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Scott S. Perry, Yuchen Huo, Alexander Rudy, Shannon Brown, Howard A. Ketelson, David L. Meadows; Topography and Morphology of Silicone Hydrogel Contact Lens Surfaces Probed by Atomic Force Microscopy: The Effect of Copolymer Solution Treatment. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6539.
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The surfaces of three types of silicone hydrogel (SH) contact lenses (PureVision®, O2 OPTIX®, and ACUVUE® OASYS®) were analyzed using atomic force microscopy (AFM) in aqueous environment. The influence of lens preparation, solution treatment with diblock copolymers (polyethylene oxide-co-polybutylene oxide), and lens wear on surface topography and morphology were evaluated.
Lens samples prepared in various manners were imaged by intermittent contact mode AFM. A liquid sample holder was modified to ensure that samples were amply hydrated for the duration of the measurements. Images were generated by plotting deviations of the free, driven amplitude as a function of x-y position across the surface. Quantitative topographical and phase evaluation of the surfaces was obtained via statistical image processing.
Qualitative and quantitative changes in surface topography were observed as a result of soaking the lenses in the test solution and lens wear, as compared to pristine lens. The extent of such changes was a function of each lens type’s original surface features. When compared to samples soaked in buffered saline (Unisol 4®) prior to wearing, worn lenses that were pre-soaked in the test solution revealed statistically different degree of alteration on surface roughness. Phase changes of the lens samples following their respective treatments were also apparent, indicative of changes in the viscoelastic nature of the hydrogel materials. These observations indicated that surface topography and morphology differences amongst the lens groups may impact lubrication, wetting and tear film deposition properties of lenses.
Together, these results suggest that lens morphology differs among lens types and can be modified through solution treatment and/or interactions with tear film components.
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