Spectral photoprotection of chronic macular photochemical injury

老年性黄斑变性(AMD)和Stargardts营养不良的自身荧光变化以及对不同光化学物质在荧光双维A酸类化合物产生和修饰中作用的新理解支持这样的假设，即视网膜色素上皮(RPE)和光感受器中稳定水平的双维A酸类化合物增加会导致慢性应激和细胞损伤。重要的是，双维A酸类化合物是在视紫红质激活率高的期间由高全视网膜水平产生的，并依赖于累积的视网膜光谱辐照度。我们模拟了在不同累积环境光暴露下，在正常老化过程中，视网膜光谱辐射对RPE颗粒内视杆激活和双维A酸类物质产生以及随后的光化学氧化的影响。随着年龄的增长，绿光依赖的双维甲酸产量的显著减少被我们的模型预测的RPE颗粒内紫蓝色光化学氧化双维A酸类化合物的更大减少所抵消，这将导致未氧化的双维甲酸荧光随着年龄的增加几乎呈线性增加。Delori在正常受试者的自发荧光中观察到了这种年龄依赖性，这是年龄的函数。在广泛的累积日光照射范围内，我们的模型预测了类似的双维A类物质水平(荧光)，这主要取决于随着年龄而变黄的人类晶状体的光谱透过率。我们认为紫光对RPE颗粒中积累的双维A酸类化合物有解毒作用，这些类双维A酸类化合物主要是在明亮的日光照射期间在视杆中产生的，但随着晶状体年龄的增长，这种解毒率相对于双维A酸类化合物的生成率会下降。在正常人群中，随着老年性黄斑病变发病率的增加，RPE中未氧化双反应素类化合物的水平仅在高龄时达到细胞毒性水平。在Stargardts中，由于ABCA4功能障碍导致光感受器外节中双维A类化合物的产生增加，导致细胞毒水平在生命的早期达到，可能更依赖于累积光暴露。 我们在2004年提出，在明亮的白天佩戴简单的朱砂太阳镜会选择性地减少视杆激活和双维A酸类物质的产生。这种低成本的疾病预防策略可能在减缓或预防早期Stargardt病的疾病进展方面产生重大影响，并可能通过在一生中大幅减少双维A酸类化合物的产生来预防与年龄相关的黄斑病变。我们的朱红、保护视紫红质的光谱太阳镜应该会大大减少双维A类物质的产生，同时允许较短的波长来解毒积累的脂褐素。最近，已经提出了两种不同的治疗AMD和Stargardt病的积极药物方法，通过减缓视觉周期来显著减少视紫红质的周转，从而造成“夜盲”。我们的朱红色太阳镜在明亮的阳光下可以实现更高水平的保护，同时实际上提高了暗适应能力，最大限度地减少了夜盲。 或者，AMD和Stargardt‘s的慢性光化学应激被假设与氧化的双维A酸和它们暴露在紫蓝色光下时产生的活性氧有关。此前，我们已经在中度AMD患者中设计并测试了蓝光太阳镜。为了直接评估这些替代光假说，我们设计了双色太阳镜，其中一只眼睛配备了朱红绿色阻挡滤光片，专门保护视紫红质，另一只眼睛配备了黄色蓝紫罗兰色阻挡滤光片，专门保护眼睛免受短波长光化学损伤。在强烈的阳光下佩戴这种太阳镜，我们可以比较双眼的变化，在这种变化中，只有光谱辐照度发生变化，而遗传、生理和环境暴露在其他方面是相同的。 我们与NEI眼科诊所合作开发了使用眼底相机和共焦扫描激光眼底镜(CSLO)的临床非侵入性多光谱视网膜自发荧光成像，以便直接绘制受试者中荧光双维A类化合物的水平，并将其水平的变化与早期老年性黄斑病变和Stargardts的微观病理进展联系起来。我们已经开发了一些方案来测量和分析基于自体荧光成像的双维甲酸水平，并将这些绝对水平与局部成像的微观病理相关联。这种图像分析中的一个关键因素是校正晶状体荧光、吸收和散射以及视网膜、RPE和底层脉络膜的吸收和反射率的光学效应。我们改进了这些贡献的光学模型，并开发了多光谱自发荧光图像集的自动计算机化分析，以校正背景并一致地绘制出自发荧光RPE上方光感受器轴突的黄斑色素吸收图。我们正在使用黄斑色素分布的局部内部控制来验证我们校正的多光谱图像集。我们目前正在对这些校正的多模式图像集进行分析，以识别和描述显微视网膜病理变化以及双维甲酸水平对其发展的影响。最近，我们已经实施了新的方案，使用商业的cSLO自体荧光成像来绘制视紫红质密度图，并将其与绝对双维A类自体荧光水平的图相关联。 我们计划使用这些方法来测试光谱光保护对正常视网膜区域和细胞外RPE玻璃体所指示的早期局部RPE功能障碍区域稳态双维A水平的影响。我们目前的重点是了解网状假性玻璃体及其相关视紫红质丢失的微观病理和进展。

The associations of autofluorescence changes in age-related macular degeneration (AMD) and Stargardts Dystrophy along with new understanding of role of different photochemistries in creation and modification of the fluorescent bisretinoids support the hypothesis that rising steady-state levels of bisretinoids within the retinal pigment epithelium (RPE) and photoreceptors induce chronic stress and cellular injury. Importantly bisretinoids are created by high all-trans-retinal levels during periods of high rod rhodopsin activation rates and dependent on cumulative retinal spectral irradiance. We have modeled the effects of retinal spectral irradiance on rod activation and bisretinoid production and subsequent photochemical oxidation within RPE granules during normal aging at different cumulative ambient light exposures. Significant decreases in green-light dependent bisretinoid production with advancing age are more than offset by larger reductions in violet-blue photochemical oxidation of bisretinoids within the RPE granules predicted by our model to lead to an almost linear increase unoxidized bisretinoid fluorescence with age. Delori observed this age-dependence in the autofluorescence of normal subjects as a function of age. Over a broad range of cumulative bright daylight exposures, our model predicts similar bisretinoid levels (fluorescence) dependent mainly on the spectral transmittance of the human lens which yellows with age. We propose that violet light detoxifies the accumulated bisretinoids in RPE granules that were largely created in the rods during periods of bright daylight exposure, but this detoxification rate relative to the bisretinoid production rate declines as the lens yellows with age. In the normal population, the levels of unoxidized bisretionoids with the RPE only reach cytotoxic levels at advanced ages associated with increasing incidence of age-related macular maculopathy. In Stargardts the increased bisretinoid production in the photoreceptor outer segments due to ABCA4 dysfunction causes cytotoxic levels to be achieved earlier in life and perhaps more dependent of cumulative light exposure. We proposed in 2004, the wearing of a simple vermillion sunglass whenever in bright daylight would selectively reduce rod activation and bisretinoid production. Such low-cost disease prevention strategy might have significant impact in slowing or preventing disease progression in early Stargardt's and might prevent age-related maculopathy by dramatically reducing bisretinoid production over a lifetime. Our vermilion, rhodopsin-protecting spectral sunglasses should dramatically reduce bisretinoid production while allowing shorter wavelengths to detoxify accumulated lipofsucin. Recently two different aggressive pharmaceutical approaches to slow AMD and Stargardt's have been proposed to significantly reduce rhodopsin turnover by slowing the visual cycle, thereby create "night blindness". Our vermillion sunglasses can achieve higher levels of protection when in bright sunlight while actually improving dark-adaptation and minimizing night blindness. Alternatively chronic photochemical stress in AMD and Stargardt's has been hypothesized to be related to oxidized bisretinoids and their creation of reactive oxygen species on exposure to violet-blue light. Previously we had designed and test blue-light sunglasses in moderate AMD patients. To directly evaluate these alternative phohypotheses, we designed bicolored sunglasses in which one eye is provided a vermilion green-blocking filter that specifically protects rhodopsin and the other eye a yellow blue-violet-blocking filter that specifically protects from short-wavelength photochemical injury. When worn whenever in bright sunlight, such sunglasses allow us to compare changes in both eyes in which only spectral irradiance is changed while genetics, physiology and environmental exposures are otherwise the same. We have in conjunction with the NEI Eye Clinic developed clinical noninvasive, multispectral retinal autofluorescence imaging using both fundus cameras and confocal scanning laser ophthalmoscopes (CSLO)in order to directly map the levels of fluorescent bisretinoids in human subjects and relate changes in their levels with microscopic pathology progression in early age-related maculopathy and in Stargardts. We have developed a number of protocols for measuring and analyzing bisretinoid levels based on autofluorescence imaging and correlating those absolute levels with locally imaged micropathology. A critical factor in such image analysis is corrections for the optical effects of lens fluorescence, absorption and scattering and absorption and reflectivity of the retina, RPE and underlying choroid. We have refined optical models of these contributions and developing automatic computerized analyses of multispectral autofluorescent image sets to correct for background and consistently map macular pigment absorption in the photoreceptor axons above the autofluorescent RPE. We are using the local internal control of macular pigment distribution to validate our corrected multispectral image sets. We are currently working on analysis of these corrected multimodal image sets to identify and characterize microscopic retinal pathology changes and the effects of bisretinoid levels on their development. Recently we have implemented new protocols using commercial cSLO autofluorescence imaging to map rhodopsin density and correlate that with the maps of absolute bisretinoid autofluorescence levels. We plan to use these methodologies to test the effects of spectral photoprotection on steady state bisretinoid levels in normal retinal regions and in regions of early local RPE dysfunction as indicated by extracellular RPE drusen. We are currently focusing on understanding the micropathology and progression of reticular pseudodrusen and the associated rod (rhodopsin) loss within them.