The reason our screens may not be changing our biological clock, Foster explains, is that the level of blue light exposure from screens simply isn’t strong enough. For example, the light from an iPhone or Kindle is 10 to 30 lux (that is, lumens per square meter). The sun emits a whopping 80,000-100,000 lux. So isn’t it blue light that keeps us from sleeping, is it emails, Reels, games, TikTok? “Exactly,” he says. “The devices should not be worn for at least 30 minutes before bedtime, not because of the light but because of the alert activity the content creates in the brain.”
The impact on eye health
But how bad are our screens for actual eye health? I spoke to Professor Glen Jeffery, Professor of Neuroscience at the UCL Institute of Ophthalmology, who has recently done a lot of work (not yet published) on the impact of blue light on our eyes. “There are particular types of blue light,” he says, “present in expensive car lights, highway lights, and some high-end televisions, which can be particularly harmful to the eyes.”
He explains: “You have more mitochondria in your retina than any other part of the human body. They are like batteries, providing power to the cell, but absorbing blue light, which can cause them to turn off.” Jeffery’s colleagues at UCL have been carrying out studies on cell culture under blue light and can confirm that the cells are not happy there. “They don’t tend to divide well and some die easily,” he says.
He goes on to say that our screens and phones do not emit these dangerous levels of intense blue light. However, this is not to say that the low levels of blue light from our screens don’t have a cumulative effect on eye health over time: these devices haven’t been around long enough to allow for long-term studies.
And what about the dithering of light from our smartphones that some say causes headaches and eyestrain? Research published in the National Library of Medicine in 2017 shows that blue light glasses can help block this. However, it all depends on whether your blue light glasses actually contain the filter they claim to have.
Jeffery and his team have been testing lenses with a spectrometer to measure the light coming out the other side, and while some blocked blue light, many, he notes, did nothing at all and contained no filter at all. Therefore, if you are going to buy a pair, it is important that you choose a brand, such as Ocushield, which is FDA and MHRA approved and third party tested.
However, Jeffery tells me that within our retina we have a natural filter for blue light, a macular pigment in the form of a yellow spot. “This filter varies greatly from person to person, but its level of protection depends on whether you eat enough vegetables,” he says. “You can help reduce your chance of developing age-related macular degeneration by eating a more plant-based diet.”
So should I ditch my blue light glasses and spend the money on more trips to the grocery store? “100 percent,” she says.
Read last week’s article: Fact or Fad: Are Vitamin Drops Worth the Effort?