The impact of outdoor time on myopia development in overweight children: insights and future research directions

Dear Editors, The article titled ‘Effect modification of time spent outdoors on the association between early childhood overweight and myopia: a one-year follow-up study’ in Volume 46, Issue 1, March 2024, presents substantial findings.1 It suggests that this is a promising intervention. Although the study makes several valuable contributions, several aspects warrant further investigation. The study assumes a direct causal link between outdoor time and reduced myopia risk, yet it does not fully explore other potential confounding variables. Factors such as genetic predisposition, socioeconomic status, indoor activities and dietary habits could also influence the onset of myopia. Future studies should aim to control these variables to ensure that the observed effects are primarily due to outdoor time. Furthermore, while the study provides evidence that increasing outdoor time can reduce myopia onset more among overweight children than normal-weight children, it does not sufficiently explain the underlying mechanisms. A more comprehensive understanding of how outdoor time influences biological processes related to myopia development, such as light exposure, physical activity and eye growth, could be gained by further investigation.2 While informative, the study’s follow-up period of one year may not be sufficient to understand the long-term impact of outdoor time on myopia progression. Myopia is a condition that develops over several years,3 and thus, longer-term studies are necessary to assess whether the protective effects of outdoor time are sustained over time or if they diminish.4–7 Future research should consider several areas. Firstly, future studies should include a broader range of potential confounders, such as genetic factors, socioeconomic status, indoor activities and dietary habits, to more precisely isolate the effect of outdoor time on myopia. Secondly, extending the follow-up period beyond 1 year would provide valuable data on the long-term effects of outdoor time on myopia progression. This would help determine whether the benefits observed in the short term are sustained over several years. Furthermore, investigating the biological mechanisms by which outdoor time affects myopia development is also crucial. Studies could examine how factors such as light exposure, physical activity levels and time spent focusing on distant versus near objects influence eye growth and development. Additionally, conducting studies in diverse populations, including different geographic regions, urban and rural settings, and various socioeconomic groups, would help determine the generalizability of the findings. Tailored interventions could then be developed to suit different contexts and maximize their effectiveness. Future studies can build on these insights by questioning assumptions, considering alternative perspectives and demanding rigorous evidence to develop more effective solutions for myopia prevention.