The present invention relates to control of a computer system, which includes a data processing unit, a display and an eye tracker adapted to register a user's gaze point with respect to the display. The data processing unit is adapted to present graphical information on the display, which includes feedback data reflecting the user's commands entered into the unit. The data processing unit is adapted to present the feedback data such that during an initial phase, the feedback data is generated based on an absolute position of the gaze point. An imaging device of the system is also adapted to register image data representing movements of a body part of the user, and to forward a representation of the image data to the data processing unit. Hence, during a phase subsequent to the initial phase, the data is instead generated based on the image data.