Association of Time Outdoors and Patterns of Light Exposure in Myopic Children

Association of Time Outdoors and Patterns of Light Exposure in Myopic Children

June 2, 2025

By Dr. Katrina Wong, Australian College of Optometry

Photo Credit: Getty Images

Animal studies suggest bright light stimulates dopamine release, which inhibits ocular growth.1-3 Chicks have also shown varied growth inhibition to bright light depending on the time of day4 and dosage.5 

Li et al. (2023) aimed to examine the association of reported time outdoors and light exposure patterns with myopia among 483 children aged 9 years in Singapore. This study used questionnaires reporting time outdoors, wrist-band light meters and activity diaries to evaluate associations between these factors and cycloplegic refraction. The key metrics of the study were cycloplegic spherical equivalent (SE), myopia – which was defined as cycloplegic spherical equivalent autorefraction of ≤-0.50D – and axial length.  The study population had low reported time outdoors and low light exposures. 

However, reported time outdoors was found to be protective against myopia. Every additional hour per day of reported time outdoors was associated with lower odds of myopia, but was not associated with spherical equivalent or axial length changes. Light levels, timing and frequency of light exposures were not associated with myopia, spherical equivalent or axial length.

Findings suggest increasing daily time outdoors, even under moderate light levels, rather than specific outdoor light levels and patterns, is protective of myopia. However, this is only one cross-sectional study in a specific population of 9-year-old children in Singapore and may not be comparable to other populations.

Abstract

Association of Time Outdoors and Patterns of Light Exposure with Myopia in Children

Mijie Li, Carla Lanca, Chuen-Seng Tan, Li-Lian Foo, Chen-Hsin Sun, Fabian Yap, Raymond P Najjar, Charumathi Sabanayagam, Seang-Mei Saw

Background/aims

To evaluate the association of reported time outdoors and light exposure patterns with myopia among children aged 9 years from the Growing Up in Singapore Towards Healthy Outcomes birth cohort.

Methods

We assessed reported time outdoors (min/day), light exposure patterns and outdoor activities of children aged 9 years (n=483) with a questionnaire, the FitSight watch and a 7-day activity diary. Light levels, the duration, timing and frequency of light exposure were assessed. Cycloplegic spherical equivalent (SE), myopia (SE≤-0.5 D) and axial length (AL) of paired eyes were analysed using generalised estimating equations.

Results

In this study, 483 (966 eyes) multiethnic children (50.0% boys, 59.8% Chinese, 42.2% myopic) were included. Reported time outdoors (mean±SD) was 100±93 min/day, and average light levels were 458±228 lux. Of the total duration children spent at light levels of ≥1000 lux (37±19 min/day), 76% were spent below 5000 lux. Peak light exposure occurred at mid-day. Children had 1.7±1.0 light exposure episodes/day. Common outdoor activities were walks, neighbourhood play and swimming. Greater reported time outdoors was associated with lower odds of myopia (OR=0.82, 95% CI 0.70 to 0.95/hour increase daily; p=0.009). Light levels, timing and frequency of light exposures were not associated with myopia, SE or AL (p>0.05).

Conclusion

Reported time outdoors, light levels and number of light exposure episodes were low among Singaporean children aged 9 years. Reported time outdoors was protective against myopia but not light levels or specific light measures. A multipronged approach to increase time outdoors is recommended in the combat against the myopia epidemic.

DOI: doi: 10.1136/bjophthalmol-2021-318918

Katrina Wong is an optometrist who graduated from the University of Auckland, Aotearoa/New Zealand in 2010. With an interest in public health and teaching, she completed the clinical residency program at the Australian College of Optometry and is now the Manager of Teaching Services there. She also works for Deakin University as a Teaching Fellow in Optometry and Clinical Practice. She has completed the Australian College of Optometry’s Certificate of Public Health and Leadership. Other areas of work have included volunteering for the Vanuatu Prevention of Blindness Project and work across Northern Territory, Australia with the Brien Holden Foundation providing eye care in Indigenous communities.