Contributors: Henry L. Hudson and David S. Boyer
Acute retinal necrosis [ARN] (Kirisawa-Urayama uveitis, acute retinal necrosis syndrome [ARNS], bilateral acute retinal necrosis [BARN], progressive outer retinal necrosis [PORN], necrotizing herpetic retinopathy] is a disorder in which the retina of one or both eyes undergoes acute necrosis. The condition is characterized by primary peripheral necrotizing retinitis [retinitis - necrotizing], retinal arteriolitis and frequent  retinal detachment. It may often become bilateral. Acute retinal necrosis can occur after or before the outbreak of cutaneous herpes zoster. The earliest retinitis consists of yellow-white lesions in the outer retina in the postequatorial fundus. Retinal arteriolitis and optic disc edema are usually present early in the disease. Over 3-5 days patches of yellow-white necrotizing full thickness retinitis develop in the peripheral retina and spread rapidly over the next 5-10 days. The retinitis may remain in one quadrant or may become confluent in the periphery. The retinitis almost never extends more posterior than the major arcades. The posterior pole is usually spared. Vitritis increases, and occasionally an exudative retinal detachment [retinal detachment - exudative] can occur in the inferior periphery. Central retinal artery occlusion or central central retinal vein occlusion or optic neuropathy can suddenly decrease vision. The visual prognosis for herpes simplex virus associated acute retinal necrosis is also poor. Recurrence of varicella zoster related acute retinal necrosis is rare in healthy individuals, but has been seen in AIDS patients. The progressive outer retinal necrosis syndrome, seen in advanced cases of AIDS, less commonly has retinal vasculitis or optic neuritis. The cases are often (71%) bilateral and poorly responsive to treatments. The pattern of retinal involvement is similar to acute retinal necrosis, except the lesions are confined to the outer retina and vitritis tends to be minimal. Visual prognosis is extremely poor with most ( up to 90%) patients worse than 20/400. Multifocal deep yellow white lesions which become full thickness yellow retinal necrosis are the hallmark. Retinal arteriolitis, optic disk edema, serous retinal detachment [retinal detachment - serous], intraretinal hemorrhage [hemorrhage - retina] have all been reported. Rhegmatogenous retinal detachment [retinal detachment - rhegmatogenous] is frequent later in the course of the disease. Progressively increasing vitritis is seen, limiting the view to the fundus. A self limited form of varicella zoster virus retinitis has been associated with chicken-pox.