The present invention concerns surgical devices for producing an opening (1) in a wall (2) located in a soft opaque medium (3) and locating same with the aim of carrying out a given operation, at least at said opening. The device according to the invention is essentially characterised by the fact that it comprises a cylindrical drill rod (010) defined along a longitudinal axis and having a cross-section of a given value, a thin cylindrical pin (12), a longitudinal groove (20) provided in the drill rod (10) substantially parallel to the longitudinal axis and opening on the side surface (24) of the drill rod (10) via a longitudinal opening (200), the longitudinal groove (20) being produced in such a way that the depth of same and width of the longitudinal opening are determined such that, when the pin slides along said groove, said pin only rests on the two edges (200-1), (200-2) of the opening (200).
