Silicone hydrogel contact lens surface analysis by atomic force microscopy: shape parameters

M. J. Giraldez; C. Garcia-Resua; M. Lira; C. Sánchez-Sellero; E. Yebra-Pimentel

doi:10.1117/12.891953

26 July 2011 Silicone hydrogel contact lens surface analysis by atomic force microscopy: shape parameters

M. J. Giraldez, C. Garcia-Resua, M. Lira, C. Sánchez-Sellero, E. Yebra-Pimentel

Proceedings Volume 8001, International Conference on Applications of Optics and Photonics; 80010C (2011) https://doi.org/10.1117/12.891953
Event: International Conference on Applications of Optics and Photonics, 2011, Braga, Portugal

Abstract

Purpose: Average roughness (R_a) is generally used to quantify roughness; however it makes no distinction between spikes and troughs. Shape parameters as kurtosis (R_ku) and skewness (R_sk) serve to distinguish between two profiles with the same R_a. They have been reported in many biomedical fields, but they were no applied to contact lenses before. The aim of this study is to analyze surface properties of four silicone hydrogel contact lenses (CL) by Atomic Force Microscopy (AFM) evaluating Ra, Rku and Rsk. Methods: CL used in this study were disposable silicone hydrogel senofilcon A, comfilcon A, balafilcon A and lotrafilcon B. Unworn CL surfaces roughness and topography were measured by AFM (Veeco, multimode-nanoscope V) in tapping mode^TM. R_a, R_ku and R_sk for 25 and 196 μm² areas were determined. Results: Surface topography and parameters showed different characteristics depending on the own nature of the contact lens (Ra/Rku/Rsk for 25 and 196 μm² areas were: senofilcon A 3,33/3,74/0,74 and 3,76/18,16/1,75; comfilcon A: 1,56/31,09/2,93 and 2,76/45,82/3,60; balafilcon A: 2,01/33,62/-2,14 and 2,54/23,36/-1,96; lotrafilcon B: 26,97/4,11/-0,34 and 29,25/2,82/-0,23). In lotrafilcon B, with the highest R_a, R_ku showed a lower degree of peakedness of its distribution. Negative Rsk value obtained for balafilcon A showed a clear predominance of valleys in this lens. Conclusions: K_ku and R_sk are two statistical parameters useful to analyse CL surfaces, which complete information from R_a. Differences in values distribution and symmetry were observed between CL.

Citation Download Citation

M. J. Giraldez, C. Garcia-Resua, M. Lira, C. Sánchez-Sellero, and E. Yebra-Pimentel "Silicone hydrogel contact lens surface analysis by atomic force microscopy: shape parameters", Proc. SPIE 8001, International Conference on Applications of Optics and Photonics, 80010C (26 July 2011); https://doi.org/10.1117/12.891953

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