In some cases, a child labeled as a slow learner in school or as having ADHD may have a problem that stems more from poor vision than any learning disability or behavioral problem. Children who have seen nothing but blurred words on the blackboard or on printed pages may think that they are seeing what other children are seeing, so they will not know enough to point out the problem to parents and teachers as their grades decline. Although many schools test children with the Snellen eye chart, this test leaves 70% to 80% of eye problems undetected. For a more comprehensive examination, children should be brought to an eye professional for a complete eye exam each year. If left untreated, some childhood vision problems can cause permanent vision loss. That’s why early identification of vision problems is crucial. Children with diagnosed vision problems should be examined annually by their optometrist. Those without problems should have an exam every two years, and those who develop headaches or have trouble reading or learning should be examined immediately. Signs for parents to watch for that may indicate something is wrong with their children’s vision include squinting, avoidance of close work, short attention spans, complaints of headaches, and an inclination to turn their head to one side.