Many children experience symptoms of ‘visual stress’ when reading. This includes distortions in text and eye strain. Using a coloured overlay on the reading material has been proven to reduce these symptoms and increase reading speed in individuals with photosensitive epilepsy and autism. Tourette’s syndrome and autism often overlap clinically, and individuals with autism have shown symptoms similar to that observed in those suffering from visual stress.
In 2013 a researcher in Anglia Ruskin University’s Psychology department conducted a Pilot study  to investigate the effects of coloured overlays in children with Tourette’s syndrome. The pilot study indicated that a substantially large proportion of children with Tourette’s syndrome may suffer from visual stress when reading. Colour overlays appear to help remediate these symptoms and improve reading rate.
Based on these findings, a larger scale, controlled study was completed, and the results were published in 2016.  The report notes that if visual stress and sensory difficulties are related problems, then the prevalence of visual stress is likely to be higher in children with sensory disorders such as Tourette’s syndrome. Eighty percent of individuals with Tourette’s syndrome reported that tics were produced as intentional responses to aversive sensory phenomena and some researchers have even speculated that Tourette’s syndrome is characterized by a hypersensitivity to sensory stimulation. Given the overlap between sensory behaviours, hypersensitivity and visual stress, it seems likely that visual stress may be contributing to symptoms in Tourette’s.
The study found that a higher than normal proportion of the children with Tourette’s syndrome read more quickly with the use of a coloured overlay, with levels of improvement reaching 54%.
The results of this study provide further evidence consistent with an association between sensory difficulties and cortical hyperexcitability and suggests that children who are hypersensitive to sensory stimuli may experience the greatest benefits from the use of a colour filter.
Given that coloured filters have been found to benefit performance on tasks other than reading; including matching to sample, visual search and recognition of emotion in faces (Ludlow et al, 2008; 2012), the overlays might offer an important tool to children with sensory disorders in educational settings.