When the dark circle in the center of your eye is larger than normal Dilated pupils (mydriasis) can happen for many reasons, such as a normal response to light, medication or drug use, eye exams ...

In most cases, pupils change size based on the light and dilate, meaning that appear larger, when you're in a darker room. But your pupils may also change size based on injuries, drug use ...

If you have your pupils dilated for an eye exam, they may stay dilated for several hours. Your eye health provider dilates ...

Two factors, in particular, could reveal a person’s inner state: the length of time it takes the pupil to dilate in response to a flash of light and how the pupil transitions from dilation to ...