Blue-light glasses: are they really worth it?

Blue-light-filtering lenses are marketed as protection against screen-related eye strain, retinal damage and sleep disturbance. Yet the pooled evidence from the available clinical trials does not bear out these promises. Here is what the science actually says, and, more importantly, what genuinely relieves your eyes in front of a screen.

THE ESSENTIALS

What exactly is “blue light”?

Visible light is made up of wavelengths ranging from red (the longest) to violet (the shortest). Blue light corresponds to the part of the spectrum lying roughly between 400 and 500 nanometres: a high-energy light that is abundant in natural sunlight, but also emitted, in far smaller amounts, by the LEDs in our screens, smartphones and lighting.

Blue light is not “bad” in itself. Some of it even plays an essential physiological role: it synchronises our body clock and keeps us awake and alert during the day. The debate, then, is not about blue light as such, but about one specific question: is the blue light from screens harmful, and does a filtering lens make any difference?

Screens versus the sun: a matter of dose

This is the point that marketing conveniently leaves out. The intensity of blue light you receive while looking at a screen is about a thousand times lower than what you receive outdoors on an ordinary day, let alone when glancing towards a bright sky. In other words, if screen exposure were enough to damage the retina, simply stepping outside during the day would be infinitely more worrying. In toxicology as in ophthalmology, it is the dose that makes the risk.

THE PROMISE

What filtering lenses promise

Over the past decade or so, “blue-light” lenses and glasses have become a mainstream product, often offered as an add-on when you buy spectacles. Three benefits are generally put forward:

• Reducing eye strain felt after a long day of screen use
• Protecting the retina from premature ageing or maculopathy
• Improving sleep by limiting evening exposure to blue light

These arguments are appealing because they rest on real facts, blue light does exist and it does influence the body clock, but they make a subtle leap: from “blue light has effects” to “therefore a lens that filters it protects you.” It is precisely this shortcut that the studies allow us to test.

THE EVIDENCE

What the science says: the Cochrane 2023 review

The most robust reference on the subject is a Cochrane systematic review published in 2023 Singh 2023. Cochrane reviews represent the highest level of evidence in medicine: following a strict methodology, they pool all the available clinical trials. Here, the authors analysed 17 randomised controlled trials, carried out in several countries.

Their conclusions are clear, and run counter to the marketing message:

• Eye strain: filtering lenses probably do not reduce symptoms of screen-related eye strain compared with standard lenses.
• Sleep: the findings are inconclusive, with some studies showing an effect and others not, and no clear trend.
• Retinal health: no conclusion is possible, because no study measured any structural change in the macula that could be attributed to wearing these lenses.

The authors also stress that the available studies were short in duration and of variable quality: nothing therefore allows any claim of long-term benefit. Put simply, at the current level of evidence, paying extra for a blue-light filter offers no demonstrated advantage for the comfort or health of your eyes.

An absence of proven effectiveness does not mean a filtering lens “does harm”: most are neutral and well tolerated. It means they do not deliver the promise for which they are often sold at a premium.

THE STRAIN

So where does screen-related eye strain really come from?

Digital eye strain, which ophthalmologists call asthenopia or computer vision syndrome, is very real. A meta-analysis published in 2023, covering 45 studies, estimates that it affects nearly two thirds (66%) of regular screen users Anbesu 2023. But its causes have nothing to do with the colour of the light.

The drop in blink rate and dryness

This is the central mechanism. Normally, we blink 15 to 20 times a minute. In front of a screen, focused, we drop to around 5 blinks a minute. The tear film, which is no longer renewed often enough, evaporates: the eye becomes dry, it stings and burns, and vision blurs intermittently. This is by far the leading cause of discomfort, and it also explains why the problem worsens during remote working or in air-conditioned air.

Sustained focusing effort

Fixing your gaze on a close-up plane for hours forces the muscle that focuses the eye (accommodation) and the convergence muscles into continuous work. This static effort is tiring, exactly like a muscle held contracted for a long time. An uncorrected or poorly corrected refractive error (short-sightedness, long-sightedness, astigmatism, early presbyopia) makes this phenomenon markedly worse.

The working environment

Sitting too close to the screen, glare, unsuitable lighting, text that is too small, a screen placed too high: all of these force the eye to compensate constantly. None of these factors is corrected by a blue-light filter.

Blue light and sleep: the real nuance

This is where the question becomes more subtle. It is true that light, and its blue component in particular, affects the secretion of melatonin, the sleep hormone. Specialised cells in the retina, sensitive to wavelengths around 460 to 480 nm, relay light information to our internal clock. Light exposure in the evening can delay sleep onset: this is well established, notably in the expert assessment by ANSES ANSES 2019.

But two nuances change everything:

• It is mainly the total light intensity and the timing (using a bright screen late in the evening) that shift the rhythm, far more than the blue tint alone.
• The Cochrane review found no clear benefit of filtering lenses on sleep. Lowering brightness, switching on night mode and, above all, easing off screens an hour before bedtime acts on the real cause, and costs nothing.

THE RETINA

Blue light and the retina: is there a danger?

The American Academy of Ophthalmology, one of the world’s leading ophthalmology learned societies, is explicit: it does not recommend blue-light glasses and points out that there is no evidence that the light emitted by screens damages the eyes AAO 2021.

In France, ANSES did raise the alarm about a possible retinal phototoxicity of blue light, but in a very specific context: direct, intense and prolonged exposure to blue-rich LED sources (certain types of lighting, headlights, light-up toys), particularly in children, whose lens filters less. This has nothing to do with normal screen use, whose irradiance stays well below hazard thresholds. The caution advised concerns intense lighting sources, not the act of checking your phone.

THE ADVICE

What actually helps against eye strain?

The good news is that the measures that really work are simple, free and grounded in an understanding of the true causes. Here is what an ophthalmologist recommends day to day:

• Take regular breaks. The “20-20-20” rule (every 20 minutes, look at something about 6 metres away for 20 seconds) is a simple cue for relaxing your focusing effort. The evidence for its effectiveness remains modest, but it is a good habit of visual hygiene, with no downside.
• Remember to blink. Blink deliberately, and use artificial tears (tear substitutes) if your eyes are dry: this is the single measure that most relieves screen discomfort.
• Set up your screen. Brightness matched to the room lighting, text large enough, a distance of 50 to 70 cm, and the top edge of the screen slightly below eye level.
• Correct your vision. An unsuitable optical correction is a common and underestimated cause of strain. A refraction test can detect it.
• In the evening, cut back on screens rather than buying glasses: lower the brightness, switch on night mode and, ideally, stop an hour before bedtime.
• See a specialist if symptoms persist: lasting discomfort may point to dry eye, a focusing disorder or a refractive error to be corrected. See also our article on digital eye strain in front of screens.

FAQ

Frequently asked questions

Scientific sources

1. Singh S, Keller PR, Busija L, et al. (Downie LE). Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. Cochrane Database Syst Rev. 2023 Aug 18;8(8):CD013244. PMID 37593770
2. Agence nationale de sécurité sanitaire (ANSES). Effets sur la santé humaine et sur l’environnement des diodes électroluminescentes (LED). Avis et rapport d’expertise. 2019.
3. American Academy of Ophthalmology. Are Blue Light-Blocking Glasses Worth It? / Digital Devices and Your Eyes. 2021.
4. Anbesu EW, Lema AK. Prevalence of computer vision syndrome: a systematic review and meta-analysis (45 studies included; pooled prevalence 66%). Sci Rep. 2023 Jan 31;13(1):1801. PMID 36720986

Further reading

• Dry eye and remote work: recognising and relieving it
• Digital eye strain in front of screens: what really helps?
• Dr Moïse Tourabaly — Ophthalmologist
• Book an appointment at the practice

Paris 13 practice · Tel. 01 45 47 08 11

Disclaimer

This article is for information purposes. A personalised ophthalmological opinion remains essential for any decision concerning your vision.

This article is intended for general information and does not replace a medical consultation. Persistent eye strain may point to dry eye, a focusing disorder or an uncorrected refractive error, all of which require an ophthalmological examination. For any question concerning your vision, consult an ophthalmologist.