I once banged a chick that used to do something like that during sex; she'd roll her eyes into the back of their sockets and get that "dead in the eyes" look similar to this:
I don't know if she had a hyper-senstive pussy but just fingering her would send her into this kind of frenzy, then after she came, she'd always pass out for about 7 seconds. She also slurred a lot when you'd be banging her saying stuff like "Yeaahhhharghawwwfuck!"