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H. Aliyar, P.D. Hamilton, N. Ravi; Polymeric Hydrogel Composites as Lens Refilling Materials . Invest. Ophthalmol. Vis. Sci. 2005;46(13):820.
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Purpose: Previously, we reported a hydrogel material with reversible disulfide bonds that had viscoelastic properties comparable that of young porcine lens. Here, we extend the material property to include the correct refractive index (1.40). However, in an ideal homogeneous uniform hydrogel, it is almost impossible to have a material with high refractive index and low modulus. This is because the refractive index usually scales linearly with hydrogel concentration while the modulus scales exponentially. In this abstract, we report a novel hydrogel composite formulation showing higher refractive index and lower modulus value. Methods: Copolymer containing acrylamide (AAm) and cinnamoyloxyethylmethacrylate (CEMA, 3 mole %) was prepared. A dilute solution of this polymer was irradiated by UV light to 65% conversion of photoactive cinnamoyl chromophores and then concentrated. To this concentrated low viscous solution, we added a thiol containing acrylamide copolymer, and gelled with dithiodipropionic acid. We determined the mechanical properties of composite hydrogels (in cyclindrical shape) by compression between parallel plates using a dynamic mechanical analyzer (DMA 7e, Perkin Elmer, Norwalk, Connecticut, USA), and its refractive index using Abbe refractometer (ATAGO’s Abbe refractometer 1T/4T, Kirkland, WA, USA). Results: We evaluated several compositions and have successfully identified a class of copolymeric hydrogel composite formulation in which the refractive index and modulus values were found to be 1.409 and 0.71 kPa respectively. The refractive index and mechanical property of the porcine lens is 1.405 and 1.2 kPa. respectively. Conclusions: The copolymeric hydrogel composite exhibited low modulus with high refractive index values which have the potential for use as lens refilling materials for the preservation of accommodation after cataract surgery and possibly a surgically treatment of presbyopia.
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