Mechanisms in Peripheral Dark Adaptation

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Abstract
Measurements are presented of the absolute thresholds for red and green test flashes at various times during a 0.5 sec interruption of a red and green adapting field occurring each 3 sec, under variation of the size d of the test spot between 4′-420′ and the brightness A of the adapting field. Peripheral vision 7° nasal from the fovea of the observer’s right eye is concerned.From these measurements nervous and photochemical components in adaptation are detected with the aid of speculations on the validity of quanta-explanations for visual functions.The dependence of the absorption power of the photochemical substances on the adapting brightness which we deduced from the reported data, agree with the steady-state equation in photochemical theories.With increasing brightness of the adapting field for green test flashes, Ricco’s region in the curve representing the absolute threshold as a function of d diminishes, whereas the minimal necessary number of quanta that is absorbed in the receptors such that they contribute to the light perception increases.