Applied Science - Science and Math (5B)
Lab

   
OBJECTIVES:
  • Obtaining and interpreting medical data.
  • Graphing the data on a bar graph.
VOCABULARY:
  • astigmatism
  • farsighted
  • nearsighted
MATERIALS:

Students determine their eyesight.

BACKGROUND:

Physicians measure the human body to check the status of its health.  They test hormone levels, size of the fetus (for pregnant women), weight, and many other parts to see if anything is going wrong with the body.

An optometrist and ophthalmologist are two types of people who determine the health of your eyes.  Optometry is the measurement and science of vision care.  Optometrists do not treat diseases of the eye, practice medicine, or perform surgery.  Ophthalmology is the study of the diseases of the eye.  An ophthalmologist or oculist is a physician who can detect and correct eye problems.  Detecting problems of the eye can start with a simple test to see if a person's eyesight is normal.  The test requires an understanding and interpretation of measurement.

This lab gathers data on the eyesight of your students.  It may also help alert parents to their child's need for glasses.  In this activity, students will measure their vision by using a simple Snellen Chart which quickly težls if a person's eyesight is normal.  The chart uses letters like P, S, E, Z, and L that help determine if your eyes are impaired.  The eye chart was developed by a Dutch physician, Herman Snellen, in 1863.  It is designed to be viewed at 6 meters or 20 feet and the patient is asked to read off letters and numbers that get successively smaller with each line read.  In the United States, we use the English system to read the chart. However, it was originally invented and is still used in most countries in the metric system.  Perfect eyesight in a metric country is 6/6 and in the English system, 20/20.  The vision score is expressed as a fraction determined by the last line read successfully.  A score of 20/30 for example, means that from 20 feet away, you can read a line that people with normal vision can make out at 30 feet.  When the second number is larger, it means your vision is not as sharp as the norm.  A score of 20/10 on the other hand, means that at 20 feet you can read letters that a person with normal vision will have to move up to 10 feet to see clearly.  However, when an optometrist or ophthalmologist prescribes new glasses, it is written in the metric system related to the diameter of the lenses.

Variations of the Snellen eye chart are used to test distance vision, first without glasses and later with an assembly of lenses made to correspond to the new prescription.

Astigmatism causes a blurred vision where lines seem to merge.  Without astigmatism, it is difficult to see the same thing a person with an astigmatism does.

PROCEDURE:

  1. Hang several eye charts around the room (in module) and have groups of students test each other.  They should record their right eye, left eye, and both eyes.  Use a piece of paper to cover one eye.  Students should record the information on their lab sheet.  If students find they have trouble reading the chart, assure them that having glasses are only a means to see better.   Mention all the great people in history who have worn glasses from Marie Curie, Einstein, and Ben Franklin to most of our presidents.
      
  2. Use the chart for astigmatism.  There are several examples of these charts on the enclosed sheet.  Instruct students to look at the chart at their normal reading distance.  Look at the illustrations first with one eye closed then the other.  If some sections of the image look blacker or sharper than others, the student may have an irregularity in the curvature of the lens called astigmatism 

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ASTIGMATISM

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