Blue Light Blockers

Artificial light can suppress melatonin and delay your circadian clock. Even electronic screen illumination like that of an e-reader can do so.1 This is because LEDs and fluorescent lights emit a lot of blue short-wavelength light that our circadian system is the most sensitive to.2 At high irradiance, blue light can even be harmful for the eye.3 Wouldn’t it be better to use toned glasses to filter out those undesired wavelengths of light? This is the concept on which blue-light blocking glasses are based. But do they really help? Let’s take a look at the scientific evidence.

Influence on circadian system and sleep

From a theoretical point of view, it makes sense to filter out the blues around a wavelength of 480 nm, as they most affect the circadian system.2 However, blue-light blockers don’t reduce their intensity to zero but rather dampen them. In 2017, Leung et al.6 examined 5 representative pairs of blue-light blocking glasses and found that their filtering reduced the relative circadian efficiency of the incoming light by 5.8%-15%. This is far from an elimination of these wavelengths. No significant effect on sleep quality could be observed in their trial when subjects wore the glasses for a minimum of 2 hours a day for a month.6 Another study by Shechter et al.7 with 14 participants with insomnia symptoms suffering under insomnia did show a significant improvement in total sleep time (+52 minutes/night by subjective assessment, +29 minutes/night measured with actigraphy) as well as sleep quality when amber tinted lenses were worn in the last 2 hours before bedtime for a week. The lenses blocked 65% of the incoming blue light, according to the manufacturer. Unfortunately, no specific lens examination with regards to circadian efficiency was performed. A prior study by Burkhart et al.7 also found a significant improvement of sleep quality in 20 subjects with insomnia wearing amber lenses 3 hours before bedtime compared to a control.

Eye protection

Within the last couple of years, blue light blockers have experienced quite a hype with claims of them being able to protect you from eye-strain, cataract, macular degeneration and more. Furthermore, they supposedly improve visual performance. Do these promises hold true? In their 2017 review of trials investigating the beneficial effects of blue-light blocking spectacle lenses, Lawrenson et al.3 come to the conclusion that there is “no high quality clinical trial to support these claims”. When it comes to eye strain after time spent in front of electronic displays, the intensity of the screen is not enough to harm the eye.4 The cause of eye strain may rather be the lack of blinking and ocular movements that is independent of the screen light wavelength.3 The American Association of Ophtamology does not recommend special eyewear for computer use.5

Conclusion

Reducing blue light at night helps you be tired at night and not delay your circadian clock. If designed in a way that they effectively filter out blue light, glasses may help you to do so if worn before bedtime and, therefore, may help you sleep better, too. However, be aware that not all these glasses downright eliminate the type of light your circadian system is sensitive to: Many blue light blockers appear to actually filter out only a certain percentage of those wavelengths. Unless the specs are clearly stated by the manufacturer, the effect may be hard to predict. In general, avoidance of artificial evening light is still the recommended way to go. Effective blue light blockers can be helpful to filter out the rest or in situations where light exposure is outside your control.

When it comes to eye health and visual performance, we did not find reasonable scientific evidence that blue light blocking glasses are worth the purchase.

[1] Chang, A. M., Aeschbach, D., Duffy, J. F., & Czeisler, C. A. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences of the United States of America112(4), 1232–1237. https://doi.org/10.1073/pnas.1418490112

[2] Do, M. T. H., & Yau, K. W. (2010, October). Intrinsically photosensitive retinal ganglion cells. Physiological Reviews. American Physiological Society Bethesda, MD. https://doi.org/10.1152/physrev.00013.2010

[3] Lawrenson, J. G., Hull, C. C., & Downie, L. E. (2017, November 1). The effect of blue-light blocking spectacle lenses on visual performance, macular health and the sleep-wake cycle: a systematic review of the literature. Ophthalmic and Physiological Optics. Blackwell Publishing Ltd. https://doi.org/10.1111/opo.12406

[4] O’Hagan, J. B., Khazova, M., & Price, L. L. A. (2016). Low-energy light bulbs, computers, tablets and the blue light hazard. Eye (Basingstoke)30(2), 230–233. https://doi.org/10.1038/eye.2015.261

[5] Celia Vimont: Should You Be Worried About Blue Light? Available online at https://www.aao.org/eye-health/tips-prevention/should-you-be-worried-about-blue-light, checked on 2/11/2021.

[6] Leung, T. W., Li, R. W., & Kee, C. (2017). Blue-Light Filtering Spectacle Lenses: Optical and Clinical Performances. PLOS ONE12(1), e0169114. https://doi.org/10.1371/journal.pone.0169114

[7] Shechter, A., Kim, E. W., St-Onge, M. P., & Westwood, A. J. (2018). Blocking nocturnal blue light for insomnia: A randomized controlled trial. Journal of Psychiatric Research96, 196–202. https://doi.org/10.1016/j.jpsychires.2017.10.015

[8] Shechter, A., Kim, E. W., St-Onge, M. P., & Westwood, A. J. (2018). Blocking nocturnal blue light for insomnia: A randomized controlled trial. Journal of Psychiatric Research96, 196–202. https://doi.org/10.1016/j.jpsychires.2017.10.015