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Ulrike Stahl, Nancy Keir, Jalaiah Varikooty, Krithika Nandakumar, Adam Keech, Alan Landers, Lyndon Jones; The effect of recovery periods on end of day comfort. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5462.
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Previous studies indicate that single lens replacements or time of day do not influence end of day (EOD) contact lens comfort, suggesting that length of wear may be a driving factor in ocular comfort. This study investigated the impact of lens-free intervals of varying lengths on EOD comfort.
25 symptomatic lens wearers (comfortable wear time 6.3±1.6hrs) participated in this randomised, cross-over study involving nine individual 12-hour days: 1 lens-free (spectacle wearing) assessment day and 8 lens wear days. On each lens wear day, lenses were worn bilaterally in 2-hour intervals, separated by lens-free (recovery) intervals of 0, 30, 60 or 80 minutes (repeated throughout the day). For each 2-hour lens wear interval, a new pair of lenses was worn. Ocular comfort was rated before and after the first lens insertion, and after each 2-hour lens interval, using a 0-100 visual analogue scale (0= extremely uncomfortable and 100 = very comfortable). This study involved 2 different types of silicone hydrogel lenses, and the order of lens type and length of recovery period was randomised. Participants were unaware of the true study purpose and that a new lens pair was used for each lens wear interval.
A continuous decrease in comfort with wearing time was observed on all lens wear days, independent of recovery periods or lens type. There were no differences in EOD comfort scores between lens wear days for lens 1 (Mean range 48.9±17.8 to 56.0±19.8, p>0.42) or lens 2 (Mean range 53.7±15.9 to 58.8±13.9, p>0.9), and ratings were significantly lower compared to the lens-free assessment day (70.8±16.2) (p<0.001). The average drop in EOD comfort from lens insertion ranged between 14.2 to 26.0 and 14.4 to 19.8 (lens 1 and 2, respectively), and was independent of the recovery period lengths.
The introduction of lens free recovery periods during a 12-hour lens wear day did not positively affect EOD comfort in this study. The accumulative lens wear time in this study ranged from 8-12 hours, and may suggest that once lens wear exceeds the usual comfortable wear time, participants will not benefit from short recovery periods.
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