MONDAY, May 25, 2015 (HealthDay News) -- Eye training or other vision therapies will not treat dyslexia in children, say researchers who found normal vision among most children with the learning disability.
The findings confirm what eye doctors have known for a long time, said Dr. Mark Fromer, an ophthalmologist at Lenox Hill Hospital in New York City.
"Dyslexia is a brain dysfunction, not an eye disorder," said Fromer, who was not involved in the study. "There are no studies that clearly identify that visual training can be helpful for the dyslexic patient."
Depending on the definition used, as many as one in five school-aged children in the United States may have dyslexia, the researchers said. If severe reading difficulties associated with dyslexia aren't addressed, they can affect adult employment and even health, they added.
The new findings, published online May 25, will appear in the June issue of the journal Pediatrics.
The researchers tested over 5,800 children, aged 7 to 9, for a variety of vision problems, including lazy eye, nearsightedness, farsightedness, seeing double and focusing difficulties.
The 3 percent of children with dyslexia who had severe difficulty reading showed little differences in their vision than children without dyslexia. And 80 percent of children with dyslexia had fully normal vision and eye function in all the tests, the findings showed.
A slightly higher proportion of those with dyslexia had problems with depth perception or seeing double, but there was no evidence that this was related to their reading disability. After making adjustments for other contributing factors, this finding seemed due to chance.
"It does make sense to think something is wrong with your eye if you're not reading well, but there really is no connection between any ophthalmological disorder and dyslexia," said Fromer, who is also director of eye surgery for the New York Rangers hockey team.
Though the study findings aren't new, this review is much larger than previous ones, he added.
"The biggest issue here is that parents of dyslexic children should not waste a lot of money on vision training for their children with dyslexia," Fromer said. "It won't work."
Study co-author Dr. Cathy Williams said the research adds to evidence about dyslexia and how to treat it.
"We hope professional bodies, charities and support groups will share this information with families and teachers, along with the findings of systematic reviews of treatments, so that families and teachers are aware of the best options to help affected children," said Williams. She is a senior lecturer in child visual development at the University of Bristol in England.
Other researchers have previously found differences in the brain among those with dyslexia compared to children without the disorder, said Dr. Walter Fierson, a pediatric ophthalmologist from Arcadia, Calif.
That research showed that the cause of the disability has to do with how someone processes letters and sounds, not with how they perceive letters and words in the first place, said Fierson. He is co-author of the American Academy of Pediatrics' policy statement on learning disabilities, including dyslexia.
An initial eye evaluation to find out if eye problems are present is important, he said. But this is only to rule out problems or treat specific conditions -- prescribing glasses or contacts for nearsightedness or farsightedness, for instance.
"To date, the best techniques for the remediation of dyslexia involve intensive one-on-one -- or at least small group -- teaching by phonetic methods by experienced teachers," Fierson said.
"At least as important, however, is an initial evaluation by a neuropsychologist or educational psychologist to determine the specific problem areas present in the poor reader," Fierson added.
"Parents should avoid unproven quick fixes and go for intensive phonics," Fierson said. "As is usually the case, things that seem too good to be true usually are. This includes vision treatments for dyslexia."
The U.S. National Institutes of Health has more about dyslexia.