Vision problems are rare in dyslexic children, and most have perfect eyesight, a large UK population based study has found.
The study’s findings, published in Pediatrics on 25 May,1 reinforced the argument that coloured overlays and lenses are unlikely to help with reading difficulties in children with dyslexia. Around 375 000 UK children have dyslexia, and the use of coloured overlays and lenses by such children is common in educational establishments. Parents can spend hundreds of pounds on them, but their effectiveness remains uncertain.
Studies examining the effectiveness of these reading aids have tended to be poorly designed or inconclusive.2 Professional bodies, including the Royal College of Ophthalmologists, have concluded that “manipulation of the visual system using colour to facilitate reading lacks scientific support”3; however, an editorial in The BMJ last year showed that six of the eight UK charities supporting parents of children with dyslexia included information on their websites endorsing the use of overlays and tinted lenses.2
To assess whether children with dyslexia experienced problems with visual function, researchers at the universities of Bristol and Newcastle looked at the results of comprehensive eye tests conducted on 5822 children participating in the Children of the 90s survey, a large population based study in the south west of England, when they were aged 7 to 9. The children’s reading was also assessed at age 9. The researchers looked at the results of visual function tests in the 172 children (3%) with severe dyslexia and the 479 (8%) with moderate dyslexia and compared them with the children in the group who did not have dyslexia.
The results showed that most of the dyslexic children had perfect vision. No association was found between dyslexia and strabismus, motor fusion, sensory fusion at a distance, refractive error, amblyopia, convergence, accommodation, or contrast sensitivity.
Abnormalities in near sensory fusion were slightly higher in dyslexic children (odds ratio 1.63 (95% confidence interval 1.02 to 2.60)). Similarly, the prevalence of stereoacuity worse than 60 seconds was slightly higher in children with dyslexia (1.58 (1.01 to 2.47)). But, overall, 84% of dyslexic children had no near sensory fusion abnormalities, and 83% had excellent stereoacuity.
Cathy Williams, paediatric ophthalmologist and study author, said, “Vision problems are rare in dyslexic children. The few vision impairments we did see in the dyslexic children also occurred in their non-dyslexic classmates.”
Before purchasing expensive treatments for visual impairments that they believe are associated with their child’s dyslexia, she added, parents should ask “what visual impairment is actually being treated, how it is measured, and what is the evidence that treating it will help a child with dyslexia?”
Alexandra Creavin, of the University of Bristol’s School of Social and Community Medicine, said, “There are treatments and training programmes to help children with dyslexia that do have a good evidence base, including training in phonics (speech sounds).
“We hope national bodies like NICE [the National Institute for Health and Care Excellence] in the UK will produce evidence based guidelines for the management of children with dyslexia and that charities and support groups will signpost families to the best sources of support for their children and present a balanced view of all the evidence.”
Notes
Cite this as: BMJ 2015;350:h2830