[Visual acuity measured by pattern visual evoked potential]

We investigated the appropriateness of a method for the assessment of visual acuity using pattern visual evoked potentials (PVEP) in which retinal X-ganglion cells are predominantly stimulated. Eighteen normal eyes (average 22.2 years old) with normal acuity of 1.0 were examined. The stimulus consisted of white and black checkerboards (39', 26', 15' and 9') with a visual angle of eight degrees and a contrast level of 15%. The pattern reversal frequency was 0.7 Hz. This resulted in 100 averaged PVEP per session. We judged visual acuity from responses of the P100 component. Visual acuity was judged to be 0.1, so that there was response to the 39' checkerboard stimulus pattern, but not to the 26' pattern. Consequently, the accuracy for visual acuity was 76.9% for 0.1, 71.4% for 0.2, 70.0% for 0.5 and 58.3% for 1.0. This method, which uses a stimulus pattern with a small visual angle, low contrast, and low pattern reversal frequency, is useful for subjective measurement of the visual acuity of infants or handicapped children whom it is difficult to measure by the conventional objective method of measuring visual acuity with Landolt's rings.