A method of extracting eye velocity information from a video footage having a plurality of frames is disclosed. The method comprising providing a visual stimulus effective to elicit optokinetic nystagmus in front of the eye(s) of a subject, and detecting at least part of an eye in at least two frames of the video footage, applying an optical flow algorithm to the at least two frames of the video footage to extract pixel velocity information, and determining a statistical measure from the pixel velocity information within the detected at least part of the eye. A system and a device of extracting eye velocity information by this method are also disclosed. The invention also includes method, system and device for measuring head movement to compensate with the eye movement.
