Fig. 7 (Top) A tissue lens can be shaped by placing the anterior surface of the cornea on a plastic base and removing tissue from the posterior surface (hatched area). More tissue is removed centrally to create a lens for myopia. (Center) Additional tissue is removed from the periphery to create a wing. (Bottom) When placed on the patient's cornea, the posterior surface of the tissue lens conforms to the anterior surface of the patient's cornea, and the anterior surface of the tissue lens assumes a different shape. In this method of shaping a tissue lens, the plastic base remains constant, and the lathing parameters for the posterior surface are varied.