From Wikipedia

Inside Dyslexia

Dyslexia is a learning disorder that manifests itself as a difficulty with reading, spelling and in some cases mathematics. It is separate and distinct from reading difficulties resulting from other causes, such as a non-neurological deficiency with vision or hearing, or from poor or inadequate reading instruction. It is estimated that dyslexia affects between 5% and 17% of the U.S. population.

Dyslexia is thought to be the result of a neurological defect/difference, and though not an intellectual disability, it is variously considered a learning disability, a language disability, and a reading disability, among others. Dyslexia is diagnosed in people of all levels of intelligence (normal to above