Blue light and sleep
Sean Cain, sleep researcher and associate professor of psychology at Monash University, says increased Australian exposure to artificial blue light is a "health problem".
Exposure to blue light before bedtime can affect our ability to sleep in three ways: suppressing melatonin in our body that helps us sleep, increasing vigilance and affecting our body's internal clock (or circadian rhythm).
"Though it can be 23 hours, you give a signal to the clock that it's a few hours earlier, and then it's harder to sleep," explains Professor Cain.
There is also evidence that exposure to blue light can affect sleep quality throughout the night: studies conducted by Swiss researchers in 2013 have found that exposure to blue light even at relatively low levels (ie, sitting in a room lit with a standard LED bulb) can reduce the amount of sleep in slow waves (most often the restorative type of sleep) that a person has earlier during the night.
Because the problem is not just in the phone. Though people are exposed to less blue light every day than to get them from the sun as we lived mostly in the outdoor lifestyle a few centuries ago, our exposure is now happening through artificial sources in unnatural times, especially lighting the space when sun sets.
"Most Australians have a lot of blue light in their environment because of the decision to switch to more energy-efficient LED diodes," says Associate Professor Cain.
"It's good for saving energy, but it has replaced the light that has less impact on our indoor clock. Now we have these LED diodes, which are very rich in blue, and we have them in our homes up to bed."
Can blue light damage your eyes?
A short answer to this question is yes, but probably not at the levels at which you are exposed.
Many marketing information on blue light targets focus on screen usage throughout the day – Bailey Nelson's website maintains that their filter "helps reduce eye strain and fatigue caused by displays and devices," while the Wylee Oscar lens blue lights "for those who spend days in front of the computer screen – and how it can allegedly lead to eye strain.
However, Melbourne optometrist and Optometry Australia spokeswoman Sophie Koh says that more evidence is needed if exposure to blue light causes particular strain on the eyes, resulting from "limited, minor studies and anecdotal evidence".
"Research is under way in this area and there are many other components that contribute to digital eye strain or" computer vision syndrome, "she says.
As far as serious eye problems are concerned, it is unlikely that this can be caused by your smart habit.
According to a report by the New Zealand governmental organization Royal Society Te Apārangi in 2018, although retention of retina may occur after exposure to high intensity blue light, this would require a blue light level far greater than that emitted by the LED display.
With these proofs, Koh says "at this stage … we do not have to worry about computers or phones" that trick our retina. "
"Recent research has shown that even in extreme conditions, blue light exposure levels on computer displays and mobile devices are smaller than those that are absorbed by natural daylight, which is below international security constraints," she says.
Blue light glasses: are they worth investing?
If you are concerned that your eyes will be lighted throughout the day, Koh recommends that you seek advice from the optometrist to rule out common vision problems such as defective refractive errors (prescribable) or dry eye.
There are other measures, such as the 20-20-20 rule – every 20 minutes to watch the screen and at least 20 feet (six feet) in the distance for 20 seconds – or with applications like F.lux or Apple Night Shift for filtering blue light on a smartphone, which can be useful.
But if you mostly want to improve sleep quality, Associate Professor Cain says he would "strongly support" someone who in the evening wears blue light on the filter cups, especially by putting the glasses at the same time each night to encourage the body to develop a proper circadian rhythm.
However, he would warn of wearing bright blue glasses throughout the day, as this could "potentially" affect the vigilance.
"It is not directly tested, but we know blue light is alerted throughout the day so exposure to a lot of blue light during the day can be pretty good, not just for warning, but [also] giving your body a strong signal that it's a day, he says.
"If you block it, you are in a situation where there is not enough signal for your watch to differentiate between day and night. I think it would be a terrible idea to carry these things at all times of the day."
And, if you want to buy blue light glasses so you can write in the early hours, keep dreaming: in the end, no special pair of glasses will win by putting your phone away before you go to bed.
"Obviously, if you use devices in a way that makes you more active – if you look at a work email or worry about the next day – it will be harder to fall asleep."
Mary Ward is the deputy editor of The Sydney Morning Herald and The Age.