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Electrooculography (EOG): Measuring Eye Potentials
  • Human
  • Grade 6+

Electrooculography (EOG): Measuring Eye Potentials

Explore how your eyes generate tiny voltage changes as you move them, revealing the hidden signals behind your gaze.

Devices and Accessories2

About the Experiment

What Will You Learn?

What Will You Learn?

• How the steady voltage across your eyes shows up as a signal when your eyes move.

• How eye movements (left/right and up/down) and blinks create detectable electrical deflections.

Background

Background

Our brain not only controls our arms and legs—it also directs two powerful cameras that capture the visual world around us: our eyes. In this experiment, we will explore eye movements using electrooculography (EOG). The cornea is naturally more positive than the retina, making the eye an electric dipole. When you move your eyes, the orientation of this dipole changes, producing a measurable electrical deflection known as the electrooculographic signal. By positioning electrodes on either side of the eye—or above and below—it’s possible to detect left/right movements, vertical movements, and even blinks.

Procedure

  1. Electrode Preparation & Placement

    Electrode Placement for Lateral Movements:

    • Place your BYB headband so that two electrodes rest on either side of your eyes.
    • Apply a small amount of electrode gel under the metal patches to ensure a solid connection.
    • Stick a ground electrode (sticker) on the mastoid process—the bony bump behind your ear.

    Connections:

    • Clip the red alligator clips to the electrodes on either side of the eyes (exact sides don’t matter for a first trial).
    • Attach the black alligator clip to the ground electrode.
    • Plug the electrode cable (orange connector) into the SpikerBox.

    Setup & Noise Management:

    • Connect your SpikerBox to your recording device. To minimize interference, keep your laptop or tablet a short distance from power outlets and fluorescent lights, and run on battery power if possible.
    • Open SpikeRecorder. In Settings, enable the notch filter: choose your local power-line frequency: 60 Hz in the U.S., most of the Americas and a few other countries (e.g. South Korea, Taiwan, western Japan), 50 Hz in most of the rest of the world.

    Record Lateral Eye Movements:

    • Click Record in SpikeRecorder.
    • With a friend’s help or on your own, move your eyes to the left, then to the right. Observe the deflections in the EOG signal as you change direction.
    Electrode Preparation & Placement

  2. Recording Vertical Movements & Blinks:

    • Reposition the headband so that one electrode sits above your eye and another below it.
    • Secure the ground electrode behind your ear again.
    • Record as you move your eyes up and down and when you blink. Compare the waveforms—blinks often produce sharp spikes, mostly because your eyelid slides down over the positively charged cornea.

    Data Saving & Analysis:

    • Open your recordings in SpikeRecorder to measure features such as the amplitude and timing of deflections produced by different movements.
    • Analyze polarity shifts and see whether you can clearly distinguish eye movements from blinks.
Results & Analysis

Results & Analysis

Further Investigation Ideas

  1. Interface Applications: Could you create an interface—perhaps a video-game controller—that uses EOG signals? What challenges might you face when translating these analog signals into digital commands?
  2. Electrode Placement: How does shifting electrode positions (closer to or farther from the eye) affect the signal you record?
  3. Movement Parameters: Does the amplitude of the EOG change with the distance or speed of an eye movement?

Additional Factors: Do variables such as eyelid tension (squinting vs. eyes wide open) or wearing glasses influence the EOG signal? Why might that be?

Model it: draw the chain that makes your signal—your brain, the eye muscles, the eyeball turning, and the cornea–retina dipole turning with it—and label where your electrodes sat for each recording.

Design Challenge

  1. An Eye-Controlled Game Controller

    Could two glances become two buttons? Design an EOG controller that tells a look to the left from a look to the right, and doesn’t get fooled by a blink.

    1. Rank your criteria: correct commands out of 10 looks each way, comfort, and how quickly you can set it up.
    2. Test at least three electrode placements around the eyes. For each, make 10 looks left, 10 looks right and 10 blinks, and count how many you can tell apart in SpikeRecorder.
    3. Compare your designs in a table, combine the best features into one final setup, and test it again.
    4. Explain your trade-offs: is your most accurate design also comfortable enough to wear for a whole game?
    5. Judge your final controller for a real player, for example someone who cannot use their hands: what would it cost, is it safe and comfortable to wear for hours, and who could or could not use it?

NGSS alignment

Performance expectations

  • HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

    Draw the chain from brain to eye muscles to the turning eye: parts working together, and the eye's own voltage shows where you look.

  • MS-ETS1-2 Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

    Score at least three electrode placements against ranked criteria in one table (design challenge).

  • MS-ETS1-3 Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.

    Test at least three electrode placements, compare how well each tells looks from blinks, and combine the best features (design challenge).

  • HS-ETS1-3 Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics, as well as possible social, cultural, and environmental impacts.

    Rank accuracy, comfort and setup time, explain the trade-offs, and judge the controller for a real player (design challenge).

Science and engineering practices

  • 1 Asking Questions and Defining Problems

    Define the problem: two eye commands a controller can tell apart (design challenge).

  • 2 Developing and Using Models

    Use the eye-as-dipole model, and draw the chain from brain to eye muscles to electrodes, to explain the deflections.

  • 3 Planning and Carrying Out Investigations

    Record left-right movements, up-down movements and blinks.

  • 4 Analyzing and Interpreting Data

    Measure the size and timing of each deflection and tell eye movements from blinks.

  • 6 Constructing Explanations and Designing Solutions

    Design an eye controller from the test data and explain it (design challenge).

Crosscutting concepts

  • Structure and Function

    The cornea is more positive than the retina, making the eye an electric dipole.

  • Patterns

    Each movement and blink has its own waveform.

  • Influence of Science, Engineering, and Technology on Society and the Natural World Engineering connection

    Eye-movement signals can become a game controller or another interface.

Disciplinary core ideas

  • LS1.A Structure and Function

    The eye's structure creates a measurable electrical signal.

  • ETS1.B Developing Possible Solutions

    Test several placements and weigh accuracy against comfort.

  • ETS1.C Optimizing the Design Solution

    Use test results to pick and combine the best design.

Backyard Brains mapping using the book's method. Not in the book. Engineering claims rest on the design challenge on this page (Greg, 2026-10-06; real-user judgment step added 2026-10-08), modelled on the SpikerBot curriculum.