UC Berkeley

Purpose: To evaluate the influence of lens care solutions (LCS) on interfacial dynamics and rheological properties of human tear-lipid films. Methods: Tear lipids were extracted from Schirmer strips collected from 6 healthy subjects. Sessile bubble tensiometry was used to study interfacial properties at 22. °C. Lipids were deposited on an air bubble immersed into electrolytes solution to form 90. ±. 20. nm films. Lipid films were subjected to expansion-compression cycles for dynamic interfacial properties and to step-strain relaxations for assessments of rheological properties. LCS (BioTrue [BT], PureMoist [PM], Revitalens [RL], ClearCare [CC]) were injected into optical chamber and equilibrated for 2. h without or with lipid films. Dynamic interfacial properties of films were measured. Then electrolyte solution was pumped through chamber and properties of films were re-evaluated. Results: Equilibrium surface tension (EST), elasticity modulus ( E), and relaxation times ( τ) of tear lipids were 22. ±. 2.1. mN/m, 10.7-14.8. mN/m, and 80-150. s, respectively. EST for LCS was 45.3. ±. 0.8 for CC, 40.3. ±. 0.8 for BT, 33.4. ±. 1.0 for PM, and 30.1. ±. 0.8. mN/m for RL. E for LCS varied within 0.5-6.7. mN/m, and τ varied from 49 to 68. ±. 5. s. For mixed lipids. +. LCS films, EST remained unchanged whereas E and τ were reduced for all LCS types. Exposure to PM and RL noticeably altered the shape of lipid-film iso-cycles. These changes persisted after LCS washout. Conclusions: Some components of LCS bind irreversibly to lipid films and make them less viscous and less elastic. These findings suggest the possibility of tear-film destabilization upon LCS exposure. © 2014.