Investigations of Human Cone Directionality

描述（由申请人提供）：人类中央凹高度专门化，具有出色的视觉敏锐度和对比敏感度。为了提供这种能力，中央凹中心的锥体的直径小于翼旁锥体。为了补偿相对于远离中心的视锥的横截面积的减小，中央凹视锥具有较长的外段，因此其视锥色素的光密度较高。视锥细胞也起到了天线的作用：内节优先收集来自瞳孔的光，并沿着外节引导光。视锥的这些波导特性也在中央凹上变化，中央凹中心的视锥接受来自瞳孔的更宽区域的光，而不是仅仅几百微米远的视锥。这种增加的来自瞳孔的光的收集既增加了它们的灵敏度，也允许它们使用瞳孔的更宽区域，从而具有更高的光学分辨率。因此，中央凹代表了紧密耦合以提供良好视力的因素的平衡。随着年龄的增长，这种平衡可能会改变。中央凹的曲率改变（中央凹凹变宽），并且出现锥体色素对称分布的不规则性。此外，中央凹视锥的高光学密度降低，变得更类似于远离中央凹中心几度的视锥。光密度的这种变化可能是由于外段长度的减小、光色素量的减少或锥体的波导特性的变化而发生的。早期ARM的光密度的中心凹和旁视锥下降甚至更多。 现代光学技术现在允许我们直接测量控制中央凹锥体捕获光的光学因素。我们将使用最先进的仪器和分析技术来研究正常人和早期年龄相关性黄斑变性（ARM）患者的中心凹。我们将使用自适应光学成像与SLO直接成像锥和相关结构。我们将使用光感受器排列反射计和视网膜密度计来测量视锥细胞的光学特性。我们将通过测量近红外光散射和脂褐素荧光来确定衰老和早期ARM中锥体与RPE健康的变化。我们将测试RPE健康的变化是否与上覆视锥细胞的光学效率的变化有关。 这些研究将提供一个独特的定量框架，用于评估作为成像系统的人眼的中央凹，并提供有关中央凹的功能能力如何随着年龄和早期ARM的变化的信息。这种测量将是至关重要的了解ARM的发展，并更好地解释视觉并发症之前发生的永久性视力丧失。

DESCRIPTION (provided by applicant): The human fovea is highly specialized for excellent visual acuity and contrast sensitivity. To provide this capability the cones in the center of the fovea are smaller in diameter than parafoveal cones. To compensate for the decreases in cross sectional area relative to cones further from the center, the foveal cones have longer outer segments, and therefore a higher optical density of their cone photopigments. The cones also act as antennae: the inner segments collect light preferentially from the pupil and guide the light along the outer segments. These waveguide properties of the cones also vary across the fovea, with the cones in the foveal center accepting light from a wider region of the pupil than cones just a few hundred microns away. This increased collection of light from the pupil both increases their sensitivity and also allows them to use a wider region of the pupil, and thereby have higher optical resolution. Thus, the fovea represents a balance of factors which are tightly coupled to provide excellent vision. As the eye ages this balance may change. The curvature of the fovea changes (the foveal pit widens) and irregularities in the symmetric distribution of the cone photopigment appear. In addition, the high optical density of the foveal cones decreases, becoming more similar to cones a few degrees away from the center of the fovea. This change in optical density may occur due to either a decrease in the outer segment length, decreases in the amount of photopigment, or changes in the waveguide properties of the cones. With early ARM the optical density of both the foveal and parafoveal cones decrease even more. Modern optical technology now allows us to directly measure the optical factors controlling the capture of light by the foveal cones. We will use state of the art instrumentation and analysis techniques to study the fovea in normals and patients with early age-related macular degeneration (ARM). We will use adaptive optics imaging with an SLO to directly image the cones and related structures. We will use photoreceptor alignment reflectometry and retinal densitometry to measure the optical properties of the cones. We will relate changes to the cones in aging and early ARM to RPE health, determined by measuring near infrared light scattering and lipofuscin fluorescence. We will test whether changes in RPE health are related to changes in the optical efficiency of the overlying cones. These studies will provide a unique quantitative framework for evaluating the fovea of the human eye as an imaging system, and provide information on how the functional capacities of the fovea change with both age and early ARM. Such measurements will be critical for both understanding the development of ARM, and to better explain visual complications that occur prior to the permanent loss of vision.