Assessment of local cone on- and off-pathway function using multifocal ERG technique.

There is evidence that recording the photopic ON- and OFF-responses with long-duration stimuli is useful for determining the contribution of the cone ON- and OFF-pathways to the primate photopic electroretinogram (ERG). In this study, the optimal conditions for recording multifocal ON-OFF responses are described, and the technique is applied to normal subjects and two patients with unusual retinal diseases. The results from the normal subjects demonstrated that there were topographical variations of the photopic ERG waveform: when responses were normalized to the ON-response (b-wave) amplitude, the OFF-response (d-wave) amplitude increased with increasing eccentricity. The changes in the waveform in two patients suggested relatively greater defects of the hyperpolarizing or depolarizing bipolar cells. We conclude that the multifocal ERG technique with long-duration stimuli can be a useful tool to assess the function of local cone ON- and OFF-pathways in normal and diseased retinas.