The association of time outdoors and patterns of light exposure with myopia in children: implications for prevention

Abstract

Purpose : This cross-sectional study evaluates the association of time outdoors and light exposure patterns with myopia in children from the Singapore Growing Up Towards Healthy Outcomes (GUSTO) birth cohort

Methods : We performed cycloplegic spherical equivalent (SE), myopia (SE≤-0.5D) and axial length (AL) measurements in 422 multi-ethnic children (41.2% myopic; 47.6% girls; 59.5% Chinese) who attended the 9-year GUSTO visit and were not on myopia treatment (atropine and orthokeratology). Time outdoors in the past month (physical or leisure activities) was assessed with a questionnaire and outdoor activity types with an activity diary filled over 7 days. Light exposure patterns: light levels (lux), duration, timing (morning: 7-11 AM; afternoon: 11 AM-3 PM; evening: 3-7 PM) and frequency of light exposure (number of outdoor episodes ≥1000 lux continuously ≥5mins) were measured with a wrist-worn watch (FitSight) over 14 days. Paired eyes (n=844) were analyzed using Generalized Estimating Equations with multivariable linear or logistic regression model

Results : Time outdoors (Mean±SD:1.65±1.42 hours/day) and average light levels (467±231 lux) were low, with 76.0% of the daily duration of light exposure <5000 lux. Light levels were highest during mid-day, compared to the morning or evening (Ps<0.001). Children exhibited 1.7±1.0 daily outdoor episodes. Time outdoors, the duration and frequency of light exposure were higher on weekends than weekdays (Ps<0.05). Boys exhibited higher light levels, duration and frequency of light exposure than girls (Ps<0.05). While outdoors, children spent the longest duration on walks, neighborhood play and swimming. In multivariable analyses, time outdoors was associated with lower odds of myopia (OR=0.79; 95% confidence interval (CI): 0.67 to 0.93; P=0.005) and less myopic SE (β=0.15D; 95% CI:0.01 to 0.29; P=0.034) but not associated with AL (P=0.15). Light levels were not associated with myopia and SE but were marginally associated with AL (β=-0.31mm; 95%CI: -0.62 to -0.003; P=0.048). The duration, timing or frequency of light exposure were not associated with myopia, SE or AL (Ps>0.05)

Conclusions : Increasing time outdoors was protective against myopia and myopic SE. Light levels or specific outdoor light patterns were not associated with myopia. Longitudinal studies are needed to confirm these findings

This is a 2021 ARVO Annual Meeting abstract.