Study shows green lenses help dyslexic kids (photo: Milena Razuk)

A joint research team from Brazil and France have shown green filters increased reading speed for nine- and 10-year-olds with dyslexia.

Coloured filters for the treatment of learning disabilities were first patented in 1983 and have since been extended for use by children with autism and attention deficit hyperactivity disorder (ADHD), said researcher Milena Razuk. “However, studies of their efficacy were methodologically flawed. We used a highly rigorous methodology for the first time.”

Razuk, who completed her PhD in April at Cruzeiro do Sul University in São Paulo, Brazil, studied the effect of yellow and green lenses on dyslexic children while in France on a research internship at Paris Diderot University. Eighteen children with and another 18 without dyslexia were asked to read passages from children’s books, suited to their reading age, displayed on a computer screen with a yellow filter, a green filter and no filter while their eye movements were recorded. “A child with dyslexia has to fix his or her gaze on the words for a longer time to understand a text. Reading speed is slower as a result,” said principal investigator Professor José Angelo Barela, from São Paulo State University’s Rio Claro Bioscience Institute.

While the filters did not affect the reading speed of children without dyslexia, children with dyslexia read significantly faster with the green filter, compared with the yellow filter or no filter. The authors said the green filter improved reading performance in dyslexic children because the filter most likely facilitated cortical activity and decreased visual distortions.

Although its exisitence is disputed by some professional bodies, including The Royal Australian and New Zealand College of Ophthalmologists (RANZCO), Irlen syndrome (also referred to as Meares-Irlen Syndrome, Scotopic Sensitivity syndrome, and visual stress) is a perceptual processing disorder which the Irlen Institute claims can be eased with coloured lenses.