[Pattern reversal electroretinogram--effect of check size, luminance, field size and defocusing]

Using a high water-content soft-contact-lens electrode we recorded pattern electroretinograms (P-ERGs) of subjects responding to reversal checkerboard stimuli and the stimulus parameters were varied in order to investigate normal P-ERG properties. The P-ERG varied with changing luminance, field size and defocusing parameters in the same way as P-VECP, but differed from P-VECP with changes in the check size parameter. These results suggest that the spatial tuning observed in P-VECP could not be discerned in this P-ERG study. It cannot be denied that P-ERG is distorted by P-VECP, which has a larger amplitude at about 100 ms after stimulation. In the future it will be necessary to investigate the origin of P-ERG under experimental conditions separating contrast-related response from luminance-related response.