An apparatus including a wavefront sensor including a light source (172) configured to illuminate a subject eye, a detector (122), an image sensor (162) configured to output an image of the subject eye, a first beam deflecting element (112) configured to intercept a wavefront beam returned from a subject eye when the subject eye is illuminated by the light source (172) and configured to direct a portion of the wavefront from the subject eye through an aperture (118) toward the detector (122), and a controller coupled to the light source (172), the image sensor (162) and the beam deflecting element (112), configured to process the image to determine transverse movement of the subject eye and to control the beam deflecting element (112) to deflect and project through the aperture (118) portions of an annular ring portion of the wavefront and further configured to pulse the light source (172) at a firing rate to sample selected portions of the annular ring at the detector (122), to process the image of the subject eye to calculate transverse movement of the subject eye and to orient the beam deflecting element (112) at a DC offset angle to compensate transverse movement of the subject eye.
