This study hypothesized that a traditional high-water contact lens of moderate oxygen transmissibility (Dk/t) is noninferior to common silicone hydrogel (SH) lenses worn for daily wear with respect to measures of hypoxic stress.
Thirty-six habitual contact lens wearers completed wear of three lens types worn in a randomized order: etafilcon A (ACUVUE 2, control), lotrafilcon B (Air Optix Aqua), and comfilcon A (Biofinity). Central corneal thickness (CT) and limbal hyperemia were measured >2 hr after waking and after 6 to 8 hr of wear on days 1 and 7. Endothelial bleb formation was measured on day 1 of each lens type. Noninferiority of etafilcon A, with respect to the other two lens types, was assumed if the following difference margins of equivalence were met: <1.5% for corneal swelling, <0.5 grade for limbal hyperemia, and <1% area of endothelial blebs. Outcomes were modeled using generalized linear mixed modeling techniques.
All lenses showed reductions in least-square mean estimates of CT on both days: etafilcon A −0.26% at day 1 and −0.31% at day 7; lotrafilcon B −1.11% at day 1 and −1.06% at day 7; comfilcon A −0.63% at day 1 and −0.84% at day 7. The difference in mean swelling between etafilcon A and lotrafilcon B was 0.85% at day 1 (95% confidence interval [0.4%–1.3%]) and 0.75% at day 7 (0.3%–1.2%). The difference in mean swelling between etafilcon A and comfilcon A was 0.37% at day 1 (−0.1% to 0.8%) and 0.53% at day 7 (0.1%–1.0%). For limbal redness, etafilcon A fell within 0.1 grade of lotrafilcon B and 0.18 grade of comfilcon A. For endothelial bleb formation, etafilcon A fell within 0.45% of lotrafilcon B and 0.23% of comfilcon A.
The etafilcon A control lens resulted in corneal deswelling throughout the day as did the SH lens types. Limbal hyperemia and endothelial bleb formation with all lenses were negligible, and noninferiority assumptions were met between the lens types for all outcomes. Equivalence of etafilcon A with respect to the two SH lenses for three measures of hypoxic stress was demonstrated.