Usually, the pupils in each eye dilate or constrict simultaneously. When they do not, the pupils may appear to be different sizes. In this article, learn about the possible causes for pupils of ...

Muscles in the iris (the colored part of the eye) can tighten around the pupil and temporarily constrict it. When the pupils are less than 2 millimeters (mm), they are considered miotic ...

In low light, your pupils open up or dilate to let in more light. In bright light, they get smaller or constrict to let in less light. Sometimes, pupils can dilate without any change in light.

For years, scientists thought that pupils â those tiny black circles in the middle of our eyes â dilate and become large when we inhale and constrict to their smallest size when we exhale.

By measuring how someone's pupils dilate and constrict in response to changes in ambient light and also while viewing emotive images, the researchers were able to index both parasympathetic ...

It’s also well established that our pupils constrict when focusing on a nearby object, and dilate in response to cognitive effort or emotional arousal. As the German pupil-research pioneer Irene ...