The pattern evoked electroretinogram: its variability in normals and its relationship to amblyopia

Electroretinograms evoked by pattern stimuli (contrast reversing gratings) were measured under steady state conditions in the normal and amblyopic eyes of 14 amblyopic individuals having Snellen acuities in the range 20/100 to 20/600. These ERGs were measured as a function of spatial frequency, and compared with the psychophysical threshold losses to the same stimuli. In all cases the authors compared the normal and fellow amblyopic eye's response while taking into account the variability of right-left eye comparisons of normal individuals for these psychophysical and electrophysiological tests. When factors such as optical focus, fixation alignment, and fixation stability have been individually optimized, no pattern ERG deficit was observed in a spatial frequency range where there were obvious psychophysical deficits to the same stimuli. Our results do not substantiate previous claims of a pattern ERG anomaly in many severely amblyopic eyes.