The eyes being reflective are proof that a Soul is inside of the body in The Host, and is used as verification by both Souls and humans:
"Look, look, look!" he says. He pulls a small cylinder from his hip pocket and twists the top. A beam of light shoots out the end.
He turns the flashlight on his face.
The light makes his skin yellow. It shows the prominent cheekbones beside a long thin nose and a sharply squared-off jaw. His lips are stretched in a grin, but I can see that they are full, for a man. His eyebrows and lashes are bleached out from the sun.
But that's not what he's showing me.
His eyes, clear liquid sienna in the illumination, shine with no more than human reflection. He bounces the light between left and right.
The Host, chapter 4 (page 35)
This seems like it should have some sort of significance - the phrase 'the eyes are windows to the soul' comes to mind - but I don't know what the significance could be. So:
Is there a significance to this? If so, what?