Vision problems do not cause dyslexia.
Dyslexia is a frequently overused term, and is often mistakenly thought of as reading or writing letters backwards. But the main problem with dyslexia is persistent difficulty with phonics – the ability to attach sounds to letters and blend the sounds into words. Decoding or phonemic awareness are also terms sometimes used to describe phonics ability. Most dyslexic individuals show difficulty with phonics and other aspects of language function. Dyslexia can also make it more difficult to remember sight words.
All children with reading problems are not dyslexic. Vision problems can affect reading, but they do not cause phonics difficulty, which is the hallmark of language based dyslexia.
Vision problems can also make reading more difficult, causing problems with fluency, speed and comprehension. But vision problems do not cause dyslexia. Vision therapy is not intended to treat dyslexia, as is discussed in the American Optometric Association’s position paper on dyslexia and vision therapy. Children with actual language based dyslexia need intensive reading tutoring like the Wilson or Orton-Gillingham methods.
Children with reading problems need a thorough vision evaluation to determine whether there are any vision problems affecting their reading.