Time outdoors, near work influence axial length in children

ORLANDO, Fla. — Results from a study involving 4,000 children showed that spending at least 2 hours a day outside decreases axial length and that more than 1 hour a day of near work increases it.

Jan Roelof Polling, of the Erasmus Medical Center in Rotterdam, Netherlands, reported the results of the Generation R Study here at the Association for Research in Vision and Ophthalmology meeting. Polling said this multi-ethnic, population-based, birth-cohort study included 6,690 children, of which visual acuity and axial length were obtained at the age of 6 years. Data regarding time the children spent outdoors as well as performing near work tasks were collected from 4,059 children via questionnaire.

Polling said outdoor habits included activities such as walking to school, sports and outdoor playing, and the questionnaire asked for how many days, for how long and whether in the morning or evening. Because children do not start reading until after the age of 6 years, they were questioned about the use of hand-held computers, TVs and DVDs, he said.

The prevalence of myopia in this group was 1.9% (129 children), according to the abstract.

The mean axial length was 22.64 mm for boys and 22.09 mm for girls, Polling said, and 22.35 mm for non-myopes and 23.32 mm for myopes.

The boys studied tended to spend a little more time outdoors and performing near work than girls, Polling said.

The highest number of myopic children, 82, were seen in the group that spent a lot of time on near work and little time outdoors, he said. Of all nonmyopic children, those who spent a lot of time outdoors and little time on near work had the shortest axial length.

“Outdoor activity in myopia is a good protective factor for the onset and progression, and near work is a risk factor for myopia,” Polling said.

The authors concluded in the abstract that playing outside less than an hour a day increased the risk of higher-than-average axial length by 34%, while time spent on near work was not significantly associated with axial length.

“Parents of children at risk of myopia progression should be made aware of the protective effect of outdoor exposure in very young children,” they said.

Disclosure: The authors have no relevant financial disclosures.