The risk factors for ocular biological parameters in Chinese preschool children: a Beijing eye study

Abstract

Background To investigate the genetic and environmental factors associated with axial length (AL), the corneal radius of curvature (CR) and the axial length to corneal radius of curvature (AL/CR) ratio among 3- to 6-year-old children in Beijing, China. Methods This cohort study of kindergarten children in Tongzhou District, Beijing, started in November 2021 and was conducted over three months. A total of 1403 children aged 3–6 years from 9 kindergartens were randomly selected for ocular biological parameter measurements and cycloplegia refraction. Ocular biological parameters, including axial length (AL) and the corneal radius of curvature (CR), were collected before cycloplegia. The spherical equivalent (SE) and AL-to-CR ratio (AL/CR) were calculated. The questionnaire of each child's parental myopia and environmental influence was completed by the children’s parents. Results A total of 1403 participants (733 males, 52.25%) aged 3–6 years (mean 4.36 ± 0.82 years) were included. According to the one-way analysis of variance, longer ALs were associated with male sex, older age, myopic diopter and parental myopia. A greater CR was associated with male sex and more outdoor time. A greater AL/CR ratio was significantly associated with male sex, older age, myopic refractive strength and parental myopia. Multiple regression analysis revealed that a longer AL and a greater AL/CR ratio were significantly associated with male sex, older age, diopter with myopia and parental myopia. CR values were greater in males. In addition, when the time spent outdoors increased, the CR value increased, and the AL/CR ratio decreased. Conclusion Ocular biological parameters are influenced by genetic and environmental factors. A longer AL was associated with older age, male sex and parental myopia among children aged 3–6 years in Beijing, China. Parental myopia and male sex are associated with a greater risk of a higher AL/CR ratio in preschool-aged children. When the time spent outdoors increases, the CR increases, and the AL/CR decreases.