Duke Eye Center, Department of Ophthalmology, Duke University, Durham, North Carolina, United States.
Entropy Control, La Jolla, California, United States.
Invest Ophthalmol Vis Sci. 2019 Feb 1;60(2):538-543. doi: 10.1167/iovs.18-25150.
Crowding refers to the phenomenon in which objects that can be recognized when viewed in isolation are unrecognizable in clutter. Crowding sets a fundamental limit to the capabilities of the peripheral vision and is essential in explaining performance in a broad array of daily tasks. Due to the effects of glaucoma on peripheral vision, we hypothesized that neural loss in the disease would lead to stronger effects of visual crowding.
Subjects were asked to discriminate the orientation of a target letter when presented with surrounding flankers. The critical spacing value (scritical), which was required for correct discrimination of letter orientation, was obtained for each quadrant of the visual field. scritical values were correlated with standard automated perimetry (SAP) mean sensitivity (MS) and optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurements.
The study involved 13 subjects with mild glaucomatous visual field loss and 13 healthy controls. Glaucomatous eyes had significantly greater (worse) scritical than controls (170.4 ± 27.1 vs. 145.8 ± 28.0 minimum of visual angle, respectively; P = 0.007). scritical measurements were significantly associated with RNFL thickness measurements (R2 = 26%; P < 0.001) but not with SAP MS (P = 0.947).
In glaucoma patients, a pronounced visual crowding effect is observed, even in the presence of mild visual field loss on standard perimetry. scritical was associated with the amount of neural loss quantified by OCT. These results may have implications for understanding how glaucoma patients are affected in daily tasks where crowding effects may be significant.
拥挤是指当孤立地观察时可以识别的物体在杂乱无章的情况下变得无法识别的现象。拥挤现象限制了周边视觉的能力，对于解释广泛的日常任务中的表现至关重要。由于青光眼对视神经的损害，我们假设这种疾病导致的神经损失会导致视觉拥挤效应更强。
要求受试者在周围有侧翼的情况下辨别目标字母的方向。正确辨别字母方向所需的关键间隔值（scritical）是通过每个视野象限获得的。scritical 值与标准自动视野计（SAP）平均敏感度（MS）和光学相干断层扫描（OCT）视网膜神经纤维层（RNFL）厚度测量值相关。
本研究涉及 13 名轻度青光眼视野丧失患者和 13 名健康对照者。青光眼患者的 scritical 值显著大于（更差）对照组（分别为 170.4 ± 27.1 和 145.8 ± 28.0 最小视角；P = 0.007）。scritical 值与 RNFL 厚度测量值显著相关（R2 = 26%；P < 0.001），但与 SAP MS 无关（P = 0.947）。
在青光眼患者中，即使在标准视野计上存在轻度视野丧失，也会观察到明显的视觉拥挤效应。scritical 值与 OCT 定量的神经损失量相关。这些结果可能对理解青光眼患者在拥挤效应可能显著的日常任务中受到的影响具有重要意义。
