Acute retinal necrosis may be classified both by duration of symptoms into acute or late, or by severity: mild or fulminant.

• Acute retinal necrosis (ARN) may be classified by duration of symptoms as follows:^[1]
  • Acute stage: Occurs at onset of disease and usually progresses past acute classification after a few weeks
    • Presents with coalescence of white, necrotic tissue in the peripheral retina
    • Vaso-occlusive retinal vasculitis is usually present
    • Optic nerve head of the affected eye will appear swollen, but the posterior pole will usually not be affected
  • Late stage: Is the natural progression of the disease and will present differentiating characteristics after a few weeks up to a few months
    • Characterized by a regression of the coalesced necrosis in the peripheral retina, presenting starkly contrasted necrotic/non-necrotic tissue, mild pigmentation scarring, and increased vitreous debris
    • Retinal detachment, severe vision loss, and potentially blindness in the affected eye
    • If the infection is bilateral, the second eye will usually present signs of ARN in the weeks and months following the initial symptom manifestation in the first eye
• Acute retinal necrosis can also be classified by severity as follows:^[2]
  • Mild: Used to characterize ARN that is stable and non-progressive
    • There is usually no sign of retinal detachment.
  • Fulminant: ARN that is progressive and will usually lead to retinal detachment and further complications if left untreated