The use of dramatic irony in works with unreliable narrators help to make the purpose of the story clearer to the reader as it allows the reader to understand and better relate to the motivations of the narrator.
Dramatic irony refers to the irony which is understood but the audience but not by the characters in the drama. For instance in the play Romeo and Juliet by William Shakespeare, Audience knows that Juliet is not whereas, Romeo thinks her to be dead.