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The eye is composed of
the cornea, a transparent window where light enters the eye; and the lens,
which is a crystalline structure that lies right behind the cornea and
focuses the light rays on the retina.
The iris is the colored ring of muscle around the pupil (the black
center of the eye), which constricts or dilates depending on the amount of
light present in the environment and changes the size of the pupil. The size of the pupil regulates the amount
of light by constricting to let in less light and vice versa.
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