Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Vision Disparity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources
PubMed2000

Stereodeficient subjects demonstrate non-linear stereopsis.

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.

Amblyopia↗
PubMed2002

The interface between ophthalmology and optometric vision therapy.

Considerable disparity lies between ophthalmologic impressions of optometric vision therapy, and the reality of optometric vision therapy as practiced in the United States. The viewpoint shared by ophthalmology in particular, and the medical field in general, is one that is filtered through organizational policy statements and the isolated experiences of influential individual practitioners. This has resulted in a skewed portrayal of optometric vision therapy. The purpose of this paper is to present a balanced perspective on this subject, and one that should be of assistance in creating an interface between ophthalmology and optometry that better serves the public.

Adult↗
PubMed1986

Spatial interaction in the domain of disparity signals in human stereoscopic vision.

When a few isolated features are viewed foveally, changes in the binocular disparity of one introduces apparent depth changes in others. For features a very few minutes of arc apart, the effect is equivalent to a pooling of their disparity signals, even though the features are seen distinctly as separate. When the distance between them is 4-6 minutes of arc or more, the effect is in the opposite direction: the features act as if they repelled each other in depth. Using a null method, it was possible to characterize this interaction effect numerically. There are some quantitative, but no qualitative, differences between observers, and in any one observer the disparity interaction between vertically separated targets is not necessarily the same as between horizontally separated ones. The disparity interaction effect is seen with presentations both of 50 ms and of 1 s duration. There is a very small temporal after-effect, seen when the extinction of inducing flanks is synchronous with test target onset.

Depth Perception↗
PubMed2006

Slant perception, and its voluntary control, do not govern the slant aftereffect: multiple slant signals adapt independently.

Although it is known that high-level spatial attention affects adaptation for a variety of stimulus features (including binocular disparity), the influence of voluntary attentional control-and the associated awareness-on adaptation has remained unexplored. We developed an ambiguous surface slant adaptation stimulus with conflicting monocular and binocular slant signals that instigated two mutually exclusive surface percepts with opposite slants. Using intermittent stimulus removal, subjects were able to voluntarily select one of the two rivaling slant percepts for extended adaptation periods, enabling us to dissociate slant adaptation due to awareness from stimulus-induced slant adaptation. We found that slant aftereffects (SAE) for monocular and binocular test patterns had opposite signs when measured simultaneously. There was no significant influence of voluntarily controlled perceptual state during adaptation on SAEs of monocular or binocular signals. In addition, the magnitude of the binocular SAE did not correlate with the magnitude of perceived slant. Using adaptation to one slant cue, and testing with the other cue, we demonstrated that multiple slant signals adapt independently. We conclude that slant adaptation occurs before the level of slant awareness. Our findings place the site of stereoscopic slant adaptation after disparity and eye posture are interpreted for slant [as demonstrated by Berends et al. (Berends, E. M., Liu, B., & Schor, C. M. (2005). Stereo-slant adaptation is high level and does not involve disparity coding. Journal of Vision 5 (1), 71-80), using that disparity scales with distance], but before other slant signals are integrated for the resulting awareness of the presented slant stimulus.

Adaptation, Physiological↗
PubMed2006

[Clinical study on crossed disparity and uncrossed disparity in intermittent exotropia before and after surgery].

OBJECTIVE: To understand the clinical variety of zero disparity, crossed disparity and uncrossed disparity in intermittent exotropia before and after strabismus surgery. METHODS: 100 cases of intermittent exotropia were involved in the study. Before and after surgery, zero disparity stereo-acuity, crossed disparity and uncrossed disparity stereo-acuity were examined with stereogram designed by Yan Shaoming, distance fusion range and distance stereo-acuity were examined with traditional and random dot synoptophore stereogram. The patients were divided into four groups based on the results of the stereogram examination before surgery. RESULTS: In the 100 cases, there was no coexistence of zero disparity and uncrossed disparity, no coexistence of crossed and uncrossed disparity, and no existence of only crossed disparity or only uncrossed disparity. Postoperative zero disparity, crossed disparity, uncrossed disparity, distance fusion range and distance stereo-acuity improved significantly compared with the preoperative results for each group (P < 0.01). The comparison of distance fusion range was not prominent before and after strabismus surgery in the 4 groups (P > 0.05). The distribution of distance stereo-acuity was prominent after strabismus surgery in the 4 groups (P < 0.01). Distance stereo-acuity rebuilding after surgery in group 1 and group 2 was better than that in group 3 and group 4. CONCLUSIONS: (1) In the cases with intermittent exotropia, zero disparity stereo-acuity, crossed disparity and uncrossed disparity stereo-acuity are abnormal. The sequential damage of stereopsis is uncrossed disparity, crossed disparity and zero disparity. The sequential rebuilding of stereopsis is zero disparity, crossed disparity and uncrossed disparity. (2) The serious damage or disappearance of uncrossed disparity stereo-acuity is the indication of intermittent exotropia surgery for perfect binocular vision rebuilding.

Adolescent↗
PubMed1996

Stereoacuity and colour contrast.

We have measured the contrast dependence of stereoacuity using both horizontally and vertically oriented, isoluminant (red-green) and isochromatic (yellow-black), 0.5 c/deg Gabor patches. For comparison, contrasts were computed in multiples of detection threshold, where detection threshold was defined as the contrast required for the stimulus to be simultaneously detectable in each eye. Disparity thresholds (1/stereoacuity) for vertical chromatic Gabors were higher than those for vertical luminance Gabors by a factor of between 4 and 9 depending on contrast, and declined less steeply with contrast. Disparity thresholds for horizontal chromatic Gabors were very high (130-210 min arc) compared with horizontal luminance Gabors (by a factor of between 9 and 17) and were only measurable at contrasts above 10 times simultaneous monocular detection threshold. These results support the view that chromatic stereoscopic processing is less precise than luminance stereoscopic processing, and that there is a special deficit in the processing of disparity with horizontally oriented chromatic stimuli. The implications of these results for the role of colour vision in stereopsis are discussed.

Color Perception↗
PubMed1990

Detection of disparity motion by the human observer.

A single-line stimulus in a context-free visual environment presented for 250 msec needs to move with a disparity velocity of 25 to 45 min of arc/s before the direction of depth motion can be correctly identified. Presence of a pair of flanking line stimuli improves this value severalfold, but even then the threshold is 18 to 28 times higher than for the detection of a static disparity difference.

Depth Perception↗