Method for contact lens design and manufacturing

Method for designing and manufacturing contact lens with aspherical geometry, said lens having a front surface, an edge and a back surface suitable for matching an eye's cornea surface by interposition of a tear film layer, comprising the steps of:

• conducting digital topography of said cornea surface and creating a numerical definition of said cornea surface;
• choosing a surface portion approximating said cornea surface as defined by said numerical definition of said cornea;
• determining a numerical definition of a tear film layer covering said cornea surface;
• choosing a lens back surface approximating the summation of said surface portion and said tear film layer as defined by said numerical definitions;
• designing the front surface shape and edge shape;
• and
• cutting the lens by a CNC machine tool, wherein said lens back surface and its position are calculated by a non-linear optimization which minimizes a functional V related to congruence between said corneal topography and said approximating surface, said congruence being defined by the following integral:
• V=.intg..intg.([(P-Q)*i0-h(r,f)].sup.2)*.beta.(r,f)dS
• wherein P is a vector position of a corneal topography point and h(r,f) is the axial coordinate of the surface S, Q is a vector of said origin, [(P-Q)*i0-h(r,f)].sup.2 is the distance between said lens surface and said topography;
• .beta.(r,f) is a weight function on the approximation error.