OPTICAL AND RETINAL LIMITS TO VISUAL PERFORMANCE

描述(研究人员摘要)：这项研究的长期目标 该计划旨在确定光学和视网膜因素如何影响视力。 下一个项目期的具体目标分为三类： 敏锐度、混叠和光学。 视力是临床上衡量视功能的最重要的指标 实践，它在当前关于限制的辩论中起着关键作用 视觉系统的神经结构所强加的性能。 此前的实验表明，在周边视觉中，分辨率 由于神经采样不足，混叠的模糊性限制了敏锐度 视网膜图像，可能是由相对稀疏的视网膜阵列 神经节细胞。研究人员提议测试这种神经节细胞 通过将人类观察者的分辨率敏锐度映射到 使用混叠标准的整个视野，这是一项心理物理任务 这是已知的采样受限的，然后将结果与 神经节细胞密度的最新解剖学估计。通过这种方式， 研究人员旨在确定神经节细胞的功能意义 密度为正常的外周视力，因此神经的后果 患眼的纤维丢失。 混叠是对模式过于精细而无法解决的错误认知。 这种幻觉自然发生在周边视力中，原因是 神经采样不足。混叠图像功能实用的证据 将通过对比消除锯齿前后的视觉表现来进行对比 视觉刺激的过滤。高次谐波的分辨与检测 将测量周边视力的模式并将结果进行比较 用所得到的正弦光栅来确定如何更高 频率、不可分辨组件会影响性能。这种方法 将被改编用于临床周边视力测试 由于混叠而可见的条纹字母光印，与 字母的大小。有了这样的目标，调查人员预计 在临床环境中演示混叠，从而利用必要的 黄斑中心凹和周边视力的差异可能具有诊断意义 对青光眼和其他以死亡为特征的眼病的价值 视网膜神经节细胞。 通过眼睛对视网膜图像进行光学过滤代表了潜在的 任何视觉任务的限制因素。最近，调查人员已经 开发了一个简单的示意图眼睛，很好地解释了 视觉上的色差和衍射。唯一的自由参数 该模型涉及到瞳孔相对于眼睛结节的位置 点和视轴。调查人员现在提议对 多个单眼的瞳孔位置分布 一种先前开发的双色游标对准技术。这个 研究人员还建议研究轴向瞳孔的重要性。 对模型眼的调制传递函数进行定位和扩展 这些理论计算要包括颜色对比度。

DESCRIPTION (Investigator's abstract): The long term goal of this research program is to determine how optical and retinal factors affect vision. Specific aims for the next project period fall into three categories: acuity, aliasing and optics. Acuity is the most important measure of visual function in clinical practice and it plays a key role in current debates about the limits to performance imposed by the neural architecture f the visual system. Previous experiments have shown that in peripheral vision, resolution acuity is limited by the ambiguity of aliasing due to neural undersampling of the retinal image, probably by the relatively sparse array of retinal ganglion cells. The investigators propose to test this ganglion cell hypothesis by mapping the resolution acuity of the human observer over the entire visual field using the aliasing criterion, a psychophysical task which is known to be sampling-limited, and then comparing the results with recent anatomical estimates of ganglion cell density. In this way the investigators aim to establish the functional significance of ganglion cell density for normal peripheral acuity, and thus the consequences of nerve fiber loss in the diseased eye. Aliasing is the false perception of a pattern too fine to be resolved. Such illusory percepts occur naturally in peripheral vision and are due to neural undersamplng. Evidence of the functional utility of aliased images will be south by comparing visual performance before and after anti-alias filtering of visual stimuli. Resolution and detection of harmonically-rich patterns will be measured for peripheral vision and the results compared with that obtained for sinusoidal grating to determine how the higher frequency, non-resolvable components affect performance. This approach will be adapted for clinical testing of peripheral vision by employing a striped-letter optotype which is visible due to aliasing independently of the size of the letter. With such targets the investigators expect to demonstrate aliasing in a clinical context and thus exploit an essential difference between foveal and peripheral vision which may have diagnostic value for glaucoma and other ocular diseases characterized by the death of retinal ganglion cells. Optical filtering of the retinal image by the eye represents a potential limiting factor for any visual task. Recently the investigators have developed a simple schematic eye which accounts well for the effects of chromatic aberration and diffraction on vision. The only free parameters of the model involve the position of the pupil relative to the eye's nodal point and visual axis. The investigators now propose to survey the distribution of pupil locations in a large number of individual eyes using a previously developed, two-color vernier-alignment technique. The investigators also propose to examine the importance of axial pupil location on the modulation transfer function of the model eye and to extend these theoretical calculations to include color contrast.