Kwon MiYoung, Liu Rong, Patel Bhavika N, Girkin Christopher
Department of Ophthalmology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States.
Invest Ophthalmol Vis Sci. 2017 Nov 1;58(13):5810-5818. doi: 10.1167/iovs.17-22560.
Glaucoma is a leading cause of blindness worldwide, characterized by progressive loss of retinal ganglion cells. Patients with bilateral glaucoma read slower than normal cohorts. Here we examined the factors that may underlie slow reading in glaucoma and determined the best predictor of reading speed in glaucoma.
A total of 38 subjects participated in this study: 17 patients with primary open-angle glaucoma (mean age = 64.71 years) and 21 age-similar normal controls (58.24 years). For each subject, we measured binocular visual acuity (BVA); binocular contrast sensitivity (BCS); stereoacuity; visual field mean deviation (MD); and the visual span (i.e., the number of letters recognizable at one glance) known to limit reading speed. The visual span was measured with a trigram letter-recognition task in which subjects identify trigrams flashed at varying letter positions left and right of the fixation. Oral reading speed was measured with short blocks of text.
Even after controlling for age, glaucoma patients showed significantly slower reading speed (by 19%, P < 0.05) and smaller visual span (by 11 bits, P < 0.001) compared to normal controls. While their BVA was relatively normal (20/20 Snellen equivalent), their BCS (P < 0.001); stereoacuity (P < 0.001); and visual field MD (P < 0.001) showed pronounced deficits. Multiple regression analysis further revealed that reading speed in glaucoma was best predicted by the visual span.
Our results showed that slower reading speed in glaucoma was closely related to the shrinkage of the visual span. Our findings further support the view that the visual span plays a limiting role in reading speed.
青光眼是全球失明的主要原因，其特征是视网膜神经节细胞逐渐丧失。双侧青光眼患者的阅读速度比正常人群慢。在此，我们研究了可能导致青光眼患者阅读速度减慢的因素，并确定了青光眼患者阅读速度的最佳预测指标。
共有38名受试者参与了本研究：17名原发性开角型青光眼患者（平均年龄 = 64.71岁）和21名年龄相仿的正常对照者（58.24岁）。对于每个受试者，我们测量了双眼视力（BVA）；双眼对比敏感度（BCS）；立体视锐度；视野平均偏差（MD）；以及已知会限制阅读速度的视觉广度（即一眼能识别的字母数量）。视觉广度通过三字母识别任务进行测量，在该任务中，受试者识别在注视点左右不同字母位置闪烁的三字母组。口头阅读速度通过简短的文本段落进行测量。
即使在控制年龄后，与正常对照者相比，青光眼患者的阅读速度仍显著较慢（慢19%，P < 0.05），视觉广度较小（小11比特，P < 0.001）。虽然他们的BVA相对正常（相当于20/20 Snellen视力），但其BCS（P < 0.001）；立体视锐度（P < 0.001）；以及视野MD（P < 0.001）均显示出明显缺陷。多元回归分析进一步表明，青光眼患者的阅读速度最佳预测指标是视觉广度。
我们的结果表明，青光眼患者阅读速度较慢与视觉广度缩小密切相关。我们的发现进一步支持了视觉广度在阅读速度中起限制作用的观点。
