Electrooculography

Electrooculography (EOG) is a technique used to measure the corneo-retinal standing potential that exists between the front and the back of the human eye. The resulting signal is called the electrooculogram. Primary applications are in ophthalmological diagnosis and in recording eye movements. Unlike the electroretinography (ERG), the EOG does not measure response to individual visual stimuli.

Principle

The eye acts as a dipole in which the anterior pole is positive and the posterior pole is negative. EOG measures the potential difference between the front and the back of the human eye. It is usually recorded using electrodes placed on the skin around the eye, which detect changes in the electrical potential as the eye moves. This change in potential provides a measure of eye movement.

Procedure

The patient is asked to sit with their head steady, and to move their eyes in a specific pattern. This can include looking straight ahead, looking to the left or right, or following a light as it moves across the patient's field of vision. The electrodes detect the movement of the eye, and this information is recorded and can be analyzed to help diagnose a range of conditions.

Applications

EOG is used in the investigation and diagnosis of some diseases such as Parkinson's disease, brain stem death and multiple sclerosis. It is also used in research into sleep disorders, where it is used to measure rapid eye movement (REM) during sleep. In addition, it can be used to detect eye movement in situations where it may not be observable otherwise, such as in the study of reading.

Limitations

EOG is not very accurate for tracking eye position, which is better achieved with infrared eye trackers. The EOG is most useful for measuring saccadic eye movement, and is not very reliable for slow eye movement or where the eye is stationary.

See also

• Electroencephalography
• Electromyography
• Electroretinography