Eccentric fixation with macular scotoma.
Eccentric fixation with macular scotoma.
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DOI：
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发表时间：
1988-02
影响因子：
4.4
通讯作者：
Stephen G. Whirraker;James Dudd;ond Roger W. Cummings
中科院分区：
文献类型：
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作者：
Stephen G. Whirraker;James Dudd;ond Roger W. Cummings
有黄斑暗点的人阅读和视觉扫描的速度往往比其他视力下降但中心视野完好的人慢。我们测量了注视眼动，并考虑了注视变异性和向心眼漂移对视觉表现不佳的贡献。这些因素可能会混淆始终使用黄斑外的最佳视网膜位点的努力。我们测量单眼水平和垂直眼球运动，使用搜索线圈眼动仪，而自然发生的中央暗点或控制受试者与模拟暗点偏心固定一个单一的字符，大小为他们的视力。选择具有长期稳定黄斑病变的受试者来估计可达到的性能极限。在试图偏心注视，一个无处不在的中央凹的追求或向心漂移的倾向是没有发现，而是一个模式的漂移是特质从主题到主题。这一发现得到了32只长期存在的双眼黄斑暗点眼漂移分析的证实。此外，眼漂移速度（15-200 minarc/sec）太低，不具有功能意义。漂移速度在偏心固定与可见的目标没有显着不同的目标被熄灭后，然而，漂移速度大于在中央凹固定。这表明中央凹对缓慢的眼球运动有专门的控制。对于模拟和真实的暗点，注视变异性随着暗点的大小而增加，当暗点直径超过20 ℃时，注视变异性突然增加。一个显着的少数科目（39%）采用两个或两个以上的不同的首选视网膜位点（PRL）在固定。如果暗点的大小超过20摄氏度，则更有可能出现多个PRL。因此，当中心暗点尺寸小于约20 ℃时，可以获得合理稳定的注视。
People with macular scotoma tend to read and visually scan more slowly than others with equivalently reduced visual acuity but intact central fields. We measured fixation eye movements and considered the contribution of fixation variability and centripetal eye drift to poor visual performance. These factors might confound efforts to consistently use an optimum retinal locus outside of the macula. We measured monocular horizontal and vertical eye movements using a search coil eyetracker while subjects with naturally occurring central scotomata or control subjects with simulated scotomata eccentrically fixated a single character that was sized to their visual acuity. Motivated subjects with long-standing stable maculopathies were chosen to estimate attainable performance limits. During attempts to eccentrically fixate, an ubiquitous foveal pursuit or centripetal drift tendency was not found; rather a pattern of drift was idiosyncratic from subject to subject. This finding was confirmed by an analysis of eye drift of 32 eyes with long-standing bilateral macular scotomata. Moreover, the eye drift speeds (15-200 minarc/sec) were too low to be of functional significance. Drift speeds during eccentric fixation with a visible target were not significantly different than those after the target was extinguished; however, drift speeds were greater than during foveal fixation. This suggests that the fovea has a specialized control of slow eye movements. Fixation variability increased with scotoma size for both simulated and real scotomata, with an abrupt rise when scotomata diameters exceeded 20 degrees C. A significant minority of subjects (39%) adopted two or more distinct preferred retinal loci (PRL) during fixation. Multiple PRL were also more likely if scotoma size exceeded 20 degrees C. Reasonably steady fixation is thus attainable when central scotoma sizes are smaller than approximately 20 degrees C.