Teiresias -

One of the interesting character in the play; Oedipus Rex is Teiresias. He is a blind prophet and servant of Apollo, twice was asked by Oedipus to come to the palace to discuss the crisis in Thebes.
In the first act of the play he finally appears, enlightening the reasons for the city’s destruction, knowledge that he is unwilling to reveal to Oedipus for fear of making him miserable. Oedipus, feeling himself to be betrayed by the prophet’s resistance, verbally abuses Teiresias by saying these words;

“You sightless, witless, senseless, mad old man!”

Oedipus also accuses him of working on behalf of the “usurper” Creon.
Reluctantly, Teiresias tells Oedipus that he should not mock him so quickly; in a famous moment of foreshadowing, he tells the king that it is he who is blind:

“But I say that you, with both your eyes, are blind:
You cannot see the wretchedness of your life,
Nor in whose house you live, no, nor with whom.”

Significantly, Teiresias is also the first character in the play to question Oedipus’s assumption that he knows his parentage and to tell him that he has committed killing that he does not yet know are his own. He tells Oedipus that he will become blind and poor, that Oedipus is himself Lauis’s murderer, and that he will learn that he has fathered children with his mother. While Teiresias’s presence on stage is brief, as a prophet representing the god Apollo he remains one of the most powerful characters in the play.

So, the character of Tiresias show the literal blindness of the soothsayer points to the blindness of those who refuse to believe the truth about themselves when they hear it spoken.