Scotopic sensitivity syndrome, also known as Irlen Syndrome , approximating in some ways to Meares Irlen syndrome, and 'Visual Stress', refers to visual perceptual disorder(s) affecting primarily reading and writing based activities. Its existence is not recognized by some major medical organizations including the American Academy of Pediatrics, the American Academy of Ophthalmology, and the American Optometric Association. However, it is fair to say that it does enjoy recognition amongst a respected body of medical opinion, and has been recognised in American States and Australia, and has been studied extensively in leading research centres, including the former Applied Psychology Unit, Cambridge, UK. The Scottish Parliament has also funded a research and treatment centre at the Glasgow Caledonian University.
Irlen syndrome is sometimes categorised as a form of dyslexia. However, bestselling autistic author, Donna Williams, in her book Like Colour To The Blind wrote about her experience of tinted lenses after being diagnosed with scotopic sensitivity. In this book she described the lenses as enabling her to have cohesive, unfragmented vision, able to see faces, bodies and objects as a whole for the first time and reducing the extremity of experiences such as meaning-blindness, face blindness, inability to learn to read facial expression and body language and the social consequences of these impairments. This led to a worldwide raised awareness of scotopic sensitivity as a sensory perceptual problem common in many (but not all) people with autism and expanded awareness of the potential effects of Scotopic Sensitivity far beyond that of reading disability, also leading to awareness of the effects of fluorescent lighting on those with this perceptual disorder.
The condition was jointly described by two people working individually, unaware of the work of the other person. In the early 1980s New Zealand teacher Olive Meares described the visual distortions some individuals reported when reading from white paper, while American therapist Helen Irlen wrote a paper about the use of coloured overlays aiding the reading abilities of some people. Irlen who was the first to systematically define the condition, named her findings "scotopic sensitivity", though the discussions and debates over the following years, some often referred to it as Meares-Irlen syndrome. Testing for scotopic sensitivity were also taken up by orthoptists in UK hospitals using a technique that used the Intuitive Colorimeter, developed under Medical Research Council license. Other commercial organisations have produced sets of therapeutic tints, although most have not received scientific evaluation.
TheoryScotopic sensitivity syndrome is based on the theory that some individuals have hypersensitive photoreceptors, visual pathways, and/or brain systems that react inappropriately to physical energy (wavelengths). Vision occurs when energy is received by the retina's photoreceptors, initiating a biochemical process affecting the visual pathways and deep structures of the brain. A growing number of researchers are taking an interest in the view that inappropriate biochemical processing has the potential to cause physiological and/or visual perceptual problems. Many of these problems are grouped together under the label "scotopic sensitivity syndrome". This "theory" is little more than a vague re-statement of possible mechanisms that might account for the observed facts. --Rhonda Stone, Author, The Light Barrier, St. Martin's Press, 2002/Griffen, 2003
SymptomsOne or more of these symptoms may be related to the condition:
- Headaches (including migraine)
- Nausea, including visually-related motion sickness
- Problems with depth perception (catching balls, judging distance, etc.)
- Restricted field of view and span of recognition
- Discomfort with busy patterns, particularly stripes ("visual stress" and "pattern glare")
- Discomfort with extreme conditions of bright/dark contrast (i.e. backlighting)
- Discomfort or difficulty reading (reading involves busy patterns, particularly stripes. People with strong symptoms of the syndrome find it very difficult to read black text on white paper, particularly when the paper is slightly shiny.)
- Text that appears to move (rise, fall, swirl, shake, etc.)
- Attention and concentration difficulties
- Seeing the part and losing the whole
- Epileptic seizure related to strobing or pattern glare
TreatmentThe use of tinted lenses in glasses and coloured overlay sheets has been prescribed by many doctors; however, the efficacy of such treatment is questionable. It has been felt to be efficient treatment by some, and inappropriate by others, because more conventional treatments are sometimes more appropriate.
The American Optometric Association acknowledges the benefits of tinted lenses for some individuals and recommends further scientific investigation. The College of Optometry (UK) goes further, specifying guidelines for optometrists who use the colorimeter system. A society for colored lens prescribers (s4clp.org) has been established to provide a list of eye-care practitioners with expertise in the provision of colored lenses for the treatment of visual stress.
Irlen MethodThe Irlen Method is a controversial system that is intended to improve reading difficulties associated with scotopic sensitivity syndrome using tinted lenses and overlays. Irlens Lens Program - University of Newcastle, Australia
Intuitive ColorimeterDeveloped by Arnold Wilkins, Ph.D., University of Essex, England, an alternative system for the identification of tint to reduce symptoms.
Skepticism surrounding scotopic sensitivity syndrome has evolved on several fronts:
- Whether SSS exists as a distinct, predictably identifiable disease with a reasonable pathophysiologic mechanism;
- Whether SSS is causally or incidentally related to dyslexia, autism, or other conditions; and
- Whether existing methods of SSS treatment are appropriate and effective.
The association of scotopic sensitivity syndrome and dyslexia has been challenged by many authors in both the optometric and ophthalmologic communities. but recent scientific evidence suggests a weak association.
Tinted lenses and dyslexics--a controlled study. SPELD (S.A.) Tinted Lenses Study Group.
Gole GA, Dibden SN, Pearson CC, Pidgeon KJ, Mann JW, Rice D, Rooney KF, Hannell G, Fitzgerald BA, Kortman JY, et al.
SPELD Incorporated, Kensington, South Australia.
Critics claim that the symptoms of those with Scotopic Sensitivity Syndrome are related to already known visual disorders. According to a statement released by the American Optometric Association in 2004http://www.aoa.org/x5418.xml: ''"There is evidence that the underlying symptoms associated with the Irlen Syndrome are related to identifiable vision anomalies, e.g., accommodative, binocular, and ocular motor dysfunctions, in many patients seeking help from colored lenses. Furthermore, such conditions return to normal function when appropriately treated with lenses, prisms, or vision therapy. When patients exhibiting the Irlen Syndrome were treated with vision therapy, their symptoms were relieved. These patients were no longer classified as exhibiting this syndrome, and therefore did not demonstrate a need for the colored overlays or tinted lenses."''
A previous controlled study found the lenses not to significantly improve reading but several of its peer reviewed studies did find distinct neurological patterns in those displaying strong symptoms consistent with the syndrome.
Although experts are divided over the pathology of Irlen Syndrome, and whether several distinct syndromes are not being mistakingly placed under this loosely defined one, what is agreed is that for sufferers, the symptoms are very real. In a small minority of extreme cases, they do appear quite pronounced, even acute. This is important to stress, because the impression may have been gathered from the discussion on this subject, that those displaying symptoms are in some sense 'faking it'. In truth, very few researchers, and none of the most widely respected ones, believe this to be the case, nor have they ever suggested this. ability."http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2757828&dopt=Abstract
TerminologyCritics assert that the term "scotopic sensitivity" is a misnomer given that the symptoms of "Scotopic Sensitivity Syndrome" reportedly occur during photopic conditions.
- As described by people with a related problem
- Irlen.com http://www.irlen.com/
- Irlen.org.uk http://www.irlen.org.uk/
- IrlenCentre.ca http://www.irlencentre.ca/general.html
- "Scotopic Sensitivity Syndrome and Appropriate Referral to Irlen Dyslexia Centres" http://services.admin.utas.edu.au/alda/options/app/app7.htm at the University of Tasmania
- "Irlen Filters and Learning Disabilities" http://www.ldrc.ca/contents/view_article/207/ at Learning Disabilities Resource Community (Canada)
- "The role of visual therapies in the management of children with learning difficulties" http://www.eyedr4kids.com/dyslexia%20learning%20difficulties.htm#Summary at Paediatric Ophthalmology and Strabismus
- Going through the looking glass, BBC News, 3 June 2007.
- Research in use of overlays
- Information from the BBC
scotopia in German: Irlen-Syndrom