The invention relates to a device for cutting a tissue part of an eye by means of laser radiation, comprising a suction ring unit (16), which can be placed on the eye and which has a ring axis (22), a mechanical interface unit (34), which is separate from the suction ring unit (16) and which can be moved along the ring axis (22) in coupling contact with said suction ring unit and which can be mechanically coupled to optical means (70), which focus the laser radiation onto or into the tissue part (12) of the eye, and sealing means (44, 52), which, when the interface unit (34) moves into coupling contact with the suction ring unit (16), form a space (58) that can be evacuated, which space is separated from sealing surfaces (46, 60) of the interface unit (34) and from the suction ring unit (16) and the sealing means (44, 52).
