What is the role of Tiresias in Oedipus?

In their 1678 version of Oedipus, John Dryden and Nathaniel Lee retain much of the central plot, which revolves around the fate of Oedipus as predicted by an oracle. However, Dryden and Lee changed the ending fromthe classical version, Oedipus Rex by Sophocles. Not only does Oedipus die, but another act details the trial of Adrastus for killing Laius, the previous king of Thebes and father of Oedipus. Adrastus is trying to shift the blame away from Laius’s and Jocasta’s daughter, Eurydice.
Tiresias, the blind prophet, plays a prominent role in this version as in the earlier play: it is he who tells Oedipus that he has caused the plague. Rejecting this idea, Oedipus accuses Tiresias of siding with Creon, Jocasta’s current husband. While Sophocles places this exchange at the beginning, in the Dryden and Lee play, Tiresias learns this information near the end from the ghost of Laius. His confrontation with Oedipus in Act III contributes to the king’s suicide.