Selling blue-light filter coatings is a big business, though.
by who?
"While light of any kind can suppress the secretion of melatonin, blue light at night does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness. The blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours)." https://www.health.harvard.edu/healthy-aging-and-longevity/b...
"Evening residential illumination possesses the capacity to impair sleep quality via the suppression of endogenous melatonin production, a process largely driven by short-wavelength (blue) light." https://www.nature.com/articles/s41598-025-29882-7
"Blue light waves come from fluorescent and LED lights and back-lit electronic screens on televisions, computers, tablets, and cell phones. Remember, exposure to these lighted screens during the sensitive period can make it difficult for you to fall asleep at night or can wake you up too early" https://www.cdc.gov/niosh/work-hour-training-for-nurses/long...
"Blue light had stronger suppression effects, particularly in younger participants and men. These results underscore blue light’s disruptive effects on circadian health and highlight red light as a less disruptive alternative for nighttime environments." https://pmc.ncbi.nlm.nih.gov/articles/PMC12113466/
"A systematic search of PubMed, Scopus, and Web of Science identified randomized controlled trials (RCTs) from 2010 to 2024. Eligible studies enrolled adults using BBGs before bedtime and reported actigraphy-derived outcomes. Random-effects meta-analysis was performed using the generic inverse variance method. The review was registered in PROSPERO (CRD420251034611).
Results
Three double-blind crossover RCTs (n = 49) were included. BBGs showed a non-significant reduction in SOL (MD = −4.86 min; 95% CI: −20.23 to 10.52; p = 0.54) and a non-significant increase in TST (MD = 8.75 min; 95% CI: −35.31 to 52.82; p = 0.70). No significant effects were found for SE (MD = −0.61; 95% CI: −7.58 to 6.35; p = 0.86) or WASO (MD = −1.47; 95% CI: −14.94 to 11.99; p = 0.83). Heterogeneity was low (I2 = 0%).
Conclusion
BBGs may provide small improvements in sleep, but current evidence from RCTs does not support significant effects. Larger, well-powered trials with standardized protocols are needed."
- Efficacy of blue-light blocking glasses on actigraphic sleep outcomes: a systematic review and meta-analysis of randomized controlled crossover trials - https://doi.org/10.3389/fneur.2025.1699303
The issue is intensity of light. These retinal projector lasers are not intense enough to damage your eye. A regular light at the same intensity as a powerful laser would damage your eyes just as much. It's just a lot harder to create a regular light that can reach that level of intensity.
First, what is the fail-safe in case the scanning mechanism fails? I.e. is the intensity safe if the beam becomes stationary? Or does it guarantee it goes dark when not properly scanning?
Second, what is the safe intensity limit for the brief visits to each target pixel area? As the scanned area increases, you need higher intensity to maintain the same visual brightness with a shorter exposure for any one spot. At some limit, is the pixel to area ratio too low and this intensity too great?
Third, does the optical path through the cornea and lens have any hot-spot where you have to also worry about peak flux with this projection technique?