Do blue-light glasses work? A Cochrane review found little evidence

Blue-light filtering glasses are sold on three promises — less digital eye strain, protection for the retina, and better sleep — and a 2023 Cochrane systematic review found little good evidence for any of them. Pooling the randomised trials, the reviewers concluded the lenses may not reduce eye-strain symptoms with computer use over the short term, probably have little or no effect on vision, and have an indeterminate effect on sleep [s1].

What the trials measured

The review included 17 randomised controlled trials comparing blue-light filtering spectacle lenses with ordinary non-filtering lenses in adults [s1]. The studies were small and short: sample sizes ranged from five to 156 participants, and follow-up ran from less than one day to five weeks [s1]. That alone caps how much any of them could show about a product people expect to wear for years.

Quality was a recurring problem. None of the trials had a low risk of bias across all seven of Cochrane's domains; the reviewers judged 65% to be at high risk of detection bias because outcome assessors were not masked, and 59% at high risk of performance bias because participants and staff were not masked [s1]. Only 35% had been pre-registered on a trial registry [s1]. Because of missing data, differing populations and different follow-up lengths, the reviewers could not statistically pool any outcome — there is no meta-analysis in this review, only a structured reading of trials that do not line up [s1].

Eye strain and vision

On visual fatigue, the review found there may be no difference between filtering and non-filtering lenses over less than a week [s1]. One trial reported a mean difference of 9.76 units in the direction of worse symptoms with the filtering lenses, but with a 95% confidence interval from −33.95 to 53.47 across 120 participants — an interval so wide it is consistent with a meaningful benefit, a meaningful harm, or nothing [s1]. On critical flicker-fusion frequency, a standard measure of visual fatigue, one study reported a difference of −1.13 Hz, 95% CI −3.00 to 0.74, again across 120 participants — no clear effect [s1].

For sharpness of vision the answer is firmer. Compared with ordinary lenses, blue-light filtering lenses probably have little or no effect on best-corrected visual acuity: a mean difference of 0.00 logMAR units, 95% CI −0.02 to 0.02, from a single 156-participant study rated moderate-certainty [s1]. On the marketed promise of retinal or macular protection, there was simply nothing to weigh — no randomised evidence addressed macular health at all [s1].

The sleep claim, and the real phenomenon behind it

Sleep is where the marketing is most confident and the evidence least so. Across six trials in 148 participants, the findings were inconsistent — three reported a significant improvement in sleep scores with filtering lenses and three reported no significant difference — leaving the reviewers unable to say the lenses are equivalent or superior to ordinary lenses for sleep quality [s1].

The confusion is understandable, because the underlying worry is legitimate. A 2015 study in PNAS established that evening exposure to the short-wavelength-enriched light emitted by electronic devices can suppress melatonin and phase-shift the biological clock [s2]. In its own experiment, people reading a light-emitting e-reader before bed took longer to fall asleep, had reduced evening sleepiness, secreted less melatonin, showed later timing of their circadian clock, and had reduced next-morning alertness than when reading a printed book [s2]. The habit is near-universal: a survey of 1,508 American adults found 90% used some kind of electronics at least a few nights a week within an hour of bedtime [s2].

But notice what that study manipulated — the device and the timing of light, not a pair of glasses. It shows evening screen light can affect sleep; it does not show that filtering a portion of that light through spectacle lenses undoes the effect. That is the gap the Cochrane review sat in, and could not fill [s1].

What the review could not assess, and the bottom line

Several of the specific claims made for these lenses had no randomised evidence behind them at all: the review found no trial data on contrast sensitivity, colour discrimination, discomfort glare, macular health, serum melatonin levels or overall patient satisfaction [s1]. Reported side effects were infrequent but not nil, and included headache, discomfort wearing the glasses and lower mood [s1].

The honest summary is that blue-light glasses are neither proven to work nor shown to be harmful — they are mostly unstudied at the standard that would justify the claims on the box [s1]. If evening screens are disrupting sleep, the evidence points at the light and the timing themselves rather than at a lens that filters a slice of it [s2]. The reviewers' own conclusion was a call for better trials, which is a polite way of saying the case has not yet been made [s1].

This article describes what the studies found and is not medical advice.

Sources

• Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults — Cochrane Database of Systematic Reviews, 2023-08-18
• Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness — Proceedings of the National Academy of Sciences, 2014-12-22