Coloured filters are designed to help individuals with visual processing difficulties, visual stress and related problems.
People with visual processing difficulties are especially sensitive to lights, glare, patterns, colours, and contrast. People with visual stress may experience perceptual distortions and discomfort, especially when reading printed text.
Some people have suggested that visual processing difficulties and/or visual stress are common in people with conditions such as reading and learning difficulties, ADHD or autism. For example, the Irlen website, accessed on 2 March 2016, claims that Irlen syndrome [visual stress] affects 33% of people on the autism spectrum, although we have found no evidence to support this claim.
According to Ludlow et al (2007),
“The visual processing abnormalities commonly reported in ASD include hyper sensitivity to lights and colors and experiences of visual distortion, which may, for example, alter the perceived dimensions of rooms. Visual distortions can also result in difficulties writing on printed lines and maintaining appropriate spacing between letters and words. Whilst there is no clear consensus about the root cause of these difficulties it has been suggested that some individuals with autism suffer from a co-occurring disorder called visual stress. Visual stress refers to perceptual distortions and discomfort, most notably when reading printed text. Williams has suggested that the co-occurrence of autism and visual stress results in particularly dramatic symptoms characterised by fragmentary perception. “