Contact lens for keratoconus
The present invention is directed to a non-deforming contact lens for keratoconus patients having a displaced central zone. In particular, the central zone is displaced from the geometric center of the lens. The shape of the central zone is egg or spoon-shaped and is rotationally asymmetrical with one semi-meridian that is shorter than a corresponding semi-meridian. An intermediate transition zone is formed integral with the periphery of the central zone, and a peripheral zone is formed integral with the periphery of the intermediate transition zone, forming a round contact lens.
1. A contact lens for keratoconus having a posterior surface facing toward an eye having at least three zones, comprising:
a central zone displaced from the two-dimensional geometric center of the contact lens in the z direction, wherein the central zone is rotationally asymmetrical having a meridian with a first semi-meridian shorter in radius than a corresponding second semi-meridian;
an intermediate transition zone formed integral with a periphery of the central zone; and
a peripheral zone formed integral with a periphery of the intermediate transition zone.
2. The contact lens of claim 1 , wherein the intermediate transition zone includes an initial local slope equivalent to a final local slope of the central zone in all semi-meridians.
3. The contact lens of claim 1 , wherein the intermediate transition zone includes a rotational asymmetry resulting in equivalent sagittal height circumferentially at its junction with the peripheral zone.
4. The contact lens of claim 1 , wherein the intermediate transition zone includes a geometry resulting in non-equivalent sagittal height circumferentially at its junction with the peripheral zone.
5. The contact lens of claim 4 , wherein the peripheral zone includes a rotational asymmetry resulting in equivalent sagittal height circumferentially at an edge of the contact lens.
6. The contact lens of claim 4 , wherein the intermediate transition zone includes an initial local slope equivalent to a final local slope of the central zone in all semi-meridians.
7. The contact lens of claim 1 , wherein one semi-meridian of the central zone is lower in eccentricity than its corresponding semi-meridian.
8. The contact lens of claim 1 , wherein the eccentricity of the semi-meridians of the central zone are substantially equivalent.
9. The contact lens of claim 1 , wherein the semi-meridians of the central zone are unequal in eccentricity and have radii longer than a shortest semi-meridian.
10. The contact lens of claim 1 , further comprising an anterior lens surface containing a correction for neutralizing low and higher order aberrations of a lens-eye system.
11. A contact lens for keratoconus having a posterior surface facing toward an eye having at least three zones, comprising:
a central zone displaced from the two-dimensional geometric center of the contact lens in the z direction, wherein the central zone is rotationally asymmetrical having a meridian with a first semi-meridian with an eccentricity different than a corresponding second semi-meridian;
an intermediate transition zone formed integral with a periphery of the central zone; and
a peripheral zone formed integral with a periphery of the intermediate transition zone.
12. The contact lens of claim 11 , wherein the intermediate transition zone includes an initial local slope equivalent to a final local slope of the central zone in all semi-meridians.
13. The contact lens of claim 11 , wherein the intermediate transition zone includes a rotational asymmetry resulting in equivalent sagittal height circumferentially at its junction with the peripheral zone.
14. The contact lens of claim 11 , wherein the intermediate transition zone includes a geometry resulting in non-equivalent sagittal height circumferentially at its junction with the peripheral zone.
15. The contact lens of claim 14 , wherein the peripheral zone includes a rotational asymmetry resulting in equivalent sagittal height circumferentially at an edge of the contact lens.
16. The contact lens of claim 14 , wherein the intermediate transition zone includes an initial local slope equivalent to a final local slope of the central zone in all semi-meridians.
17. The contact lens of claim 11 , wherein one semi-meridian of the central zone is lower in eccentricity than its corresponding semi-meridian.
18. The contact lens of claim 11 , wherein the eccentricity of the semi-meridians of the central zone are substantially equivalent.
19. The contact lens of claim 11 , wherein the semi-meridians of the central zone are unequal in eccentricity and have radii longer than a shortest semi-meridian.
20. The contact lens of claim 11 , further comprising an anterior lens surface containing a correction for neutralizing low and higher order aberrations of a lens-eye system.