MARIETTA, Ga., March 19, 2013 /PRNewswire/ -- Did you know that your students' performance on their school's standardized test might not be an accurate representation of what they know? Why? Because as many as one in five students have undetected eye-muscle coordination problems that make it uncomfortable or painful for them to see clearly up close, even if they have had normal eye exams or have 20/20 eyesight. These vision issues affect performance year-round, but they are especially challenging during the high-pressure atmosphere of timed, standardized tests. "For many students, eye-muscle problems cause them to see double, or to see words blur, come apart, or dance on the page," said Dr. David Cook, founder of Cook Vision Therapy Center in Marietta, Georgia, and author of When Your Child Struggles, The Myth of 20/20 Vision. "These problems also can result in headaches or fatigue after just a few moments of reading. The longer these students try to focus, the worse the symptoms become." Unfortunately, many of these students assume everyone sees the way they see. They simply don't know they have a vision problem. And they certainly don't know effective, life-changing help is available. Many children, and adults, too, can permanently correct their vision issues and eliminate the resulting problems in a matter of months through vision therapy, which is basically physical therapy for the eyes, said Dr. Cook. While these vision problems are relatively easy to correct, they often go undetected. Eye-muscle issues are seldom tested for during vision screenings at school or in a pediatrician's office, or even in standard eye exams with an optometrist. But parents and teachers can watch students for these and other signs: frequent headaches, re-reading material, rubbing of the eyes or tilting of the head, decreased comprehension and performance the longer the student works, and spending hours doing a few minutes' worth of homework.