Effect of induced fixation disparity by negative lenses on the visually evoked potential wave

The effect of induced fixation disparity produced by negative lenses and base-in prisms on the pattern visually evoked potential (VEP) was investigated. Monocular and binocular pattern reversal VEP were recorded through the negative lenses and base-in prisms using a 9.5 min arc check size. The results suggest that the mean binocular amplitude was 27% larger than the mean monocular amplitude which indicates partial summation in the absence of negative lenses or base-in prisms. A reduction of the binocular VEP amplitude appears to arise in the presence of fixation disparity induced by both the negative lenses and base-in prisms. Both the prisms and the negative lenses had no appreciable effect on the monocular VEP amplitude.