Low prevalence of myopia among school children in rural China

We aim to assess the prevalence of myopia in Chinese school children with low educational pressure and explore which factors could explain the differences in prevalence between generations.

A school-based epidemiologic study including 2432 grade 1 and 2346 grade 7 students was conducted from 2016 in rural areas of China. Each participant's refractive status was measured before and after cycloplegia using an autorefractor and axial length (AL) was measured using an IOL Master. The questionnaires were completed by the parents or legal guardians of the children to collect detailed information regarding risk factors. Myopia was defined as spherical equivalent less than - 0.50D.

Grade 7 students had a higher prevalence of myopia (29.4% vs. 2.4%; P < 0.001) and high myopia (0.4% vs. 0.1%; P < 0.001) compared with grade 1 students. Grade 7 students also had longer ALs (23.50 mm vs. 23.37 mm; p = 0.004) after adjusting for the effect of gender, height and other myopia-related risk factors. Adjustment for time spent on reading and writing after school per day led to a reduction in the excess prevalence of myopia in grade 7 students by 15.1%. In addition, adjustment for time outdoors reduced the excess prevalence of myopia in grade 7 students by 33.4%.

We reported a relatively lower prevalence of myopia in school students in rural China, suggesting that Chinese may not have a genetic predisposition to myopia and environmental factors may play a major role in the development of school myopia in Chinese children.