Eye tracking as a computer input and interaction method

Eye tracking applications can be considered under two points of view: in the former the eye tracker is a passive sensor that monitors the eyes to determine what the user is watching. In the latter the eye tracker has an active role that allows the user to control a computer. As a computer input device, an eye tracker typically substitutes the mouse point-select operation with a look-select process to: press buttons, select icons, follow links, etc. While look-select operations are naturally suited to eye input, controlling an interface element is not, because the eyes move covertly by saccades -- quick movements of the point of gaze from one location to another. Since the main task of the eyes is simply to see, if they are also used for interacting with the computer it may be difficult to decide, for example, whether a button is watched to understand its function or to trigger the associated action. In general, eye tracking systems present significant challenges when used for computer input and much research has been carried out in this field.