A Real-Time Eye Tracking Method for Detecting Optokinetic Nystagmus

Optokinetic nystagmus (OKN) is an involuntary repeated “beating” of the eye, comprised of sequences of slow tracking (slow phase) and subsequent quick re-fixation events (quick phase) that occur in response to (typically horizontally) drifting stimuli. OKN has a characteristic saw-tooth pattern that we detect here using a state-machine approach applied to the eye-tracking signal. Our algorithm transitions through the slow/quick phases of nystagmus (and a final state) in order to register the start, peak and end points of individual sawtooth events. The method generates duration, amplitude, velocity estimates for candidate events, as well as repetition estimates from the signal.