In 1983, perceptual problems caused by light sensitivity were identified by Helen Irlen, an educational psychologist, who worked with adults with dyslexia. She discovered that a visual perceptual dysfunction, unrelated to visual skills normally assessed by ophthalmic examination, may cause distortions with print and environment. Helen Irlen suggests that there are people whose problem is not in the processing of information but in the inability to get it through one of the channels, viz. vision. She states that these individuals are highly sensitive to particular wavelengths and frequencies of the white light spectrum leading to rapid fatigue after only short periods of reading, thus giving rise to a reading disability, headaches and stress. Irlen called the cluster of symptoms of this dysfunction Scotopic Sensitivity Syndrome (now known as Scotopic Sensitivity/Irlen Syndrome - SS/IS). SS/IS is a visual-perceptual problem that occurs in some people with learning/reading disorders, autism and other developmental disorders. The symptoms include:
- Light sensitivity: Difficulty concentrating or discomfort in fluorescent lighting, bright sunlight, glare or lights at night.
- Contrast and color sensitivity: Problems with high contrast such as black on white, bright colors, and busy patterns such as stripes and polka dots.
- Poor print resolution: Difficulty reading print, numbers, or musical notes. Problems may include print that shifts, shakes, blurs, moves, doubles, swirls, sparkles, shimmers, or disappears.
- Restricted span of recognition: Inability to read letters, numbers, musical notes or words in groups, or see objects in the environment together. This results in problems tracking, correctly identifying words, or the ability to skim or speed read.
- Attention deficit: Problems concentrating while doing tasks such as reading, writing, computer use, looking, and even listening.
- Poor depth perception: Inability to judge distances or spatial relationships affecting small and gross motor coordination. May be unsure or have difficulty with such things as escalators, stairs, ball sports, or driving.
- Strain and fatigue: Physical symptoms are varied and include, but are not limited to, fatigue, tiredness, headaches, fidgetiness, distractibility and hyperactivity.
Originally, SS/IS was considered a visual-spatial subtype of reading disability. Recent research, however, has shown that SS/IS (in a milder degree) affects about 20% of the general population as well. They experience difficulties with normal working environment, particularly fluorescent lighting and computer screens, resulting in fatigue, eyestrain, headaches, poor concentration, inefficiency and stress.
SS/IS can be associated with other disorders. Most research has been devoted to SS/IS in people with dyslexia. However, in the 1990s there arose an interest in SS/IS and autism.
The copyright of the article Scotopic Sensitivity/Irlen Syndrome and Autism in Autistic Behaviour is owned by . Permission to republish Scotopic Sensitivity/Irlen Syndrome and Autism in print or online must be granted by the author in writing.
