A method and apparatus for obtaining geometrical data relating to the internal surface of the ear canal and/or ear whereby a probe having a light emitting distal portion is inserted into the ear canal, the method including the steps of: directing light from a distal portion of a probe to illuminate at least one point of the internal circumferential surface of the ear and/or ear canal, receiving the light reflected from the illuminated surface, and directing the received light to at least one light sensitive element to generate an output, and analyzing the output to determine the distance from the probe to the internal surface of the ear and/or ear canal at points of the circumference.