The following text is taken out of the 'Report of the Task Group on Dyslexia' which is fully available below.
Developmental dyslexia was first described in 1886, in the case of a 14 year old boy who was unable to learn to read. A further study in 1917 attributed such difficulties to “congenital word blindness”. It was not until the 1960s that research moved from the area of medicine into the area of education, with studies into what factors, if any, discriminated between “dyslexic” and “backward readers”.
Since that time, there has been much debate on what causes dyslexia and how it is manifested in those who are thought to have the condition. However, there has been little agreement on a precise definition.
The term “dyslexia” has been generally used within medical/biological research and remains the term preferred by the voluntary groups in this field. However, as Nicholson (2001)21 points out, this implies that “there is a single relatively uniform syndrome”. Current research indicates that this is not the case.
Educationalists, in particular educational psychologists, preferred the term “specific learning difficulties”, indicating that the person had a deficit in some of the processes of learning, but not all. Within the USA, during the 1980s, the term dyslexia was replaced with the term “reading disability”. The consequence of this was a shift from an analysis of the process of learning, to that of the process of reading.
DE - Report of the Task Group on Dyslexia (.pdf)
The Task Group on Dyslexia was set up in January 2001 to audit current provision for children and young people with dyslexia, from nursery level to further education, and to identify training needs and opportunities for teachers.