Spotting the link between vision problems and ADHD

A few years ago Dawn DeCarlo, O.D., started to notice a trend—and it surprised her.

First, as part of her work on a National Eye Institute grant, she conducted focus groups with parents of children who had serious eye conditions. She asked parents if their kids took any medications, and the comments that followed included attention deficit hyperactivity disorder (ADHD) drugs.

"Wow," Dr. DeCarlo, who is on the faculty of the School of Medicine in the Department of Ophthalmology at the University of Alabama at Birmingham (UAB), remembers thinking. "Why do so many kids in these focus groups have problems with ADHD?"

To find out, she turned to her clinic, the UAB Center for Low Vision Rehabilitation, where she is the director. She already had a question on intake forms, asking if young patients had ADHD. Sure enough, when she conducted a review of her cases, nearly one in four—22.9%—of her patients had ADHD.

More than 1 in 10 U.S. school-age children has diagnosed ADHD, according to the Centers for Disease Control and Prevention (CDC). So what was happening in her clinic? And was this an isolated phenomenon, or had she stumbled on a nationwide trend?

Dr. DeCarlo turned to the National Survey of Children's Health (NSCH), a survey of more than 98,000 children conducted by the CDC and, together with her team of Mark Swanson, O.D., Gerald McGwin, Ph.D., Kristina Visscher, Ph.D., and Cynthia Owsley, Ph.D., parsed the data. The results will be published in the journal Optometry and Vision Science in May, and are available online ahead of print now. They describe a clear correlation between serious vision problems and ADHD diagnosis.

Vision and ADHD

The NSCH is a phone survey of nationally representative households that assess the health of children from infants to age 17 through parent report. Dr. DeCarlo and her team took the NSCH's survey results from 2011 and 2012 and deconstructed the data for children ages 4 to 17. She focused on two main questions: Was there a diagnosis of ADHD, and had a doctor told the parent that his or her child had a vision problem that couldn't be corrected by glasses or contacts?

Once her team parsed the data and applied an analysis to come up with associations, Dr. DeCarlo discovered that her clinic wasn't unique after all. Children with vision problems were nearly twice as likely to have been diagnosed with ADHD, compared to those who hadn't. And the odds were even higher for children with mild to moderate vision problems—perhaps, Dr. DeCarlo says, because there weren't enough children with severe vision problems to provide the statistical power to draw conclusions. And this correlation remained true, even after controlling for other potentially confounding attributes.

Next up on Dr. DeCarlo's research agenda is a study that will look at vision impairment and reading development and their associations with executive function—that is, higher-level thinking and decision making—and attention. Her team's hypothesis, she says, is that having low vision may require executive functioning to manage, thus leaving less attention available for everything else.

"There could be some sort of causation between vision problems and attention, but it needs a whole lot more study before we can say that," she says. "It does give us enough evidence, though, to pursue the question."