Corneal refractive therapy with different lens materials, part 2: effect of oxygen transmissibility on corneal shape and optical characteristics

Abstract

Purpose: To compare the effects of two different oxygen transmissible (Dk/t) lenses on corneal shape and optical performance after one night of corneal refractive therapy (CRT(R)) for myopia.

Methods: Twenty myopic subjects were fit with Menicon Z (MZ) (Dk/t = 90.6, Paragon CRT(R) lenses) on one eye and an Equalens II (EII) CRT lens (Dk/t = 47.2) on the contralateral eye (eye randomized). Corneal topography, refractive error and aberrations were measured before lens insertion (baseline), and the following day after overnight lens wear, on lens removal and 1, 3, 6, 12 h later. Root mean square wavefront errors were measured using 4.5 mm pupils.

Results: Averaged over position and time, the horizontal corneal curvature was statistically different between the MZ and EII lens-wearing eyes (p = 0.011). The central cornea flattened similarly (p = 0.886) and the mid-periphery steepened in both eyes (p = 0.061) from baseline. The EII lens-wearing eyes were steeper in the mid-periphery than the MZ eyes immediately after lens removal and at the 1-h visit (p < or = 0.032). Central corneal flattening and mid-peripheral corneal steepening regressed over time (all p < 0.001) but did not recover to baseline by 12 h (all p < 0.004). Myopia was reduced equally by 0.84 +/- 0.83 D for the MZ-lens wearing eyes and 0.84 +/- 0.87 D for the EII eyes (p = 0.969). Coma increased from baseline 1.85X (0.056 +/- 0.081 microm) for the MZ-lens wearing eyes and 1.72X (0.048 +/- 0.084 microm) for the EII eyes (both p < 0.001). Spherical aberration increased from baseline 4.55X (0.101 +/- 0.077 microm) for the MZ-lens wearing eyes and 4.31X (0.085 +/- 0.076 microm) for the EII eyes (both p < 0.001), but there were no differences between the MZ and EII eyes (all p > or = 0.308). Coma and spherical aberration did not return to baseline by 12 h (both p < or = 0.007).

Conclusions: After one night of CRT lens wear, changes in corneal shape were slightly different, with more mid-peripheral steepening in the EII eyes compared to the MZ eyes. Change in central corneal curvature and optical performance were similar in both eyes.