Effect of contact lens surface properties on comfort, tear stability and ocular physiology

Aim: Retrospective analysis of different contact lens wearing groups suggests lens surface lubricity is the main factor influencing contact lens comfort. However, the examined commercially available contact lenses differ in material and design as well as surface properties. Hence this study isolates the contribution of lens surface properties using an ultra-thin coating technology. Methods: Nineteen habitual contact lens wearers (21.6 +/- 1.7 years) wore formofilcon B soft monthly disposable contact lenses with and without coating technology modified surface properties for a month each in a randomised double-masked cross-over study. Objective non-invasive: breakup time (NIKBUT), NIKBUT average and ocular redness (Jenvis grading scale) were evaluated (Keratograph 5M) after 1 week and 1 month of wear. Symptoms were assessed using the Contact Lens Dry Eye Questionnaire (CLDEQ-8); perceived vision quality and subjective lens comfort at insertion, mid-day and end of the day were rated with four Visual Analog Scales. Results: Perceived visual quality (F = 5.049, p = 0.037), contact lens dry eye symptoms (F = 14.408, p = 0.001) and subjective lens comfort (F = 28.447, p < 0.001) were better for coated compared to uncoated lenses. The surface coating postponed the lens dewetting (F = 8.518, p = 0.009) and increased the pre-lens tear film stability (F = 5.626, p = 0.029), but bulbar (F = 0.340, p = 0.567) and limbal (F = 0.110, p = 0.744) redness were similar for both contact lenses. No parameter changed significantly between a weeks' and months' wear (p > 0.05). Lens surface wettability and ocular redness were not correlated to changes in symptoms (p > 0.05). Conclusion: As previously hypothesised, enhancing the physical surface properties of a soft contact lens improves subjectively rated wearer comfort, which, in turn, should result in reduced contact lens discontinuation.