Adaptation of tonic accommodation.

Abstract

We compared the resting (dark) focus of accommodation before and after adapting to accommodative stimuli placed nearer or farther from an initial baseline resting focus. Short-term monocular adaptation (less than 2 min) did not result in consistent after-effects that were correlated with the adaptation stimulus. After short-term adaptation, accommodation returned to its resting level in 2-15 s. Long-term monocular adaptation (30 min) to a 6-D near stimulus resulted in a small (0.5-D) average increase in the resting focus of accommodation beyond the normal 2-15-s short-term decay. These observations illustrate a tonic adaptation of accommodation that is small and requires longer durations of adaptation than an analogous adaptation of the fusional vergence system to prism.