The eye is a complicated organ which allows us to see. To
understand it, we must first look at the biology of the eye. The
pupil is an opening which allows Light to pass into the eye. It
is the dark hole in the center of your eye. The pupil is controlled
by the iris (the colored part of the eye) which is a muscle that contracts
to make the pupil smaller and relaxes to allow the pupil to widen.
The pupils size relates to how much Light there is in a particular
setting. If you are standing outside and the sun is really bright,
then your pupil will get smaller to make up for this. The iris
is covered by the cornea. The lens of the eye is located in back
of the iris. The lens focuses the Light onto the retina, which
acts like a screen. Eyelashes and eyelids protect the eye by stopping
dust particles from falling onto the eye itself. The purpose of
blinking is to moisten the cornea. If the cornea were not kept
wet, it would become opaque.
There are two types of Light sensitive cells on the retina.
Rods, are used for black and white vision, and are concentrated
on the sides of the retina. Cones are used for color vision, and
are concentrated in the center of the retina. Vision is most acute
in the area of the retina known as the fovea centralis.