A recent study sparks debate on the effectiveness of outdoor exposure for children at risk of myopia.
The Surprising Findings:
Research published in the British Journal of Ophthalmology aimed to uncover the impact of outdoor time on myopia development in children with premyopia. Premyopia, an early stage before clinical myopia, presents a crucial opportunity for intervention. Previous studies have shown that spending time outdoors can significantly reduce the onset of myopia in non-myopic children, with a relative reduction ranging from 11% to 52%.
But here's the twist: While these studies included children with hyperopia and premyopia, the specific effects on premyopic children were not thoroughly examined.
The Study in Focus:
In a post-hoc analysis of the Shanghai Time Outside to Reduce Myopia (STORM) study, researchers tracked 6- to 9-year-old participants without myopia using smartwatches to measure their time outdoors over a year. The children were divided into four groups based on their daily outdoor time:
- 60 minutes or less
- 61 to 90 minutes
- 91 to 120 minutes
- More than 120 minutes
Premyopia was defined by specific refractive measurements, and myopic shift was tracked over a year.
The Results:
Out of 3,194 participants, nearly 43% were premyopic, with an average age of 8.2 years. Interestingly, there was no significant difference in outdoor time between premyopic and hyperopic children. Hyperopic children showed a reduced myopic shift with more time spent outdoors, but the relationship was different for premyopic children. Their myopic shift had a J-shaped curve, indicating a limited protective effect that only became significant at the highest outdoor exposure levels.
When comparing subgroups, the difference in refractive changes was not significant for 61-90 minutes and 91-120 minutes of daily outdoor time. Only with more than 120 minutes of outdoor time was a reduced myopic shift observed, but it wasn't statistically significant.
Within a year, 31% of premyopic children progressed to myopia, while only 0.3% of hyperopic children did. Additionally, 33.6% of children moved into the premyopic range.
Expert Insights:
The study authors emphasize the need for premyopic children to spend more time outdoors in moderate light conditions (3,000-5,000 lux) to achieve a protective effect. They propose several explanations for the differing effects between premyopic and hyperopic children. For instance, premyopic individuals may already be experiencing lens power reduction and axial elongation, which could contribute to the limited protective effect.
Controversial Aspects:
However, the study has its limitations. The premyopia category includes children at various refractive development stages, which might impact the results. Additionally, the light intensity measured by smartwatches may not accurately represent what the eye receives, and near work was assessed through a questionnaire, which could introduce bias. Socioeconomic factors, diet, and genetic risks beyond parental myopia were not fully considered, and the study's duration might not capture long-term effects.
The Bottom Line:
While outdoor exposure has a protective effect for hyperopic children, its impact on premyopic children is more nuanced. Longer outdoor durations or additional interventions may be necessary to prevent myopia in premyopic children. This study highlights the complexity of myopia prevention and the need for further research to optimize strategies for children at different stages of refractive development.
What are your thoughts on these findings? Do you think the study's limitations affect the interpretation of the results? Share your opinions and join the discussion!
