Redistribution of the Corneal Epithelium After Overnight Wear of Orthokeratology Contact Lenses for Myopia Reduction

Background: To investigate changes in the corneal epithelium topographic map in juvenile myopia after overnight wear of orthokeratology lenses (OK). Methods: A total of 53 juveniles (53 right eyes) successfully wore OK and were reviewed in a timely manner from January 2016 to July 2017. Epithelial and corneal data were obtained by optical coherence tomography (OCT). Changes in uncorrected visual acuity, diopter, corneal refractive power, and epithelial and corneal thickness were analyzed before and after 1 day, 1 week, and 1 mo of overnight wear of OK. Results: The corneal epithelium was reshaped after 1 day of OK; the myopia degree was reduced, and uncorrected visual acuity reached 0 logMAR at 1 week. The central (2-mm) average epithelial thickness was 52.04±2.35 μm, 49.25±2.67 μm, 45.91±2.80 μm, and 47.53±3.44 μm before and after 1 day, 1 week, and 1 mo of OK, respectively (t=10.122, 10.782, and 10.673, respectively, P≤0.001). The central epithelium appeared to have a thinning trend, which was obvious at 1 week, when the average thinning of 6.13±1.67 μm accounted for approximately 11.78%±3.21% of the total epithelium thickness. The epithelial thickness of the reverse curve zone was 51.83±2.49 μm, 57.62±3.01 μm, 59.43±3.19 μm, and 60.22±2.75 μm before and after 1 day, 1 week, and 1 mo of OK, respectively, showing a significant increase over time (t=5.325, 6.177, and 6.312, respectively, P≤0.001). Conclusion: In the early stage of OK, the corneal epithelium was redistributed very quickly. The central epithelium became thin, while the epithelium of the reverse curve zone correspondingly thickened and achieved a plateau at 1 mo. Epithelial redistribution guaranteed uncorrected visual acuity after removal of OK.