Longer wavelengths in sunlight pass through the human body and have a systemic impact which improves vision.
Level 3 - non-randomized controlled study
Controlled interventional laboratory study in humans; randomization is not specified in the abstract.
PubMed 40628952 · doi:10.1038/s41598-025-09785-3
What was done
Researchers measured whether infrared wavelengths from sunlight penetrate through the human thorax. They then exposed human subjects to a specific transmitted solar wavelength band (830–860 nm) directed at the thorax for 15-minute controlled laboratory sessions, testing conditions with and without direct ocular involvement and evaluating the effect of clothing on light transmission. Visual function was evaluated 24 hours post-exposure.
What was found
Infrared wavelengths from sunlight penetrated the human thorax, and while clothing reduced intensity, it did not block transmission. Thoracic exposure to 830–860 nm light was associated with significantly improved visual function 24 hours later, including in subjects whose eyes were completely shielded from light exposure during the session. The abstract provides no exact sample sizes, numerical baseline or post-treatment values, effect sizes, or confidence intervals.
Why it matters
This study provides evidence that localized near-infrared light exposure to the torso can exert systemic functional benefits to distant organs such as the visual system, likely via systemic mitochondrial modulation.
Limits
The abstract does not disclose the sample size, subject demographics, whether allocation was randomized or blinded, or quantitative metrics of visual improvement. Long-term durability beyond 24 hours and the exact underlying biochemical mechanisms in humans were not reported.