Abstract
An overshoot in dynamic accommodation is often observed when a step in the convergence stimulus is presented (e.g., a change in depth in a stereoscopic image). However, the overshoot is not observed in all subjects (Torii et el., J Mod Opt, in press). The accommodative overshoot may occur as a result of influences from convergence-induced accommodation, which is the first phase of the accommodative response, and blur-induced accommodation. In the present study, we examined the hypothesis that the overshoot appears when an individual's CA/C ratio is high. Stereoscopic images were presented on a parallax-barrier LCD display. Accommodative responses were measured using a modified video refractor. CA/C and AC/A ratios were measured respectively by blurring stimulus and by occluding one eye using the same instruments. The results showed that CA/C and AC/A ratios are negatively correlated as shown previously and that amplitude of the overshoot is large in subjects with high CA/C ratios. We conclude that the transient overshoot in accommodative responses is caused by excess convergence accommodation.