To investigate the distribution and influencing factors of the ocular biological parameters related to refractive development in school-age children.

A cross-sectional study was performed.A total of 1 091 children aged 6-12 years old from July, 2017 to August, 2018, resident in downtown of Zhenjiang were enrolled in this study.The corneal radius of curvature (CR) and axial length/corneal radius of curvature ratio (AL/CR) were calculated after AL and corneal curvature (K) were measured by IOL Master.After pupillary dilatation with 0.5% tropicamide, cycloplegic retinoscopy was performed to identify refractive status.According to the spherical equivalent refraction (SER), all right eyes were classified into myopia, hyperopia and emmetropia.The comparison of the above parameters between different genders, as well as among different age groups and different refractive status groups were determined while the relative factors of the biological parameters and refractive status were analyzed by multivariate regression analysis.The study protocol was approved by the Ethics Committee of Affiliated People's Hospital of Jiangsu University (No.K-20190153-W).

There were statistical differences in AL, SER and AL/CR value among different age groups (F=32.34, P<0.01;F=33.69, P<0.01;F=2.19, P=0.04), which showed that refractive status shifted to myopia as well as AL and AL/CR value were increased with age.Compared with the girls, the boys had significantly longer AL, greater CR, greater AL/CR value, and smaller K (t=7.58, P<0.01;t=-7.48, P<0.01;t=-8.08, P<0.01;t=-2.14, P=0.03). There were statistical differences in AL and AL/CR value among different refractive status groups (F=192.68, P<0.01;F=143.15, P<0.01). The myopia group had longer AL and greater AL/CR value than the other two groups.Children whose parents were not myopic and children who had outdoor activities more than 14 hours per week and did homework less than 20 hours per week and children who slept more than 9 hours per day had shorter AL, smaller AL/CR value, and were more inclined to hyperopia or emmetropia.The results of multivariate regression analysis suggested that children aged from 6-12 years old with older age, female, increased height, parental myopia, and more time in homework or less time in outdoor activities per week may be more likely to have myopia, and longer AL or bigger AL/CR value was correlated with older age, male, greater body mass index (BMI), increased height, myopia conditions of parents, more time of doing homework, and less time in outdoor activities.

The SER shifts to myopia with age in 6 to 12-year-old school-age children in the downtown of Zhenjiang.And there are significant differences in AL, CR and AL/CR value between boys and girls.Female, older age, increased height, more time in homework, less time in outdoor activities, and parental myopia are associated with more negative SER.

School-age children; Refractive development; Myopia; Ocular biological parameters; Axial length/corneal radius of curvature ratio