Analysis of the Influence of Corneal Parameters on the Pattern of Myopia Progression when Using Orthokeratology Lenses in Children

Abstract

The progressive course of myopia is one of the most important medical and social problems worldwide. In Ukraine, the relative incidence of moderate myopia ranges from 8.9 to 30.8 % in schoolchildren and in final-year students, mild and moderate myopia is found, according to various data, in 30-68 % of individuals. Some researchers have tried to determine the shape of the cornea and its relationship to the eye size in myopia, but conflicting data have been obtained, so the issue needs further investigation. The aim. To analyze the effect of corneal eccentricity (Ex) in children with myopia on the increase of the axial length of the eye when using orthokeratology lenses (OKL). Methods. The study involved 60 children (117 eyes) aged 7 to 15 years with uncomplicated mild and moderate myopia from –0.75 to –5.0 diopters by spherical equivalent. Biometry was performed using an ultrasound scanner before the start of refractive therapy or prescription of glasses and then every 6 months of observation. Corneal topography was also performed with determination of keratometry and Ex in flat and steep meridians (Oculus Easygraph topographer, Germany). MoonLens OKL with combined design were selected for all the subjects. Results. In patients with mild myopia, there was direct strong correlation between the value of Ex, both in a flat and in a steep meridian, and the axial length at the beginning of the therapy which equaled to 0.28 (p = 0.011) There was also a strong direct relationship between the value of the initial Ex and the difference in refraction (ΔR) after 24 months of observation which equaled to 0.32 (p = 0.001). Assessment of the correlation between the initial value of keratometry and the axial length revealed negative correlation between –0.69 in the group with mild myopia (p<0.001) and –0.67 in children with moderate myopia (p<0.001). There was no correlation of the effect of Ex on the annual gradient of myopia progression in the study. Conclusions. There is no correlation between the baseline Ex and the annual gradient of myopia progression on the background of the use of OKL because the corneal profile changes and there are other factors influencing the pattern of the axial length change. A direct correlation between the baseline Ex and the annual changes in refraction (ΔR) was revealed.