Double Flash Human Electroretinogram With Special Reference to the Oscillatory Potentials and the Early Phase of Dark Adaptation: A Normative Study

The ERGs of 20 healthy humans were studied with a double‐flash technique. The interval range between flashes was 0.35–180 sec and enabled the study of photopic as well as scotopic responses. The behaviour of the a‐ and b‐waves was compared with that of the oscillatory potentials (o.p.) during the early phase of dark adaption. The amplitude of the a‐ and b‐waves was decreasing the shorter the interval between flashes, while the amplitude of the o.p. was maximal at the 30 sec interval. The first oscillatory peak behaved differently from the others. The recovery of the ERG from suppression by flashes was calculated for the a‐ and b‐waves and a linear regression line was obtained. The o.p. behaved differently. Comparison with the dark adaptation curve suggested the recovery of the a‐ and b‐wave to be linked to a photochemical process and the o.p. to a neural process.