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The first step in understanding glaucoma is to know
about the eye and how it works. The eye is like a camera, focusing light
and relaying the image to the brain. The brain then processes this
information into the "pictures" we see.
The outer layer of the eyeball is made up of the
sclera and cornea. The sclera is a thin, yet tough, protective shell
which is the "white of the eye". The transparent front portion
is called the cornea. The cornea allows light to enter the eye and with
the lens focuses light on to the retina.
Behind the cornea is the colored iris. The pigment
in the iris determines the color of your eyes. The pupil is the black
hole in the center of the iris, controlling the amount of light entering
the eye. In this way it acts like the diaphragm in a camera.
In bright
conditions, such as outdoors on a bright, sunny day, the iris constricts
the pupil and makes it smaller. This limits the amount of light that
passes through the pupil to the retina at the back of the eye. In darker
conditions the iris dilates the pupil so that more light can enter the
eye.
The lens is behind the iris and focuses the image
onto the retina. Cataract is a condition where the lens fibers become
brown and cloudy and blur your vision. The retina is a thin, transparent
membrane that coats the back of the eye. It is similar to the film in a
camera. The retina sends over one million nerves through the optic nerve
to the brain. These nerve fibers transmit signals to the visual part of
the brain, which processes them into a "picture," or visual
image. Glaucoma damages these nerve fibers and causes them to die.
The outer coating of the eye is "floppy"
like a beach ball. A clear watery fluid, aqueous, is produced inside the
eye by the pigmented cells surrounding the lens (the ciliary body). This
fluid provides the necessary pressure to help maintain the shape of the
eye. We call this pressure the intraocular pressure (IOP). It also
nourishes the cornea and the lens, providing them with oxygen and vital
nutrients.
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