Dyslexic people may uniquely not have a dominant eye, a trait that may cause the mirror effect that disrupts their ability to read, according to a new study.
Researchers at the University of Rennes in France conducted a study of 60 people, half of whom were dyslexic and half of whom were not.
When they examined their eyes, they found that non-dyslexic people had spots that indicated that one eye was dominant over the other. Dyslexics had the same types of spots in each eye, which the researchers say indicate that neither eye is dominant.
Not having a dominant eye could confuse the brain by creating ‘mirror’ images, but the researchers claim to have found a way to ‘cancel’ the duplicated image.
Dyslexic people often make ‘mirror errors’ that make it difficult to read and spell. A new study suggests that this could be because they do not have a dominant eye
About 700 million people worldwide struggle with dyslexia, which can make learning to read and, subsequently, learning itself very difficult.
Many people with dyslexia often make ‘mirror errors’ when they read, and struggle to distinguish between things like the letters ‘b’ and ‘d.’
Previous research suggests that dyslexia may be genetically inherited, or may develop after birth. Dyslexic people have a difficult time making the correct connections between letters they read, and the sounds and words that should result.
Some research has theorized that dyslexia is a linguistic problem, and related to the use of the right hemisphere of the brain to read and spell, instead of the left, which is better suited for these functions.
Though it’s not the first to suggest that dyslexia is – at least in part – a visual problem, this new study suggests differences in eye anatomy could be the underlying cause for the faulty way that the brains of dyslexic people process information.
Dr Guy Ropars and Dr Albert le Floch found that there were differences in the eye anatomies of those with and without dyslexia.
Our eyes contain two kinds of cells for processing visual information. Rods help us see in low light, while cones process spatial and color information. We have red, green and blue cones.
The study found that the dominant eyes of non-dyslexic people had a round spot in the cornea where there were no blue cones, while the other eye had an irregularly-shaped spot.
The dyslexic participants’ eyes were identical. Both the right and the left eyes had the same round spot, with the same blue-cone hole, meaning neither eye was dominant over the other.
‘The lack of asymmetry might be the biological and anatomical basis of reading and spelling disabilities,’ the study authors said.
They hypothesize that the lack of a dominant eye creates the mirror-image effect experienced by dyslexic people.
So, the researchers experimented with a way to ‘cancel’ the double image. They used imperceptibly high-speed flashes from an LED lamp to block the mirrored images while the dyslexic participants read.
The authors report that their subjects called the light the ‘magic lamp,’ but admit that the experiment was very preliminary.
Linda Siegel, editor-in-chief of the International Dyslexia Association’s journal, Perspectives on Languages and Literacy is dubious, however.
She says that their controls and tests are insufficient, and that ‘the research itself is flawed.’
‘Let’s say there were differences between dyslexics and non-dyslexics,’ she says, ‘that doesn’t mean the difference is what caused the dyslexia.’
She added that other research has found differences in the visual perceptions of dyslexic and non-dyslexic people, ‘but compared to the differences in language and sound awareness skills, the differences are small.’
Most people with normal vision have one dominant eye, which has a greater concentration of neural connections to the brain.