The effect of simultaneous dual-focus integration on the global flash multifocal electroretinogram in the human eye

To investigate the effect of simultaneous dual-focus (DF) on retinal activities measured by global flash multifocal electroretinogram (mfERG).

Thirty adults were recruited for mfERG measurement under three conditions: in-focus (i.e., no defocus), +2.50 D DF and +7.50 D DF, administered using single vision contact lenses and DF lenses. The direct component (DC) and the induced component (IC) of the mfERG were pooled into central macular (0-8°), para-macular (8-18°) and peri-macular (18-30°) regions, and then compared across the three conditions using two-way, repeated measures ANOVA.

Simultaneous DF had a significant effect on the IC amplitude, which was significantly stronger under +7.50 D DF (p < 0.01) than for the in-focus condition, which was mostly derived from the central and para-macular regions. No significant effect was observed for the +2.50 D DF condition.

Under the effect of relatively strong simultaneous DF integration, the retina showed an enhanced retinal response, which originated from the inner retina. Compared with the peri-macular region, central and para-macular responses appeared to be enhanced.