Objective analysis of pre-lens tear film stability of daily disposable contact lenses using ring mire projection

Abstract

Purpose: The primary objective of this study was to evaluate the in vivo pre-lens non-invasive drying-up time of two types of daily disposable contact lenses (DDCLs) after 12 hours of wear. Methods: This prospective, randomized, single-center, cross-over pilot study evaluated 31 subjects aged 18–44 years with normal eyes and good tear film stability who were adapted current soft contact lens wearers. Subjects wore nelfilcon A and stenfilcon A DDCLs for 12 hours each on two different days. Non-invasive video keratography drying-up time (NIK-DUT) videos of each eye were recorded 12 hours after lens insertion for about 25 seconds, with a 5-minute tear film recovery time allowed between video recordings of the right and left eyes to avoid bias. Post-blink time required to reach 15% distortion of the projected rings and the speed of break-up at 15 seconds post-blink were measured at each time point and on-eye wettability was determined by ring mire projection under white light illumination. Results: Mean time to reach 15% ring distortion was similar for nelfilcon A (19.25±3.20 sec) and stenfilcon A (20.24±3.02 sec) DDCLs but varied highly among subjects. The mean speed of break-up at 15 sec post-blink was 0.3±0.38% distortion/sec (95% confidence interval [CI] 0.138–0.365% distortion/sec) for nelfilcon A and 0.2±0.23% distortion/sec (95% CI 0.048–0.279% distortion/sec) for stenfilcon A DDCLs. Conclusion: Multifunctional topography allowed the objective evaluation of in vivo pre-lens tear film stability using ring mire projection. This dynamic method was simple, fast and non-invasive, enabling measurements of NIK-DUT and evaluating wettability over a large area, greater than the optical zone of the contact lens surface, for the entire inter-blink interval.