13] Electroretinographic determination of human Rod flash response in vivo

Abstract

This chapter describes a “paired-flash” electroretinogram (ERG) method that circumvents the constraint just noted, and in human subjects yields approximate determination of the full time course of the massed rod response to a test flash of arbitrary intensity. Studies to date investigating the paired-flash technique in human subjects indicate that this method yields, to good approximation, the full time course of the massed rod photoreceptor response to a test flash. Support for this conclusion comes primarily from the correspondence of kinetic, sensitivity, and light adaptation properties of the paired-flash-derived response with photocurrent response properties of human and other mammalian rods in vitro . Results obtained with the paired-flash method motivate further work in both human subjects and experimental animals to refine this in vivo approach for studying rod phototransduction. The chapter also identifies a number of considerations likely to be important for future development of the technique, including the refinement of procedures to subtract the cone contribution at short interflash intervals, and to better correct for postreceptor contributions and desensitization of the probe flash response.