An intraocular lens is described which comprises, as one face (21, 145) thereof, a linear Fresnel prism array with facets angled relative to the optical axis of the lens so as to deviate light incident thereon to an off-axis position. The facets are modified so as to reduce at least one of diffraction effects and astigmatism associated with the Fresnel prism. In particular, by varying the pitch (xl,..., xn) of the prism elements across the array, which may comprise varying their size, a diffraction grating effect can be reduced or negated, such that light is not diffracted into undesirable orders and multiple images can be avoided. Furthermore, chromatic angular dispersion associated with the diffraction grating effect may be reduced. The pitch variation can be random. By varying the angle of the facets across the array, astigmatism that would otherwise result from the presence of the Fresnel prism can also be compensated.
