The wavelength matters.
460-480nm light suppresses melatonin. Our devices peak at 450nm. Understanding which light to block - and when - changes everything about sleep.
Blue light shifts your clock twice as much as green.
Harvard researchers found blue light suppressed melatonin for about twice as long as green light and shifted circadian rhythms by twice as much - 3 hours versus 1.5 hours.
Critical Wavelength Ranges
The melanopsin photopigment in our retinal cells has peak sensitivity at 460-480nm. A two-hour exposure to blue light (460nm) in the evening suppresses melatonin at light levels common in everyday environments.
Our devices peak at 450nm.
Research measuring actual device emissions found all electronic devices tested showed maximum emission between 440nm and 460nm - right in the danger zone for both eye strain and circadian disruption.
Smartphones
Peak emission around 450nm, producing 20-40 cd/m² at maximum brightness
LED Screens
Peak in the 435-440nm range - significant concern in medical research
Apple Devices
iPhone, iPad, MacBook Pro all show enhanced blue peaks at 445-455nm
Night Lights
Even 8 lux - twice a night light's brightness - can interfere with melatonin
Timing changes everything.
We want blue light exposure. Morning bright light including 480nm wavelengths helps regulate circadian rhythms and improves alertness.
Neutral zone. Blue light has minimal circadian impact. Normal screen use without significant disruption.
Critical blocking time. LED devices can suppress and delay melatonin even at relatively dim light levels (<30 lux). Switch to amber lenses blocking 65-99% in the 460-480nm range.
Specifications that actually matter.
Daytime Computer Glasses
Clear or lightly tinted. Block 35-45% of blue light for eye strain without affecting alertness.
- Swanwick Day Swannies: 98% at 400nm, graduating to 45% at 450nm
- Felix Gray: Claims 15x more filtering than other clear lenses
- GUNNAR clear lenses: 35% at 450nm
Evening/Night Glasses
Orange-amber tint. Block 65-99% in the 450-480nm range for melatonin protection.
- Swanwick Night Swannies: 99%+ from 400-500nm
- GUNNAR Amber Max: 98% at 450nm
- Uvex safety glasses: 98% blocking for ~$10
Budget tip: Start with affordable Uvex safety glasses (~$10) that block 98% of blue light with orange lenses to test effectiveness before investing in premium brands.
Practical recommendations.
Allow full blue light exposure. Use minimal filtering (20-35%) only if experiencing eye strain from computer work.
Optional clear blue light glasses blocking 35-45% if working extensively with screens.
Switch to amber lenses blocking 65-99% of blue light, especially in the 460-480nm range.
f.lux and Night Shift shift screen temperatures warmer. Reducing brightness to 50% cuts blue light proportionally.
Author's Note
I block all blue when indoors most of the time. But I'm always going outside without any glasses to allow whatever sunlight is available into my eyes and onto my skin.
I personally don't notice any difference between 100% blocking and 80% blocking. Sometimes when my eyes are sensitive, I wear the stronger ones, but I'm not sure it makes a difference.
Blocking blue is great and all, but altering lifestyle to get away from constant blue light is much more helpful.
Our circadian rhythm is programmable.
Morning light exposure, evening light blocking, and getting away from screens when possible. The science is clear - 460-480nm light after dark disrupts everything.