Contact lenses and eye closure: comparative analysis using three different methods to induce corneal swelling

To determine if the methods used to induce closed-eye corneal swelling significantly affect the swelling results, we conducted a randomized, double-masked study of 12 experienced daily wearers of rigid lenses using 3 measurement conditions for closed-eye contact lens wear. In addition to the control (no lens) condition, each of five rigid gas-permeable (RGP) lens types and two soft lens types were worn overnight by each subject at different measurement sessions. The overnight swelling response measured by optical pachymetry immediately at waking (8 h closed-eye) for untaped eyes was not significantly different from the swelling measured when the eye had been taped shut overnight and measured 1 h after the subject was awake (9 h closed-eye). The 3 h closed-eye corneal swelling response was significantly lower (p less than 0.0001) than both of the overnight corneal swelling responses. The average corneal swelling response for the lenses used was inversely proportional to the equivalent oxygen percentage (EOP) of the lenses. A high degree of intersubject variability was observed in the corneal swelling response.