Taking part in physical activities may be an effective way for kids to reduce the prevalence of myopia. Photo: Getty Images.

In a new study, researchers aimed to investigate the prevalence of myopia and determine the association between physical activity and risk of myopia among primary school students. The study was conducted in Tianjin, China. They found an association between physical activities and a decrease in myopia prevalence, as well as myopia being higher in girls than boys.

A total of 2,976 participants (1,568 girls and 1,408 boys) were included. They underwent visual acuity and spherical equivalent (SE) with noncycloplegic autorefraction measurement. Myopia was defined as an SE refraction ≤−0.50D and an uncorrected visual acuity <5.0 in either eye.

The overall prevalence of myopia was 52.9% among this Asian population of kids ages six to 12. The researchers noted in their paper for Translational Vision Science & Technology  that the overall high prevalence of myopia in this study suggests that myopia is a serious public health problem among school children in Tianjin. “Taken together, these results highlight the emergent need for efforts to control myopia in school-aged children,” the authors commented in their article.

Activity was measured via the Physical Activity Questionnaire for Children (PAC), a self-administered, seven-day recall questionnaire that assesses participation in different physical activities, as well as activity during physical education, lunch break, recess, after school, in the evenings and at weekends, the paper on the research explains. Respondents choose from a 1-5 scale to report their level of activity for each item, then the researchers calculate a composite score for each subject.

There was a significant association between higher physical activity and lower risk of having myopia (OR = 0.762). After adjusting for age, sex and school region and using the lowest quartile of PAC scores as the reference group, there was a significant association between decreased odds of myopia and physical activity in the second quartile (OR = 0.876), third quartile (OR = 0.708), and fourth quartile (OR = 0.676).

As for the potential mechanisms through which physical activity influences myopia development, the authors speculated a bit in their paper. “A possible biological explanation is that specially designed sports activities include the alternation of far-sightedness and near-sightedness, which can replace the conventional regulation function training on children’s kinetic visual acuity, uncorrected distance visual acuity, axial length and accommodative facility, improve the regulatory ability of ciliary muscle, and promote the benign development of dynamic vision,” the authors wrote.

“Open sports are usually accompanied by visual tracking of the target object, and closed sports can also integrate the use of the eyes in a reasonable way to achieve full exercise of visual function,” the paper continues. “Physical exercise relieves eye fatigue caused by long-term attention to static objects and improves the overall health level of the body to promote the development of visual function of teenagers and prevent the decline of myopia and other visual functions.”

The researchers concluded by offering their assessment that regular participation in sports activities is an effective means to prevent myopia. “It plays a positive role in improving the myopia of teenagers. Physical activities may effectively reduce the probability of becoming myopic in children aged six to 12 years and promote eye health.”

The prevalence of myopia was consistently higher in females than males in different physical activity categories, which has also been observed in previous studies. The authors investigated potential underlying mechanisms for these gender differences and found that it might be decided by biological factors, outdoor activity time and a high amount of near-vision work.

“Large international studies show that girls have better reading scores and attitudes than boys around the world,” the researchers wrote. “Boys spend more time on games and computers than girls. The increase in working hours on near work is an important risk factor for myopia, but this effect can be compensated for by increasing outdoor time.”

The authors concluded that a future longitudinal study is needed to evaluate the progression of myopia in school-aged children and to develop intervention strategies to prevent or slow down the progression of myopia.