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

Abstract

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.

A new approach for quantifying epithelial and stromal thickness changes after orthokeratology contact lens wear

“…These results are consistent with earlier reports in which the central epithelial thickness decreased over 30 days of lens wear by 15.8 ± 3.3 µm in 18 eyes [12], and by up to 18 µm in one eye [32]. Other studies reported epithelium thickness reduction after one week of lens wear of 10.6 ± 4.2 µm [10], and 6.1 ± 1.6 µm [15]. Others adopted a one-day follow up and reported epithelial thickness reductions of 4.6 ± 2.7 µm [10], and 8.7 ± 4.8 µm [12].…”

“…The thickness increases in the paracentral area could be due to the deformation of epithelial cells caused by the negative pressure exerted by the Ortho-K lens in the reverse curve zone [23,33], and remodelling of the epithelium due to interference by the contact pressure with the normal centripetal migration of epithelial cells from the limbus could be another reason. The paracentral thickness increases observed in our study are compatible with the mean values reported by Zhang et al [15], in which epithelial thickness increases were noted in both the paracentral and peripheral areas, albeit the change did not reach statistical significance. However, Zhang also mentioned that the lack of significance of changes in the paracentral area may have been due to variations in the size and location of reshaping areas among individuals.…”

“…[23] measured the epithelial thickness in 27 subjects before and one month after wearing Ortho-K lenses, and showed significant epithelial thickness reductions in the central cornea up to 2 mm diameter. Similar observations, and also epithelial thickening in the peripheral region, were made based on analysis of OCT corneal scans [11,15,16,24].…”

“…[11] has explained, these differences may be due to variations in the eyelid pressure acting in different eye regions. They could also be due to different lens-on-eye decentrations among individuals [15].…”

Corneal thickness changes in myopic children during and after short‐term orthokeratology lens wear

“…Anterior segment OCT has been used to investigate corneal changes after ortho‐k lens wear in children 12–14 . These studies confirmed that ortho‐k lens wear induces central corneal thinning, but conflicting results were found for peripheral corneal changes.…”