Study shows increasing myopia in Canada, benefits of time outdoors
A pilot study conducted in the Waterloo region of Canada found an estimated myopia prevalence of 6% in children between 6 and 8 years of age, growing to 28.9% in the 11-year-old to 13-year-old age group.
Uncorrected myopia was quite frequent, and the protective effect of time spent outdoors was confirmed.
Children were tested at school for cycloplegic refraction, and parents answered a questionnaire about their children’s indoor and outdoor activities. Family history of myopia was also investigated. A total of 166 participants completed the study.
The overall prevalence of myopia in the study population was 17.5%. In children between 6 and 8 years old, the prevalence was 6%, increasing to 28.9% between the ages of 11 and 13 years. The degree of myopia and the mean axial length were also greater in the older age group. Overall, 34.5% of myopic children were uncorrected.
Time spent outdoors was the only activity that showed a correlation with refraction: 1 additional hour per week spent outside decreased the odds of myopia by 14.3%. Family history of myopia was an additional risk factor. One myopic parent in the family increased the odds of developing myopia by a factor of 2.52, showing that the genetic component still has a primary role and that a combination of both genetics and environmental factors determines the final visual outcome.
"The prevalence of myopia continues to increase worldwide at an alarming rate, and Canada is no exception,” study author Mike Yang, OD, BSc, told Primary Care Optometry News. “The increased prevalence and the shift toward onset at earlier ages will result in a greater incidence of higher prescriptions. High levels of myopia are associated with ocular diseases that can lead to significant visual impairment.
The results of the Canadian study paint a troubling picture but also demonstrate that outdoor time can be a significant factor in reducing the risk of becoming myopic, with 1 additional hour per week reducing the odds of becoming myopic by over 14%,” he continued. “The results reinforce the importance of regular annual eye exams for children.” – by Michela Cimberle
Disclosure: The authors reported no relevant financial disclosures.