Blue lights: are they really harmful? Diagonale


Blue lights: are they really harmful?

Some lights, computer screens, television screens and cell phones are sources of blue light. With teleworking and on a daily basis, we are increasingly exposed to these sources of light. The question then arises for our health.

Blue light, what is it exactly?

Sunlight is made up of many rays of different wavelengths: red, orange, yellow, yellow, green, blue, violet.

The longer the wavelength, the less energy the ray contains. Blue rays have a short wavelength and therefore contain a lot of energy.

Blue lights fall into two categories:

  • Blue-turquoise: they are less intense and are essential to health (helps regulate sleep, treat seasonal depression, etc.).
  • Blue-violet: they contain more energy. They can increase visual fatigue associated with prolonged use of digital applications. In the long term, these lights can damage the eyes.



To know: UV (ultra-violet) rays are part of the blue-violet light spectrum. They are so powerful that they can modify the appearance of the skin (tanning, sunburn, burning, etc.).


What are the sources of blue light in our daily life?

The sun is the main and most intense source of blue light.

Artificial sources are:

  • fluorescent objects
  • LED devices: TV screens, cell phones, computers
  • low consumption light bulbs
  • Xenon headlights

All these objects sources of artificial blue light are less intense than the sun, but they are ubiquitous in everyday life.

It is the fact of staring at these objects for a long time that raises questions about their impact on our health.


What are the effects of blue lights?

First, blue light stimulates the production of vitamin D: essential for healthy bones, eyes and the immune system.

It also improves memory, cognitive function and mood. It is for this reason that it is used in light therapy to treat seasonal depression.

It helps regulate sleep because it interrupts the production of melatonin (sleep hormone). Exposure in the morning and during the day is therefore beneficial. For this same reason, it is not recommended to watch television or your cell phone before going to bed because this tells the body to stay awake. This can cause difficulty falling asleep.


According to a study conducted by Neurobiology of Disease, exposure to blue lights is beneficial for people with mild traumatic brain injury. A 30-minute exposure every morning allowed the patients in the study to have:

  • Better quality of sleep
  • Increased cognitive functions
  • Reduced sleepiness during the day
  • Accelerated healing


Finally the real answer to this question of the harmfulness of blue lights is: a little exposure at the right time of the day is positive.


To know: Being exposed for an hour outside during a cloudy day exposes our eyes up to 30 times more to blue light than spending an hour in front of a computer screen.


Common and misconceptions about blue lights

For the theories concerning retinal lesions, cataracts, AMD, lesions of the lens, it is especially a really very important exposure to blue lights which can be a risk, so prolonged exposure to the sun is problematic but much less exposure to screens.


Regarding AMD: the following risk factors are much more important than blue lights: age, smoking, cardiovascular disease, hypertension, overweight, etc.


Regarding the high risk of cataracts, this theory should be qualified.

The lens of the eye is able to filter the majority of blue light from the sun (be careful!! this is not always the case after cataract surgery). It is still important to wear sunglasses outdoors.

On the other hand, the lens does not filter the blue lights of the screens.


As for visual fatigue linked to blue lights, it is also to be qualified because you really have to spend a lot of time (all day) in front of the screens before feeling this effect of fatigue.

To limit this impact, don't forget to blink regularly and don't hesitate to respect the 20-20 20 rule: take a 20-second break, every 20 minutes, looking 20 feet away (about 6 meters).


How to reduce their impact?

There are filters that can be activated in the computer settings. It is also possible to add a blue light filter to your glasses lenses.

Also consider actions at source:

  • Warmer lighting tint (avoid white).
  • Limit time in front of screens and promote exposure in the morning or during the day.
  • Use electroluminescent bulbs with low blue light emission.
  • Adjust the brightness of your screens. The Lux software optimizes the adjustment of the luminosity according to the geographical position and the time in order to reproduce the natural solar cycle. Also the Philips Hue White & Color Ambiance bulbs adjust the brightness of the week.

The idea is being developed for luminous devices in bluish hues in cars to prevent fatigue at the wheel.


Finally, what is to be remembered is above all a moderation of the time spent in front of screens and adapting the moment to avoid exposure in the evening and before going to bed.