High Density Facial Mapping for Alternative EOG Electrode Placement for the Disabled

Abstract

A small potential difference of between 1 and several mV exists between the cornea (+) and the retina (-) of the eye which is dependent on the ambient light level. This phenomenon, known as the resting potential or cornealretinal potential (CRP), has been known for over 150 years, [1] and has led to the eye being modeled as an electrical dipole. The measurement of this signal, electrooculography (EOG), is used not only for diagnostic studies in clinical settings, but also for use in assistive technology (AT) as a control input for external devices for the disabled.

A large percentage of end users of EOG in AT are patients who have developed amyotrophic lateral sclerosis (ALS) and that use bi-level positive airway pressure (BiPAP) devices for breathing assistance. These devices cover a large portion of the face, especially the areas most commonly used for EOG signal acquisition (area surrounding the eyes).

This paper serves to present alternative locations for EOG acquisition through the use of electrode facial mapping. A high-density electrode array system is used to gather information on the signal integrity on the face and surrounding area and is weighed against the apparent benefits with respect to BiPAP mask obstruction and general aesthetics. These results are used as a stepping stone towards the development of a new low powered, portable EOG device that will be applicable to any user, despite possible facial obstructions or aesthetic concerns.