Poor Binocular Coordination Of Saccades In Dyslexic Children

Bucci MPBrémond-Gignac DKapoula Z.

IRIS Group, CNRS, Service OPH-ORL-Stomatologie, Hôpital Européen Georges Pompidou & Pôle Chirurgie ORL-OPH, Hôpital Robert Debré, Paris, France. [email protected]

AIM: To examine the quality of binocular coordination of saccades in dyslexic children in single word reading and in a task requiring fixation of single LED. METHODS: Eighteen children with dyslexia (11.4 +/- 2 years old) and 13 non-dyslexic children of matched age were studied. Horizontal saccades from both eyes were recorded with a photoelectric system (Oculomotor-Bouis). RESULTS: Binocular coordination during and after the saccade in dyslexics is worse than that of non-dyslexic children; the disconjugacy does not depend on the condition. Moreover, dyslexics do not show the stereotyped pattern of disconjugacy (divergence during the saccade and convergence after the saccade). The conjugate post-saccadic drift is larger in dyslexics for both conditions. CONCLUSION: Poor quality of binocular coordination of saccades and drift of the eyes after the saccade, regardless of the task, indicates an intrinsic ocular motor deficiency. Such a deficiency could be related to immaturity of the normal ocular motor learning mechanisms via which ocular motor coordination and stable fixation are achieved. Learning could be based on the interaction between the saccade and vergence subsystems. The cerebellum, but also cortical areas of the magnocellular stream such as the parietal cortex, could be the sites of ocular motor learning.

Graefes Arch Clin Exp Ophthalmol. 2008 Mar;246(3):417-28. Epub 2007 Nov 29.

What Is The Mechanism By Which Myopia Develops?

Richard Gallagher in the Ophthalmologist newsletter:

Despite a century of interest in refractive development, the etiology of myopia is still not fully understood. Now, with the prevalence skyrocketing, the search for answers is more urgent than ever.

What is known is that myopia results when an eye is too long for its optical power or optically too powerful for its axial length. The components of the optical system, such as axial length, refracting power of the cornea and depth of the anterior chamber, must remain in sync as the eye grows to ensure that objects are brought into sharp focus. The hypothesized mechanism by which this is brought about is called emmetropization, a term derived from the Greek emmetros, meaning “well-proportioned” or “fitting”. Identifying aspects of the visual experience that might aid, or hinder, the process of emmetropization provides clues as to why myopia develops. Several factors have been identified; the mechanism du jour is that outdoor light exposure helps maintain emmetropia. Spending too much time indoors, and not enough time outdoors promotes myopia.

There are a couple of mechanistic explanations for this indoor/outdoor light phenomenon. These explanations are not mutually exclusive. One is the huge disparity in the level of light exposure. Outside, light level readings are in the range of 50-100,000 lux; indoors, values are less than 1,000 lux, and mostly closer to 500. Increased exposure to sunlight promotes dopamine neurotransmission in the retina; in animal models, dopamine signaling is associated with an inhibition of axial elongation. Thus, a child exposed to a sufficiency of outdoor light is less likely to develop myopia than if he or she spends most of the time indoors.

Another possible mechanism involves peripheral vision. An outdoor vista, such as that experienced at the ocean or in the countryside provides dioptric continuity throughout the visual field: both central and peripheral vision are clear, unblurred. This state may help maintain symmetry of the eyeball, and promote emmetropia. Indoors, dioptric stimuli vary widely across the visual field. Central vision may be focused on a television screen or words on a page, but a wide range of light sources and objects at different distances means that the peripheral retina is likely to be defocused. Studies in animal models indicate that this kind of optically-imposed defocus impacts upon central refractive development: when the periphery of the eye is defocused, refractive errors are more likely to occur. Hence, the child spending his or her time indoors is more inclined to be myopic.

Increased understanding of the factors that influence refractive parameters and how these interact should lead to more effective treatments to slow myopia progression or to prevent its onset.

Question 3. What factors contribute to susceptibility to myopia?

Nature or nurture? There is clearly a mix of genetic and environmental components involved in the development of myopia, but the contribution of each, and the ingredients that make up that contribution, are still being teased out.

Back in 2005, a meta-analysis of some 300 papers downplayed the role of hereditary factors. It noted distinct variations in prevalence between genetically similar cohorts in different environments: for instance, the high prevalence of myopic Indians in Singapore (70 percent of 18-year-old men), while in India itself the rate was roughly 10 percent. The simplest explanation of such findings is that a massive environmental effect is swamping the genetic influence.

So, was mother right when she said, “Don’t stare at the television too long or your eyes will go square”? No. Despite the folklore of “screens damaging eyes,” which has been passed down the generations in the form of watching TV, playing video games, working with personal computers, to today’s use of smartphones, their impact appears to be minimal. What Mother failed to identify is the crystal-clear relationship between education (and socio-economic status) and myopia prevalence in children. “Education” likely means “more reading,” supporting the idea that “nearwork” is a significant risk factor in myopia. Additionally or alternatively, increased indoor activity means less outdoor activity. As noted above, a strong body of evidence links outdoor activities, such as sports (though not indoor sports) and the amount/duration of sunlight exposure, to reduced risk of myopia in children. Thus, for “environmental factors,” read “lifestyle”; an important distinction when comparing myopia incidence on a global scale.

Environmental factors alone cannot, however, explain why so many individuals within a single family present with myopia; there must be a substantial role for genes. Altogether, an extraordinary 68 genes across all chromosomes have been associated with refractive error, including 20-some recent additions from the international Consortium for Refraction and Myopia (CREAM) and the company 23andMe, who corroborated each other’s findings.

Interestingly, no significant genetic differences between Europeans and Asians were discovered. The bad news is that many of the genes have very slight (though additive) effects, ruling out a simple solution. The rather better news is that they can be mapped onto functional pathways, giving pointers on how to improve our basic understanding and, by extension, our ability to treat this perplexing condition. The pathways include neurotransmission, vitamin A (retinol) metabolism, eye development and remodeling of the extracellular matrix.

Rapid progress is being made on the environmental component too. Randomized clinical trials are underway to more precisely pin down the impact of sunlight, bright light, and/or outdoor exposure; some of these studies use wearable light sensors in place of questionnaires to capture data more rigorously.

The ultimate goal will be to integrate the two streams of information, pinpointing unfavorable combinations of genetic predisposition and environmental factors that are particularly risky for the development of myopia. At that point, improved therapeutic options may come into focus.

Commented by our GURU Neuro-Developmental F.C.O.V.D Dave cook: I liked the mention of variation between central and peripheral vision. When you look at a handheld book Smart phone, your central focus is at the distance of the page or screen, your peripheral vision is completely out of focus. The flat world of computer screen, TV, and Books all mismatch central and peripheral focus with our eyes relatively unmoving for prolonged periods of time.

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.

Achromatopsia

We do have supply a special lenses for Achromatopsia , Hemeralopia (Day Blindness) – Extreme Light and Glare Sensitivity.

In order to get a optimum result, you will need to make an appointment to meet our Optometrist in Special interest of this.

The light forces her to squint her eyes in normal room light. Day blindness or hemeralopia can now open her eyes with
the special lenses.

Stroke Visual Expansion Field

HEMIANOPIA(STROKE OF VIEW)
Hemianopia, also known as Hemianopsia is loss of vision in either the whole left or the whole right half of the field of vision. The most common causes of this damage include the side effect of stroke, brain tumour and trauma. Such vision loss could lead inconveniences in life for instance problems with mobility, tendency to bump into objects, falling incidents, unpredicted accidents and reading difficulties.

Results from the National Health and Nutrition Examination Survey (1988-1994) indicated that 1 in 1000 people examined had Hemianopia. At least one third of stroke survivors in rehabilitation have either homonymous Hemianopia or spatial neglect.

If you have found this website we are assuming that you, or your loved one, or a client has been diagnosed with Hemianopia. You just ignited a new hope! What you are reading now are actually the treatment options available in Malaysia to help the Hemianopic patients.

1.  The Peli Lens™, the newest and most effective prism technique that offers more field expansion than any other option; by far: 20˚ in the original design and 30˚ in the new design. These are backed by clinical trials.

2.  Training to scan (vision therapy)

Based on clinical research, patient success rates, field expansion characteristics and cost, the Peli Lens™ represents the best option for a majority of hemianopic patients.  The other methods mentioned here are viable options in the event that the patient does not adapt to the Peli Lens™.

Hemianopic View (Right Blindness)What will be missedThe Peli lens™or“EP” Expansion Prism Lens

A hemianope who has vision only on the left side of both eyes would likely trip over the trash bin because it is not visibleIf we could somehow indicate to the hemianope that there is an obstacle in his blind field, then it could be avoided.

The “EP” or Expansion Prism system.
The “EP” system is designed to help with obstacle detection, especially while moving; it is not a reading aid.
Patient fitting is simple and cost effective using the fitting protocol provided and making adjustments as needed during the training walk with the patient.  The patient then is sent home to adjust for about one month.

• 20 degree field expansion
• 50% acceptance rate at 12 month follow-up
• Clinical-proven result
• Unobstructed central vision
• No image jump
• Cosmetically appealing

Testimonial about Our Vision Rehabilitation CLICK HERE

What’s Really Causing Your Child’s Reading Problem?

As parents, we want the best for our children. We want them to be safe, successful and happy. But for the parent of a child with an undiagnosed functional vision problem, these goals can be frustratingly elusive.

Typically, children who have an undiagnosed functional vision problem struggle with reading and writing. The frustrating part about the condition is that a visit to the eye doctor may not always reveal that there is a problem. In fact, many people with functional vision problems have 20/20 vision and healthy eyes.

What is functional vision?

Functional vision is how the brain, eyes and visual pathways all work together, allowing you to see and interact with the world.

These issues are separate from vision problems detected using a Snellen eye chart — in which you read letters from a wall chart.

The Snellen eye chart tests your ability to achieve normal visual acuity or sharpness of vision.
For most who struggle with this, lenses are prescribed to improve the acuity.

Functional vision, however, involves more than how the eye sees a 2D object like the eye chart. When a functional visual problem is present, one can have difficulty moving his or her eyes, focusing or seeing three dimensional space.

It can also be hard to detect if only visual acuity is being assessed. It’s similar to having a torn meniscus in the knee. Although you are experiencing pain and a loss of mobility, an x-ray may not reveal any abnormalities.

Using the Snellen eye chart for a functional vision problem is the same concept. Like the x-ray, it’s not that the eye chart is inaccurate. It’s just not the right tool for diagnosing the problem.

What are some types of functional vision problems and their symptoms?

Before we get to what is needed for a proper diagnosis, let’s touch on the most common types of functional vision problems:

1. Poor Convergence: When looking at an object, the eyes should aim at the same point in space.  If the eyes can’t focus on the same spot, then double or overlapping vision may occur.

2. Poor Laterality and Directionality: Laterality is the ability to distinguish directions, such as right or left.  Directionality is the ability to interpret shapes when they are in different orientations. People with poor laterality and directionality may reverse letters or struggle to determine “right” from “left.”

3. Poor Form Discrimination: Inability to pick up on small differences between similar-looking objects. Here, the individual may confuse similar-looking words, such as want and what.

4. Poor Span of Recognition: This refers to one’s ability to process larger chunks of text. Someone struggling with a poor span of recognition may have to focus on a single word or even letter at a time.  For this individual, reading can be a slow, grueling, unpleasant experience.

5. Poor Visualization: Visualization is the ability to create mental images, allowing the individual to conceptualize numbers and understand mentally how a word is correctly spelled. A person with poor visualization may have difficulty with spelling, math, reading and comprehension.

6. Poor Tracking: When one follows a line of text in a book or sees a ball travel through space, he or she is employing their visual tracking capabilities. When one struggles in this capacity, he or she loses place easily while reading or has difficulty catching a ball.

7. Poor Orientation: When one’s visual system can’t accurately perceive where they are in relation to surrounding people and objects, they may have clumsiness, difficulty sitting still and poor performance in sports.

8. Poor Focusing: When someone’s focusing system (accommodation) is not working well, they may have difficulty keeping text clear when reading. They may rub their eyes frequently or experience headaches when reading.

Often the individual with a functional vision problem experiences a combination of these symptoms.

What is life like for the person suffering from a functional visual problem?

A functional vision problem turns routine tasks into monumental obstacles. For a child in school, copying notes from a chalkboard or reading a textbook – things that come easy for other students – are incredibly difficult.

How is it best treated?

Vision therapy can address the root causes of functional vision problems. It uses activities that improve the visual skills that aren’t working well and eventually “teaches” the visual system to work efficiently.

The activities integrate a variety of treatment devices including lenses, prisms, optical filters, computer software, visual-motor-sensory integration training devices and more.

Vision therapy, conducted during regular office and home sessions, delivers the most effective results for restoring functional vision.

Who is ideally suited to treat functional vision problems and why?

Most vision screenings today involve reading letters on a distance eye chart; they do not measure one’s functional vision.

Performing a functional vision test requires special training and equipment. The developmental optometrists at The Vision Therapy Center are optometrists with this extra level of training.  They can perform a comprehensive assessment of visual information processing, binocular function and other visual skills.

Like any health concern, being able to successfully treat a functional vision problem begins with an accurate diagnosis. After all, you can’t treat the symptoms of a problem if you don’t know the cause.

The Neuro-Developmental Optometrsist at The Vision Therapy Center and Sun Time Vision specialist are experts at both diagnosing and treating functional vision problems, enabling patients to be successful in school, work and life.

But the first step toward the cure – and ending your child’s struggles in school – requires evaluating the problem.

 Click Here to schedule an appointment or  please call us at +603- 2110 3967.