Aims To explore the prevalence and risk factors for myopia and uncorrected myopia in schoolchildren in southern China.

Methods The government-led Shantou Myopia Study was conducted from September 2020 to June 2021. Non-cycloplegic refraction was performed. Uncorrected visual acuity (UCVA) was measured along with presenting visual acuity if participants wore spectacles. Spherical equivalent refraction (SER) is defined as the spherical dioptres added to half of the cylindrical dioptres. Myopia is defined as SER <−0.50 dioptre with UCVA of <20/20 in at least one eye.

Results This study enrolled 724 828 schoolchildren (77.8% of all schoolchildren in Shantou) from 901 schools. Data from 721 032 schoolchildren (99.5%) were analysed (mean age 11.53±3.13 years, 6–20 years, 373 230 boys and 347 802 girls). Among them, 373 459 (51.8%) had myopia: 37.1% of 465 696 children in primary schools, 75.4% of 170 164 children in junior high schools and 84.8% of 85 172 children in senior high schools. The prevalence of myopia increases non-linearly with age. Older age, female and urban living environment were independently associated with myopia prevalence and myopic SER. Among the 373 459 children with myopia, 60.0% had no refractive correction: 74.9%, 53.9% and 35.5% in primary, junior high and senior high schools, respectively.

Conclusion The overall prevalence of myopia among schoolchildren in Shantou was 51.8%, higher than the national average in China. The proportion of uncorrected myopia is high, especially in primary schools. Our results indicate the need for public education on eye care among schoolchildren even in a municipal city.

Data are available upon reasonable request.

http://dx.doi.org/10.1136/bjo-2021-320940

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Data are available upon reasonable request.

HW, YL, KQ and RZ are joint first authors.

HW, YL, KQ and RZ contributed equally.

Contributors HW wrote the manuscript with support from KQ, JCY, LJC and C-PP and with input from all authors. HW, YLi and J-WL analysed the data and designed the figures and tables. MZ, KQ, RZha, HW and DD conceived the study and designed the study project. YLi, KQ and RZha conducted the personnel training and verified the analytical methods. RZha, XL, LL, YLu, DZ, PG, YY, LJ, YH, QM, RZho, YO, QC, YZ, DD and CL, along with the Shantou Myopia Study Group, carried out the implementation and data collection. J-WL and KQ conducted the data management. C-PP and MZ supervised the project and were in charge of overall direction and planning. MZ is guarantor

Funding This work was supported by the Key Disciplinary Project of Clinical Medicine under the Guangdong High Level University Development Program (002-18119101), China, and the Guangdong Science and Technology Special Fund Project (210701206902460), China.

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