A method for fabrication of a lens element from a lens blank shaped from a high index, high thermal property thermoplastic resin conditions the surface of the lens blank by an extended annealing process. The temperature of the lens blank is increased to a soak temperature greater than 165 degrees C. over a ramp-up period of more than 2.5 hours, increasing the temperature during the ramp-up period by no more than 2 degrees C. per minute, on average. The lens blank is maintained at the soak temperature for a soak period of at least 3 hours. The temperature of the lens blank is lowered back to room temperature during a ramp-down period at a rate no faster than 1.5 degrees C. per minute, on average. This forms a conditioned lens blank that is diamond-turned to obtain an optical quality surface.