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M. Ugarte, A.A. Hussain, J. Marshall; An OCT-based Method for Determining the Elasticity of the Human Bruch's-choroid Complex: Relevance to Ageing and AMD . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1736.
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Purpose: Ageing of Bruch’s membrane is associated with a reduction in its capacity for transport of nutritional moeties and waste products. Underlying mechanisms for such reduction include deposition of debris, oxidative damage, and greater cross-linking due to both disulphide bridging and formation of advanced glycation end-products (AGE’s). The impact of these changes on the elasticity of Bruch’s membrane and its role in age-related disease remains unknown. The present investigation has assessed a potential OCT-based method for quantifying the elasticity of ageing Bruch’s-choroid in both normal and AMD donors. Methods: An open Ussing-type chamber was constructed allowing the application of a hydrostatic pressure (1500Pa) to the choroidal surface causing the preparation to bow outwards. The surface was scanned by the OCT in eight meridia and the cross-sectional profiles (after calibration in µm) were fitted to a polynomial equation allowing the calculation of the length of the tissue in each meridian. Pressure was raised to 2500Pa and the resulting increase in length determined. Donors were assessed in the age range 16-89 years. Tissue samples from donors with AMD were similarly analysed. Results: The elasticity of the Bruch’s-choroid complex was observed to decrease with ageing of donors (complex from 81 year-old donor 77.78% less elastic than sample from 16 year-old). The increased pressure resulted in homogeneous expansion of the preparation. Elasticity was considerably reduced in AMD donors (complex from 89 year-old donor with AMD 83.33% less elastic than sample from 16 year-old) and the distortion in the convex cross-sectional profile was indicative of inhomogeneity in the surface topography of the preparations. Conclusions: The study demonstrates for the first time the age-dependent decrease in the elasticity of ageing Bruch’s-choroid in normal donors. AMD donors showed an exaggerated decrease in elasticity with localised regions of considerable stiffness. The relevance of these changes to underlying structural parameters and their potential role in the development of pathological insults will be discussed.
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