In 2016, numerous headlines fed the flames of blue light panic. A Telegraph article by the publication’s science editor claimed that taking selfies is aging our skin and that doctors can even tell which hand a person holds their phone when taking a portrait of themselves by noticing which side of their face is the most damaged.
The reason for this premature aging? The blue light from our phone and that burst of illumination from the flash.
Blue light seemingly causes skin aging, upsets our sleep routine, and gives us eye strain. We know all of this from reading it on devices that are, it would appear, slowly poisoning us.
Is blue light really a headline-worthy wrongdoer, though? And are the solutions often presented to us—blue-blocking lenses and glasses—really necessary?
What blue light does to the body
We all remember from biology 101 that the back of our eye, the retina, contains two types of light receptors: the cones, which give us colour vision during the day, and the rods, which allow us to see at night. But over the past couple of decades, scientists have become interested in another retinal cell. Its name is not important (and hard to remember: the intrinsically photosensitive retinal ganglion cell), but its function is interesting: it detects light, especially blue light, but is not as important to vision as the rods and cones are. Rather, it mainly sends signals to the brain to help regulate our circadian clock, telling us when it is night and when it is day. This chatter between the back of our eye and our brain ultimately leads to the release in the blood of the hormone melatonin, which promotes sleep.
This circadian clock worked out well for most of humanity’s history… until the invention of electric lighting, which turned black nights into bright extensions of our day. The yellow glow of incandescent bulbs then made way to the blueish white light of LEDs. This blue glow, which has a wavelength roughly between 400 and 500 nanometres, is now emitted by devices all around us: television sets, computer monitors, smartphones, and tablets. We know that light higher up in energy (i.e. ultraviolet, X-rays, and gamma rays) can be damaging to our bodies. Recently, scientists started to wonder if all of this blue light might similarly cause problems.
Evidence started to emerge from studies done on cells and in laboratory animals, often using much higher doses than what we are typically exposed to, that blue light can actually harm the retina. These findings, combined with our extended use of electronic devices, paved the way for new products: blue-blocking glasses to be worn in the evening (or even all day long) and blue-blocking lenses to be implanted in the eyes of patients getting cataract surgery. Blue-blocking glasses are claimed to relieve eye fatigue and headaches, provide better sleep, and protect your eyes from “harmful” blue light. Those blue-blocking intraocular lenses, meanwhile, are often suggested to help prevent the development of a type of blindness tied to aging.
Blue-blocking glasses
The original type of blue-blocking glasses uses orange lenses to block the vast majority of blue light from reaching the eye. They should not be worn during the day, as blue light keeps us awake. A new generation of blue-blocking glasses, however, features clear, colourless lenses. They look like normal reading glasses (and can also be fitted with your prescription), which makes them more appealing; the downside is that, as recent studies have demonstrated, they do a poor job of filtering out blue light in order to maintain transparency and avoid distorting colours for the wearer.
The Cochrane Collaboration, known for their comprehensive summaries of scientific evidence on matters of human health, recently published a review of the evidence we have on blue-blocking glasses. It would be easy to sum it up as “they don’t work,” but the findings are more nuanced than that.
The authors specifically looked at the best type of evidence—randomized controlled trials—to see if these types of glasses had any clear effect on health. The most confident conclusion they were able to make is that these glasses have little to no effect on visual acuity. Then again, these glasses are not meant to sharpen your vision, but it is nice to know that they don’t seem to worsen it. Every other conclusion from this Cochrane summary was delivered with low to very low certainty given the mediocrity of the studies. The authors were unable to determine if these glasses help with contrast and colour determination, which are indicators of a healthy retina.
Moreover, this Cochrane summary mixed studies that used orange glasses, which do block blue light, with studies that used clear lenses, which do not block blue light well, with yet other studies that didn’t bother to specify the type or brand of blue-blocking glasses they had tested. It’s a mess.
Despite this lack of good evidence, blue-blocking glasses are often suggested for people who suffer from what has been called “computer vision syndrome,” the temporary symptoms of which include blurred vision, eye strain and dryness, as well as headaches and neck-and-shoulder pain. Blue light is fingered as the boogeyman, but there are much stronger risk factors: glare, low humidity, spending uninterrupted time staring at a screen, a suboptimal setup that puts strain on our posture, and even having an out-of-date eye prescription. A simple way to reduce the risk of computer vision syndrome is the famous 20-20-20 rule: after every 20 minutes spent staring at a screen, look at an object at least 20 feet (6 metres) away for 20 seconds.
Blue-blocking intraocular lenses
There are worse afflictions than computer vision syndrome, though, and the topic of blue light has also been raised in the context of cataracts and age-related macular degeneration (AMD). The latter is a loss of eyesight that causes things in the centre of our field of vision to become blurry. While it has been hypothesized that a lifetime exposure to blue light might be a contributing factor to AMD, there is no consensus on this issue at the moment. An argument against blue light increasing the risk of AMD is that the lens in our eye becomes yellower as we get older and thus prevents more and more blue light from reaching the back of our eye. (This has been suggested as one potential explanation for why older adults have more sleep difficulties: not enough blue light during the day.) An aging lens partially blocks blue light, yet AMD still develops.
As for cataracts, patients undergoing surgery to remove their cloudy lens are now offered the option of receiving an artificial lens that can also block blue light. These are known as blue-blocking intraocular lenses and they are coated with dyes that absorb blue and violet light. The idea is that they would lower the risk of later developing AMD. A 2018 Cochrane review of the evidence comparing these lenses to regular ones also faced a paucity of good data. A year after the surgery, patients can probably see at a distance with the same accuracy regardless of the type of lens they were implanted with, but the health of their retina simply could not be ascertained from the published studies.
Like a cataractous lens, the evidence surrounding blocking blue light is frustratingly murky. The solution? To stop focusing on blue light as a bugaboo and put it in its proper context.
Context matters
All of this anxiety over the blue light emanating from our phones makes us forget the brightest light source to which we are exposed: the sun.
The sun bombards us with light that contains the same blue wavelengths emitted by our electronic devices but that is orders of magnitude brighter than what our phone is capable of. A team from Public Health England compared the blue light coming from the sun versus what was emitted by a variety of electronic devices set to maximum brightness. Their conclusion? “Under even extreme long-term viewing conditions, none of the assessed sources [including the sun on a clear English day in June] suggested cause for concern for public health” when it came to blue light. (Ultraviolet light, however, is a real issue, and we should not forget about sunscreen and sunglasses.) True, after the sun sets, we are left with the glow of our devices which can suppress the release of melatonin, but a review of 15 studies on this revealed that after a two-hour exposure to blue light in the evening, our melatonin levels recover within 15 minutes. Hardly a major worry.
If we are tossing and turning in bed, it might not be because of the blue in the light but because of the light itself. Those cells at the back of our eye that communicate with our brain to release melatonin, they are not only sensitive to blue light but to other colours as well. Many electronic devices now come with a night mode, which dramatically reduces the amount of blue light the screen is emitting… but they are still obviously releasing a fairly bright light, just one that is yellower in tint. Dimming all lights before bed, including light fixtures, is thus recommended. After all, falling asleep with an incandescent bulb turned on in the bedroom is not easy, even if its light is yellow and not blue. Moreover, and perhaps most importantly, insomnia can be caused by what we are consuming on our devices. Looking at the news in bed, even with night mode turned on, causes alertness and anxiety. More relaxing activities before going to sleep can help ensure a smoother transition into Morpheus’ arms.
On the topic of computer use and blue-blocking glasses, the American Academy of Ophthalmology is clear: there is no scientific evidence that the computer light damages the eye and the Academy does not recommend any special eyewear for computer use. Any eye strain that results from electronic device use has to do with how the device is used, not by its glow.
Some may choose to avail themselves of blue-blocking technology, citing a desire to be safe rather than sorry. That is fine, but recommending this technology by claiming it has been scientifically demonstrated to be beneficial is either disingenuous or ill-informed.
Having reading glasses made with a blue-blocking technology is also going to cost you extra. I called ten optometrists/opticians in Montreal to ask about prices. While this is not something they can add to a pre-existing pair of glasses, they can select lenses that have this property to make a new pair of glasses, as long as you pay an extra CAD 50 to 60 on average. (The price differences I was quoted ranged from 25$ to 80$.) All of them offered it, none of them said it was useless, except for one person who told me those lenses only blocked 20% of blue light.
Finally, regarding the prospect of our social media influencers prematurely aging their skin by pointing their phones at their faces, I have not been bowled over by the evidence put forward by cosmetic dermatologists. One recent review of the evidence refers to LED light as “toxic and damaging to the eyes and skin,” which is a wild statement to make. If you are worried about what light is doing to your skin, wear plenty of sunscreen before going outside to prevent photodamage caused by ultraviolet radiation.
The light coming from your phone pales in comparison.
Take-home message:
- Evidence for blue light harming our eyes comes from cell and animal studies, not human studies, and there is no consensus on whether a lifetime accumulation is a risk factor for age-related macular degeneration
- The sun emits blue light and is much brighter than any of our electronic devices, yet the blue light from it is not a public health concern
- Blue-blocking glasses that use clear, colourless lenses only block a small percentage of blue light
- There is an absence of good evidence to recommend blue-blocking glasses and blue-blocking intraocular lenses for cataract surgery
- The problems blamed on blue light can be solved by doing the following: dimming lights and relaxing before bed, staring at distant objects regularly when at the computer, and putting on sunscreen before heading outside
