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T. F. Svitova, M. C. Lin; The Effect of Lens-Care Solutions on Reconstituted ex vivo Lipids Rheological Behavior and Interaction With Model Tear Proteins. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4864.
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© ARVO (1962-2015); The Authors (2016-present)
Contact lens patients who develop lens-induced dry-eye conditions find different degrees of relief from different lens care products. In this study, a novel technique was employed to investigate the effect of lens-care solutions (LCS) on the mixed protein-lipid layers .
Sessile bubble tensiometry was used to examine interfacial properties of reconstituted ex-vivo lipids extracted from Focus N&D lenses worn by10 healthy subjects on continuous-wear basis for 1 month. Reconstituted lipids were deposited on the surface of air-bubble immersed into buffered saline. The interfacial properties and rheology of these ex-vivo lipid layers were studied in the absence and presence of Lysozyme in aqueous phase (1-2 mg/ml). The Lysozyme-loaded lipid-layers were exposed to 1:20 dilute either Optifree Express (OFX) or Optifree Replenish (OFR) LCS. After 30 min of exposure, the care solutions were washed out from the bulk phase. The interfacial rheological parameters of the remaining layers were evaluated and compared with that of the initial mixed lipids-protein layers.
There was little inter- and intra-subject variability in surface tension of the reconstituted ex-vivo lipid layers (Mean ± SD = 25 ± 3 mN/m). The rheological parameters such as storage modulus (E), and interfacial viscosity (υin,) were also found to be similar among subjects. E measured in pure buffer was 23 ± 2 mN/m for compression and 26 ± 2 mN/m for expansion steps. Lysozyme adsorbed irreversibly onto reconstituted lipid layer. Interaction of ex-vivo lipids with Lysozyme slightly reduced E , while υin became 1.2-1.5 times higher indicating slower relaxation of mixed layer. 30-min exposure of these layers to OFX caused a significant decrease in E (4 ± 1 mN/m; p 0.05).
The formation of interfacial lipid-protein complex produced a noticeable effect on interfacial elasticity and viscosity of reconstituted lipid layers. OFR displaced protein from mixed layers but did not change their interfacial behavior. In contrast, OFX had a profound effect. These results suggest that different lens care solutions may produce different effect on the stability of the tear film. Some of them might cause adverse alterations in the rheological behavior of lipids and their interaction with tear proteins.
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