Investigations of Human Cone Directionality

描述(申请人提供)：人的中心凹高度专门化，具有优异的视觉敏锐度和对比敏感度。为了提供这种能力，位于中心凹中心的视锥细胞的直径比中央凹旁的视锥细胞小。为了补偿比视锥中心更远的视锥横截面积的减少，中心凹视锥有更长的外节，因此它们的视锥感光颜料有更高的光学密度。视锥也起到天线的作用：内侧部分优先从瞳孔收集光线，并沿着外部部分引导光线。视锥细胞的这些波导特性在整个中心凹也不同，中心凹中心的视锥细胞比几百微米外的视锥细胞接受更广泛的瞳孔区域的光线。这种从光瞳收集的光的增加既提高了它们的灵敏度，也允许它们使用更宽的光瞳区域，从而具有更高的光学分辨率。因此，中心凹代表了各种因素的平衡，这些因素紧密相连，提供了良好的视觉。随着眼睛年龄的增长，这种平衡可能会改变。中心凹的曲率改变(中心凹变宽)，视锥感光色素的对称分布出现不规则性。此外，中心凹视锥的高光密度降低，变得更接近中心凹中心几度处的视锥。这种光密度的改变可能是由于外段长度的减少、光着色量的减少或锥体的波导性质的改变而发生的。在ARM早期，中心凹和副中心凹锥体的光密度降低得更多。 现代光学技术现在使我们能够直接测量控制中心凹视锥捕捉光线的光学因素。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老年性黄斑变性(ARM)患者的中心凹。我们将使用带有SLO的自适应光学成像来直接成像锥体和相关结构。我们将使用光感受器对准反射仪和视网膜密度计来测量视锥细胞的光学性质。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中视锥细胞的变化与RPE健康的关系。我们将测试RPE健康状况的变化是否与覆盖视锥的光学效率的变化有关。 这些研究将为评估作为成像系统的人眼中心凹提供一个独特的定量框架，并提供有关中心凹的功能能力如何随年龄和手臂早期变化的信息。这样的测量对于了解ARM的发育和更好地解释永久性失明之前发生的视觉并发症都是至关重要的。

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.