Abstract
Purpose: :
To study the impact of soft contact lens (SCL) surface wettability on subjective comfort ratings and tear-film stability.
Methods: :
The contact angles (CA) were evaluated in dynamic-cycling regime by modified captive-bubble technique with concurrent surface tension measurements. Healthy, asymptomatic and seasoned SCL wearers were recruited for randomized, double-masked, contra-lateral studies with cross-over. 17 wore Accuvue2 (AV2) lenses for 30 min., one from blister (pristine), the other pre-soaked in OptiFree (OF) solution for a week. 16 were dispensed with one Focus N&D (FND) and one Purevision (PV) lenses. Pre-lens NIBUT (PL-NIBUT), comfort, preferences, in vivo wettability were evaluated after 15 min. wear for all lenses; repeated measurements were taken after 2-week wear for SiH lenses. Ex vivo CA and surface tension were simultaneously measured on each lens pair at the same time. Collected AV2 lenses were analyzed for protein-uptake using BCA colorimetric assay.
Results: :
In vitro CA for AV2 pristine and pre-soaked lenses were 10.9o±3.1o and 83.7o±4.5o, respectively. Ex vivo aqueous adhesion energy (Eadh) was similar for pristine and OF-soaked lenses, 38.4±3.2 mN/m and 39.5±3.5 mN/m, respectively. Ex vivo CA for pristine lenses remained low (12.8o±8.8o),whereas CA of pre-soaked lenses decreased significantly (27.1o ± 10.1o). NIBUT was reduced to 30 ± 3% of pre-corneal for both AV2 lenses. In vivo wettability was equal for pristine and pre-soaked lenses. Total protein uptake was not significantly different for pristine lenses and pre-soaked lenses (32.1± 10.8 µg/lens vs. 38.2 ± 8.2 µg/lens; p > 0.05). For FND and PV lenses the initial in vitro CA were 41.2o±4.4o and 74.4o±9.3o, and Eadh 47.8±3.2 mN/m and 8.1±5.3 mN/m, respectively. Ex vivo CA were 56o±3.4o and 76o±10o and Eadh were 34±10 mN/m and 10.4±11.2 mN/m for FND and PV, respectively. Pre-lens NIBUT was reduced to 21±1.7 % of pre-corneal NIBUT for FND and to 30 ± 2 % for PV . Comfort ratings were 86.8±12.2 and 82.9±10.9 for FND and PV, respectively (P>0.05).
Conclusions: :
Wettability of AV2 lenses was equalized by protein-uptake within first 15 min. of lens-wear. No significant differences were detected in clinical performance for all lenses. No significant preference toward any of the lenses was expressed by the subjects. No correlation was found between comfort ratings and in vitro, in vivo, and ex vivo wettability.
Keywords: contact lens • quality of life • cornea: tears/tear film/dry eye