Use of pattern electroretinography to differentiate acute optic neuritis from acute anterior ischemic optic neuropathy.

The transient pattern electroretinogram (PERG) was recorded from 16 patients with acute optic neuritis and from 13 patients with acute non-arteritic anterior ischemic optic neuropathy (AION). All patients were tested within 35 days from the the onset of visual symptoms and all had significant central visual field abnormalities in their affected eyes as quantified by automated perimetry. Analysis of the PERGs showed that the amplitude of the N95 peak was abnormally reduced for each eye affected with AION while it remained normal in optic neuritis. No significant alteration in P50 amplitude was observed in either condition. The loss of N95 amplitude in AION was highly correlated with the average depth of visual field loss (in decibels) within a radius of 10 degrees of fixation. These results suggest that PERG could be used early in the course of optic neuropathy to distinguish optic neuritis from AION in those cases for which the diagnosis is still uncertain after the clinical examination.