"Blue light" and its impact

In general terms, blue light is a stressor: on the positive side, it wakes us up and prepares us for the activities of the day; on the negative side, it can deplete our reserves and cause harm, or simply keep us awake and reduce the efficiency of sleep and recovery.

In natural light, blue light stress is always balanced by the presence of red and near-infrared (long-wavelength) light, which generally has the opposite effect. In modern electric lighting, blue light is frequently present in disproportionate quantities, at the wrong time of the day, and without any of the long wavelengths to counterbalance its physiological ramifications. Therefore, comparing blue light exposure in isolation from its context is not appropriate. In other words, blue light from sunlight cannot be directly compared to the same amount of blue light exposure from indoor electric light.

Note: the term "blue light" is somewhat imprecise, since color is a perceptual interpretation, not a property of light itself. Therefore, the term short-wavelength visible light (the short end of the spectrum is violet and blue light) is often used instead.

Blue light as a stressor

Mechanisms of photochemical harm and why (at least one reason, why... aside from the lack of long wavelengths) electric light supplementation against seasonal affective disorder can be harmful:

Wielgus & Roberts (2012) Retinal photodamage by endogenous and xenobiotic agents. Photochemistry and Photobiology, 88.

Photodamage by blue LED light causes mitochondrial dynamics deregulation in the retinal pigment epithelium (which supplies nutrients to and cleans up waste from the retina), with potential contribution to age-related macular degeneration:

Alaimo et al. (2019) Toxicity of blue led light and A2E is associated to mitochondrial dynamics impairment in ARPE-19 cells: implications for age-related macular degeneration. Archives of Toxicology, 93. 

The mainstream in displays, after decades of denial, is finally starting to acknowledge some of the health problems with blue light from screens. Their proposed mitigation measures are still band-aids at best, as they do not take into account the interactive nature of the physiological effects of various frequencies:

Harris et al. (2023) Reducing Blue Light Toxicity with Quantum‐Dot Technology. Information Display, 39.

The "blue spike" in the spectral emission of regular white (phosphor converted) LEDs does contribute to excess retinal cell damage relative to blue-free LEDs:

Jin et al. (2021) The effects of low-color-temperature dual-primary-color light-emitting diodes on three kinds of retinal cells. Journal of Photochemistry and Photobiology B: Biology, 214.

Displays and sleep

Blue light from displays in the last hour of the day: reduced melatonin secretion and evening sleepiness, later timing of the circadian clock, and reduced alertness the next morning:

Chang et al. (2015) Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 112.

These effects are mainly melanopsin-dependent (at a given illumination level, the proportion of power in the blue-green part of the spectrum matters the most, regarding sleep):

Schöllhorn et al. (2023) Melanopic irradiance defines the impact of evening display light on sleep latency, melatonin and alertness. Communications Biology, 6.

Circadian effects of blue light are most pronounced at the center of the visual field (projected to the macula of the retina). Therefore, computer displays are the most efficient lighting application to achieve such effects (for good or for bad):

Nagare, Rea, & Figueiro (2021) Spatial sensitivity of human circadian response: Melatonin suppression from on-axis and off-axis light exposures. Neurobiology of Sleep and Circadian Rhythms, 11.

A short summary of some of the negative effects of display use on youth by the French National Academy of Medicine:

Académie Nationale de Médicine (2023) Eye and brain of children and adolescents under the light of screens. Press release.

Negative health consequences of screen time cost $151 billion to the US health system in 2023. The proposed solution in this report is more frequent visits to a doctor. What if we could instead eliminate the cause of the problem?


Displays and eye strain

A key mechanism through which flicker disrupts eye movement planning and thus decreases work performance:

Schweitzer & Rolfs (2021) Intrasaccadic motion streaks jump-start gaze correction. Science Advances, 7.

The worse the flicker, the greater the resulting negative effect on cognitive performance, arousal, and associated brain and pupil functioning:

Veitch et al. (2023) Effects of Temporal Light Modulation on Cognitive Performance, Eye Movements, and Brain Function. LEUKOS.

Great collection and discussion of negative health effects of flicker (these sources also concern with software-based causes of flicker, which are beyond the scope of the display itself; however, all issues with flicker from the backlight can be solved by a continuous backlight source, as in Pixun):





While the exact contribution of various mechanisms is an open question, time spent outdoors helps prevent short-sightedness:

Xiong et al. (2017) Time spent in outdoor activities in relation to myopia prevention and control: a meta‐analysis and systematic review. Acta Ophthalmologica, 95.

Even broader spectrum LED helps with myopia (while, for many reasons as shown here with other studies, it certainly cannot compete with natural light):

Muralidharan et al. (2022) Recovery From Form-Deprivation Myopia in Chicks Is Dependent Upon the Fullness and Correlated Color Temperature of the Light Spectrum. Investigative Ophthalmology & Visual Science, 63.