The electrooculogram (EOG) reflects the standing potential produced by transepithelial potential (TEP) of the retinal pigment epithelium (RPE) at the back of the eye. To record the potential, skin electrodes are attached near the inner and outer canthus of each eye. The standing potential is measured by having the patient move their eyes left and right between alternating LEDs 30° apart. The standing voltage becomes smaller during dark adaption, reaching its lowest potential, the “dark trough”, in about 10 minutes, followed by light adaptation that causes the potential to rise to a peak in about 10 minutes. When the ratio of the amplitude of the “light peak” to that of the “dark trough” (i.e., light peak:dark trough ratio (LP:DT ratio)) is less than 1.7, the EOG is considered as abnormal. The normal value of LP:DT ratio is near 2 or greater. The EOG placement of electrodes is also used for tracking eye movement.
Electrooculogram Fast oscillation Retinal pigment epithelium LP:DT ratio Light peak Dark peak Light trough Dark trough Arden ratio
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