Each time a character tries to avert the future predicted by the oracles, the audience knows their attempt is futile, creating the sense of irony that permeates the play.
With the amount of similarities between the two plays Shakespeare must have been inspired by Oedipus and Sophocles when he was writing Othello. He also, is too proud to listen to the gods.
Indeed, the tragic irony of Oedipus terrifies everyone who really thinks it over. Situational Irony is the occurrence of something not expected, usually associated with a pessimistic or fatalistic view. The reader knows that Oedipus exists as the sick one because he killed his own father especially when Oedipus says, "Damned in the blood he shed with his own hand!
Finally, Oedipus goes through a discovery process ending when he discovers his tragic resolution. One would think that a man with as disturbing a prophesy over his head as Oedipus would be very careful about who he married or killed. Oedipus Rex is a tragedy due to the content the Sophocles, the playwright, decided to include, first, murdering his father, king Laius, then marrying his mother, Jocasta, and ending by blinding himself.