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Tracking the closed eye by calibrating electrooculography with pupil-corneal reflection MacNeil, Raymond R.


Electrooculography (EOG) offers several advantages over other methods for tracking human eye movements, including its low cost and capability of monitoring gaze position when the eyelids are closed. Yet, EOG poses its own challenges, because in order to determine saccadic distance and direction, the electrical potentials measured by EOG must be calibrated in some way with physical distance. Moreover, the EOG signal is highly susceptible to noise and artifacts arising from a variety of sources (e.g., activity of the extraocular muscles). Here we describe a method for estimating a corrected EOG signal by simultaneously tracking gaze position with an industry standard pupil-corneal reflection (PCR) system. We first compared the two measurements with the eyes open under two conditions of full illumination and in a third condition of complete darkness. Compared to the PCR signal, the EOG signal was less precise and tended to overestimate saccadic amplitude. We harnessed the relation between the two signals in the dark condition in order to estimate a corrected EOG-based metric of saccade end-point amplitude in a fourth condition, where the participants eyes were closed. We propose that these methods and results can be applied to human-machine interfaces that rely on EOG eye tracking, and for advancing research in sleep, visual imagery, and other situations in which participants’ eyes are moving but closed.

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