Acute retinal necrosis refractory to treatment

A female patient in her 60s presented with a right eye hypertensive uveitis and subsequently developed vitritis and retinitis. An anterior chamber tap was PCR positive for herpes simplex virus. Despite oral valaciclovir 2 g three times a day and an initial intravitreal foscarnet 2.4 mg/0.1 mL injection her condition worsened, with more extensive retinal necrosis and retinal haemorrhages. A repeat anterior chamber tap was performed and PCR testing confirmed viral strains resistant to aciclovir. The patient was therefore treated with repeated intravitreal injections of foscarnet along with intravenous foscarnet which stabilised her clinical condition for a time, though unfortunately her retina later detached. Acute retinal necrosis is an uncommon but visually devastating infectious uveitis; in situations where initial antiviral treatments are not stabilising or improving the clinical picture it is important to consider the rare possibility of antiviral resistance. Intravenous foscarnet carries the risks of unpleasant and potentially dangerous side effects, about which patients must be counselled.