How useful are blue light blocking filters?

Blue light blocking filters have, for some time now, been a significant topic of conversation within the optometric profession. There is ongoing research around their use to provide evidence on their effectiveness and benefits. 

A recent Cochrane review on this topic, published in 2023, was conducted to investigate the possible benefits and safety of blue light filtering spectacle lenses on visual performance, macular protection and sleep quality.¹  

The authors of this review collected and analysed all relevant studies to summarise the best available research evidence. 

Overall, the topic of blue light filters remains highly relevant as eye care professionals (ECPs) strive to provide evidence-based care while addressing concerns patients may have about digital eye strain and blue light exposure in the face of the marketing of dozens of products by manufacturer’s purporting to be of significant benefit to patients’ vision and/or eye health and/or sleep quality. 

Current advice as provided by professional bodies 

The Association of British Dispensing Opticians (ABDO) states, with reference to the recent Cochrane review, that ‘there is currently insufficient evidence to generally recommend blue light filters in prescription spectacle lenses’.²  

They have advised that members must exercise professional judgement when recommending blue light filtering spectacle lenses to their patients and that it would be appropriate to make a case that there is strong evidence from a number of robust studies to support the claims made for these products.³ 

The latest guidance from the College of Optometrists³ also makes reference to the recent Cochrane review and its lack of evidence in blue light filtering spectacle lenses performing any better than non-blue light filtering lenses in reducing eye strain associated with computer use or improving best corrected visual acuity (BCVA) or sleep quality.⁴ 

They have gone on to advise that ECPs must prioritise patient care and maintain public trust by ensuring their recommendations are evidence-based. They should avoid misleading statements, and when selling blue light blocking lenses, they should inform patients there is no strong evidence supporting their benefits.  

Clinicians should present information impartially and base clinical decisions on evidence to ensure valid patient consent and avoid mis-selling claims.⁴ 

What is Blue Light And why is it a Concern? 

Blue light is part of the visible light spectrum. Vibrating within the 380 to 500 nanometre range, it has the shortest wavelength and highest energy. About one third of all visible light is considered to be blue light, with sunlight being the biggest source.  

The intensity of the solar blue light spectrum fluctuates during the day, and the human body has evolved to use these differences to keep our circadian rhythm in time with our environment.⁵ Artificial sources of blue light include fluorescent light, LED TVs, computer monitors, smartphones and tablet screens.⁶ 

Some health experts have raised questions about whether artificial blue light could be damaging to the eye. Animal studies have found an association between blue light and phototoxic retinal damage.^{7, 8} 

Use of lighting has undergone significant change over the past decade. There has been an increase in the use of light emitting diodes (LEDs) and fluorescent lighting, which emit higher levels of blue light in comparison to traditional incandescent light sources. 

Additionally, LEDs are also being utilised in the backlit displays of tablets, laptops and computers.⁹ 

Recent research indicates that blue-light exposure from screens is significantly lower than from natural daylight and well within safety limits.  

However, excessive blue light exposure can cause eye strain and disrupt sleep by shifting the circadian phase. Given the widespread use of digital devices, there is concern that blue light exposure may be a public health concern.⁹  

The rationale for introducing blue light blocking ophthalmic lenses was to reduce the risk of retinal damage by blocking and decreasing short wavelength visible light.¹⁰ These devices include spectacle lenses, contact lenses and intraocular lenses (IOLs), which may contain or be coated with a chromophore that absorbs incident short wavelength light.  

The alternative approach is the application of anti-reflective coatings to spectacle lenses surfaces, which selectively reduce the transmission of regions of the violet-blue spectrum.   

It is of note that global manufacturers of mobile phones, tablets and laptops have encouraged the use of night mode screen settings, introduced in the recent years, to reduce the exposure to blue light.  

It is claimed that these settings help users to avoid disruption of circadian rhythm/sleep patterns and improve sleep quality, however there is little evidence for this. At any rate this feature rather negates one of the previous main selling points of blue light filtering lenses. 

There are a range of blue light filtering lenses currently available on the market, including Blue Control (Hoya), Crizal Prevencia (Essilor), Dura vision/ blue protect (Zeiss), BlueGuard (Zeiss), blueEast (Bonastar), Gunnar (Gunnar Optics), Kodak Total Blue (Signet Armolite), Solitaire Protect Balance 2 (Rodenstock), OptiBlue (Optimum), BluV Xpert (BBGR), Lutina (Tokai), StressFree (Swisscoat)1 and doubtless many more. 

Blue light filters tend to work in two ways. Most incorporate an antireflection coating with a blue-violet residual reflex indicating that the lens is reflecting a greater proportion of low wavelength higher energy light.  

This may also be in combination with a pale brown/amber or straw-coloured tint that additionally absorbs a greater proportion of lower wavelength light.  

In a few lenses, such as Tokai Lutina and the new BlueGuard from Zeiss, the lens material itself innately absorbs blue light, as well as also giving UV protection. Like all blue filtering lenses they claim to address digital eye strain while looking better with less noticeable blue-purple reflections.  

Objectives of the Cochrane Review 

Delving deeper into the Cochrane review that the guidance from both ABDO and the College of Optometrists is based on, it was carried out to assess the effects of blue light filtering lenses in comparison to non-blue light filtering lenses for improving visual performance, providing macula protection and improving sleep quality. 

How the Review was Conducted 

The authors of the review only included randomised control trials (RCTs), and in addition to this, only trials which had adult participants.   

Key Findings of the Review 

Overall, this Cochrane review identified 17 eligible RCTs, which compared blue light filtering lenses with non-blue light filtering lenses. 

 The trials in the review had individual study sample sizes which ranged from five to 156 participants and follow up periods ranging from less than one day to five weeks.  

They were conducted across six countries and included diverse study populations, ranging from healthy adults to those with significant health conditions, including bipolar disorder and insomnia. 

Change in visual fatigue or discomfort scores 

The primary findings of the review focused on changes in visual fatigue or discomfort scores. The authors analysed three studies, which aimed to measure how visual fatigue or discomfort changed when using blue light filtering lenses versus non-blue light filtering lenses, with follow up periods ranging from less than one day to five days.  

These studies included both parallel-arm and cross-over designs, with varying participant eligibility criteria: healthy volunteers, symptomatic computer users, and radiology residents. Measurement tools included Likert scales and a visual analogue scale. 

The findings were as follows: 

• Singh et al, 2021,¹¹ reported no significant difference in visual fatigue scores among symptomatic computer users pre- and post-computer task with blue light filtering lenses compared to non-blue light filtering lenses.
• Lin et al, 2017,¹² conducted a trial that included 36 participants, which reported no significant difference between intervention arms for the change in visual fatigue sore.
• A third trial by Dabrowiecki et al, 2020,¹³ including 10 participants, reported no change in average daily visual fatigue scores with blue-light filtering lenses. 

They did not conduct a meta-analysis due to limited quantitative data and the certainty of evidence was downgraded to low due to lack of masking and wide confidence intervals in some studies. 

Change in Critical Flicker-Fusion Frequency (CFF) 

The other primary focus of the review was change in CFF. CFF refers to the frequency at which a regularly recurring change of light stimuli is perceived as steady. Its threshold is often assessed in clinics to evaluate the temporal characteristics of the visual system, making it a common test for eye diseases.¹⁴ 

Changes in CFF were used to evaluate the effectiveness of blue light filtering lenses on visual performance and fatigue. 

The authors reviewed two trials, which reported data related to the change in CFF, with a follow up period of less than one day, using a parallel-arm design. Participants in these trials included healthy individuals and symptomatic computer users. 

The findings were as follows: 

• Singh et al, 2021¹¹ reported no change in CFF with blue light filtering lenses compared to non-blue light filtering lenses.
• The study conducted by Lin et al, 2017,¹² involved 36 participants and described a significant difference between ‘high’ blue light filtering lenses when compared with both ‘low’ blue light filtering lenses and non-blue light filtering lenses. However, quantitative data was not provided. 

They judged the certainty of evidence as low due to inconsistency of results and risk of bias related to masking of participants and personnel. 

None of the 17 trials in this Cochrane review provided data relating to contrast sensitivity, discomfort glare, macular structure changes, colour discrimination or melatonin levels. 

Change in Best Corrected Visual Acuity (BCVA) 

One of the secondary outcomes of the review was changes in BCVA. One cross-over trial within the review by Hammond in 2015, involving 156 bilateral pseudophakic participants measured BCVA in logMAR units without glare conditions. The unit of analysis was a single eye, but the follow up period was unclear. 

They reported that they found no difference in logMAR BCVA between blue-light filtering lenses and non-blue-light filtering lenses. 

The certainty of evidence was judged as moderate, downgraded by one level due to risk of bias, as the outcome assessor was not masked. 

Daytime alertness 

Another secondary outcome of the review was that of daytime alertness. None of the included trials reported the proportion of participants with reduced daytime alertness. However, two studies measured alertness using Likert scale-based questionnaires. 

The findings were as follows: 

• A study by Janku et al, 2020,¹⁵ involving 27 people with insomnia measured the change in daytime alertness using the Hyperarousal Scale (HAS), found no difference in daytime alertness between blue-light filtering and non-blue-light filtering lenses over five weeks.
• A cross-over trial by Knufonke et al, 2019,¹⁶ involving 15 recreational athletes used the Karolinska Sleepiness Scale (KSS) and reported no significant difference in morning and evening alertness scores between blue-light filtering and non-blue-light filtering lenses. It did not report change from baseline or endpoint outcome data. 

The certainty of evidence was judged as very low due to risk of bias and imprecision, with both studies having small sample sizes and lack of masking. 

Sleep quality 

The review also considered the effect of blue light filtering lenses on sleep quality. The authors analysed six studies involving 148 participants with diverse characteristics reported on subjective sleep quality using visual analogue scales or Likert scale-based questionnaires.  

The study populations included recreational athletes, individuals with sleep difficulties, chronic insomnia, bipolar disorder, insomnia and major depressive disorder with sleep onset insomnia; and follow up periods ranged from one to five weeks. 

The findings were as follows: 

• Esaki et al, 2017,¹⁷ carried out a study involving 20 participants with major depressive disorder and sleep onset insomnia and reported no significant difference in sleep quality at a two-week follow up, with blue light filtering lenses compared with non-blue light filtering lenses. 

• Esaki et al, 2020,¹⁸ conducted a study involving 43 participants with bipolar disorder reported no significant difference in sleep quality at a two-week follow up, with blue light filtering lenses compared with non-blue light filtering lenses. 

• Janku et al, 2020,¹⁵ reported no significant difference between blue light filtering lenses compared with non-blue light filtering lenses. Their study involved 27 participants with insomnia, and they measured the change in subjective sleep quality at a six-week follow up, using the Pittsburgh Sleep Quality Index (PSQI). 

• Burkhart & Phelps, 2009,¹⁹ reported significant improvement in sleep quality with blue-light filtering lenses, although they did not report any data numerically. This study involved 20 participants with sleep difficulty and measured the change in subjective sleep quality using a Likert scale. 

• Knufinke et al, 2019,¹⁶ conducted a study involving 15 participants who were recreational athletes, which reported improvement in daily average sleep scores over nine days. 

• Shechter et al, 2019,²⁰ carried out a study involving 15 participants with chronic insomnia symptoms and measured average change in subjective sleep scores over the course of a week. They reported an improvement in subjective sleep with blue light filtering lenses compared with non-blue light filtering lenses. 

The certainty of evidence was judged as very low due to risk of bias, small sample sizes and variable findings. 

Interpretation of Findings 

Dispensing of blue light filtering lenses was reported back in 1996 but this is reported to have been on the rise since 2016.²¹ All of the studies included in the Cochrane review took place after 2010, indicating an increase of publications on this topic due to a growing interest in blue light filtering lenses. 

The review found that there was no reported improvement in visual fatigue when using blue light filtering lenses when compared with using non-blue light filtering lenses.  

Overall, the relatively consistent findings across the studies indicate that blue light filtering lenses may not reduce symptoms of visual fatigue with computer use when compared with using non-blue light filtering lenses. 

There was also no significant difference between using blue light filtering lenses verses non-blue filtering lenses with regards to CFF. 

With regards to BCVA, there was no significant difference reported between blue-light filtering lenses and non-blue-light filtering lenses. The review found that there were different findings reported across the studies for subjective sleep outcome, which the authors stated relates to the highly divergent participant populations across the six trials they reviewed.  

Three of the trials, reporting quantitative data, reported no significant difference in subjective sleep quality when comparing the use of blue light filtering lenses with non-blue light filtering lenses.  

One trial with a small sample size and not reporting quantitative data, reported a small improvement in subjective sleep quality, while two that did not mask participants, reported an average improvement.  

The authors have stated they did not expect these findings, given that computer users are a commonly targeted group of patients that blue light filtering lenses are recommended to. They have further stated the overall body of evidence relating to the use of blue light filtering lenes for the improvement of sleep quality is inconclusive. 

Clinical Relevance 

The authors of the Cochrane review concluded that, based on the research evidence, available at the time, there may not be any clinically meaningful difference in short term subjective visual fatigue scores or CFF when using blue light filtering lenses when compared to using non-blue light filtering lenses. 

They were also highly uncertain whether blue light filtering lenses have any beneficial effect on daytime alertness or sleep quality. 

They were unable to comment on the effect of blue light filtering lenses on contrast sensitivity, discomfort glare, colour discrimination, effects on macular health or serum melatonin levels, as none of the eligible trials evaluated these outcomes. Additionally, there was no clear evidence of any adverse events indicating that blue light filtering lenses may be unsafe to wear. 

Overall, the authors of this Cochrane review reported that their findings did not support the dispensing of blue light filtering lenses for the purpose of reducing visual fatigue or enhancing BCVA. Any potential effects on sleep quality remain unclear because it is not well understood how individuals with various medical conditions may respond differently to the intervention. 

Further to this review, a study by Ganeshrao et al, 2024,²¹ reported that manufacturers’ information, followed by clinicians when prescribing blue light filtering lenses, predominantly shows low to moderate efficacy. 

Palavets & Rosenfield, 2019,²² reported that, at the time of their study, there was a lack of high-quality evidence to support the use of blue light filtering lenses for the purposes of improving visual performance or to alleviate eye fatigue. 

Lawrenson et al, 2017,¹⁰ reported they also found a lack of high-quality evidence to support the use of blue light filtering lenses for the general population to improve visual performance or sleep quality, or to alleviate eye fatigue or conserve macular health. 

Downie, 2017,⁹ stated, although there is plausible rationale for using blue light filtering devices, there is significant debate regarding the effectiveness of these products in providing retinal protection and their other supposed benefits in clinical populations. 

Practical Guidance 

It has been found that 25% of UK and Ireland-based optometrists considered the provision of blue light filtering lenses to be one of the management options for digital eyestrain.²¹  

It has also been reported that the main source of evidence used for the purpose of prescribing blue light filtering lenses for many clinicians may be from advertisements rather than from scientific studies;²¹ and, despite questionable evidence, commercial brands advocate blue light filtering lenses. 

Despite concerns about the long-term safety of backlit LED displays, which emit light in the 460-490nm range, these emissions do not exceed international exposure limits, even with prolonged use. Additionally, the light emitted from these devices is less intense than natural sunlight, even on a cloudy winter day in the UK.¹⁰ 

There is a clear need for clinicians to adopt an evidence-based approach when it comes to the prescribing of blue light filtering lenses.^{3, 4, 9} Additionally, there is a need for high quality studies to address the effects of blue light filtering lenses on visual performance along with the potential alleviation of the symptoms of eyestrain and or visual fatigue, with an agreed set of outcomes.¹⁰ 

A 2024 study by the American Academy of Ophthalmology (AAO) found blue light plays a minor role in digital eye strain. Instead, factors such as prolonged screen time, inadequate lighting, incorrect viewing distance and poor screen ergonomics are more significant contributors.  

Additionally, a 2024 review in the Journal of Optometry concluded that blue light glasses offer minimal benefit for digital eye strain. The review emphasised that taking regular breaks, ensuring proper lighting and improving ergonomics are more effective in reducing symptoms.²³ 

Furthermore, a 2024 review by Harvard Medical School found that blue light-blocking glasses offer only a slight benefit for those who use electronic devices extensively before bed. However, this improvement is negligible compared to the effectiveness of good sleep hygiene practices.  

Adopting habits such as avoiding screen time an hour before bed, maintaining a consistent sleep schedule, and creating a restful sleep environment are more beneficial.²³ 

In terms of recommending blue light filtering lenses at the time of dispense, it is the author’s opinion that we should be following the guidance provided by ABDO and the College of Optometrists. That is that ECPs exercise professional judgement and aim to provide all clinical and dispensing recommendations using an evidence-based approach. 

Given that the findings of this Cochrane review did not support the prescribing of blue light filtering lenses to the general population for the purposes of reducing visual fatigue, enhancing BVA, or improving sleep quality, ECPs should be mindful about the advice that they provide with regards to the potential benefits of these lenses. 

It is unclear from the research as to whether blue light protecting lenses are being compared in the studies to other spectacle lenses similarly incorporating a high-quality antireflection coating or whether they are simply being compared to the subject’s habitual spectacles, which may be an uncoated alternative.  

Similarly, it unclear whether or not the habitual lenses might be photochromic or otherwise incorporate a pale tint indoors, or indeed if any of these factors have been controlled for.   

There is little doubt, providing the lenses are kept clean, most patients prefer the visual performance and cosmetic appearance of anti-reflection coated lenses, and the evidence shows that a reduction of reflections can improve legibility and reduce visual fatigue.²⁴  

Some patients choose to have a pale (category 0) brown or amber tint over a clear lens to help with troublesome bright lights. Although claims of retinal cell death and circadian rhythm disruption has been exaggerated, there are many patients that do still like blue light filtering lenses.  

It is worth bearing in mind that they provide full UV protection and it is our role, as ECPs, to provide a patient with the options available, enabling all patients to make informed choices about there lenses.  

Additionally, although the Cochrane review did not support the prescribing of blue light filtering lenses to the general population for the purposes of reducing visual fatigue, enhancing BVA, or improving sleep quality, there is also no evidence that they do any harm.  

• Michelle Mehta is qualified dispensing optician and contact lens optician who has worked predominantly in multiple high street practice.  She is a theory examiner for ABDO College and has previously been a distance learning tutor for both the dispensing and contact lens courses.  Her previous work has also included working as a professional services consultant. Having joined City, University of London as a visiting clinical tutor, Mehta took on a permanent role as lecturer in optometry and visual sciences at the university in 2023. She is also a CPD facilitator and probationary contact lens examiner for ABDO as well as a member of their Research and Clinical Committee. 

References 

1. 1 Singh, S, Keller, PR, Busija, L, McMillan, P, Makrai, E, Lawrenson, JG, Hull, CC and Downie, LE, 2023. Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. Cochrane Database of Systematic Reviews, (8). 
2. ABDO. C9.3.1 Blue light guidance for ABDO members. https://www.abdo.org.uk/regulation-and-policy/advice-and-guidelines/updates/c9-3-1-blue -light-guidance-for-abdo-members/
3. ABDO. Blue Light Guidance for Members. https://www.abdo.org.uk/wp-content/uploads/2017/12/ABDO-Blue-Light-Guidance-WEB.pdf
4. College of Optometrists. Review finds there may be no benefit using blue-light filtering spectacles. https://www.college-optometrists.org/news/2023/september/review-of-blue-light-filtering-blocking-lenses
5. Cougnard-Gregoire, A, Merle, BM, Aslam, T, Seddon, JM, Aknin, I, Klaver, CC, Garhöfer, G, Layana, AG, Minnella, AM, Silva, R and Delcourt, C, 2023. Blue light exposure: ocular hazards and prevention—a narrative review. Ophthalmology and therapy, 12(2), pp.755-788.
6. How blue light affects your eyes, sleep, and health. https://health.ucdavis.edu/blog/cultivating-health/blue-light-effects-on-your-eyes-sleep-and-health/2022/08
7. Noell, WK, Walker, VS, Kang, BS and Berman, S, 1966. Retinal damage by light in rats. Investigative Ophthalmology & Visual Science, 5(5), pp.450-473.
8. Ham Jr, WT, Mueller, HA, Ruffolo Jr, JJ, Guerry III, D and Guerry, RK, 1982. Action spectrum for retinal injury from near-ultraviolet radiation in the aphakic monkey. American Journal of Ophthalmology, 93(3), pp.299-306.
9. Downie, LE, 2017. Blue-light filtering ophthalmic lenses: to prescribe, or not to prescribe?. Ophthalmic & Physiological Optics, 37(6).
10. Lawrenson, JG, Hull, CC and Downie, LE, 2017. The effect of blue-light blocking spectacle lenses on visual performance, macular health and the sleep-wake cycle: a systematic review of the literature. Ophthalmic and Physiological Optics, 37(6), pp.644-654.
11. Singh S, Downie LE, Anderson AJ. Do blue-blocking lenses reduce eye strain from extended screen time? A double-masked, randomized controlled trial. American Journal of Ophthalmology 2021;226:243–51. 
12. Lin JB, Gerratt BW, Bassi CJ, Apte RS. Short-wavelength light-blocking eyeglasses attenuate symptoms of eye fatigue. Investigative Ophthalmology and Visual Science 2017;58(1):442-7. 
13. Dabrowiecki A, Villalobos A, Krupinski EA. Impact of blue light filtering glasses on computer vision syndrome in radiology residents: a pilot study. Journal of Medical Imaging 2020;7(2):022402. 
14. Muth T, Schipke JD, Brebeck AK, Dreyer S. Assessing Critical Flicker Fusion Frequency: Which Confounders? A Narrative Review. Medicina (Kaunas). 2023 Apr 20;59(4):800. doi: 10.3390/medicina59040800. PMID: 37109758; PMCID: PMC10141404.
15. Janku K, Smotek M, Farkova E, Koprivova J. Block the light and sleep well: Evening blue light filtration as a part of cognitive behavioral therapy for insomnia. Chronobiology International 2020;37(2):248-59. 
16. Knufinke M, Fittkau-Koch L, Møst EI, Kompier MA,Nieuwenhuys A. Restricting short-wavelength light in the evening to improve sleep in recreational athletes - A pilot study. European Journal of Sport Science 2019;19(6):728-35. 
17. Esaki Y, Kitajima T, Takeuchi I, Tsuboi S, Furukawa O, Moriwaki M, et al. Effect of blue-blocking glasses in major depressive disorder with sleep onset insomnia: a randomized, double-blind, placebo-controlled study. Chronobiology international 2017;34(6):753-61. 
18. Esaki Y, Takeuchi I, Tsuboi S, Fujita K, Iwata N, Kitajima T. A double-blind, randomized, placebo-controlled trial of adjunctive blue-blocking glasses for the treatment of sleep and circadian rhythm in patients with bipolar disorder. Bipolar Disorders 2020;22(7):739-48.
19. Burkhart K, Phelps JR. Amber lenses to block blue light and improve sleep: a randomized trial. Chronobiology International 2009;26(8):1602-12. 
20. Shechter A, Kim EW, St-Onge MP, Westwood AJ. Blocking nocturnal blue light for insomnia: a randomized controlled trial. Journal of Psychiatric Research 2018;96:196-202. 
21. Ballae Ganeshrao, S, Theruveethi, N and Srinivasan, K, 2024. Knowledge, perception and practice towards blue-blocking lenses among optometrists. Clinical and Experimental Optometry, 107(3), pp.332-340.
22. Palavets, T and Rosenfield, M, 2019. Blue-blocking filters and digital eyestrain. Optometry and Vision Science, 96(1), pp.48-54.
23. The Truth About Blue Light Computer Glasses: Are They Worth the Hype? BYNOCS – technology for superior vision. https://www.bynocs.com/truth-about-blue-light-computer-glasses/
24. Y-T Lin, P-H Lin, S-L Hwang, S-C Jeng and Y-R Lin. Ergonomic evaluation of electronic paper: Influences of anti-reflection surface treatment, illumination, and curvature on legibility and visual fatigue, Journal of the Society for Information Display, vol. 16, no. 1, pp. 91-99, January 2008.