earEOG via Periauricular Electrodes to Facilitate Eye Tracking in a Natural Headphone Form Factor

Eye tracking technology is frequently utilized to diagnose eye and neurological disorders, assess sleep and fatigue, study human visual perception, and enable novel gaze-based interaction methods. However, traditional eye tracking methodologies are constrained by bespoke hardware that is often cumbersome to wear, complex to apply, and demands substantial computational resources. To overcome these limitations, we investigated Electrooculography (EOG) eye tracking using 14 electrodes positioned around the ears, integrated into a custom-built headphone form factor device. In a controlled experiment, 16 participants tracked stimuli designed to induce smooth pursuits and saccades. Data analysis identified optimal electrode pairs for vertical and horizontal eye movement tracking, benchmarked against gold-standard EOG and camera-based methods. The electrode montage nearest the eyes yielded the best horizontal results. Horizontal smooth pursuits via earEOG showed high correlation with gold-standard measures ($r_{\mathrm{EOG}} = 0.81, p = 0.01$; $r_{\mathrm{CAM}} = 0.56, p = 0.02$), while vertical pursuits were weakly correlated ($r_{\mathrm{EOG}} = 0.28, p = 0.04$; $r_{\mathrm{CAM}} = 0.35, p = 0.05$). Voltage deflections when performing saccades showed strong correlation in the horizontal direction ($r_{\mathrm{left}} = 0.99, p = 0.0$; $r_{\mathrm{right}} = 0.99, p = 0.0$) but low correlation in the vertical direction ($r_{\mathrm{up}} = 0.6, p = 0.23$; $r_{\mathrm{down}} = 0.19, p = 0.73$). Overall, horizontal earEOG demonstrated strong performance, indicating its potential effectiveness, while vertical earEOG results were poor, suggesting limited feasibility in our current setup.