And very black hair! (...). What traumatizes me the most are her pupil-less red eyes. And its blood-red jaw, as if it had just eaten something." Twenty seconds Alain will never forget!

The RSPCA explains how to tell the difference between the three snakes native to the UK - the adder, grass snake and smooth ...

"Miosis" is a medical term that describes the constriction of the pupils. Learn its causes, symptoms, and how to treat it.

Nocturnal animals tend to have proportionally bigger eyes than humans do. They also tend to have pupils that open more widely in low light. So, at the outset, nocturnal eyes gather more light than ...

The peripheral drift illusion causes us to perceive motion in a still image. A new study shows that the mechanism of this illusion relies on changes in pupil size.