Refractive devices such as lenses and prisms deflect radiation by presenting the wavefront with a spatially varying path length. This letter describes a novel device in which the optical path length is varied by a change in refractive index, rather than thickness. The active element is a liquid-crystalline material which, because of its fluid nature and large birefringence, is capable of large changes in refractive index. Consequently, it is possible to achieve electro-optical effects much greater than those of analogous solid-state devices.