Techniques for reducing a read out time and power consumption of an image sensor used for eye tracking are described. In an example, a position of an eye element in an active area of a sensor is determined. The eye element can be any of an eye, a pupil of the eye, an iris of the eye, or a glint at the eye. A region of interest (ROI) around the position of the eye is defined. The image sensor reads out pixels confined to the ROI, thereby generating an ROI image that shows the eye element.