Do Blue Light Glasses Work? What a Cochrane Review Found

Order a new pair of glasses and there’s a fair chance you’ll be offered a blue light filter for an extra charge. Blue light glasses are sold mainly on two promises: less eye strain after a day at a screen, and better sleep after an evening in front of one. Both sound reasonable, since screens do give off blue light and light affects sleep.

So do blue light glasses work? For eye strain, the trials found no clear benefit, and for sleep the evidence is too thin and mixed to say. That’s the conclusion of a 2023 Cochrane review of 17 randomized trials comparing blue-light filtering lenses with standard lenses. What matters more for sleep is how much light reaches your eyes in the evening, and that costs nothing to change.

What 17 Trials Say About Blue Light Glasses

Blue-light filtering lenses use a coating or tint to hold back part of the short-wavelength light from screens, LED bulbs and the sun. The Cochrane team found 17 trials comparing them with standard lenses in adults, with 619 people across six countries. Most were small, from 5 to 156 people each, and follow-up ranged from under a day to five weeks.

For eye strain, three trials measured how tired people’s eyes felt, and none found a difference. The largest gave 120 adults either filtering or standard lenses for a two-hour computer task. The reviewers rated this evidence low certainty, so a small benefit can’t be ruled out.

Sleep was murkier. Six trials with 148 people measured sleep quality: three found an improvement and three didn’t, and the evidence was rated very low certainty. Most participants had insomnia, depression or bipolar disorder, and all six trials used amber or orange lenses worn in the hours before bed, unlike the nearly clear lenses usually sold for screen work. None of the 17 trials reported blood melatonin levels or checked whether the lenses protect the retina. Side effects such as headaches, low mood or discomfort were infrequent, and similar complaints came up with standard lenses.

Singh, S. et al. (2023). “Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults.” Cochrane Database of Systematic Reviews, 8, CD013244.

Where Eye Strain Comes From

Tired, dry eyes after a day at a screen usually have ordinary causes. You blink less while you concentrate on a screen, so the surface of the eye can dry out. Holding focus at one short distance for hours is tiring in itself, and an out-of-date or missing prescription makes it worse.

The standard advice is the 20-20-20 rule: every 20 minutes, look at something at least 20 feet (about 6 meters) away for 20 seconds. In a study from the University of Valencia, 29 people with eye strain, aged 18 to 43 and at a computer about seven hours a day, got laptop software that watched through the webcam and reminded them to take these breaks. After two weeks, their eye strain and dry eye symptoms had eased, but a week after the reminders stopped, symptoms were no longer clearly better than at the start. There was no separate comparison group, and the authors couldn’t rule out a placebo effect.

Talens-Estarelles, C. et al. (2023). “The effects of breaks on digital eye strain, dry eye and binocular vision: Testing the 20-20-20 rule.” Contact Lens and Anterior Eye, 46(2), 101744.

If your eyes still ache or your vision blurs after a few weeks of regular breaks, or screen work brings on headaches, book an eye test with an optometrist rather than buying a filter.

Evening Light and Your Body Clock

For sleep, the question is how much light reaches your eyes, and when. In a 2015 study in Boston, 12 healthy young adults lived in a hospital research unit for two weeks. On five evenings they read on an iPad at full brightness for about four hours before bed, and on five others they read a printed book, with the room kept very dim both times. Reading on the iPad suppressed their evening melatonin by about 55%, while the book didn’t. After the iPad evenings, the nightly rise in melatonin came about an hour and a half later, they took nearly 10 minutes longer to fall asleep, and they felt sleepier the next morning.

That was a heavy dose, four hours at maximum brightness, in only 12 people. The authors also noted that they couldn’t say whether the screen’s blue-rich color or simply its brightness was responsible, since the paper book was lit by very dim room light alone.

Chang, A.M. et al. (2015). “Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness.” Proceedings of the National Academy of Sciences, 112(4), 1232-1237.

A 2019 study from Monash University in Melbourne shows how little light it takes. Over six or seven weeks, 55 people aged 18 to 30 spent one evening a week in the lab under a different light level, from 10 to 2,000 lux, after a dim evening for comparison. On average, about 25 lux halved their melatonin, which is as dim as or dimmer than typical indoor lighting at night. The most sensitive person reached that point at 6 lux, the least sensitive at 350 lux. All were healthy and young, so the numbers may not hold for older adults.

Phillips, A.J.K. et al. (2019). “High sensitivity and interindividual variability in the response of the human circadian system to evening light.” Proceedings of the National Academy of Sciences, 116(24), 12019-12024.

Night Shift Mode Put to the Test

Phones now offer a built-in version of the glasses. Night Shift on iPhone and Night Light on many Android phones warm the screen’s colors in the evening. A 2021 trial tested Night Shift on 167 young adults aged 18 to 24, recruited at a US university. Each was randomly assigned to one routine for seven nights: iPhone use in the hour before bed with Night Shift on, with it off, or no phone at all, while wrist sensors tracked their sleep.

The three groups slept about the same, with no difference in how long they took to fall asleep, how long they slept or how much they woke in the night. Among those who averaged more than 6.8 hours of sleep, an exploratory analysis found that the no-phone group slept best, with higher sleep efficiency and less time awake. That hints that putting the phone down mattered more than changing its color, though a subgroup finding in young adults needs confirming.

Duraccio, K.M. et al. (2021). “Does iPhone night shift mitigate negative effects of smartphone use on sleep outcomes in emerging adults?” Sleep Health, 7(4), 478-484.

What to Try Tonight

To protect your sleep from screens, lower the dose rather than change the color. Tonight, an hour before your usual bedtime, switch off the ceiling light and use a single lamp, turn your phone’s brightness down as far as is comfortable, and leave the phone charging outside the bedroom. Keep Night Shift on if you like the warmer color, but on its own it made no difference in the trial. If you already own blue light glasses, there’s no need to throw them out. Just don’t count on them to do the job of a dimmer evening. And if you regularly lie awake for hours whatever you do, talk to your doctor.

People differ a lot in how evening light affects them, so check your own pattern. Lamplit’s sleep log is free: each morning, enter your bed and wake times, rate the night from “Poor” to “Excellent”, and add the “Late screen” factor if you used a phone, tablet or laptop in the last hour before lights out. After two weeks, compare the tagged nights with the rest. If they started later or got lower ratings, that’s a clue worth acting on.

Log last night’s sleep in Lamplit, and tag it if you had a late screen. It’s free.