Helen Irlen, a psychologist, discovered that colour can affect the way the brain processes visual information. She believed that, in some individuals, the nervous system is wired differently and reacts badly to some colours. This causes problems processing, interpreting, and interacting with the environment.
In 1983 she invented Irlen lenses and overlays, which are designed to filter out the colours which cause the problems. Sometime later Professor Arnold Wilkins at the University of Essex developed a set of coloured filters which he called ‘Intuitive Overlays.’ These are designed to do the same thing.