The size of your pupils varies throughout the day, but most people’s pupils fall within a particular size range. We’ll look at when and why your pupils change size. First, the range of “normal” pupil ...

A person’s pupils may be of different sizes (anisocoria) for several reasons, including physical trauma, response to light, and infection. The condition may also be present from birth. Pupils, or the ...

It is commonly known that pupil size fluctuates in response to brightness and darkness during wakefulness. What is less commonly known is that pupil size is also regulated by the autonomic nervous ...

It has been said that “the eyes are the window to the soul,” but new research suggests that they may be a window to the brain as well. We first uncovered this surprising relationship while studying ...

The pupillary light response helps our eyes see the world around us in various lighting conditions ranging from bright, sunny days to dark, moonlit nights. Like a camera's aperture, this adaptive ...

The pupil controls how much light enters the eye, allowing for clear vision. In low light, pupils widen to let in more light, and in bright light, they narrow to prevent too much light from entering.

You look in the mirror and notice that the dark circles in the middle of your eyes are bigger than usual. What's going on? Those dark circles are your pupils, the openings that let light enter your ...