"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, A. R., & Roberts, J. E. (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. 

Displays and sleep

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.

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.


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.