Eye tracking is a technique which attempts to determine where a person is looking.
Equipment which is used to do this automatically and quite accurately are called eye trackers. A video camera collects images of the eye. From these images, a computer calculates the center of the pupil and the specular highlight of the LED which is referred to as the corneal reflection. Because the lens of the eye protrudes out in front of the sphere of the eyeball, the pupil and reflection move relative to each other as the eye shifts gaze. The computer uses the vector between the pupil center and corneal reflection to calculate the direction of the gaze.