Q:
How does the eye work?
A: Like a finely engineered machine, in order for the eye to
see properly, all of the eye's parts must function properly,
all of the eye's parts must function in perfect synergism.
The transparent surface of the eye through which light enters
is called the cornea. The cornea must be absolutely clear.
If the cornea should become diseased or opaque it can be replaced
with a new cornea from a donor, through a procedure called
a corneal transplant. Once the light enters the eye through
the cornea, it passes through a small hole in the iris called
a pupil. The iris works very much like the lens of a camera.
It opens up the pupil (dilates) to let in more light when
it is dark and closes up the pupil (constricts) to let in
less light when it is very bright. Directly behind the pupil
is a clear, gelatin-like lens, wrapped in a clear protective
membrane called its capsule. The lens is responsible for focusing
the images that you see to the back of the eye. If the lens
becomes opaque, then the lens becomes known as a cataract.
Q: How does
the image then get to the brain?
A: The image passes through the vitreous, a clear gel that fills
the eye, and the image is then focused onto the retina at
the back of the eye. The retina records the image, very much
like film in a camera, and sends the image by way of the optic
nerve to the brain. |
Q: How does the retina function?
A: The retina is responsible for changing images into electrical
impulses which are sent to the brain. The retina is nourished
by tiny blood vessels located in the layers in the back of the
eye. There are areas on the retina that are responsible for
different types of vision. One such area located near the optic
disk is the macula. The macula is responsible for straight ahead,
or central vision. Located throughout the retina are light sensing
cells called rods and cones. Cones are responsible for color
and central vision. Rods are responsible for night and side
vision.
Q: How does the movement of the eye happen?
A: Movement of the eyes...up, down, sideways, is controlled
by a set of six muscles attached to the eyeball. To see correctly,
both eyes must move at the same time, the same distance and
the same direction. To do this the brain tells a set of muscles
to pull and the opposite set of muscles to relax...thus the
eye can move in all directions. If the eye muscles are not coordinated
in their movement, double vision may occur. This uncoordinated
movement is called strabismus. If the wandering eye is not corrected,
loss of vision may occur, leading to an extreme case of amblyopia.
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