Electrooculography is a method for measuring the resting potential of the retina. The resulting signal is called the electrooculogram. It is used to assess the function of the pigment epithelium. During dark adaptation, the resting potential decreases slightly and reaches a minimum after several minutes. When the light is switched on, a substantial increase of the resting potential occurs, which drops off after a few minutes when the retina adapts to the light. The patient is asked to switch the eye position repeatedly between two points (usually to the left and right of the center). Since these positions are constant, a change in the recorded potential originates from a change in the resting potential.