Relationship Between Physical Activity and Visual Acuity in Japanese Students: A Cross-Sectional Study.

Background and Aims: Physical activity, including outdoor activities, has been assessed using questionnaires or accelerometers. Examining the relationship between physical activity and myopia is important for future intervention studies. This study aimed to evaluate physical activity using a widely used questionnaire and an accelerometer and to examine their relationship with myopia. Methods: In Study 1, physical activity was assessed using a questionnaire in 613 primary school students (Grades 3-6, aged 8-12) and 438 secondary school students (Grades 1-3, aged 12-15). In Study 2, physical activity in 55 primary school students (Grades 3-6, aged 8-12) was measured using an accelerometer. Visual acuity was determined using Landolt ring tests. Screen time was also assessed in both studies. The relationship between physical activity (independent variable) and visual acuity (dependent variable) was analyzed using binomial logistic regression, adjusting for grade, gender, and screen time. Results: No significant association was found between visual acuity and physical activity as measured by either questionnaire or accelerometer in both primary and secondary students, even after adjustments for grade, gender, and screen time. Conclusion: Physical activity measured by questionnaires and accelerometers did not show an association with myopia. However, this does not exclude a potential association between outdoor activity and myopia. Our findings suggested that these methods of assessing physical activity may not be suitable proxies for outdoor activity in myopia research.