Abstract: A shaft (1) having a fiber swab (5) on one end, a metric scale (2) on the shaft starting at the swab end, and preferably a flat portion (7) of the shaft for orienting the scale by touch, without visual inspection. A second scale (3) is preferably provided, starting at the opposite end from the first scale, and on the opposite side of the shaft. The shaft optionally includes a bulb (6) on one or both ends. An arrangement of tactile indicators (7 and 8) allows a practitioner to orient the probe for used of the desired end and its associated scale by touch alone, allowing visual concentration on the patient.