Early dark adaptation, the receptor potential and lateral effects on the retina.

The rapid threshold drop in early dark adaptation has been found to slow, following saturating adaptation levels in the rod monochromat, and following cone-saturating flashes in normal subjects. This supports the idea that early dark adaptation reflects the decay of the receptor potential to the adapting light, but contrast effects also influence the shape of the early dark adaptation curve. It is proposed that early dark adaptation reflects both receptor potential decay and loss of lateral effects following an adapting light. Variations of curve shapes are discussed from this point of view, with their theoretical significance.