Multifocal ophthalmic lens and related methods
A multifocal ophthalmic lens has a surface that varies across at least a portion of the lens to form a surface power map. The surface power map comprises a spiral, with a power that varies substantially periodically both radially outwards from and angularly about an optical axis of the lens. A period of the radial variation is greater than 100 microns and a period of the angular variation is greater than 6 degrees. Methods of making and using the multifocal ophthalmic lens are also described.
1. A multifocal ophthalmic lens wherein:
a first surface of the lens varies across at least a portion of the lens to form a first surface power map;
the first surface power map comprises a spiral, with a power that varies substantially periodically both radially outwards from and angularly about an optical axis of the lens;
a period of the radial variation is greater than 100 microns; and
a period of the angular variation is a unit fraction of 360 degrees.
2. The multifocal ophthalmic lens according to claim 1 , wherein:
the ophthalmic lens is a contact lens; and
the first surface varies across an optic zone of the contact lens to form the first surface power map.
3. The multifocal ophthalmic lens according to claim 1 , wherein the power varies smoothly across the portion.
4. The multifocal ophthalmic lens according to claim 3 , wherein the power varies both radially and angularly as one of: a rounded square wave and a sinusoid.
5. The multifocal ophthalmic lens according to claim 1 , wherein the power varies both radially and angularly as a square wave.
6. The multifocal ophthalmic lens according to claim 1 , wherein the periods of the radial and angular variations are each substantially constant across the portion.
7. The multifocal ophthalmic lens according to claim 1 , wherein the period of at least one of the radial and angular variations changes according to one or both of: a radial distance from the optical axis of the lens and an angular position about the optical axis of the lens.
8. The multifocal ophthalmic lens according to claim 1 , wherein:
the lens comprises a central region and an outer region, the central region immediately surrounding the optical axis of the lens and the outer region surrounding the central region;
the power of the central region does not vary periodically across the central region; and
the outer region comprises the angular and radial variations in power.
9. The multifocal ophthalmic lens according to claim 8 , wherein the central region has a diameter of less than 50% of that of the portion.
10. The multifocal ophthalmic lens according to claim 8 , wherein:
the lens comprises a transition region, the transition region surrounding the central region and the outer region surrounding the transition region; and
the power of the transition region varies to provide a smooth transition between the central and outer regions.
11. The multifocal ophthalmic lens according to claim 1 , wherein:
the lens comprises a second surface which varies across the portion of the lens to form a second surface power map;
the second surface power map comprises a spiral, with a power that varies substantially periodically radially outwards from and angularly about the optical axis of the lens;
a period of the radial variation of the second surface power map is greater than 100 microns; and
a period of the angular variation of the second surface power map is a unit fraction of 360 degrees.
12. The multifocal ophthalmic lens according to claim 11 , wherein:
the first surface power map and the second surface power map each comprise a spiral; and
the spirals provided by the first and second surface power maps twist in opposing directions.
13. The multifocal ophthalmic lens according to claim 11 , wherein the multifocal ophthalmic lens is a myopia control lens.
14. A method of manufacturing a multifocal ophthalmic lens, the method comprising:
operating a lathe to shape a first surface of at least one of: a lens, a mould for a lens, or an insert for manufacturing a mould for a lens, such that:
the first surface varies across at least a portion of the lens to form a first surface power map;
the first surface power map comprises a spiral;
the first surface power map varies substantially periodically both radially outwards from and angularly about an optical axis of the lens;
a period of the radial variation is greater than 100 microns; and
a period of the angular variation is a unit fraction of 360 degrees.
15. The method according to claim 14 , further comprising operating a lathe to shape a second surface of the lens, the mould, or the insert, such that:
the second surface varies across the portion of the lens to form a second surface power map;
the second surface power map comprises a spiral;
the second surface power map varies substantially periodically both radially outwards from and angularly about an optical axis of the lens;
a period of the radial variation is greater than 100 microns; and
a period of the angular variation is a unit fraction of 360 degrees.
16. A method of improving vision of a person, the method comprising:
providing a multifocal ophthalmic lens to a person in need of improved vision, wherein
a first surface of the lens varies across at least a portion of the lens to form a first surface power map;
the first surface power map comprises a spiral, with a power that varies substantially periodically both radially outwards from and angularly about an optical axis of the lens;
a period of the radial variation is greater than 100 microns; and
a period of the angular variation is a unit fraction of 360 degrees.