What is blue light and why is it bad?
What is Blue Light?
Blue light is visible light with a wavelength between 400 and 450 nanometers (nm). As the name suggests, this type of light is perceived as blue in color. However, blue light may be present even when light is perceived as white or another color. The largest source of blue light is sunlight. In addition, there are many other sources:
- Fluorescent light
- CFL (compact fluorescent light) bulbs
- LED light
- Flat screen LED televisions
- Computer monitors, smart phones, and tablet screens
Blue light is of concern because it has more energy per photon of light than other colours in the visible spectrum, i.e. green or red light. Blue light, at high enough doses, is therefore more likely to cause damage when absorbed by various cells in our body.
Blue Light and Sleep
While there is still a lot of debate surrounding the wide range of potential symptoms that could be linked to blue light, there is consensus that blue light has been linked to distorted circadian rhythm and thus trouble sleeping. While light of any kind can suppress the secretion of melatonin, blue light at night does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness. 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). However, there are mixed views on the long-term consequences of the blue-light on the ocular health, specifically its role in the development of myopia or age related macular degeneration (AMD).
The impact of blue light on eyesight and ocular health
Although in vitro laboratory studies show that blue light can damage photoreceptor cells and retinal pigment epithelial cells via a photochemical mechanism, there is no epidemiological evidence showing damage to human eyes from prolonged use of digital devices.
There are a few reasons for that. First, the modern devices’ intensity of blue light isn’t anything as strong as one coming from the sun or used in studies. And screens have generally been improving over time. Secondly, there simply hasn’t been enough long-term studies done particularly with humans on the impact of blue light.
As a result, some institutions don’t flag exposure to blue light as a health risk while others encourage people to take protective actions. For example, Dr Shelby Temple, PhD, Honorary Professor at Aston University, encourages optometrists not to wait for research that is not feasible before educating patients about risks for macular disease. He says “On their own, individual devices probably aren’t putting out high enough amounts of energy that they are going to cause immediate damage. But in the long-term, that’s more interesting. It’s not about the intensity; it’s about the exposure.” He makes a comparison to smoking and its relation to lung cancer, which wasn’t really paid attention to before 1964. “The evidence that was put forward by the surgeon general to link smoking to lung cancer then is the same type of evidence we have about blue light damage today. There has never been a double-blind placebo-controlled study in humans that proved smoking causes cancer, nor should there be. We will never have a placebo-controlled study in humans that proves blue light causes macular degeneration.”
So is the blue light emitted from screens harmful to our health?
The real answer to the question is we don’t know. However, we do believe when it comes to health, prevention is better than cure.
Disclaimer: No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.