Abstract
Orthokeratology has been widely used to control myopia, but the mechanism is still unknown. To further investigate the underlying mechanism of corneal reshaping using orthokeratology lenses via the finite element method, numerical models with different corneal curvatures, corneal thicknesses, and myopia reduction degrees had been developed and validated to simulate the corneal response and quantify the changes in maximum stress in the central and peripheral corneal areas during orthokeratology. The influence of the factors on corneal response had been analyzed by using median quantile regression. A partial eta squared value in analysis of variance models was established to compare the effect size of these factors. The results showed central and peripheral corneal stress responses changed significantly with increased myopia reduction, corneal curvature, and corneal thickness. The target myopia reduction had the greatest effect on the central corneal stress value (partial eta square = 0.9382), followed by corneal curvature (partial eta square = 0.5650) and corneal thickness (partial eta square = 0.1975). The corneal curvature had the greatest effect on the peripheral corneal stress value (partial eta square = 0.5220), followed by myopia reduction (partial eta square = 0.2375) and corneal thickness (partial eta square = 0.1972). In summary, the biomechanical response of the cornea varies significantly with the change in corneal conditions and lens designs. Therefore, the orthokeratology lens design and the lens fitting process should be taken into consideration in clinical practice, especially for patients with high myopia and steep corneas.
Highlights
As one of the most effective methods of myopia control, orthokeratology has been widely used around the world in the past two decades (Wolffsohn et al, 2016; Cho and Tan, 2019; Jonas et al, 2021)
The central corneal stress and the peripheral corneal stress were regarded as continuous variables, while myopia, corneal curvature, and corneal thickness were regarded as categorical variables
It can be found that the maximum von Mises stress of the corneal central area showed an upward trend with the increase of myopia reduction degree, corneal curvature, and corneal
Summary
As one of the most effective methods of myopia control, orthokeratology (ortho-k) has been widely used around the world in the past two decades (Wolffsohn et al, 2016; Cho and Tan, 2019; Jonas et al, 2021). The strong effect on myopia control of ortho-k lens for children and adolescents has been proved and reported by numerous clinical researchers. The effectiveness in reducing myopia and controlling myopia progression of ortho-k lens has been proven by statistical data, the results vary for the individual subjects (Cho et al, 2005). The mechanism by which it controls the development of myopia, the influences, and the weight of these influencing factors are still unknown, while the clinical application of the ortho-k lens has been reported extensively
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