To test the hypothesis that extraretinal cues related to vergence angle and lens accommodation are used to scale horizontal disparities for fixation distance.Methods.
Depth perception of random dot stereograms was studied in 10 healthy adult subjects with normal visual acuity by modifying retinal disparity, fixation distance, vergence angle, and accommodation. Statistical analysis was used to compare the dataResults.
Depth perception increased with fixation distance. The increment of depth perception persisted even when horizontal retinal disparity was kept constant. The magnitude of depth perception was independent of vergence angle. Depth perception did not vary with changes in accommodation.Conclusions.
Extraretinal cues related to vergence angle and accommodation seem to be not necessary to scale horizontal disparities for viewing distance.