Your first question is really general because they can ask you about EVERYTHING: health care issues, why you want to to this or that, describe an interesting clinical case, who is the President of France (Mass E&E asked me this one), etc.. Be prepared for everything!
Some programs had 1. Most programs for ophtho had 2 interviewers. Some had a committee.
I think the who is the President of France was the biggest curve ball. Most questions were straight forward.