Dose–Response Relationship of Outdoor Exposure and Myopia Indicators: A Systematic Review and Meta-Analysis of Various Research Methods

• Main Authors: Ciao-Lin Ho, Wei-Fong Wu, Yiing Mei Liou
• Format: Article
• Language: English
• Published: MDPI AG 2019-07-01
• Series: International Journal of Environmental Research and Public Health
• Subjects: axial length; near-sightedness; preschool; school age; spherical equivalent refractive error (SER)
• Online Access: https://www.mdpi.com/1660-4601/16/14/2595

Myopia in children has dramatically increased worldwide. A systematic review and meta-analysis were conducted to evaluate the effects of outdoor light exposure on myopia. According to research data from 13 studies of 15,081 children aged 4&#8722;14 at baseline, outdoor light exposure significantly reduced myopia incidence/prevalence (odds ratio [OR] = 0.85, 95% confidence interval [CI]: 0.80&#8722;0.91, <i>p</i> &lt; 0.00001; I2 = 90%), spherical equivalent refractive error (SER) by 0.15 D/year (0.09&#8722;0.27, <i>p</i> &lt; 0.0001), and axial elongation by 0.08 mm/year (&#8722;0.14 to &#8722;0.02, <i>p</i> = 0.02). The benefits of outdoor light exposure intervention, according to pooled overall results, included decreases in three myopia indicators: 50% in myopia incidence, 32.9% in SER, and 24.9% in axial elongation for individuals in Asia. Daily outdoor light exposure of more than 120 min was the most effective intervention, and weekly intervention time exhibited a dose&#8722;response relationship with all three indicators. Subgroup comparisons revealed that interventional studies report greater benefits from outdoor light exposure compared with cohort and cross-sectional studies, and individuals with myopia in intervention studies experienced slightly greater benefits than individuals without, in terms of SER and axial elongation. Therefore, this study suggests 120 min/day of outdoor light exposure at school.