It's not the eyes you see with. It's the eyes that set your sleep.

Background

The chronobiology group at the University of Surrey had spent years studying how light affects the human circadian rhythm. In 2001 they designed an experiment specifically to map which wavelengths of light suppress melatonin, and through which photoreceptor system.

What the study looked at

They exposed participants to different wavelengths of monochromatic light during the night, measuring the changes in plasma melatonin. The goal was to build an action spectrum independent of Brainard's work — with no prior knowledge of his results — to see whether both groups would arrive at the same conclusions.

What they found

The sensitivity spectrum that Thapan et al. obtained confirmed Brainard's results independently: melatonin suppression peaks at around 460nm and falls off steadily toward the longer wavelengths. Red light in the 660nm range produces little to no suppression. On top of that, the sensitivity profile doesn't match any of the known visual photoreceptors — confirming that there is a photoreceptor system, separate from vision, that governs the body clock.

What this means for you

The effect of light on your baby's sleep isn't up for debate — it's physics. Two independent research groups, in two different countries, published identical results in the same year. Blue light suppresses melatonin through a system that has nothing to do with seeing. The deep red glow of the NeuroSafe™ Light doesn't switch that system on. So when you need to check on your little one at 3am, a single tap gives you enough light to see — without telling your baby's brain that the day has begun.

Study limitations

Like Brainard's study, this one was carried out in adults. The sample size is small. But the fact that two separate groups independently replicated the results in the same year is exactly what gives this finding such exceptional scientific weight.