Prevalence and associated factors of myopia in children and adolescents in Russia: the Ural Children Eye Study

Background To assess the prevalence of myopia and the distribution of ocular axial length as surrogate for myopic refractive error in school children in a population in Russia. Methods The Ural Children Eye Study, a school--based case-control study, was conducted in Ufa/Bashkortostan/ Russia from 2019 to 2022 and included 4933 children (age: 9.7 +/- 2.6 years; range: 6.2-18.8 years). The parents underwent a detailed interview and the children an ophthalmological and general examination. Results Prevalence of any myopia (=-0.50 dioptres (D)), minor myopia (-0.50 D to -1.0 D), moderate myopia (-1.01 D to -5.99 D) and high myopia (=-6.0D) was 2187/3737 (46.2%; 95% CI 44.8% to 48.6%), 693/4737 (14.6%; 95% CI 13.6% to 15.6%), 1430/4737 (30.2%; 95% CI 28.9% to 31.5%) and 64/4737 (1.4%; 95% CI 1.0% to 1.7%), respectively. In the children aged 17+ years, prevalence of any, minor, moderate and high myopia was 170/259 (65.6%; 95% CI 59.8% to 71.5%), 130/259 (50.2%; 95% CI 44.1% to 56.3%), 28/259 (10.8%; 95% CI 7.0% to 14.6%) and 12/259 (4.6%; 95% CI 2.1% to 7.2%), respectively. After adjusting for corneal refractive power (beta: 0.09) and lens thickness (beta: -0.08), larger myopic refractive error was associated (r2=0.19) with older age (beta: 0.33), female sex (beta: 0.04), higher prevalence of maternal (beta: 0.15) and paternal (beta: 0.12) myopia, more time spent in school, with reading books or playing with the cell phone (beta: 0.05) and less total time spent outdoors (beta: 0.05). Axial length and myopic refractive error increased by 0.12 mm (95% CI 0.11 to 0.13) and -0.18 D (95% CI 0.17 to 0.20), respectively, per year of age. Conclusions In this ethnically mixed urban school children population from Russia, prevalence of any myopia (65.6%) and high myopia (4.6%) in children aged 17+ years was higher than in adult populations in the same region and it was lower than in East Asian school children, with similar associated factors.