Patent EA-005124-B1 (EA)
Title: An ophthalmic lens
Inventor: PIERS PATRICIA ANN
IPC: G02C7/04
Filed: 2002-03-20
Abstract: 1. An ophthalmic lens comprising a diffractive part and a refractive part, characterized in that it a) a refractive part is configured with at least one aspheric surface, which is adapted to compensate a passing wavefront at least partly for the spherical aberration introduced by at least one of the optical parts of the eye and optionally also by the refractive and/or diffractive part, b) a diffractive part is a diffractive surface profile consisting of a number of concentric rings, said diffractive part which is adapted to compensate a passing wavefront at least partly for the chromatic aberration introduced by at least one of the optical parts of the eye, said refractive and diffractive parts together contribute to a required power of the lens. 2. An ophthalmic lens according to claim 1, wherein the diffractive part also is capable of compensating a passing wavefront at least partly for chromatic aberration introduced by the refractive part of the lens. 3. An ophthalmic lens according to claim 1 or 2, wherein the refractive part also is capable of compensating a passing wavefront at least partly for at least one type of monochromatic aberration introduced by the diffractive part of the lens. 4. An ophthalmic lens according to any one of the preceding claims, wherein said lens is designed to compensate at least partly for values of monochromatic and chromatic aberrations measured in the eye of an individual patient. 5. An ophthalmic lens according to any one of the claims 1-3, wherein said lens is designed to compensate at least partly for an average value of monochromatic and/or chromatic aberration determined by measurements of a group of people. 6. An ophthalmic lens according to any one of the preceding claims, wherein said refractive part comprises at least one surface, which is configured to compensate a passing wavefront at least partly for spherical aberration introduced by at least one of the optical parts of the eye and optionally also by the diffractive part of the lens. 7. An ophthalmic lens according to claim 1, wherein said aspheric surface is capable of compensating at least partly for spherical aberration as expressed by the 11 t normalized Zernike term. 8. An ophthalmic lens according to any one of the preceding claims, wherein the lens together with the eye provides a polychromatic image quality, which when expressed as MTF (50) (Modulation Transfer Function at 50 cycles per millimeter) performs at least about 40% higher than an aspheric lens compensating for the same spherical aberration as the inventive lens but without compensating for the chromatic aberration. 9. An ophthalmic lens according to claim 1, wherein the profile height of the diffractive surface profile equals an integer number of the design wavelength. 10. An ophthalmic lens according to claim 1, wherein the profile height of the diffractive surface profile is one design wavelength. 12. An ophthalmic lens according to claims 10 and 11, wherein the radial width of the first zone of the diffractive profile is 0.365 mm for a 20 D lens. 13. An ophthalmic lens according to claim 1, wherein the profile height of the diffractive surface profile is two design wavelengths. 14. An ophthalmic lens according to any one of claims 1-10,12,13, wherein the anterior surface of the lens is an aspheric surface and the posterior surface of the lens is flat and has a diffractive profile. 15. An ophthalmic lens according to claims 13 and 14, wherein the radial width of the first zone of the diffractive profile is 0.516 mm for a 20 D lens. 16. An ophthalmic lens according to any one of claims 1-13, 15, wherein the shape of the lens is equi-biconvex. 17. An ophthalmic lens according to any one of claims 1-15, wherein the shape of the lens is convex-plano. 18. An ophthalmic lens according to any one of the preceding claims, wherein the lens material is a silicon. 19. An ophthalmic lens according to any one of claims 1-17, wherein the lens material is PMMA or an hydrogel. 20. A method for designing an ophthalmic lens according to any one of the claims 1-19, comprising: - manufacturing a lens blank provided from a refractive part and a diffractive parts, - combining a refractive part and a diffractive part of the lens such that they together compensate a passing wavefront at least partly for at least one type of monochromatic aberration and for chromatic aberration introduced by at least one of the optical parts of the eye, while dimensioning said refractive and diffractive parts to provide the lens with a required power. 21. A method according to claim 20, further comprising the steps of: - measuring at least one type of monochromatic aberration provided to a wavefront from at least one of the optical parts of an eye; and combining the refractive and diffractive parts of the lens such that they compensate at least partly for the measured monochromatic aberration. 22. A method for designing an ophthalmic lens according to claim 20 or 21, further comprising the steps of: - measuring the spherical aberration provided to a wavefront from at least one of the optical parts of an eye; - combining the refractive part and the diffractive part of the lens such that they together compensate a passing wavefront at least partly for the measured spherical aberration introduced by at least one of the optical parts of the eye. 23. A method according to any one of the claims 20-22, comprising measuring the chromatic aberration provided to a wavefront from at least one of the optical parts of the eye and combining the refractive and diffractive parts of the lens such that they together compensate a passing wavefront at least partly for the measured chromatic aberration introduced by at least one of the optical parts of the eye. 24. A method according to any one of the claims 20-22, comprising combining the refractive and diffractive part of the lens such that they together compensate a passing wavefront at least partly for an average chromatic aberration of human eyes in general or of eyes in a specific group of people. 25. A method according to claim 20, comprising combining the refractive and the diffractive part of the lens such that they together compensate a passing wavefront at least partly for an average monochromatic aberration of eyes in general or of eyes in a specific group of people. 26. A method according to any one of the claims 20-25, comprising combining the refractive and diffractive part of the lens such that the diffractive part compensates a passing wavefront at least partly for the chromatic aberration introduced by the refractive part of the lens. 27. A method according to any one of the claims 20-26, comprising combining the refractive and the diffractive part of the lens such that the refractive part compensates a passing wavefront at least partly for the monochromatic aberration introduced by the diffractive part of the lens. 28. A method according to any one of the claims 20-27, comprising measuring the refractive error of the eye and dimensioning the refractive and diffractive parts of the lens such that they together compensate at least partly for the refractive error of the eye. 29. A method according to any one of the claims 20-28, comprising providing the refractive part with an aspheric surface, which compensates a passing wavefront at least partly for the spherical aberration introduced by at least one of the optical parts of the eye and optionally also by the diffractive part of the lens. 30. A method according to any one of the claims 20-29, comprising providing the refractive part with an aspheric surface, which is adapted to compensate at least partly for spherical aberration as expressed by the11-th normalized Zernike term. 31. A method according to any one of the claims 20-30, comprising providing the lens with a diffractive surface profile. 32. A method according to claim 31, comprising providing the diffractive surface profile with a number of concentric rings. 33. A method according to claim 32, comprising providing the diffractive surface profile with a profile height that equals an integer number of the design wavelength. 34. A method according to any one of the claims 20-33, comprising providing the anterior surface of the lens with an aspheric refractive lens and superimposing a diffractive profile on top of it. 35. A method of designing an ophthalmic lens according to any one of the claims 1-19, characterised by the steps of: i) selecting an eye model with a refractive aspheric ophthalmic lens of a predetermined refractive power and a predetermined amount of at least one monochromatic aberration; ii) estimating the power of said eye model at different wavelengths, so as to determine the chromatic aberration of the eye model; iii) estimating a correction function of how the power varies with the wavelength to be an ideal compensation for said chromatic aberration of the eye model; iv) finding a linear function of how power varies with the wavelength, which suitably approximates said correction function; v) calculating a provisional zone width of a diffractive profile corresponding to this linear function and also calculating the diffractive power of this diffractive profile; vi) reducing the refractive power of the refractive ophthalmic lens by the amount of power calculated for the diffractive profile; vii) estimating a new correction function of step iii), finding a new linear function of step iv) and calculating a new provisional zone width and a new diffractive power for a new diffractive profile corresponding to this new linear function; viii) adjusting the refractive power of the refractive ophthalmic lens such that the total power of a hybrid lens, which comprises both the refractive ophthalmic lens and the diffractive profile and which is adapted to replace the refractive ophthalmic lens in the eye model, equals the predetermined power; ix) repeating steps vii) to viii) until a suitable combination of a refractive