How does Sophocles use "blindness" in this story?

One way to approach answering this question is to look at Oedipus and Tiresias, the blind prophet. Although Oedipus, who has the physical ability to see, believes that he can discover the truth about the identity of King Laios' murderer, he is blind to the fact that he himself is guilty. He is also unaware that he has indeed fulfilled another part of the prophecy he tried to escape: married his mother.

Tiresias, on the other hand, is physically blind, but he has the ability to "see" metaphorically; he can make predictions. He also knows the truth about Oedipus' identity, but the old seer doesn't want to reveal this painful reality.

When Oedipus discovers the awful truths, he gouges out his eyes, thus physically blinding himself to the reality around him; he cannot bear to look at the children he has sired, knowing they are his half-siblings.

The play is full of references to sight and blindness, to light and dark imagery. All of these reinforce Sophocles' ideas about truth being a matter of perception.