We often hear that getting kids to play outside can help protect their eyesight and prevent nearsightedness. But a new look at the data suggests the story is more complicated, especially for kids who are already at high risk. The study followed over 3,000 children in Shanghai, using smartwatches to track exactly how much time they spent outdoors. It focused on two groups: kids who were slightly farsighted (hyperopic) and kids who were on the very edge of becoming nearsighted (premyopic). For the farsighted kids, the message was clear: more time outside meant less shift toward nearsightedness over a year, with benefits leveling off after about two hours a day. But for the kids already at the brink of nearsightedness, the results were different. They showed a 'J-shaped' relationship with outdoor time. Compared to kids who spent less than an hour outside, those who spent between one and two hours outdoors saw no significant difference in their eye prescription change. Only when kids spent more than two hours outside was there any hint of a protective effect, and even that result was not strong enough to be statistically certain. The study concludes that for children already at high risk for nearsightedness, simply increasing outdoor time may have a limited effect, and we might need to look at longer durations or additional strategies to help them.
Does playing outside protect kids' eyesight? For some children, it might not be enough.
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What this means for you:
For kids on the verge of nearsightedness, playing outside may offer less protection than we thought. What this means for you:
For kids on the verge of nearsightedness, playing outside may offer less protection than we thought. View Original Abstract ↓
AIMS: To investigate the effect of time outdoors on myopic shift among premyopic children.
METHODS: Post-hoc analysis was nested in a cluster-randomised trial of the Shanghai Time Outside to Reduce Myopia (STORM) study. 6- to 9-year-old participants without myopia from the STORM study, who wore wristwatches to monitor time outdoors from 2017 to 2018, were included. Participants were all examined with cycloplegic refraction. Daily time outdoors was objectively monitored with the wearable smartwatch. Premyopia was defined as a cycloplegic spherical equivalent (SE) from -0.50 to +0.75 (inclusive) dioptres (D). Myopic shift was SE change from baseline to 1 year follow-up.
RESULTS: Among 3194 participants (1369 premyopic; mean age 8.2±0.6 years; 49.5% boys), there were no statistical differences between premyopic and hyperopic children in time outdoors (p=0.303). Hyperopes showed reduced myopic shift with increasing outdoor time (plateau at about 120 min/day). However, premyopes exhibited a J-shaped relationship between time outdoors and myopic shift. In comparison to the subgroup with daily time outdoors <60 min, the difference in SE change in the other subgroups was not statistically significant (61-90 min/d: -0.03 (95% CI -0.10 to 0.05); 91-120 min/d: -0.03 (95% CI -0.11 to 0.05)). The reduced myopic shift was only observed with time outdoors >120 min/d, although it was still not statistically significant (>120 min/d: 0.04 (95% CI -0.05 to 0.14)).
CONCLUSIONS: Among premyopic children, increased time outdoors has a limited protective effect on myopic shift, suggesting longer duration of time outdoors or additional interventions to prevent or delay myopia onset in this population.