An optical system including at least a first lens, a partial reflector and a reflective polarizer is described. The optical system has an optical axis such that a light ray propagating along the optical axis passes through the first lens the partial reflector and the reflective polarizer without being substantially refracted. At least one major surface of the optical system is rotationally asymmetric about the optical axis. A major surface of the optical system may have a first portion defined by a first equation and a second portion adjacent the first portion defined by a different equation. The first lens may have a contoured edge adapted to be placed adjacent an eye of a viewer and substantially conform to the viewer's face.