Multifocal ophthalmic lenses and related methods
A multifocal ophthalmic lens wherein a first surface of the lens is shaped to form a surface power map and a second surface of the lens is shaped to form a second surface power map. The first surface power map and the second surface power map together form a lens power map. The first surface power map, the second surface power map, or the lens power map comprises a spiral. The spiral has a variation across at least a portion of the lens. Methods of making and using such lenses are also provided.
1. A multifocal ophthalmic lens, wherein:
a first surface of the lens is shaped to form a first surface power map;
a second surface of the lens is shaped to form a second surface power map;
the first and second surface power maps together form a lens power map;
the first surface power map, the second surface power map, or the lens power map comprises a spiral having a first periodic component having a constant period that is greater than 100 microns in a radial direction extending outwards from the centre of the portion, and a second periodic component in an azimuthal direction about the centre of the portion, the spiral having a variation across at least a portion of the lens.
2. The multifocal ophthalmic lens according to claim 1 , wherein the second periodic component has a constant period.
3. The multifocal ophthalmic lens according to claim 1 , wherein the first periodic component and/or the second periodic component varies as one of a square wave, a sinusoid, and a rounded square wave.
4. The multifocal ophthalmic lens according to claim 2 , wherein the second periodic component has a period of greater than 6 degrees.
5. The multifocal ophthalmic lens according to claim 1 , wherein the variation of the spiral comprises an offset in power, the offset changing according to a radial distance from the centre of the portion.
6. The multifocal ophthalmic lens according to claim 5 , wherein a peak power of one or more arms of the spiral varies according to one or both of: a radial distance from the centre of the portion and an azimuthal position about the centre of the portion.
7. The multifocal ophthalmic lens according to claim 1 , wherein:
a peak power of each arm of the spiral does not vary with radial distance from the centre of the portion; and
the peak power of at least one arm of the spiral differs from that of the other arms.
8. The multifocal ophthalmic lens according to claim 1 , wherein each of the first surface power map and the second surface power map vary smoothly across the portion.
9. The multifocal ophthalmic lens according to claim 1 , wherein:
the portion of the lens comprises a central region and an outer region, the outer region surrounding the central region;
the lens power map within the outer region comprises the spiral; and
the lens power map does not vary periodically within the central region.
10. The multifocal ophthalmic lens according to claim 9 , wherein the central region has a diameter of less than 30% of that of the portion.
11. The multifocal ophthalmic lens according to claim 9 , wherein lens is a contact lens and the central region is smaller than the minimum pupil size of a wearer of the lens.
12. The multifocal ophthalmic lens according to claim 9 , wherein:
the lens comprises a transition region, the transition region surrounding the central region and the outer region surrounding the transition region; and
the lens power map varies such that the transition region provides a smooth transition between the central zone and the outer zone.
13. The multifocal ophthalmic lens according to claim 1 , wherein a twist rate of the spiral varies according to a radial distance from the centre of the portion.
14. The multifocal ophthalmic lens according to claim 1 , wherein a width of one or more arms of the spiral differs from a corresponding width of the other arms of the spiral.
15. The multifocal ophthalmic lens according to claim 14 , wherein, at a pre-determined radial distance from the centre of the portion, the spiral changes its direction of rotation.
16. The multifocal ophthalmic lens according to claim 1 , wherein the ophthalmic lens is a contact lens, a spectacle lens, or an intraocular lens.
17. A method of manufacturing a multifocal ophthalmic lens, the method comprising:
operating a lathe to shape a first surface of one of: a lens, a mould for a lens, or an insert for manufacturing a mould for a lens to form a first surface power map;
operating a lathe to shape a second surface of the lens, mould, or insert to form a second surface power map;
wherein:
the combination of the first and second surface power maps forms a lens power map;
the first surface power map, the second surface power map, or the lens power map comprises a spiral having a first periodic component having a substantially constant period that is greater than 100 microns in a radial direction extending outwards from the centre of the portion, and a second periodic component in an azimuthal direction about the centre of the portion, the spiral having a variation across at least a portion of the lens, mould or insert.
18. A method of improving vision of a person, the method comprising:
providing a multifocal ophthalmic lens according to claim 1 to a person in need of improved vision.
19. The multifocal ophthalmic lens according to claim 1 , in which the ophthalmic lens is a centre distance contact lens, or a centre near contact lens.
20. The multifocal ophthalmic lens according to claim 9 , wherein the central region has an optical power corresponding to a distance vision correction.
21. The multifocal ophthalmic lens according to claim 9 , wherein the central region has an optical power corresponding to a near vision correction.