Flash photos typically produce a red reflection in people’s eyes, but sometimes that reflection can appear white or gray, ...

Medically reviewed by Christine L. Larsen, MD The pupil is the opening located in the center of the iris of the eye. It ...

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.

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 ...

It's caused by inflammation in the uvea, a layer of tissue just inside the outer white part of your eye. The uvea is made up of a layer of blood vessels, a muscular ring that surrounds your pupil ...

Dilated pupils are also caused by drug use, sexual attraction, brain injury, eye injury, certain medications, or benign episodic unilateral mydriasis (BEUM). The size of your pupils can say a lot ...