OBJECTIVE: To analyze the changes in the prevalence of myopia and its relation to ocular biological parameters, and behaviors among primary school students in China, and understand the prevention and control of myopia.
METHODS: Cross-sectional surveys were performed on 7-9-year-old children in the yrs. 2012 and 2019. In addition, spherical equivalent refraction (SER), axial length (AL), and AL/corneal radius ratio (AL/CR ratio) were collected without cycloplegia. Participants completed detailed questionnaires on behavior related to myopia.
RESULTS: Data was collected on 623 children (8.02 ± 0.57 years old) in 2012 and 536 students in 2019 (8.09 ± 0.65 years old). The prevalence of myopia was 37.7% in 2012 and 39.9% in 2019. The SER was -0.25 (0.92) D in 2012 and -0.25 (1.25) in 2019. There was no statistical difference in the prevalence of myopia and SER over the 7 years (all P > 0.05). In 2019, the prevalence of myopia among girls demonstrated an increasing trend (33.8% vs. 37.8%), but there was no statistical difference (P > 0.05). The mean AL and AL/CR ratio of boys were decreasing (all P < 0.05). The proportion of children reading more than 2 h and using digital devices for more than 2 h per day after their classes in the 2019 group both decreased (all P < 0.05). However, the proportion of activities performed outdoors for more than 2 h./day decreased significantly (P = 0.001).
CONCLUSIONS: Compared with 2012, the prevalence of myopia in primary school students in 2019 was under control, which may be related to the improvement of children\'s near-work behavior, but there was the problem of insufficient outdoor activity time. In terms of ocular biological parameters, the risk of myopia for boys in 2019 was lower.

The prevalence of myopia in children is increasing worldwide and is viewed as a major public health concern. This increase has driven interest in research into myopia prevention and control in children. Although there is still uncertainty in the risk factors underlying differences in myopia prevalence between ethnic groups, rates in children of East Asian descent are typically higher regardless of where they live. Mounting evidence also suggests that myopia prevalence in children increases with age. Earlier commencement and more rigorous education systems in these countries, resulting in more time spent on near-work activities and less time on outdoor activities, may be responsible for the earlier age of myopia onset. However, to date, the mechanisms regulating myopia onset and progression are still poorly understood. Findings from several studies have shown orthokeratology to be effective in slowing axial elongation and it is a well-accepted treatment, particularly in East Asian regions. While our understanding of this treatment has increased in the last decade, more work is required to answer questions, including: How long should the treatment be continued? Is there a rebound effect? Should the amount of myopia control be increased? To whom and when should the treatment be offered? Practitioners are now faced with the need to carefully guide and advise parents on whether and when to undertake a long somewhat complex intervention, which is costly, both in time and money. In the near future, a greater demand for effective prophylaxis against childhood myopia is envisaged. Other than orthokeratology, atropine therapy has been shown to be effective in slowing myopia progression. While its mechanism of control is also not fully understood, it is likely that it acts via a different mechanism from orthokeratology. Thus, a combined treatment of orthokeratology and atropine may have great potential to maximise the effectiveness of myopia control interventions.