Coefficient of friction for Acuvue lens found equal to cornea

Researchers reported that the ratio between the friction and normal force of 1-Day Acuvue TruEye was similar to the cornea after a full day of wear.

Tawnya Wilson, OD, FAAO, a principal research optometrist with Johnson & Johnson Vision Care Inc. (JJVCI), told Primary Care Optometry News, “Lubricity is what allows two surfaces, such as the eyelid blinking across a contact lens to slide smoothly against one another. A material’s lubricity is typically described by its coefficient of friction (CoF), or the ratio between the friction and normal force.”

She said that studies have shown the CoF may affect comfort even more than wettability, oxygen permeability or modulus.

JJVCI researchers tested healthy, unpreserved human corneal tissue in a phosphate-buffered tear-like fluid within 3 to 9 hours of donor death and determined that its CoF is 0.015 ±0.009. They compared this to the in vitro CoF on 13 fresh narafilcon A contact lenses and the ex vivo CoF on 10 subjects who wore 1-Day Acuvue TruEye for 10 to 16 hours.

“Not only was the CoF of the fresh-from-the-package lenses statistically equivalent to that of the human corneas we had tested earlier, but it was also statistically unchanged after a full day of wear,” Wilson said. “This research should provide clinicians with confidence that the lubricity of the 1-Day Acuvue TruEye Brand can be maintained throughout the normal wear period.” – by Nancy Hemphill, ELS, FAAO

References:

Brennan NA, et al. Optom Vis Sci. 2009:86;E-abstract 90957.

Roba M, et al. Tribology Letters. 2011;44(3):387-397.

Brennan NA, et al. Contact Lens Ant Eye. 2013;36:S2.

Wilson T, et al. Cornea. 2015;34(9):1179-1185. doi: 10.1097/ICO.0000000000000524.

Tosatti S, et al. Coefficient of friction comparison of worn daily disposable silicone hydrogel contact lenses to human corneal tissue. Poster presented at: European Contact Lens Society of Ophthalmologists. 2015.