What does blue light do to your body?
Blue light inhibits the production of melatonin, the hormone that tells your body it's evening. If you're exposed to that light late in the day, your internal clock shifts, and it takes longer before you feel sleepy.
This happens unconsciously. You don't have to feel wide awake for it to have an effect, because the pathway that regulates this is separate from the cells responsible for sharp vision.
Which part of the light is responsible?
Mainly the range between 380 and 520 nanometers. Within that area, the peak is around 480 nanometers, precisely where the light-sensitive cells in your retina that control your biological clock are most sensitive.
The dark block marks the range that an evening lens tempers, roughly 380 to 520 nanometers.
Where that light comes from and why the sun is a much larger source than your phone, you can read in what is blue light and where does it come from.
Why does it work differently in the evening than during the day?
Because your body uses light as a time signal. During the day, bright light is useful: it resets your clock and keeps you alert. That same light in the evening gives the wrong signal at the wrong time.
| Time | What light does | What you want |
|---|---|---|
| Morning | Resets your clock, makes you alert | As much daylight as possible |
| Afternoon | Keeps you alert | No restriction needed |
| Last hours | Inhibits melatonin, delays sleep | Less light in the blue range |
Does this mean you should avoid screens?
No. It's about timing and quantity, not completely stopping. And light is only one of the factors, because what you do on that screen often outweighs the light itself.
Why your mind remains active after an evening of scrolling, even if the light is dimmed, is explained in why it's hard to fall asleep after screen use. And not everyone reacts equally strongly; we explain that difference in why not everyone reacts the same.
What can evening glasses do about this?
An evening lens tempers the range that inhibits your melatonin, without you having to put away your screen. It solves the light signal, not the mental stimuli of what you're watching.
Anyone who is still behind a screen in the last hour can remove the light component with our SLEEP. If you still find it hard to fall asleep afterward, the cause lies elsewhere and glasses are not your solution.
This article is intended as an explanation, not as medical advice. For persistent sleep problems, a general practitioner is the appropriate contact.
