With screens dominating much of our day-to-day lives, people are keen to know whether or not they have any effect on us – not just from the content we see, but from the light of the screen itself. Some are particularly concerned about the impact of blue light, with all sorts of accessories being peddled to us to combat its alleged effects. But does blue light actually have an impact on our health?

What is blue light?

Blue light is a color that’s part of the light spectrum visible to the human eye, occurring at wavelengths between 380 and 500 nanometers and making up around a third of the light that we can see.

Although many people will have heard of it in the context of digital devices, we actually get the vast majority of our exposure to blue light from the Sun – screens like computers and phones give us very little in comparison.

Two of the major ways that blue light is said to be potentially harmful is by damaging our eyes and preventing us from getting a good night's sleep. How much truth is there in these claims?

How might blue light affect our eyes?

“Blue light causes blindness”

One of the main studies that headlines have latched on to is a 2018 paper from researchers at the University of Toledo. “Blue light from phone screens accelerates blindness” was the headline of a Guardian article about the study, one of many – but that’s not what the research showed at all.

In this study, the team looked at how retinal, a light-absorbing compound found in the eye, responded to blue light exposure and found that there was damage to cell membranes in the cells tested.

But whilst retinal is present within the human eye, the results of the study can’t be applied to us. That’s because it didn’t mimic the conditions of an actual, live human eye; all but one of the cell lines that were tested were from other parts of the body, which aren’t exposed to blue light. Retinal also doesn’t touch the cell membrane in cells that are actually in human eyes.

Another study tested cells that are present within the retina, the part of the eye that senses light and converts it into electrical signals that are interpreted by the brain. The researchers found that two hours after blue light exposure, these cells had severe DNA damage, which had caused them to die.

There’s a catch, however – the study was carried out in rat cells. Not only does that mean the results can’t necessarily be translated to humans, but the research being conducted in vitro means it can’t even say that much about how living rats would respond either.

“Blue light causes eye strain”

If you’ve ever come across an advert for a pair of blue-light filtering glasses to put on when you’re using devices, you’ll likely have noticed claims that they can help to reduce eye strain – which implies that eye strain is caused by blue light. However, there’s no solid evidence to suggest this is the case.

A 2023 Cochrane review, for example, examined 17 clinical trials that compared the effects of blue-light filtering versus non-blue-light filtering lenses on eyes and found that the former “may not attenuate symptoms of eye strain with computer use, over a short‐term follow‐up period, compared to non‐blue‐light filtering lenses.”

What does appear to be the primary cause of eye strain after using digital devices, according to the American Academy of Ophthalmology, is not blinking enough when we’re using them.

How might blue light affect our sleep?

Chatter about blue light also often involves the effect that it might have on our sleep, often with the warning that we shouldn’t be using our devices so close to bedtime because of that. But how true are such claims?

It’s a bit of a mixed bag, primarily because the area needs a lot more research. A review of 36 studies found that half of them showed tiredness and sleep efficacy were decreased by blue light exposure, but the time it took to get to sleep and its quality and duration didn’t seem to be affected.

A study published at the end of last year exposed people to different types of light – dim blue, yellow, and white – and found that there was no conclusive evidence for differences between them in affecting sleepiness, actual sleep, or the body’s circadian rhythm (our sleep-wake cycle).

That being said, the study’s conditions weren’t exactly as they are in real life. 

“This study had specifically designed the light exposure…to avoid triggering the light-sensitive cell in our eye known to be responsible for resetting our circadian rhythm, which does not match real-world lighting environments,” Dr Alexander Solomon, a surgical neuro-ophthalmologist, who wasn’t involved with the study, told Healthline.

“This cell is sensitive to blue light, so saying blue light doesn’t play as much of a role is untrue. It’s simply saying a bright yellow light can affect things as much as a dim blue light.”

The bottom line

At present, the evidence for blue light being bad for us simply isn’t there, particularly when it comes to causing damage to our eyes. Its effect on our sleep might be marginally more contentious, but still, there’s not enough to support you needing to go off and spend a bunch of money on blue light glasses. 

If it feels like your devices are keeping you awake, there are a couple of much cheaper solutions – pop it in night mode (which is found on plenty of devices nowadays), or simply try to use them less before bed (easier said than done when there’s TikTok drama, we know).

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.  

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.