To Purchase NEWTON'S APPLE videos and other science stuff,
Begin the lesson by asking students, "Do you know that everyone is a
little bit blind?" Then instruct them to conduct the following experiment
to find their normal blind spot.
On a piece of paper, draw two small stars about four inches apart. Cover
your left eye and hold the paper at arm's length. With your right eye focused
on the left star, move the paper slowly toward you. What happens? Switch
eyes and do it again. Where did the star go? Why do you think this is happening?
Most of us have thought about how difficult daily life would be if we
were blind, so we're careful to protect our eyes. Yet for a million Americans,
there is a sneak thief at work, slowly and silently stealing their vision.
The thief is so clever that the victims don't even know their eyesight
is in danger.
The thief is a disease called glaucoma, a painless affliction that is
the second leading cause of blindness in the United States. Glaucoma is
a disease of the plumbing system of the eye, a system that most people
don't even know they have. A normal eye is filled with a fluid, called
aqueous humor, that constantly flows through the pupil (the dark, central
part of the eye that lets in light) and over the iris (the colored ring
of tissue around the pupil that gives our eyes their color). The fluid,
produced inside the eye by the skin of the ciliary body (focusing muscle),
nourishes the cornea (the clear front lens of the eye) as it flows out
of the eye through a meshwork of tiny drainage openings at the base of
the iris (where it joins the outside edge of the cornea).
There are several types of glaucoma, but the most common kind occurs
when the drainage openings slowly become blocked over many years. Since
there are no pain-sensing nerves in the region, the increasing pressure
of the fluid is painless.
Even when the drainage openings are almost completely blocked, the ciliary
tissues keep producing fluid. As a result, pressure from the backed-up
fluid starts building inside the eye. This increased pressure pushes on
the optic nerve at the back of the eye, distorting, compressing and, over
time, destroying it, one nerve cell at a time, until blind spots form.
The loss is usually slow, with ever-increasing dimming of vision creeping
in from the side, as if you were looking through a narrowing tunnel or
the room lights were dimming. Many people don't notice this loss in their
peripheral vision, even when 50 percent of the nerves are destroyed. When
they go to an eye doctor and discover they have glaucoma, further loss
of vision can be prevented, but nothing can be done to restore the eyesight
Glaucoma can't be cured, but doctors can prevent further damage by using
drugs in the form of eyedrops or pills to lower the pressure in the eye.
If drugs don't work, doctors can use laser surgery to open the drainage
system and allow the fluid to pass out of the eye. If that fails, microsurgery
is used to create new tubes to allow the fluid to drain out. The best way
to deal with the disease of glaucoma, however, is to detect it early, before
much vision is lost.
1. If you were blind, how do you think your life would be different? How would it be the same?
2. Do you get a glaucoma test when you visit the eye doctor? How do you think the test works?
CATCH THE SNEAK THIEF OF SIGHT
GLAUCOMA: Student Activity
Conduct interviews to determine which older friends and family are at risk for glaucoma.
Between two and three million Americans have glaucoma, and worldwide
it is the second leading cause of blindness. Glaucoma also is the leading
cause of blindness in African Americans. Some people have a much higher
risk of getting glaucoma than others. While glaucoma is rare in young people,
some of the adults you know may be suffering from the "silent sneak-thief
In this activity, you will develop a "glaucoma risk" questionnaire, then interview at least three adults to determine if they should be extra vigilant about getting their eyes checked for the disease.
3. Figure out a system to write down and keep track of each adult's
risk factors. Determine which of them is most likely to develop the disease.
1. Is a person who wears glasses or contact lenses more or less likely to have an undetected case of glaucoma? Why?
2. Are there other eye diseases that are hard to detect, yet also damage vision?
Bantam Medical Dictionary.
Barnes & Noble
concise medical dictionary.(1995)
The Learning Company: Mosby's
Medical Encyclopedia. CD-ROM for Macintosh or Windows.
Interactive Ventures Inc.:
Mayo Clinic Family Health. CD-ROM for Macintosh or Windows.
Dorling Kindersley Multimedia:
The American Medical Association Family Medical Guide.CD-ROM for Macintosh
The Glaucoma Research Foundation
Prevent Blindness America
American Academy of Ophthalmology
Ophthalmic Consultants of
Glaucoma first steals sight by taking away peripheral vision. To get an idea of what that is like, take a black piece of construction paper about the size of regular notebook paper and roll it into a tube. When you hold it in your left hand and look through it with your left eye, it's like looking down a dark tunnel. That's how many people with advanced glaucoma see. Now hold your right palm midway along the tube in front of your right eye. What do you see in your palm?
On a dark evening, go outside and try to look at familiar objects. Can you see them better if you look straight at them or if you look just to the side of them? Why do you think that is?
Look at one word on the page of a book. Without moving your eyes from that word, how much can you read?