Sparkly eyes?

Have you ever read a book that mention a line like this?
"Her eyes glittered with malice."
or this?
"There was an evil glint in his eyes."
or even this?
"Her eyes gleamed with happiness."

I don't get it.
I've read a lot of books, and this has always stumped me.
Do literature people have the magical power to read the light reflecting off people's retinas?
I most certainly can't tell if somebody is happy or not by looking at the gleam in their eyes.

From what I know, normal people read other people's expressions from little strips of hair above their eyes - eyebrows.

I can't tell if somebody's sad because they tilted their head away from the light.
That doesn't make any sense.

Somebody told me recently that if you carve the pumpkin by cutting out a circle from the bottom instead around the stem, then the pumpkin will stay fresh longer because the stem is its life source.

What the heck?

That's like saying if I chop off a leg from a human corpse rather than a head, then it will rot slower.

I kind of want to try that out.
With the pumpkins, of course, not the corpses.

Also in literature, people tend to snort a lot. Have you noticed that? Somebody makes a ridiculous comment, and somebody snorts. I can't snort. Can you?

But back to the original point- I guess that's why the world isn't run the way books are written.
Otherwise, everybody would be snorting and have anime eyes.