Refractive error prevalence in urban Vietnamese children: a 2021 to 2024 school health analysis

Background. Refractive error is a leading cause of childhood visual impairment worldwide, yet longitudinal, multi-city data from Vietnam remain scarce, especially for children younger than school age. We aimed to describe the prevalence and secular trends of refractive error in a large urban Vietnamese school health program. Methods. We conducted a retrospective analysis of repeated cross-sectional school health screening data collected from 2021 to 2024 across three major Vietnamese cities (Hanoi, Ho Chi Minh City, and Hai Phong), among children aged 3 to 18 years. The dataset included 141,339 examinations, with a Hanoi sub-cohort of 19,788 examinations that had quantitative autorefractor measurements. We estimated crude prevalence and adjusted prevalence ratios using Poisson regression. Results. The prevalence of any refractive error stayed high throughout the study period, ranging from 53.9% to 57.1% (P for trend < 0.001), and was higher in Hai Phong (68.4%) and Hanoi (61.6%) than Ho Chi Minh City (35.9%), higher in girls than boys (58.5% vs 53.1%), and higher with older age (P < 0.001). In the Hanoi sub-cohort, confirmed myopia prevalence nearly tripled, from 3.7% in 2022 to 11.0% in 2024 (P < 0.001), while hyperopia declined. Conclusions. Refractive error is highly prevalent among urban Vietnamese schoolchildren, and confirmed myopia appears to be rising rapidly at younger ages. These findings support closer surveillance and earlier school-based intervention in Vietnam and similar settings.