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Scott Perry, Jessica Rex, Alex Rudy, Jennifer Lane, Leroy Muya; Compositional and Frictional Analysis of a Copolymer Solution Treatment of Silicone Hydrogel Contact Lens Surfaces. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6100.
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The surface chemical compositions of three brands of contact lenses were analyzed using X-ray photoelectron spectroscopy (XPS) prior to and following treatment in a test solution of diblock copolymer of polyethylene oxide and polybutylene oxide (nEO-BO). Atomic force microscopy (AFM) was also employed to evaluate the surface topography and frictional properties of these lenses prior to and following similar solution treatments.
Three silicone hydrogel lens types (balafilcon A, lotrafilcon B, and comfilcon A) were tested. Lenses were soaked for a minimum of 8 hours in nEO-BO hydrogen peroxide solution (3% peroxide) in AOSept lens cases. For surface compositional analysis with XPS, lenses have been prepared through a vacuum drying procedure, in which the hydrogel is taken from a fully hydrated state directly to an ultraclean, ultrahigh vacuum environment. Colloidal probe AFM was used to measure the frictional properties of the treated lens surfaces in aqueous environments.
Prior to treatment, differences in surface elemental composition of the various lenses were found to reflect known bulk compositions and/or respective surface treatments. Following solution treatment, photoelectron intensity attributable to the uptake of the block copolymer on the surface was apparent for balafilcon A (19.4±9.5%) and lotrafilcon B (38.5±27.2). Only modest changes in surface composition were observed for comfilcon A. AFM measurements in saline revealed large disparities in the impact of copolymer adsorption on the coefficients of friction, with balafilcon A (85% reduction) and lotrafilcon B (82% reduction) exhibiting the largest changes. In contrast, only small changes in friction attributable to copolymer uptake were observed for comfilcon A.
Together, these results depict a correlation between the lens surface composition and the impact of polymer adsorption on the frictional response of silicone hydrogel lenses. The results indicate this specific diblock copolymer consisting of polyethylene oxide and polybutylene oxide can have a positive impact on the lubrication properties of certain silicone hydrogel lenses.
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