Lens-care-solution-induced alterations in dynamic interfacial properties of human tear-lipid films

Abstract

a b s t r a c tPurpose: 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 expansioncompression cycles for dynamic interfacial properties and to step-strain relaxations for assessments of rheological properties.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 ( ) 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 varied from 49 to 68 ± 5 s. For mixed lipids + LCS films, EST remained unchanged whereas E and 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.

Dynamic interfacial properties of human tear-lipid films and their interactions with model-tear proteins in vitro

“…and (B), causes thickening in the aqueous layer, with a corresponding bright streak between the arrows, in the fluorescence image in (B). Healthy tear film, 25-year-old white male [26] ©The American Academy of Optometry 2013.…”

“…In a recent review [23], the Marangoni effect, mentioned above as one of the possible tear-lipids functions, was criticized and practically dismissed as an important factor based on the premise that an aqueous-air interface has to be exposed and the tear-lipid film has to be broken in order for the Marangony flow to take place. The results of our studies of tear-lipids dynamic interfacial properties suggest [24][25][26] that Marangony flows do take place at the interface between air and lipid film due to surface-pressure gradients arising when lipid films are irregularly stretched or compressed during blink. The surface-pressure gradients between thick and thin lipid-film areas cause the Marangony flows in tear-lipid films and consequently, the viscous drag between lipid film and tear aqueous, which in turn creates flows in tear-aqueous fluid.…”

TFOS DEWS II Tear Film Report

“…However, both meibum and contact lens lipid extracts are sensitive to the presence of (glyco)proteins (lactoferrin, lysozyme, mucin, lipocalin, serum albumins, lactoglobulin, lactoferrin, secretory IgA, keratin, lung surfactant proteins) [297–300,307,314] and pharmaceutical agents (hyaluronic acid, benzalkonium chloride, SofZia, Polyquad, whole eye drops and lens care solutions) [305,315–317] in the film subphase. However, even in sub-physiologically “diluted” (5–10 mN/m vs. ~30 mN/m) meibum films, the kinetics of the penetration of such substances is much slower (>1 h) than the physiological time scale [297–300].…”

“…This is a rapid interaction that immediately alters the structure and dynamic interfacial properties of the layers [287,305,311]. These data, along with studies evaluating the impact of lipid (or lipophilic) inclusions directly into meibum layers, demonstrate that non-surface active or lipophilic substances are well tolerated by tear lipid films [318–322], while polar surface active ingredients can disrupt the film’s structural integrity and surface properties [314–317]. Interactions between the tear film lipid layer and pharmaceutical agents are of particular pharmacokinetic importance as they may impart long term effects at the ocular surface, in light of the much slower in vivo turnover rate of the tear film lipid layer compared to the mucoaqueous layer (0.93 ± 0.36%/min vs. 10.3 ± 3.7%/min respectively) [323].…”

Accounting for Ethnicity-Related Differences in Ocular Surface Integrity as a Step Toward Understanding Contact Lens Discomfort

“…68 The biophysical properties of tear lipids, such as dynamic interfacial behavior, elasticity, and viscosity, are crucial factors controlling tear film stability. 54,62,70,71 These properties are likely to be closely linked and strongly dependent on tear lipid composition. Evidence for dissimilarities in the biophysical properties between Asian and white tear lipid film emerged during investigations of the dynamic properties of the human tear lipid film.…”