If a child is having trouble reading, it’s only logical for parents to bring them in for a vision check. And if the child shows 20/20 vision, it’s logical to conclude the problem might originate somewhere besides the eyes. But that may not be the case, according to a recent study of Canadian children published in the Journal of Optometry.

Dr. Lisa Christian from the University of Waterloo in Ontario, Canada, and colleagues performed a retrospective review of these children who had all had complete eye exams. These children also had Individual Education Plans (IEP) specifically directed at improving their reading abilities.

The authors found that while most of the children had good eyesight, a substantial proportion had binocular vision that was below the normal limits on testing, so the children may have experienced blurred images, poor depth perception, or double vision among other problems when they read.

Such problems can result from a variety of conditions, such as misaligned eyes, or poor functioning of the oculomotor muscles. A person with such problems will typically have difficulty reading — they may lose their place easily and develop eyestrain.

So when there is an issue with a child’s learning to read, it could be important to determine whether eye problems other than myopia are the cause.