Eye Anatomy - how the eye works
A guide to the many parts of the human eye -- how and
why vision works and functions
The human eyeball, the organ responsible for the sense
of sight, is a very complex structure. We use our vision
in almost every activity, so the eye is one of the most
important organs in the body.
How vision works
Sight begins when light rays from an object enter the
eye through the
cornea, the clear front “window” of the eyeball. The
cornea is actually responsible for about sixty percent of
the eyeball’s light-ray-bending capability. The cornea’s
refractive power bends the light rays in such a way
that they pass freely through the
pupil, the size-changing hole in the
iris.
The
iris, the structure that gives the eye color, works
like a shutter in a camera. It has the ability to enlarge
and shrink, depending on how much light the environment
is sending into the eye.
After passing through the iris, the light rays strike
the eye’s
crystalline lens. This clear, flexible structure works
much like the lens in a camera – shortening and lengthening
its width in order to focus light rays properly.
In a normal eye, after exiting the back of the lens,
the light rays pass through the
vitreous -- a clear, jelly-like substance that fills
the globe of the eyeball. The vitreous humor helps
the eye hold its spherical shape. Finally, the light rays
land and come to a sharp focusing point on the
retina.
Continuing with our “camera” analogy, the retina’s function
is much like the film in a camera. It is responsible for
capturing all of the light rays, processing them into light
impulses through millions of tiny nerve endings, then sending
these light impulses through over a million nerve fibers
to the
optic nerve.
The optic nerve is sort of like an extension of the brain.
It is a bundled cord of more than a million nerve fibers.
The light impulses travel through this nerve fiber to the
brain, where they are interpreted as an image.
Illustrations and movie by JirehDesign.com
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