Electrooculography (EOG/E.O.G.) is a technique for measuring the resting potential of the retina. The resulting signal is called the electrooculogram. The main applications are in ophthalmological diagnosis and in recording eye movements. Unlike the electroretinogram, the EOG does not represent the response to individual visual stimuli.
Eye movement measurements: Usually, pairs of electrodes are placed either above and below the eye or to the left and right of the eye. If the eye is moved from the center position towards one electrode, this electrode "sees" the positive side of the retina and the opposite electrode "sees" the negative side of the retina. Consequently, a potential difference occurs between the electrodes. Assuming that the resting potential is constant, the recorded potential is a measure for the eye position.
The eye acts as a dipole in which the anterior pole is positive and the posterior pole is negative. 1. Left gaze: the cornea approaches the electrode near the outer canthus of the left eye, resulting in a positive-going change in the potential difference recorded from it. 2. Right gaze: the cornea approaches the electrode near the inner canthus of the left eye, resulting in a positive-going change in the potential difference recorded from it (A, an AC/DC amplifier).
Ophthalmological diagnosis 
The EOG is used to assess the function of the pigment epithelium. During dark adaptation, the resting potential decreases slightly and reaches a minimum ("dark trough") after several minutes. When the light is switched on, a substantial increase of the resting potential occurs ("light peak"), which drops off after a few minutes when the retina adapts to the light. The ratio of the voltages (i.e. light peak divided by dark trough) is known as the Arden ratio. In practice, the measurement is similar to the eye movement recordings (see above). The patient is asked to switch the eye position repeatedly between two points (usually to the left and right of the center). Since these positions are constant, a change in the recorded potential originates from a change in the resting potential.
Application in Entertainment 
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Electrooculography was used by Robert Zemeckis and Jerome Chen, the visual effects supervisor in the movie Beowulf, to enhance the performance capture by correctly animating the eye movements of the actors. The result was an improvement over the technique used for the film The Polar Express.
Electrooculography, in addition to other neuromuscular signals, is used as a computer input method by the Neural Impulse Actuator.
Brown, M., Marmor, M. and Vaegan, ISCEV Standard for Clinical Electro-oculography (EOG) (2006), in: Documenta Ophthalmologica, 113:3(205—212)
Bulling, A. et al.: It's in Your Eyes - Towards Context-Awareness and Mobile HCI Using Wearable EOG Goggles, Proc. of the 10th International Conference on Ubiquitous Computing (UbiComp 2008), pages 84–93, ACM Press, 2008
Bulling, A. et al.: Robust Recognition of Reading Activity in Transit Using Wearable Electrooculography, Proc. of the 6th International Conference on Pervasive Computing (Pervasive 2008), pages 19–37, Springer, 2008
Bulling, A. et al.: Wearable EOG goggles: Seamless sensing and context-awareness in everyday environments, Journal of Ambient Intelligence and Smart Environments, 1(2):157-171, 2009
Bulling, A. et al.: Eye Movement Analysis for Activity Recognition Using Electrooculography, IEEE Transactions on Pattern Analysis and Machine Intelligence, in press
Bulling, A. et al.: Eye Movement Analysis for Activity Recognition, International Conference on Ubiquitous Computing (UbiComp 2009), pages 41-50, ACM Press, 2009.
See also 
- International Society for Clinical Electrophysiology of Vision
- Optokinetic drum