I found a study on Reuter's health that freaked me out. The study talks about night blindness in kids and how some kids' eyes don't adjust to the dark, they are just blind.
I do not have this and neither do my kids. I thought it was fascinating, though, because I have trouble seeing in the dark for quite a long time after the lights go out. My husband thinks it's funny that “Miss 20-20” can't see in the dark. I, of course, do not. I'm not quite as freaked out as the little kids in this study, most of the time, but it is not fun.