An Adequate Visual System is Critical to Learning!
Since 80% of all a child learns comes to them through their visual pathways, if there is any interference in those pathways a child will not develop to their maximum potential.
All that is meant by the notation 20/20 is that a person is capable of seeing clearly at a distance of twenty feet. However, how well a child sees at twenty feet has very little to do with how their vision functions at the reading and learning distance.
20/20 often gives parents and teachers a false sense of security that vision is normal. There are many other important visual skills that might not be developed even though visual acuity at distance is normal.