Four different lens designs. A material was examined in this study. These comprised of a mid-peripheral lens profile designed to provide a greater lens-induced pressure on the ocular surface (8.4-mm base curve and thicker, stiffer mid-peripheral; high pressure) compared with a flatter (8.8 mm) base curve, thinner mid-peripheral shape profile (low pressure), in combination with a chisel or knife lens edge designs.<br />Small Diameter 1.56 Super Thin Knife Edge Lens 55mm, 60mm Optical Lenses HMC Coating – (55mm 60mm Optical Lenses,1.56 Super Thin knife ). <br />20 degrees angle in fact, a 20 0 is often considered the best sharing point for most knife.