Dyslexia: A specific developmental disability that alters the way the brain processes written material. Because dyslexia is due to a defect in the brain's processing of graphic symbols, it is thought of primarily as a learning disability. The effects of dyslexia vary from person to person. The only common trait among people with dyslexia is that they read at levels significantly lower than are typical for people of their age and intelligence. Dyslexia is different from reading retardation which may, for example, reflect mental retardation or cultural deprivation. Treatment of dyslexia should be directed to the specific learning problems of the affected individual. The usual course is to modify teaching methods and the educational environment to meet the specific needs of the individual with dyslexia. The outlook varies. The prognosis is generally good, however, for individuals whose dyslexia is identified early, who have supportive families and friends and a strong self-image, and who are involved in appropriate remediation programs.