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TitleThe effect of lens wear on refractive index of conventional hydrogel and silicone-hydrogel contact lenses: a comparative study
Author(s)Lira, Madalena
Santos, Lívia
Azeredo, Joana
Yebra-Pimentel Vilar, Eva
Oliveira, M. Elisabete
KeywordsRefractive index
Automated refractometer CLR 12-70
Silicone-hydrogel contact lenses
Conventional hydrogel contact lens
Equilibrium water
Equilibrium water content
Issue dateApr-2008
PublisherElsevier Ltd.
JournalContact Lens and Anterior Eye
CitationContact Lens & Anterior Eye". ISSN 1367-0484. 31:2 (Apr. 2008) 89-94.
Abstract(s)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 < 0.001). Conclusion: The results presented here show that after being worn the silicone-hydrogel contact lens, show more capacity to retain or to reach their initial equilibrium water content than conventional hydrogel contact lenses. This suggests that the silicone-hydrogel contact lenses are less susceptible to spoilation over time maintaining its biocompatibility and contributing to the clinical success of lens performance.
AccessOpen access
Appears in Collections:CEB - Publicações em Revistas/Séries Internacionais / Publications in International Journals/Series

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