A method to process an image acquired through an optical-fiber guide includes acquiring a first reference image through the optical-fiber guide, acquiring a second calibration image through the optical-fiber guide, spatially identifying each fiber of the optical-fiber guide of the second calibration image in a first detection map, acquiring a recalibration image through the optical-fiber guide, determining a geometrical transformation to make the recalibration image coincide with the first reference image, deriving a new detection map spatially identifying each fiber of the optical-fiber guide of the recalibration image, wherein the new detection map is derived using the geometrical transformation and the first detection map, and individually processing zones of an acquired image corresponding to each fiber of the optical-fiber guide using the new detection map.