Effect of Accommodation on Apparent Distance Specified by Vergence

Abstract

Apparent distance is modulated by accommodation or vergence. There is conflicting evidence about the effect on distance perception when vergence and accommodation are presented simultaneously. In the current study, we investigated whether apparent distance defined by vergence is modulated by changes of accommodation. Subjects observed a dichoptic stimulus that evoked vergence by looking at a fixation target, through concave or convex lenses. This stimulus is called the reference stimulus. Similarly, they observed a target by looking through non-refractive lenses. This stimulus is called the test stimulus. The reference stimulus and the test stimulus appear at different distances if accommodation modulates apparent distance. We examined the point of subjective equality. The subjects changed the apparent distance of the test stimulus by changing the vergence angle of the test stimulus to make them have the same apparent distance. The result showed that apparent distance is modulated by changes of accommodation.