How harmful is blue light?

Blue light has a bad reputation. Manufacturers are taking advantage of this, addressing its negative effects. This can be seen in the product description of the Dell P2422H:

Naturally, the monitor has a corresponding spec meant to filter out large amounts of blue light. However, manufacturers won’t say how or why blue light is harmful.

Of course…

There’s disagreement among scientists about how and whether blue light is supposedly harmful (in German). Thus, some blame it for cellular damage to the retina. There are also scientists who believe that they contribute to the development of age-related macular degeneration, a type of retinal problem (in German).

The kicker: we don’t primarily absorb blue light from screens. It’s in the visible part of the electromagnetic spectrum. It’s also prevalent outside or from artificial light.

According to Professor em. Dr. rer. nat. Michael Bach of Freiburg University Hospital, «Light intensity when using electronic devices is much too low to cause retinal damage to the eyes.» For comparison: when the winter sky is overcast, the intensity in Central Europe is around 5000 lux, during summer up to 100,000 lux. A bright screen remains below 500 lux at a seating distance of 50 centimetres. Bach also says that blue light eye damage from sitting in front of a screen for hours shouldn’t be feared.

Are there upsides to blue light?

Blue light controls our internal clock. It vitalises, keeps you awake and suppresses the release of melatonin – a sleep hormone. On the one hand, this is positive, but it can also be bad late at night: if we’re exposed to a lot of blue light at night, it can disrupt our internal clock and lead to sleep disturbances. These, in turn, are harmful to our health. Rest is important. If our internal clock is off balance, there can be health consequences. This is where blue light filters can actually help us from unintentionally getting pumped up in the evening (in German).

Verdict: blue light isn’t «evil»

While general findings on outdoor blue light is still divided, scientists are at least certain regarding artificial blue light from displays and lamps: according to current research, it shouldn’t be harmful to the eyes. So on-screen filters won’t help protect your eyes.

Blue light filters, however, can help our internal clock. Blue light stimulates. In the evening, therefore, they’re quite useful in allowing us to rest and have a healthy sleep.