OPTICAL AND NEURAL FACTORS IN NIGHT VISION

普遍的照明影响一个人看到空间模式的能力。 这个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可见度。 该实验室先前的研究表明，眼睛的光学质量对昏暗光线下的视力有害。 空间视觉也受到视觉神经元密度的限制，并且先前的研究表明，随着光水平降低，视网膜图像变得更粗糙地被视觉系统采样。 阈上模式的感知在昏暗的光水平下改变，这可能部分是由视觉的空间采样特性的变化引起的。 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在低亮度下异常光学质量对视觉的影响。 一个快速，客观的技术来测量眼睛的光学质量可以允许一个预测患者的视觉性能在低亮度。 改善视网膜图像质量的努力可能会增强患者的夜间视力。 2)第二个目的是量化的光学和神经的贡献，周边空间视觉在低亮度。 周边视网膜是在昏暗照明下最敏感的视网膜区域，然而对于离轴观看，眼睛的光学质量降低。 提出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，例如通过校正散光，是否会提高夜视任务的周边视野中的可见度。 外周敏感度也根据刺激方向而变化。 这些视神经敏感度的差异部分是由于光学散光，但它们也可能具有神经起源。 将通过用直接在视网膜上形成的干涉条纹测量空间对比敏感度来检查不同取向的神经敏感度。 3.）第三章第三个目的是研究不同刺激方向的周围神经元的采样密度。 视网膜神经元的密度可以从心理物理学的研究中推断出来。 在昏暗的照明下，混叠反映了比视网膜光感受器更近端的神经元的采样率。将检查各种刺激方向的混叠，以确定某些方向的采样率是否更粗糙。 采样率的差异可能是灵敏度随时间变化的原因。

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.