Imaging Protein Deposits on Contact Lens Materials

Abstract

Imaging techniques that allow proteins to be examined in situ show much promise for determining the extent and physical characterization of protein on contact lens materials. These techniques indicate that the pattern of deposition of proteins onto silicone hydrogel contact lens materials differs between materials, depending upon their bulk and surface composition.

Hydrogel Contact Lenses Surface Roughness and Bacterial Adhesion

“…Although the hioxifilcon-based contact lens contains MA, which should determine a greater surface roughness, its similar Ra to senofilcon A could be attributed to its high water content. As may be observed in Figure 3, senofilcon A shows a granulated surface structure, which is similar to that previously reported for the AFM observation of senofilcon A (Teichroeb et al, 2008), of galyficon A and for the cryogenic SEM visualization of the latter. (Gonzalez-Meijome et al, 2006b) Galyfilcon A is a non surface-treated silicone hydrogel contact lens that contains PVP as an internal wetting agent.…”

“…The roughness parameters obtained for these lenses were similar to those observed previously in silicone-hydrogel contact lenses lacking surface treatment, such as galyfilcon A and comfilcon A Gonzalez-Meijome et al, 2009), but lower than those reported for surface-treated designs (Gonzalez-Meijome et al, 2006a;Guryca et al, 2007). Despite the similar surface appearance of silicone hydrogels included here and those examined by others, (Teichroeb et al, 2008; Gonzalez-Meijome et al, 2009) Teichroeb et al observed higher roughness parameters for senofilcon A than Comfilcon A when measuring a 25 μm 2 area. These differences could be related to the fact that the lenses were analysed after drying in ambient conditions for 15 minutes.…”

“…Atomic force microscopy (AFM) provides detailed information on the surface characteristics of contact lenses (Bhatia et al, 1997;Baguet et al, 1993;Baguet et al, 1995;Bruinsma et al, 2003;Lira et al, 2008;Guryca et al, 2007;Gonzalez-Meijome et al, 2006a;Gonzalez-Meijome et al, 2009;Teichroeb et al, 2008;Maldonado-Codina and Efron, 2005) and is a powerful tool for the high resolution examination of the structure of the hydrated contact lens surface. The method has the advantages that it avoids artefacts due to dehydration and coating (Bhatia et al, 1997;Kim et al, 2002), and allows for non-destructive surface topography and roughness measurements.…”

Impact of Ethylene Oxide Butylene Oxide Copolymers on the Composition and Friction of Silicone Hydrogel Surfaces

“…A second group of lenses includes ACUVUE Ò OASYS Ò (senofilcon A) and ACUVUE Ò ADVANCE Ò (galyfilcon A), which both incorporate poly(vinylpyrrolidone), or PVP, in their lens chemistry, resulting in greater similarities between the bulk and the surface compositions [7,10]. A third generation of SH lenses employs an entirely different silicone chemistry, entailing neither an internal wetting agent nor surface plasma treatment, to achieve the desired combination of high oxygen permeability and hydrophilicity [10].…”

“…In general, these studies have shown that contact lens hydrogels have surfaces that are not usually at thermodynamic equilibrium when used in the ocular environment and, as a result, there can be significant changes in the surface chemistry over time due to the migration of hydrophobic groups to the air/lens interface. To overcome these dynamic changes, the surfaces have been modified through plasma treatment, the inclusion of free polymers into the lenses' matrix, and/or the soaking of lenses in saline solutions containing block copolymers to physically modify the surfaces [1,6,7,9,10,13].…”