Stereodeficient subjects demonstrate non-linear stereopsis

Abstract

There appear to be two modes of stereoscopic processing: a conventional linear operation that is dependent on correspondence between local luminance components in the two eyes' views, and a non-linear or second-order processing mode. This second mode may use disparity information provided by particular 'non-Fourier' features of the stimulus such as the contrast envelope. Preliminary results suggest that people who fail standard clinical stereotests are able to extract non-linear disparity information from Gabor stimuli [McColl & Mitchell, 1998. Vision Research, 38, 1889-1900]. Here we evaluate the status of the non-linear mechanism in such individuals by using two types of contrast enveloped stimuli, namely random line and Gabor micropatterns, in a task that requires near/far depth judgements [Ziegler & Hess, 1999. Vision Research, 39, 1491-1507]. Although our sample was small, three of our four subjects who had performed poorly on at least one standard clinical test of stereopsis could perform the task, as well as one 'stereoblind' subject who had failed all four standard clinical tests. The overall results suggest that individuals with stereoanomalies show a diversity of deficits, but some nevertheless can see depth using 'non-linear' mechanisms.

Sparing of coarse stereopsis in stereodeficient children with a history of amblyopia

“…However, there is preliminary evidence for the resilience of stereopsis at larger disparities in adults who have disrupted binocular vision. McColl, Ziegler, and Hess (2000) demonstrated that some individuals who are stereoanomalous are able to localize stimuli in depth via coarse disparity signals. Furthermore, Harris, Wilcox, Moroz-Harris, Day, and Smith (2000) found that a subset of their observers with strabismus were able to judge the relative depth of diplopic targets better than visually normal subjects in spite of the fact that they performed very poorly on standard tests of stereopsis.…”

First- and second-order contributions to depth perception in anti-correlated random dot stereograms

“…31 Strong evidence to support this is found in individuals with strabismus, 56 a condition where the eyes are abnormally aligned. Standard clinical tests suggest that individuals with strabismus are stereo-deficient, however McColl et al (2000) demonstrated that some individuals were still able to perceive depth in their task. Wilcox and Allision (2009) suggest this depth perception was via coarse disparity signals from the second-order mechanisms.…”

The Effects of Anisometropic Amblyopia on the FNS and TNO Stereotest Thresholds in Four- to Eight-Year-Olds

“…Therefore it does not require anisometropic amblyopes to utilise the first-order processing of fine detail; it would mainly require the second-order processing of the more coarse information to elicit a good result. As a consequence, anisometropic amblyopes may have the ability to achieve high stereoacuity thresholds with the FNS and struggle to achieve similar stereoacuity thresholds with the TNO (McColl, Ziegler & Hess, 2000;McColl & Mitchell 1998;Giaschi et al, 2013). Conversely, there was also no statistical significance found between IAD and TNO stereoacuity in anisometropic amblyopes.…”