An objective VER assessment of visual acuity compared with subjective measures.

Visual acuity was estimated by making amplitude measurements of the transient visually evoked response (VER) wave to pattern reversal using check sizes of 5.5, 7.5, 8.5, and 9.5 min arc. As in previous studies the 5.5 min arc check produced a response which reflected the visual acuity of the high acuity subjects, but often failed to produce a VER wave at the low acuity end. The proposal is made that where the 5.5 min arc check produces an acceptable wave (amplitude greater than 1.5 microV) then the regression line for the 5.5 check can be used to predict visual acuity. Where the VER amplitude is below 1.5 microV for this small check size then a second recording must be made using the 9.5 min arc check and the visual acuity predicted from the 9.5 check regression line.