The aim of coloured filters is to block out the frequencies of light to which the individual is sensitive, allowing the brain to process visual information normally. For example, according to the Irlen website, accessed on 2 March 2016,
“Seventy percent of the information an individual receives enters through the eyes and must be correctly interpreted by the brain. Any problem in the way the brain processes visual information can cause difficulties in the general ability to function. Sensory overload causes problems processing, interpreting, and interacting with the environment. The Irlen Method helps individuals with Autism and Asperger Syndrome who have perceptual problems, light sensitivity, and sensory overload by filtering the frequencies of light to which the individual is sensitive. This allows the brain to process visual information normally.”
It is important to note that visual processing difficulties and visual stress are different to other problems with vision, such as long-sight or short sight. Of course, the same person may suffer from more than one type of vision problem at the same time.
There have been a number of studies which claim that coloured overlays can help some individuals on the autism spectrum. For example,
Ludlow et al (2006) reported “Findings showed that 15 out of 19 (79%) children with autism showed an improvement of at least 5% in reading speed when using a coloured overlay. In contrast only 3 of 19 (16%) control group children showed such an improvement. The findings suggest that coloured overlays may provide a useful support for reading for children with autism.
Ludlow et al (2012) reported “The current findings are important in showing that perceptual abnormalities in a large proportion of children with autism benefit from the use of an overlay, not just in respect of reading ability, but also as regards improvements in perception of facial expression. This then provides further evidence that lowlevel perceptual abnormalities may be responsible for their difficulties attending and processing facial expressions.”
Whitaker et al (epub) reported “Judgments of emotional intensity improved significantly with the addition of the preferred colored tint in the ASD group but not in controls, a result consistent with a link between visual stress and impairments in processing facial expressions in individuals with ASD.”
We have been unable to identify any studies which make claims for the use of coloured lenses. However, the Irlen Institute website, accessed on 3 March 2016, makes the following claims.
“The Irlen Method is not a cure for Autism or Asperger Syndrome. Not every individual with Autism and Asperger Syndrome suffers with perceptual problems, light sensitivity, and sensory overload. The Irlen Method is a piece of the puzzle for some individuals. Typical problems that can be helped by the Irlen Method are ..." sensory overload, environmental distortions and print distortions.