A switchable optical element has an optical axis. The element includes a chamber, a wave front modifier having a face defining an interior surface of the chamber (the face extending transverse the optical axis), a first fluid and a second fluid. The fluids are immiscible and in contact over an interface. The optical element is switchable between a first discrete state in which the first fluid substantially covers the face of the wave front modifier, and a second discrete state in which the second fluid substantially covers the face of the wave front modifier, wherein the chamber encloses both fluids in both discrete states, and the interlace extends transverse the optical axis in the first discrete state.