Department of Psychology, University of Minnesota, Minneapolis, Minnesota, United States.
Department of Psychology, Northeastern University, Boston, Massachusetts, United States.
Invest Ophthalmol Vis Sci. 2021 Oct 4;62(13):6. doi: 10.1167/iovs.62.13.6.
Binocular summation refers to better visual performance with two eyes than with one eye. Little is known about the mechanism underlying binocular contrast summation in patients with common eye diseases who often exhibit binocularly asymmetric vision loss and structural changes along the visual pathway. Here we asked whether the mechanism of binocular contrast summation remains preserved in eye disease.
This study included 1035 subjects with normal ocular health, cataract, age-related macular degeneration, glaucoma, and retinitis pigmentosa. Monocular and binocular contrast sensitivity were measured by the Pelli-Robson contrast sensitivity chart. Interocular ratio (IOR) was quantified as the ratio between the poorer and better eye contrast sensitivity. Binocular summation ratio (BSR) was quantified as the ratio between binocular and better eye contrast sensitivity.
All groups showed statistically significant binocular summation, with the BSR ranging from 1.25 [1.20, 1.30] in the glaucoma group to 1.31 [1.27, 1.36] in the normal vision group. There was no significant group difference in the BSR, after accounting for IOR. By fitting a binocular summation model Binocular = (Leftm + Rightm)1/m to the contrast sensitivity data, we found that the same binocular summation rule, reflected by the parameter m, applies across the five groups.
Cortical binocular contrast summation appears to be preserved in spite of eye diseases that can affect the two eyes differently. This finding supports the importance of assessing both monocular and binocular functions, rather than relying on a monocular assessment in the better eye as a potentially inaccurate surrogate measure.
双眼总和是指双眼的视觉表现优于单眼。对于常见眼病患者，其双眼视觉损失和视觉通路结构变化通常存在双侧不对称性，而对于这种双侧对比总和的机制知之甚少。在这里，我们想知道在眼部疾病中，双眼对比总和的机制是否仍然存在。
本研究纳入了 1035 名眼部健康、白内障、年龄相关性黄斑变性、青光眼和色素性视网膜炎患者。通过 Pelli-Robson 对比敏感度图表测量单眼和双眼对比敏感度。双眼间比值（IOR）定义为较差眼和较好眼对比敏感度的比值。双眼总和比值（BSR）定义为双眼和较好眼对比敏感度的比值。
所有组均表现出统计学显著的双眼总和，BSR 范围从青光眼组的 1.25 [1.20, 1.30]到正常视力组的 1.31 [1.27, 1.36]。在考虑 IOR 后，BSR 在各组间无显著差异。通过将双眼总和模型 Binocular = (Leftm + Rightm)1/m 拟合到对比敏感度数据中，我们发现，尽管五种疾病会导致双眼受到不同的影响，但参数 m 反映出相同的双眼总和规则适用于所有组。
尽管眼部疾病可能会导致双眼受到不同影响，但皮质双眼对比总和似乎仍然存在。这一发现支持了评估单眼和双眼功能的重要性，而不是仅仅依赖于较好眼的单眼评估作为可能不准确的替代测量方法。
