I would think that they would not see much with the spot lights in there faces much. Although I have no idea about that. Never heard the girls say much about them seeing anyone.
They are much too polite and diplomatic to single anyone out.
I have only been on stage a couple of times in plays, but yes, it is almost impossible to see individuals with the lights on you.
My brother gives lessons in stagecraft to budding actors and musical artists.
They are taught to pan the audience and smile as if making eye contact, even with the upper tiers and back of house.
I just received a DVD of his Group's production of "Oklahoma!"