Schematic drawing of the elongated laser plasma of a Gaussian beam in side view, roughly indicating the direction of mechanical forces leading to cavity formation within the corneal lamellae (A). To improve cutting precision, it would be ideal to have a disk-like plasma orientated parallel to the corneal surface along the cutting direction and the cleavage lines given by corneal lamellae (B). This feature can be approximated by introducing a spiral phase mask with 2π phase shift (C) into the beam path that converts the linear polarized Gaussian beam exiting the laser into a vortex beam with helical phase (D). The foci of the Gaussian and vortex beam are presented in (E), with the vortex beam focus shown in the top view. It has a ring shape, with the same length in the axial direction as the focus of the Gaussian beam, but with a diameter two times larger. 22