[The incidence of myopia and myopic progression from 2019 to 2020 in school-age children in Zhuozhou]

Objective: To analyze the changes in refractive status and prevalence of myopia in 6-to 14-year-old children at 2 time points in Zhuozhou, Hebei Province. Methods: In the current cohort study, the visual acuity and refractive status of primary and secondary school students aged 6 to 14 years were examined from June to August 2019 and reexamined from June to August 2020. A total of 30 412 subjects with examination data were enrolled, including 15 861 males (52.2%) and 14 551 females (47.8%), with an average age of (10.0±2.7) years. The participants underwent autorefraction without cycloplegia and a naked eye visual acuity test with a standard logarithmic visual acuity chart. Myopia was screened by the standard of equivalent spherical refraction less than -0.75 diopter (D). The categorical data were analyzed by the Chi-square or Fisher's exact test. Clopper-Pearson was used to estimate the 95% confidence intervals for the incidence of myopia. Results: After the 1-year interval, the change of equivalent spherical refraction was(-0.67±1.11) D and(-0.76±1.11) D, respectively, in male and female participants, and their visual acuity decreased by 0.11±0.19 and 0.12±0.21, respectively. There were significant inter-group differences in the annual change of spherical power in different age groups (χ²=276.23, P<0.001). The naked eye visual acuity reduction was greatest in the 10-year-old students. The incidence of myopia was 42.2% (95% confidence intervals of 41.47% to 42.93%) during the 1-year follow-up period. The incidence of myopia was highest at the age of 14 (52.0% in males and 54.2% in females) and lowest at the age of 6 (31.0% in males and 33.1% in females). Conclusions: The 1-year follow-up revealed an obvious myopic shift in the refractive status of school students in Zhuozhou, with their naked eye visual acuity decreased. The incidence of myopia was higher in females than that in males.