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Peter Maziarz, III, X. Michael Liu, Charles P. Lusignan, Mohinder M. Merchea; Differential Surface Friction Analysis of Silicone Hydrogel Contact Lenses Treated with Block Co-Polymer Multi-Purpose Solutions. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6122.
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© ARVO (1962-2015); The Authors (2016-present)
To understand whether the immersion of silicone hydrogel (SiHy) contact lenses in multipurpose solutions (MPS) using different block co-polymer surfactants impacts lubricity, expressed as the kinetic coefficient of friction (CoF). CoF is a system property that may be an important factor related to in-vivo comfort. It may be influenced by the MPS used, as well as, the lens properties (e.g. surface roughness, surface energetics, and rheology).
Two commercially available multipurpose solutions, MPS A (renu fresh™) or MPS B (PureMoist™) and two SiHy lenses, lotrafilcon B (AirOptix Aqua), and senofilcon A (Acuvue Oasys) were studied. SiHy contact lenses were removed from the blisters, rinsed, and soaked in a large excess of stirred Borate Buffered Saline (BBS) overnight to remove the packaging solution. Subsequently, lenses were equilibrated in MPS A or MPS B for 24 hrs. CoF was characterized with a CSM Nanoscratch Tribometer equipped with a custom-built lens holder. The samples were oriented apex-down in 0.75ml of MPS spread over a Kapton® substrate. CoF was measured under a 30 mN normal load at a speed of 5 mm/min. Multiple data points (n=5), using samples of each lens, were analyzed to determine a mean value and standard deviation.
CoF was calculated as the ratio of the lateral force (pull) to the normal force (weight) applied to move the lens relative to the Kapton® at a constant speed. Kinetic friction (motion at constant speed) is different than static friction (incipient motion) and we report only kinetic friction values. The mean (± 1SD) CoF of lotratfilcon A with MPS A and MPS B respectively were 0.06 ± 0.01 and 0.05 ± 0.02. The mean (± 1SD) CoF of senofilcon A with MPS A and MPS B respectively were 0.04 ± 0.03 and 0.03 ± 0.02. There was no statistically significant difference in CoF between MPS A and MPS B for either lotrafilcon A (t-test, p≥0.15) or senofilcon A (t-test, p≥0.57).
Although the MPS are formulated with different block copolymer surfactants for improved wettability and lubricity, this study demonstrated that no statistically significant difference (P>0.15) was observed in lubricity between SiHy lenses treated in MPS A or MPS B, under the applied experimental conditions. Further study is warranted to understand the impact of specific surfactants in MPS formulations on in-vivo SiHy lens comfort.
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