Accommodation to perceived depth in stereotests.

The question of whether the eye may accommodate to the stimulus provided by apparent depth in stereograms is considered theoretically in relation to the magnitudes of the disparities and viewing distances found in typical clinical stereotests. It is concluded that, for the relevant range of disparities (< or = 2000 arc sec), any shift in accommodation is likely to be small (< or = 0.15 D). An experimental study with two different clinical stereotests (Lang, TNO) confirms this prediction.