Binocular summation in visually evoked responses and visual acuity.

Monocular and binocular transient visually evoked responses (VER) were recorded on 50 adult subjects using a pattern reversal stimulus (check size 5.5 min arc). The peak-to-trough amplitude of the VER wave was measured and compared with the subjective visual acuity (Landolt C). The binocular amplitude enhancement over the monocular amplitude was around 26% across the acuity range studied, whereas the mean binocular subjective visual acuity improvement was around 11.3%, but this varied from 1% at the high acuity end to 17% at the low acuity end of the range.