Clinicians can add yet another study to their arsenal of evidence supporting the benefits of outdoor activities for patients at risk for myopia. Researchers from the Illinois College of Optometry found school-aged children who spent more hours doing outdoor activities per week had a reduced chance of developing myopia.

Since myopia is on the rise globally, the study looked at a possible connection between reduced risk of myopia development, myopic shift and axial elongation and additional hours spent outdoors.

The investigators conducted a literature search and included five clinical trials that met their selection criteria. The study used three outcome variables to assess the benefit of intervention: relative risk, difference in myopic shift rate and difference in axial elongation rate and grouped children according to their initial refractive status: myopes, non-myopes or mixed.

Overall, the pooled relative risk data indicated a reduced risk of developing myopia with more hours of outdoor activities per week.

The study found the risk of myopia development in one year was lower in children who spent more hours doing outdoor activities per week, but the outcome varied among studies.

Looking at the myopic shift in one year, the mean difference in the rate between the intervention and control groups ranged from 0.06D/year to 0.23D/year with an overall difference of 0.13D/year. For non-myopic children, myopic shift was consistently slower in the intervention group compared with the control group. For myopic children, the benefit was mixed. In the group of mixed myopic and non-myopic children, an overall benefit of intervention was also observed (0.17D/year).

Only three of the five studies reported axial length. In the three studies, the axial elongation was also found to be slower (−0.03mm/year). The benefit of slowing myopic shift was observed in all initially non-myopic cohorts (three of three) and most of the myopic cohorts (two of three).

“The meta-analysis results suggest that there is a slightly lower risk of myopia onset and myopic shift with more hours of outdoor activities. Future clinical trials are needed to assess its long-term effect and whether the effect varies by initial myopic status,” the researchers wrote in their paper.

While some previous studies have looked at light intensity and other possible factors as the mechanism behind reduced myopia risk, further investigations need to be conducted in this area, the investigators suggested. 

Deng L, Pang Y. Effect of outdoor activities in myopia control: meta-analysis of clinical studies. Optom Vis Sci. March 21, 2019. [Epub ahead of print].