The effect of accommodative hysteresis on apparent distance.

Abstract

The influence of accommodative hysteresis on monocular distance perception was examined in 18 visually normal young adults. Tonic accommodation and apparent distance were measured immediately before and after a 10 minute period of sustained focus at either the accommodative nearpoint or farpoint. Separate sessions were used for the two sustained focus conditions. On each session, apparent distance was assessed for both a highly effective and a non-effective accommodative target viewed at a constant optical distance of 3D. Sustained focus at the nearpoint resulted in a significant increase in the apparent distance of the highly effective accommodative target, as well as in tonic accommodation. Sustained focus at the farpoint yielded a slight decrease in tonic accommodation, but no significant alteration in the apparent distance of the highly effective accommodative target. No tendency for change in the apparent distance of the non-effective accommodative target was observed under either the nearpoint or farpoint condition. The results suggest that accommodative distance information is linked to the level of monocular blur-driven accommodative innervation necessary for clarity of focus.