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Teng-Leng Ooi, Chao Han, Zijiang He; Effect of sensory eye dominance and unequal binocular contrast stimuli on stereopsis. Journal of Vision 2016;16(12):829. doi: https://doi.org/10.1167/16.12.829.
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© ARVO (1962-2015); The Authors (2016-present)
Empirically, the extent of sensory eye dominance due to an imbalance of interocular inhibition (SED-inhibition) is gauged when the two eyes viewing a binocular rivalry stimulus achieve equal predominance. This occurs when the physical contrast levels of the rivalrous half-images are adjusted so that the weak eye receives a higher contrast level. It has been shown that observers with significant SED-inhibition have reduced stereopsis for binocular depth stimuli with equal contrast level (Ooi & He, 2001; Xu et al, 2011). However, it is not known how the stereo perception of observers with SED-inhibition is affected by binocular depth stimuli with unequal contrast levels in the two eyes. Here, we investigated this question by testing observers with clinically normal vision. SED-inhibition was measured using a pair of binocular rivalry stimulus with vertical and horizontal gratings. We then measured observers' stereo thresholds using random dots stereogram with different interocular log contrast ratio. For the range of log(interocular contrast ratio) tested (-0.4, -0.2, 0, +0.2 +0.4), we found an approximately V-shaped stereo threshold versus contrast ratio function with a minimum close to zero log(interocular contrast ratio). That is, stereo threshold was lowest when the physical contrast levels in the two eyes were similar. We also found asymmetric slopes in the two arms of the V-shaped function. Namely, the side of the arm where the strong eye received higher contrast level had a steeper slope indicating that stereopsis of observers with significant SED-inhibition can be compromised when more extreme contrast levels are uncompensated. A possible explanation is that the contribution of the interocular inhibitory mechanism to the stereoscopic process increases as the difference in physical contrast between the two eyes increases. Accordingly, having an unbalanced interocular inhibition impedes the stereoscopic process more so when the difference in interocular contrast is large.
Meeting abstract presented at VSS 2016
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