What is blue light?
Sunlight is made up of the full spectrum of visible light as a combination of red, orange, yellow, green, blue, indigo and violet light. All the colors of a rainbow are present is sun light, which you can see in prisms. Each of the colors has a different wavelength: light rays on the redder end have longer wavelengths and less energy, whereas on the blue end, rays present shorter wavelengths and more energy.
Whiter looking light contains a larger amount of blue component, which means it can expose the eye cells to a higher amount of wavelength from the blue spectrum.
The main source of blue light is our sunlight, but there are many other sources:
Fluorescent light & CFL (compact fluorescent light) bulbs
Flat screen LED televisions
Computer monitors, smart phones, and tablet screens
Sun exposure is necessary and good for your health. And even though the amount of blue light exposure you receive from screens is smaller than the exposure you get from the sun, there is evidence that long-term effects of screen exposure is harmful.
The danger comes from the proximity of the screens, and the amount of time spent looking at devices, even more so for children.
According to a recent study, children’s eyes absorb more blue light than adults from digital device screens.
Each color of light has a different effect. Blue wavelengths is beneficial during the day because it increases attention, fastens reaction times, and improves mood, but it is also the most disruptive after sundown. The multiplication of devices with screens, as well as energy-efficient lighting, increases our exposure to blue wavelengths and brings about a dangerous dark-side for our health.
Light and sleep
Your circadian rhythm is the internal clock that controls your sleep/wake cycle, and is highly dependent on sunlight. At sundown, your body naturally releases a hormone called melatonin, which tells your body it is time to get ready for sleep.
While light of any wavelength can suppress the secretion of melatonin, blue light at night does so more dramatically.
Researchers at Harvard led 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).
Blue light exposure and eye disorders
Age related macular degeneration (AMD, ARMD)
Some studies have shown that blue light can accelerate ARMD occurrence and its development after cataract surgery that occurred many years previously. The adverse effects of blue light exposure include oxidative stress in the cells of the eye, retinal blood vessel damage and cone cell death, retinal degeneration and morphological changes.
A study on rabbits showed that damage to the retina can occur after only 24 hours of blue light exposure.
Sunlight exposure has always been considered to be a risk factor for cataracts, because of blue-light wavelength. Now with the proliferation of screens, the input is higher and higher. Studies have shown that blue light can induce the production of ROS in the mitochondria of lens epithelial cells (hLECs), which may lead to the development of cataracts.
Near sightedness in children
A survey of the impact of screen reading on schoolchildren's visual acuity was recently conducted, and results showed that screen reading can lead to the occurrence and development of poor eyesight.
The conclusion was that the longer the screen time reading is, the higher the incidence of nearsightedness .
Blue light exposure and aging
Prolonged exposure to blue light, such as that which emanates from your devices, could be affecting your longevity, even if it's not shining directly into your eyes. A study was conducted on flies that do not grow eyes, and the ones exposed to blue-light wavelength showed neuron damage that impaired their ability to move normally.
How to protect yourself from blue light at night
Use dim red lights for night lights. Red light is the least likely to disrupt circadian rhythm and suppress melatonin production.
Avoid devices and bright screens two to three hours before bed.
Consider wearing blue-blocking glasses, and installing a night-shift app that filters the blue/green wavelength at night.
Expose yourself to lots of natural sunlight during the day, which will boost your ability to sleep at night, as well as your mood and alertness during daylight.
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Trevor R. Nash, Eileen S. Chow, Alexander D. Law, Samuel D. Fu, Elzbieta Fuszara, Aleksandra Bilska, Piotr Bebas, Doris Kretzschmar & Jadwiga M. Giebultowicz. Daily blue-light exposure shortens lifespan and causes brain neurodegeneration in Drosophila. npj Aging and Mechanisms of Disease, 2019 DOI: 10.1038/s41514-019-0038-6