You would still see, but your brain would only choose to wake you if it saw something that it decided you needed to wake up for, like some sort of danger. This is the same for hearing - you hear lots of things while asleep but only wake up for the important ones (like someone shouting 'fire'). As Smudge says, this woul dalso depend on how heavy your sleep was.
According to my mum when i was very young i would sometimes sleep with my eyes opened.Yeah i know what your thinking that's freaky.My mum told me the story that 1 night she had some friends over and they had been putting their jackets on my bed & 1 of the girls went to get her Jacket & as she lifted her jacket she saw me lying there with my eyes opened & screamed "Oh My God He's Dead".Even as i write this it still makes me laugh