"But it's not my eyes"
We often see children (and adults) who state that in reading or computer use they sometimes skip words or lines or that print sometimes doubles or that they lose comprehension or develop headaches later in the day. These statements are frequently accompanied by the disclaimer "but it's not my eyes."
The statement is partially true: it's not the eyes. It's the visual system which consists of two eyes, a brain and a physical body.
The reason we have a visual system in the first place is to guide movement and protect from predators. Vision is an important part of the body's information processing system. Eyes produce information that is sent to the brain where vision takes place and to the muscles where action takes place. Good sports performance depends upon the same visual abilities that make for good reading vision.
The vision screening that children receive in school and at the pediatrician's office, as well as most eye examinations in doctors' offices, look only at one factor: the ability to see small letters far away. The meaning of 20/20 vision is that the individual can see five letters that are 3/8 of an inch in height at a distance of twenty feet and maintain that ability for as long as it takes to read the letters, about three to five seconds.
Question: What has this to do with reading?
Answer: 20/20 vision has almost nothing to do with reading.
We read at twelve to fourteen inches. The two eyes have to focus at that distance and they have to coordinate so they point at the same place. They must scan stepwise across the page and then return to the next line. They have to perform these functions for an extended time. All these eye movements are controlled by the brain which at the same time is processing information. If an individual has to expend a significant effort in making the eyes perform their tasks there is less energy available for learning and comprehension.
Children rarely complain about vision because they don't know that there is a problem. They assume everyone sees the same way as they do. When a child is asked a question such as "do you ever skip words or lines?" or "do you ever see double?" the parent is often surprised at an affirmative answer. Not until the question is asked does the parent or the child become aware that the vision is not all it should be.
Behavioral Optometric Vision Examination
In a behavioral vision examination these and other important functional vision questions are routinely asked. Only in a behavioral optometric examination are the visual skills required for good reading performance routinely evaluated.