Demanins R, Hess R F
Department of Ophthalmology, Montreal, Quebec, Canada.
Vision Res. 1996 Apr;36(8):1189-93. doi: 10.1016/0042-6989(95)00181-6.
Previous studies have found that the spatial uncertainty of amblyopes is critically dependent on temporal factors. These studies claim that the spatial uncertainty is much greater at short exposure durations. We have reassessed the effect of exposure duration on the spatial uncertainty of normal and amblyopic eyes using a task in which we can compensate for the loss in contrast sensitivity which inevitably occurs as exposure duration is shortened. Our task involved a three-element alignment task, where each of the elements were spatial Gabors at two different separations. We ensured that our stimuli were always displayed at a fixed ratio above contrast detection thresholds at each exposure duration. Our results show that for normal subjects, for well separated equivisible stimuli, there is only a weak effect of exposure duration. A similar dependence is found for the dominant and amblyopic eyes of a group of strabismic amblyopes. Dominant eyes of strabismic amblyopes show increased spatial uncertainty compared with normal subjects. Amblyopic eyes of strabismic amblyopes show increased spatial uncertainty compared with their dominant fellow eye which is invariant with exposure duration. Some subjects show a larger positional deficit at short durations when the stimuli are almost abutting.
先前的研究发现，弱视患者的空间不确定性严重依赖于时间因素。这些研究称，在短曝光时长下，空间不确定性要大得多。我们重新评估了曝光时长对正常眼和弱视眼空间不确定性的影响，所采用的任务能弥补因曝光时长缩短而不可避免出现的对比度敏感度损失。我们的任务涉及一个三元素对齐任务，其中每个元素都是处于两种不同间距的空间高斯包络函数。我们确保在每个曝光时长下，我们的刺激始终以高于对比度检测阈值的固定比例显示。我们的结果表明，对于正常受试者，对于间距较大的等效可分辨刺激，曝光时长的影响很微弱。在一组斜视性弱视患者的优势眼和弱视眼中也发现了类似的相关性。与正常受试者相比，斜视性弱视患者的优势眼表现出更大的空间不确定性。与同一只优势眼相比，斜视性弱视患者的弱视眼表现出更大的空间不确定性，且这种不确定性不随曝光时长而变化。当刺激几乎相邻时，一些受试者在短时长下表现出更大的位置偏差。
