For example, in air traffic control, getting information about an airplane would be a lightweight application, but issuing instructions to an airplane with an eye-tracking interface would be dangerous. The philosophy Rob has adopted is one where natural, not trained, movements are used. Eye tracking is used for additional input in places where this input could improve the interaction. Because eyes don't sit still, the data from eye trackers is quite noisy. In the optical video method, the camera shows pictures of the eye.
Corneal reflection is used as a second feature.
The eye tracker camera provides X and Y positions sixty times per second. When questioned about using a camera on the head, Rob pointed out that current work in virtual reality also uses a head-mounted camera, and that people don't find the hardware to be all that terrible. Rob went on to describe types of eye movement in human-computer dialogue. He explained that the eye moves rapidly and ballistically. In fact, the brain ignores a steady image.