Efficacy of Myopia Control and Distribution of Corneal Epithelial Thickness in Children Treated with Orthokeratology Assessed Using Optical Coherence Tomography

Abstract

The association between myopia control efficacy in children treated with orthokeratology and corneal epithelial thickness is still unknown. The aim of this study was to explore the corneal epithelial thickness and its association with axial length changes in children treated with orthokeratology. This retrospective cohort study enrolled children aged from 9 to 15 years who had received orthokeratology for myopia control and had been followed up for at least 1 year. Anterior segment optical coherence tomography was performed to generate wide epithelial thickness maps of the patients. Annual axial length changes were calculated from the axial length at 6 months after the initiation of orthokeratology lens wear and at final measurements. Corneal epithelial thickness data were obtained from 24 sectors and a central 2 mm zone of the wide epithelial thickness map. Associations between annual axial length changes and corneal epithelial thickness for each sector/zone of the wide epithelial thickness map, and orthokeratology treatment data were determined by generalized estimating equations. Finally, a total of 83 eyes of 43 patients (mean age 11.2 years) were included in the analysis. The mean annual axial length change was 0.169 mm; when regressing demographic and ortho-k parameters to mean annual axial length changes, age and target power were both negatively associated with them (β = −14.43, p = 0.008; β = −0.26, p = 0.008, respectively). After adjusting for age and target power, the annual axial length changes were positively associated with the corneal epithelium thickness of IT1, I1, SN2, and S2 sectors of the wide epithelial thickness map, and negatively with that of the I3 sector. In conclusion, we identified associations between annual axial length changes and the corneal epithelium thickness of certain sectors in children treated with orthokeratology. This may facilitate the design of orthokeratology lenses with enhanced efficacy for myopia control.

Short-term Changes in Epithelial and Optical Redistribution Induced by Different Orthokeratology Designs

“…In previous studies, the treatment zone moved from central to inferotemporal, and the epithelia of 2 to 5 mm, inferior temporal zones were thinner. 9,14 This asymmetric epithelial thinning and thickening may be related to the lens with slight inferotemporal decentration. The ortho-k lens decentring toward the inferotemporal quadrant of the cornea was commonly reported by corneal topography.…”

“…1–8 Ortho-k can reduce axial elongation by approximately 50% over 2 years. 3 The treatment-zone size and decentration, 7,8 corneal power shift 5,6 and epithelial thickness of certain sectors 9 caused by ortho-k lenses have been associated with axial length growth. Some studies have found that different lens designs can result in various peripheral refractions, 10 corneal optical modifications, 11,12 and myopia progress control.…”

Biomechanical study of cornea response under orthokeratology lens therapy: A finite element analysis

“…As numerous recent clinical studies have found that OK lenses with small optical zone diameters produce smaller treatment zones with steeper aspheric changes of the cornea, which may be beneficial for myopia control. 15,[38][39][40] However, these researches are limited to the variation in optical zone diameter of the OK lens. Therefore, in the future, we will do a comprehensive parametric study on BC (e.g., diameter width, e-value, etc.…”

“…13,14 Studies on the application of ophthalmic instruments such as corneal topography and OCT have found that after orthokeratology, the central cornea flattens and decreases in thickness, and the mid-periphery steepens and increases in thickness. 15 However, most studies were limited to analyzing the alteration of corneal geometry after orthokeratology. Few researchers have delved into the detailed investigation of the spatial displacement and stress distribution of the cornea under the OK lens combined with the OK lens's theoretical design parameters.…”

“…Previous studies had claimed that OK lenses act on the corneal surface mainly by the mechanical pressure of the eyelids and the hydraulic pressure of tears 13,14 . Studies on the application of ophthalmic instruments such as corneal topography and OCT have found that after orthokeratology, the central cornea flattens and decreases in thickness, and the mid‐periphery steepens and increases in thickness 15 . However, most studies were limited to analyzing the alteration of corneal geometry after orthokeratology.…”