To investigate the association of children's refractive errors with their visual activities assessed by questionnaire in the school year and summer break (June, July, and August).
The parents of 147 children aged 6 to 18 years participating in a longitudinal study of refraction and visual function filled out a questionnaire in 1999 listing the number of weekly hours outside of school that the children read for pleasure, studied, watched TV, used the computer/played video games, and engaged in sports/outdoor activities. They also provided hours for these activities during the summer break. Refractions were measured annually by non-cycloplegic distance retinoscopy. Myopes refer to subjects who were myopic (spherical equivalent < −0.5 diopter) at the time of the survey and non-myopes (spherical equivalent refraction > = −0.5 diopter) were emmetropic or in a few cases hyperopic at survey time.
During the school year, myopes spent significantly fewer hours (8.25 ± 6.24 h/week) than non-myopes (10.95 ± 5.95 h/week) in sports/outdoor activity (p < 0.05). In addition, myopes (12.78 ± 9.28 h/week) watched more television than non-myopes (8.91 ± 5.95 h/week) (p = 0.02). No significant refractive group differences were found for other activities. During the summer break, no significant differences were found between refractive groups in any visual activity times. No significant correlations between sports/outdoor activity and TV time were found. Overall, the biggest differences between summer and school activity times were found in outdoor activity (21.76 ± 13.80 vs.10.34 ± 6.10 h/week; p < 0.001) and studying (1.69 ± 3.71 vs. 9.51 ± 6.96 h/week; p < 0.001).
In agreement with other studies, the non-myopes had more hours of sports/outdoor activity during the school year, which may protect against myopia development. A new finding is the high number of sports/outdoor activity hours for both myopes and non-myopes during the summer break, which may contribute to slowed eye growth in all children during these 3 months.
‡PhD, OD, FAAO
Department of Vision Science, New England College of Optometry, Boston, Massachusetts.
This work was supported by National Eye Institute, National Institutes of Health, Bethesda, MD, NEI/NIH grants EY01191, EY014817, and EY018694.
Received September 4, 2009; accepted January 28, 2010.