The mechanism of dark-adaptation

An analysis is given of the various possible components of the dark-adaptation process. A distinction is made between: Photochemical component (ƒ1), neural receptor component (ƒ2), spatial summation component (D), temporal summation component (T) and a quantum coincidence component (k). These various components partly reveal themselves in different ways in dark-adaptation curves obtained by sensitivity measurements as a function of time for different target-sizes, different target-colours and different retinal locations. Experiments were carried out in order to study the relative contribution of each component for foveal as well as for peripheral vision. Foveal adaptation appears to be governed by the component ƒ1 and perhaps also ƒ2. In phase I of peripheral adaptation a small D-component is added and in phase II of peripheral adaptation only the k-component is active. The behaviour of the resting potential of the human eye during dark-adaptation does not bear a simple relation to any of the neural components mentioned in the present paper