Why does Sanxingdui's mask have no pupils? What do experts say they might be?

Physiologically speaking, the pupil is a small round hole in the center of the iris of the eye, which is mainly the passage for light to enter the eye and then form an image on the retina, so that people can see things outside. If there is no pupil, that person can't see. So experts speculate that Sanxingdui mask represents a group of blind people.