I've noticed that about young people; their eyes often show red-eye. Wide open pupils and lots of blood vessels illuminated in the back of the eyes. Older people seem to exhibit less red-eye.
Mind you, cats do the same but differ according to type of cats.
We have a "black" and white cat with green eyes and he shows NO red eye at all; just reflects back like a mirror. The other one is a bit Siamese, with blue eyes and she stares out bright red with a flash.
I try to take pics of them with an indirect flash but I have to keep my hand in front of the camera flash so their eyes don't show any reflection and let the slave flash do the illumination. The problem with THAT is that my camera puts out TWO flashes 1/10 of a second apart, (to get an accurate light measurement before opening the shutter). It's just enough time for them to close their eyes from the first flash!
And those red-eye flashes ...
Yeesh! They carry on so long, everyone has their eyes half closed by the time the camera snaps!~