Dyslexia and Vision Rehabilitation

Dyslexia and Vision Therapy

Dyslexia is word frequently tossed about when children have problems reading or learning. Commons complaints that lead to the use of the word include letter reversals, poor reading comprehension and decreased reading fluency. These symptoms are also recognized as possible vision related problems cause by poor eye movement accuracy.

Is dyslexia a vision problem or a language problem?

Attempting to define dyslexia can be confusing. The origin of the word is vague: “dys” meaning difficulty with and “lexia”  meaning reading lends itself to broad interpretation.  The best definition for dyslexia, from the International Dyslexia Association says:

“Dyslexia is a specific learning disability that is neurobiological in origin. It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge.”

The research shows that the root cause of dyslexia is phonological processing, or how the brain processes sounds in language. Additionally, the prevalence of dyslexia is estimated to be between 5-20% of the population, according to the National Institute of Health: http://www.ninds.nih.gov/disorders/dyslexia/dyslexia.htm. *

Reading is a complex process involving language, speech, memory and other processes, but all of these processes assume that the collection of the information to be processed is accurate, ie that the eyes work correctly and move accurately. We do know that poor eye movements lead to poor processing skills because the data to be processed was not collected accurately.

Does vision therapy treat dyslexia?

This is also a very interesting question. In our vision rehab practice, we frequently get children referred to us that have common symptoms of dyslexia and visual processing difficulties like reversals and poor reading skills. Following the interventions, the children have reduced symptoms and most have improved reading fluency.

Some of patients do continue to have problems in reading although they show improved eye movements. At this point, we may further assess the patient using a dyslexia screening tool that can identify specific errors related to the processing parts of reading such as the decoding and encoding of words. When results indicate, we refer those children to specialists like our friends at Read-Write Learning Center at  that specialize in the treatment of dyslexia.

 

Does vision therapy treat dyslexia????

NO. Vision therapy cannot treat dyslexia. But it does improve the accuracy of eye movements eliminating many of the symptoms generally associated with dyslexia. With these eye movement problems gone, an accurate assessment of the visual processing skills and reading fluency is now possible, allowing for an accurate diagnosis of a visual processing or other reading and learning problems.

Here is a video case study describing the process.


*Special thanks to Hunter Oswalt, Director of the Read-Write Learning Center for her input on editing this post.

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Visual Processing Disorder

Visual Processing Disorder

Visual Processing disorder is broad term used to describe children that have difficulty with visual tasks. They may have problems with puzzles, mazes, handwriting or reading. The child may be clumsy and have difficulty remembering things like where toys are located. Visual processing problems can be different in each child. Here is a symptom checklist that might help.

Sensory Processing Disorders

Visual processing disorders are part of a larger group of disorders called “sensory processing disorders“. Sensory processing disorders can be linked to any sense (touch or hearing, vision, taste or smell) and are characterized by the brain magnifying or muting sensory information. This magnification or muting of the sensation can appear a child that does not like loud noises, or constantly likes to touch rough surfaces. They may be picky eaters because some foods “feel funny” in their mouths or they only wear their favorite super soft shirt.

These sensory difficulties can cause problems with fine and gross motor development as well as academic performance and cause behavioral issues as well.

Causes of Sensory Processing Disorder

Research continues to identify causes of these disorders but no real conclusions have been found. There are differences in brain structure noted in these children and environmental toxins have been linked to these disorders.

Treating Visual Processing Disorder

Children diagnosed with visual processing disorder should first have complete eye exam including a binocular vision exam. Children with visual processing disorders and other sensory disorders are frequently found to have eye movement and near vision focusing problems that only a binocular vision assessment can uncover. Treatment for the eye movement and near vision focusing problems can frequently reduce the symptoms associated with visual processing disorders.

Following resolution of the eye movement problems, we can ONLY THEN begin successful treatment of visual motor integration and visual perception problems.

Neurological Events and Visual Processing disorders

Recently, I have had several children referred to me recently with “visual processing problems” that also have histories of seizure disorder and concussion. These children also had significant binocular vision problems. Once their binocular vision disorder was correctly diagnosed (both had CI, accommodative dysfunction and saccade dysfunction) and treated, we then able improve visual processing for both of these children.

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How do we see up close?

The Near Vision System

“I can’t see the board” is a common reason children come for their first eye exam. But problems seeing close are more closely related to academic success then distance vision problems. With more computer use, and frequent changes from looking at the board to a notebook, school can be a workout for the near vision focusing system.

Watering eyes, rubbing eyes, and headaches are early signs of discomfort with near vision. These soon lead to difficulty reading and falling grades. The child may also show avoidance behaviors when trying to do school work as it is physically painful to see up close. But worst of all, the child may not say anything at all, as they do not know that their vision is not working right. Typical school vision screenings may miss the problem also.

The near vision system is a balance of several processes…

So what are the mechanisms involved in near vision focusing??

There are 3 processes involved in near vision focusing. Optometrists call it the near vision triad.

1) Pupil constriction- as an object moves closer, the pupils constrict to improve focusing of incoming light to the fovea. The fovea is an area on the retina with the highest density of light receptors. This area gives us our most acute vision.

2) Accommodative Convergence– as an object moves closer, the eyes move nasally to keep the object on the fovea. Both eyes should smoothly convergence together as the target moves closer.

3) Accommodation– lens of the eye focuses- In humans under 40 years old, the lens of the eye changes focus as objects move closer. This is much like a camera lens. As children, the lens is very flexible allowing for a large focusing range. After 40, the lens tends to become less flexible, so we end up wearing bifocals.

Here is a great example of it all working together:

As something moves toward us, the brain adjusts with the right amount of accommodation and convergence, in addition to the pupil constriction. The amount of both convergence and accommodation can be calculated by the the optometrist to come up with the AC/A ratio. This number gives the optometrist clues to the efficiency of the system.

What does it look like when it does not work right??

 

In some children, both of the lenses tend to over focus making them work very hard to maintain focus of near vision objects. The optometrist can assess this and improve it with glasses also. The child with accommodation problems will be rubbing his eyes during close work. He might complain of headaches when reading. He may show poor comprehension and poor reading skills. Or he may not show any of these signs. He may have a short reading span, or have a difficult time hold still, perhaps mis-identified as ADD.

Without enough convergence, the muscles that focus the lens tire as they work to keep near things in focus. They cause similar problems as poor accommodation and frequently a child will has both. This multi-process system is very flexible in children. Therefore, some children have problems coordinating the system. The condition is called convergence insufficiency and is a common vision problem in children. There will be a separate discussion of CI later.

This is easy to screen using the Near Point Convergence test .  

Only the optometrist can identify these problems, but as therapists, teachers and parents, we need to be aware of the signs of near focusing problems. The Convergence Insufficiency Symptom Survey  is a well researched tool that is very effective in identifying patients with possible CI.

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