Variation of topographic visually evoked potentials across the visual field.

We examined the variation of monocular pattern reversal topographic visually evoked potentials across a 13.6 degrees visual field and measured the parameters of the VEP waveforms in 37 locations across the field. Eighteen right and 20 left normal eyes were tested from 23 subjects. The mean response densities of the VEP decreased with increasing eccentricity; response densities are higher in the lower hemifield than in the corresponding mirror symmetric locations in the upper hemifield. The incidence of polarity reversal is higher in the upper hemifield, especially in more superior locations. The latency in the temporal field is shorter than that in the other locations. The coefficients of variations (CVs) of latencies are less than those of amplitudes in corresponding locations and the CVs of latencies of P1 and N2 components are less than those of the N1 component in corresponding locations. The CVs of amplitudes of the waveforms in mid-peripheral locations are larger than those of the other central areas. The parameters of the human topographic visually evoked potential are distributed regularly across the visual field and appear to reflect the underlying anatomy of the retina and visual cortex, and the placement of the recording electrode.