Increasing weekly outdoor activity can reduce the risk of myopia onset and myopic shift, according to a meta-analysis of clinical studies.
“Our meta-analysis found an overall protective effect against myopic shift and axial elongation with outdoor activities,” Li Deng, PhD, and Yi Pang, MD, OD, PhD, wrote in their study published in Optometry & Vision Science. “The overall treatment sizes for both myopic shift and axial elongation were small and clinically nonsignificant.”
The meta-analysis was conducted using a literature search of PubMed, MEDLINE, Scopus, EMBASE, VisionCite and Cochrane Library. Studies were selected if authors included a clearly defined intervention group with different levels of outdoor exposure, if they were prospective intervention trials, if participants were between 6 and 18 years old, and if the studies measured myopia progression and/or axial length elongation.
Researchers analyzed the benefit of outdoor activity considering relative risk, difference in myopic shift rate and difference in axial elongation rate in five studies. Children were assigned to three groups: initial myopes, initial nonmyopic or mixed.
Researchers found that the myopic shift rate was slower in the intervention group compared to the control group (0.13 D/year; 95% confidence interval, 0.08 D to 0.18 D). Axial elongation was also slower in the intervention group (0.03 mm/year; 95% CI, 0.05 D to 0.00 D). Reduced myopic shift was observed in all initially nonmyopic cohorts (three of three) and most initially myopic cohorts (two of three).
The risk of developing myopia was lower with more hours of outdoor activity per week (relative risk, 0.66; 95% CI, 0.49 to 0.89). This finding varied per individual study (P = .07). Researchers note that more studies are needed to determine how outdoor activities reduce myopia onset and progression.
Limitations included a lack of a consistent intervention definition, inconsistent differences in hours spent outdoors, and varying sample size and selection biases across studies.
“The meta-analysis results suggest that there is a slightly lower risk of myopia onset and myopic shift with more hours of outdoor activities,” they wrote. “Future clinical trials are needed to assess its long-term effect and whether the effect varies by initial myopic status.” – by Julia Lowndes
Disclosures: The authors report no relevant financial disclosures.