Changes in corneal densitometry after long-term orthokeratology for myopia and short-term discontinuation.

Lianghui Zhao,Jie Li,Xianli Du,Lili Jing,Timo Eppig

doi:10.1371/journal.pone.0263121

Lianghui Zhao, Jie Li + Show 3 more

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https://doi.org/10.1371/journal.pone.0263121

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Abstract

PurposeTo quantify changes in corneal densitometry after long-term orthokeratology treatment in myopic children and to analyze the reversibility one month after discontinuation.MethodsSeventy-four myopic subjects aged 8–16 years, who wore orthokeratology lenses for two years, were divided into relatively steep- (lens movement within 1.0–1.5 mm, thirty-six participants) and flat-fitting groups (lens movement within 1.5–2.0 mm, thirty-eight participants). Based on refractive errors, they were divided into low and moderate myopia groups (thirty-seven participants in each group). Corneal densitometry was performed using Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) at each follow-up timepoint. Repeated-measures analysis of variance was used to compare the parameters before and after orthokeratology.ResultsThe corneal densitometry values over the 0–10 mm diameter area increased from 12.84±1.38 grayscale units (GSU) at baseline to 13.59±1.42 GSU after three-month orthokeratology (P = .001) and reached 14.92±1.45 GSU at two years (P < .001). An increase in densitometry began at one month (P = .001) over the 0–2 mm annulus compared with that at three months over the 2–6 mm and 6–10 mm zones (P = .002,.014). The densitometry values significantly increased at three months in the relatively steep-fitting group (P = .003) and at one year in the relatively flat-fitting group (P = .001). After discontinuation of orthokeratology for one month, the values showed no significant decrease.ConclusionsLong-term orthokeratology treatment causes a small but statistically significant increase in corneal densitometry values. During the first year, the onset of these changes was related to the fitting mode. Corneal densitometry values showed no significant reduction after one-month discontinuation.

Highlights

As orthokeratology has become a valid method to control myopia and has been used worldwide in recent years [1, 2], the safety of the cornea associated with the technique has increasingly become a concern
We speculate that corneal transparency might change after long-term orthokeratology treatment, but the change is too slight to be quantified by slit-lamp microscopy
Histological evidence has shown that these changes are associated with the compression of central basal cells, the elongation of mid-peripheral basal cells, and the increased number of mid-peripheral epithelial cell layers after orthokeratology treatment [9]

Summary

Introduction

As orthokeratology has become a valid method to control myopia and has been used worldwide in recent years [1, 2], the safety of the cornea associated with the technique has increasingly become a concern. Previous studies have found that a brownish pigmented corneal arc can appear after orthokeratology [3–5], which may change the transparency of some areas of the cornea. An important safety index of the cornea, depends on the normal functions of corneal epithelial cells, stromal cells, and endothelial cells and on the regular arrangement of fibers. Histological evidence has shown that these changes are associated with the compression of central basal cells, the elongation of mid-peripheral basal cells, and the increased number of mid-peripheral epithelial cell layers after orthokeratology treatment [9]. The density and morphology of corneal stromal cells have been shown to change after orthokeratology lens wear [10]

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