Vision & Eyesight: Parts of the Eye
The eye is made up of 5 major parts. The image below 
shows the cross section of an eye with the five
parts labeled. Light enters through the clear covering of the eye called the cornea.
It then passes through the adjustable opening in the eye called the iris.
(the colored part) The lens, which is a bit soft and flexible, is supposed to focus the
image of the object onto the retina. The retina is like the movie screen of the
eye. Any image formed on the retina should cause nerves to fire sending a signal
along the optic nerve to be "seen" by the mind.
- Cornea
- The clear covering of the eye. If the cornea is mis-shaped, it may lead to
vision trouble.
- Iris
- The colored opening in the eye. The iris' job is to open or close to adjust
the amount of light that actually enters the eye.
- Lens
- The lens is a converging lens so that it can create a real image on the back wall
of the eye. The lens is actually soft in the middle (like a bag of water) so that
the muscles around it can adjust its shape and focus. This allows us to focus on
something close to us and far away.
- Retina
- The projection screen at the back of the eye. If the image gets focused here,
vision is good.
- Optic Nerve
- The nerve that carries the signal from the retina to the brain. It is also
the cause of the blind spot you have in each eye.
©1999 Science Joy Wagon
