The present invention relates to an optical device (1), comprising a lens (10) having an adjustable focal length, the lens (10) comprising a container (11) that encloses a lens volume (V) and a reservoir volume (R) that is connected to the lens volume (V), wherein the two volumes (R, V) are filled with a transparent liquid (L), wherein the container (11) further comprises a flat lateral wall structure (12) having a front side (12a) and a back side (12b), an elastically deformable and transparent membrane (20), a transparent cover element (30), and an an elastically deformable wall portion (22), wherein the membrane (20) is connected to the back side (12b) of the lateral wall structure (12), wherein the cover element (30) is connected to the front side (12a) of the lateral wall structure (12) such that the lens volume (V) is arranged between the cover element (30) and the membrane (20), and wherein the wall portion (22) is arranged adjacent the reservoir volume (R), and wherein the wall portion (R) comprises an inside (22a) and an outside (22b) facing away from said inside (22a), wherein the inside (22a) contacts the liquid (L) residing in the reservoir volume (R), and wherein the lens (10) further comprises a lens shaper (40) that is connected to the membrane (20) and defines an area (21) of the membrane (20), which area (21) has an adjustable curvature and contacts the liquid (L) in the lens volume (V), and wherein the lens (10) further comprises a movable piston (50) connected to the outside (22b) of the wall portion (22) and configured to act on said outside (22b) to pump liquid (L) from the reservoir volume (R) into the lens volume (V) or from the lens volume (V) into the reservoir volume (R) so as to change the curvature of said area (21) of the membrane (20) and therewith the focal length of the lens (10).