Studies of the A-Wave in the Human Electroretinogram

Abstract

The electroretinogram (ERG) in response to high-intensity stimuli represents a sequence of waves beginning with a negative deflection—the a-wave. Previous studies have analyzed this complex wave in terms of photopic and scotopic components. These analyses were derived from the behavior of the a-wave during dark adaptation and with stimuli of different wavelengths.^1-4 This assumption of a duplex nature of the a-wave has been strengthened by the fact that it frequently appears to be split into two parts separated by a "step," or hump. Based on this finding, tentative schemes have been suggested in which the photopic and scotopic components of the a-wave are distinguished by different latencies.^1,4 The present study deals with the a-wave of normal, congenitally night-blind, and totally color-blind subjects in response to white-light stimuli of different intensities. Since the rapid course of the a-wave prevents adequate measurements when it is registered with standard ERG techniques,