From The College of Optometrists Journal Acuity, May 2026
Are coloured overlays really effective for treating visual stress?
1 May 2026
Adrian O'Dowd examines the evidence on the use of coloured overlays and how the profession should approach visual stress.
Visual stress is a controversial topic within optometry, particularly regarding its management and whether specific qualifications should underpin the use of coloured overlays.
Visual stress describes visual–perceptual symptoms triggered by text or high-contrast patterns, rather than a refractive or ocular pathology. Its neurophysiological basis is not fully understood. Symptoms may include visual discomfort, distortion of text, headaches and reading fatigue (Wilkins, 2002; 1995).
Previously termed Meares–Irlen syndrome, Irlen syndrome or scotopic sensitivity syndrome, the condition is now more commonly referred to as visual stress, reflecting a shift away from implying a specific causal mechanism (SASC, 2025; Irlen, 1991; Meares, 1980).
Coloured overlays and precision tints may provide symptom relief for some people, but evidence for their routine clinical use remains mixed (Howard-Jones, 2014; Stein, 2014; Wilkins, 2002). Any intervention should be approached cautiously, with clear communication about the limits of current evidence and appropriate professional training (Suttle and Conway, 2025).
Visual stress
As many as 15% to 20% of individuals with dyslexia report symptoms consistent with visual stress, although prevalence varies widely depending on diagnostic criteria and study design (Evans and Allen, 2016; Loew et al, 2015). Higher rates of visual stress symptoms have been reported in some groups, including those with autism; however, visual stress is not considered a core feature of autism, and the strength of association remains debated. Evidence regarding any association with attention deficit hyperactivity disorder is limited.
Visual stress is believed to be made worse by environmental factors such as lighting, glare, high contrast, flicker and colours. But how to help these people has led to much professional debate.
One way of trying to help a person with visual stress is by using coloured overlays. These are sheets of translucent or transparent coloured plastic placed over a page of a book or screen to colour the text beneath without interfering with its clarity. A similar approach is to use tinted lenses (Albon et al, 2008). But these techniques have proved controversial.
Don’t over-egg the evidence
Coloured overlays and precision-tinted lenses remain a debated area within optometric practice. While some clinicians report meaningful symptomatic benefit in selected patients with visual stress, systematic reviews have concluded that the evidence base is limited and methodologically variable, with inconsistent findings across studies (Uccula et al, 2014; Hyatt et al, 2009; Wilkins et al, 1994). Assessment typically involves measuring reading speed and subjective comfort while trialling different chromatic filters, often using validated tools such as the Wilkins Rate of Reading Test and, in some cases, the Intuitive Colorimeter (Griffiths et al, 2016; Smith and Wilkins, 2007; Wilkins et al, 1996). These services are not included within the NHS General Ophthalmic Services eye examination and are usually provided privately (British Dyslexia Association, 2026). Given the ongoing uncertainty regarding mechanism and efficacy, practitioners should exercise clinical judgement, ensure appropriate differential diagnosis, and communicate clearly with patients about the current limits of evidence.
Research into the validity of using coloured filters has not yet reached a firm conclusion (Suttle and Conway, 2025; Harkin et al, 2025).
A leading review concluded that individually prescribed coloured filters had been shown to improve reading performance in people with visual stress, but said larger and rigorous randomised controlled trials of interventions were needed (Evans and Allen, 2016).
Key messages for optometrists interested in providing or recommending coloured overlays
Always complete a full eye examination first to avoid any misdiagnosis
Select candidates carefully and discuss evidence openly
Ensure appropriate training and supervision
Separate visual stress assessments from eye examination visits
Offer overlays or tints at minimal cost
Follow College guidance to avoid complaints or misinformation
Evidence base
One of the authors of this review, Professor Bruce Evans FCOptom, Director of Evans Optometric Consultancy and Visiting Professor at City St George’s, University of London and at London South Bank University, notes that evidence suggests some individuals require a precisely defined colour to achieve benefit. He argues that the controversy reflects mixed evidence rather than disproval, and that evidence-based practice does not preclude helping patients – provided clinicians are transparent about limitations in the data.
He says: “Evidence-based practice does not mean that clinicians should refuse to have anything to do with these topics. Rather, clinicians should still seek to help their patients, but with clear explanations of where the evidence is not strong.”
Subsequent studies have cast doubt on the specificity of colour effects. A randomised trial of 29 patients with diagnosed visual stress found improved reading speed and comfort with tinted lenses, but no significant difference between optimal and suboptimal tints (Suttle and Conway, 2025). A systematic review of 51 studies similarly concluded that coloured overlays and lenses could not be endorsed as an evidence-based intervention, with reported benefits potentially explained by placebo, practice effects or the Hawthorne effect, where the act of being observed by the experimenter may enhance performance (Griffiths et al, 2016; Sedgwick and Greenwood, 2015).
One of the authors of the Griffiths et al (2016) review, Professor Brendan Barrett MCOptom, Professor of Visual Development at University of Bradford, remains unconvinced. “There are many, many positive testimonies from patients and witnessed accounts from practitioners, but this is not the same as published evidence and so there has to be a strong chance that a big element of the ‘effect’ is placebo.”
Farah Awan MCOptom, who dispenses coloured overlays, acknowledges the lack of conclusive evidence. “There’s not enough of an evidence base, but the difference that it makes to people’s lives can be very powerful and rewarding,” she says.
Others urge caution before dismissing the approach. Professor Arnold Wilkins, Emeritus Professor at the University of Essex, argues that the evidence base is still evolving and that high-quality randomised trials take time to complete. “We have been gradually accumulating science. This takes time, patience, patients, skill – and a thick skin!”
Qualification-worthy?
Dr Miriam Conway, Associate Professor at City St George’s, University of London, stresses the importance of maintaining an objective, evidence-informed position. “If you look at Wilkins’, and Evans and Allen’s studies, they say precision tints are definitely working, but we found the opposite [Wilkins, 2018; Evans and Allen, 2016]. It is important to maintain an objective, evidence-informed stance on this issue until a substantial body of research emerges in either direction.”
Debate also runs hot on whether an official qualification in the use of coloured overlays and tinted lenses should be developed for optometrists. Unlike accredited qualifications in low vision or glaucoma monitoring, no regulated qualification currently exists, although training is available through organisations such as Cerium Visual Technologies and Visual Stress Consultancy.
Brendan says a formal qualification would be inappropriate, arguing that it could lend undue credibility to a practice with an insufficient evidence base and would require legislative change: “Dedicating a qualification to it could be seen as giving kudos to an area of practice that is not evidence-based, though it is not without its advocates and proponents.”
There are many positive patient testimonies and witnessed practitioner accounts, but this is not the same as published evidence
Clinical Adviser for the College Daniel Hardiman-McCartney MBE FCOptom emphasises professional competence rather than qualifications alone. “A clinician’s legal entitlement to provide a service is not sufficient justification for commencing practice in a new clinical domain.” He stresses that legal scope of practice does not equate to clinical readiness and that optometrists must undertake appropriate training, critically appraise evidence and gain supervised or mentored experience before offering any new service.
Farah agrees that training is important: “It would be helpful for people dispensing overlays to have training to identify suitable candidates who would benefit from the overlays. Training delivered by clinicians together with industries supplying the technology would lead to consistency in approach and strengthen the credibility of outcomes.”
The number of optometrists offering visual stress assessments is unclear, although estimates suggest it is a significant minority. Daniel estimates that “at least 200 UK practices provide some form of colorimetry or coloured overlay assessment for visual stress”.
Some clinicians have chosen to suspend offering overlays. Miriam says: “We have stopped offering this service while we continue to review the scientific evidence base regarding its effectiveness.”
Experiences and ethics
Despite uncertainty in the evidence base, some practitioners report strong positive patient experiences. Farah describes working in both independent practice and a university visual stress clinic, where she has seen patients and parents report meaningful improvements.
She stresses that careful candidate selection is crucial. She also describes prescribing overlays for her niece during adolescence, which coincided with improved academic performance. “Once I prescribed the overlays, her academic achievement went through the roof.” Her niece reports “overlays allowed me to better understand and retain information” and is now a successful engineer. Although anecdotal, such accounts help explain why the practice continues to attract advocates.
Ethical concerns centre on professional credibility, patient expectations, and cost. Brendan warns that exaggerated claims and high fees risk undermining trust in optometry. “Overlays or coloured lenses may appear to help and if they do, then okay, issue them, but don’t over-egg the evidence, which is extremely weak at present, and don’t attempt to make money from this practice when we can’t verify or explain its clinical use.”
Brendan argues: “Overlays or tinted lenses should always be offered at minimal cost to patients. The practice of issuing high-cost lenses which have a ‘special tint’ is, in my view, bordering on unethical.”
Role of schools
Use of coloured overlays in schools appears to be increasing, with some teachers recommending referral to special educational needs coordinators (SENCOs). Sales data suggest a sustained rise in overlay provision to schools over several years (Wilkins, 2018).
Bruce says that optometry should play a central role, noting that children using overlays via informal routes may have uncorrected refractive or ocular problems requiring professional assessment. “This is why I have always stressed that if children are to use coloured filters, then it is better that these are provided through eye care professionals than by lay people.”
Arnold supports closer collaboration between optometric practices and schools. He says: “It would be useful for optometric practices to liaise with schools to formalise the provision of coloured overlays via trained individuals. The provision of tints is more complex and requires optometric professionals with more extensive training.”
As interest in visual stress grows, unregulated providers have increasingly offered assessments, often outside clinical settings, including online. Daniel says: “Coloured overlay assessments for visual stress are not a regulated activity, which means that, in principle, they can be offered by anyone. The College is frequently contacted by teachers who have encountered third-party companies proposing to undertake such assessments in schools or community settings, despite not being qualified optometrists.”
Concerns have been raised about exaggerated claims made by some providers. In some instances, unregulated businesses have made unsupported assertions about the impact of coloured overlays. The Advertising Standards Authority (ASA) has upheld complaints against misleading advertising, including claims linking dyslexia causally to visual stress, or promising academic improvement: for example, increasing A-level outcomes by at least two grades following use of overlays on one website (ASA, 2022). Such rulings highlight the importance of accurate communication and clinical oversight (COptom, 2022). “These providers are often well intentioned, but many lack an understanding of the evidence base and are not registered healthcare professionals,” Daniel says.
Communication advice for dealing with the public when this service is offered
Explain clearly what assessment involves
Outline the mixed evidence base and uncertain benefits
Signpost patients or carers to independent information
Be transparent about costs and duration
Refer school-age patients to SENCO where appropriate
© iStock
Best practice
College guidance advises a clear separation between visual stress services and the NHS sight test (COptom, 2026).
Daniel says: “Our view is that there should be clear separation between this and core optometry and the NHS eye test.
“Where an optometrist chooses to provide assessments or interventions for visual stress, they must ensure absolute clarity and consistency in their communications. They must ensure a valid consent, including providing all materially important information to parents, so that sufficient information is communicated in a way that can be understood. Claims regarding potential benefits must be appropriately evidence-based, accurately framed and proportionate. It should be made clear to patients, parents and educators that the evidence base remains mixed.”
Until more robust evidence emerges, debate around visual stress and coloured overlays is likely to continue. A cautious, transparent and patient-centred approach remains essential.
References
Advertising Standards Authority. (2022) ASA ruling on Fred Templeman and partners t/a Templeman Opticians (accessed 21 January 2026)
Albon E, Adi Y, Hyde C. (2008) The effectiveness and cost-effectiveness of coloured filters for reading disability: a systematic review. West Midlands Health Technology Assessment Collaboration. Department of Public Health and Epidemiology (accessed 16 February 2026)
British Dyslexia Association. (2026) Neurodiversity and co-occurring difficulties (accessed 21 January 2026)
COptom. (2026) Knowledge, skills and performance (accessed 21 January 2026)
COptom. (2022) Clinical files (accessed 16 February 2026)