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Noelle I. Rabiah, Charles W Scales, Gerald G. Fuller; Influence of tear-film component integration on contact lens wettability. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3932.
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© ARVO (1962-2015); The Authors (2016-present)
This work aims to elucidate how lysozyme and mucin integration affect the wettability of a Group IV conventional hydrogel contact lens, i.e. etafilcon A, and understand if there is a competition between in vitro uptake and release of these macromolecules.
The drainage of phosphate-buffered saline (PBS) films on clean and fouled lenses (lysozyme, mucin, and lysozyme/mucin) was conducted on a custom interferometry setup, i.e. the Interfacial Dewetting and Drainage Optical Platform (i-DDrOP). The PBS film thickness during the drainage and subsequent dewetting of these films was analyzed with white light interferometry to determine changes in film stability (wettability) on contact lenses before and after deposition. Two-photon microscopy (TPM), spectrophotometry, and interfacial rheology were used to analyze the uptake and release of lysozyme and mucin in etafilcon A.
The driving force for breakup of PBS films on etafilcon A was disjoining pressure and its influence decreased if lysozyme was allowed to integrate into the lens before testing, compared to fresh lenses. This was indicated by a longer film breakup time, which can be attributed to a decreased breakup thickness of the PBS film on lysozyme-integrated lenses (0.16 ± 0.04 μm), compared to fresh lenses (0.42 ± 0.08 μm, p < 0.05). Soaking etafilcon A lenses in a fluorescently-labeled lysozyme solution resulted in significant lysozyme integration into the lens interior, as confirmed by TPM. Release of lysozyme from etafilcon A into fresh PBS over the course of 24h was quantified via spectrophotometry (0.25 ± 0.03 mg/lens). Interfacial rheology experiments revealed that as lysozyme desorbs from lenses in PBS, it renders the PBS-air interface viscoelastic. There was no measurable difference in lysozyme uptake or release profiles due to the presence of mucin.
Lysozyme and mucin integration within etafilcon A contact lenses result in increased wettability and stability of a thin PBS film. Lysozyme integration is somewhat homogenous across the lens surface and penetrates throughout the lens bulk. As lysozyme releases from etafilcon A, it increases the viscoelastic properties of the air-liquid interface. In consideration of these in vitro findings, integration and desorption of lysozyme from etafilcon A in vivo may contribute to tear-film support.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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