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.
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机译：根据经验，当观察双眼竞争性刺激的两只眼睛达到相同的优势时，可以评估由于眼内抑制（SED抑制）不平衡而导致的感官眼优势的程度。当调整对等的半张图像的物理对比度时，会发生这种情况，以便弱视者获得较高的对比度。已经显示，具有显着SED抑制作用的观察者以相同的对比度水平降低了双眼深度刺激的立体视（Ooi＆He，2001; Xu et al，2011）。然而，未知的是，具有SED抑制作用的观察者的立体感觉如何受到两只眼睛中对比度水平不相等的双眼深度刺激的影响。在这里，我们通过测试具有临床正常视力的观察者来调查这个问题。使用一对带有垂直和水平光栅的双眼竞争刺激来测量SED抑制。然后，我们使用具有不同眼对数对比率的随机点立体图测量观察者的立体阈值。在测试的log（眼内对比度）（-0.4，-0.2、0，+ 0.2 +0.4）范围内，我们发现了近似V形的立体阈值与对比度的函数，且log（眼内对比度）的最小值接近零。 ）。即，当两只眼睛的物理对比度水平相似时，立体阈值最低。我们还在V形函数的两个臂中发现了不对称的斜率。即，强眼获得较高对比度的臂侧具有较陡的斜率，这表明当没有更极端的对比度水平补偿时，具有明显的SED抑制作用的观察者的立体视就会受到损害。可能的解释是，随着两只眼睛之间的物理对比度差异的增加，眼内抑制机制对立体过程的贡献也会增加。因此，当眼内对比度的差异较大时，具有不平衡的眼内抑制更加阻碍了立体过程。
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