I got some clear understanding here and just yesterday got my son's vision examined by a Developmental Optometrist. After 2 appts. with an opthalmologist that told me everything was perfect, we find out that he is significantly delayed in focusing, tracking and some other stuff. He is in the 5th percentile for an 8 year old in tracking - and, he is in a grade with nine year olds!! It took him a long time to refocus from looking at a distance to close up! He was not able to tell anyone and his teachers/etc did not pick up on this... He also moves his head as he reads.. The website will tell you more - 90% of kids who struggle to read have undiagnosed vision problems.