Eye-gaze estimation accuracy and key in human vision

Eye movement and eye-gaze direction have significant roles in human communications. Eye-gaze direction often indicates what a person is thinking about or trying to do. Empirically, it is possible to recognize which eye (right or left) is being fixated by a person who is standing in front of us at 1 m distance; this indicates that our eye-gaze estimation accuracy is less than 3.7 deg. This paper describes our specific examination of eye-gaze direction estimation accuracy and method in the human vision system. Extensive measurements show that the eye-gaze estimation accuracy is 2-4 deg from 1 m distance. However, they also indicate that individual eye-gaze estimation errors differ in magnitude and tendency. A person who has good eyesight estimates well, in general. Furthermore, measurements reveal that human vision might use an eyeball model-based method that employs the center of the iris or pupil, rather than an iris shape-based method with an elliptical iris shape.