Please do not read the following if you have never read Oedipus or are unfamiliar with the plot of the play, in case it spoils the reading for you:
In Sophocles' play Oedipus the King, the dramatic irony of much of Oedipus' earlier words is not revealed until we learn from Teiresias that Oedipus is the man responsible for killing King Laius and setting the plague upon Thebes. Early in the play, Oedipus says the following lines:
For whoso slew that king might have a mind
To strike me too with his assassin hand.
Therefore in righting him I serve myself
Here's the source for the edition I'm using, if you're wondering.
My question is the following: could the above lines be considered dramatic irony even though they occur before the scene in which the audience learns the truth from Teiresias? That is, upon reading Teiresias' revelation, could one consider the preceding material to be dramatically ironic, even though one was ignorant of the information at the time it was read?