July 13, 2026
By Kevin Chan, OD, MS, FAAO, FBCLA, IACMM
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The global rise in myopia is widely understood as an intriguing gene–environment interaction. Environmental and behavioral factors, particularly prolonged near work, intensive schooling, limited daylight outdoor time and changing patterns of screen use and sleep have become more integral to current preventative measures of myopia progression.
While daytime outdoor light exposure has been observed as a protective factor for yet-myopic children, the role and implications of nighttime light exposure are less clear and often overlooked. Interestingly, it has also increasingly become more prevalent in children’s lives in modern age. When children are exposed to streetlights, illuminated buildings, advertising signs, traffic lighting and indoor electric lighting well into the night, a key question arises: How do these artificial environmental exposures potentially influence ocular growth beyond clinical interventions?
Recent research by Li et al. examined whether outdoor artificial light at night, also known as ALAN, is associated with childhood myopia among children in Hong Kong. The study combined a large cross-sectional baseline analysis with a prospective cohort follow-up, making it one of the more substantial epidemiologic investigations of nighttime environmental light exposure and pediatric refractive development.
Study Design and Analysis
The study used data from the Hong Kong Children Eye Study, a population-based cohort with a three-year follow-up. At baseline, 19,114 children were included, with a mean age of 7.40 years and 52.8% boys. A prospective subgroup of 2,558 children who were not myopic at baseline completed follow-up and contributed to the incidence analysis.
Outdoor ALAN exposure was estimated within 500 meters of each child’s residence using time-varying satellite data. Myopia was defined using cycloplegic spherical equivalent refraction of −0.50D or less, which is a standard clinical and epidemiologic threshold.
Key Findings
- Each interquartile range increase in outdoor ALAN exposure was associated with 8% higher odds of prevalent or existing myopia at baseline.
- Among initially non-myopic children followed prospectively, each interquartile range increase in outdoor ALAN exposure was associated with a 26% higher risk of incident myopia.
- The exposure-response relationship for incident myopia was non-linear, with risk increasing more sharply above approximately 93.08 nW/cm²/sr.
- Older children, defined in the study as those aged 7.35 years or above, appear more vulnerable to ALAN-associated incident myopia than younger children.
Study limitations and considerations
- Observational design: It primarily focuses on association, with limited plausibility of drawing causative effect.
- Localized exposure estimate: ALAN was measured around the home, which may not fully reflect children’s actual nighttime light exposure indoors, during travel or at other locations.
- Generalizability: Findings from Hong Kong as an urban high-density area with high educational demand may not necessarily apply to rural areas, lower-density cities or regions with different lighting infrastructure and educational routines.
Practical Applications for Clinicians
- Further history probing: Ask questions about bedroom darkness, nearby outdoor lights, sleep timing and length of screen use before bed.
- Target higher-risk children: Pay particular attention to children with sudden onset of rapid refractive progression, or prolonged nighttime light exposure in highly illuminated neighborhoods.
- Reevaluate slow-responding children: Results aren’t derived from clinical interventions alone. For those with inconsistent or stagnant treatment responses, artificial environmental factors are worth further exploration.
Action Plans for Patients and Families
- Modify evening environment: Lower indoor light intensity and avoid unnecessary bright lights in the hour before bedtime.
- Increase daylight outdoor time: Encourage safe outdoor activity during the day, especially after school and on weekends.
- Regulate near work: Build in regular breaks during reading and device use.
- Make the bedroom darker: Use curtains, blinds or room arrangements that reduce direct nighttime light entering the sleeping area.
- Protect sleep timing: Keep a consistent bedtime and reduce late-night studying or screen exposure when possible.
- Schedule comprehensive eye examinations early: Timely eye examinations for children are paramount – particularly for those with strong family history of myopia, or observable symptoms, such as squinting, eye rubbing and blurry vision at distance.
My Perspective
Li et al. illustrates clinically relevant findings that higher outdoor artificial light at night (ALAN) around the home is associated with greater myopia prevalence and incidence among children in Hong Kong.
The merits of this study can also extend to other urban cities or highly illuminated areas at night, thus affecting future policy planning and regulation at the public health scale. Nevertheless, clinicians and parents should interpret the findings prudently since no causation between ALAN and myopia development is yet established.
Clinical success roots from a clinician’s astute and proactive preventative measures, along with child and parental awareness and attention on environmental stimuli in daily lives.
Abstract
Outdoor Artificial Light at Night Exposure and Risk of Myopia: A Cross-Sectional and Prospective Cohort Study Among Hong Kong Children
Yingan Li, Yuzhou Zhang, Ka Wai Kam, Yuhan Cui, Poemen Chan, Patrick Ip, Wei Zhang, Alvin Young, Chi Pui Pang, Clement C. Tham, Li Jia Chen, Mei Po Kwan, Jason C. Yam
Background
Methods
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