An edge lit fixture. A housing provides the basic shape and structure of the fixture. The housing is constructed from discrete segments including lens frames, side frames, and end frames, which can be used in many different combinations to create the desired fixture. The assembled housing defines an open central area. One or more light panels are arranged around the perimeter of the housing such that at least some of the light is emitted toward the central area. The open central area of the housing allows for existing materials, such as a ceiling tile, for example, to function as a back surface of the fixture.