Education and myopia prevalence in children from kindergarten to primary school: an exploratory mediation analysis from the Hong Kong children eye study

PURPOSE: To assess the role of education on myopia prevalence and refractive status in children enrolled in kindergarten and the early grades of primary school. METHODS: In this population-based, cross-sectional study, children from primary schools and kindergartens were recruited prior to the onset of the COVID-19 pandemic in January 2020. Cycloplegic autorefraction and axial length (AL) were measured in all children. Data on parental myopia, family income and children's lifestyle factors were collected via a standard questionnaire. Mediation analyses were used to explore the influence of education on myopia prevalence, spherical equivalent (SE) and AL. RESULTS: In 2525 kindergarten children (413 in grade 2 /(K2) and 2112 in grade 3 (K3)) and 9018 primary school children (4250 in grade 1 (P1) and 4768 in grade 2 (P2)), myopia prevalence increased with academic grade: 7.6% of K2, 8.7% K3, 17.3% P1 and 29.1% P2. AL was longer in K3 than in K2 children (p<0.001) although SE did not differ (p=0.18). Exploratory analyses suggested statistical mediation by education duration in the association between age and myopia-related outcomes. Among kindergarten children, parental myopia was the sole factor associated with myopia prevalence, SE and AL. For primary school children, schooling duration in P1, age, sex, family income and parental myopia were associated with myopia prevalence, SE and AL. CONCLUSION: The prevalence of myopia significantly increased from kindergarten to primary school with education duration being a possible mediator from primary school onward. Notably, significant changes in AL were observed among kindergarten children.