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 already lost.
 
 

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? 

 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 of sight."
 
 

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.

 Materials
 
 

 1. Based on the facts listed below and other information you gather from the resource material on glaucoma, develop a list of questions designed to determine a person's risk of getting glaucoma.

• A normal, healthy 65-year-old eye only sees 20 percent of the light that a teenager sees. Any loss in light sensitivity will further diminish night vision. 
• Glaucoma is seven times more likely to occur in blacks than in whites. People of Asian descent are also at a higher risk than those of European descent. 
• People over the age of 65 are seven times more likely to get glaucoma than those under 65. 
• Only 15 percent of people with glaucoma go blind. 
• Between 20 and 25 percent of people with a close relative who has glaucoma will get the disease themselves, especially if both are female. 
• Some people with normal pressure in their eyes can have glaucoma, and some people with high pressure in their eyes don't get glaucoma. 
• The risk of developing glaucoma if you have a family history of the disease is nearly 10 times greater than someone without a family history of glaucoma. 
• About 80 percent of people with glaucoma are over age 60; 31 percent are between 45 and 60 years old; less than one percent are under 45 years of age.
• People who suffer from diabetes or who wear thick glasses for myopia are more likely to get glaucoma.
• People who have had an eye injury are more likely to get glaucoma in that eye, even many years later.

 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.
 
 

Questions

 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?