In vitro contact angle and coefficient of friction profiles for daily disposable contact lenses

Abstract

Abstract Purpose To profile coefficient of friction (COF) and contact angle (CA) performance of popular daily disposable contact lenses many of which contain comfort additives. COF indicates the level of friction that may be experienced between a contact lens and ocular surfaces (corneal epithelium and palpebral conjunctiva). Small CA values indicate a more wettable lens surface. Methods CA's and static and dynamic COF's were measured on commercially available nelfilcon A with PVA (NA); nelfilcon A with HPMC, PEG and PVA (NB); etafilcon A with added povidone (E); hilafilcon B (H); and omafilcon A (O) contact lenses. Lenses were removed from the original packages and measured for out of package (TO) or rinsed in PBS for 1 hour (T1) or 4 hours (T4) and measured. Unpaired t‐tests with alpha <0.05 were used to compare between and within lenses and report statistically significant differences. Results At TO, the CA's averaged NA (9.6), NB (11.4), E (39.6), H (11.2), and O (44.6). After rinsing the NA and NB lenses maintained the lowest CA's. The highest CA was with E at T4 (78.2). At TO, the lowest static and kinetuc COF's were measured on NA (0.006 and 0.027 respectively) while the highest static and kinetic COF's were measured on O (0.831 and 1.114). After rinsing, static COF's were statistically unchanged for NB and O (which contains no comfort additives) and all others increased at T1 and T4 from their T0 values. Conclusion The contact angle and friction performance of daily disposable contact lenses was found to vary widely. Nelfilcon A with PVA were the most wettable as indicated by having the lowest CA. Nelfilcon A with PVA, PEG and HPMC showed low static and kinetic COF's that remained stable with rinsing. Commercial interest