Electrooculography

Electrooculography, often abbreviated as EOG, is a technique used to measure the resting electrical potential that exists between the front and back of the human eye. This potential, known as the standing potential, changes with eye movements. By placing electrodes on the skin around the eye, typically near the medial and lateral canthi, EOG can detect these changes and record the corresponding eye movements.

The basic principle behind EOG relies on the fact that the cornea, the outer transparent layer of the eye, is positively charged relative to the retina, the light-sensitive tissue at the back of the eye. When the eye moves, this dipole rotates, altering the electrical field detected by the electrodes. A larger movement of the eye, such as looking from the center to the side, results in a more significant change in the recorded potential.

EOG has various clinical applications, particularly in ophthalmology. It is used to assess the function of the retinal pigment epithelium (RPE), a critical layer of the retina. Certain diseases affecting the RPE, like Best's disease and other inherited retinal dystrophies, can cause abnormal EOG readings, even before visual symptoms become apparent. This makes EOG a valuable diagnostic tool for early detection and monitoring of these conditions. It can also be used in research settings to study eye movements during visual tasks or in sleep studies.