Scotopic sensitivity

Irlen syndrome, occasionally referred to as scotopic sensitivity syndrome (SSS) or Meares-Irlen syndrome, very rarely as asfedia, and recently also as visual stress, is a proposed disorder of vision. In 1980 New Zealand teacher Olive Meares described the visual distortions some individuals reported when reading from white paper. In 1983, American psychologist Helen Irlen wrote a paper about the use of coloured overlays aiding the reading abilities of some people. Similar symptoms were separately described by Meares and Irlen—each unaware of the other's work. 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 referred to it as Meares-Irlen syndrome. It remains controversial whether non-Irlen-certified Meares-Irlen syndrome and the original Irlen syndrome are the same condition. Irlen syndrome, for example, seems to include a broader array of symptoms, including severe variants of the core condition. Basic testing for scotopic sensitivity was tried by optometrists, opticians, and orthoptists in UK hospitals, and by optometrists and opticians in private practice employing a technique that used the Intuitive Colorimeter, developed under Medical Research Council license. An alternative approach to correct Irlen syndrome was tried by Orthoscopics franchise in the UK, with wide colour coverage and tints manufactured by Hoyato match. Other commercial organisations have produced sets of therapeutic tints, although most have not received scientific evaluation. The disorders have been studied in several institutions, including the Psychology Department at Essex University, the former Applied Psychology Unit, Cambridge University in England, and in the case of Meares-Irlen syndrome, Visual Unit at Glasgow Caledonian University in Scotland. As of 2012 the Visual Stress Unit offered non-commercial diagnostic and therapeutic services to individuals, and provided advice to the Scottish National Health Service. In Australia, Irlen syndrome was researched by Paul Whiting at the University of Sydney. Whiting set up the first Irlen Dyslexia Centre in Australia, which operated in the Children's Centre at Sydney University for more than 15 years. Irlen syndrome was also studied in Australia by Greg Robinson (1944–2008) at the University of Newcastle. He was director of the Special Education Centre at the School of Education. In the US, peer-reviewed literature on the topic suggests that much is unknown about the cause of these disorders, ranging from the 2011 study in a journal of the American Academy of Pediatrics, 'Irlen Colored Overlays Do not Alleviate Reading Difficulties' and the 2012 study in the journal Brain Topography, 'A Functional Neuroimaging Case Study of Meares–Irlen Syndrome'. The first, purely in relation to Meares-Irlen syndrome, finds that there is no evidence for one of the fundamental claims of therapeutic benefit. The second, which focused primarily on Irlen syndrome, found compelling evidence of unique brain function linked to the syndrome. The College of Optometrists (UK) has specified guidelines for optometrists who use the colorimeter system. A society for coloured lens prescribers has been established to provide a list of eye-care practitioners with expertise in the provision of coloured lenses for the treatment of visual stress. The Irlen Method uses coloured overlays and tinted lenses in the form of glass or contact lenses. The method is intended to reduce or eliminate perceptual processing errors; it is claimed the resultant retiming of visual signals in the brain improves the reading difficulties associated with scotopic sensitivity syndrome.