A new study published in Scientific Reports (July 2025) found that longer wavelengths of sunlight, specifically in the 830–860 nm near-infrared range, can pass through the chest and stimulate beneficial effects in distant organs, including the eyes.
Sunlight penetrates deeply and is absorbed by deoxygenated blood, helping mitochondria in low-oxygen tissues produce more energy. As a result, even without shining light directly into the eyes, participants experienced measurable improvements in vision.
Study findings:
- Near-infrared light (850 nm) penetrated through the body. Using sensors on the front and back of the chest, the researchers showed that light in the 830–860 nm range passed through the body, even when people were wearing clothes. This confirmed that sunlight at these wavelengths reaches deep tissues.
- Vision improved 24 hours later, even when the light was applied to the back. After 15 minutes of light exposure to the back, participants had significantly improved color contrast sensitivity, especially in blue-yellow (tritan) and red-green (protan) vision tests. These improvements were:
- ~16% for tritan contrast (eyes uncovered)
- ~9% for protan contrast (eyes uncovered)
- ~7% tritan contrast (even when eyes were fully shielded)
- The improvement happened without direct eye exposure. This showed that the light had a systemic effect, likely through something other than just stimulating the retina directly.
Vision improves because the retina is mitochondria-dense.
The authors suspected that exposure to sunlight increased ATP (energy) and mitochondrial function. The retina has one of the highest concentrations of mitochondria in the body, especially in photoreceptor cells (the rods and cones that detect light).
These cells need enormous amounts of energy to process signals and regenerate visual pigments.
- When ATP production improves systemically (even from light absorbed through the back or chest), it seems to indirectly support the retina:
- More ATP = better function and faster recovery of photoreceptors
- Less oxidative stress = lower inflammation and cell damage
- Improved pigment recycling = sharper color contrast and perception
This helps explain why vision improved 24 hours after light exposure, even when the eyes themselves weren’t exposed to the light.
850 nm near-infrared light can pass through the hand and is mostly absorbed by deoxygenated blood, which appears dark. That’s important because it means this type of light reaches deep into tissues and targets areas where oxygen is low, precisely where mitochondria are under stress.
By absorbing this light, mitochondria in low-oxygen zones can restore energy production, improving cell function. In the study, this likely helped energize cells systemically, including in the eyes, even though the light never touched them directly.
The authors emphasize that sunlight’s full spectrum, including longer wavelengths like near-infrared, is essential for healthy biological function.
Most modern indoor lighting, especially white LEDs, only emits a narrow band of light. mostly between 400–650 nm (blue to red), and lacks the longer infrared wavelengths (800+ nm) that penetrate the body and stimulate mitochondrial energy production.
The concern is that by spending most of our time indoors under artificial lighting, were missing out on wavelengths that support energy metabolism, tissue repair, and vision. Over time, this absence of beneficial light could contribute to chronic fatigue, slower healing, or even age-related disease.
Artificial light isn’t enough, our biology evolved with full-spectrum sunlight, and leaving out parts of that spectrum could be harming us.
