Note on the Electrical Response of the Human Eye During Dark Adaptation*

Measurement of the magnitude of the principal component of the electrical response of the human eye to an intense flash of light, as a function of time in the dark following five minutes of light adaptation to an extremely bright field, shows an increasing response as a function of time in the dark. The curve levels off at a plateau before a second abrupt rise at about seven minutes in the dark. This break in the curve resembles the rod-cone break in the psychophysical dark-adaptation curve, in that a decrease in the level of prior light adaptation reduces the prominence of the break or even eliminates it. The variation in the initial dark electrical response after various time intervals of prior light adaptation resembles the variation in cone threshold after various durations of light adaptation.