DESCRIPTION (provided by applicant): Better understanding of the pathophysiology of the early stages of age-related maculopathy (ARM) may guide development of better treatments and/or preventions of age-related macular degeneration. Prominent clinical and histopathologic lesions of early ARM involve Bruch's membrane, a thin connective tissue between the choriocapillaris and the RPE. Unlike the case for late ARM, for which several risk factors have been identified, the only consistently identified risk factor for early ARM is advanced age. It is, therefore, important to understand how age-related changes in Bruch's membrane predispose some individuals for retinal dysfunction. A decreased transport capacity of Bruch's membrane, perhaps caused by lipid accumulation, has been postulated to be a critical early event in the pathogenesis of ARM. However, morphometric studies have not yet been successful in identifying those moieties responsible for limiting the transport capacity of Bruch's membrane. QFDE is a morphological technique that preserves extracellular matrix in exquisite detail and allows structures to be visualized that are not seen using conventional transmission electron microscopy (TEM) techniques. QFDE offers a technology that, in other connective tissues, has provided new insights into the transport characteristics of these tissues. Our goal is to combine the technique of quick-freeze/deep-etch (QFDE) morphology with bioengineering analytic methods to evaluate this hypothesis, using well-preserved eyes from normal human donors. Our specific aims are (i) to use the methods of quick-freeze/deep-etch (QFDE) morphology and lipid histochemistry in conjunction with conventional electron microscopy methods to characterize quantitatively the earliest ultrastructural changes in Bruch's membrane associated with lipid deposition in 20-70 year old donor eyes; (ii) to combine these results with analytical bioengineering tools to evaluate the effects of age-related changes on transport properties of Bruch's membrane; and (iii) to use an in vitro model of fluid and lipid transport through extracellular matrix to validate the results of the analytical studies and characterize the impact of lipid accumulation on transport.