Human electroretinogram near the absolute threshold of vision.

.raditional studies of the animal and human electroretinogram (ERG) indicate that the stimulus intensity necessary to evoke a minimal ERG from the dark adapted retina is well above the absolute threshold of vision; these studies also show that the ERG response at threshold consists of the b-wave only, and the a-wave appears at suprathreshold intensities. Recent work on the toad, rat, cat, monkey, and human' ERG, however, demonstrates that it is possible to obtain an ERG with very dim stimuli, approaching the absolute threshold of vision. Some of these investigations have shown that the threshold ERG consists of a corneal negative potential with the b-wave appearing at suprathreshold intensities. The amplitude of the ERG is small when caused by stimuli of very low intensity, so that it is difficult to record and interpret ERGs with stimuli near the absolute threshold of vision. The purpose of our study was to enhance and utilize these very small potentials by modifying the