No, he just acts that way. He even went to The Canadian National Institute for the Blind to learn how to 'act blind' Check out the interview here to see more on what he says about his character. see related link below.
Nobody can tell for 100%... you can have one scientist saying yes they are and one that says no they aren't. :( it bugs me too. Scientist are trying to figure it out but still nobody knows fro sure!...
yes he was. wing to his being born six weeks premature, the blood vessels at the back of his eyes had not yet reached the front and their aborted growth caused the retinas to detach