Group offers pointers on how students' vision impacts ability and inability to learn
From the Children’s Vision Information Network
Throughout grade school, the demands placed on children in the classroom are great. However, no task is more challenging in those early years of school than learning to read.
Reading requires children to accurately use all of their language, decoding, phonetic, and visual skills to successfully recognize words and gather meaning from the written text. Unfortunately, about 20 percent of school-aged children struggle to read. Some of these children suffer from learning disabilities or dyslexia, the inability of the brain’s verbal language or auditory processing centers to accurately decode print or phonetically make the connection between the word’s written symbols and their appropriate sounds. However, a large portion of children struggling to read are not dyslexic at all; their phonetic awareness and language-processing skills are fine. It’s their vision that is interfering with their ability to read.
Vision plays a vital role in the reading process. First of all, children must have crisp, sharp eyesight to see the print clearly. School vision screenings routinely check children’s sharpness of vision at distance—measured by the 20/20 line on the eye chart—and refer children for glasses if they have blurry far-away vision and can’t see the board from the back of the room. Unfortunately, this is all school vision screenings are designed to check, and children’s vision involves so much more.
For success in school, children must have other equally important visual skills besides their sharpness of sight, or visual acuity. They must also be able to coordinate their eye movements as a team. They must be able to follow a line of print without losing their place. They must be able to maintain clear focus as they read or make quick focusing changes when looking up to the board and back to their desks. And they must be able to interpret and accurately process what they are seeing. If children have inadequate visual skills in any of these areas, they can experience great difficulty in school, especially in reading.
Children who lack good basic visual skills often struggle in school unnecessarily. Their “hidden” vision problem is keeping them from performing at grade level, yet teachers and parents often fail to make the connection between poor reading and the child’s vision.
Learning-Related Vision Problems
Eye Teaming Problems
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 10 percent of school-aged children have eye-teaming problems— technically, called convergence insufficiency or convergence excess. At the close-up distances required for reading, children with eye-teaming problems are able only to aim their eyes together correctly for short periods of time. As their ability to accurately aim their eyes breaks down, their eyes end up pointing at slightly different places on the page. The result is a great deal of visual strain and eventually blurred, scrambled or double print.
Tracking skills, or the ability to control the fine eye movements required to follow a line of print, are especially important in reading. Children with tracking problems will often lose their place, skip or transpose words, and have difficulty comprehending because of their difficulty moving their eyes accurately. Many are forced to use their fingers to follow the line because their eyes can’t.
When we read, our eyes don’t move smoothly across the line. Instead, our eyes make a series of jumps and pauses as we read. The small jumps between words or groups of words are called saccades. The brief pause we make while looking at the words is called a fixation. After a fixation, we move our eyes to the next word or group of words—another saccade.
This very precise coordination of jumps and pauses is controlled by our central and peripheral visual systems. Our central vision processes what we’re seeing in clear detail and defines what we’re looking at. Our peripheral, or side vision, simultaneously locates surrounding objects and let’s us know where to look. (These two systems are sometimes referred to as the “Where is it?” and “What is it?” systems.) In reading, our central vision processes the word, while our side vision locates the following word and tells us where to aim our eyes next. The integration of these two systems is what allows us to efficiently move our eyes along a line of print without overshooting or undershooting, or mistakenly aiming our eyes at lines above or below. If there is not continuous, fluid, simultaneous integration between these two systems, reading will be jerky, loss of place will be common and comprehension will be poor.
Visual Motor Integration
Twenty percent of the raw visual data coming off the retina does not go back to the visual cortex for imaging but breaks away and travels up to the brain’s motor centers to help with balance, coordination, and movement. Visual motor integration, commonly called eye-body or eye-hand coordination, is a critical component of vision. Think of it as a visual “follow the leader:” The eyes go first and tell the muscles where to follow.
Gross Motor Eye-Body Coordination—the efficient visual input to the body’s relationship with its surrounding space, commonly referred to as eye-body coordination. Good visual motor and bilateral integration skills allow children to use their visual systems to monitor and adjust placement of their body weight against the gravitational forces on both sides of their body’s midline, allowing for good balance and coordination. Children with poor eye-body skills may have difficulty in such areas as sports, learning to ride a bicycle, or general “clumsiness.”
Fine Motor Eye-Hand Coordination—the efficient visual input into the body’s fine motor system. Children with poor eye-hand coordination may have poor handwriting and take longer to complete written assignments. They usually become frustrated over time and lose concentration, resulting in less time on task.
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