Do blue-light glasses work? What the Cochrane review and eye doctors say

What blue-light glasses claim

This review draws on the 2023 Cochrane systematic review of randomized trials and an earlier meta-analysis of tinted glasses worn before bed^{1, 3}. It also draws on a patient page from the American Academy of Ophthalmology and an expert consensus on indoor light^{2, 4}. None of the trials measured whether the lenses protect the retina, and the Academy doesn’t recommend them^{1, 2}.

The meta-analysis of tinted glasses found a small gain in measured sleep time³. That gain was significant in patient groups but not in healthy participants³. For evening light, the Academy suggests avoiding screens for two to three hours before bed². A light-science expert consensus also sets a low ceiling for indoor light in the evening⁴.

Blue-light filtering lenses cut out part of the short-wavelength, or blue, end of visible light. They’re sold to ease eye strain, protect the retina and improve sleep¹. The Cochrane reviewers note that digital devices such as LED-backlit screens give off relatively more short-wavelength light than traditional incandescent light sources¹. That’s the usual starting point for these claims¹.

Two quite different uses share the label. The eye-strain trials tested lenses worn during computer work¹. The studies in a meta-analysis of glasses worn before bed tested amber, orange or brown tinted lenses³. People usually wore them for two to three hours before bed, for anywhere from two days to a month³.

Orange lenses also dim everything you see³. The meta-analysis authors put their visible-light transmission at roughly 30% to 45%³. By contrast, the amber lenses in two of its studies let through about 90%³.

What the trials show for eye strain and sleep

The most complete summary is a 2023 Cochrane systematic review comparing blue-light filtering lenses with non-filtering lenses in adults¹. Its search ran to March 2022 and found 17 randomized controlled trials with 619 participants¹. The trials enrolled between 5 and 156 people each, and follow-up ran from less than a day to five weeks¹. Eight used a crossover design, in which each person tried both lenses¹.

Participants included healthy volunteers, computer users with symptoms, recreational athletes, radiology residents and adults with artificial lens implants in both eyes¹. Some trials enrolled people with sleep problems, insomnia, depression or bipolar disorder¹. The data were too sparse and varied to pool, so each outcome rests on one or a few trials¹.

On eye strain, the reviewers concluded that the lenses may not reduce strain from computer use over a short follow-up¹. One trial of 120 people measured visual fatigue over less than a week and found no clear difference¹. Its 95% confidence interval was wide enough to include both benefit and harm (low certainty)¹. Two smaller studies with 46 people between them also reported no significant difference in visual fatigue¹.

The 120-person trial also found little or no difference in critical flicker-fusion frequency, a lab measure of visual fatigue (mean difference -1.13 Hz, 95% CI -3.00 to 0.74; low certainty)¹. A trial of 156 people found no difference in best-corrected sharpness of vision (mean difference 0.00 logMAR, 95% CI -0.02 to 0.02; moderate certainty)¹.

On sleep, six trials with 148 participants reported sleep quality, and the review rated that evidence very low certainty¹. Three reported better sleep scores, in 20 people with sleep difficulty, 15 recreational athletes and 15 people with chronic insomnia¹. Incomplete reporting meant the reviewers couldn’t calculate how large those gains were¹. The other three found no significant difference, in 20 people with depression and trouble falling asleep, 43 with bipolar disorder and 35 with insomnia¹. Two trials with 42 people measured daytime alertness, and the effect is unknown (very low certainty)¹.

An earlier meta-analysis looked only at tinted glasses worn before bed³. It included 12 studies: 8 randomized trials and 4 before-and-after studies without a comparison group³. Each analyzed between 6 and 21 people³. Four of the six sleep-quality trials in the Cochrane review are among them^{1, 3}. The studies covered healthy adults and adolescents, plus people with sleep complaints, insomnia, delayed sleep timing, ADHD, depression and bipolar mania³.

Measured total sleep time rose slightly (Hedges’ g 0.32, 95% CI 0.01 to 0.63; 6 studies)³. Measured sleep efficiency didn’t change significantly (g 0.31, 95% CI -0.05 to 0.66; 7 studies)³. Self-reported sleep quality and sleep time also improved, but each rested on only three studies³. Time to fall asleep and time awake at night varied too much between studies to pool³.

Split by group, the gain in measured sleep time was significant in patients (g 0.52, 95% CI 0.07 to 0.98)³. In healthy participants it wasn’t (g 0.21, 95% CI -0.55 to 0.97)³. The authors described the evidence as mixed and called for larger, well-controlled trials³. They suggested any benefit may be larger in people with insomnia, bipolar disorder, delayed sleep timing or ADHD than in healthy good sleepers³.

What the trials don’t show

It doesn’t show that the lenses ease eye strain. The largest visual-fatigue trial and two smaller studies all found no clear or significant difference¹. The trials also carry a high risk of bias: none of the 17 was at low risk across all seven areas Cochrane checks¹. In 65% of the trials, the risk was high because outcome assessors knew which lenses people wore¹. In 59%, it was high because participants and staff knew¹.

It doesn’t show that the lenses protect the eyes. No included trial measured macular health¹. None looked at contrast sensitivity, color vision, glare or blood melatonin levels either¹. The concern that blue light damages the retina comes from animal and cell-culture experiments¹. The review notes that 10 of 12 major population studies didn’t report a positive association between light exposure and age-related macular degeneration¹.

The American Academy of Ophthalmology says there’s no scientific evidence that light from computer screens damages the eyes². It adds that the amount of light from a computer has never been shown to cause any eye disease². The Cochrane review also notes that the UK advertising regulator ruled one optical retailer’s claim misleading¹. The retailer said its lenses filter out harmful blue light, and the regulator found that claim lacked adequate substantiation¹.

It doesn’t show better sleep for healthy people who already sleep well. The Cochrane evidence on sleep quality is very low certainty and split down the middle¹. Five of the six trials enrolled people with sleep difficulty, insomnia, depression or bipolar disorder¹. The sixth enrolled 15 recreational athletes¹. In the tinted-glasses meta-analysis, the gain in measured sleep time wasn’t significant in healthy participants³.

The meta-analysis authors also noted that adherence was hard to check³. The light people were actually exposed to was rarely measured³. And the studies couldn’t separate blocking blue light from simply dimming everything³. No study in either review lasted longer than five weeks^{1, 3}.

Do eye doctors recommend blue-light glasses?

The American Academy of Ophthalmology doesn’t recommend blue light-blocking glasses, or any special eyewear for computer use². It says several studies suggest the glasses don’t improve symptoms of digital eye strain². In its view, the strain comes from how people use their screens, not from anything coming from the screens². Long hours of staring mean less blinking². Most symptoms are temporary and ease after you stop using the computer².

For screen-related eye strain, its suggestions are about habits and setup rather than lenses²:

• Take a 20-20-20 break: every 20 minutes, look at something at least 20 feet away for at least 20 seconds²
• Sit about 25 inches, roughly arm’s length, from the screen²
• Place the screen so your gaze falls slightly downward²
• Use artificial tears when your eyes feel dry²
• Adjust room lighting and increase screen contrast²
• Add a matte screen filter if needed²
• If you wear contact lenses, take breaks wearing glasses instead²

What experts suggest for evening light

The concern about evening light and sleep has some basis. The American Academy of Ophthalmology notes some evidence that blue light affects the body’s circadian rhythm, the natural wake and sleep cycle². It says the best way to avoid sleep disruption is to avoid screens for two to three hours before bed². It adds that a dark or night mode in the evening can help too².

A 2022 expert consensus puts numbers on indoor light for healthy adults⁴. It comes from the Second International Workshop on Circadian and Neurophysiological Photometry⁴. It uses melanopic equivalent daylight illuminance (melanopic EDI), a measure weighted to the light-sensitive eye cells that drive the body clock⁴. The authors chose it because ordinary lux readings are a poor stand-in for those effects⁴.

The targets rest mainly on laboratory studies in healthy adults of melatonin suppression, body-clock shifts and alertness⁴. Supporting field studies looked at daytime lighting in offices, schools and care homes⁴. The targets apply to healthy adults aged 18 to 55 with regular daytime schedules, and aren’t meant for night shift workers⁴. They may need adjusting for children, older people and clinical groups⁴. The authors cite a study in which sensitivity to evening light, measured by melatonin suppression, varied more than tenfold between people⁴.

The targets describe the light reaching the eye from daylight and room lighting across the day and evening⁴. The tinted-glasses studies, by contrast, rarely measured how much light people were actually exposed to³. The consensus sets three targets⁴:

• Daytime: at least 250 lux melanopic EDI at the eye, using daylight first where possible⁴
• Evening: no more than 10 lux melanopic EDI from at least three hours before bedtime, ideally from white light low in short wavelengths⁴
• Sleep: as dark as possible, no more than 1 lux melanopic EDI, or 10 lux if some light is needed to see at night⁴

Are blue-light glasses safe?

The glasses appear low risk, but the data on harms are thin. Nine trials with 333 people reported on side effects, and only three or four of them described any events (the review gives both counts)¹. Reported events were infrequent and included headache, more depressive symptoms, lower mood and discomfort wearing the glasses (low certainty)¹. Similar events showed up with non-filtering lenses¹. The reviewers thought they mostly came from wearing glasses in general, not from the filtering lenses themselves¹.

Tinted evening lenses also cut overall brightness, not just blue light³. The meta-analysis authors put the visible-light transmission of orange lenses at roughly 30% to 45%³.

The Academy says most eye symptoms from computer use are temporary². If symptoms continue, it says to contact an ophthalmologist².

Sources

1. Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults Cochrane Database of Systematic Reviews, 2023 · systematic review
2. Are Blue Light-Blocking Glasses Worth It? American Academy of Ophthalmology, 2021
3. Interventions to reduce short-wavelength ("blue") light exposure at night and their effects on sleep: a systematic review and meta-analysis Sleep Advances, 2020 · meta-analysis
4. Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults PLOS Biology, 2022 · guideline