The following section outlines some sample activities that can be used in the classroom during the eye and ear units. This section provides a brief overview of the activity and resources that are useful for supporting student learning. Additional teacher and student resources can be found under Appendix A.
Modeling of the Eye and of the Ear
Students who are learning about anatomy benefit from multiple exposures to the structure and positioning of these organs. For this reason, it is highly recommended that students are not given pre-labeled diagrams to memorize the labels, but are asked to come up with models and drawings of their own. Students should all create their own drawings of the eye and ear to put into their notes, being mindful of the relative position of all components.
Student generated models for the eye and ear are also relatively strong tools that can be used to facilitate student learning. Students can receive a half sphere of a hollowed Styrofoam ball that can serve as the base for an eye. From there, they can add the anterior chambers and the interior components to complete their model. The same process can be used to make an ear. Modeling clay is a useful and inexpensive tool that can allow students to build structures for both the eyes and the ear. Once students have generated their models, they should explain the structures and functions that are within their model and how they play a role in the detection of light and sound.
The second activity that is highly recommended for studying the eye is an eye dissection. Students can follow along with teacher instructions or use a guided video from the Exploratorium (referenced under Appendix A) as they dissect. Students should make qualitative and quantitative observations about the eye including the differences between the aqueous and vitreous humor, the dimensions of the lens, and the relative thickness between the different layers of the eye.
As students dissect, especially if cow eyes are being used, it is important to point out the relative differences between human and non-human eyes. The cow eye will have a tapetum where human eyes will not. Other anatomical differences may also include the size and the oval pupil shape. If enough musculature is left on the cow eye, it is also useful to denote that the cow eye only has four muscles, allowing it to move up, down, left, and right while humans are in possession of six muscles. This allows the eye to roll clockwise or counter clockwise, providing a greater range of motion past what the cow eye experiences. Students can experience this range of motion for themselves. Have students hold their heads still while their partner draws an imaginary clock around their face. Students should be able to roll their eyes a full rotation.
Eye Disorder Lab Activities
There are several mini labs that can be completed for this unit that allow students to explore the differences between “normal” and “abnormal” vision, as well as tricks that help to point out key features of human anatomy. Many of these items can be done with easy to obtain materials, but Carolina offers a visual perception kit that contains these items and many more. More information about this kit is listed below in Appendix A. As with all labs that look specifically at the ability of the body to perform functions as a test of “normality”, it is crucial to emphasis to students that these classroom lab exercises are not diagnostic but exploratory in this setting. If students are highly concerned about the results of a test they may want to consult their parents or physician.
The first activity requires a Snellen chart—one of the standard visual acuity charts that you see when you go to the doctor’s office. The Snellen chart is used to help doctors determine patient’s visual acuity. A patient is placed 20 feet away from the chart and is asked to read down the lines, starting from the large E, until they can no longer clearly distinguish the letters. Many students may already be familiar with this process from visits to the optometrist. Next to each row is a series of numbers (20/10, 20/20, 20/30, and so on). These numbers are a ratio between the number of feet needed to see clearly for the patient and the number of feet needed to see clearly for an average person. For example, someone who has 20/20 vision is able to see clearly from 20 feet what the average person is able to see clearly from 20 feet. A person with 20/30 vision is able to see the same thing at 20 feet that an average person can see from 10 feet further away, i.e, 30 feet. Someone who is near sighted, however, has a ratio where the second number is significantly higher than the average 20, for example, 20/80.
To perform this test, have students stand at a line 20 feet from the Snellen chart. Students should remove their glasses for this activity as prescriptive lenses will increase visual acuity. Students will cover first the left eye and read out-loud as far down as possible on the chart. A partner is useful for helping to identify letters that the student misses. After, students should switch to their right eye and repeat. The same process can be repeated again with both eyes and with corrective lenses if the student has them.
To look for the blind spot in the eye, the place where the retina attaches to the optic disk that feeds back into the optic nerve, students can use a simple tool. Using a piece of paper that has the blind spot markers on it (usually a dot and a cross), students start by holding their piece of paper at about arm’s length, with their nose between the dot and the cross. Closing the left eye, students should stare at the image of the circle with their right eye. Slowly, students can move the piece of paper towards their face continuing to focus on the circle. At around a foot from the students face, they should notice that the cross that was on the lateral edge of the page has disappeared. This same process can be repeated with the other eye by following these same steps.
Students can experience color vision and color vision fatigue many ways. There are numerous websites that provide examples of what opsin abnormalities might look like and tests that students can take to see if they have color blindness.
A second activity that would require some preparation on part of the teacher is to obtain many different colored flosses or wool yarns and string them on a black cardboard. This activity works best if there are a number of red and greens and blues that are similar in shade but not exact. Students will then need to match strings of floss to the identical bunch on the board without physically holding up the sample. This type of test is a Holmgrem-type color vision test. While not the most accurate test for colorblindness, it can be a useful tool for demonstrating the ability of the eye to detect slight differences in color.
Many students will find that shades of blue that are closely matching are very difficult to distinguish without physically placing the strings on the board, partially because of the location of blue cones in the periphery of the fovea centralis.
The last activity that is easily performed in a lab setting revolves around fatiguing cones. Students should receive a square piece of transparent green or red plastic cut in 3x3 inch squares. Students should look through the plastic with a single eye at a ceiling light (remind students to use good judgement and not to stare into lights that are too bright). For this demonstration to work well, students should make sure that their entire field of vision is covered by the piece of plastic and that they try not to blink. Students should continue looking for 1 to 1.5 minutes through this piece of plastic. When they are done, students should look down at a white surface. What should appear is the opposite color—if the student was looking through red, they should see green and vice versa. This process can be duplicated also by looking at a red and green image on a screen and then turning their gaze to a blank wall.
Simulated Hearing Loss Lab
Students can visit several websites that allow them to experience what it might feel like to have different types of hearing loss. A link for this website is found under Appendix A. Students also have the ability to test their own hearing using a Rinne test (as described above) and to create their own audiograms using a pure tone test. It is important to note that students should be careful never to listen to the same pure tone too loudly or for too long because, as previously mentioned, this can cause damage to the inner ear.
Cochlear Implant Conundrum
An excellent tie-in of culture and community revolves around cochlear implants. Students should be given several articles about the way the cochlear implant works, how effective they are in young children, and also the reasons why or why not to have this procedure performed. Students can also use the visual text
Sound and Fury
in which both sides of the argument are presented.
There are several ways students can share this information. Students may be asked to debate one another about whether all deaf children should be given this surgery.
Or, the scenario can be posed as a role play where a pair of students are the parents of a child who has been diagnosed as being deaf. In this scenario, it is important to establish whether the parents are both hearing or deaf or a combination of the two. Other students should be asked to play the roles of doctors, school teachers, ASL specialists, speech therapists, family and friends (both deaf and not), and other community leaders. The role of the surrounding ensemble is to persuade the family to either give the child the implant or to not have their child implanted. It is also important for students to come to the realization on their own that the family might elect to have their child receive the implant later in life and that this can bring on complications of its own.