Researchers have found that increased time outdoors provides limited protection for premyopic children.
The goals of the investigators in Shanghai, China, were to provide evidence-based recommendations for myopia prevention, as well as reduce the prevalence of potentially pathological high myopia in the longer term.
To do that they monitored 3194 children in Shanghai between the age of six and nine, who all wore wristwatches to monitor time outdoors from 2017 to 2018.
The children were either premyopes or hyperopes.
Participants were all examined for cycloplegic refraction and myopic shift was studied from baseline to a one-year follow-up.
Hyperopes showed reduced myopic shift with increasing outdoor time (plateau at about 120 minutes per day).
But premyopes exhibited a J-shaped relationship between time outdoors and myopic shift, the study said.
In comparison to the subgroup with daily time outdoors of less than 60 minutes, the difference in spherical equivalent change in the other subgroups was not statistically significant.
The reduced myopic shift was only observed with time outdoors greater than 120 minutes per day, although it was still not statistically significant, said the researchers.
“We found that time spent outdoors had a limited protective effect on myopic shift among premyopic children, distinct from the dose-dependent protective effect observed in hyperopic children,” said the researchers in the Shanghai Time Outside to Reduce Myopia (STORM) study, which has been published in the British Journal of Ophthalmology.
“This finding reveals the unique dynamics of myopic shift within the premyopic population, highlighting the need for more intensive interventions.”
They concluded that the findings held “significant implications for future myopia prevention efforts”.
“While the protective effects of time outdoors are clear for children with hyperopia, the protective effect of time outdoors on myopic shift among children with premyopia is more limited and was only seen with longer durations of time outdoors.
“Nevertheless, in school-based interventions, given the other benefits of time outdoors, increased time outdoors should be provided for all children. However, additional interventions, such as low dose atropine or red-light therapy, to prevent or delay myopia onset in premyopic children, may be useful.”
