One of many studies asked why human eyeballs are much whiter than most animals.
The answer it is proposed it because white eyeballs are important in human social convention
and communication because they allow the other person to see what we are looking at
or get social clues from eye shape and expressions. Bizarrely this just says that in rhyme.

White

Humans, I've read, have white eyeballs
so each can make a distinction
of what others are looking at.
Useful for social convention.
Reptile eyes however are yellow
and anyway look through a slit.
Seems they don't care whose looking
at what, when or how. Not a bit.