The line mentions <span>Teiresias, the prophet who knew what would happen, and the seeing itself. Even though he is blind, Teiresias sees into the future and the truth of things. Even though he isn't blind, Oedipus doesn't see what he is doing and who he is. His tragic blindness will turn into the actual blindness, in a self-punishing act.</span>
Macbeth is easy to manipulate and Banquo isn't as easy to fool. Banquo can sense something isn't right (like Macbeth is being tricked) :)