Correlation Of Visual Evoked Potential And Cognitive Event Related Potential With Visual Sensitivity

Purpose: By combining pattern-reversal visual evoked potential (PRVEP) and cognitive event related potential (C-ERP) in normal controls and subjects with different degrees of visual disorders, we aimed to investigate their characteristics and correlations with visual acuity, and tried to make it as an objective electrophysiological index for evaluating visual functional status.Method: Ninety eyes were applied in this study, and three groups (0.1, 0.5 and 1.0) were divided according to the vision checked in standard logarithmic visual acuity chart (SLD-Ⅱ). (1)The PRVEP were induced by series of check size (8°, 4°, 2°, 1°, 30', 15', 7.5') in white-black chess-board reversal mode with a visual angle of eight degrees, a contrast level of 100%, and a temporal frequency of 2 Hz. (2)C-ERPs were induced in a visual three-stimulus oddball task, involving the pseudorandom presentation of visual stream altogether 200 presentations with non-targets for 75%, rare target stimulus for 15% and probe stimulus for 10%. Three blocks of visual stimulus correlated with visual angle of 50', 10'and 5'were presented in turn. Amplitude and latency of N1, P1 components at Oz in PRVEP and that of P3a, P3b components at midline electrodes in ERP were measured for analysis.Results: In PRVEP testing, the results showed: (1) The PRVEP locates at occipital region, with peak amplitude at Oz. (2) N1, P1 latency and amplitude all display curvilinear relationship with visual angle of visual stimulus, and 30'is the optimal stimulus (p<0.01) for its shortest P1 latency and greatest P1 amplitude. (3) P1 latency and amplitude both show linear correlation with visual acuity (R2>0.90). Along with the increments of the visual sensitivity, P1 latency shortened and P1 amplitude raised. Significant difference exists in P1 latency and amplitude among vision groups (p<0.01).For Cognitive ERP recording, the results indicated: (1) P3a lacats at forehead- parietal (FCz), P3b locates at parietal-occipital (Pz); (2) P3a, P3b latency and amplitude all show significance differences with visual angles (P<0.01). (3) P3a, P3b latency both show linear correlation tendency with visual angles (R2>0.90). Along with the diminished size of the visual stimulus, P3a, P3b latency lengthened while amplitude decreased. (4) P3a, P3b latency show statistical significance with visual acuity (P<0.05). (5) P3b latency shows negative correlation with visual acuity, while other indices have no obvious linear correlation with visual acuity.Conclusions: (1) Components of PRVEP and ERP have different electrodedistribution; (2) Size of the visual stimulus affect components of PRVEP and ERP, showed that P1, P3a and P3b latency and amplitude all show linear correlation tendency with visual angles.(3)P1 latency and amplitude,P3b latency show linear correlation tendency with visual acuity.