A method includes obtaining an image of an eye in a bright-pupil imaging mode in which a retinal retro-reflection complements the image of the eye in the bright-pupil mode, and obtaining an image of the eye in a dark-pupil imaging mode in which a cornea-scleral retro-reflection complements the image of the eye in the dark-pupil mode. One of the bright-pupil imaging mode and the dark-pupil imaging mode is selected based on quality of obtained images.