Increasing the amount of time children spend outdoors can help prevent the development of myopia

This article presents a review of the literature regarding the role of time outdoors as a protective factor in the prevention of myopia. It also examines some of the biological ways in which time outdoors helps to prevent myopia and suggests that increasing the amount of time that children spend outdoors be considered a preventive measure to the development of myopia.

Findings from 19 major epidemiological studies were reviewed. All of these studies were published between 2002 and 2013, with the exception of one which was published in 1993. While most of the studies focused on school-age children, the age range was 6 months to 26 years. The number of participants for any one study ranged from 145 to over 4000. These cross-sectional and longitudinal studies were conducted in ten different countries and included several different ethnic groups.

Findings indicate that children who spend more time outdoors are less likely to be or become myopic. This was true even for groups with a high prevalence of myopia and irrespective of how much near work the individuals do or whether their parents are myopic.

Some studies suggest that it's the light-stimulated release of dopamine from the retina which serves as the protective factor while outdoors. Increased dopamine release appears to inhibit increased axial elongation, which is the structural basis of myopia. What is clearly indicated by the data is that time spent outdoors is important for normal refractive development in children. What is not clear is whether time outdoors also regulates progression in those with established myopia. Some reports indicated that there are seasonal variations in progression which may be explained, in part, by time outdoors. The authors conclude that the effects of time outdoors are large enough to make investigation of its use in prevention worthwhile. They note, for example, that longitudinal data suggest that the chance of becoming myopic is reduced by about one third if time spent outdoors is increased from 0 - 5 hours per week to 14 or more per week.