A wavefront sensor includes a light source configured to illuminate a subject eye, a detector, a first beam deflecting element configured to intercept a wavefront beam returned from a subject eye when the subject eye is illuminated by the light source and configured to direct a portion of the wavefront from the subject eye through an aperture toward the detector and a controller, coupled to the light source and the beam deflecting element, configured to control the beam deflecting element to deflect and project different portions of an annular ring portion of the wavefront from the subject eye through the aperture and further configured to pulse the light source at a firing rate to sample selected portions of the annular ring at the detector.