Electrooculography (EOG) is a technique for measuring 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 Ophthalmology ( ) is a surgical subspecialty within medicine that deals with the diagnosis and treatment of eye disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Following a medic ...

diagnosis Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engin ...

and in recording

eye movements Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of inte ...

. Unlike the

electroretinogram Electroretinography measures the electrical responses of various cell types in the retina, including the photoreceptors ( rods and cones), inner retinal cells ( bipolar and amacrine cells), and the ganglion cells. Electrodes are placed on th ...

, the EOG does not measure response to individual visual stimuli. To measure eye movement, pairs of electrodes are typically placed either above and below the eye or to the left and right of the eye. If the eye moves from center position toward one of the two electrodes, 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 of the eye's position.

Principle

The eye acts as a

dipole In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways: *An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system i ...

in which the anterior pole is positive and the posterior pole is negative. # Left gaze: the

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...

approaches the electrode near the outer canthus of the left eye, resulting in a negative-trending change in the recorded potential difference. # Right gaze: the cornea approaches the electrode near the inner

canthus The canthus (pl. canthi, palpebral commissures) is either corner of the eye where the upper and lower eyelids meet. More specifically, the inner and outer canthi are, respectively, the medial and lateral ends/angles of the palpebral fissure. Th ...

of the left eye, resulting in a positive-trending change in the recorded potential difference.

Ophthalmological diagnosis

The EOG is used to assess the function of the

pigment epithelium The pigmented layer of retina or retinal pigment epithelium (RPE) is the pigmented cell layer just outside the neurosensory retina that nourishes retinal visual cells, and is firmly attached to the underlying choroid and overlying retinal visual ce ...

. During

dark adaptation Darkness, the direct opposite of lightness, is defined as a lack of illumination, an absence of visible light, or a surface that absorbs light, such as black or brown. Human vision is unable to distinguish colors in conditions of very low l ...

, resting potential decreases slightly and reaches a minimum ("dark trough") after several minutes. When 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 eye movement recordings (see above). The patient is asked to switch eye position repeatedly between two points (alternating looking from center to the left and from center to the right). Since these positions are constant, a change in the recorded potential originates from a change in the resting potential.

References

* 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. {{Electrodiagnosis Diagnostic ophthalmology Electrodiagnosis Electrophysiology Neurophysiology Neurotechnology

Principle

Ophthalmological diagnosis

See also

References