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, the spiral having a variation across at least a portion of the lens, wherein the spiral has a first periodic component with a period of 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, and wherein the first and second periodic components vary smoothly as a sinusoid, a rounded square wave, or a square wave.
2 . The multifocal ophthalmic lens according to claim 1 , wherein the second periodic component has a period of greater than 6 degrees.
3 . 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.
4 . The multifocal ophthalmic lens according to claim 1 , 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.
5 . 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.
6 . 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.
7 . 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.
8 . The multifocal ophthalmic lens according to claim 7 , wherein the central region has a diameter of less than 50% of that of the portion.
9 . The multifocal ophthalmic lens according to claim 7 , 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.
10 . 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.
11 . 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.
12 . The multifocal ophthalmic lens according to claim 11 , wherein, at a pre-determined radial distance from the centre of the portion, the spiral changes its direction of rotation.
13 . The multifocal ophthalmic lens according to claim 1 , wherein the ophthalmic lens is a contact lens, a spectacle lens, or an intraocular lens.
14 . 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, the spiral having a variation across at least a portion of the lens, mould or insert, wherein the spiral has a first periodic component with a period of 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, and wherein the first and second periodic components vary smoothly as a sinusoid, a rounded square wave, or a square wave.
15 . 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.
16 . The multifocal ophthalmic lens according to claim 7 , wherein the central region has an optical power corresponding to a distance vision correction.
17 . A multifocal ophthalmic lens according to claim 7 , wherein the central region has an optical power corresponding to a near vision correction.