I think like with other things, such as allergies or something, perhaps dyslexia can either range from being mild to severe... for example, an old school friend of mine could read and write like your average joe, but admitted that occasionally, through his eyes, it looks as if certain letters in certain words flip-flip as he reads, so when you have a sentence like, "I have a pair of pears", it may end up looking like, "I have a piar of paers" to him.