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P.B. Morgan, N. Efron, I.D. Cameron, N.A. Brennan, M. Goodwin; Oxygen Permeability of Silicone Hydrogel Contact Lens Materials . Invest. Ophthalmol. Vis. Sci. 2006;47(13):114.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the oxygen permeability (Dk) of currently–available silicone hydrogel contact lens materials.
Permeability was measured in a randomized and masked manner for the following silicone hydrogel contact lens materials: Acuvue Advance, Acuvue Oasys, Focus Night & Day, O2 Optix and PureVision. Two conventional hydrogel lens materials, Etafilcon A and pHEMA, were measured as controls. We used an extended version of the polarographic measurement method described in ISO 9913–1. Stacks of 1–6 –1.00DS contact lenses were evaluated, with each stack measured twice. The resulting value for t/Dk (derived from electrode current and mathematically correcting for the edge effect) was plotted against t for each stack, with Dk calculated as the inverse of the gradient of this relationship; this latter method corrects for the boundary effect.
Measured permeability values (+/– 95% CI), and manufacturer–claimed values in parentheses, were: Acuvue Advance 59.2 +/– 5.7 (60), Acuvue Oasys 107.4 +/– 7.4 (103), Focus Night & Day 162.0 +/– 9.8 (140), O2 Optix 80.5 +/– 4.9 (110), PureVision 75.9 +/– 6.6 (99), Etafilcon 21.0 +/– 1.0 (21) and pHEMA 8.2 +/– 0.7 (7.5).
With the exception of O2 Optix and PureVision, our values were broadly similar to manufacturer–claimed values. It is unclear whether some manufacturers have accounted for edge and/or boundary effects, and some manufacturers may have used a different measurement methodology (coulometric); these factors may account for discrepancies between our data and that of manufacturers. Our extended ISO methodology has generated data points with small 95% confidence intervals, suggesting that the use of the polarographic method of oxygen permeability measurement can be successfully employed with hyper–permeable contact lens materials.
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