Cooper Philip R, Mendola Janine D
McGill Vision Research and Department of Ophthalmology, McGill University, Montréal, QC, Canada.
J Vis. 2019 Nov 1;19(13):14. doi: 10.1167/19.13.14.
Stereoanomalous (SA) subjects have normal visual acuity but reduced stereopsis and may have a prevalence of up to 30%. It has been suggested that, in SA subjects, an imbalance in interocular inhibition might underlie an asymmetry in sensory eye dominance (SED). Our study expands upon previous findings by examining binocular rivalry (BR) mean dominance durations, dichoptic masking (DM) thresholds and SED for a group of SA subjects compared to naïve controls. We examined BR dominance durations and DM thresholds for 15 stereonormal (SN) subjects and 10 SA subjects with normal or corrected-to-normal visual acuity. All subjects had visual acuity of 20/40 or better and less than or equal to two lines difference between eyes. Individuals who scored ≥6/9 on the Randot stereo test and <100 arcmin on the PacMan Stereo Acuity test were considered SN. We compared near-vertical and near-horizontal oriented sine-wave gratings for BR and DM in order to dissociate stereo-related mechanisms that rely on horizontal disparities from other eye-based integration mechanisms. Mean randot scores for SN subjects were 8.5/9 with a PacMan stereoacuity of 33 arcmin, and SA subjects scored 2.5/9 and 3,380 arcmin, respectively. The mean difference in SED was 0.19 for SN and 0.48 for SA when measured with a neutral density filter bar. The SA group showed a large interocular difference in BR durations that was significantly greater than normal (p = 0.004) and correlated with loss of stereoacuity. Moreover, the interocular difference for DM was similarly greater for SA subjects (p = 0.04) although a proportional difference in monocular sensitivity could partially account for this. We also found that both SN and SA subjects presented higher DM thresholds and, to some extent, sensitivity for vertical than horizontal orientations. SA subjects show an abnormal bias toward their dominant eye for both BR and DM. These data suggest that common mechanisms of monocular sensitivity and interocular inhibition may limit multiple binocular measures and provides a practical link to better understand the heterogeneity of stereopsis in amblyopia.
立体视觉异常（SA）受试者视力正常，但立体视锐度降低，患病率可能高达30%。有人提出，在SA受试者中，眼间抑制失衡可能是感觉性眼优势（SED）不对称的基础。我们的研究通过检查一组SA受试者与未经训练的对照组的双眼竞争（BR）平均优势持续时间、双眼掩蔽（DM）阈值和SED，扩展了先前的研究结果。我们检查了15名立体视觉正常（SN）受试者和10名视力正常或矫正至正常的SA受试者的BR优势持续时间和DM阈值。所有受试者的视力均为20/40或更好，两眼之间相差不超过或等于两行。在兰多立体视测试中得分≥6/9且在吃豆人立体视锐度测试中得分<100角分的个体被视为SN。为了区分依赖水平视差的立体相关机制与其他基于眼睛的整合机制，我们比较了近垂直和近水平方向的正弦波光栅的BR和DM。SN受试者的平均兰多得分是8.5/9，吃豆人立体视锐度为33角分，SA受试者的得分分别为2.5/9和3380角分。用中性密度滤光条测量时，SN受试者的SED平均差异为0.19，SA受试者为0.48。SA组在BR持续时间上表现出较大的眼间差异，显著大于正常水平（p = 0.004），且与立体视锐度丧失相关。此外，SA受试者的DM眼间差异同样更大（p = 0.04），尽管单眼敏感性的比例差异可能部分解释了这一点。我们还发现，SN和SA受试者的DM阈值都更高，并且在某种程度上，对垂直方向的敏感性高于水平方向。SA受试者在BR和DM方面对其优势眼都表现出异常偏向。这些数据表明，单眼敏感性和眼间抑制的共同机制可能会限制多种双眼测量，并为更好地理解弱视中立体视的异质性提供了一个实际的联系。
