Electrooculography (EOG) is the technique used to measure the corneo-retinal standing potential between the front and back of the eyeball. During the 1800s it was observed that the cornea (the front layer of the eye) is electrically positive in comparison to the back of the eye. The presence of light did not affect this front-back relationship which signified it was a resting potential- it became known as the corneo-retinal standing potential. This potential varies in movement slightly and these movements can be recorded by an electrooculograh. The resulting electrooculargram can be used to diagnose eye diseases or disorders.