Objective To systemically explore the range of visual angles that affect visual acuity, and to establish the relationship between the P 1 component （peak latency -100 ms） of the pattern-reversal visual-evoked potential （PRVEP） and the visual acuity at particular visual angles. Methods Two hundred and ten volunteers were divided into seven groups, according to visual acuity as assessed by the standard logarithmic visual acuity chart （SLD-II）. For each group, the PRVEP components were elicited in response to visual angle presentations at 8°, 4°, 2°, 1°/60＇, 30＇, 15＇, and 7.5＇, in the whiteblack chess-board reversal mode with a contrast level of 100% at a frequency of 2 Hz. Visual stimuli were presented monocularly, and 200 presentations were averaged for each block of trials. The early and stable component P1 was recorded at the mid-line of the occipital region （Oz） and analyzed with SPSS 13.00. Results （1） Oz had the maximum Pl amplitude; there was no significant difference between genders or for interocular comparison in normal controls and subjects with optic myopia. （2） The P1 latency decreased slowly below 30＇, then increased rapidly. The P1 amplitude initially increased with check size, and was maximal at -1° and -30＇. （3） The P1 latency in the group with visual acuity 〈0.2 was signifi- cantly different at 8°, 15＇ and 7.5＇, while the amplitude differed at all visual angles, compared with the group with normal vision. Differences in P1 for the groups with 0.5 and 0.6 acuity were only present at visual angles 〈1°. （4） Regression analysis showed that the P1 latency and amplitude were associated with visual acuity over the full range of visual angles. There was a moderate correlation at visual angles 〈30＇. Regression equations were calculated for the P1 components and visual acuity, based on visual angle. Conclusion （1） Visual angle should be taken into consideration when exploring the function of the visual pathway, especially visual acuity. A vi
Xiping ChenQianqian LiXiaoqin LiuLi YangWentao XiaLuyang Tao
