A natural experiment in school lighting: observational evidence linking far-red light exposure to slower myopia progression in Chinese Uyghur schoolchildren.

BACKGROUND

Childhood myopia is a growing problem worldwide. In a primary school in Xinjiang, China, some classrooms had been installed with far-red/near-infrared (FR/NIR) lighting, while others kept conventional lights. This natural experiment let us test whether everyday exposure to FR/NIR light is linked to slower myopia progression in Uyghur children-a group often understudied despite high myopia rates.

METHODS

In this one-year prospective observational cohort study, we invited all eligible Uyghur children in grades 2 and 3. Exposure groups were defined by pre-existing classroom lighting conditions (FR/NIR-enriched vs. Conventional-lit). Primary outcome was change in axial length (AL); secondary outcome was change in spherical equivalent refraction (SER, calculated as sphere + ½ cylinder). Propensity score matching (PSM) was employed to address confounding, with sensitivity analyses (ANCOVA and IPTW-ANCOVA) conducted to assess robustness.

RESULTS

After PSM, 82 participants (41 per group) were included. AL increase was significantly smaller in the FR/NIR-enriched group (0.19 ± 0.09 mm) than Conventional-lit group (0.34 ± 0.12 mm), with a mean difference of -0.15 mm (95% CI: -0.20 to -0.10; P < 0.001). SER myopic shift was also attenuated in the FR/NIR-enriched group (-0.12 ± 0.46 D vs. -0.52 ± 0.59 D), yielding a mean difference of 0.40 D (95% CI: 0.16 to 0.64; P < 0.001). Subgroup analyses suggested age-related differences.

CONCLUSIONS

Over one year, children in classrooms with FR/NIR-enriched lighting showed slower eye growth and less myopic shift. With careful statistical adjustment, these findings suggest that changing classroom lighting could be a simple, passive way to help control myopia at the population level.