Others include neonates and those in whom immunosuppression was induced, such as after organ transplantation, hematopoietic stem cell transplantation, malignancy, or other causes, Dr. Arevalo noted.
When these patients present, optical coherence tomography can be used to diagnose atrophic retinal detachments resulting from the very thin retinal tissue and exudative retinal detachments in the macula, he advised.
Polymerase chaine reaction
According to Dr Arevalo, polymerase chain reaction (PCR) can be performed to diagnose the CMV retinitis; while 50- to 100-μl tissue samples are ideal, the disease can be diagnosed with as little as 1 μl of tissue.
Once diagnosed, CMV retinitis can be treated with intravenous ganciclovir (5 mg/kg every 12 hours for two weeks and 5 mg/kg/day for maintenance) or oral valganciclovir (Valcyte, Genentech) (induction dose, 900 mg twice daily for three weeks and 900 mg once daily for maintenance). Intravitreal antiviral drug implants for CMV retinitis include ganciclovir (2-5 mg/0.05-0.1 μl) and foscarnet (Foscavir, Pfizer) (2.4 mg/0.1 μl).
According to Dr. Arevalo, retinal detachments develop in about 20% of this patient population. This detachment rate may decrease with improved therapies.
The number of patients in whom CMV retinitis develops has decreased, which, in turn, decreases the number of retinal detachments.
He noted that the extent and activity of the retinitis are risk factors for detachment. It is imperative to monitor this in patients and prepare a treatment plan.
“With longer patient survival, the need is great for a surgical strategy that will provide the best long-term visual outcome,” he said.