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  2. Polycoria - Wikipedia

    en.wikipedia.org/wiki/Polycoria

    The extraneous pupil is c. 2.5mm away from the principal pupil. In cases of true polycoria there is an intact sphincter muscle, which contracts and dilates the pupils. [5] In an eye without polycoria, the sphincter muscle is a part of the iris that functions to constrict and dilate the pupil.

  3. Iris (anatomy) - Wikipedia

    en.wikipedia.org/wiki/Iris_(anatomy)

    The iris (pl.: irides or irises) is a thin, annular structure in the eye in most mammals and birds that is responsible for controlling the diameter and size of the pupil, and thus the amount of light reaching the retina. In optical terms, the pupil is the eye's aperture, while the iris is the diaphragm. Eye color is defined by the iris.

  4. Human eye - Wikipedia

    en.wikipedia.org/wiki/Human_eye

    Dilation and constriction of the pupil. The eye includes a lens similar to lenses found in optical instruments such as cameras and the same physics principles can be applied. The pupil of the human eye is its aperture; the iris is the diaphragm that serves as the aperture stop.

  5. Pupil function - Wikipedia

    en.wikipedia.org/wiki/Pupil_function

    The pupil function or aperture function describes how a light wave is affected upon transmission through an optical imaging system such as a camera, microscope, or the human eye. More specifically, it is a complex function of the position in the pupil [ 1 ] or aperture (often an iris ) that indicates the relative change in amplitude and phase ...

  6. Iris sphincter muscle - Wikipedia

    en.wikipedia.org/wiki/Iris_sphincter_muscle

    The pupil constricts when the iris sphincter muscle is stimulated and contracts. In humans, it functions to constrict the pupil in bright light (pupillary light reflex) or during accommodation. [citation needed] In lower animals, the muscle cells themselves are photosensitive causing iris action without brain input. [5]

  7. Pupil - Wikipedia

    en.wikipedia.org/wiki/Pupil

    The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina. [1] 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.

  8. Pupillary light reflex - Wikipedia

    en.wikipedia.org/wiki/Pupillary_light_reflex

    The pupil is the dark circular opening in the center of the iris and is where light enters the eye. By analogy with a camera, the pupil is equivalent to aperture, whereas the iris is equivalent to the diaphragm.

  9. Eye - Wikipedia

    en.wikipedia.org/wiki/Eye

    Muscles around the iris change the size of the pupil, regulating the amount of light that enters the eye [3] and reducing aberrations when there is enough light. [4] The eyes of most cephalopods , fish , amphibians and snakes have fixed lens shapes, and focusing is achieved by telescoping the lens in a similar manner to that of a camera .