Myopia control lens and related methods
An ophthalmic lens for myopia control. A first surface of the lens varies across the lens to form a first surface power map. A second surface of the lens varies across the lens to form a second surface power map. Each of the first and second surface power maps comprise a spiral. The spirals formed by the first and second surface power maps twist in opposing directions. Related methods are also described.
1. An ophthalmic lens for controlling progression of myopia, the lens including an outer surface that is convex, the outer surface shaped to form a first surface power map, and an inner surface that is concave, the inner surface shaped to form a second surface power map, wherein:
the first surface power map comprises a spiral;
the second surface power map comprises a spiral; and
the spirals provided by the first and second surface power maps twist in opposing directions.
2. The ophthalmic lens according to claim 1 , wherein the lens is a contact lens or a spectacle lens.
3. The ophthalmic lens according to claim 1 , wherein the power varies smoothly across the first and second surface power maps.
4. The ophthalmic lens according to claim 3 , wherein the power of the inner and outer surfaces varies both radially and angularly as a rounded square wave or a sinusoid.
5. The ophthalmic lens according to claim 1 , wherein each of the first and second power maps has a power that varies substantially periodically both radially outwards from and angularly about an optical axis of the lens.
6. The ophthalmic lens according to claim 5 , wherein the periods of the radial and angular variations are each substantially constant across the first and second surface power maps.
7. The ophthalmic lens according to claim 5 , wherein a period of one or more 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 ophthalmic lens according to claim 5 , wherein:
the radial variation has a period of greater than 100 microns; and
the angular variation has a period of greater than 6 degrees.
9. The ophthalmic lens according to claim 1 , wherein the spirals formed on the first and second surface power maps twist in opposing directions but are otherwise substantially identical.
10. The ophthalmic lens according to claim 1 , wherein each spiral comprises at least four arms.
11. The ophthalmic lens according to claim 1 , wherein each arm of each spiral twists through at least half a rotation.
12. The 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 spirals are formed in the outer region; and
the spirals do not extend into the central region.
13. The ophthalmic lens according to claim 12 , wherein the central region has a diameter of less than 50% of that of the spirals.
14. The ophthalmic lens according to claim 12 , 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.
15. The 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 spirals are formed within the central region; and
the spirals do not extend into the outer region.
16. A method of controlling myopia progression in a person, the method comprising:
providing the multifocal ophthalmic lens according to claim 1 to a person in need of control of myopia progression.
17. The ophthalmic lens according to claim 1 , wherein each spiral comprises a plurality of arms, and each of the plurality of arms comprises a peak arm and a trough arm.
18. A method of manufacturing an ophthalmic lens, the method comprising:
operating a lathe to shape a concave surface and a convex surface of one of: a lens, a mould for a lens, or an insert for manufacturing a mould for a lens such that:
the concave surface forms a first surface power map;
the convex surface forms a second surface power map;
the first surface power map and the second surface power map each comprise a spiral; and
the spirals formed by the first surface power map and the second surface power map twist in opposing directions.