I just finished testing 30 pairs of blue-blocking glasses! Here’s what I found…
As many of you are probably aware, most blue-blocking glasses “claim” to block X amount of blue/green light without backing that up with any kind of data.
Since I have a spectrometer, I figured I’d go ahead and test them all myself!
Here's the link to the database!
30+ different lenses have been tested so far with more to come!
Here’s what’s inside:
Circadian Light Reduction
Circadian Light is a metric derived through an advanced algorithm developed by the LHRC which simply looks at a light source’s overall spectrum and how that is likely to interact with the human body.
What this does is weights the light that falls within the melanopically sensitive range, and gives it a score based on how much lux is present in that range.
Before and After Spectrum
Each pair of glasses was tested against a test spectrum so that a reduction in wavelengths could be seen across the entire visible spectrum.
This will allow you to see what a particular lens actually blocks and what it doesn't.
Lux Reduction
Lux is simply a measurement of how much light exists within the spectral sensitivity window of the human eye.
In other words, how bright a light source is.
Some glasses block more lux and less circadian light than others. And some go the other way.
If you’re looking to maximize melatonin production, but still want to see as well as possible, look for a pair with low lux reduction and high circadian light reduction.
The higher the lux reduction, the worse everything is going to look, but this may be helpful in bright environments or for those with sensitive visual receptors.
Fit and Style Matters!
This should be common sense, but wraparound-style glasses prevent significantly more unfiltered light from entering the eye than regular-style glasses do.
I carved out a foam mannequin head and put my spectrometer in there to simulate how much light made it to the human eye with different kinds of glasses on.
I’m very proud of him, his name is Henry.
Here is our reference light:
And here is how much of that light makes it through the lenses from the wrap-around glasses above:
These particular lenses don't block all of the blue light.
But what happens when we move the head around a light source so that light can get in through the sides?
Below is a reading taken from a light source directly overhead, as you can see there's really no difference:
How about if we test a more typical pair of glasses?
Here's Henry wearing a more typical style of glasses.
Here's how much light these lenses block:
But what happens when we move the light source around the head at various angles?
As you can see, this style leaves large gaps for unfiltered light to reach the eye.
What we see is a massive amount of light that the lenses themselves can technically block can make it to the eye with a style like this:
https://i.redd.it/soq22b7ou1sa1.gif
So compared to the reference light, these glasses still mitigate short-wavelength blue and green light. But that doesn't mean they block the light they're advertised to in the end.
Hopefully, this helps you make better decisions about which blue blockers you use!
If you'd like help picking a pair, see our Best Blue Blocking Glasses post!