pupil

The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil. The size of the pupil is controlled by the iris, and varies depending on many factors, the most significant being the amount of light in the environment. The term "pupil" was coined by Gerard of Cremona.

AI overview

The pupil is the black hole in the center of your eye that lets light pass through to the retina so you can see. Your iris automatically adjusts the pupil's size depending on how bright your surroundings are, making it larger in dim light to let more light in and smaller in bright light to protect your eye.

AI-generated from the Wikipedia summary — may contain errors.

Key facts

Anatomy.Caption: The pupil is the central opening of the iris on the inside of the eye, which normally appears black. The grey/blue or brown area surrounding the pupil is the iris. The white outer area of the eye is the sclera. The central outermost transparent colorless part of the eye (through which we can see the iris and pupil) is the cornea.
Anatomy.Image2: Schematic diagram of the human eye en.svg
Anatomy.Caption2: Cross-section of the human eye, showing the position of the pupil.
Anatomy.part_of: Eye
Anatomy.system: Visual system
Anatomy.Name: Pupil
Anatomy.Latin: pupilla. (plural: pupillae)
Anatomy.Image: Eye_iris.jpg

via Wikipedia infobox

Research

35,961 papers

Disorders of the Pupil.ReviewContinuum (Minneapolis, Minn.) · 2025Kawasaki ADOI: 10.1212/cont.0000000000001542
Emotional response in babies' pupil contagion.Journal of experimental child psychology · 2024Tsuji Y, Kanazawa S, Yamaguchi MKDOI: 10.1016/j.jecp.2023.105801
Pupil dilation reveals the intensity of touch.Psychophysiology · 2024Ten Brink AF, Heiner I, Dijkerman HC et al.DOI: 10.1111/psyp.14538
A diagnostic challenge: dilated pupil.ReviewCurrent opinion in ophthalmology · 2013Caglayan HZ, Colpak IA, Kansu TDOI: 10.1097/ICU.0000000000000005
Preoperative pupil fatigue.Journal of cataract and refractive surgery · 1992Power WJ, Hope-Ross M, Mooney DJDOI: 10.1016/s0886-3350(13)80909-1
Atonic pupil after cataract surgery.ReviewJournal of cataract and refractive surgery · 1995Golnik KC, Hund PW 3rd, Apple DJDOI: 10.1016/s0886-3350(13)80505-6
Pupil shape in the animal kingdom: from the pseudopupil to the vertical pupil.ReviewArchivos de la Sociedad Espanola de Oftalmologia · 2014González-Martín-Moro J, Gómez-Sanz F, Sales-Sanz A et al.DOI: 10.1016/j.oftal.2014.04.005
Pupil dilation offers a time-window on prediction error.eLife · 2026Colizoli O, van Leeuwen TM, Rutar D et al.DOI: 10.7554/eLife.105287

via PubMed

Wikidata facts

Image: Iris.eye.225px.jpg

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NCI Thesaurus ID: C33429
Commons category: Pupils (eye)

Sources (4)

via Wikidata · CC0

~18 min read

Article

13 sections

Contents

Function
Effect of light
Clinical significance
Effect of drugs
Diseases
Size {{anchor|Diameter}}
Animals
Evolution and adaptation
Activity pattern and behavior
Society and culture
See also
References
External links

In humans, the pupil is circular, but its shape varies between species; some cats, reptiles, and foxes have vertical slit pupils, goats and sheep have horizontally oriented pupils, and some catfish have annular types. In optical terms, the anatomical pupil is the eye's aperture and the iris is the aperture stop. The image of the pupil as seen from outside the eye is the entrance pupil, which does not exactly correspond to the location and size of the physical pupil because it is magnified by the cornea. On the inner edge lies a prominent structure, the collarette, marking the junction of the embryonic pupillary membrane covering the embryonic pupil.