A personal computer system comprises a visual display, an imaging device adapted to provide eye-tracking data by imaging at least one eye of a viewer of the visual display, and identifying means for recognizing the viewer with reference to one of a plurality of predefined personal profiles. The personal computer system further comprises an eye-tracking processor for processing the eye-tracking data. According to the invention, the eye-tracking processor is selectively operable in one of a plurality of personalized active sub-modes associated with said personal profiles. The sub-modes may differ with regard to eye-tracking related or power-management related settings. Further, the identifying means may sense an identified viewer's actual viewing condition (e.g., use of viewing aids or wearing of garments), wherein the imaging device is further operable in a sub-profile mode associated with the determined actual viewing condition.