  We present software to detect noise in eye position signals from video-based
eye-tracking systems that depend on accurate pupil and corneal reflection
position estimation. When such systems transiently fail to properly detect the
pupil or the corneal reflection due to occlusion from eyelids, eye lashes or
various shadows, the estimated gaze position is false. This produces an
artifactual signal in the position trace that is rapidly, irregularly
oscillating between true and false gaze positions. We refer to this noise as
RIONEPS (Rapid Irregularly Oscillating Noise of the Eye Position Signal). Our
method for detecting these periods automatically is based on an estimate of the
relative inefficiency of the eye position signal. We look for RIONEPS in the
horizontal and vertical traces separately, and although we typically use it
offline, it is suitable to adaptation for real time use. This method requires a
threshold to be set, and although we provide some guidance, thresholds will
have to be estimated empirically.
