The LEDs used in our digital devices emit light that is shifted toward the blue spectrum. Recent experimental as well as observational studies have shown that intense or sustained blue light exposure can cause retinal damage in animals. In response to this research, coatings are now available for eyeglasses that block out the high-energy, blue light spectrum and there are settings on newer monitors and apps for phones that offer to reduce blue light emissions.
A quick search of headlines from around the world that mention blue light turns up: “Children Using Smartphones at Risk of Irreversible Eye Damage,” “Smart Ways To Protect Your Child’s Eyes From Smart Screens,” and “Health Alert: Blue Light Blindness.”
So, should we add the blue light from our phones and computers to the ever-expanding list of things we’re to fear? Does staring at our phone while playing Pokeman Go damage our retinas in addition to the falling-off-cliff or walking-in-front-bus damage which we are to expect as part of the normal gameplay experience?
Naturally, it’s more complex than this. The answer involves considering the effects of blue light in three areas: eye strain, sleep, and the health of the retina itself.
Relative to other segments of the visible light spectrum, blue light is high-energy and short-wavelength. Because of its shorter wavelength, blue light is scattered more easily than other colors (this scattering is why the sky is blue). Blue light is also refracted (bent) more than other colors as it passes through the lens of your eye (this is part of the reason most people will see the red letters in the headline above as floating in front of the blue background). Because of this different nature of blue light, glasses that filter out the blue spectrum can result in sharper, more relaxed vision especially when viewing images on an electronic device.
Blue light exposure has also been shown to be one of the primary drivers of circadian rhythms. A 2003 study by Lockley at Harvard Medical School found that the circadian rhythms of humans are about twice as sensitive to shorter wavelength blue light than longer wavelength, more yellow light. Blue light therapy has been used as an effective means to increase alertness and has been looked into as a method of treating seasonal affective disorder. While becoming more alert and awake is great during the day, it’s not ideal in the evening before bed.
Predictably, a 2015 study by Chang found that evening exposure to electronic devices adversely affects sleep, circadian rhythm, and alertness the next day. Participants were given either an electronic reader or a printed book to read before bed, and those with the e-books took longer to fall asleep, didn’t sleep as well, had lower melatonin levels, and weren’t as alert the next morning.
The final aspect often mentioned regarding blue light is the possibility of retinal damage due to sustained exposure to this shorter wavelength light. In the famous Beaver Dam, Wisconsin study of the effects of sunlight on the retina, it was found that those with more exposure to sunlight were more likely to have some of the early signs of macular degeneration, and folks who wore sunglasses and hats limited this risk. An earlier study of watermen on the Chesapeake Bay, estimating light exposure broken down by different bands of wavelengths, had found that the blue light exposure was most associated with the development of macular degeneration later in life. Experimental studies in rhesus monkeys and albino rats have shown that it is possible to cause damage to the retina with either short, intense exposure, or sustained exposure to visible light and that blue light may be the most damaging portion of the spectrum.
However, it is still unclear if we need worry about blue light exposure in everyday life because damage depends on the intensity, type, and timing of exposure and retinal damage has been controlled in animal studies by providing supplements of antioxidants or carotenoids. What’s more, other researchers have evaluated the intensity of blue light emitted from common electronic devices like phones and tablets and found that while the intensity of blue light emitted from the sun or a welding torch is strong enough to damage the retina, the LEDs in electronic devices do not emit an intense enough light to cause harm during normal usage. A good summary of the current thought appeared in a recent study by Tossini in the journal Molecular Vision: “Although we are convinced that exposure to blue light from LEDs in the range 470–480 nm for a short to medium period (days to a few weeks) should not significantly increase the risk of development of ocular pathologies, this conclusion cannot be generalized to a long-term exposure (months to years).”
So, is it worth spending the extra money to put the special coating on your glasses that filters out part of the blue light spectrum? Well, it will make vision more relaxed and slightly sharper, especially on the computer. It will likely help you sleep better if you’re in the habit of using electronic devices before bed. Though, you could probably get the same effect by just reading a book printed on paper too. Will it keep your eyes safe from retinal damage? Good question, we don’t really know. It seems that there are reasons to believe that it might help with blue light exposure from the sun over many years, and is probably an especially good idea if you have a history of macular degeneration in your family. But, eating plenty of vegetables, not smoking, and wearing sunglasses and a hat outdoors are likely more important.