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.
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.
The Promethean Trust, a Norwich-based charity for dyslexic children, has found that the use of a cursor has eliminated the need for colored overlays or lenses. The cursor is simply a piece of card or plastic, approximately the size of a business card, with a notch cut out of one corner. The reader (or the remedial teacher) uses this to track print from left to right, and at the same time the card prevents the eyes from wandering ahead. Although no formal research has been conducted, it is likely that most cases of visual confusion result from the eyes moving in mini-saccades when the reader encounters an unfamiliar word. This occurs as the reader unconsciously tries to scramble letters to achieve a 'fit' with a familiar word. This creates the subjective impression that the letters 'won't stay still'.
Skepticism surrounding scotopic sensitivity syndrome has evolved on several fronts:
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.
We have carried out a randomised prospective controlled trial of the effect of tinted lenses on the reading ability of 24 non-asthmatic dyslexic children aged between nine and twelve years. Reading ability was assessed using the Neale Analysis of Reading. After one school term, there was no significant difference in the change in reading age between treatment and control groups. After two school terms (approximately six months), only 11 children (44%) were still wearing the glasses. Of 381 suitable subjects for entry into the study, 208 were excluded because of a diagnosis of asthma (to avoid effects of medication on cerebral function). As a result, we may have excluded subjects who would have responded favourably to tinted lenses.
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 2004 : "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."