A new Canadian study finds that many elementary school children who read below grade level have challenges with their eyesight — even if standard tests say their vision is 20/20.
Researchers from the University of Waterloo found that one-third of a group of children with reading difficulties tested below-normal in binocular vision. Healthy binocular vision is defined as both eyes being able to aim simultaneously at the same visual target. Problems with binocular vision may lead to eye strain, fatigue or double vision.
“A complete binocular vision assessment is not always part of the standard vision test,” said Dr. Lisa Christian, lead researcher on the project and an associate clinical professor at the School of Optometry and Vision Science, University of Waterloo. “However, binocular vision problems could be compounding a child’s academic difficulties, and should be investigated.”
The research involved a retrospective review of 121 children between the ages of six and 14 who had all been assigned an Individual Education Plan (IEP) specifically for reading. The findings show that more than three-quarters of these children had good eyesight, but when they were tested for binocular vision, more than a third of them scored below what was considered normal.
Optometrists classify binocular vision anomalies under three main categories: accommodation, vergence and oculomotor. The symptoms may sometimes appear benign or may be masked as other problems.
Children with accommodative issues have trouble focusing or have difficulty changing their focus from one distance to another. For example, our eyes have a natural focusing system, similar to a camera. When the eyes cannot switch focus correctly, the images appear blurry.
Children with vergence problems have trouble turning their eye in or out — eye movements required for reading. When reading a book up close, for example, our eyes need to be able to move inward to see the words. Children with oculomotor issues have trouble with eye tracking and may lose their place while reading.
“Kids can see words on the page, but if (for example) they have difficulty turning their eyes in to read or focusing words on a page, they may experience symptoms of eye strain, double vision or fatigue after five or 10 minutes,” Christian said. “It’s not just about visual acuity, but about how well the eyes work together when performing an activity such as reading.”
“Full eye examinations, particularly in children with vision issues, may be a tool for parents and educators to assist children who are found to have difficulty reading.”
Source: University of Waterloo