To investigate the current prevalence of myopia and the progression of the axial length/corneal radius ratio(AL/CR) among primary school students in Jing'an District, Shanghai, and to analyze the value of dynamic AL/CR monitoring and elucidate its longitudinal association with myopia progression, so as to provide evidences for supporting myopia prevention and control interventions.

From 2019 to 2023, by using a stratified cluster random sampling method, 17 624 students from two primary schools in Jing'an District, Shanghai were selected for annual vision screenings in five consecutive years. Additionally, a retrospective cohort of 480 eligible first-grade students identified in 2019 was followed up until 2023. The analysis focused on the myopia prevalence and the trend in the AL/CR. Differences in screening myopia rates across different student groups from 2019 to 2023 were compared using the Chi-square test. The trends in myopia rates were analyzed using the Chi-square trend test. The Kruskal-Wallis H test was employed to compare AL/CR and its annual increment across groups. A linear mixed-effects model was used to identify factors influencing AL/CR, and a time-dependent Cox regression model was developed to predict the risk of myopia onset.

From 2019 to 2023, the screening myopia rates were 36.65%, 38.31%, 40.47%, 39.56%, and 39.76% for each respective year. Cohort analyses revealed Grade 5 girls had significantly greater AL/CR increments than boys (Z=-2.05, P < 0.05). Linear mixed models identified baseline AL/CR (β=1.051, 95%CI=1.012-1.091), grade level (β=0.040, 95%CI=0.038-0.042), and first-year AL/CR increment (β=0.788, 95%CI=0.733-0.843) as primary determinants (all P < 0.01). Boys showed slower AL/CR progression than girls (β=-0.003, 95%CI=-0.005 to-0.001, P < 0.01). The time-dependent Cox model demonstrated that both baseline AL/CR (Z=3.40) and its time-varying effect (Z=10.41) significantly predicted myopia risk(both P < 0.01). The effect of AL/CR on myopia risk significantly increased with follow-up time, and the growth rate exceeded a linear progression pattern.

AL/CR progression is primarily driven by baseline values and grade advancement, with slower progression in boys. Dynamic AL/CR monitoring outperforms baseline measurements in predicting myopia progression. Students with rapid AL/CR increments require early intervention.