• Students will be able to explain how light energy converts into sensory signals.
• Students will compare the anatomy and physiology of rods and cones.

Rods and cones are the functional units of the retina, allowing us to see the world around us. Students will use measurements of their field of vision to map the distribution of rods and cones on their retina and discuss the anatomy and physiology that makes sight possible.

Teacher Preparation

Gather materials for the rods and cones mapping activity. Print each student a Rods and Cones Lab Notebook.

Phenomenon Activity
Use the Rods and Cones Slide Show to lead students through the activity. To start, have students imagine they are sitting at the center of a clock. Students will be positioned facing the screen in the 12 o’clock position (they will change their position several times during the activity).

• Slides 3-12: have the students focus directly on the center of the video screen used for the slideshow.
• Slides 14- 23 Students will rotate 30 degrees or imagine that their belly button has a clock hand coming out and point it at 1 p.m.
• Slides 25-34: students will rotate 60 degrees or point the clock hand at 2 p.m.
• Slides 36-45: Students will rotate 90 degrees or point the clock hand at 3 p.m.

For each slide, give students three seconds to observe each one. Ask students to record which circle they think is on top and record it in the table in the Rods and Cones Lab Notebook. After each round, go back and discuss the correct answers. Ask students to record the number of answers they got right in the lab notebook. After the slide show, ask students to graph and analyze their responses.

At the end of the activity, use the discussion questions to analyze students’ experiences. Ask students to fill out the K and W columns of the KWL chart.

Lesson

Provide students with the Eye Anatomy Printable. This can be used later as a quiz if needed. Ask students to fill out the parts of the eye using the diagram in the slideshow.

Ask students to share what they recorded in the K and W columns of the chart. Lead into a discussion about vision using the Rods and Cones Slideshow. Use the following questions to start the discussion:

• Where does vision start?
• What is the evidence for (or against) this thought?
• Are you misrepresenting the evidence or are you making any assumptions?

Continue through the slideshow to help students understand how vision works. When finished, ask students to fill out the L column of their KWL chart to record what they learned.

Note: Listen for words relating to eye anatomy: cornea, rods, cones, lenses, retina, iris or pupil. Also, look for knowledge related to light: photons, absorption and reflection.

Mapping Cones and Rods
Develop and use a model: After introducing and discussing the anatomy of the eye and retina, students should be ready to map their rods and cones. Use the Rods and Cones Slideshow as well as the Rods and Cones Lab Notebook to lead students through a modeling activity.

When your students finish this activity mapping rods and cones, use these discussion questions:

• Considering what we learned in this lesson, what did you learn about looking directly at someone when they are speaking?
• Is it easier or harder to see changes if you have something interfering with your vision?

Note: For students who have not yet studied optics, this video can provide extra assistance.

The Sanford Connection
The Sanford Lorraine Cross Award honors a researcher or research team for breakthrough innovations that directly affect global health. Sight is something many of us take for granted. Jean Bennett, MD, PhD, and Katherine High, MD, developed a gene therapy treatment for blindness and won the inaugural Lorraine Cross Award in 2018. Learn more about their decades-long collaboration and their groundbreaking research here.

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