Myopia prevalence in Canadian school children: a pilot study

PurposeA pilot study to determine the prevalence of myopia, proportion of uncorrected myopia and pertinent environmental factors among children in a suburban region in Canada.MethodsRefraction with cycloplegia and ocular biometry were measured in children of two age groups. Myopia was considered at a spherical equivalent refraction (SER) ≤−0.50 D in at least one eye. Parents completed a questionnaire that captured the child’s daily activities.ResultsA total of 166 children completed the study (83 aged 6–8 and 83 aged 11–13). Myopia prevalence was 17.5% among the overall group, 6.0% among ages 6–8 and 28.9% among ages 11–13. Mean subjective SER in myopic children was −1.10 D (95% confidence interval (CI), −0.34 to −1.86 D) at ages 6–8 and −2.44 D (95% CI, −1.71 to −3.18 D) at ages 11–13. In this study, 34.5% of the myopic children were uncorrected, which represented 6.0% of the entire group of children. Mean axial length (AL) increased by 1.03 mm from ages 6–8 (mean 22.62 mm; 95% CI, 22.45 to 22.79 mm) to ages 11–13 (mean 23.65 mm; 95% CI, 23.45 to 23.84 mm; p < 0.01). The correlation coefficient between AL and SER was −0.618 (p < 0.01). Binary logistic regression between outdoor time and the prevalence of myopia showed that one additional hour of outdoor time per week lowered the odds of a child having myopia by 14.3% (p = 0.007).ConclusionMyopia prevalence increased from 6% at ages 6–8 to 29% at ages 11–13. Thirty-five per cent of the myopes in this study were uncorrected. More time outdoors may be beneficial to protect against myopia onset.