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Update on Irlen Lenses


There is much controversy when it comes to whether Irlen/Scotopic Sensitivity Syndrome (IS or SSS) exists or not and if its proposed treatment of coloured filters is effective for treating reading difficulties.

Irlen Syndrome is described as a perceptual condition where individuals experience sensitivity to certain wavelengths of light thus causing reading-related visual stress. The elimination of those wavelengths using coloured lenses or overlays while reading are the basis for treatment of IS, which is proposed to alleviate visual stress and make reading less difficult.1

Optometrists are hesitant to jump on board with diagnosing IS as they believe there is an underlying vision deficit that is contributing to the reading difficulties, of which can be treated by proper lenses, prisms, and/or vision therapy. The described symptoms of IS are very similar to those symptoms associated with accommodative, binocular vision, and ocular motility disorders (such as fatigue, words moving on the page, etc.). Supporters of IS stress that it is a distinct condition separate from vision problems that could be diagnosed during a visual examination. They propose that although IS and visual problems may have similar symptomatology, similar symptomatology may have dissimilar etiology. They believe that those with IS have a dysfunction of the major visual pathways in the brain which are unrelated to vision problems.1

The Irlen Institute states that all clients receive comprehensive assessment of their visual system, and if any vision problems are found they are treated prior to testing for IS.1 But a study performed by Scheiman et al reported that 95% of subjects identified as being a good candidate for Irlen lenses also had a readily identifiable vision anomaly. There were 57% of those Irlen candidates that reported they had an eye examination within a year of the study, and yet in 90% of those subjects it was found that they had significant uncorrected visual efficiency problems. This suggests that the appropriate testing to identify oculomotor, accommodative, and binocular vision anomalies had not been carried out during those examinations.2

Much of the controversy around IS and the treatments they suggest stems from the lack of validity of the research they provide. Irlen has only one published article7 in a scientific journal, with much of her other work8 being found in newspapers and non-published journals5. Systematic reviews of the studies on coloured filters and reading disabilities suggest that the existing research is inconclusive and not sufficient to direct current treatment of learning disabilities.5, 6 There is a need for long-term randomized control trials with appropriate placebo and masking.5

A recent, well designed study addresses these concerns and completed the first investigation of Irlen colored overlays in which the participants had no explicit knowledge of their prescribed color before being tested (masked) with an adequate sample size to make valid conclusions. Their results suggested that Irlen coloured overlays had no immediate effect on children with reading difficulties, even in those who had been diagnosed with IS.3

It is important for full eye examinations of those identified with learning difficulties to specifically look at whether there are any visual deficits in the areas of ocular motility (saccades or pursuits), accommodation, binocularity and/or depth perception, and that the appropriate treatment be carried out. It may be that a large proportion of those with reading difficulties that also have vision deficits that have not been appropriately detected and managed by optometrists and thus have turned to the Irlen treatment approach for help that they failed to receive otherwise.1

In another study by Blaskey, Scheiman et al, it showed that the subjects’ use of Irlen filters had a reduction in visual symptoms (increase in comfort), but all 11 of the subjects still had clinically significant vision anomalies after treatment with the filters. Whereas in the vision therapy treatment group, where the subjects also reported significant improvement in comfort after vision therapy, the subjects were no longer considered candidates for Irlen filters, suggesting that the optometric intervention alone was sufficient for treating the symptoms. There was a subdivision of the vision therapy group (two subjects) that reported they received additional benefit from coloured lenses after their visual anomalies have been treated by vision therapy.4

It seems that the general consensus from an optometric viewpoint is that it is critical for those identified with reading difficulties to be properly assessed for any visual anomalies before considering diagnosing IS and the prescribing of Irlen filters or overlays. It is highly possible that appropriate glasses, prism, and/or vision therapy for people with visual efficiency deficits will alleviate their visual symptoms, thus improving concentration and efficiency while reading. There may be an additional benefit for a select group of people with use of coloured lenses after having been treated with glasses and vision therapy, but it is critical to diagnose and manage the underlying vision problem prior to taking this controversial approach.

It is therefore important, for those with reading difficulties, to be properly examined by an optometrist, to determine the etiology of their reading difficulty. A referral to a developmental optometrist may be required.  A developmental optometrist spends years in post- doctoral education to master the diagnosis and treatment of visual efficiency and visual perceptual disorders through therapeutic glasses, prisms and vision therapy. Recent studies9, 10, 11 on vision therapy have shown that there is great remediation in visual efficiency symptoms when vision therapy is used to treat convergence insufficiency and accommodative dysfunction. Not only do symptoms improve, but their clinical measures of accommodation and binocular vergence, greatly improve if not normalize after the visual therapy program. These treatments usually alleviate the majority of visual symptoms and improve reading ability and efficiency in patients with reading difficulties. If there are no detected vision anomalies or there are residual symptoms after optometric treatment, the phenomenon of IS could be considered and if indicated, coloured lenses may be prescribed for increased relief of symptoms.

By Debbie Luk, BSc(Hons), OD, FCOVD, and Shannon Pennifold, BSc.


1 Irlen HL, Scheiman M. Scotopic sensitivity syndrome, Irlen filters and reading disability. Journal of Behavioral Optometry 1994: 5;31: 62-66.

2 Scheiman M, Blaskey P, et al. Vision characteristics of individuals identified as Irlen filter candidates. Journal of the American Optometric Association 1990: 600-604.

3 Ritchie SJ, Sala SD, & McIntosh RD. Irlen colored overlays do not alleviate reading difficulties. Pediatrics 2011: 128; e932.

4 Blaskey P, Scheiman M. The effectiveness of Irlen filters for improving reading performance: a pilot study. Journal of Learning Disabilities 1990: 23: 604-610.

5 Albon E, Adi Y, Hyde C. The Effectiveness and Cost-effectiveness of Colored Filters for Reading Disability: A Systematic Review. Birmingham, United Kingdom: University of Birmingham Department of Public Health and Epidemiology; 2008.

6 Dohnert M, Englert ED. The Irlen syndrome--are there pathophysiologic correlates and scientific evidence for "reading with colors"? Z Kinder Jugendpsychiatr Psychother 2003; 31(4):305-309.

7 Irlen H, Lass MJ. Improving reading problems due to symptoms of scotopic sensitivity syndrome using Irlen lenses and overlays. Education 1989; 109(4):413-417.

8 Irlen, H. Successful treatment of learning disabilities. 1983, paper presented at the 91st Annual Convention of the American Psychological Association, Anaheim, California.

9 Convergence Insufficiency Treatment Trial Study Group. Randomized clinical trial of treatments for symptomatic convergence insufficiency in children. Arch Ophthalmol 2008;126(10):1336-1349.

10 Lavrich JB. Convergence Insufficiency and its current treatment. Current Opinion in Ophthal 2010; 356-360.

11 Convergence Insufficiency Treatment Trial Study Group. Treatment of accommodative dysfunction in children: results from a randomized clinical trial. Optom Vis Sci 2001; 88:1343-1352.

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