The prevalence of dyslexia has been estimated to be 10-20% of children in a regular classroom and greater than 50% in a special education classroom. The prevalence is equal in males and females, but tends to be more severe in males.

Reversals and Dyslexia


When you hear the word dyslexia, many people immediately visualize an image of jumbled words printed in reverse. This word reversal phenomenon is certainly true for some dyslexics, however dyslexia is far more complicated than simple word reversals.

Actually, reversal tendencies are normal for small children. By age eight, however, reversals should not be prevalent in a well developed child. Because of this fact, research shows that reversals are a significant predictor of reading achievement when using standardized testing such as the Gardner Reversals Test. Reversal problems in children older than eight years old are usually caused by problems with vision and can be remediated.

So what is Dyslexia?

Dyslexia is a difficult term to define, especially since it has become the catch all word for many types of reading and processing problems. Even among professionals, agreeing on a common definition of dyslexia is not easy. Consequently, there is much controversy about the way to treat dyslexia, sometimes even in the same field.

Treatment options for those individuals diagnosed dyslexia vary greatly due in part to the lack of agreement about how it creates the dysfunction and what aspects are considered most important. Many professionals disagree on or flat out reject certain types of treatment due to different areas of expertise and the lack of knowledge about other professions. Don't be surprised if you find this in your search for treatment options.

Dyslexia, in general terms, is a learning disability that makes written language more challenging. People with dyslexia have trouble mostly with reading, writing and spelling.

Dyslexia is generally believed to be a problem with interpretation of information by the brain; information taken in is not processed in standard ways. Words may be read but not understood, or letters rather than the entire word are seen or read.

Dyslexia is not related to intelligence, teaching methods or sociocultural opportunity. Those that suffer with dyslexia are a population of children who have difficulty learning to read in spite of good intelligence, educational opportunities, cultural experiences and normal sensory development.

The issue of learning disabilities becomes even more complicated when dyslexia is a factor, especially since many kids are labelled dyslexic unnecessarily. Dyslexia should be diagnosed only after other causes for reading difficulties are ruled out, such as vision, hearing or instruction problems.

Unfortunately, many schools districts around the country, dyslexia is often diagnosed and used to qualify a student for special education if a student is two years behind or more in reading and not working up to their intellectual potential.

Dyslexia and Research

Neuropsychologists most often conclude that dyslexia is a language processing problem. Brain image studies (fMRI, PET scan) show that people with dyslexia seem to process language information in a different area of the brain than people who do not have dyslexia, regardless of intellectual ability.

When comparing good readers with poor readers, other brain image studies have shown that non-efficient readers use predominantly the speech/auditory parts of the brain while efficient readers use the visual parts of the brain.


Though the brain image studies is an exciting way to understand the differences in how the brain fires in different types of learners, it is important to remember what comes first, the chicken or the egg? Does the brain process a certain way during reading because it did not learn and develop the skills needed efficiently or is there something physically wrong with the brain, that caused the person to process differently?

It has been shown with EEG studies that the way a brain processes can be changed with proper feedback to the brain. Occupational therapy, physical therapy, speech/auditory therapy and vision therapy would not be successful if we could not re-pattern the brain.

Vision Therapy and Dyslexia

Learning to read requires both phonetic and eidetic processes, which are cognitive ways to decode and encode words, respectively. Visual skill deficits can interfere with both encoding and decoding words, in a host of different ways. Vision problems can cause problems with sight recognition, reading comprehension, memorization, recall, fluency, speed, rhythm and the length of time spent reading or writing.

In order to explain how a behavioral optometrist can help diagnose and manage vision related learning difficulties in dyslexic individuals, it may be helpful to briefly explain some of the categories of dyslexia.

The following terms are for your information, but the bottom line is the label is not really what matters (though sometimes it is necessary to begin correct treatment and management). What IS important is what can be done about the difficulties the child is experiencing to make it easier for them to learn. Don't let the labels and terms make you forget the child.

The three most common types of dyslexia and how optometrists can help:

  1. Dysphonesia - A dysfunction where the primary problem is letter-sound integration. They are unable to identify words or letters with their accompanying phonetic sounds. They cannot attack unfamiliar words using skills such as phonics, syllabication and/or structural analysis. This is a decoding problem. Dysphonetics rely on eidetic coding (word attack skills). You can think of eidetic coding as memorizing words instead of sounding them out. Words like "pneumonia" and "mnemonics" are eidetically coded. Dysphonetics may recognize familiar words, but are incapable of efficiently decoding unfamiliar and multisyllabic words because they have difficulty sounding out and blending sounds together. For example, if they were taught the word "deal" they may still have difficulties with the word "seal" or not know how to read the word "dealing." These children tend to need more educational help rather than optometric remediation, though remediating any vision problems that could be causing some of the difficulty is always helpful.
  1. Dyseidesia - A dysfunction that involves whole word decoding, a more global process in which words are recognized based upon their shape and configuration. This is the opposite of dysphonesia. People that are considered dyseidetic lack the ability to take whole words or configurations and perceive them as a unit symbol (or gestalt), but can use skills such as phonetics (sounding out words), syllabication and structural analysis. This means they don't have good word attack skills. It is more of an encoding problem. They have problems storing information, which involves sequential memory (knowing the right order of things). Consequently, retrieval of information is difficult. People who experience this dysfunction rely on phonetic coding instead, which can lead to incorrect spelling. Some researchers have found that these individuals have deficient short-term visual memory (the ability to recall previously presented visual experiences), visual discrimination (the differentiation between visual patterns), visual figure ground (differentiating a particular part of a visual field, e.g. Where's Waldo), and visual sequential memory (visualizing in a particular order). These problems are often remediated by visual perception training. Visual perceptual therapy can improve a person's reading skills and comprehension, assuming they are still provided the proper educational instruction.
  1. Dysnemkinesia - A dysfunction that involves memory and motor movement. Individuals with this dysfunction tend to be distinguished by their abnormally high frequency of letter reversals. It is the dysfunction most people think about when they hear the word dyslexia. This is actually a developmental issue. It occurs due to poor development of the visual spatial skills known as laterality and directionality. They have problems with things like symbol orientation. For example, "p" "b" "q" and "d" are all the same symbol oriented in different ways. Dysnemkinesics will not see this symbol as being different letters when oriented differently and will confuse them. Consequently, Dysnemkinesics tend to transpose letters and syllables, exhibit faulty eye movements, demonstrate excessive reversals, and have spatial difficulties. They often have poor sight recognition, and tend to have trouble building up a sight vocabulary. Reading tends to be slow and difficult, since they often read and spell phonetically. Dysnemkinesia is the easiest type of dyslexia to identify and treat by an optometrist skilled in vision training.

NOTE: You can have one or more types of dyslexia at the same time, e.g. dysphoneidetic.

What should you do if you suspect a child of having dyslexia?

Since vision is such an integral part of the way we learn and process information, children who have difficulty in reading and/or who are poor spellers may have coding problems and should receive a thorough optometric exam to rule out poor visual skills in all areas of vision function including input, processing, storing, retreival and output.

According to research, it is clear that individuals already labeled dyslexic, reading or learning disabled, as well as children experiencing academic difficulties can all benefit from optometric intervention, such as vision therapy.

Though there is no age restriction for treatment, it is important to realize that the earlier patients can be treated, the more vision therapy makes an impact in academic performance because the longer a person goes without treatment, the farther they get behind in school, the lower their self esteem and the longer it takes to change poor learning habits or compensations.

Not all optometrists specialize in learning related vision problems. Out of those that do, not all of them specifically screen for dyslexia, though they recognize if it is there. To find an eye doctor in your area that specializes in learning related vision problems, click here.

An important note to remember

Though it is an optometrist's responsibility to help diagnose and treat children who manifest some type of visual dysfunction, and that visual dysfunction can make learning and reading more difficult, it is important to reiterate the fact that optometrists DO NOT treat learning or reading disabilities. There are learning specialists and special educators that specialize in learning disabilities. Vision therapy can be an effective method in improving academic performance, but often a multidisciplinary approach with other professionals dedicated to working with these kids is the best course of action.

To learn more about vision therapy, click here.




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