The iris is a contractile structure, consisting mainly of smooth muscle, surrounding the pupil. Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the …

Small pupils can happen when you’ve had a stroke or when you’ve used opiates, among other reasons. Mydriasis is the name of the opposite condition, having dilated pupils.

Jan 6, 2026 · A pupil is the opening created by the iris, which controls the amount of light that enters the eye. Learn about medical conditions affecting the pupils.

Dec 4, 2024 · Pupils are the dark-colored openings at the center of your eyes that let light in. Doctors can look at your pupils for clues about your health. The size of your pupils and how …

Apr 29, 2023 · The eye has many parts, including the cornea, pupil, lens, sclera, conjunctiva and more. They all work together to help us see clearly. This is a tour of the eye.

Dec 29, 2025 · The amount of light entering the eye is restricted by the aperture in the iris, the pupil. In a dark room, a person’s pupils are large, perhaps 8 mm (0.3 inch) or more in …

Feb 26, 2019 · Typically, the pupils appear perfectly round, equal in size and black in color. The black color is because light that passes through the pupil is absorbed by the retina and is not …

Feelings such as surprise, fear, or attraction can trigger the sympathetic nervous system, causing the pupils to widen. This response is linked to the body’s general state of alertness.

Oct 30, 2023 · Structure of the eyeball seen in a transverse section. The pupil is the small black circle located in the center of the eyeball. Surrounding the pupil is the colored part of the eye, …

Mar 4, 2025 · The pupils are the parts of the eye that constrict and dilate in response to light, controlled by the iris. Pupil-related eye conditions include anisocoria, cataracts, miosis and …