Eye Vision
Brief
Students
determine their own eyesight and calculate the average eyesight value for the
class. They learn about technologies to enhance eyesight and how engineers play
an important role in the development of these technologies.
Real World
Connection
Engineers
have created eye devices for people who have vision difficulties, including
glasses and LASIK (laser-assisted in situ keratomileusis) eye surgery
equipment. Electrical engineers have applied their understanding of the eye to
create microchips 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.
Project
Objectives
After
this lesson, students should be able to:
v Describe
vision.
v Explain
how vision is measured.
v List
several technologies designed by engineers to adjust and enhance vision.
Material List
Each
group needs:
v Pencils,
one per student
v Calculator
v Eye Worksheet,
one per student
For
the entire class to share:
v Eye
Chart
Introduction
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, enabling our brains to fit two images together to make 3-D images in
our heads. These 3-D images help us judge the distance we are from objects.
Does everybody see the same? Well, everyone'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? (Listen to student ideas.)
Having 20/20 vision means that when you stand 20 feet away from the classroom
board, 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 can read standing 40 feet away. This means that you
must 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 board 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 classroom board and see what an average
person sees when he is10 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 gives the eye its color. After light has passed through
the cornea and iris (pupil), it is focused by the lens and continues to the
retina, where the light becomes an image that is sent to the brain via the
optical nerve. Figure 1 shows a diagram of the eye, including these components.
Procedure
Before
the Activity
v Print out the Eye Chart and affix it to a classroom
wall. Use a piece of tape to mark a spot on the floor that is 20 feet from the
chart.
v Make copies of the 20/20 Worksheet, one per student.
With
the Students
1.
Ask
students what they think 20/20 vision means. Help them brainstorm ideas.
Present the Introduction/Motivation section content.
2.
Explain
to students that their job as engineers today is to determine the average or
"normal" eyesight for the class and then design a technology that has
the class eyesight average in mind. The average will be determiend by first measuring
and recording the vision of everyone in the class.
3.
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 eyes (cover up the
left eyes), then the left eyes (cover up the right eyes), 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, the
vision is 20/30. Note: If someone has glasses, they can try this experiment
with their glasses both on and off. Remind students to record on their
worksheets their vision ratings.
4.
Once
each student has measurements for both eyes, have them find the average of the
two eyes together, recording this on their worksheet. (Students can also
compare this to the vision of both individual eyes. The results may or may not
be the same.)
5.
Next,
provide every student with the data for each person in the class. Do this by
projectingi a summary sheet on an overhead transparency, or writing the ratings
on the classroom board.
6.
Have
students calculate the class average and write a paragraph explaining why they
think designs could be based on the class average vision data.
7.
Have
students share their answer with a neighbor and then see if the class can come
to a consensus.
8.
With
a neighbor, have students brainstorm and sketch (if time) a new technology for
the class that is based on the vision data. Tell 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 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.
Troubleshooting
Tips
If
you do not have 20 feet of space in front of the chart, have students read the
chart from 10 feet away 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 classroom board or overhead
transparency for the rest of the class to view.
You
may want to suggest to students alternate 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.
Assessment
Pre-Activity Assessment
Discussion
Questions: Solicit, integrate and summarize student responses. Ask students:
F Why
do we have two eyes instead of one?
F What
is 20/20 vision?
Activity
Embedded Assessment
Worksheet:
Have students complete the 20/20 Worksheet. Review their answers to gauge their
mastery of the concepts.
Voting:
Ask a series of true/false question and have students vote by holding thumbs up
for true and thumbs down for false.
Tally
the votes and write the numbers on the board. Give the right answer.
F True
or False: Vision is how someone sees something. (Answer: True)
F True
or False: Everyone's eyes have lenses that change shape when they 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.)
F True
or False: The "average" person can see 20/30 vision. (Answer: False,
the average person sees with 20/20 vision.)
F True
or False: The only way to correct vision is with glasses. (Answer: False, other
technologies have been developed with the help of engineers to correct vision,
such as LASIK eye surgery.)
Post-Activity
Assessment
Class
Presentation:
Have student groups present their electronic message board design to the rest
of the class. Ask them to discuss why they created the design as they did and
where they would place the message board in the classroom.
Informal
Discussion:
Solicit, integrate and summarize student responses.
Ask
students to discuss why understanding vision and how the eye works is important
to engineers.
Homework: Have students draw a
diagram describing vision. Require the diagram to include a light source, an
object to be seen, and the eye viewing the object. In the diagram, have them
label the cornea, iris and pupil, lens, and retina. Additionally, challenge
students to add a second lens (glasses) to the diagram and describe the effect
on vision of the added lens.
Activity Extensions
Not
all animals have 20/20 vision. For example, hawks see eight times better than
humans and frog eyes have cells that are especially sensitive to movement. 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
is accomplished by multiplying the fraction by another fraction to get the
numerator to 100. For example, if a person has 20/40 vision, multiply that
number by 5/5 to get 100/200.
No comments:
Post a Comment