Grapheme-colour synaesthesia and the orthoptist

Abstract

Aim: To give an overview of the condition known as grapheme-colour synaesthesia, and examine whether there is a need for orthoptists to be aware of its existence and potential impact when it coexists with other conditions, such as specific learning difficulty and Meares-Irlen syndrome. Methods: A literature-based review was performed. Relevant material was identified using the University of Liverpool library catalogue, Google, PubMed and Web of Knowledge. The focus was on relevant research published within the last 15 years. Results: Evaluation of the literature shows that grapheme-colour synaesthesia is thought to arise from increased structural connectivity between brain areas involved in the processing of colour and visual word forms. The grapheme-colour linkages are very specific and long-standing, possibly congenital, and the condition is probably genetic. It is more common than previously thought, and could potentially coexist with visual perceptual difficulties such as dyslexia and Meares-Irlen syndrome. However, due to a lack of awareness of the condition it is rarely diagnosed. As grapheme-colour synaesthesia appears to have an impact on reading and mathematical ability, it is relevant to the orthoptist’s extended role in assessing children with these conditions. Conclusion: Grapheme-colour synaesthesia is more common than previously thought, and although more research is needed to establish the true impact of grapheme-colour synaesthesia on other visual conditions, the orthoptist may wish to consider including the condition in the list of differential diagnoses in cases of specific learning difficulty and Meares-Irlen syndrome.

Keywords

• Grapheme-colour synaesthesia
• Functional brain imaging
• Meares-Irlen syndrome
• Specific learning difficulty