Blue light blockers

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Artificial light can suppress melatonin and delay your circadian clock. Even electronic screen lighting like that of an e-reader can do this. This is because LEDs and fluorescent tubes emit a lot of blue, short-wave light, to which our circadian system is most sensitive. At very high irradiance, blue light can even be harmful to the eye. Blue-light-blocking glasses promise to filter out these wavelengths of light. But do they really help? Let’s take a look at the scientific evidence and then at available options.

Influence on the circadian system and sleep

From a theoretical point of view, it makes sense to filter out blue rays around a wavelength of 480 nm, as they have the greatest impact on your circadian system. Usually, blue light blockers do not reduce their intensity to zero. Depending on the color of the lenses, they mildly to strongly dampen blue light intensity.

Lens color matters – go for amber or red

Transparent + blue shimmer: not effective

In 2017, Leung et al studied five representative pairs of transparent lenses with a “blue-light-blocking” blue shimmer. Those kinds of lenses are currently getting popular as an upsale for regular optical lenses. The researchers found that their filtering reduced the relative circadian efficiency of incoming light by 5.8-15%. This is far from an elimination of these wavelengths. In their study, no significant effect on sleep quality was observed when subjects wore the glasses for at least 2 hours a day for a month.

Amber or red: promising!

A study by Shechter et al with 14 participants suffering from insomnia symptoms did show a significant improvement in total sleep time (+52 minutes/night by subjective assessment, +29 minutes/night measured by actigraphy) as well as sleep quality when amber-tinted lenses were worn for one week in the last 2 hours before bedtime. According to the manufacturer, the lenses blocked 65% of incident blue light. Unfortunately, no specific study of the lenses was conducted in relation to circadian efficiency. An earlier study by Burkhart et al also found a significant improvement in sleep quality in 20 subjects with insomnia who wore amber lenses 3 hours before bedtime, compared to a control group.

Yellow: a suboptimal trade-off

The downside of amber or red lenses is that you see everything with a strong orange or red tint. Yellow lenses reduce around 95% of blue light but still allow for a comparably good color rendering – this may increase your enjoyment of food or movies. Sounds good?
Unfortunately, your circadian sensitivity encompasses a spectrum around blue light, not just blue light. In yellow lenses, the level of circadian reduction likely lies around 75%, which is not too much. Consider that light intensity follows a logarithmic scale: What appears as twice as bright may actually be 10 times as bright. Therefore, a reduction of 75% is not that much.

Hint: If you want to get a feel for the spectral changes with respect to the tint of the lens, you can find a really cool (US-based) database on blue-light blockers with spectogram measurements on OptimizeYourBiology.com/blue-blocker-database

What blue-light blockers to buy?

Apart from theoretical efficacy, the effective product is the one that you regularly use. To get your best pair of blue-light-blocking glasses, consider the following factors. :

• Spectrum & Color: See the section “Lens color matters” above. Consider what level of color rendering your use case requires. Yellow lenses may be less efficient than amber, but if you would not wear amber lenses in the long run, yellow still wins. Personally, amber is the color I use.
• Style: When I bought my first pair of blue light blockers, all I cared about was blocking performance. After having got my pair, I had to realize that it just did not look great. I was embarrassed to wear it in the presence of other people – my theoretical blocking efficacy of 99% went down to zero in practice.
  Be fair with yourself: It is okay to want to look good! It will make your compliance much easier.

Recommended products:

EU market:

PRISMA Freiburg Pro99
My personal favorite. Solid circadian reduction, solid looks, okay price.
The company is advised by photobiologist Alexander Wunsch, who is known to be passionate about getting things right when it comes to blue-light blocking.
If you do not like the Freiburg frame, find other styles with Pro99 lenses – they are all fine.
There is a lens variant Lite95 that is yellow. I do not recommend it due to the far lower circadian light reduction.
Find the PRISMA Freiburg Pro99 glasses here: Link

LichtBlock
Slightly more expensive than PRISMA, but they offer dark amber lenses and a wide variety of styles. I have no personal experience with the product or the brand, but from what I can see, it appears to be a legitimate option.
Find the LightBlock shop here: Link

If you wanna go cheap, ask Google or visit your e-commerce platform of choice. If you find a pair that has dark amber or red lenses, it should be just fine!

US market:

For the US market, please find

• recommendations from clinicians on the website of the CET – Center for environmental Therapeutics
• recommendations from biohackers (they have tested A LOT of glasses, focus on theoretical efficacy rather than style) on OptimizeYourBiology.com

Eye protection: Little evidence

In recent years, blue light blockers have seen quite a bit of hype as they can supposedly protect against eye strain, cataracts, macular degeneration and more. They are also said to improve visual performance. Do these promises hold true? Lawrenson et al in their 2017 review of studies examining the positive effects of blue light-blocking lenses, conclude that there is “no high-quality clinical trial to support these claims”. When eye strain occurs after a prolonged time in front of electronic screens, the intensity of the screen is not enough to damage the eye. Rather, the cause of eye strain may be the lack of blinking and eye movement, which is independent of the wavelength of the screen light. The American Association of Ophthalmology does not recommend special glasses for computer use.

Conclusion

Reducing blue light at night will help you to be tired at night and not delay your circadian clock. If glasses are designed to effectively filter out blue light, they can help you do this when worn before bed, and therefore also contribute to better sleep.

Be aware, however, that these glasses do not outright eliminate the kind of light to which your circadian system is sensitive: Classic blue light blockers actually seem to filter out only a small percentage of these wavelengths. Unless the specifications are clearly stated by the manufacturer, the effect can be difficult to predict. In general, avoiding artificial evening light still seems to be a far better strategy than filtered exposure.

When it comes to eye health and visual performance, there is no reasonable scientific evidence that blue-light-blocking glasses are worth buying.