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In this activity, students determine their own eyesight and calculate what a good average eyesight value for the class would be. Students learn about technologies to enhance eyesight and how engineers play an important role in the development of these technologies.

Engineers have created eye devices for people that have vision difficulties, including glasses and LASIK (Laser-Assisted In Situ Keratomileusis) eye surgery equipment. Electrical Engineers have used their understanding of the eye to create a microchip that can be implanted into the back of the eye. The microchip works as a light sensor for people whose natural light sensor does not work. eye eyesight vision LASIK 20/20 lens sight After this activity, students should be able to: Describe vision. Explain how vision is measured. List several technologies designed by engineers to adjust/enhance vision. Each group needs: A calculator 2 copies of the 20/20 Worksheet Our eyes are an important part of our nervous system. What do we do with our eyes? We see the world around us! Why do we have two eyes? Well, two eyes help us see a larger area than just one eye. Each of our eyes sees an object from slightly different angles, allowing our brain to fit two images together to make a 3-D image in our head. These 3-D images help us judge the distance we are from the object. Does everybody see the same? Well, everybody's eyes have lenses that change shape when we focus on something. The lenses become rounder when we look at something close up and flatter when we look at something that is far away. However, not all eyes focus light rays exactly the same. How your eyes see something is called vision. What does it mean to have 20/20 vision? Do you know? Having 20/20 vision means that when you stand 20 feet away from the chalkboard, you can see what the "average" person sees. If you have 20/40 vision, it means that you can only read the letters that someone with 20/20 or "normal" vision would read standing 40 feet away. This means that you actually have to be closer to the chalkboard to read it. Can you guess what having 20/100 vision means? It means that if you were standing 20 feet from the chalkboard you would see what an average person standing 100 feet away would see. You can also have vision that is better than average. If you had 20/10 vision, you would be able to stand 20 feet from the chalkboard and see what an average person sees when they stand 10 feet away from the chart. A hawk's vision is eight times better than a human's — that would be almost 20/2 vision! The eye itself is a ball made up of three layers. The outside layer is made of two parts, the clear cornea (directly at the front of the eye) and the white sclera (gives the eyeball its shape). Beneath the outside layer is the middle layer, called the iris. The iris controls how much light enters the eye. It dilates to let more light in through the pupil and contracts to let in less light. The iris is pigmented and is what gives the eye its color. In an attempt to see at 20/20, some people use glasses or contact lenses. There are also some technologies that have been developed with engineers to try and correct vision. One form of this is LASIK surgery. LASIK stands for "Laser-Assisted In Situ Keratomileusis" and is a procedure that permanently changes the shape of the cornea (the clear part on the front of the eye) by using a laser. The top surface of the cornea is cut and rolled back revealing the middle section of the cornea. A laser is used to vaporize a portion of the middle section, and the flap is then returned to its normal location over the eye. This allows the eye to change shape closer to the way an eye would in someone with 20/20 vision. Today, we are going to learn what our own vision is. We are also going to look at the average vision of our entire class, and think about how engineers design technologies with vision in mind. Print out the Eye Chart (attached). Affix Eye Chart to the wall of the classroom, and mark a place on the floor that is 20 feet from the chart. Make enough copies of the 20/20 Worksheet for each student Ask students what they think 20/20 vision means. Help them brainstorm ideas. Explain to the students that their job as engineers today will be to determine the average or "normal" eyesight for their class and then design a technology that has the class eyesight average in mind. The average will be done by recording the vision of everybody in the class. Have students take turns standing at the 20-foot mark and identifying the smallest row on the eye chart that they can read with their right eye (cover up the left eye), then the left eye (cover up the right eye), then with both eyes together. The small number to the left of the row represents the denominator of the fraction. For example, if the last readable row has a 30 next to it, their vision would be 20/30. Note: If someone has glasses, they can try this experiment with their glasses both on and off. Once each student has measurements for both of their eyes, have them find the average of the two eyes together on their worksheet. (Students can also compare this to the vision of both individual eyes. The results may or may not be the same.) Next, give each student the data for each person in the class. (Note: copy the master sheet, put it up on a transparency, or write results on the board.) 6. Have the students calculate the class average and write a paragraph explaining why they think designs could be based on the class average vision data. Have students share their answer with a neighbor and then see if the class can come to a consensus. With a neighbor, have the students brainstorm and sketch (if time) a new technology for the class that is based on the vision data. Tell the students that they are designing an electronic message board for the teacher to put up homework reminders, upcoming events for the school, and important class news. Have the students think about the average vision of the class, and use that to decide what the message board will look like and where in the classroom it should be placed. Have students share their ideas with the rest of the class. 20/20 Worksheet (pdf) 20/20 Worksheet (doc) Eye Chart (pdf) Eye Chart (doc) If you do not have 20 feet to work with, you can have students read the chart from 10 feet and then convert the fraction to 20 feet. For example, 10/40 would be 20/80. Consider having one person record all of the data on the board or overhead for the rest of the class. You may want to suggest to students ways of finding a "normal" value for the class. The mean (the average), median (the value in the exact middle of the data set), and mode (the most often occurring measurement) are good places to start. Discussion Questions: Solicit, integrate and summarize student responses. Ask the students: Why do we have two eyes instead of one? What is 20/20 vision? Worksheet: Have the students complete the activity worksheet; review their answers to gauge their mastery of the subject. Voting: Ask a true/false question and have students vote by holding thumbs up for true and thumbs down for false. Count the number of true and false and write the number on the board. Give the right answer. True or False: Vision is how someone sees something. (Answer: True) True or False: Everybody's eyes have lenses that change shape when we focus on something. (Answer: True, the lenses of our eyes become rounder when we look at something close up and flatter when we look at something that is far away.) True or False: The "average" person can see 20/30 vision (Answer: False, the average person sees with 20/20 vision.) True or False: The only way to correct vision is with glasses. (Answer: False, there are also some technologies that have been developed with engineers to try and correct vision, including LASIK eye surgery.) Class Presentation: Have the student groups present their electronic message board design to the rest of the class. Ask them to discuss why they chose the design they did and where they would place the message board in the classroom. Informal Discussion: Solicit, integrate and summarize student responses. Ask the students to discuss why understanding vision and how the eye works is important to engineers. Not all animals have 20/20 vision. For example, hawks see 8 times better than humans and a frog's eye has a special set of cells that responds to motion instead of light. Have students research how different animals "see." Have students investigate the difference between nearsightedness and farsightedness. Have students answer the question, "Is eating carrots good for your eyesight?" (Yes, it can be because carrots contain vitamin A, which is used to make pigments in the light-sensitive cells of the eye!) Have students calculate their vision if the average is based on 100/100 vision. This would be accomplished by multiplying the fraction by another fraction to get the numerator to 100. For example, if a person has 20/40 vision, they would multiply that number by 5/5 to get 100/200. International Society for the Enhancement of Eyesight, January 28, 2005 http://www.i-see.org/