IIRC the eye can detect down to around 10 photons per second.
>Another interesting thing I read is that the skin gives off low levels
>of light ie we are slightly phosphorescent. Maybe a fully adapted eye
>can actually see that? Last time I was in aq cave with the lights out
>for a while I *thought* I could still see my hand move before my eyes.
I wouldn't trust that one.
A better test would be seeing somebody else's hand moving so you don't "know" where it is. There are still a lot of possibilities for figuring out where it is other than vision.