When Does Pupil Constricts?

The pupil is the part of your eye that controls how much light gets in. In bright light, your pupils get smaller (constrict) to limit the amount of light that enters. In the dark, your pupils get bigger (dilate). That allows more light in, which improves night vision.

When do pupils dilate and constrict?

Your pupils get bigger or smaller, depending on the amount of light around you. In low light, your pupils open up, or dilate, to let in more light. When it's bright, they get smaller, or constrict, to let in less light. Sometimes your pupils can dilate without any change in the light.

What causes pupillary constriction?

What Causes Pupils to Constrict? Pupil constriction and dilation are controlled by the sympathetic and parasympathetic nervous systems in the brain. Normally, when the parasympathetic nerve is activated, it causes pupils to constrict, or narrow. When the sympathetic nerve is stimulated, pupils dilate.