Dark adaptation with interposed white adapting fields.

It is proposed that dark adaptation following a moderate pigment bleach may nearly as well be carried out (and more conveniently) under low room lighting conditions as in complete darkness. To test this idea, dark adaptation curves were determined either immediately after the termination of a 3 min, 4.1 log td white pre-exposure field, or following 10 or 15 min of additional exposure to one of three low-level photopic (2.9, 2.4, 1.8 log td) backgrounds of white light. Dark thresholds measured after the additional exposure fell rapidly and reached the rod plateau of the normal dark adaptation curve with a maximal delay of 1.5 min (for the 10 min backgrounds) or 6.5 min (for the 15 min backgrounds). For the time to be spent in the dark, this meant a savings of 8.5 min. At smaller delays savings were even greater. The difference between savings and delay indicates whether or not an interposed background is feasible.