The effect of lens wear on refractive index of conventional hydrogel and silicone-hyd

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The effect of lens wear on refractive index of conventional hydrogel and silicone-hydrogel contact lenses: a comparative study. Cont Lens Anterior Eye. 2008 Apr;31(2):89-94 Authors: Lira M, Santos L, Azeredo J, Yebra-Pimentel E, Real Oliveira ME PURPOSE: The purpose of this work was to evaluate the ability of four silicone-hydrogel contact lenses (galyfilcon A, balafilcon A, lotrafilcon A and lotrafilcon B) to retain their equilibrium water content before and after wear, through measurements of refractive index and compare with that of a conventional disposable hydrogel contact lens (etafilcon A). METHODS: The refractive indices of 115 contact lenses were measured using an automated refractometer (CLR 12-70, Index Instruments, Cambridge, U.K.) before and after a schedule of daily wear by 58 patients for 30 days in the case of silicone-hydrogel lenses and 15 days for the conventional contact lenses. RESULTS: In the silicone-hydrogel contact lenses the changes on the refractive indices were not statistically significant, however after being worn the refractive index of the conventional etalfilcon A hydrogel contact lens increased significantly (p