Blue light and BlueBlock glasses: what does the research show?

When you buy glasses, you are often offered protection against blue light. The promise is appealing: less tired eyes, protection for your vision and better sleep. But measuring how much light a lens filters does not prove that it delivers all those benefits.

At Relenser, we do not support charging extra for products sold through fear rather than good evidence. For ordinary screen use, research does not justify the claim that you need a clear BlueBlock filter to protect your retina. Benefits for short-term eye strain have not been convincingly demonstrated. When it comes to sleep, we need to distinguish almost clear coatings from strongly tinted evening glasses.

This does not mean that all blue light is harmless in every situation. Intensity, duration and timing of exposure matter. So let us look at what the studies actually measured and what we can conclude from them.

If blue light is not the culprit, why do our eyes hurt after work?

After eight hours at a screen, our eyes are tired, and we still use our phones in the evening. If an extra coating could protect our sight, why would we save money on it?

The problem lies in the promise and the proposed cause. Prolonged close work places demands on focusing, while screen use often involves less frequent or incomplete blinking. This can contribute to tired and dry eyes. Discomfort does not, by itself, mean retinal damage. A blue-light filter does not remove the need to focus or improve blinking.

The symptoms are real. Burning eyes, a gritty feeling, occasional blurred vision and headaches are not imaginary. But the fact that they occur during computer work does not tell us what causes them.

During close work, the eyes must adjust their focus and work together to look at the same object. Maintaining this for hours can be demanding. An unsuitable prescription, small text or glare can make matters worse. Sheppard and Wolffsohn, 2018: digital eye strain

We also tend to blink less or fail to close our eyelids completely when using a screen. The tear film is then renewed less effectively. Add air conditioning blowing towards your face and there is a plausible explanation for dry, irritated eyes. A blue-light filter does not correct the wrong prescription or make you blink fully. AAO EyeWiki: digital eye strain

What exactly is blue light?

Visible light consists of different wavelengths, which we perceive as different colours. The blue part of the visible spectrum is usually described as approximately 400 to 500 nanometres.

Blue light comes from the sun, lamps and screens. Phones and computers did not introduce a new kind of radiation. Part of the light they emit belongs to the same visible spectrum we encounter outdoors.

O'Hagan and colleagues compared light sources, including screens and blue sky. None of the screens tested came close to the exposure limit used in their assessment. O'Hagan et al., 2016

Why, then, is there so much talk of “high-energy blue light”?

Because a single photon of blue light carries more energy than a photon of red light. That is physically correct. But assessing a hazard also requires information about intensity, exposure duration and how much light reaches the tissue. The label “high-energy” does not establish that a computer is dangerous.

What have studies of blue-light glasses found?

A 2021 study examined 120 people with symptoms of digital eye strain. It was randomised and double-masked: participants and researchers assessing the outcomes did not know who was wearing which filter. Blue-light filtering did not produce a statistically significant improvement in symptoms compared with clear control lenses. Singh et al., 2021

A broader picture comes from the 2023 Cochrane review, which included 17 randomised studies involving 619 people. It found that blue-light filters may not reduce eye strain over short-term follow-up compared with lenses without the filter. Evidence about sleep was uncertain; the included studies did not establish long-term retinal protection. Cochrane, 2023

The UK's College of Optometrists also states that there is no strong evidence that blue-light filtering improves visual performance, reduces eye strain or improves sleep. Professional position statement

What about studies in which blue light damages the retina?

Such studies do exist. With sufficiently intense or prolonged exposure, light can cause damage in a laboratory. But we need to examine whose eyes were exposed and how.

In a 2021 study, Sánchez-Ramos and colleagues used 36 rats. Six tablet screens surrounded the exposed groups' cages, approximately 10 centimetres from the cage walls. The screens were on for 16 hours a day over three months, followed each day by eight hours of darkness. One group was exposed to screens without filters, another to screens with Reticare filters, and a third was not exposed to screens. The filtered group showed fewer of some signs of retinal damage. Sánchez-Ramos et al., 2021

That is a result in rats under those conditions. Someone working at a computer does not have six screens surrounding their head at a distance of 10 cm. Rat and human eyes also differ in structure. Moreover, the researchers tested a film over the screens that changes the spectrum and amount of transmitted light, not a clear coating on spectacle lenses.

The experiment can therefore inform further research. It does not establish that using a phone causes retinal disease in humans or that paying extra for BlueBlock at an optician prevents it.

What about sleep? Here the story is different

Light helps regulate our internal clock. Evening light can suppress the evening rise in melatonin and delay the body's preparation for sleep. Daylight, meanwhile, is a normal and important signal for alertness and the timing of our daily rhythm. Brown et al., 2022: light, the body clock and sleep

Our eyes contain cells that signal day and night to the body. They are particularly sensitive to the blue-turquoise part of the spectrum, around 480 nanometres. A lens may block substantial light in another part of the blue spectrum while only slightly reducing the signal to the body clock in the range to which these cells are sensitive. Glickman et al., 2025, Table 1

In 2025, Glickman and colleagues compared 26 glasses or filters. From their spectral properties, they calculated how much they reduce light weighted for its relevance to the circadian system. If the starting amount of this weighted light under standard daylight illumination is represented as 100 units, approximately 90 passed through Essilor's Crizal Prevencia lens, marketed as a blue-light filtering lens, while about four passed through the orange UVEX SCT-Orange filter. That corresponds to reductions of approximately 10% and 96%, respectively. Glickman et al., 2025, Table 1 The visual difference is obvious: one lens is almost clear, the other strongly orange.

The shared label “blue-light glasses” conceals this difference. Results from studies of strongly orange evening glasses cannot be used as proof that an almost clear coating on everyday glasses will improve sleep.

But 96% less of this weighted light does not mean 96% better sleep. This comparison describes filtering. The body's actual response also depends on the initial light level, timing and duration of use. Brown et al., 2022

Some small studies of strongly tinted evening glasses report benefits. However, a 2025 review of objective sleep measurements, covering three studies with 49 participants, found no statistically significant improvement in time to fall asleep or total sleep time. The data were limited and the estimates imprecise. Luna-Rangel et al., 2025

Light's effect on melatonin therefore does not establish that an ordinary clear coating improves sleep. A practical first step is to reduce bright evening lighting and screen brightness. Warmer screen colours can be part of that adjustment, but they do not guarantee good sleep. Brown et al., 2022 You can enable night mode on your devices or use software such as f.lux.

Sales claims worth questioning

Certain ways of persuading people recur in the sale of blue-light filters. In each case, it is worth asking what the demonstration or research actually establishes.

1. A major threat

If a screen is presented as something that damages your eyes, an extra filter becomes almost automatic. Who would not pay another €30 to avoid damaging their sight, especially when children are involved?

Lens manufacturers' catalogues list computers, phones and tablets among sources of blue light. They also discuss possible long-term eye damage from excessive exposure. This places the extra coating within a story of danger and protection. Essilor: Crizal catalogue, Crizal Prevencia / Crizal for Kids sections

The key word is “excessive”. The fact that excessive exposure can be harmful does not establish that ordinary screen use involves that level of exposure. What matters is what was actually measured. Six tablets around a cage, shining for 16 hours a day, are not the same scenario as normal computer use.

2. A demonstration that shows filtering but sells health

If a salesperson shows that less light of a particular colour passes through a lens, the demonstration can be real.

But it has not measured eye strain, sleep or effects on the retina. It has only shown filtering. Health benefits require relevant clinical evidence, with independent confirmation being particularly valuable.

3. A percentage without an explanation

“Blocks up to 40% of blue light” sounds precise. What may be less clear is whether the percentage refers to the whole blue spectrum, a narrow section or a single wavelength. The comparison used also matters.

Two similar percentages can therefore describe different lenses. Even an accurate measurement of filtering does not imply the same percentage reduction in health risk. To make that claim, we would need to know the initial risk and show that the product changes it. Rampersad and Carlson, 2024

4. “Clinically proven” without evidence supporting the promise

This is not merely a theoretical concern. In July 2022, the UK's Advertising Standards Authority upheld a complaint about an advert for Gamer Advantage blue-light glasses. The advert claimed clinically proven sleep benefits through an effect on melatonin. The ASA found that the submitted evidence, including a master's thesis and scientific posters, was insufficient. The advert could not appear again in that form. ASA ruling, 27 July 2022

Who pays for the research, and why does it matter?

Manufacturers can fund good-quality research. Their involvement does not, by itself, mean the data are wrong. But we should know who funded the work, who designed the experiment and who has a commercial interest in positive findings that help sell lens extras.

The literature provides several specific examples worth knowing about.

JINS and the eye-strain study. Lin and colleagues' 2017 study involved 36 people. The stronger filter produced a more favourable result in a flicker-detection test and in some symptoms. The paper discloses that JIN/JINS supplied the lenses, prepared the randomisation schedule and arranged investigator masking for the lenses. The company also provided funding; two authors disclosed financial or consultancy relationships. Lin et al., 2017

That is a substantial role in conducting the study. It is not proof of manipulation, but a small positive result needs to be considered alongside the study's limitations and other research, including the larger trial that did not confirm a benefit. Singh et al., 2021

Essilor and the study of involuntary eyelid closure. In 2023, Monschein and colleagues tested Crizal Prevencia lenses in people with blepharospasm, a disorder involving involuntary contractions of muscles around the eyes that close the eyelids. Researchers counted blinks under different conditions, including reading and resting. Participants wore the filtering and control lenses in sequence, for two weeks each. Of 24 people enrolled, 15 were included in the final analysis.

The results were mixed. In four of the six test conditions, participants blinked less with the filter than with the control lenses. But when compared with their baseline before trying the glasses, there was no statistically reliable improvement. The filter performed better than the control in some measurements, without establishing improvement over the starting condition.

A further limitation is the number of comparisons. The more outcomes you test, the greater the chance that one will appear favourable by chance. Statistical analysis can account for this by requiring stronger evidence of a positive finding. The researchers did not make such an adjustment because they treated the study as exploratory. Monschein et al., 2023

That does not mean the favourable results were necessarily accidental. It means they are a signal that needs confirmation in a larger, well-designed study. And the study concerned a specific eyelid disorder, so its results cannot establish that the same filter helps ordinary computer-related eye strain.

The paper discloses Essilor's funding and states that the company was not involved in study design, analysis or writing. Monschein et al., 2023, Funding The crucial point is that research into a specific disorder cannot serve as general evidence for office workers.

Reticare and the rat experiment. In the experiment described earlier, the exposure conditions matter. Before the experiment, the rats spent 14 days in darkness. Six tablets with white displays at maximum brightness then surrounded the exposed groups' cages, approximately 10 centimetres from the cage walls. The screens were on for 16 hours a day over three months, followed by eight hours of darkness each day.

This is prolonged exposure from all four sides of a cage. It cannot simply be equated with a person using a computer or phone. The authors themselves describe the 16-hour light / eight-hour dark cycle as more aggressive than the 12-hour cycle used in an earlier study. The result shows an effect of the filter in rats under those conditions; it does not establish that people need protective glasses for ordinary screen use. Cells paper: methods and discussion

There is also a commercial connection. The study tested a Reticare screen filter, while the paper states that it received no external funding and that the authors had no conflicts of interest. On its website, the company describes Celia Sánchez-Ramos, the paper's first author, as its co-founder and scientific director. Paper disclosures, Reticare's company page

We are not claiming that all industry-funded research is invalid. The problem arises when a small study or indirect evidence is presented as conclusive proof to justify an extra charge, even though it does not support that conclusion.

What can actually make screen work more comfortable?

An accurate prescription and lenses suited to your working distance are important foundations. Breaks are a useful habit, but cannot replace glasses you need.

Take regular breaks from close work. The 20–20–20 rule is a practical reminder: roughly every 20 minutes, look at something at least 20 feet (six metres) away for 20 seconds. It is not a magic formula in which every number must be exact. A study of 29 users found that reminders reduced symptoms but did not improve most objective signs of dry eye. The ideal timing and duration of breaks have not been firmly established. Talens-Estarelles et al.

Remember to blink fully. Occasionally close your eyelids gently and completely while working. If symptoms persist, the tear film and eyelids may need assessment; not every feeling of dryness has the same cause. Sheppard and Wolffsohn, 2018

Choose a comfortable viewing distance. Text should be large enough to read without leaning forward. A larger screen can make working at a greater distance easier, but there is no single best distance for everyone. Consider text size, your work and the glasses you use.

Adjust your workspace. Enlarge text so you do not have to lean towards the screen. Reduce distracting reflections, match brightness to the room and avoid air blowing directly into your face. The aim is comfortable viewing, not making the screen as dark as possible at all costs. Sheppard and Wolffsohn, 2018

Check your prescription and working distance. Distance, reading and computer glasses are not always interchangeable, particularly when near vision becomes difficult. Suitable correction for the actual working distance is an important part of comfortable computer use. AAO EyeWiki: causes and management

For children, make time outdoors too. More time outdoors is associated with a lower risk of developing short-sightedness. It does not treat an existing prescription, but it is a more relevant topic for discussing children's habits than automatically paying extra for a blue-light filter. Rose et al., 2008

Recurring pain, blurred vision or other symptoms call for an eye examination. Labelling persistent problems “blue light” does not resolve them.

Why Relenser does not recommend this extra as essential

We sell lenses too, and make our living from them. Our principle is to advise customers as we would advise our own mothers. That is why we do not support charging extra for an almost clear filter on the basis of screen-protection claims that research does not support.

Apply the same critical standards to us. That is why we link our claims to sources and explain the limitations of the studies.

Some people prefer lenses with a blue light filter, so we offer that option too. Personal preference is different from proven medical necessity. We do not recommend it as essential protection from screens.

If you have questions, contact us. We will help you choose lenses based on your prescription and the distances you work at. Explore replacement lenses for your existing frames.