Should you forget what you’ve heard about blue light?

It’s been linked to everything from disturbed sleep to eye strain and even retinal damage, but is the blue light emitted by electronic devices really so bad?

The connection between screens and blue light has been so widely discussed that you might think it’s a type of light that’s unique to your phone, tablet or computer screen.

But the screen in your bag or back pocket isn’t the biggest source of blue light you encounter every day. Sunlight is – by far. Other sources include florescent and LED lights.

So why all the fuss about screen-related exposure to blue light?

Part of the answer is a 2014 study that found that while reading a book before bed has zero impact on the production of the sleep-promoting hormone melatonin, looking at screens like tablets, which mostly emit blue light, does.

Pre-bed tablet users enjoyed less restorative REM sleep and felt sleepier the morning after.

But a study published in late 2019 debates that, saying blue light may be less disruptive to sleep than originally thought – and that white or yellow light is actually worse.

So, does blue light disrupt sleep or not?

The answer is still “yes”, depending on the timing.

While daytime exposure to blue light is important for a healthy sleep-wake cycle, research continues to show that exposure too late at night disrupts sleep.

As for the 2019 study that suggests otherwise, that was performed using mice, which experts say casts doubt.

But pre-bed exposure to blue light isn’t the only reason screens disrupt sleep.

“There may be other factors such as overstimulation causing increased alertness,” says Dr Jane Khan, chair of the Royal Australian and New Zealand College of Ophthalmologists’ public health committee.

In fact, Australia’s Sleep Health Foundation says not only are “interactive” devices like phones more likely to affect sleep than “passive” devices like e-readers, simply the fact that devices distract us into staying up late is another contributing factor.

What about eye strain and retinal damage?

RANZCO’s official view is that there’s currently no evidence to suggest that normal environmental exposure to blue light, including from digital screens, damages eyesight.

It’s a similar story for eye strain.

“Blue light from screens doesn’t really play a role because it’s such a small amount of light,” says Dr Khan.

“The main things that contribute to eye strain associated with screens are poor focus due to either incorrect or a lack of prescription glasses, ocular dryness, fatigue and poor ergonomic positioning.”

Are blue-light filtering glasses a good investment?

A new study may have added weight to their worth.

“We found that wearing blue-light-filtering glasses is an effective intervention to improve sleep,” says study author assistant professor Cristiano Guarana, of Indiana University.

Study participants who wore them before bedtime enjoyed longer, better-quality sleep and performed better at work the next day, too.

“The effects of wearing blue-light filtering glasses were stronger for ‘night owls’ than for ‘morning larks’,” says Prof Guarana.

“Although most of us can benefit from reducing our exposure to blue light, owl employees seem to benefit more because they encounter greater misalignments between their internal clock and the externally controlled work time.”

But according to RANZCO not only is there no evidence that blue-light blocking glasses improve visual performance or conserve general eye health, avoiding all blue light may not be healthy, including for sleep.

Even Prof Guarana’s study only involved wearing the light-filtering glasses for two hours before bed, not all day.

How to protect your eyes when using screens

“Taking regular breaks, wearing the correct prescription glasses, practising good ergonomic positioning, avoiding direct flow from air conditioning and using ocular lubricants if your eyes feel dry can help avoid eye strain associated with screen use,” Dr Khan says.

“And while there’s no exact set of rules around screen use at night, it’s recommended to avoid them for a couple of hours before bedtime.”

Written by Karen Fittall.