To assess the impact of lens-free intervals of varying lengths on end-of-day comfort with soft contact lenses.
Twenty-five symptomatic lens wearers participated in this randomized, cross-over study involving nine individual 12-hour days: one spectacle (no lens) and eight lens wear days. On each lens wear day, lenses were worn bilaterally in 2-hour intervals, separated by lens-free (recovery) periods of 0, 30, 60, or 80 minutes (repeated throughout the day). For each 2-hour lens wear interval, new lenses were worn. Ocular comfort was rated on a 0 to 100 visual analogue scale (0 = extremely uncomfortable); tear film and ocular parameters were assessed at the beginning and end of each study day. This study involved two different types of silicone hydrogel lenses, and the order of lens type and length of recovery period was randomized. Participants were unaware of the true study purpose and that a new lens pair was used for each lens wear interval.
End-of-day comfort on lens wear days was significantly worse than on the spectacle day (p < 0.002). There was no significant effect of the recovery periods on end-of-day comfort (p > 0.05). Although lens wear affected noninvasive tear film break-up time and conjunctival staining, there were no effects of recovery period length on noninvasive tear film break-up time (p > 0.05), tear meniscus height (p > 0.05), corneal staining (p > 0.05), conjunctival staining (p > 0.05), bulbar conjunctival redness (p > 0.05), or limbal redness (p > 0.05). There was no consistent effect of recovery period length on lid margin staining.
Lens-free recovery periods during a 12-hour lens wear day did not positively impact end-of-day comfort in this study. Cumulative lens wear times ranged from 8 to 12 hours, and the results suggest that once the length of lens wear exceeds the usual comfortable wear time, there is no benefit of short recovery periods.
†PhD, OD, FAAO
‡OD, MS, FAAO
§PhD, FCOptom, FAAO
Centre for Contact Lens Research, School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada (US, NJK, LWJ); and Alcon Laboratories Inc., Johns Creek, Texas (AL).
Ulrike Stahl Centre for Contact Lens Research School of Optometry and Vision Science University of Waterloo 200 University Avenue West Waterloo, ON N2L 3G1 Canada e-mail: firstname.lastname@example.org