An optical film includes a microstructured surface having a plurality of irregularly arranged planar portions forming greater than about 10% of the microstructured surface. The microstructured surface may be configured such that, when the microstructured surface is placed on an emission surface of a lightguide with a first luminous distribution of light exiting the lightguide from the emission surface in a first plane perpendicular to the emission surface, the light emitted by the lightguide is transmitted by the microstructured surface at a second luminous distribution of the transmitted light in the first plane. The first luminous distribution includes a first peak making a first angle greater than about 60 degrees with a normal to the microstructured surface. The second luminous distribution includes a second peak making a second angle in a range from about 5 degrees to about 35 degrees with the normal to the microstructured surface.