Why do eyes glow in fantasy when someone uses magic?

Not always, my friends and I write fantasy and we generally think that's a dumb effect. I guess it's one of the easiest ways to convey the message that some intense **** be goin' down... haha. The eyes are the windows to the soul, so it takes a lot of power to draw the magic from the soul and use it or something...? That's my best guess.

I don't know that I've ever actually seen that in fantasy (Aang's Avatar state in Avatar: The Last Airbender aside). I suppose it would be used to show, er...power and...mystical...stuff? XD Seems silly to me.

You mean, like in "The Last Airbender" movie how his eyes glow white?

Haha! I don't know. Drama?

part of story to show magic

to show the intensity.

because it's cool. I'm serious.