PURPOSE. To investigate short-term corneal changes induced by reverse geometry lenses worn for orthokeratology (OK), and to monitor recovery of the cornea following lens wear. METHOD. Nine young adult subjects wore reverse geometry rigid gas-permeable lenses (BE; Capricornia Contact Lenses, Brisbane, Australia) in one eye only for 10, 30 and 60 minutes with eyes open, and for 8 hours with eyes closed. The fellow eye acted as a non-lens-wearing control. Corneal topographic changes were monitored using the Medmont E-300 corneal topographer. Changes in uncorrected logMAR visual acuity were also recorded. Data were analyzed by ANOVA and post hoc t-tests.
RESULTS. Significant central corneal flattening (-0.61 +/- 0.35D; p=0.014), and the formation of a defined "treatment zone" (diameter 3.86 +/- 0.27mm), were found after 10 minutes of open-eye lens wear, and progressed with increasing periods of lens wear. Significant improvement in unaided logMAR visual acuity (-0.16 +/- 0.18; p=0.005) was also apparent after the 10-minute lens-wearing session, and showed further improvement with longer periods of lens wear. The recovery of all variables to baseline followed a non-linear course. The cornea recovered within 24 hours after 10, 30 and 60 minutes of OK lens wear, but recovery after 8 hours of OK lens wear occurred only after 48 hours in six subjects and 72 hours in the remaining three subjects.
CONCLUSIONS. The cornea responds rapidly to the application of reverse geometry lenses for OK, with significant central corneal flattening and improvement in visual acuity after just 10 minutes of lens wear. This suggests that the corneal epithelium is able to be molded or redistributed very rapidly in response to the tear film forces generated behind reverse geometry lenses. Our results also support the existing belief that changes in the cornea induced by OK are reversible.