The pattern electroretinogram: N95 amplitudes in normal subjects and optic neuritis patients.

Recent work has suggested that the N95 peak of the transient pattern electroretinogram (PERG) may be a more sensitive indicator of the late stages of retinal function prior to optic nerve activation than the P50 peak. In this report, we show that a new measure of N95 amplitude, based on digital filtering methods to identify a non-linear baseline before measurement, greatly reduced the amplitude variation in a population of 50 normal subjects when compared with two other plausible measures. We then used that new measure to follow the time course of N95 amplitudes in 12 optic neuritis patients. It was found that maintenance of a normal N95 amplitude at 6 months after onset of optic neuritis was always associated with excellent clinical recovery as measured by visual fields, acuity, presence or absence of an afferent pupil and optic atrophy, and contrast sensitivity (CS). Loss of N95 amplitude to below laboratory limits of normal was associated with abnormalities in these indicators of visual function. This study supports the idea that the N95 peak represents retinal ganglion cell function.