Vision is more than clarity. It is the ability to visualize, understand and apply the information that comes through the eyes. Children with 20/20 sight may not have these abilities.
Therefore, learning problems are often related to vision problems, but often remain undiagnosed or misdiagnosed.
Nearly all the visual problems that deter children from doing well in the classroom will NOT be uncovered by the Snellen eye chart, nor by most stereoscopic devices. The value of these school screening devices is to identify those children who cannot see clearly.
The appearance of irritated eyes, squinting and frequent blinking are PHYSICAL signs of visual problems. A child's PERFORMANCE is affected by problems with eye movement, eye teaming, eye-hand coordination, and visual perception.
Our eyes are designed to work as a team, but each eye functions independently. When we look at something, the right eye records the image and the left eye records the image. Then the two separate images are transmitted up the optic nerves to the brain, which combines them into a single picture. For the visual system to work correctly, each eye must aim at the exact same point in space so that the images being recorded are identical. This allows the brain to combine, or "fuse", the two incoming images for clear, comfortable single vision. However, if the eyes aren't aiming together, then the images being recorded are slightly different. If the disparity is great enough, the brain can't combine the two pictures. The result is double vision.
Unfortunately, about ten percent of school-aged children have eye teaming problems — technically, these are vergence disorders such as convergence insufficiency or convergence excess. At the close up distances required for reading, children with eye teaming problems are only able to aim their eyes together correctly for short periods of time.
The result is a great deal of visual strain and eventually blurred, scrambled, or double print. Children with undetected vision problems can exhibit similar symptoms as children labeled ADD or ADHD. Studies show that approximately 20% of school-aged children suffer from eye teaming or focusing deficits which make remaining on task for long periods of time difficult.
The connection between eye teaming problems and attention deficit disorders was recently documented in medical journals. The latest research study found children diagnosed with ADHD were three times as likely to have a convergence insufficiency than children in the rest of the population.
Any child who is suspected of having ADD should have a complete eye exam by a pediatric specialist in children's vision to determine if poor visual processing is a factor in the child's behavior.
Unlike ADD which is diagnosed by a subjective checklist, objective clinical measures and tests can be run to determine for certain if the child has a learning-related vision problem which is making it difficult for him to remain on task.