What is Dyslexia?


Dyslexia is a type of learning disability, also known as a reading disability, characterized by an inability to read accurately and fluently and difficulty spelling correctly.

Dyslexia can also be diagnosed if a person reads accurately but very slowly.

The diagnostic criteria for dyslexia have changed frequently, and there are still dozens of different diagnostic criteria in use.

The narrow definition of dyslexia refers to individuals who have normal reading comprehension skills but have problems with decoding (turning letters into sounds), while the broader definition of dyslexia includes all individuals who have problems with decoding, regardless of their reading comprehension skills.

The inability to read fluently can lead to a decrease in reading volume, which can later lead to a decrease in vocabulary and comprehension.

Until now, dyslexia has been misunderstood as a condition with no known cure, an English-speaking condition, an incurable condition, a condition of reading backwards, and a condition of genius.

Currently, dyslexia has been studied a lot and its identity has been almost revealed, and it is said that there are about 5% of dyslexic patients in Korea, just like in English-speaking countries, and they are treated without much difficulty as long as they are diagnosed early.


In the past, dyslexia was thought to be caused by visual problems, but as brain imaging studies and cognitive psychology studies have accumulated, it has been determined that it is a neurodevelopmental disorder caused by the brain’s temperament.

Although genetics is highly influential and often runs in families, several genes are involved, and these genes are known to be involved in the migration and connection of neurons in early development.

Brain imaging studies have consistently reported structural and functional abnormalities in areas of the left brain involved in language and reading.

Structural abnormalities in the brain lead to abnormalities in phonological processing, the ability to recognize and process speech sounds down to their smallest units.

Abnormalities in phonological processing can lead to an inability to learn letter-sound correspondences, or an inability to match letters and sounds and then combine them into meaningful word sounds.

Currently, it has been concluded that left-right brain imbalance, failure of right brain inhibition, problems with general auditory perception (not speech sounds), and problems with balance or sensory integration do not cause dyslexia.


Dyslexia is first recognized by teachers or parents when a child begins formal education and falls behind his or her peers in academic performance.

In addition to reading difficulties, it is often accompanied by difficulties in other areas such as math, attention, and peer relationships.

Children may have delayed speech or inaccurate pronunciation, resulting in late tongue shortening, and lack of reading experience due to lack of interest in learning letters or books.

In the lower grades of elementary school, they make many errors when reading, struggling to read single-syllable words or words with phonological changes, and confusing the order of consonants and vowels in words.

As they reach the upper elementary grades, they tend to omit or substitute when reading next clauses and when reading functional words such as investigation.

They often misspell words, have poor writing skills, and have difficulty memorizing dates, names, and phone numbers.

Even in adolescence, reading is still slow and difficult, so they dislike reading and studying, and their spelling mistakes persist into adulthood.


Dyslexia cannot be explained by intellectual disability or simple developmental delay alone, so an IQ of 70±5 or higher must be present from the beginning of school age, not later.

It must also not be caused by external environmental factors.

A diagnosis should not be made if there is a suspicion of poverty, a non-caring family environment, or insufficient educational opportunities in general.

Vision or hearing impairments, neurological or motor disorders that interfere with the development of academic skills should not be the direct cause.

Learning disabilities often coexist with other neurodevelopmental disorders such as ADHD, communication disorders, developmental coordination disorder, and autism spectrum disorder, as well as other mental disorders such as anxiety, depression, and bipolar disorder.

In these cases, a diagnosis of learning disability can be made, but a learning disability is not diagnosed if the comorbidities are the primary cause of the difficulty in acquiring learning skills.

If dyslexia is suspected through a history and examination, a psychoeducational evaluation is necessary.

A psychoeducational evaluation consists of three parts: an assessment of the child’s intellectual level, an assessment of academic performance in reading and writing, and a neuropsychological evaluation of the information processing abilities that underlie learning.

A child’s intellectual level is typically measured by the Wechsler Intelligence Scale.

If the WISC-IV is administered, a child’s intellectual level may be estimated through an indicator score called the GAI rather than the full-scale intelligence.

Academic achievement tools tell us how far behind a student is in his or her grade level.

The CLT, KORLA, RARCP, BASA, etc. are domestic tests that evaluate the information processing skills underlying learning, and these tests commonly consist of tests such as reading aloud meaningful and meaningless words, reading aloud long texts, phonological awareness tests, other phonological processing tests (rapid naming, working memory, short-term memory), dictation and verbal comprehension assessments.


There is no cure for dyslexia, and it is treated through speech therapy and special education.

Treatment for dyslexia usually consists of phonological awareness training, systematic phonics instruction, decoding training, and fluency and spelling training.

Phonological awareness training is the practice of recognizing, segmenting, synthesizing, and manipulating speech sounds at the phonemic level, the smallest unit of speech.

Systematic phonics instruction involves learning the correspondence of letters and sounds to the pronunciation of graphemes.

In decoding, students use their knowledge of the sounds of graphemes from phonics instruction to practice synthesizing all the consonant and vowel sounds that make up a word when reading it.

Once the child has practiced decoding and can read any word accurately without guessing, he or she can begin to practice reading fluency and dictation by listening to words read aloud.

Objective evidence has accumulated on the effectiveness of interventions centered on phonological awareness and the benefits of early intervention.

Therefore, treatments with poor evidence, such as auditory perceptual training, visual perceptual training (eye movements, Allen lenses, etc.), sensory integration therapy, IM, and neurofeedback, should not be recommended for children with dyslexia.


Prognosis depends on the severity of the student’s phonological processing weaknesses and the strength of other cognitive abilities, including intelligence, that compensate for them.

With early identification and intensive therapeutic instruction, most of the difficulties can be overcome or minimized.

If it is not recognized early enough, it is helpful to teach strategies to circumvent or compensate for the current disability, or to provide assistive technology.

In addition, accommodations such as allowing the student to take an alternative course to the foreign language, extending the time for testing, or allowing the student to take tests orally can help the student gradually develop learning skills and adjust to school.

If dyslexia is diagnosed late or not treated properly, reading and writing problems can persist into adulthood.

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