Definition of Iris
Iris: The iris is the circular, colored curtain of
the eye. Its opening forms
the pupil. The iris helps regulate the amount of light that enters
the eye.
The
eye has a number of other key components. These include the cornea,
pupil, lens,
retina, macula, optic nerve and vitreous.
The cornea is the clear front window of the eye that
transmits and focuses
light into the eye.
The pupil is the dark aperture in the iris that
determines how much light
is let into the eye.
The lens is the transparent structure inside the eye that
focuses light
rays onto the retina.
The retina is the nerve layer that lines the back of the
eye, senses light
and creates impulses that travel through the optic nerve to
the brain.
The macula is a small area in the retina that contains
special
light-sensitive cells and allows us to see fine details
clearly.
The optic nerve is the nerve that connects the eye to the
brain and
carries the impulses formed by the retina to the visual
cortex of the brain.
The vitreous humor is a clear, jelly-like substance that
fills the middle
of the eye.
Last Editorial Review: 3/12/1999
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