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Comparative study of silicone-hydrogel contact lenses surfaces before and after wear using atomic force microscopy.

Lira M, Santos L, Azeredo J, Yebra-Pimentel E, Oliveira ME

Department of Physics (Optometry), School of Sciences, University of Minho, Portugal. mlira@fisica.uminho.pt

PURPOSE: The aim of this study was to analyze surface changes of three silicone-hydrogel contact lenses after daily wear. The lenses used in this study were balafilcon A, lotrafilcon B (both surface-treated), and galyfilcon A (non surface-treated). METHODS: To understand how and where proteins, lipids, and other contaminants change contact lenses, surface roughness was assessed through Atomic Force Microscopy Tapping Mode. Roughness parameters were Mean Surface roughness (R(a)), Mean-square-roughness (R(q)), and Maximum roughness (R(max)). The surface topography of unworn and worn lenses was also mapped in great detail. RESULTS: Contact lenses roughness parameters exhibited different values before and after wear and the surface appearance also changed. After wear, balafilcon A and galyfilcon A showed a significant increase on surface roughness parameters, being this increase more accentuated to galyfilcon A. In lotrafilcon B materials no significant changes were observed with wear. CONCLUSIONS: The present study suggests that surface treatment of silicone-hydrogel contact lenses can play a role in the prevention of a significant increase in roughness, and contribute to the better clinical tolerance of these lenses.

Published 8 April 2008 in J Biomed Mater Res B Appl Biomater, 85(2): 361-7.
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