In the evening before the sleepover, baseline corneal thickness measurements across the horizontal meridian were recorded. The CRTH lenses were inserted, and the fit was assessed for adequate movement, centration, and fluorescein pattern before sleep. Participants slept at the CCLR, retiring at 10 PM and waking at 7 AM the next morning. On waking, the subjects kept their eyes closed until the lenses were removed. In study 1, the thickness of each eye was measured immediately after lens removal and repeated 1, 3, 6, and 12 hours thereafter. An additional set of readings was obtained the next day (28 hours after initial lens removal) to monitor recovery. In study 2, an additional measurement was added at 20 minutes and then repeated at 1, 2, and 3 hours after lens removal.