Patients with central vision loss are forced to use an eccentric retinal location as a substitute for the fovea, called a preferred retinal locus, or PRL. Clinical studies have shown that patients habitually choose a PRL located either to the left, and/or below the scotoma in the visual field. The position to the right of the scotoma is almost never chosen, even though this would be theoretically more suitable for reading, since the scotoma no longer blocks the upcoming text. In the current study, we tested whether this asymmetry may have an oculomotor basis. Six normally sighted subjects viewed page-like text with a simulated scotoma, identifying embedded numbers in "words" comprising random letters. Subjects trained and tested with three different artificial PRL ("pseudo-PRL," or pPRL) locations: inferior, to the right, or to the left of the scotoma. After several training blocks for each pPRL position, subjects were found to produce reliable oculomotor control. Both reading speed and eye movement characteristics reproduced observations from traditional paradigms such as page-mode reading and RSVP for an advantage for an inferior pPRL. While left and right positions resulted in similar reading speeds, we observed that a right pPRL caused excessively large saccades and more direction switches, exhibiting a zig-zag pattern that developed spontaneously. Thus, we propose that patients' typical avoidance of pPRL positions to the right of their scotoma could have an oculomotor component: the erratic eye motion might potentially negate the perceptual benefit that this pPRL would offer.

中文翻译：

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模拟中央视力丧失中阅读眼球运动的不对称性。


中心视力丧失的患者被迫使用偏心的视网膜位置来代替中央凹，称为首选视网膜位置（PRL）。临床研究表明，患者习惯性地选择位于视野中暗点左侧和/或下方的 PRL。几乎从未选择过暗点右侧的位置，尽管理论上这更适合阅读，因为暗点不再阻挡即将到来的文本。在当前的研究中，我们测试了这种不对称是否可能具有动眼神经基础。六名视力正常的受试者观看带有模拟暗点的页面状文本，识别由随机字母组成的“单词”中嵌入的数字。受试者使用三个不同的人工 PRL（“伪 PRL”或 pPRL）位置进行训练和测试：暗点的下方、右侧或左侧。对每个 pPRL 位置进行几次训练后，发现受试者能够产生可靠的动眼神经控制。阅读速度和眼球运动特征都再现了传统范式（例如页面模式阅读和 RSVP）的观察结果，从而为较差的 pPRL 带来了优势。虽然左侧和右侧位置导致相似的阅读速度，但我们观察到右侧 pPRL 导致过大的扫视和更多的方向转换，表现出自发形成的锯齿形图案。因此，我们认为，患者典型地回避 pPRL 位于暗点右侧的位置可能具有动眼神经成分：不稳定的眼球运动可能会抵消该 pPRL 所提供的感知益处。