Interventions to increase time spent outdoors for preventing incidence and progression of myopia in children.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 38864362 · doi:10.1002/14651858.CD013549.pub2
What was done
A Cochrane systematic review was conducted to evaluate randomized controlled trials (RCTs) and cluster-RCTs investigating interventions aimed at increasing outdoor time to prevent the incidence and progression of myopia in children. Major electronic databases were searched through June 24, 2022, with no language restrictions. Outcome measures included mean change in refractive error from baseline, incidence of myopia, mean change in axial length, unaided distance visual acuity, quality of life, and adverse events. Evidence certainty was evaluated using GRADE.
What was found
The review included 5 RCTs (4 cluster-RCTs) with 10,733 primary school children (mostly aged 6 to 9 years). For refractive error change: - At 1 year: mean difference (MD) 0.08 dioptres (D) (95% CI -0.01 to 0.17; 4 studies, 1,656 participants; low-certainty evidence). - At 2 years: MD 0.13 D (95% CI 0.06 to 0.19; 4 studies, 2,454 participants; moderate-certainty evidence). - At 3 years: MD 0.17 D (95% CI -0.17 to 0.51; 1 study, 729 participants; low-certainty evidence). For myopia incidence: - At 1 year: 7.1% intervention vs 9.5% control; risk ratio (RR) 0.82 (95% CI 0.56 to 1.19; 3 studies, 1,265 participants; low-certainty evidence). - At 2 years: 22.5% intervention vs 26.7% control; RR 0.84 (95% CI 0.72 to 0.98; 3 studies, 2,104 participants; moderate-certainty evidence). - At 3 years: 30.5% intervention vs 39.8% control; RR 0.77 (95% CI 0.59 to 1.01; 1 study, 394 participants; moderate-certainty evidence). For axial length change: - At 1 year: MD -0.04 mm (95% CI -0.09 to 0.00; 3 studies, 1,666 participants; low-certainty evidence). - At 2 years: MD -0.04 mm (95% CI -0.07 to -0.01; 3 studies, 2,479 participants; moderate-certainty evidence). - At 3 years: MD -0.03 mm (95% CI -0.13 to 0.07; 1 study, 763 participants; moderate-certainty evidence). No included studies reported changes in unaided distance visual acuity or quality of life. No adverse events were reported.
Why it matters
This review provides synthesized evidence restricted strictly to randomized trials showing that school-based outdoor time interventions can modestly reduce the rate of new myopia cases over two years. It helps distinguish genuine trial-level effects from the potential confounding present in prior non-randomized reviews.
Limits
Only five RCTs met inclusion criteria, four of which were cluster designs, and only one trial followed participants for three years. Confidence intervals at one and three years were wide and crossed the line of no effect. Interventions varied across trials (e.g., outdoor lessons, recess policies, motivational messaging), and none of the included studies measured changes in unaided visual acuity or quality of life. Low certainty of evidence precludes clear conclusions on whether outdoor time halts progression in already myopic children.
Cited by
- supports Large studies indicate that children who spend two or more hours per day outdoors have a lower incidence of myopia.