This is an essential part of feeling connected to the other person when having a face to face conversation
It makes the eyes of dogs shine in the dark when they are feeling happy
Biological light shines out through your eyes in the direction you are looking whenever you are feeling an emotion
It is a weak kind of biological electromagnetic radiation
It is different depending on the emotion you are feeling and the intensity of that emotion
This is why you can feel when someone is staring at you
Just like classic light it can bounce off mirrors, move trough glass, it can be focused by lenses and it is stopped by opaque materials