Accommodation and Stereoacuity

Stereoacuity and resolution acuity were measured (1) through apertures set at various distances from S and (2) through plus lenses producing an accommodative error for the target equal to that produced by the presence of the apertures. Stereoacuity was degraded by the apertures but not by the lenses, whereas resolution acuity was degraded by the lenses but not by the apertures. Although stereoacuity progressively declined with decreasing targetdistance , it did not change significantly if accommodation remained constant. The decline of stereoacuity in the water is attributed to increased accommodation resulting from different sources and to the paucity of visual stimulation which is typical of the underwater scene and which is known to disrupt many visual processes (the so-called "Ganzfeld" effect).