It comes from the sky, light bulbs, LEDs and screens (tablets, computers, smartphones …). All return that blue light which is part of the visible spectrum. “In broad daylight or in cold white LED lighting, this represents a third of the total visible light received by the eye, explains Coralie Barrau, physicist, photobiologist and Essilor R&D engineer. Blue daylight resets our biological clock, rhythms our sleep / wake cycles and our metabolic functions. In addition, it acts on the mood, with an obvious anti-stress effect. A beautiful blue sky and we already feel better, so a real positive! “
Negative effects on our eyes
Daily exposure to blue-violet light, even at low intensities, helps accelerate retinal aging. It promotes oxidative stress and decreases antioxidant defenses. It is an identified risk factor for Macular degeneration (AMD). A meta-analysis, a compilation of numerous works, published in 2012 in the British Journal of Ophthalmology, indeed shows a certain link between exposure to sunlight (including blue light represents one third of the spectrum) and the risk of developing AMD. Screens and artificial lights also emit blue light, especially at a time when we are no longer supposed to receive it: at dusk and at night. Suddenly, the sleep cycle is disrupted by this false “daylight” message sent to the brain.
Accelerated aging of the skin
“Visible light, including blue, has been shown to stimulate enzymes, metalloproteinases, indicates Pr Passeron, dermatologist at CHU Nice and researcher at Inserm. These will degrade the cell matrix and, ultimately, increase skin aging. On the other hand, being glued to your screen, unlike what you can read on the internet, does not accelerate aging or the appearance of unsightly spots or pigmentation. “
By comparison, an hour and a half to two hours of sunlight provides what would be required for screens placed 30 cm from the skin for a week at a rate of five to seven hours per day. “However, our team has shown that blue daylight has an aggravating effect on melasma (pregnancy mask) and in post-inflammatory hyperpigmentation problems (after surgery or a burn, for example). And another team has just proven its action on brown spots. “
Consequences on the metabolism
In 2016, researchers at Northwestern University (United States) showed that blue light promotes insulin resistance, weight gain and diabetes. To do this, they enriched light in blue and studied its impact on the glucose and insulin levels of two test groups. The first received the enriched light half an hour after waking up followed by breakfast; the second, at the end of the afternoon, followed by dinner. In the latter group, the researchers observed unusual spikes in glucose, demonstrating a difficulty for insulin to regulate blood sugar levels after a meal. Conclusion: in the evening, blue light impacts the metabolism, so we should limit the sources so as not to see an increase his risk of diabetes or obesity!
How to preserve it?
• As a precaution, outside and inside, it is advisable to fit the lenses of your glasses with blue-violet light filters, just as they have UV protection. “The protective effect of Crizal Prevencia and Eye Protect System filters is measured in vitro on retinal cells exposed to polychromatic light reproducing that of day”, confirms Coralie Barrau.
• For home lighting, opt for warm white LEDs (yellow white), which have less blue. Locate the four digits on the packaging followed by a K (color temperature, Kelvins) and choose the lowest (from 2700 to 3500 K), knowing that the scale goes up to 6500 K, or even more (white cold).
• Television does not present any particular risk if viewed from a distance, except for children, especially at night. Even a weak emission of blue, especially from computer screens, tablets and smartphones, is enough to impact the production of melatonin, the sleep hormone.
Ideally, screens should be avoided two hours before falling asleep and at least one hour before.
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Led bulbs, dangerous for the retina
Blue light helps to heal better
