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J. R. Beattie, A. M. Pawlak, J. J. McGarvey, M. E. Boulton, A. W. Stitt; Sclera as a Possible Diagnostic Target for in-vivo Raman Analysis of Age Related Maculopathy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2789.
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Raman spectroscopy can detect and quantify advanced glycation endproduct (AGE) modifications in Bruch’s Membrane (BM) that are implicated in age related maculopathy. Detecting AGEs in vivo is hampered by laser safety limitations (<1 mW at red wavelengths) and the fact that BM is 2-6 µm thick, close to photoreceptors and lies at the rear of an f3.5 optical system. In contrast the sclera is 100-250 um thick and permits more laser versatility. Building on our experience with BM we have sought to evaluate AGEs in sclera from post-mortem eyes and whether these levels reflect BM levels.
63 Post-mortem human donor scleral and BM flat mounts were probed using a confocal Raman microscope. PLS regression was used to create a model of age related changes in BM, which was then applied to the sclera data.
BM and sclera Raman signals were very similar, both being dominated by collagen and heme, with BM spectra showing larger contribution from heme. The Raman data from the BM showed linear changes with age (R2 = 0.9), with heme and AGE signals the main contributors. Application of this model to the sclera data revealed a linear relationship, demonstrating that the spectral changes also occur in sclera. The slope of the trend in sclera data is ¼ that of BM, suggesting the changes occur at a slower rate.
Age-related spectra changes in the BM are also reflected in sclera from human eyes. This suggests that in vivo detection of Raman signals for diagnostic / prognostic use in patients could be obtained from the sclera.
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