Everything You Need to Know About Blue Light, Sleep, and Eye Health

Blue light doesn't just refer to the luminous glow from your screens. There's another (sunny) source you should know about — and it's good for you.

Close up of woman using her phone at night
TOWFIQU/Getty Images/EyeEm

Blue light earns a lot of negative attention as harmful to sleep and your circadian rhythm.

And when you think of “blue light,” you’ll likely conjure an image of yourself, lying in bed, with the illumination from your device as the only light in a darkened room.

But contrary to popular belief, blue light — made up of the shortest, highest-energy wavelengths — is actually everywhere. In its natural form, it’s even necessary for good health.

But our habits and devices play a significant role in how it affects us. “We live in the era of screens. We stare at screens most of the day,” says Dr. Rahil Chaudhary, an ophthalmologist at Eye7 Hospitals in South Delhi, India. “But doing so at night is particularly harmful because the blue light messes up your sleep cycle.” And, as we all know, certain phone use habits at night, like doomscrolling, may even trigger mild feelings of depression.

Being mindful of how and when you use your devices can make the difference between waking up fatigued or feeling more rested and alert in the morning. Here are the links researchers have found between blue light, sleep quality, and eye health.

What is Blue Light — and Where Does It Come From?

“Blue light is part of the visible light spectrum — the only waves of light energy that the human eye can see,” says Dr. Dagny Zhu, a Harvard-trained and board-certified ophthalmologist. And it vibrates within the 380-to-500-nanometer range, which is the most “visible” form of light.

And the largest source of blue light is actually all around us. “The greatest source of ambient blue light comes from the sun,” says Zhu. Not only that, according to eye experts — blue light from the sun in the late morning or early afternoon yields 10 times the ambient illumination of blue light from electronics.

And the sun’s blue light is not a bad thing: During the day, blue light emitted from the sun boosts your alertness, aids with memory and cognitive function, and even elevates your mood.

But overexposure to it after sunset can hurt your sleep cycle.

What Too Much Blue Light Does to Your Sleep Quality

Enough exposure to blue light once the sun has set, through artificial sources, can have a negative impact.

Here are some examples of some artificial sources you’re likely familiar with:

  • Smart phones  
  • TVs 
  • Computers  
  • Tablets  
  • Fluorescent lights 
  • LED lights  

Overexposure is when you receive more blue light than what your eyes can filter, which often happens at night and is augmented when your screens are closer to your eyes and you’re bypassing your regular bedtime to stay up.

Man falling asleep with phone in bed
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Bad habits with blue light may cause:

  • Later sleep times   
  • Disrupted sleep quality   
  • Disturbed sleep cycle   
  • Melatonin suppression  

“It inhibits the release of melatonin — the sleep hormone — and this signals your brain to stay awake instead of resting,” Chaudhary says. A study published in the journal Somnologie, found that artificial light at the wrong time may disrupt circadian rhythms and sleep.

And while using blue light in the dark can ravage your sleep cycle, summer’s long days can multiply the disruptive effects of blue light as well. Being observant of when you are exposed to blue light is just as important to syncing our sleep cycle and melatonin secretion.

“We've lived under the sun and been exposed to natural blue light for eons,” says Zhu. She explains that spending a day under the sun is unlikely to be considered overexposure. “We're talking about microscopic pathological changes that add up slowly and cumulatively over the years.”

At the same time, she cautions that staring directly into the sun. "Gazing into the sun for even a few seconds is definitely harmful and can cause permanent damage to part of the retina responsible for central vision," Zhu says.

All to say, that most experts agree that blue light overexposure all comes down to poor user habits — even if you have good intentions. A 2015 study published about light-emitting eReaders in the evening concluded that they negatively affect sleep, circadian timing, and next-morning alertness.

It’s Not All Blue — Benefits of Blue Light Exposure

“Blocking all blue light would be detrimental to our health,” Zhu notes, because when used correctly, it has a lot of benefits. According to the American Academy of Ophthalmology, exposure to blue light from the sun, as well as our screens boosts mood and alertness. A sunrise, for example, signals to our brain that it’s time to wake up.

Man in sportswear stretching before a run in nature
FreshSplash/Getty Images

Natural light is especially important for protecting kids’ health. “Sunlight has been shown to be helpful in the growth and development of children’s eyes,” says Zhu. “Recent studies have shown that more outdoor time for children protects against the progression of myopia or nearsightedness.”

Some benefits of blue light:

  • Elevates mood 
  • Boosts alertness 
  • Improves memory and cognitive function 
  • Regulates the body’s natural wake and sleep cycle 

What About Claims That Blue Light Damages Your Eye Health?

“We definitely know that UV rays cause cataracts, eye cancer, and growths on the clear covering over the white part of the eye,” says Zhu, and for these risk factors she recommends wearing sunglasses while outside. However, she also notes that “the contribution and significance of blue light remains unclear.”

In recent years, there’s been evidence that high levels of blue-light exposure can cause retinal toxicity. The overall research on eye damage, however, remains mixed.

One 2018 study, published in the International Journal of Ophthalmology, found it can cause diseases such as dry eye, cataracts, and age-related macular degeneration. Yet Zhu points to more recent research, which claims that a small amount of blue light coming from our computer screens has never been shown to cause any harm to our eyes. Still, she notes that more long-term studies are needed.

“For the average person working with everyday digital devices, the risk of eye damage is likely very low. However, people with pre-existing retinal conditions like macular degeneration should probably exercise greater caution,” says Zhu.

She also warns that exposure to high intensity blue light can be an occupational hazard for some workers in industrial settings. “This refers to both greater chronic exposure to moderate levels of blue light over many years,” Zhu notes, “and acute exposure to very high intensity blue light over a shorter period of time.”

Kids Are Especially Impacted By Blue Light

Kids in particular are even more sensitive to these effects. In 2018, researchers studied 22 healthy children (12 boys and 10 girls) and 20 of their parents (adults), and found that the impact of light is greater in children than in adults.

“Children absorb more blue light than adults,” says Zhu. “That’s because their pupils are larger and their lenses are clearer, whereas adults have smaller pupils and cloudier age-related lens changes that act as a better shield.”

How to Limit Blue Light Exposure

Instead of stressing over blue-light exposure, your best bet is to build boundaries around your device use. Think twice when grabbing your phone and bringing it with you to bed. You could, for example, set a timer and then charge your phone from across the room.

Or to curb the impulse of grabbing your phone at bedtime, try removing the tempting allure of nighttime electronic use with a tech tuckaway nightstand — which allows you to hide your devices without unplugging them.

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Tech Tuckaway Nightstand DIY with Cara Newhart

For practical reasons, some people, including on-call workers, can't sleep with their phone in a separate room. If turning your device off isn’t an option, a blue-light filter applied directly to your device’s screen can give an added layer of protection.

Tips for limiting blue light exposure:

  • Avoid bright screens at night by turning off your devices one-to-two hours before bedtime. 
  • Be deliberate with your blinks to combat digital eye strain. We normally blink 15 times a minute, but this drops to less than half when working in front of a screen.  
  • Make a habit of taking frequent breaks from your devices  by trying the “20-20-20” rule — every 20 minutes, look away from your screen and place your eyes on an object 20 feet away for at least 20 seconds. The widget-style app Pomy can be a helpful reminder. 
  • Use an app hack like turning on “night mode” on your phone at night. 
  • Protect kids’ sleep and eye health by encouraging outside play for at least 60 minutes each day. 

You can also curb your exposure by trying out tools like blue-light-blocking glasses or screen filters, Zhu adds. But she cautions that the evidence on reducing eye strain is mixed.

“Though there’s not enough science to back up many of the marketing claims, some people do notice a benefit,” says Zhu. “[Still] there’s no harm in buying from reputable eyeglasses brands and trying it out for yourself.”

If you’d like to try out a pair of blue-light-blocking glasses, we recommend Swanwick's orange lenses, which we’ve found to block out more blue light than other brands.

[Note: If you buy something using a link on our site, we may earn a commission.]

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When You Should Worry About Blue Light

As the presence of blue light in our lives continues to grow, it’s normal to worry about its effects. But it’s important to remember that our biggest source of blue light comes directly from the sun and benefits us in many ways.

Ultimately, experts confirm that it all comes down to our habits — and timing is essential. Your best plan is to create healthy boundaries to limit your exposure during the evening and in bed. And naturally, these habits may end up quashing your impulse to doomscroll.

Reclaiming quality sleep can feel like a marathon but every habit we build is a step closer to making sleep easier. Beyond blue light exposure, other lifestyle habits, like your bedtime routine, getting enough fresh air, and setting up the right bedroom environment go a long way with preparing your body and mind for rest.

Need a little extra help to aid with sleep? We’ve got details on a sleep diary, tips and tricks for the best sleep position, and some natural remedies to help you fall asleep faster.

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