Recording multifocal electroretinogram on and off responses in humans

Abstract

Purpose: To record the on and off responses of the multifocal photopic electroretinogram (ERG) from the human retina and to explore how each ERG component (a-, b-, and d-waves) changes at different retinal eccentricities.

Methods: Multifocal ERGs were recorded with the visual evoked response imaging system. Sixty-one densely packed stimulus elements were square wave-modulated between stimulus on and stimulus off, according to a binary m-sequence at a rate of 4.7 Hz under a constant background illumination. The ERGs were recorded with a bipolar Burian-Allen bipolar contact lens electrode from five normal subjects. Response densities (amplitude per retinal area) were calculated for five different eccentric rings.

Results: The response densities for all components (a-, b-, and d-waves) decreased with increasing retinal eccentricities. The ratio of the d-wave to b-wave amplitudes was minimal in the central retina and increased toward the periphery. The ratio of a-wave to b-wave amplitudes also increased toward the peripheral retina.

Conclusions: These results demonstrate that the on and off responses of the human cone ERGs have different spatial distributions across the human retina, and they suggest a change in the photopic retinal circuitry with increasing retinal eccentricities.