When Oedipus discovers the truth, he goes mad. Finding that he has fulfilled the prophecy (laying with his mother and killing his father) is compounded by the presence of his children, who are now effectively cursed by the actions of their father.
Oedipus blinds himself with Jocasta's brooches as a self-punishment.
This punishment may be seen to relate to the notion that Oedipus can no longer bear to look at the truth. He has seen more than he can bear. Where he once was a man who boldly demanded to full truth, against the advice of his loved ones, he now is overcome by the truth.
His boldness remains intact enough to allow him to blind himself, but his passion for truth has had dire consequences.