July 2019
Volume 19, Issue 8
Open Access
OSA Fall Vision Meeting Abstract  |   July 2019
The upper depth limit as a function of eccentricity
Author Affiliations
  • Suzanne McKee
    Smith-Kettlewell Eye Research Institute
  • Saeideh Ghahghaei
    Smith-Kettlewell Eye Research Institute
  • Preeti Verghese
    Smith-Kettlewell Eye Research Institute
Journal of Vision July 2019, Vol.19, 36. doi:https://doi.org/10.1167/19.8.36
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      Suzanne McKee, Saeideh Ghahghaei, Preeti Verghese; The upper depth limit as a function of eccentricity. Journal of Vision 2019;19(8):36. doi: https://doi.org/10.1167/19.8.36.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Observers can identify the disparity sign (crossed or uncrossed) of briefly-presented diplopic targets (<100msec) for disparities ranging up to 14 deg (Blakemore, 1970). However, they cannot localize these targets to a particular depth. At longer durations, the half-images of targets presented with large disparities appear to lie in the fixation plane separated laterally by a distance corresponding to target disparity. Schor, Wood & Ogawa (1983) asked observers to increase target disparity until they achieved this fixation-plane percept, a disparity they called the upper depth limit. McKee, Levi & Bowne (l990) found that disparity discrimination thresholds for disparities at or beyond the upper depth limit were identical to monocular width discrimination thresholds for widths equal to the disparity(‘dichoptic width’) separating the half-images. The disparity value where dichoptic and monocular width thresholds become equivalent provides a rigorous estimate of the upper depth limit -- the point where disparity no longer produces a sense of depth nor affects visual direction.

We measured disparity and width discrimination in the lower visual field to determine their equivalence point at three eccentricities (0, 5, 10 deg). The eccentricity function for this upper depth limit is surprisingly shallow, increasing at 10 deg eccentricity by only a factor of 2 from the foveal value of ~1.7 deg. We speculate that the narrow range of disparities that support a depth percept, even at eccentric loci, reflects the limited range of disparities generated by features in the natural world.

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