Key Takeaways

• Higher residential outdoor artificial light at night was associated with both greater prevalence of childhood myopia and a 26% increased risk of developing myopia over 3 years
• The association with incident myopia appeared nonlinear, with risk increasing substantially once nighttime light exposure exceeded approximately 93 nW/cm²/sr
• Additional longitudinal and mechanistic studies are needed before causal conclusions or public health recommendations can be made

Children exposed to higher levels of outdoor artificial light at night (ALAN) around their homes were more likely to have myopia and more likely to develop myopia over 3 years, according to a new population-based study from Hong Kong.¹ The findings suggest that nighttime light pollution may contribute to refractive development independently of established behavioral and familial risk factors.

Published in Environmental Research, the investigation analyzed data from 19,114 children participating in the Hong Kong Children Eye Study, with a prospective cohort of 2,558 initially nonmyopic children followed for 3 years. Outdoor ALAN exposure was estimated using satellite-derived nighttime light measurements within a 500-meter radius of each child's residence and linked to cycloplegic refractive outcomes.

The investigators found that each interquartile range increase in outdoor ALAN exposure was associated with:

• 8% higher odds of prevalent myopia (odds ratio [OR] 1.08; 95% CI, 1.02–1.15)
• 26% higher risk of developing myopia during follow-up (hazard ratio [HR] 1.26; 95% CI, 1.16–1.37)

These associations remained significant after adjustment for age, sex, baseline refractive status, outdoor activity, near-work time, parental myopia, socioeconomic factors, sleep duration, indoor bedroom lighting, greenspace, and air pollution exposure.

Children living in the highest quartile of nighttime light exposure experienced a 34% greater risk of incident myopia compared with those in the lowest exposure quartile (HR 1.34; 95% CI, 1.12–1.60).

Rather than a simple linear relationship, investigators observed nonlinear exposure-response patterns. For incident myopia, risk remained relatively stable until outdoor ALAN reached approximately 93 nW/cm²/sr, after which the hazard increased sharply. The restricted cubic spline analysis demonstrated significant nonlinearity (P=0.007), suggesting a possible exposure threshold above which risk accelerates. Among prevalent myopia, the strongest increase in odds occurred at lower exposure levels before plateauing at higher light intensities.

Age significantly modified the relationship between nighttime light exposure and incident myopia. Children aged 7.35 years or older demonstrated a stronger association between ALAN exposure and new-onset myopia (HR 1.27; 95% CI, 1.17–1.39), whereas no statistically significant association was observed among younger children. Investigators speculate this may reflect both greater academic demands leading to later bedtimes and a developmental period characterized by more rapid axial elongation.

The authors note several biologically plausible mechanisms linking nighttime light exposure with refractive development.

Outdoor ALAN may suppress nocturnal melatonin secretion and disrupt circadian rhythms through activation of intrinsically photosensitive retinal ganglion cells, particularly because modern LED lighting contains substantial short-wavelength blue light. Circadian disruption has previously been associated with altered axial length rhythms and abnormal ocular growth in experimental models. The investigators also cite evidence that light wavelength itself may influence refractive development through retinal signaling and chromatic aberration pathways, raising the possibility that blue-enriched nighttime lighting could affect eye growth through multiple mechanisms.

The authors emphasize that the study demonstrates an association rather than causation.

Among the principal limitations:

• Outdoor satellite-derived light measurements served as a proxy for individual exposure and could not account for indoor lighting, electronic device use, blackout curtains, or sleep masks.
• Residual confounding remains possible despite adjustment for numerous behavioral, socioeconomic, and environmental variables.
• Approximately 18% of initially nonmyopic children completed the full prospective follow-up.
• The cohort consisted primarily of Chinese children living in Hong Kong, which may limit generalizability to other populations or environments.

The investigators concluded that future studies incorporating objective personal light monitoring and mechanistic research will be needed before nighttime lighting can be considered a modifiable target for myopia prevention or urban planning policies.

Reference

1. Li Y, Zhang Y, Kam KW, et al. Outdoor artificial light at night exposure and risk of myopia: a cross-sectional and prospective cohort study among Hong Kong children. Environ Res. 2026;303:124647. doi:10.1016/j.envres.2026.124647.