A gaze-tracking system for a head-mounted display apparatus includes a first set of illuminators for emitting light to illuminate a user's eye; at least one photo sensor for sensing reflections of the light from the user's eye; at least one actuator for moving at least one of: (i) the first set of illuminators, (ii) the at least one photo sensor; and a processor coupled with the first set of illuminators, the at least one photo sensor and the at least one actuator. The processor is configured to collect and process sensor data from the at least one photo sensor to detect a gaze direction of the user, and to control the at least one actuator to adjust, based upon the detected gaze direction, a position of the at least one of: (i) the first set of illuminators, (ii) the at least one photo sensor.