Health

Should you wear blue-light glasses while looking at screens?

They’re all the rage right now, but they may not do what you expect.

Credit: Reviewed / Jackson Ruckar

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Let’s face the technological facts: Many of us spend all day in front of a computer screen for work or school, only to spend our free time staring at a TV, smartphone, or tablet. According to The Vision Council, a nonprofit trade association of manufacturers and suppliers in the optical industry, 80 percent of American adults report using digital devices for more than two hours per day and 59 percent report suffering from “digital eye strain.” But are blue-light blocking (or “filtering”) glasses actually a solution, as some manufacturers claim? We tested in our labs to find out whether these special lenses indeed filter out blue light and talked to experts to learn if these special lenses are a viable fix that’s worth you spending your money on.

What is blue light?

Every visible color on the light spectrum has a different wavelength and corresponding amount of energy. The shorter the wavelength, the more energy a color ray contains, according to All About Vision, an editorial site owned by ophthalmic lens giant EssilorLuxottica. Of the light our eyes can see, blue rays have the shortest wavelength and the most energy. Before the invention of artificial light—and as humans are diurnal (rather than nocturnal) creatures—our brains took cues from the sun’s spectrum to regulate sleep cycles. In particular, the sun’s energetic blue waves signaled that we should be awake during the day, and the lack of that light, after sunset, meant it was time for sleep. In our modern lives, we’re exposed to a lot more blue light for a lot more hours of the day and night, thanks especially to digital screens and fluorescent lights. This is something our evolutionary ancestors didn’t face, and therefore raises modern dilemmas.

What are the health effects of excessive blue-light exposure?

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Credit: Reviewed / Jackson Ruckar

Blue light signals to our brain that we should be awake.

Blue light is responsible for boosting our attention and our moods. When our eyes take in blue light, our brains get the signal to be awake and energized. Blue light exposure also suppresses the secretion of melatonin—the hormone responsible for regulating the body’s circadian rhythm—more than other light wavelengths. That’s why late-in-the-day exposure is counterproductive to sleep and why sleep experts advise us to put our phones away before bed.

Late-in-the-day exposure to blue light is counterproductive to sleep, which is why sleep experts advise us to put our phones away before bed.

The effect that blue light has on eye strain, however, is less well known, despite the claims made by the manufacturers of blue light-blocking glasses. The American Optometric Association cites a host of reasons someone might suffer from digital eye strain, including poor lighting, glare on a digital screen, improper viewing distances, poor sitting posture, uncorrected vision problems, or a combination of these factors—without any mention of blue light.

How do blue-light blocking glasses claim to work?

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Credit: Reviewed / Jackson Ruckar

Blue light has the shortest, most energetic wavelengths.

Blue light scatters within the eye, explains Christopher Taylor, PhD, a research assistant professor at New England College of Optometry. And as it’s not easily focused, it causes a “noise” in the eyes, according to All About Vision. These glasses have special lenses that claim to “absorb” or “block the penetration” of blue light before it reaches our eyes. Some glasses use yellow-tinted lenses to counteract the blue, while other proprietary lenses modify light’s color temperature by other means. The net effect: Less blue light reaches the brain. That is, if they work.

Do blue-light glasses do what they claim?

Reviewed’s senior scientist, Julia MacDougall, analyzed a few pairs of the most popular glasses from Felix Gray, Gunnar, and Pixel to find out if they worked. “Testing the blue-light glasses took a little bit of ingenuity on our part, especially because it took us a while to figure out what blue-light glasses actually do,” she says. First we set up a very basic test using a bright laptop screen in a dark room. We aimed an instrument that we usually use in TV testing to record light color and luminance, the Konica Minolta CS-200, at the laptop screen. Then we took light readings of the screen both with and without the blue-light glasses.

Laptop Test
Credit: Reviewed / Betsey Goldwasser

We pointed the Konica Minolta CS-200 at the laptop screen with and without the blue light-blocking glasses.

We thought this test would be revealing because blue-light glasses claim to remove blue light; in taking screen readings through the lenses, we should’ve seen a change in the level of blue light recorded, right?

Wrong. To our surprise, while the glasses reduced the amount of light coming through (to be expected, since that’s essentially what polarized lenses do), we observed little to no difference in the color of the screen’s light with and without the glasses.

That proved to be a head-scratcher at first. But talking with one of our staff photographers gave us another clue: He pointed out that the glasses claim that they could maintain the blue color fidelity; that is, wearing the blue-light glasses should not affect your perception of the exact color shade of a blue object, whether it’s on a screen or not.

Lights
Credit: Reviewed / Betsey Goldwasser

The five LEDs used in our blue light glasses testing, arranged in order from blue (left) to UV (right).

This is the crux of the issue: How can blue-light glasses claim to remove blue light without changing the shade of blue you see? Imagine you’re painting with acrylic paints. If you mix white, red, and blue in equal amounts, you’re going to end up with a light purple. However, if you add less blue, or no blue at all, you end up with a color that’s closer to pink. By definition, filtering blue light means that you reduce or remove some shades of blue and leave behind others; this alters the final color of a blue object. But it doesn’t, in the case of these glasses.

A little puzzled at the contradiction, we decided to investigate how wearing these glasses affected our perception of blue light specifically, as opposed to the white light of a laptop screen. We once again took light readings with the CS-200, but this time, the targets were five LED lights that have contain very specific shades of blue: cyan (wavelength of 472 nm), azure (wavelength of 462 nm), palatinate blue (wavelength of 430 nm), and two shades of purple (wavelengths of 400 nm and 385 nm). The last two LEDs verge on the ultraviolet part of the visible spectrum, which means that it’s difficult for the human eye to detect the light coming from those LEDs, similar to how it’s tough to actually see the light coming from UV lamps unless it’s you’re looking at the UV light shining on a white object.

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Credit: Reviewed / Betsey Goldwasser

The five LEDs are arranged in order from blue (left) to UV (right). The blue light glasses noticeably affect the light coming from the two UV LEDs on the right, which represent the more energetic end of the light spectrum.

The results were, ahem, enlightening. When pointed at the three blue LEDs, the glasses reduced the amount of light coming through (as they do for all light sources), but they didn’t alter the shade of blue recorded by the CS-200. However, for the two UV LEDs, both the amount of light and the color content changed when we put the blue-light glasses between the light meter and the LEDs.

This is when the (metaphorical) light bulb went off: In addition to reducing the total amount of light (both blue and not) that goes into your eye, blue-light glasses remove or reduce the type of blue light that you have difficulty seeing anyway. This is how the brands that make blue-light glasses can make claims about both maintaining blue color fidelity and removing potentially harmful blue light.

What are blue-light glasses useful for?

Given Julia's outcome in the lab, we feel confident saying that these glasses do block some blue light, and therefore might help to keep your sleep cycle on track, even if you're up late on your computer or watching TV. Still, the expert advice is to shut down your screens at least an hour before bedtime, as eliminating the source of blue light entirely is the absolute best way to ensure better shut-eye.

Still, the expert advice is to shut down your screens at least an hour before bedtime, as eliminating the source of blue light entirely is the absolute best way to ensure better shut-eye.

However, even though our lab concluded that blue-light glasses work at filtering light, there remains no scientific evidence to back up that these help with your headache-inducing eye strain, despite any claims the manufacturers make.

What is proven to reduce eye strain?

Still at a loss for how to deal with your achy eyes? “The first thing to do for someone experiencing eye strain is to get a comprehensive eye exam,” Taylor says. He also recommends resting your eyes frequently during long bouts of computer use, reading, or other activities that are strenuous on them. “Even a break as simple as looking into the distance for a few minutes can help,” he says. Increasing the font sizes on your devices or utilizing night mode could help reduce eye strain, as well.

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