Scotopic Sensitivity Syndrome

Scotopic sensitivity syndrome, also known as Irlen Syndrome and Visual Stress 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 as a homogenous condition by the American Academy of Pediatrics or the American Optometric Association, although its symptomatic occurrence is accepted by the latter and has never been contested by the former. It is accepted as a homogenous condition however by a respected body of international expert medical opinion, and has been studied in the former Applied Psychology Unit, Cambridge University in the UK, and the Scottish Parliament has also funded a research and treatment centre at the Glasgow Caledonian University, for the associated condition of Meares/Irlen Syndrome.

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 (Irlen filters) 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 separately described by two people working individually, each unaware of the other's work. 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 in 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 optometrists, opticians, and orthoptists in UK hospitals, and by optometrists and opticians in private practice using a technique that used the Intuitive Colorimeter, developed under Medical Research Council license. A major leap forward has been realised by Orthoscopics in the UK, with extend color coverage and tints manufactured by Hoya to match. Other commercial organisations have produced sets of therapeutic tints, although most have not received scientific evaluation.

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