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Tatyana Svitova, Meng Lin; Effects of lens care solutions on dynamic interfacial properties of human tear lipids. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6036.
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© ARVO (1962-2015); The Authors (2016-present)
To study interfacial dynamics and rheological properties of human tear lipids extracted from Schirmer strips (SSL) and effects of three lens-care solutions (LCS) on SSL’s interfacial behaviors.
SSL samples were collected from 6 healthy subjects. Sessile bubble tensiometry was used to study interfacial properties of SSL, LCS or a mixed film (SSL+LCS) at 22 ° C. SSL was deposited on an air bubble to form 100±20 nm-thick films. SSL films were subjected to expansion-compression cycles with the film area changing from ~5 to 50 mm2. Two ml of LCS (Baush&Lomb BioTrue [BT], Alcon PureMoist [PM], or AMO Revitalens [RL]) was injected into a cell (LCS:Model Tear Electrolytes(MTE)=1:12 v:v) and equilibrated without or with SSL film for 2 hours. The dynamic rheological properties of the films were assessed. Then MTE was pumped through the cell to remove LCS from bulk and SSL dynamic properties were re-evaluated.
Equilibrium surface tension (EST), elasticity modulus (E) and relaxation times (τ) of SSL alone were 22±2.1 mN/m,10.7-14.8 mN/m and 80-150 s, correspondingly. EST for LCS alone was 40.3±1.5 for BT, 33.4±1.0 for PM, and 30.1±0.8 mN/m for RL. E of all three LCS was 5 -8.5 mN/m while τ was 33-55 s. After washout, EST of LCS films increased to 43±1.2, 35.1±1.1, and 32.1±0.8 mN/m for BT, PM and RL, suggesting irreversible adsorption of some LCS components. For mixed SSL+LCS films, EST remained unchanged (22±2.1 mN/m). For all mixed films, E was 0.2-0.5 mN/m and τ was 50-60 s; the shape of surface pressure vs. area per microgram (π-A) iso-cycles was altered dramatically. The hysteresis Δπ (Δπ=πmax-πmin) was initially 48mN/m and diminished to 25 mN/m for BT and RL, and to 21.5 mN/m for PM-treated SSL. These changes persisted after LCS washout for >24 hours, implying binding interactions between SSL and some components of LCS.
Some components of LCS adsorb and bind irreversibly to thick SSL films and make these gel-like SSL films less viscous and less elastic, resembling condensed-liquid films. Clinical implications of these findings suggest a possibility of tear lipids film destabilization upon exposure to LCS.
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