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 ...

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 ...

The black circle in the center of your eye is your pupil. It changes size thousands of times a day. When you're in dim light, it gets bigger to let more light in. When you're in bright light, it ...

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 ...