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); anda 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.