Electrooculography or EOG electrodes are placed on the head near the eye. Usually it is done with two electrodes, one positively charged, the other negatively. This allows current from one electrode to the other to be measured and because they are placed around the eye, this allows for monitoring eye movements.
Applications for EOG have traditionally focussed around the diagnosis of certain eye diseases. In recent years research in the field of EOG has found a great variety of applications.
There have been attempts to make human-machine interfaces through EOG sensors incorporated into glasses. These are then used to control video games or other software applications as well as improving VR technology immersion and responsiveness.
There has also been research towards the use of EOG as a secure way of making eye-movement passwords for various smart devices. Because EOG allows the tracking of eye movements while the eyes are closed, it can be hard for hackers to mimic the exact eye movements by observing them via a camera.