A device for variably influencing the wavefront of a beam, said device comprising a reflecting or transmitting planar optical element (1) and an actuating and holding means (2) which is connected to the planar optical element (1) via at least three elastic retaining lugs (2.3) such that forces can be introduced into at least one of the retaining lugs (2.3) via at least one actuating element (2.4) arranged in the actuating and holding means (2), which forces are deflected in their direction of action by the bending of the retaining lugs (2.3) such that they cause forces on the peripheral surface (1.3) of the planar optical element (1) whose direction of action (RA) is parallel to the axis of symmetry (A) of the planar optical element (1), allowing the planar optical element (1) to be actively deformed.