A gaze-tracking system for use in a head-mounted display apparatus, and a method of tracking a user's gaze, via such a gaze-tracking system. The gaze-tracking system includes a plurality of illuminators for emitting light pulses to illuminate a user's eye when the head-mounted display apparatus is worn by the user, the illuminators including at least a first illuminator and a second illuminator; at least one lens positioned on an optical path of reflections of the light pulses from the user's eye, the at least one lens having no chromatic-aberration correction; at least one camera for capturing an image of the reflections of the light pulses; and a processor coupled with illuminators and the at least one camera, the processor being configured to control operations of the illuminators and the at least one camera, and to process the captured image to detect a gaze direction of the user.