Patients with 30-day extended-wear/continuous-wear (EW/CW) contacts should replace their lenses in the morning rather than at bedtime to reduce their risk for ocular adverse events, according to a study in the December issue of Optometry and Vision Science.

The study evaluated 215 patients who wore silicone hydrogel EW/CW lenses. Each day, the patients inserted fresh lenses either at night before going to bed or in the morning after waking. The researchers compared the rate of ocular adverse events between patients who replaced their lenses at night or in the morning vs. a previously studied group of patients who wore the lenses continuously for a month.  

Results showed that just 4% of patients who replaced their lenses each morning experienced ocular adverse events, such as infiltrative keratitis or corneal erosion.

By contrast, 8% of patients who replaced their lenses each night and 9% of those who wore their lenses continuously for a month experienced ocular adverse events.

These results indicated that regular nighttime lens replacement did not appear to have any beneficial effect compared to continuous monthly wear—possibly due to handling the lenses, and thus contaminating them, just prior to overnight eye closure.

Further, the study researchers suggested that when users replace EW/CW lenses, they should do so in the morning to limit the risk or ocular adverse events.

Ozkan J, Willcox MD, de la Jara PL, et al. The effect of daily lens replacement during overnight wear on ocular adverse events. Optom Vis Sci. 2012 Dec;89(12):1674-81.