I would echo the previous post's sentiments. The motif of blindness is present throughout the play to emphasize the notion of "sight." Tiresias is blind, but is able to "see" the future and what lies ahead in quite a clear manner. Oedipus, when he has physical sight, lacks a vision of the future and is devoid of the sight of wisdom. His assertion of free will against the notion of fate, his perception that he can solve the riddles of what ails his people, and the assertion of self over other elements help to enhance the idea that Oedipus lacks the sight of wisdom. It is only when Oedipus blinds himself, losing physical sight, that he gains a sense of vision that allows him to better understand himself and the condition in which he lives. It is in this element that a major theme emerges: Knowledge is suffering and wisdom accompanies this pain. It is only through the agony he endures that Oedipus gains wisdom and a sense of "sight" even after losing his physical ability to "see."