Borrowed from www.childrensvision.com
I feel this does a great job explaining how these vision issues can effect a child and his or her learning.
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% 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 in order 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.
The following information summarizes each of the major areas which can interfere with a child's school performance.
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 ten 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 only able 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.
Example:
Example:
Of course, reading and comprehension become increasingly difficult as the child strains to aim both eyes at the same place to keep the print from blurring, jumping, or splitting apart like this:
In addition, children with eye teaming problems can be highly distractible, finding it difficult to concentrate and remain on task when the strain on their eyes is so great. (In fact, many of these children are often misdiagnosed with attention deficit disorder.) Other symptoms of eye teaming problems include loss of place as the print "swims" and moves, eyestrain, fatigue, headaches, and frustration.
To keep from seeing double, many children with eye teaming problems end up suppressing an eye. In other words, their brain "turns off" one eye by neurologically blocking its visual input. This allows allows them to maintain single vision because they're just using one eye. While suppression helps the child cope, but it's extremely tiring and robs the child of concentration.
Because these children have always seen this way, their vision seems normal to them. They don't recognize that they're fighting their eyes harder than anyone else just to maintain a clear, single picture. Very rarely do children realize something is wrong and report transient double vision or the eye strain and fatigue which usually accompanies suppression. Left undiagnosed and untreated, eye teaming problems can appear to be a learning disability or dyslexia. They are not. Eye teaming disorders are visual problems, not language-based reading dysfunctions. The symptoms, however, are similar and only a complete eye exam by an developmental optometrist trained to diagnose and treat eye teaming problems can determine for certain if vision is the basis of the child's struggle to read.
The good news, however, is that eye teaming problems can be treated very successfully. One type of teaming problem called convergence excess is often corrected with reading glasses. Another teaming problem called convergence insufficiency is usually corrected through vision therapy. Vision therapy is a series of special eye exercises and treatment procedures prescribed by doctors of optometry that correct problems that glasses alone can't help. During therapy, the child learns to gain control of his or her eye muscle coordination and builds the eye teaming skills necessary for success in school.
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.
Children with tracking problems can't control their eye movements at close ranges. The following is an example of how their eyes move during reading, especially as they fatigue:
Our focusing system, technically called accommodation, allows us to see clearly, especially up close. Our eyes are designed for distance vision, so when we look at something up close, the natural lens in our eye has to change shape to redirect light rays on the retina for near objects. At the close ranges required for reading, this is the visual skill needed to maintain clear sharp images for extended periods of time. It also includes the ability to quickly shift focus when looking from near to far, such as when looking from our desk to the board. For children with accommodation problems, print will become progressively blurry as they read for longer periods of time, and their eyes will fatigue from the strain of trying to keep the print clear. Sometimes children with focusing problems will hold their books very closely or lay their heads down. Headaches are very common. Reading glasses are often prescribed to help shore up inadequate focusing systems, but sometimes therapy is need to improve a child's focusing stamina. If a child is struggling with his focusing system, print on the page will often look like this:
.
Vision Perception--the ability to interpret, analyze, and give meaning to what is seen. Visual perception skills can be broken down into the following areas:
Visual Discrimination--the ability to determine exact characteristics and distinctive features among similar objects or forms. In reading, this skill helps children distinguish between similarly spelled words, such as was/saw, then/when, on/one, or run/ran.
Visual Memory--the ability to remember for immediate recall the characteristics of a given object or form. This skill helps children remember what they read and see by adequately processing information through their short-term memory, from where it is filtered out into the long-term memory. Children with poor visual memory may struggle with comprehension. They often subvocalize, or softly whisper to themselves, as they read in order to help compensate auditorily. They may have difficulty remembering what a word looks like or fail to recognize the same word on another page. They may also take longer copying assignments because they must frequently review the text.
Visual Sequential Memory--the ability to remember forms or characters in correct order. This skill is particularly important in spelling. Letter omissions, additions, or transpositions within words are common for children who struggle with this skill. They often subvocalize (whisper or talk aloud) as they write. Recognizing and remembering patterns may also be a problem.
Visual Spatial Relations--the ability to distinguish differences among similar objects or forms. This skill helps children in understanding relationships and recognizing underlying concepts. This area is closely related to the problem solving and conceptual skills required for higher level science and math.
Visual Spatial Orientation helps us with letter reversals. Many parents and educators considered letter reversals after age seven to be a symptom of dyslexia. While this can be true, the most common cause of reversals in older children is a lack of visual spatial development--consistently knowing left from right, either in relationship to their own bodies or in the world around them. Children with poor visual processing have not developed adequate skills in visual perception and spatial orientation, such as laterality and directionality. Also, children who experience frequent double vision deal with such visual confusion that their brains often misinterpret their visual input.
Visual Form Constancy--the ability to mentally manipulate forms and visualize the resulting outcomes. This skill helps children distinguish differences in size, shape, and orientation. Children with poor form-constancy may frequently reverse letters and numbers.
Visual Closure--the ability to visualize a complete whole when given incomplete information or a partial picture. This skill helps children read and comprehend quickly; their eyes don't have to individually process every letter in every word for them to quickly recognize the word by sight. This skill can also help children recognize inferences and predict outcomes. Children with poor visual closure may have difficulty completing a thought. They may also confuse similar objects or words, especially words with close beginning or endings.
Visual Figure Ground--the ability to perceive and locate a form or object within a busy field without getting confused by the background or surrounding images. This skill keeps children from getting lost in details. Children with poor figure-ground become easily confused with too much print on the page, affecting their concentration and attention. They may also have difficulty scanning text to locate specific information.
.
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.
.
Help for Children who Struggle
There is help for children who struggle to read and learn because of poor vision skills. A developmental optometrist who specializes in children's vision can run a complete diagnostic workup to determine to what extent a child's visual skills are hindering school performance and prescribe vision therapy to correct the problems. Vision therapy is the science of remediating inadequate visual systems by improving function and performance. Vision therapy is highly successful, supported by decades of research and the testimony of countless parents and children whose lives have been changed when dysfunctional vision systems are restored to normal. Remove a child's stumbling block to learning, and you allow him the opportunity to succeed. If you suspect your child may be struggling because of an undiagnosed vision problem, you may want to review the checklist of common symptoms. The first step in helping your child is getting good information. To locate a qualified behavioral optometrist who provides vision therapy contact the national certifying board of the College of Optometrists in Vision Development at 1-888-268-3770 or visit their web site at http://www.covd.org. Also, your family optometrist can be a good resource. Ask if he or she provides vision therapy or if they can make a referral to a colleague who does.
You may be interested in reading the resolution passed by the national PTA. Because so many school-aged children are struggling with vision-based learning problems, the Parents and Teachers Association is calling for better school screening methods to identify at-risk students.
|
No comments:
Post a Comment