Blue light blocking glasses: how do they work?

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In recent years, fashionable eyewear stores have found a way to expand their customer base beyond people with defective vision by stocking so-called “screen glasses”. At some major retailers, mixed with classic glasses, you will find blue light blocking lenses. And as our use of digital devices has peaked during the pandemic, interest in these products has increased.

Blue light blocking glasses look like regular glasses, but instead of wearing a corrective lens, they have a filter that specifically targets the blue light emitted by digital screens. They claim to relieve eye fatigue, improve sleep and reduce the risk of eye disease.

There are now dozens of brands, some of which are promoted on social media by influencers and major celebrities, with some high-end pairs costing nearly $200.

So, do you really have to worry about blue light? And do these glasses help?

Credit: Artwork: Jo Gay

What is blue light?

Light is a form of radiation made up of a range of different wavelengths, each a different color, says Andrew Anderson, associate professor of optometry at the University of Melbourne. When white light enters a prism, it breaks up into the colors of the rainbow, including, of course, blue. This spectrum ranges from short to long wavelengths, with blue being the shortest and red the longest.

The reason blue light gets a bad rap is because shorter wavelengths have higher energy and are therefore more likely to be dangerous, Anderson says. But that’s only at extremely high intensities.

“Blue light from a computer screen has nothing to do with the kinds of intensities required for it to cause damage,” he says.

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Why do people buy blue light blocking glasses?

Ever since we started glueing ourselves to screens, people have been complaining about digital eye strain (also known as computer vision syndrome). Dry eyes, blurred vision, eyestrain, headaches and neck tension are all symptoms. The more people use their devices, the more likely they are to experience this discomfort.

“Our eyes weren’t really designed with this task in mind, they’re designed to look far away and, sometimes, look up close,” says Luke Arundel, clinical director of Optometry Australia. “There has absolutely been an increase in eye strain during the pandemic.”

But even before COVID-19, blue light glasses were popular. Anderson published a study in 2019 of 400 Australian optometrists. He found that glasses with blue light blockers accounted for about a third of all eyeglasses prescribed the previous year, due to high device usage and patient demand.

Specsavers optometrist Karen Walsh noted a “massive increase”, especially over the past year, in the number of people learning about blue light filters. Specsavers does not promote them but can arrange for them to be applied if a patient insists, although Walsh says his busy Perth clinic has only sold them twice.

“Trying to dispel the myths [about blue-light blockers] is 10% of my day, every day,” says Walsh. “The last thing we want is for people to waste their money. Unfortunately, a lot of marketing takes hold of people’s anxiety about how much time they spend in front of digital devices.

What are the myths?

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Basically, this blue light causes eye strain or worse – permanent eye damage.

As for eye strain, Arundel says the theory is that blue light scatters in the eye and increases the effort needed to maintain visual focus. “There are, however, many components that contribute to digital eye strain,” he says, and there is currently “no high-level evidence to support wearing blue-light blocking glasses.”

Anderson’s own findings from a randomized controlled trial, published in February 2021, found no difference in symptoms between participants wearing blue light filters and those wearing clear lenses.

Anderson says researchers are working to determine what causes eye strain. Blue light aside, even overall screen light probably won’t be an issue. Scientists now believe it has more to do with human behavior and the way we use our digital devices, rather than an inherent characteristic of screens. For example, when you’re staring at a screen, your blink rate drops about five times slower than usual, so your eyes are more likely to feel dry and tired.

Also, says Anderson, fixing your gaze at a short distance for long periods of time can then make it difficult for your muscles to relax to adjust your focus over greater distances, making things further away blurry. Looking at a computer screen also exposes the eyes more, which can contribute to dryness. Then there is poor positioning of a screen, which can cause visual discomfort, for example with glare from a window behind you.

When it comes to eye damage, Anderson says the scientific evidence categorically shows blue light from screens isn’t the culprit. Animal studies conducted in the laboratory have shown that very intense exposure to high levels of blue light over an extended period of time causes retinal damage, but Anderson says these levels are not even close to the levels we would normally encounter.

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The problem isn’t that the type of blue light from a computer screen is different, Anderson says, but that it’s just not intense enough to pose a risk of eye damage. Similarly, we receive the same type of ultraviolet radiation when the weather’s ultraviolet index is “extreme” or “weak” – it’s just that there’s a lot more of it during the latter.

In fact, the most powerful source of blue light we are exposed to day-to-day is the sun, says Arundel.

“I would like to reassure people that we don’t burn our eyes with blue light staring at screens all day,” says Arundel. “The intensity of [blue light] to walk outside, even on cloudy days, is orders of magnitude greater than that emitted by digital screens.

Wearing sunglasses is important: they protect against ultraviolet light, which is a much bigger problem.

The only potential benefit of blue light filters is a possible placebo effect, says Arundel. “It’s really difficult because some patients swear by it, say it’s changed their life. But this is anecdotal evidence,” he says.

There are reasons why staring at a screen can cause eye discomfort, but there is no evidence that this is due to the blue light emitted.

There are reasons why staring at a screen can cause eye discomfort, but there is no evidence that this is due to the blue light emitted.Credit:Dimitri Vervitsiotis

Does blue light affect sleep?

Blue light plays an important role in influencing our circadian rhythm. We have photoreceptors in our eyes that are sensitive to blue light, says Sean Cain, associate professor at Monash University and spokesperson for the Australasian Sleep Association. When these receptors pick up blue light, they signal to our brain that it is daytime and suppress the production of melatonin, the sleep hormone.

This means that during the day the blue light around us helps us stay alert, but at night the scrolling on our phones can make it harder to fall asleep.

Most blue-light blocking glasses have mostly clear lenses, and Cain says they’re ineffective at improving sleep. But wearing more intense blue light blockers, which have an amber tint, can be helpful if worn before bedtime (wearing them during the day can affect your body clock).

Alternatively, Cain says, turn down the screen brightness on your devices at night and dim your house lights, and use warmer bulbs.

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What can you do to avoid eye strain?

There’s no magic bullet, but there are sensible steps people can take to alleviate the symptoms of digital eye strain.

  • See an optometrist for a comprehensive eye exam if you suffer from digital eye strain, says Luke Arundel. They’ll look for common problems, such as dry eye syndrome, uncorrected refractive error (requiring prescription lenses), or binocular vision problems (problems with how the eyes work as a team).
  • Follow the 20:20:20 rule when using devices. Every 20 minutes, pause for 20 seconds to look at something 20 feet (six meters) away. This shifts focus from your eyes and helps relax the muscles. Consider using an app to set reminders, suggests Arundel.
  • Whether it’s because you blink less or have dry eye syndrome, your eyes may be dehydrated, says Karen Walsh. She recommends using eye drops. And consciously practice blinking, says Walsh. Do it slowly and completely close your eyes. “It replenishes the tears in front of your cornea. Many people don’t completely close their eyes when they blink without thinking.

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