This tool includes: a rigid support ( 104 ) having a transverse end surface ( 113 ); an elastically compressible interface that is pressed against and covers the end surface; a flexible pad adapted to be pressed against the optical surface, itself pressed against and covering the interface on the opposite side of and in line with the end surface ( 113 ); spring return element ( 115 ) connecting the support ( 104 ) to a peripheral portion of the flexible pad situated transversely beyond the end surface ( 113 ); and a flexible flange ( 131 ) that is part of a base ( 130 ) to which the rigid support ( 104 ), which is surrounded by the flange ( 131 ), also belongs.