An accommodating intraocular lens is provided having optical parameters that are altered in-situ, wherein an optic portion of the lens includes a lens piston that alters the shape of a lens element of the lens to alter the optical power of the lens, responsive to forces applied to a haptic portion to the lens by contraction of the ciliary muscles. Forces applied to the haptic portion are concentrated by the lens piston to provide a greater dynamic range, and may be further augmented by the use of haptic pistons disposed in the haptic portion of the lens.