Dyslexia is the widely recognized optical and neurological condition that causes difficulty with reading, spelling, and writing. Letter and number reversals are common signs of dyslexia.
Deep dyslexia is a less common condition that provides evidence of the close relationship between speech and writing. With deep dyslexia, a person will see one word and verbalize a different, but closely related word.
In the book Word Weavers by Jean Aitchison the example is given of a person reading the word play instead of 'drama', ill instead of 'sick', football instead of 'soccer'.
This example illustrates that "at some deep level, the patient has understood the word he or she is reading, then been unable to retrieve the phonological shape needed to utter it."
I had never heard of deep dyslexia but I think it would be fascinating to study for anyone in the fields of cognitive linguistics and/or neurolinguistics.