Scotopic Sensitivity Syndrome

Scotopic sensitivity syndrome or Visual Stress Syndrome, also known as Irlen Syndrome or Meares-Irlen syndrome 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. There is agreement that visual perceptual disorders exist and can be debilitating, but there is little published research in the area and very little which is not associated with commercial therapeutic activities.

Similar symptoms were 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 was also taken up 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 is used by the Orthoscopics franchise in the UK, with wide 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.