Gaze tracking accuracy in humans: two eyes are better than one.

Many people viewing a small distant object report the use of a dominant eye, which may change when viewing the same object in right or left viewing fields. This study was designed to determine if the accuracy in left and right gaze recordings from a video-based binocular eye tracking system with eye-head integration would change when observers looked at targets in different viewing fields. We also wanted to determine whether system accuracy was best using the dominant eye, the average of both eyes or an alignment switching strategy for various viewing fields. Bilateral eye and head movements were recorded to determine point of gaze (POG) for subjects viewing targets with the head neutral or rotated left or right with a stationary body (static) or while stepping toward a target and back (dynamic). Constant, absolute and variable POG and rotational errors were determined. Results showed that although errors were highest in the static condition for POG errors and in the dynamic condition for rotational errors, absolute rotational angle errors were similar for static and dynamic conditions, indicating that subject to object distance played an important role in determining POG errors. Furthermore, errors were not consistently lower for a given eye or for a given eye within a specific viewing field for the head rotations performed. Since low errors across the viewing fields were found by averaging left and right errors, it was concluded that this average and should be used in future studies involving relatively small eye-in-head rotations.