An adaptive lens system comprises i) a lens compartment with a transparent cover; ii) a deformable transparent optical element mounted in the lens compartment which forms a sealed upper chamber in the lens compartment between the transparent cover and the upper surface of the optical element, and also defining a lower region external to the lower surface of the optical element; iii) a first transparent fluid medium in the upper chamber and a second transparent fluid medium in the lower region, the first and second fluid media having different refractive indices; iv) a structural element located in and movable in the upper chamber relative to the deformable optical element to mechanically engage the deformable optical element to thereby alter the curvature of the deformable optical element, thereby altering the refractive power or the prismatic effect of the adaptive lens system.