Certain aspects of the present disclosure relate to a system. In some aspects, the system may include an emitter configured to emit a light. The system may include a light guide configured to direct the light toward a pupil of an eye. The light guide may include a directing portion configured to propagate the light. The light guide may include a turning portion configured to receive light from the directing portion and direct the light toward the pupil of the eye and configured to receive reflected light directed from the pupil of the eye and direct the reflected light toward the directing portion. The system may include a receiver configured to receive the reflected light from the light guide. The system may include a processor configured to determine a gaze direction of the pupil of the eye based at least in part on the reflected light received by the receiver.