DEPTH-PERCEPTION IN RANDOM-DOT STEREOGRAMS IS NOT AFFECTED BY CHANGESIN EITHER VERGENCE OR ACCOMMODATION

Purpose. To test the hypothesis that extraretinal cues related to verg ence angle and lens accommodation are used to scale horizontal dispari ties for fixation distance. Methods. Depth perception of random dot st ereograms was studied in 10 healthy adult subjects with normal visual acuity by modifying retinal disparity, fixation distance, vergence ang le, and accommodation. Statistical analysis was used to compare the da ta. Results. Depth perception increased with fixation distance. The in crement of depth perception persisted even when horizontal retinal dis parity was kept constant. The magnitude of depth perception was indepe ndent of vergence angle. Depth perception did not vary with changes in accommodation. Conclusions. Extraretinal cues related to vergence ang le and accommodation seem to be not necessary to scale horizontal disp arities for viewing distance.