A laser eye surgery system produces a treatment beam that includes a plurality of laser pulses. An optical coherence tomography (OCT) subsystem produces a source beam used to locate one or more structures of an eye. The OCT subsystem is used to sense the distance between a camera objective on the underside of the laser eye surgery system and the patient's eye. Control electronics compare the sensed distance with a pre-determined target distance, and reposition a movable patient support toward or away the camera objective until the sensed distance is at the pre-determined target distance. A subsequent measurement dependent upon the spacing between the camera objective and the patient's eye is performed, such as determining the astigmatic axis by observing the reflection of a plurality of point source LEDs arranged in concentric rings off the eye.