The delay in school due to difficulty in reading is one of the most pressing problems faced by teachers, parents and students. Sometimes it will be a true neurological disorder, a Dyslexia, but in many other cases, it will simply be a delay in the maturation of reading learning. Differentiating these two situations is essential to achieve an improvement in the results.

In this article we will see the importance of visual system, both for diagnosis and for the currently proposed treatment programs. We present you two videos where the EyeTracker technique for diagnosis and treatment is shown.

What is Dyslexia?

Dyslexia is defined as a difficulty or delay in learning to read, although other intellectual activities evolve within normality. They are children with an almost normal school performance but with a level of reading that is much lower than that corresponding to their age or intellectual capacity and which is not justified by sensory, neurological or emotional development problems.

dyslexia

It is estimated that between 5 and 17% of the population may be affected with this pathology. We must differentiate between dyslexia that occurs at early ages of life, developmental or developmental dyslexia, with a marked hereditary character and dyslexia that appears as a consequence of a brain injury in the course of life, acquired dyslexia.

The origin of Dyslexia is multifactorial, due to the presence of multiple neuroevolutionary factors involved in learning to read, from phonological disorders, which would hinder the passage of the verbal-visual code to the verbal-auditory code (usually as a consequence of an alteration of short-term memory), even disorders of vision and ocular motility that hinder the correct sequential exploration of graphemes. Each time more importance is given to this point related to the vision, the discrimination of the words and their organization in the sentence are fundamental in the reading, as it is shown in the diagram:

Model of Patterson, Marshall and Coltheart for reading

Model of Patterson, Marshall and Coltheart for reading

This multifactorial aspect of dyslexia determines that children who suffer from it, in addition to problems in reading, also have problems that usually affect spoken language and verbal memory, find it difficult to repeat and remember new words despite having no difficulty understanding Its meaning and in other cases, are associated with hearing problems or motor coordination (draw a straight line) or visual disorders, such as confusing letterforms or difficulty in following the words of a phrase.

Dyslexia and the delay in learning to read

Given the genetic and hereditary character of the disease, an attempt has been made to look for biological or genetic markers that could detect the presence of dyslexia in the initial stages of life, fundamental to take the necessary measures for a better development of these children, but the reality is that there is not yet a specific test that reveals it. For a first screening we must inquire into the family history, when one of the parents suffers from dyslexia, the probability that it appears in any of the children, is from an 25 to an 50%. Another clear sign is the aversion to reading, this difficulty in reading comprehension makes them reject any activity that involves reading. Currently, specific reading tests, tests of cognitive skills and selective study of vision are carried out (parvo and magnocellular pathways that will be discussed later).

Recall that the process of learning to read is between the 3 and the 7 years, First a process of recognition of the form of the letters, of the words, involving the right hemisphere and its posterior regions, which indicates the importance of visual mechanisms in this phase of learning. As the child's development progresses, the reading will polarize in the left hemisphere, where the language centers are located, learn the correspondence between sounds and letters. As a result of this knowledge, there seems to be a consensus when it comes to teaching children how to read and write, attention to spoken words and direct correspondence between letters and their sounds (reading and spelling method) is combined.

The learning process of reading can vary greatly from one child to another, so that in some cases there will be a reading ability that will not correspond to the age or average level of the other children, it will be a simple delay in reading. cerebral maturation, therefore it is very important to distinguish these cases where the difficulty of reading is simply due to a delay in maturation, without brain injuries, of those children who do have brain disorders and it is true dyslexia.

Reading difficulties can appear in situations that have nothing to do with true dyslexia, as is the case of children with attentional deficits, who simply confuse words or parts of them for not paying the attention necessary for a correct reading. Other times there are transient social and emotional problems, such as the separation of parents, which causes a state of "blockage" that hinders any learning process, including that of literacy. In these cases there are no neurological disorders and although it will be equally necessary to help these children, the therapeutic approach is very different. A socio-emotional treatment or specific reading programs are proposed and not demanding more than what can be done in each case

Another of the situations in which we see children with reading deficits is that due to poor vision. The simple fact of not using the optical correction that corresponds or not using the glasses, makes these children do not see well and the reading becomes slower and with a higher rate of errors. In the same way, children with impaired vision of one eye, amblyopia (lazy eye), or with strabismus or simply unstable ocular dominance. These children have problems recognizing words or following their order in the sentence, showing slower reading and errors in word identification. Later we will insist on the subject of vision and the role that ophthalmologists and optometrists play in its detection and treatment.

In all these cases, children have a reading deficit that has nothing to do with the brain disorders that appear in dyslexia and, obviously, should be treated, but with a specific therapy according to each case.

What happens in the brain of dyslexics

Norman Gershwin in Boston was one of the first researchers who was interested to see the changes that appeared in the brain of dyslexic patients. He found that the left temporal region of the brain in these patients, appeared with the same size or even lower compared to the right temporal region, when it is normal for the left region to be larger, since this is where the centers of the brain are located. language, especially speech and reading. Al Galaburda continued the studies of Gershwind and discovered that in the brain of the dyslexics there were groups of cells that had migrated from other regions to the upper layers of the cortex, especially in medial temporal regions, where the language centers and the processing of the He speaks, forming small scars that altered his functioning.

The most recent investigations with neuroimaging show that the layer of white matter that is below the brain surface is thinner in the areas where reading centers are found in dyslexic patients, indicating the functional deficit of these regions.

With neuroimaging it has also been seen that dyslexics have less activation in the main centers of reading in the left hemisphere, a fact that occurs in all dyslexic patients, regardless of the language they speak. The areas with less activation corresponded to those that are responsible for processing the shape of the words and the shape of the sound, a fact that explains the phonological deterioration of these patients.

The researcher Guinevere Eden observed that dyslexic patients, in addition to the alterations of the language centers in the left hemisphere, associated alterations in the activation of the visumotor areas, with a strong spatial component, such as the posterior parietal region of both hemispheres, indicating that these patients have associated disorders of orientation and motor skills, tend to be somewhat clumsier in sports and more difficult to learn by imitation. I also observe that there was a different activation of the prefrontal regions, specific in the decision making and in the resolution of problems, coinciding in children with dyslexia and with attentional deficits (ADHD), an association that we know today is around 40% of the cases, which again indicates the multifactorial nature of these patients.

The involvement of vision in dyslexia is also evident in neuroanatomy studies. Livingstone en1991, showed that the magnocellular layers of the lateral geniculate nucleus are thinner in the dyslexics compared to the normal subjects, while the parvocleral tract layers were equal in both population groups. These findings have been corroborated later by other researchers, confirming the involvement of the dynamic visual pathway in early stages of the disease, which supports the role of the study of vision in the early diagnosis of dyslexia as well as its importance for treatment.

How Dyslexia Is Evaluated: Classification of Dyslexia

Since dyslexia can be accompanied by other disorders, one of the most used forms for its study is through models, question and answer algorithms, which allow us to classify the type of alteration suffered by each patient. The first algorithm proposed was that of James Hinshelwood (1900), in which three different types of reading disorders are identified:

  1. Inability to name letters (Blindness for the letters).
  2. Inability to read words (blindness to words).
  3. Inability to read sentences (blindness for prayers).

These findings made it clear that the reading is composed of independent skills and that each corresponds to a different anatomical basis. From here, new algorithms have been proposed to classify dyslexias, such as the one proposed by Colthear (1981), which classifies them as follows:

Attention dyslexia

When an isolated letter is presented, they can name it normally but, when a letter is presented next to other letters, the difficulties to name it appear, even if the letter is with another color or shaded. The same applies to words, if they occur in isolation or within a sentence.

Dyslexia of inattention

These patients often mistakenly read the first part of the word, "soldier" instead of "padlock".

Spelling dyslexia

Patients who suffer from it read the words only if they spell them (for themselves or out loud), delaying the reading speed. They can often write at a normal pace but when they are asked to read what they have written, then the delay in reading speed appears.

Deep dyslexia

It is characterized by semantic errors, patients read semantically related words instead of the word they want to read: "happy" instead of "Christmas." The nouns are the words that are read with less difficulty while the functional words and the abstract ones or those that do not make sense, are those that present greater difficulty. Written disorders and short-term verbal memory are usually associated. The deep dyslexic can not process information from sound and therefore tries to read using the meaning.

Phonological dyslexia

The only notable symptom is the inability to read aloud sounds that are not words, otherwise the reading may be almost normal. They have problems in the semantic comprehension of the word, they understand what they read when they hear the word, when they pronounce the words, by way of sound.

Superficial dyslexia

In this case, words cannot be recognized directly by their meaning, but they can be understood using letter-sound relationships, that is, only if the word is pronounced. If the words are regular, an almost normal reading is produced but when they are irregular or complex, problems begin in reading, even in spelling. Superficial dyslexia does not develop in those languages ​​that are totally phonetic, such as Italian, while in those that are not, such as French or English, if it is especially pronounced and children have greater difficulty learning to read.

From a clinical point of view and more focused on treatment, we can differentiate two types of dyslexia, those that affect the ability of the subject to analyze the visual features of the written word (peripheral dyslexia or dyslexia of the visual form of the word), and those that affect later stages of the reading process, associated with the extraction of sound or the meaning of print (central dyslexias).

The peripheral dyslexias

They would be the phonological type and are characterized because patients pronounce on the basis of a partial knowledge of the relationships between spelling and sound. The following points stand out:

  • Semantic interpretation is based on pronunciation and not printed.
  • Frequent confusion among heterograph homophones.
  • Great difficulties to read complex words, consonant clusters, vowel digraphs or ambiguous letters whose phonic value depends a lot on the graphemic context. These patients can read isolated words and passages in prose smoothly, provided they are regular. Regular words are read as regular non-familiar words by applying the corresponding most common sound orthography of the language, so tampThey have a problem with meaningless words. This pattern has as its common cause the exclusive use of the non-lexical (phonological) route in reading, because the visual route is damaged.

The central dyslexias

They depend on processing operations subsequent to the initial visual analysis of a printed word and can be both superficial and deep. This type of dyslexia has been subdivided into different categories according to the pattern of individual errors committed by the patient, according to the reading model used. Within this group we could highlight the phonological dyslexias, in which sometimes they do not seem dyslexic if their visual vocabulary is very ampmess. Their disorder is only evident if they are asked to read not words. The most outstanding features are:

  • The reading of words is practically intact.
  • They have great difficulty reading non-words.
  • Visual errors
  • Deviative errors.
  • Difficulty with functional wordsThese patients had a lesion in the parietoccipital regions of the left hemisphere, including angular rotation and with some extension in the subcortical structures.

Vision analysis in the diagnosis of Dyslexia

The study of vision to help in the diagnosis of dyslexia and reading disorders in general, is polarized into five points: study of the parvocellular pathway, study of the magnocellular pathway, study of binocular vision and stereopsis, study of the vision of the colors and, study of the ocular saccades during the reading.

Study of the parvocellular pathway

It consists in studying the patient's refraction and visual acuity, differentiating angular and morphoscopic visual acuity, with letters and numbers, presented in isolation or in groups of 3 to 7 units (respectively). The contrast sensitivity, with high, medium and low frequencies, both with sine wave bars and with significant cognitive stimuli (letters, numbers or drawings).

Dyslexic patients usually have good parvocellular vision. Once corrected possible refractive disorders (myopia, farsightedness o astigmatism), visual acuity is good, especially angular. In some cases problems can appear in the vision of the letters or numbers that are in the middle part of a line of several units (orfoscópiica vision). When we present that isolated letter, they see it well but, when it is presented next to other letters, it takes longer to answer or it is wrong more frequently.

Contrast sensitivity is usually good for high and medium frequencies, especially when performed with sinusoidal bars, showing a lower level at low frequencies, especially when studying with letters or numbers.

Magnocellular study

It consists of the study of dynamic vision, motion detection, with specific tests that analyze the response speed (reaction time), before stimuli that appear in different positions on a computer screen, as in the detection of moving stimuli. on the screen, with different shapes, sizes and speeds, like the ones we do in our Visual Neurostimulation Unit. We have an example in this video, where the movement followed by the eyes and the time of fixation about the stimulus.

In dyslexic patients, this type of test shows poor results, especially when we increase the eccentricity of the stimuli used and the speed of movement. One of the tests that allows a quick, reliable study that can be applied to young children is the study campmetric with double frequency stimuli. These types of stimuli are independent of the degree of vision of the patient and are only detected by the magnocellular route. In patients with dyslexia appears altered in a very high percentage. 89%, with a high degree of sensitivity and specificity.

Study of binocular vision and stereopsis

It is important to verify that patients have a good alignment of the eyes a good fusion and stereopsis. For its study it is used from the cross of Madox to the modern computerized equipment that allow even the analysis of the binocular and stereoscopic vision in dynamic conditions.
The analysis of binocular vision and stereopsis allows us to differentiate cases of dyslexia from other types of reading disorders. In cases of strabismus and amblyopia, there is a clear impact on the raised vision, stereopsis, while in dyslexia it may be affected, but the published data indicate a percentage that does not exceed 20%, as long as it is not associated dyslexia to strabismus or amblyopia.

In cases of dyslexia that present alterations in stereoscopic vision, improving this achieves a significant improvement in reading, contributing to other specific treatments obtaining faster and more effective results.

Study of colors

It is based on the Ishihara tables and the Fransworth test, with its classic versions or integrated into computer programs that allow to better objectify the way of realization and the analysis of the results.

In dyslexic patients there may be a certain disorder in the detection of colors, but it is more frequent in patients with reading disorders without a neurological basis. We see it in patients with alterations in the retina, in the macula and is usually accompanied by other signs such as poor central vision, scotomas that appear in the campor visual. It is useful to establish the differential diagnosis.

Study of ocular saccades

It consists of analyzing ocular, static and dynamic motility, focusing in this case on the detection of eye movements during reading. In normal situation there are follow-up movements in the words that denote the level of understanding during reading. If visual perception, the detection of letters and words, is parallel to a good semantic understanding, the eyes follow a linear shift to the right (to the left in Muslims), with excerpts from 7 to 9 letters, equivalent to 2º and with an interval between the outputs around 225 msec, although it can be extended up to 260 msec if the difficulty of the text is greater (Rayner and Pollatsek, 1989).

The linear advance is interrupted periodically with a regression of the look backwards, towards words already seen, with excerpts between 9 and 6 characters. This change of direction assumes the 10% - 15% of the saccades and is characteristic of a fluent and correct reading.

Dyslexia and reading

The arrows show the movement and direction of the eyes during the reading. Taken from the original work of Rayner and Pollatsek, 1989.

When changes in the direction of eye movements increase or when the proportion of retrograde movements is greater than 15%, considered normal, it may be due to poor understanding of the text, due to its difficulty, or because there is a disorder in the mechanisms Reading. In these cases, a slower reading is produced with less precision. Under normal conditions, the reading speed is 250 to 300 words per minute (0.2 sec per letter), increasing in dyslexics.

These revealing data were obtained in the laboratory and the problem we had was how to transfer the exploration to the daily clinic, in a simple and effective way. In most centers, the dynamic exploration of the saccades during the reading is done with the simple inspection of the eyes while we read the patient and, although it guides us, it does not allow to objectify correctly what happens in each case, therefore EyeTracker systems have appeared, the same ones that are used for research but adapted for clinical use. The EyeTracker detects the movements of the eyes during reading, as we showed in this video where you can see the movement of the eyes, in blue, and the time of fixing on the words (blue point that increases in size), taxing the whole process and offering a large amount of data on the accuracy in the fixation, fixing time, time of each saccada and space traveled, direction of the saccade, etc. With these procedures, an incipient dyslexia can be detected, classified according to its degree of severity and establishing an evolutionary control of the therapies that are applied.

Current approach to the treatment of Dyslexia

We must differentiate between the treatment to be applied in acquired dyslexia, after a brain injury that affects regions related to speech and writing, where the treatment will be specific to improve the injured areas, the treatment we will apply in the case of developmental dyslexia, those that appear in childhood. In this article we will focus on the latter. It is important to know that although the treatment will be more effective as soon as the disease is diagnosed, it can also treat adults who have reading disorders,

At present we know that there is a high percentage of dyslexics who are not aware of it and who often shows up in the study of some of the children who have the disease, when looking for possible family history. In these cases you can do a specific treatment that improves your reading performance and reading comprehension, if it exists, even in adulthood.

Focusing now on the treatment, the dual approach of reading, lexicon versus non-lexical, is determined by the location of the lesions in the brain and has led to an analysis of dyslexia based on its link with two different neurofunctional mechanisms. they will be of great importance in establishing the therapeutic strategy.

The first line of interpretation is the one proposed by Galaburda and confirmed by other researchers, especially those who provide results through magnetoencephalography. They conclude that the brains of dyslexic children have malformations as a consequence of abnormal migrations (ectopia), in areas linked to phonological processes. The most prominent cortical areas are: perisilvian areas, lower prefrontal region (Broca region), subcentral region, parietal operculum, anterior and supramarginal rotation, posterior and superior superior temporal gyrus (Wernicke area) and occipital temporo region (visumotor areas)

Based on this conceptual basis, compensatory therapies are proposed, based on structured intervention in which sounds are linked to letters and text reading is practiced, highlighting the programs: Fast for Word and Aquari-Soft. The published results are excellent, especially in phonological type dyslexics.

The second line of interpretation proposes that in dyslexic children there are visual dysfunctions related to alterations in the magnocellular pathway, respecting the parvocellular pathway (Greiger and Lettvin 1987). The two neurological pathways carry information from the retina to the occipital areas of the brain, distributing it to other association areas. The parvocellular pathway is responsible for fine analysis of the details of objects, while the magnocellular pathway is responsible for dynamic vision and motion detection.

We have already seen how the changes in vision that accompany dyslexic patients become apparent. They are children who do not have a fluent reading, "the words overlap and there are moments that see them blurred", the excerpts are anomalous, with unstable fixation and continuous changes of direction, looking for words already seen.

These findings are important because ophthalmologists and optometrists can study vision, both in adults and in young children, where it is especially difficult for other professionals, such as psychologists and psychiatrists.

Cognitive and visual treatment of Dyslexia

The current data seem to indicate that, although subjects with dyslexia recruit to a lesser extent in the temporo-parietal regions, which are involved in the reading processes automatically, they can occasionally reach an adequate reading performance at the expense of involving other brain areas, as frontal regions of the right hemisphere and posterior regions parietal and occipital, related to vision, which indicates that the range of possibilities or therapeutic strategies opens up to new alternatives, especially those that use cognitive and visual methods.

Two types of therapeutic strategies are those proposed most strongly at the present time, top-down strategies, cognitive type and bottom-up strategies, of sensoperceptive type (Galaburda, 2006).

Some prominent authors, such as Máximo Etchepareborda (2002) and Tomá Ortiz (2009), point out that the cognitive treatment of dyslexia should be carried out using a dynamic methodology, such as the one we achieve with computer programs, combining these two strategies: (1) Sensory-sensitive stimulation (buttom-up) and (2) Central stimulation (top-down).

Bottom-up Sensoperceptive Programs

These programs are based on the work with multiple verbal-visual stimuli that are projected on the computer screen, using different shapes, sizes and colors, with different location on the screen, in such a way that they stimulate the visual path, with the aim of achieve a better precision and speed in visual discrimination, spatial organization and localization of letters and phonemes in the middle of the words of said verbal stimuli. We try to improve towards automatic reading mechanisms.

In this type of programs, the speed of presentation and the physical characteristics of the same, will be of great importance in the rehabilitation of dyslexia and for this the role played by the ophthalmologist and optometrists, to analyze the level of vision (both static as dynamic) and to adjust the type of stimuli that will be used in neurostimulation programs, as well as the readjustment of these depending on the rate of improvement.

The Eyetracker is the most used tool, both for perception therapies and to perform reading exercises, especially those that combine window and mask techniques. It allows to establish the specific exercises for each case and evaluate their improvement, adjusting again the changes that allow a faster evolution. It has the disadvantage that it requires a very sophisticated technology, expensive and with a very specialized staff and unfortunately not all the centers that treat this type of pathologies have it. We hope that little by little they will be incorporated because their effectiveness is very high, as we have seen in our Visual Neurostimulation Unit.

Top down programs

These are programs that use a wide variety of linguistic, syntactic, grammatical, verbal content, pseudowords, etc. stimuli. The variety and semantic, syntactic and grammatical complexity of verbal stimuli will allow greater activity in the left hemisphere, which is hypofunctional in dyslexic children.

Again the EyeTracker is very useful to configure the tests and evaluate the patient's progression. In this case, the role of the ophthalmologist and the optometrist is also important in order to adjust the visual stimuli with the sound and rhythm of reading. Our experience demonstrates again the high efficiency of these treatments, since we can configure programs based on the videogames used by children, like the one we present here, in which a background image is used, 1 formula cars, which acts as a "distractor" and where verbal and written instructions are incorporated so that the child looks for a point that appears in different areas of the screen and that is moving . These exercises aim to capture the child's attention, they like to perform the exercises because they have fun, which is fundamental in any type of therapy in childhood. Many of the failures in certain treatments are due to boring exercises that do not motivate their performance.

Conclusions

As conclusions of this article on dyslexia and reading disorders, it should be noted:

  1. The importance of a correct diagnosis, differentiating true dyslexia from a delay in the maturation of the learning process of reading.
  2. The need for teachers and parents to be alert to reveal a possible learning disorder that affects reading and writing.
  3. The fundamental role of the ophthalmologist and the optometrist, both for diagnosis and treatment, through personalized computer programs that allow a faster and more efficient recovery, always in collaboration with psychologists and psychiatrists and yes, with fun exercises that motivate to be made. Remember that in most cases we are treating children.
Summary
Dyslexia and visual neurostimulation
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Dyslexia and visual neurostimulation
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Dyslexia and visual neurostimulation are increasingly linked to the development of children with learning disabilities. We explain it to you.
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Área Oftalmológica Avanzada
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