Abstract
Purpose:
To evaluate the effect of lens wear on coefficient of friction (CoF) as compared to unworn daily disposable contact lenses.
Methods:
Five subjects bilaterally wore nesofilcon A, delefilcon A, nelfilcon A, narafilcon A, etafilcon A, and omafilcon A daily disposable contact lenses in a random order for 4 hours each. CoF measurements were obtained via TA Instruments DHR3 stress rheometer. Lenses were immersed in BBS, conformed around a 6 mm diameter polished stainless steel ring-shaped rub tool, and allowed to relax until the axial force stabilized at a contact pressure of ~ 2 kPa, similar to eyelid pressure.
Results:
For unworn lenses, the mean (SD) static CoF was 0.04 (0.02) for nesofilcon A, 0.63 (0.12) for delefilcon A, 1.44 (0.40) for nelfilcon A, 0.03 (0.00) for narafilcon A, 0.06 (0.01) for etafilcon A, and 0.16 (0.06) for omafilcon A. For worn lenses, the mean (SD) static CoF was 0.14 (0.07) for nesofilcon A, 0.91 (0.21) for delefilcon A, 1.56 (0.67) for nelfilcon A, 0.12 (0.08) for narafilcon A, 0.31 (0.09) for etafilcon A, and 0.64 (0.11) for omafilcon A. For unworn lenses, the mean (SD) kinetic CoF was 0.05 (0.02) for nesofilcon A, 0.12 (0.02) for delefilcon A, 0.58 (0.14) for nelfilcon A, 0.05 (0.00) for narafilcon A, 0.07 (0.01) for etafilcon A, and 0.06 (0.01) for omafilcon A. For worn lenses, the mean (SD) kinetic CoF was 0.06 (0.02) for nesofilcon A, 0.13 (0.02) for delefilcon A, 0.47 (0.12) for nelfilcon A, 0.07 (0.02) for narafilcon A, 0.40 (0.19) for etafilcon A, and 0.10 (0.02) for omafilcon A.
Conclusions:
Both static and low speed kinetic friction showed variability among different daily disposable lens materials for both worn and unworn lenses. nesofilcon A and narafilcon A had the lowest static and kinetic CoF measurements for both worn and unworn lenses, while nelfilcon A had the highest static and kinetic CoF values for both worn and unworn lenses.