OPTICAL AND NEURAL FACTORS IN NIGHT VISION

普遍的照明会影响一个人看清空间图案的能力。该项目的长期目标是解释人类视觉系统中的光学和神经因素如何影响低亮度下的空间能见度。这个实验室先前的研究表明，在昏暗的光线下，眼睛的光学质量对视力有害。空间视觉也受到视神经元密度的限制，先前的研究表明，随着光照水平的降低，视觉系统对视网膜图像的采样变得更加粗糙。在昏暗的光线水平下，对阈值以上模式的感知会发生变化，这可能部分是由于视觉的空间采样特性的变化造成的。这项拟议的研究包括对人类观察者的行为实验。1)第一个具体目标是研究低亮度下光学质量异常对视觉的影响。一种快速、客观的测量眼睛光学质量的技术可以让人们预测患者在低亮度下的视觉表现。改善视网膜图像质量的努力可能会增强患者的夜视能力。2)第二个目标是量化低亮度下光学和神经对周围空间视觉的贡献。周边视网膜是弱光下最敏感的视网膜区域，但在离轴观察时，眼睛的光学质量会降低。建议进行实验来测量正常眼睛的周边光学质量，并确定周边光学的增强(例如通过矫正散光)是否会改善夜视任务中周边视野中的能见度。外周敏感性也随着刺激方向的不同而不同。这些经络敏感度的差异部分是由于光学散光，但也可能与神经起源有关。神经敏感度将通过测量直接在视网膜上形成的干涉条纹的空间对比敏感度来检测不同方向的神经敏感度。3.)第三个目的是研究不同刺激方向的外周神经元的采样密度。视网膜神经元的密度可以从心理物理学的混叠研究中推断出来。在昏暗的光照下，混叠反映了比视网膜光感受器更近的神经元阶段的采样率。将检查不同刺激方向的混叠，以确定某些方向的采样率是否较粗。采样率的差异可能是造成灵敏度经向差异的原因。

The prevailing illumination affects one's ability to see spatial patterns. The long term goals of this project are to explain how optical and neural factors in the human visual system affect spatial visibility at low luminance. Prior research in this laboratory shows that the eye's optical quality is detrimental for vision in dim light. Spatial vision is also limited by the density of visual neurons and the prior research indicates that the retinal image becomes more coarsely sampled by the visual system as the light level decreases. The perception of suprathreshold patterns is altered at dim light levels and this may be caused, in part, by changes in the spatial sampling properties of vision. The proposed study is comprised on behavioral experiments on human observers. 1) The first specific aim is to study the effects of abnormal optical quality on vision at low luminance. A rapid, objective technique to measure the eye's optical quality may allow one to predict a patient's visual performance at low luminance. Efforts to improve retinal image quality may enhance the patient's night vision. 2) The second aim is to quantify the optical and neural contributions to peripheral spatial vision at low luminance. The peripheral retina is the most sensitive retinal area under dim illumination, yet the optical quality of the eye is reduced for off-axis viewing. Experiments are proposed to measure the peripheral optical quality in normal eyes and to determine whether enhancement of the peripheral optics, such as by correcting astigmatism, would improve visibility in the peripheral visual field for night vision tasks. Peripheral sensitivity also varies according to the stimulus orientation. These meridional differences in sensitivity are due, in part, to optical astigmatism but they may also have a neural origin. Neural sensitivity will be examined for different orientations by measuring spatial contrast sensitivity with interference fringes that are formed directly on the retina. 3.) The third aim is to investigate the sampling density of peripheral neurons for different stimulus orientations. The density of retinal neurons can be inferred from psychophysical studies of aliasing. Under dim illumination, aliasing reflects the sampling rate of a more proximal stage of neurons than the retinal photoreceptors. Aliasing will be examined for various stimulus orientations to determine if the sampling rate is coarser for certain orientations. Differences in the sampling rate may responsible for the meridional variation in sensitivity.