Patent ID: 6883915

Claim:
A contact lens comprising a convex surface and a concave surface, one or both of the surfaces comprising: (a) an apex; (b) an axis passing through the apex; (c) a central optical zone that is an aspherical sub-surface described by an aspherical function form y opz (x); (d) a transition zone that is adjacent to and surrounds said central optical zone, wherein said transition zone is a rotationally symmetric off-center sphere sub-surface characterized by having a curvature radius r a the center C(x c ,y c ) of which is not located in the axis, wherein said curvature radius (r a ) is defined by a functional form (2) r a = { 1 + [ y opz ′ ⁡ ( x a ) ] 2 } 3 / 2 y opz ′′ ⁡ ( x a ) , ( 2 ) wherein the center C(x c ,y c ) of the curvature radius r a is given by formula (3) and (4) x c = x a - y opz ′ ⁡ ( x a ) · { 1 + [ y opz ′ ⁡ ( x a ) ] 2 } y opz ′′ ⁡ ( x a ) ( 3 ) y c = y a - { 1 + [ y opz ′ ⁡ ( x a ) ] 2 } y opz ′′ ⁡ ( x a ) ( 4 ) wherein y′ opz (X a ) is the 1 st derivative of the aspherical function form at a junction point A(x a ,y a ) of the transition zone with the central optical zone, y″ opz (x a ) is the 2 nd derivative of the aspherical function form at the junction point A(x a ,y a ); and (e) a peripheral zone that comprises one or more sphere sub-surfaces, wherein all sub-surfaces are tangent to each other.