Abstract
The ocular discomfort is the leading cause of contact lens wear discontinuation. Although the tear proteins as a lubricant might improve contact lens adaptation, some in vitro studies suggested that the amount of adsorbed proteins could not simply explain the lubricating performance of adsorbed proteins. The purpose of this study was to quantify the structural changes and corresponding ocular lubricating properties of adsorbed protein on a conventional contact lens material, poly (2-hydroxyethyl methacrylate) (pHEMA). The adsorption behaviors of lysozyme on pHEMA were determined by the combined effects of protein–surface and protein–protein interactions. Lysozyme, the most abundant protein in tear, was first adsorbed onto the pHEMA surface under widely varying protein solution concentrations to saturate the surface, with the areal density of the adsorbed protein presenting different protein–protein effects within the layer. These values were correlated with the measured secondary structures, and corresponding friction coefficient of the adsorbed and protein covered lens surface, respectively. The decreased friction coefficient value was an indicator of the lubricated surfaces with improved adaptation. Our results indicate that the protein–protein effects help stabilize the structure of adsorbed lysozyme on pHEMA with the raised friction coefficient measured critical for the innovation of contact lens material designs with improved adaptation.
Highlights
The use of contact lenses has become increasingly popular for vision correction and cosmetic reasons over prescribed spectacles [1,2]
The insertion of a contact lens into the eye does change the situation at the ocular surface [3] and often causes the wearer contact lens-related discomfort (CLD)
CLD is a condition characterized by adverse sensation [4,5] resulting from reduced compatibility between the contact lens and the ocular environment [6], which usually leads to discontinuation of contact lens wear [7]
Summary
The use of contact lenses has become increasingly popular for vision correction and cosmetic reasons over prescribed spectacles [1,2]. The insertion of a contact lens into the eye does change the situation at the ocular surface [3] and often causes the wearer contact lens-related discomfort (CLD). CLD is a condition characterized by adverse sensation [4,5] resulting from reduced compatibility between the contact lens and the ocular environment [6], which usually leads to discontinuation of contact lens wear [7]. Various factors that may be related to CLD include lens material designs [8,9]. Ocular changes such as varied tear composition and external variations, which include the use of medications, room humidity, or air temperature [10]. A more recent area of interest is lubricity and friction involved during contact lens wear, with current studies suggesting that the reduced friction between the cornea, lens surface, and lid Polymers 2020, 12, 1639; doi:10.3390/polym12081639 www.mdpi.com/journal/polymers
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