Multifocal ophthalmic lenses and related methods

Abstract

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 varies across at least a portion of the lens. Methods of making and using such lenses are also provided.

Description

Technical Field

[0001] The present invention relates to multifocal ophthalmic lenses and related methods. More particularly, but not exclusively, the present invention relates to a multifocal ophthalmic lens having a lens power diagram comprising a spiral that varies across a portion of the lens. The present invention also relates to methods of making and using such lenses. Background Art

[0002] In the context of the present disclosure, a multifocal ophthalmic lens is an ophthalmic lens that provides focus at more than one distance simultaneously. This is typically achieved by subdividing the ophthalmic lens into a plurality of zones. Zones in a first subset of the plurality of zones are provided with a first lens power corresponding to a first focus distance (e.g., far vision). Zones in a second subset of the plurality of zones are provided with a second lens power corresponding to a second focus distance (e.g., near vision).

[0003] In a multifocal contact lens, the multiple zones are typically formed as concentric circles centered on the optical axis of the contact lens, with the concentric circles alternating between a first lens power and a second lens power. Thus, the power diagram of the optic zone of a typical multifocal contact lens includes at least two alternating concentric circles of the first and second lens powers. However, such contact lenses can present difficulties for the wearer under changing light conditions. In lower light conditions, the pupil of the wearer's eye dilates to provide a larger aperture for incoming light, thereby increasing the amount of light received by the eye and thereby providing improved low-light vision. As conditions brighten, the pupil constricts to provide a smaller aperture, thereby limiting the amount of light received by the eye. As the wearer's pupil dilates and constricts, the number of concentric rings on the contact lens positioned across the wearer's entrance pupil (located above the wearer's pupil) will also change. As the pupil dilates, a greater number of concentric rings will be positioned across the wearer's entrance pupil. Similarly, as the pupil constricts, fewer concentric rings will be positioned across the wearer's entrance pupil. Because the concentric rings alternate between the first and second lens powers, the ratio of the first lens power to the second lens power, positioned across the wearer's entrance pupil, will change as the wearer's pupil contracts and dilates. As the pupil contracts, the amount of either near or far focus decreases until the pupil contracts to the diameter of the next smallest concentric circle. At this point, the amount of either near or far focus decreases until the pupil contracts again to the diameter of the next smallest concentric circle. As the pupil contracts, this cycle repeats, causing the ratio of near to far focus to change as the pupil contracts. It should be understood that the same effect occurs in reverse when the pupil dilates. These changes in the ratio of near to far focus can cause the wearer to lose focus or even lose multifocal vision. Generally, the more the wearer's pupil contracts, the more severe the change in ratio. Consequently, in bright conditions, particularly when the pupil contracts to near its smallest size, wearers of such multifocal contact lenses may find that the ability of the multifocal contact lenses to provide high acuity in both near and far vision is compromised. This effect is further exacerbated for dual-zone multifocal contact lenses, one of the most popular designs among multifocal contact lenses. A dual-zone multifocal contact lens comprises an inner circle of a first lens power and a single, surrounding, peripheral ring of a second lens power. Consequently, the more the wearer's pupil constricts, the less the second lens power is positioned across the wearer's entrance pupil. In some cases, the pupil may even constrict to the point where neither second lens power is positioned across the wearer's entrance pupil, resulting in a complete loss of multifocal vision. Other multifocal contact lenses may utilize similar principles, but instead of alternating concentric rings, may include aspheric power profiles to provide a more gradual transition from near to far vision power compared to the alternating ring embodiment.

[0004] The present invention seeks to alleviate the above mentioned problems.Alternatively or additionally, the present invention seeks to provide an improved multifocal ophthalmic lens. Summary of the Invention

[0005] According to a first aspect, the present invention provides a multifocal ophthalmic lens. A first surface of the ophthalmic lens is shaped to form a first surface power map. A second surface of the ophthalmic lens is shaped to form a second surface power map. The first and second surface powers Figure 1 The first surface power map, the second surface power map, and / or the lens power map together form a lens power map. The first surface power map, the second surface power map, and / or the lens power map include a spiral. The spiral varies across at least a portion of the lens.

[0006] Contact lenses with a power profile that includes a spiral can provide a more stable ratio of near to distance vision focus despite changes in the wearer's pupil size. As light conditions change, the wearer's pupil will dilate and contract to adjust the amount of light admitted to the eye. As conditions brighten, the pupil contracts to reduce the amount of light admitted to the eye. As conditions darken, the pupil dilates to admit more light to the eye. Prior art multifocal contact lenses may use alternating concentric rings of near and distance focus, such as a central circle of distance focus surrounded by a peripheral circle of near focus. Alternatively, prior art multifocal contact lenses may use an aspheric power profile within the optic zone. As discussed above, as the wearer's pupil dilates and constricts, these contact lenses vary in the ratio of near to distance focus provided across the wearer's entrance pupil. These variations can cause the wearer to be distracted or even lose multifocal vision.

[0007] A spiral power map as disclosed herein can provide a constant ratio of near focus to far focus across the entire range of diameters encompassing the spiral map. Thus, as the pupil constricts or dilates, a contact lens having a spiral power map can maintain a substantially constant ratio of near focus to far focus (where the spiral covers the entire optic zone of the lens) or a monotonically varying ratio (where the spiral covers only a radial sub-portion of the optic zone of the lens). Thus, a contact lens having a spiral power map provides improved multifocal vision in the presence of variable lighting conditions.

[0008] The skilled person will appreciate that, in the case of a power diagram that varies smoothly (e.g., like a sinusoidal curve), the power diagram will include lens powers other than just a first lens power corresponding to near vision and a second lens power corresponding to distance vision. In this case, the power diagram will also include regions having lens powers between the first and second powers (e.g., intermediate lens powers). It will be appreciated that this does not affect or diminish the advantage described above of providing a consistent and stable variation in the added power positioned across the wearer's entrance pupil. The skilled person will appreciate that this advantage stems from the fact that, for a spiral power diagram, the composition of the added power at a particular radius does not vary as a function of the radial distance from the optical axis of the lens.

[0009] According to a second aspect of the present invention, a method for manufacturing a multifocal ophthalmic lens is also provided. The method includes operating a lathe to shape a first surface of one of the following: a lens, a mold of a lens, or an insert of a mold for manufacturing a lens, to form a first surface power map. The method further includes operating a lathe to shape a second surface of the lens, mold, or insert to form a second surface power map. The first surface power map and the second surface power map are Figure 1 The first surface power map, the second surface power map, or the lens power map together form a spiral that varies across at least a portion of the lens. The portion includes a visual zone of the lens.

[0010] In a third aspect of the present invention, a method of using the multifocal ophthalmic lens described herein is also provided. The method can be effective in improving the vision of a wearer of a presbyopic lens (e.g., a person aged 40 or over). Alternatively, the method can be effective in reducing the progression of ametropia, such as reducing the progression of myopia or hyperopia. When the present lens is used to reduce the progression of myopia, the method comprises the step of providing the ophthalmic lens to a person whose eyes are able to adapt. An embodiment of the method may comprise the step of providing the ophthalmic lens to a person aged about 5 to about 25. The providing may be performed by an eye care practitioner (e.g., an optician or optometrist). Alternatively, the providing may be performed by a lens dispenser arranged to deliver the ophthalmic lens to the lens wearer.

[0011] It will of course be appreciated that features described with respect to one aspect of the invention may be incorporated into other aspects of the invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0013] Figure 1 showing a contact lens according to an example embodiment of the present invention;

[0014] Figure 2 a power diagram showing a first surface of the optic zone of a contact lens according to a first embodiment of the present invention;

[0015] Figure 3 A lens power diagram showing a first surface of an optic zone of a contact lens according to a second embodiment of the present invention;

[0016] Figure 4 a lens power diagram showing the optic zone of a contact lens according to a third embodiment of the present invention;

[0017] Figure 5shows a flowchart illustrating the steps of a method according to a fourth embodiment of the present invention;

[0018] Figure 6 Spectacle lenses according to example embodiments of the invention are shown. DETAILED DESCRIPTION

[0019] According to a first aspect, the present invention provides a multifocal ophthalmic lens. 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. A skilled person will appreciate that the surface change includes a change in surface curvature. The first and second surface powers are Figure 1 The first surface power map, the second surface power map or the lens power map comprises a spiral having a variation across at least a portion of the lens.

[0020] It will be appreciated that either of the first surface power map and the second surface power map may have a substantially constant power of +0 D across the power map. For the purposes of this description, the corresponding surface of the lens is still considered to form a surface power map, even if the surface power map ultimately does not provide focus or vision modification.

[0021] The ophthalmic lens may be a contact lens. Alternatively, the ophthalmic lens may be an intraocular lens or a spectacle lens.

[0022] The first surface may vary across a viewing zone of the lens to form a first surface power map. Similarly, the second surface may vary across a viewing zone of the lens to form a second surface power map. Thus, portions of the lens may correspond to viewing zones of the lens.

[0023] It will be appreciated that the lens will include an optic zone that provides vision correction. Contact lenses and intraocular lenses according to embodiments of the present invention may also include a surrounding peripheral zone that does not provide additional focusing or vision correction. In such embodiments, the peripheral zone may serve only to help maintain the contact lens in position on or in the wearer's eye. Thus, the skilled artisan will appreciate that the surface power map is defined by the profile of the first surface spanning the optic zone of the lens. In the context of the present invention, the profile of the lens surface outside the optic zone (e.g., in the peripheral zone) is not considered to define the surface power map. Similar considerations apply to intraocular lenses, which may also include an optic zone and (optionally) a peripheral zone.

[0024] The optic zone of a contact lens according to embodiments of the present invention may have a diameter between 4 mm and 9 mm, depending on the type of contact lens. For example, the diameter of the optic zone may be about 5 mm, or about 6 mm, or about 7 mm, or about 8 mm. The diameter of the optic zone of a contact lens may be between 7 mm and 9 mm. The optic zone includes an optical axis corresponding to the geometric center of the optic zone.

[0025] In the case of a spectacle lens, the entire lens may be used to provide vision correction, not just a portion of the lens. Thus, an ophthalmic lens may be a spectacle lens. The first surface may be formed across the entire lens to form a first surface power map.

[0026] The spiral may have a first periodic component in a radial direction extending outward from the center of the portion and a second periodic component in an azimuthal direction about the center of the portion. The first and second components may each be formed on the same one of the first and second surfaces.

[0027] The azimuthal direction is understood to refer to a rotation about the center of the portion. Thus, movement in the azimuthal direction is equivalent to a change in angular position about the center of the portion. It will be appreciated that in such embodiments, the change in the focal power diagram forming the spiral is the sum of the first and second periodic components.

[0028] One or both of the first and second periodic components may have a constant magnitude across the portion.

[0029] The first periodic component (in the radial direction) may have a period greater than 100 microns. The second periodic component may have a period greater than 6 degrees. The period of the first periodic component may be greater than 200 microns, preferably greater than 400 microns, and more preferably greater than 800 microns. The period of the first periodic component may be less than 2 mm, preferably less than 1.5 mm, and more preferably less than 1 mm. The period of the second periodic component (in the azimuthal direction) may be greater than 6 degrees, preferably greater than 9 degrees, preferably greater than 18 degrees, and more preferably greater than 36 degrees. The period of the second periodic component may be less than 180 degrees, preferably less than 90 degrees, and more preferably less than 45 degrees.

[0030] Thus, in embodiments, the first periodic component may have a period greater than 100 microns and the second periodic component may have a period greater than 6 degrees, preferably greater than 9 degrees, more preferably greater than 18 degrees, and more preferably greater than 36 degrees. In other embodiments, the first periodic component may have a period greater than 200 microns and the second periodic component may have a period greater than 6 degrees, preferably greater than 9 degrees, more preferably greater than 18 degrees, and more preferably greater than 36 degrees. In other embodiments, the first periodic component may have a period greater than 400 microns and the second periodic component may have a period greater than 6 degrees, preferably greater than 9 degrees, more preferably greater than 18 degrees, and more preferably greater than 36 degrees. In other embodiments, the first periodic component may have a period greater than 800 microns and the second periodic component may have a period greater than 6 degrees, preferably greater than 9 degrees, more preferably greater than 18 degrees, and more preferably greater than 36 degrees.

[0031] The variation in the spiral may include an offset in power. The offset may vary as a function of radial distance from the center of the portion. In embodiments, the offset may include one of a plurality of components. Thus, the plurality of components may further include an offset component that varies (e.g., linearly, exponentially, or monotonically) with radial distance from the center of the lens. For example, the offset may provide additive power that decays linearly radially outward from the center of the portion.

[0032] The peak power of one or more arms of the spiral may vary depending on one or both of the radial distance from the center of the segment and the azimuthal position about the center of the segment. The magnitude of the periodic component may vary depending on one or both of the radial distance from the center of the segment and the azimuthal position about the center of the segment.

[0033] The peak focal power of each arm of the spiral may not vary with radial distance from the center of the portion. The peak focal power of at least one arm of the spiral is different from the peak focal power of the other arms. Thus, it can be said that each arm of the spiral provides a different lens power. Thus, multifocal vision may be provided by the arms of the spiral. The peak focal power of each arm of the spiral may be different from the peak focal power of the other arms. It will be appreciated that this feature can be specified as a variation of the periodic component with respect to both the radial distance from the center of the portion and the azimuthal position about the center of the portion. Thus, the periodic component may vary with respect to both the radial distance from the center of the portion and the azimuthal position about the center of the portion, such that the peak focal power of at least one arm (e.g., each arm) of the spiral is different from the peak focal power of the other arms.

[0034] The power of the first surface power map varies smoothly across the portion. The power of the second surface power map varies smoothly across the portion. Thus, the periodic component may vary smoothly (e.g., a sinusoidal curve or a rounded square wave). Each of the surface power maps may vary continuously, without any discontinuities. The power may vary across the portion at a rate of less than 80D / mm, preferably less than 40D / mm, and more preferably less than 20D / mm. The surface may vary smoothly across the portion. The surface may vary continuously, without any discontinuities. Smoothly varying power may result in a lens surface profile that is easier to manufacture using a lathe. Those skilled in the art will appreciate that manufacturing an ophthalmic lens using a lathe may include using the lathe to shape the surface of one or more of a lens (e.g., a contact lens), a mold for a lens (e.g., a contact lens mold), and an insert for a lens mold (e.g., an insert for a contact lens mold). Sharp transitions and features are difficult to achieve using a lathe. Consequently, when manufactured using a lathe, lenses having such features generally fail to reproduce the intended or desired definition. Thus, it will also be understood that the term smoothly in this context means sufficiently smooth to enable the desired shaping of the surface of a lens, lens mold, or insert for a lens mold using a lathe.

[0035] The focal power may vary like a square wave in one or both of the radial and azimuthal directions. The focal power may vary like a circular square wave in one or both of the radial and azimuthal directions. The focal power may vary like a sinusoidal curve in one or both of the radial and azimuthal directions.

[0036] The first and second periodic components may vary as one of the following: a square wave, a sinusoidal wave, and a rounded square wave. The period of one or both of the first and second periodic components may be substantially constant across a portion of the lens. Embodiments of the present invention in which the first and second periodic components have a substantially constant period across a portion produce a lens surface profile that is easier to manufacture using a lathe, compared to embodiments in which the radial and angular variations are not constant. In the case of contact lenses according to embodiments of the present invention, one or both of the first and second periodic components may have a substantially constant period from the periphery of the optic zone toward the visual axis of the optic zone.

[0037] Power variations in each of the radial and angular directions may be associated with a corresponding waveform. Additionally, the power profile of a waveform may be symmetrical, having a substantially equal balance between near and distance vision correction. Alternatively, the power profile may be biased toward either distance or near vision correction. Thus, the power profile of a waveform may be asymmetrical in one or both of the radial and angular directions.

[0038] The period of one or both of the first and second periodic components may vary as a function of either or both of the radial distance from the center of the lens portion and the azimuthal position about the center of the portion. Embodiments of the present invention in which the period of one or both of the first and second periodic components varies as a function of position on the lens may provide a lens in which the characteristics of the helix (e.g., its rotation rate or arm width) vary in different regions of the lens.

[0039] The changes in the period of the first periodic component (i.e., the periodic component in the radial direction) can be separated by a mixing zone, for example, a period that varies smoothly (e.g., linearly). Thus, the mixing zone can include concentric rings having a smoothly (e.g., linearly) varying period between a first zone having a first radially varying period and a second zone having a second radially varying period. Alternatively, the mixing zone can include a zone of smoothly (e.g., linearly) varying lens power. Thus, the mixing zone can provide a smooth transition between zones of radially varying different periods. The zones of radially varying different periods can be separated by two mixing zones and an intermediate zone of substantially constant lens power. The mixing zone can have a width (in plan view) of from about 25 microns to about 200 microns.

[0040] The spiral may comprise more than two arms, preferably more than 4 arms, more preferably more than 8 arms, more preferably more than 16 arms. Those skilled in the art will appreciate that the period of the second periodic component will determine the number of arms on the spiral.

[0041] The period of the first periodic component may be between 24 mm and 2 mm. The period of the second periodic component may be between 16 mm and 4 mm. Each arm of the spiral may twist between a quarter of a rotation and 40 rotations. Those skilled in the art will appreciate that the number of rotations by which the arms of the spiral twist is determined by the period of the first periodic component and the radius (or size) of the portion of the lens. It will be appreciated that reference to the radius of a portion (e.g., the optic zone of a contact lens) refers to a distance that is half the diameter of the portion in plan view. In this context, a plan view is intended to be considered a view along the optical axis of the lens.

[0042] The ratio of the period of the first periodic component to the period of the second periodic component may be greater than 0.1 mm:6°. Each arm of the spiral may be wider than 0.1 mm, preferably wider than 0.5 mm, and more preferably wider than 1 mm. Each arm width may be between 0.1 mm and 3 mm. Each arm width may be between 0.25 mm and 2 mm. Each arm width may be between 0.5 mm and 1 mm. The width of the spiral arms is determined when viewing the power diagram in plan view (i.e., along the optical axis of the lens), as shown in the accompanying drawings. Those skilled in the art will understand that the width of an arm at a given radius is defined as its perpendicular width (i.e., its width in a direction perpendicular to the given radius). In this context, the width of an arm is defined as the distance between two points immediately adjacent to each side of the arm, having the maximum or minimum gradient, between which the power undergoes a single positive or negative deviation. Those skilled in the art will understand that this definition of width provides a straight-line measurement of the arm width along a tangent to a circle of the given radius. Those skilled in the art will further understand that the measurement of width under this definition will differ from the measurement of the width of a wall considered as an arc of a circle having the given radius. Unlike the width measurement under the definition of line width, this arc-based measurement will be proportional to the period of the second periodic component. The magnitude of the difference between the widths obtained by these two methods will depend on the period of the second periodic component in the particular case at hand.

[0043] Each arm of the spiral may extend from a portion of the center of the lens to a portion of the periphery. Contact lenses according to embodiments of the present invention in which the arms of the spiral extend from the portion of the center to the portion of the periphery can provide a substantially constant ratio of the first lens power to the second lens power in the presence of varying pupil dilation. Such embodiments thus provide highly sensitive multifocal vision under a wide range of light conditions.

[0044] The twist rate of the spiral may vary depending on the radial distance from the center of the portion. The twist rate of the spiral will be understood to mean the rate at which the arms of the spiral rotate around the center of the spiral (i.e., the number of rotations of the arms around the center of the spiral across a given radial distance). It will be appreciated that a change in the twist rate of the spiral may be the result of a non-proportional change in the period of the first periodic component compared to a change in the period of the second periodic component (e.g., by changing the period of the first periodic component while maintaining the circumference of the second periodic component unchanged). The width of one or more arms of the spiral may be different from the corresponding widths of the other arms of the spiral. It will be appreciated that this feature may be defined as a periodic component providing a periodic component with a varying duty cycle across the portion.

[0045] It will be appreciated that the lens will have an average lens power. Furthermore, it will be appreciated that the lens will be divided between a first region of the lens having a lens power greater than average and a second region of the lens having a lens power less than average. The ratio of the first region to the second region may be between 10:1 and 1:10. The ratio of the first region to the second region may be between 5:1 and 1:5. The ratio of the first region to the second region may be between 3:1 and 1:3. The ratio of the first region to the second region may be between 2:1 and 1:2. The ratio of the first region to the second region may be approximately 1:1.

[0046] The portion of the lens that may be the optic zone may include a central zone and an outer zone. The central zone may directly surround the optical axis of the lens. The central zone may be offset from the geometric center of the lens. For example, it may be desirable to offset the central zone from the geometric center of the lens to allow the optical axis of the offset central zone to align with the lens wearer's pupil due to the lens' natural decentration on the eye. The outer zone may surround (e.g., directly surround) the central zone. The focal power of the central zone may not vary periodically across the central zone (e.g., have a substantially constant lens power across the central zone). The lens power profile in the outer zone may include a spiral. Thus, the outer zone may be said to include a spiral. Providing a contact lens having an optic zone with a lens power corresponding to distance vision and a central zone without periodic power variations can ensure that the wearer maintains high-acuity distance vision even in bright conditions. This is particularly advantageous for the wearer when driving, for example. Alternatively, the central zone may include a spiral, and the focal power of the outer zone may not vary periodically across the outer zone (e.g., have a substantially constant lens power across the outer zone).

[0047] A contact lens may include a peripheral zone that surrounds the optic zone and does not provide additional focusing or vision correction, and serves only to help maintain the contact lens in place on the wearer's eye. When worn on the eye, the contact lens rests on the cornea in a conventional manner, with the optic zone approximately covering the wearer's pupil. Thus, it will be understood that a contact lens according to the present invention may include an optic zone and a surrounding peripheral zone. The optic zone provides vision correction. The peripheral zone does not provide any vision correction, but the peripheral zone may provide other functions (e.g., helping to maintain the contact lens in place on the eye). The surface of the lens within the optic zone provides the first and second power maps, and thereby also provides the lens power map. Thus, the optic zone may optionally include the central, outer, and transition zones described above. The optic zone may also include one or more blending zones as previously described.

[0048] The diameter of the central zone may be less than 50% of the diameter of the portion, preferably less than 40%, and more preferably less than 30%. Thus, in contact lenses according to embodiments of the present invention, the diameter of the central zone may be less than 50%, preferably less than 40%, and more preferably less than 30% of the diameter of the optic zone of the contact lens. The central zone may be smaller than the minimum pupil size of the wearer of the contact lens. Embodiments of the present invention having a central zone that is smaller than the minimum pupil size of the wearer can maintain high-acuity near and distance vision in the presence of varying light conditions.

[0049] The focal power of the central zone may be substantially constant (e.g., the focal power may vary by less than 0.25 diopters (D) compared to the nominal focal power across the central zone). The central zone may have a lens power corresponding to distance vision. Contact lenses according to embodiments of the present invention in which the central zone has a substantially constant lens power corresponding to distance vision can provide high-acuity distance vision in bright light conditions when the pupil is at its smallest size. In bright light conditions, high-acuity distance vision is generally more useful to the wearer than high-acuity near vision, as such conditions generally correspond to daytime outdoor environments, where the wearer generally requires more distance vision than near vision. Alternatively, the central zone may have a lens power corresponding to near vision. Furthermore, the central zone may have a lens power that is more correct than the near vision correction power required by the lens wearer. For example, the focal power of the central zone may be +0.25D to +1.25D, which is more correct than the eye requires for near vision correction.

[0050] The lens may include a transition zone. The transition zone may surround the central zone. The outer zone may surround the transition zone. Thus, the transition zone may be positioned between the central and outer zones. The focal power of the transition zone may vary to provide a smooth transition between the central and outer zones. Embodiments of the present invention that provide a smooth transition between the central and outer zones may enable easier manufacture using a lathe for the lens, a mold for such a lens, or an insert for such a lens mold. Thus, skilled artisans will appreciate that smooth in this context means that the lens profile must be smooth enough to be produced using a lathe.

[0051] The spiral may be formed entirely on the first surface (i.e., the spiral is formed entirely by the first surface power map). Thus, the second surface power map may not vary periodically across a portion of the lens. Alternatively, the spiral may be formed entirely on the second surface (i.e., the spiral is formed entirely by the second surface power map). Thus, the first surface power map may not vary periodically across a portion of the lens. Alternatively, the spiral may be formed by both the first and second surfaces (i.e., the spiral is formed by the superposition of the first and second surface power maps). Contact lenses according to embodiments of the present invention in which the optic zone includes a spiral lens power map may provide a substantially constant ratio of the first lens power to the second lens power in the presence of varying through-aperture sizes.

[0052] It will be appreciated that either of the first surface power map and the second surface power map may have a substantially constant power of +0 D across the power map. For the purposes of this description, the surface of the lens is still considered to form a surface power map, even if the surface power map ultimately does not provide focus or vision modification.

[0053] The first surface power profile may vary radially and periodically outward from the center of the portion. The second surface power profile may vary substantially periodically outward from the center of the portion. The lens power profile may vary substantially periodically outward from the center of the portion. The period of radial variation of the surface may be greater than 100 microns, preferably greater than 200 microns, more preferably greater than 400 microns, and even more preferably greater than 800 microns.

[0054] The first surface power profile may vary substantially periodically in azimuth about the optical axis of the lens. The second surface power profile may vary substantially periodically in azimuth about the optical axis of the lens. The lens power profile may vary substantially periodically in azimuth about the optical axis of the lens. The period of the azimuth variation of the surface may be greater than 6 degrees, preferably greater than 9 degrees, more preferably greater than 18 degrees, and even more preferably greater than 36 degrees.

[0055] The period and phase of the radial and azimuthal variations of the second surface may be the same as the period of the radial and azimuthal variations of the first surface. It will be appreciated that the period of the azimuthal and radial variations of the first surface power map need not be the same as the period of the azimuthal and radial variations of the second surface power map. The first surface power map and / or the second surface power map may comprise a spiral, for example, a spiral having variations across a portion. The second surface power map may comprise a spiral that matches the spiral of the first surface power map. In such embodiments, the power map of the lens as a whole also comprises a spiral. Embodiments of the present invention that include contact lenses having a spiral lens power map can provide a substantially constant ratio of the first lens power to the second lens power in the presence of varying pupil sizes.

[0056] The helices provided by the first and second surfaces may twist in opposite directions. Thus, the first and second surface power maps can be said to include counter-rotating helices. The helices provided by the first and second surface power maps may be identical, but with opposite twist directions. Embodiments of the present invention in which the first and second surface power maps include counter-rotating helices can provide a lens power map that approximates a dartboard-like pattern of alternating annular rings. Those skilled in the art will appreciate that the lens optical power map is formed by superimposing the first and second surface power maps. Therefore, it will also be appreciated that the combination of the first and second surface power maps provides a pseudo-dartboard pattern, each of which retains the ease of manufacture advantages described previously. Consequently, such embodiments can enable easier manufacture of lenses with pseudo-dartboard power maps using a lathe.

[0057] The lens power map may include multiple segments. The segments in the multiple segments may provide a first focal power corresponding to distance vision or a second focal power corresponding to near vision. The segments may be arranged on the lens so that they alternate radially and / or azimuthally between the first and second focal powers. Thus, the first focal power may range from 0 diopters (D) to -10D. The first focal power may range from -0.25D to -6.00D. The second focal power provided in this lens may be more positive than the first focal power of the lens. For example, the second focal power may be 1D to 5D positive compared to the first focal power. The second focal power may be 1D to 4D positive compared to the first focal power. The second focal power may be 2D to 3D positive compared to the first focal power. The second focal power may vary, for example, by providing discrete segments with a defocus that is more positive than the first focal power, such that some of the segments may have a second focal power of +1D, some may have a second focal power of +2D, and some may have a second focal power of +3D. The change in the second power may occur within the same arm, or the change in the second power may occur in a different arm.

[0058] It is possible that at a predetermined radial distance from the center of the portion, the spiral changes its direction of rotation. Thus, a first segment of the lens may include a clockwise-rotating spiral, and a second segment of the lens may include a counterclockwise-rotating spiral. Such segments may be formed as concentric rings, for example, centered about the center of the portion. Lens segments having different rotational directions may be separated by intervening segments of substantially constant lens power. A lens may include more than one change in the direction of rotation of the spiral (e.g., each change in direction having an intervening segment of substantially constant lens power).

[0059] The multifocal lens may be a myopia control lens, and the multifocal lens may be configured to reduce myopia progression in a person whose eyes are able to accommodate. The multifocal lens may be suitable for providing vision correction, and the multifocal lens may be configured to provide distance vision correction and near vision correction to a person whose eyes are not able to adequately accommodate (e.g., a person 40 years of age or older).

[0060] Contact lenses according to the present invention may include ballast to orient the lens when positioned on the wearer's eye. This ballast may be provided by a peripheral zone of the contact lens. A contact lens may provide a particular benefit to the wearer in a given orientation. Embodiments of the present invention incorporating ballast into contact lenses, when placed on the wearer's eye, will rotate to a predetermined angle of repose under the action of the wearer's eyelid; for example, the ballast may be a wedge, and the rotation may result from the action of the eyelid on the wedge. By positioning the ballast in the contact lens, it is possible to ensure that the angle of repose corresponds to a lens orientation that provides a particular benefit to the wearer.

[0061] According to a second aspect, the present invention provides a method for manufacturing a multifocal ophthalmic lens (e.g., a contact lens). The method includes operating a lathe to shape a first surface of one of the following: a lens (e.g., a contact lens), a lens mold (e.g., a mold for a contact lens), or an insert for a mold for manufacturing a lens (e.g., an insert for a mold for a contact lens). The first surface is shaped to form a first surface power map. The method further includes operating a lathe to shape a second surface of the lens, mold, or insert. The second surface is shaped to form a second surface power map. The first and second surface powers Figure 1 The first surface power map, the second surface power map and / or the lens power map comprise a spiral having a variation across at least a portion of the lens, mold or insert.

[0062] The first surface may be shaped so that the surface power profile varies substantially periodically in azimuth from radially outwardly and around the center of the portion. The period of the radial variation may be greater than 100 microns. The period of the azimuth variation may be greater than 6 degrees.

[0063] The method may include operating a lathe to shape the surface of at least a portion of the lens. Alternatively or additionally, the method may include operating a lathe to shape the surface of at least a portion of a mold for the lens. Alternatively or additionally, the method may include operating a lathe to shape the surface of at least a portion of an insert for use in manufacturing a mold for the lens. As will be appreciated by those skilled in the art, the further an object formed by a lathe is removed from the lens, the less defined features will be reproduced on the resulting lens. Thus, for example, using a lathe to shape the surface of a lens enables more defined surface features to be achieved than would be achievable if a lathe were used to shape the surface of a mold for the lens.

[0064] The method further includes operating a lathe to shape a second surface of the portion of the lens, mold, or insert. The second surface may be shaped to vary across at least the portion to form a second surface power map comprising a spiral. The second surface may be shaped so that the second surface power map varies substantially periodically in azimuth from and around the center of the portion radially outward. The period of the radial variation may be greater than 100 microns. The period of the azimuth variation may be greater than 6 degrees. The second surface may be shaped so that the second surface power map varies as a mirror image of the first surface. The second surface may be shaped so that the spiral formed by the first surface power map twists in a direction opposite to the spiral formed by the second surface power map.

[0065] The lens may be a contact lens. In such embodiments, a portion of the lens may correspond to the optic zone of a contact lens. In such cases, it will be understood that reference to the optic zone of a mold or an insert of the mold refers to the portion of the mold that corresponds to the optic zone of a lens manufactured using the mold or insert.

[0066] Lenses (e.g., contact lenses) according to the present invention can be formed by a cast molding process, a spin casting molding process, or a turning process, or a combination thereof. As understood by those skilled in the art, cast molding refers to molding a contact lens by placing a lens-forming material between a female mold member having a concave lens-forming surface and a male mold member having a convex lens-forming surface.

[0067] In embodiments where the ophthalmic lens comprises a contact lens, the contact lens material is visually transparent (although it may include a treatment tint) when used as part of or as the entire contact lens. As understood in the art, the contact lens material may be a hydrogel material, a silicone hydrogel material, or a silicone elastomer material. In other words, the present contact lens may comprise, consist essentially of, or consist of a hydrogel material, a silicone hydrogel material, or a silicone elastomer material. As understood in the contact lens art, a hydrogel is a material that maintains water in equilibrium and is free of silicone-containing chemicals. A silicone hydrogel is a hydrogel containing silicone-containing chemicals. As used herein, hydrogel materials and silicone hydrogel materials have an equilibrium water content (EWC) of at least 10% to about 90% (wt / wt). A hydrogel material or silicone hydrogel material may have an EWC of from about 30% to about 70% (wt / wt). In contrast, silicone elastomer materials, as used herein, have a water content of from about 0% to less than 10% (wt / wt). Typically, silicone elastomeric materials used with the present methods or apparatus have a water content of from 0.1% to 3% (wt / wt). Alternatively, embodiments of the present contact lenses may be made from rigid gas permeable materials such as polymethylmethacrylate (PMMA) and the like.

[0068] The method may include the step of forming a contact lens in a molding assembly comprising a first mold part and a second mold part assembled together. In the case of a hydrogel lens or a silicone hydrogel lens, the lens can be made by polymerizing a hydrogel or silicone hydrogel lens formulation containing a polymerization initiator in a lens-shaped cavity formed between the first mold part and the second mold part. For a silicone elastomer lens, the lens can be made by curing, vulcanizing, or catalyzing (e.g., by hydrogenation) a liquid silicone elastomer in a lens-shaped cavity formed between the first mold part and the second mold part. The surface of each mold part forming the contact lens-shaped cavity can be convex, concave, planar, or a combination thereof. After the contact lens is formed, the two mold parts are separated so that the contact lens remains attached to the surface of one of the mold parts. Thus, the contact lens is provided on the surface of the first or second mold part. In some other embodiments, it may be desirable to place the lens on the surface of a mold part that is not used to produce the first lens component, but this may require additional steps to achieve the desired alignment of the component with the mold part. The lens can then be removed from the mold part to which it is attached and further processed, such as by extraction and hydration, and inspected and packaged in packaging and sterilized.

[0069] Figure 1A contact lens 10 according to an embodiment of the present invention is shown. Contact lens 10 includes an optic zone 11 and a peripheral zone 13. Optic zone 11 comprises the portion of the lens through which the wearer of the contact lens sees. Optic zone 11 forms a lens designed to provide vision correction to the wearer. Peripheral zone 13 surrounds optic zone 11 and does not provide any vision correction to the wearer. Peripheral zone 13 may perform other functions. For example, peripheral zone 13 may be used to help maintain the contact lens on the wearer's eye. Peripheral zone 13 may include ballast to maintain a predetermined orientation of the contact lens on the wearer's eye.

[0070] The two surfaces of the contact lens are shaped so that they vary across the optic zone 11 to form first and second surface power maps. Figure 1 Together they form a lens power map. Thus, it can be said that the viewing zone provides a first surface power map, a second surface power map, and a lens power map. Within the viewing zone, the power map may include one or more distinct regions. Figure 1 The example contact lens shown in FIG includes a central zone 15, an outer zone 17, and a transition zone 19. The outer zone 17 surrounds the transition zone 19. The transition zone 19 surrounds the central zone 15. The central zone 15 and the outer zone 17 can provide different lens power arrangements so that they provide different vision corrections. The transition zone 19 can be used to provide a smooth transition between the central zone 15 and the outer zone 17. It should be understood that Figure 1 The contact lenses described in the accompanying drawings are provided merely as examples, and other contact lenses according to the present invention may include more or fewer zones. For example, some contact lenses according to embodiments of the present invention may omit the transition zone, or some contact lenses may even include only a single zone that spans the entire optic zone 11. Other contact lenses according to embodiments of the present invention may include additional zones, for example, formed as concentric circles.

[0071] According to a first example embodiment of the present invention, a multifocal contact lens is provided. It should be understood that alternative embodiments may include an intraocular lens or a spectacle lens. The multifocal contact lens includes a first surface and a second surface. In this example embodiment, the first surface comprises the outer surface of the contact lens, and the second surface comprises the inner surface of the contact lens. Those skilled in the art will understand that the outer surface is the convex surface of the contact lens adjacent to the wearer's eyelid, and the inner surface is the concave surface of the contact lens adjacent to the wearer's eye.

[0072] A portion of a first surface is shaped to form a first surface power map. A corresponding portion of the lens (e.g., an opposite portion) is shaped to form a second surface power map. Thus, it can be said that a portion of the lens comprises first and second surfaces, forming respective first and second surface power maps. In this example embodiment, the portion corresponds to the optic zone of the contact lens. Thus, in this example embodiment, it can be said that the first surface of the optic zone forms the first surface power map, and the second surface of the optic zone forms the second surface power map. A skilled person will appreciate that the first surface power map shows the modification to the overall contact lens power map provided by the shape of the surface. Thus, a contact lens having two surfaces (an inner surface and an outer surface) comprises two surface power maps, which in combination determine the overall contact lens power map.

[0073] Figure 2 A first surface power diagram 100 is shown. The first surface power diagram 100 forms a spiral. The spiral varies across a portion, as explained in further detail below. The spiral includes a plurality (four in this example) of arms 101. Each of the arms 101 includes one of a peak arm 101a and a valley arm 101b. It should be understood that the peak arm 101a is the arm that contributes to the positive offset of the lens power, and the valley arm 101b is the arm that contributes to the negative offset of the lens power.

[0074] The spiral can be considered to be formed by the sum of multiple components. In this case, the multiple components include a first periodic component in the radial direction extending outward from the center of the segment and a second periodic component in the azimuthal direction around the center of the segment. In addition, the multiple components further include an offset in power that varies depending on the radial distance from the center of the segment. Thus, the spiral can be said to include a variation across the segment. In this example embodiment, the center of the segment is located on the optical axis of the lens. It will be understood that the optical axis of the lens is equivalent to the optical axis of the optic zone of the lens.

[0075] In this example embodiment, the offset varies across the portion from +0D at the inner portion of the portion to -3.0D at the outer portion of the portion. It will be appreciated that, in this example embodiment comprising a central and outer zone, the inner portion of the lens corresponds to the innermost portion of the outer zone. In this example embodiment, the offset varies linearly. In other embodiments, the offset may vary in other ways, such as exponentially and / or monotonically. The periodic component varies between +0D and +3.0D. It will be appreciated that the power at a given point of the first surface power map is determined by a combination of the offset and periodic components. Other embodiments of the present invention may include components other than simple offset and radial and azimuthal periodic components. It will be appreciated that in such embodiments, the entire surface power map is formed by the combination of all of the aforementioned components. Thus, in this example embodiment, the power of a point on the surface power map varies from -3.0D upwards to +3.0D across the portion. It will also be noted that, due to the offset in power, the variation in power depends on the location on the portion. Specifically, the focal power varies from -3.0D to +0D at the periphery of the portion, and from +0D to +3.0D at the interior of the portion. Thus, the multifocal contact lens of this example embodiment can be considered to have a base lens power that varies across the portion from +0D at the center of the portion to -3.0D at its periphery, and an add power of +3.0D provided by the periodic component. This contact lens may be suitable for patients who suffer from both myopia and presbyopia. The -3.0D base lens power is used to correct the wearer's distance vision, while the +3.0D add power is used to correct the wearer's near vision when adequate accommodation is not possible. Those skilled in the art will appreciate that the specific values provided for the first and second lens powers (and therefore the base and add powers) are purely examples, and that the actual values used in a given situation will be determined by the needs of the intended wearer.

[0076] In this example embodiment, the period of radial variation is 1.2 mm and the period of azimuthal variation is 90 degrees. However, it will be appreciated that other periods of radial and / or azimuthal variation may be used in alternative embodiments.

[0077] In this particular embodiment, the focal power varies smoothly across the first surface power map 100, varying generally sinusoidally in both the radial and azimuthal directions. Having the surface power map vary smoothly across a portion of the lens provides for ease of manufacture using a contact lens lathe or an apparatus for manufacturing contact lenses (e.g., a mold or an insert for a mold). However, in alternative embodiments, the focal power may vary according to other waveforms. For example, the focal power may vary as a square wave or as a circular square wave in one or both of the radial and azimuthal directions. Thus, in alternative embodiments, the focal power need not vary smoothly across a portion of the lens.

[0078] In this example embodiment, the positive and negative deviations of the periodic component are of equal length, such that it can be said to have a 50% duty cycle. Alternative embodiments include periodic components with other duty cycles. Thus, in such embodiments, the positive deviations can have different lengths than the negative deviations. Such embodiments can bias the periodic component toward a particular lens power, for example by providing a greater amount of the first lens power than the second lens power.

[0079] It will be appreciated that the width of the arms 101 of the spiral is determined, at least in part, by the ratio of the period of radial variation to the period of azimuthal variation. In this example embodiment, each arm 101 of the spiral is approximately 500 microns wide. It will be appreciated that alternative embodiments may incorporate arms 101 having different widths. It will also be appreciated that the width of an arm 101 is defined as its vertical width. In this embodiment, all arms of the spiral have equal width, however, in other embodiments, one or more arms of the spiral have a different width than other arms of the spiral.

[0080] Similarly, in this example embodiment, the periods of the first and second periodic components are each substantially constant across the portion. However, in alternative embodiments, the period of at least one of the first and second periodic components may vary as a function of one or both of the radial distance from the center of the portion and the azimuthal position about the center of the portion.

[0081] In alternative embodiments, the period of the second periodic component is less than 180°. Those skilled in the art will appreciate that the period of the second periodic component determines the number of arms 101 on the spiral. Thus, in such embodiments, the spiral includes at least two arms. It will also be appreciated that certain values of the period of the second periodic component, particularly those that are unit fractions of 360 degrees, may be particularly advantageous because they allow for surface power maps that do not have azimuthal discontinuities.

[0082] In this example embodiment, each arm 101 of the spiral twists through an angle of 270 degrees (or 0.75 of a rotation). In alternative embodiments of the present invention, each arm 101 of the spiral may twist between a quarter rotation (90 degrees) and 40 rotations. In this example embodiment, the arms of the spiral twist at a constant rate across the portion. Thus, it can be said that the arms have a constant twist rate. In other embodiments, the twist rate of the arms may vary across the portion.

[0083] In this particular embodiment, the first surface power map 100 includes a central zone 103 and an outer zone 105. The central zone 103 directly surrounds the optical axis of the contact lens. The outer zone 105 surrounds the central zone 103. The power of the central zone does not vary periodically across the central zone 103 and, for example, may be substantially constant across the central zone 103. The outer zone 105 comprises a spiral power map. In alternative embodiments of the present invention, each arm 101 of the spiral extends from the center of a portion of the lens to the periphery of the portion. Thus, such embodiments do not include distinct central and outer zones.

[0084] As mentioned previously, in this example embodiment, the portion of the lens corresponds to the optic zone of the contact lens. In this example embodiment, the central zone 103 has a diameter of 2 mm, which corresponds to 25% of the 8 mm diameter of the optic zone. The optic zone through which the wearer sees provides Figure 1 . The contact lens may further include a surrounding peripheral zone that does not provide additional focusing or vision correction and serves only to help maintain the contact lens in place on the wearer's eye. The diameter of the central zone may be less than 25% of the diameter of the optic zone. However, it will be appreciated that in alternative embodiments of the present invention, the diameter of the central zone 103 may take on other values. Similarly, it will be appreciated that the ratio of the diameter of the central zone 103 to the diameter of the optic zone may also take on other values. For example, the diameter of the central zone 103 may be less than 30% of the diameter of the optic zone.

[0085] Central zone 103 may be smaller than the minimum pupil size of the wearer of the contact lens. Such embodiments maintain multifocal vision even when the wearer's pupil is constricted to its minimum size. If central zone 103 is larger than the minimum pupil size, then when the wearer's pupil is constricted to its minimum size, only central zone 103 will be positioned across the wearer's entrance pupil. Because the focal power of central zone 103 does not vary like a spiral across central zone 103, the lens will not provide multifocal vision for any pupil size smaller than central zone 103.

[0086] Advantageously, in this example embodiment, central zone 103 provides a lens power corresponding to distance vision. Generally, brighter conditions correspond to outdoor environments. Therefore, a wearer's pupils are typically more constricted when outdoors than when indoors. Additionally, a wearer typically requires more distance vision when outdoors than when indoors. Having central zone 103 with a lens power corresponding to distance vision allows the contact lens to provide high-acuity distance vision even when the wearer's pupil is constricted to its smallest size.

[0087] This example embodiment further includes a transition zone 107. Transition zone 107 surrounds central zone 103. Outer zone 105 surrounds transition zone 107. The focal power of transition zone 107 varies to provide a smooth transition between central zone 103 and outer zone 105. It will be appreciated that this transition zone 107 is not required, and therefore alternative embodiments do not include transition zone 107. It will be appreciated that in this context, smooth is defined as sufficiently smooth so that the corresponding lens curvature can be reproduced by a lathe. In this example embodiment, the transition zone is approximately 300 microns wide. However, it will be appreciated that other widths of transition zones may also be used.

[0088] A skilled artisan will appreciate that the second surface of the portion of the contact lens (i.e., the second surface of the optic zone of the contact lens of this example embodiment) forms a second surface power map. In this example embodiment, the second surface power map does not vary periodically across the portion, thereby providing a substantially constant +OD power across the portion. Thus, the contact lens has a lens power map that matches the first surface power map. Consequently, the contact lens provides a reduced variation in the ratio of near focus to far focus as the wearer's pupil changes size.

[0089] While in this example embodiment, the first surface corresponds to the outer surface of the contact lens and the second surface corresponds to the inner surface of the contact lens, those skilled in the art will appreciate that in alternative embodiments, the first surface may correspond to the inner surface and the second surface may correspond to the outer surface. Thus, in embodiments, the inner surface includes a surface power map that forms a spiral, and the outer surface includes a surface power map that has a substantially constant power across the surface power map.

[0090] Figure 3 A second multifocal contact lens according to a second example embodiment of the present invention is shown. The contact lens includes a first surface power map 200 substantially as described with respect to the first embodiment, except for the following features. The first surface power map 200 of the second embodiment does not include a shift in power. Thus, it can be said that the first surface power map includes a base lens power that is substantially constant across the portion. Furthermore, the magnitude of the spiral varies across the portion with respect to the radial distance from the center of the portion. That is, the magnitude of each of the periodic components varies as a function of the radial distance from the center of the portion. In this example embodiment, the magnitude of the periodic components is at its maximum at the innermost portion of the outer zone and decays linearly with radial distance from the center of the portion. Thus, the spiral again includes a variation across the portion. The second surface power map 200 is identical to the second surface power map of the first embodiment. Thus, the lens power map matches the first surface power map 200.

[0091] A third example embodiment of the present invention provides a third multifocal contact lens. The third multifocal contact lens is generally as described with respect to the first embodiment, except for the following features. In this case, the offset in power is not provided by the first surface power map, but rather by the second surface power map. Thus, it can be said that the first surface power map comprises a spiral that does not include variations across the portion. However, the lens power map (formed by the combination of the first and second surface power maps) still comprises a spiral with variations across the portion, the variations being imparted by the offset in power provided by the second surface power map. Thus, the contact lens of this embodiment provides a lens power map that matches that of the first embodiment.

[0092] According to a fourth example embodiment of the present invention, a fourth multifocal contact lens is provided. The first surface power diagram of the fourth contact lens is identical to the surface power diagram of the contact lens of the second example embodiment. In this example, the second surface power diagram further comprises a spiral formed by the sum of a plurality of components. The plurality of components comprises a first periodic component in a radial direction extending outward from the center of the portion and a second periodic component in an azimuthal direction about the center of the portion. As with the first surface, the spiral comprises a plurality of arms, including peak arms and valley arms. In this example embodiment, the periodic components of the second surface power diagram are identical to the periodic components of the first surface power diagram. However, a skilled artisan will appreciate that alternative embodiments may incorporate periodic components of different periods on the second surface power diagram into one or both of the periodic components of the first surface power diagram. In this example embodiment, the second surface power diagram further comprises a central region, an outer region, and a transition region.

[0093] In this example embodiment, the spiral formed by the second surface power map twists in a direction opposite to the spiral formed by the first surface power map. Thus, in this particular embodiment, the spirals provided by the first and second surface power maps have opposite twist directions. In this example embodiment, the spirals formed on the first and second power maps are substantially identical, except for the opposite twist directions. The power map of the contact lens is determined by the superposition of the first and second surface power maps.

[0094] Figure 4 A lens power diagram 300 for a contact lens is shown. The superposition of two counter-rotating spirals formed by the first and second surface power diagrams produces a lens power diagram 300 that approximates a pseudo-dartboard pattern of alternating annular rings. The contact lens also provides a monotonic change in the ratio of the first lens power to the second lens power when the wearer's pupil constricts. Thus, the contact lens provides improved multifocal vision even in variable light conditions. Because both the first and second surface power diagrams include central, outer, and transition zones, the overall lens power diagram 300 for the contact lens also includes a central zone 303, an outer zone 305, and a transition zone 307.

[0095] According to a fifth embodiment of the present invention, a spectacle lens is provided. The spectacle lens includes a lens power diagram generally as described with respect to the first embodiment of the present invention. However, those skilled in the art will appreciate that the spectacle lens does not include an optic zone in the same sense as the contact lens of the first embodiment. In the case of a spectacle lens, typically, substantially all of the lens can be considered to be the optic zone of the lens. Those skilled in the art will further appreciate that the characteristics of the lens profile defined above with respect to the optic zone of a contact lens apply similarly to the portion of the spectacle lens of this embodiment. It will be appreciated that alternative embodiments of the present invention include spectacle lenses having surface power diagrams generally as described with respect to the second, third, and fourth embodiments of the present invention. Spectacle lens 700 includes a central zone 715, an outer zone 717, and a transition zone 719. In this example embodiment, the spiral formed by one or both of the first and second surface power diagrams does not extend to the leftmost edge of spectacle lens 717. Instead, the spiral extends only to dashed line 701. As the spiral extends outward to dashed line 701, the spiral may decay in magnitude (e.g., linearly) from the boundary between transition zone 719 and outer zone 717. In other embodiments, the spiral may have a substantially constant magnitude across the outer zone 717. In such embodiments, the eyeglass lens 700 may further include a narrow blending zone extending along the dashed line 701. It will be further appreciated that in other embodiments, the spiral continues outward to the edge of the eyeglass lens 700. In this example embodiment, the central zone 715 (and the surrounding transition zone 719 and outer zone 717) are not positioned in the geometric center of the eyeglass lens 700 and can be said to be offset from the geometric center of the eyeglass lens 700. A skilled artisan will appreciate that this offset can be used to position the central zone in the portion of the eyeglass lens 700 that is most frequently viewed by the wearer.

[0096] According to a sixth embodiment of the present invention, an intraocular lens is provided. The intraocular lens includes a helical power substantially as described with respect to the first embodiment of the present invention. It will be appreciated that alternative embodiments of the present invention include intraocular lenses having surface power diagrams substantially as described with respect to the second, third, and fourth embodiments of the present invention.

[0097] Figure 5 A flow chart illustrating the steps of a method 500 of manufacturing a lens (eg, a contact lens) according to a seventh embodiment of the present invention is shown.

[0098] The first step of method 500, represented by element 501, includes operating a lathe to shape a first surface of one of the following: a lens, a mold for a lens, or an insert for a mold for making a lens. The first surface is shaped so that the first surface varies across a portion of the lens (which may be, for example, an optic zone of a contact lens) to form a first surface power map.

[0099] The second step of method 500, represented by element 503, includes operating a lathe to shape a second surface of the portion. That is, the second step includes operating the lathe to shape a second surface of a corresponding (e.g., opposite) portion of one of the lens, a mold for the lens, or an insert for a mold for manufacturing a lens. The second surface is shaped so that the second surface varies across at least a portion of the lens to form a second surface power map.

[0100] First surface focal power diagram and second surface focal power diagram Figure 1 The first surface power map, the second surface power map, or the lens power map together form a lens power map. The first surface power map, the second surface power map, or the lens power map includes a spiral. The spiral varies across the portion.

[0101] The first surface power map may include a spiral. Alternatively, or additionally, the second surface power map may include a spiral. The lens power map may include a spiral (i.e., the spiral is formed by the combination of the first and second surface power maps). The second surface may be shaped as a mirror image of the first surface. Alternatively, the second surface may be shaped so that the spiral formed on the first surface power map twists in a direction opposite to the spiral formed on the second surface power map.

[0102] When the first surface (and the second surface where the second step 503 has been performed) is included on a mold for a lens or an insert for a mold for a lens, method 500 may include an optional third step, represented by element 505. Third step 505 includes manufacturing a lens using the mold for the insert for the mold for a lens.

[0103] Although the present invention has been described and illustrated with reference to specific embodiments, those skilled in the art will appreciate that the present invention is susceptible to many different variations not specifically described herein. By way of example only, certain possible variations will now be described.

[0104] In a first embodiment, a lens having a spiral lens power map is provided by a first surface power map of a contact lens comprising a spiral and a second surface power map of the contact lens having a substantially constant power across the surface power map. However, in an alternative embodiment, a lens having a spiral lens power map is provided by each of the first and second surface power maps comprising a spiral. In this embodiment, the period and phase of the periodic component of the second surface power map are identical to the period and phase of the periodic component of the first surface power map. Thus, the first and second surface power maps can be said to comprise mirror images of each other. Consequently, the first and second surface power maps are superimposed to form a single spiral power map, thereby forming a contact lens having a spiral lens power.

[0105] In all of the first, second, third, and fourth embodiments, the lens power diagrams of the contact lenses each include a central zone having a substantially constant power profile, an outer zone incorporating a spiral power profile, and a transition zone providing a smooth transition between the central and outer zones. However, some alternative embodiments do not incorporate a transition zone. Still other alternative embodiments do not incorporate distinct central and outer zones. Instead, in such embodiments, the spiral profile extends from the center of a portion of the lens all the way to the radial periphery of the portion.

[0106] In a first embodiment, the spiral formed by the first surface power map twists in a counterclockwise direction. However, in an alternative embodiment, the spiral formed by the first surface power map twists in a clockwise direction. In those embodiments in which mirrored spirals are formed on the first and second surface power maps, the spirals may rotate in either a clockwise or counterclockwise direction. Similarly, in a fourth embodiment, the spiral formed on the first surface power map twists in a counterclockwise direction, and the spiral formed on the second surface power map twists in a clockwise direction. However, in an alternative embodiment, the spiral formed on the first surface power map twists in a clockwise direction, and the spiral formed on the second surface power map twists in a counterclockwise direction.

[0107] In some embodiments of the present invention, a spiral formed in one or both of the first and second surface power maps changes its direction of rotation at a predetermined radial distance from the center of the portion. For example, the spiral may rotate in a clockwise direction between the center of the portion and the predetermined radial distance, and rotate in a counterclockwise direction beyond the predetermined radial distance. In some embodiments, the lens incorporates more than one change in the direction of rotation of the spiral. Thus, for example, the spiral may change from clockwise to counterclockwise rotation before resuming clockwise rotation again. A skilled artisan will appreciate that the lens may incorporate any number of changes in the direction of rotation of the spiral. It will also be appreciated that each of these changes in direction may occur at any selected radial distance from the center of the portion. Thus, the power map may include annular rings that alternate between clockwise and counterclockwise rotating spirals.

[0108] In some embodiments, between zones of an ophthalmic lens having different rotational directions, there are zones where the power diagram does not vary as a spiral. For example, the zones may have a substantially constant power. For example, from the center of the portion to a first radial distance, the lens (or surface) power diagram may vary as a clockwise spiral, followed by a zone of substantially constant power, and then as a counterclockwise spiral. Thus, the power diagram may appear to include a plurality of annular rings, for example alternating between a spiral and a substantially constant power, with the spiral zones also alternating between clockwise and counterclockwise rotations.

[0109] Similarly, in some embodiments, a spiral may be interrupted by one or more regions (e.g., rings) where the power diagram does not vary as much as a spiral. For example, the regions may have a substantially constant power. Thus, for example, the power diagram may include annular rings that alternate between a spiral and a substantially constant power. In such embodiments, the spiral may change its direction of rotation between each interruption, or it may continue its previous direction of rotation. Thus, the spiral may maintain a constant direction of rotation across the lens, but the spiral may be interrupted by regions of substantially constant lens power.

[0110] While embodiments of the present invention have been described above with respect to methods of manufacturing contact lenses, molds for contact lenses, or inserts for molds for contact lenses using a lathe, it will be appreciated that other manufacturing methods are possible. In particular, the molds or inserts may also be manufactured using additive manufacturing techniques, such as by 3D printing.

[0111] In the foregoing description, if reference is made to integers or elements having known, obvious or foreseeable equivalents, such equivalents are incorporated herein as if individually set forth. Reference should be made to the claims to determine the true scope of the present invention, which should be interpreted so as to encompass any such equivalents. The reader will also appreciate that integers or features of the present invention described as preferred, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Furthermore, it will be understood that such optional integers or features, while potentially beneficial in some embodiments of the present invention, may not be desirable in other embodiments and therefore may not exist.

Claims

1. A multifocal ophthalmic lens, wherein: The first surface of the lens is shaped to form a first surface power map; The 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 variation across at least a portion of the lens, the spiral having a first periodic component in a radial direction extending outward from a center of the portion and a second periodic component in an azimuthal direction about the center of the portion, the period of the second periodic component being substantially constant across the portion.

2. The multifocal ophthalmic lens according to claim 1, wherein: The first periodic component has a period greater than 100 microns; and The second periodic component has a period greater than 6 degrees.

3. The multifocal ophthalmic lens of claim 1 or 2, wherein the variation in the helix comprises a shift in power that varies as a function of radial distance from the center of the portion.

4. The multifocal ophthalmic lens of claim 1 or 2, wherein the peak power of one or more arms of the spiral varies as a function of one or both of: a radial distance from the center of the portion and an azimuthal position about the center of the portion.

5. The multifocal ophthalmic lens according to claim 1 or 2, wherein: The peak focal power of each arm of the spiral does not vary with radial distance from the center of the portion; and The peak power of at least one arm of the spiral is different from the peak power of the other arms.

6. The multifocal ophthalmic lens of claim 1 or 2, wherein each of the first surface power map and the second surface power map varies smoothly across the portion.

7. The multifocal ophthalmic lens according to claim 1 or 2, wherein: The portion of the lens includes a central region and an outer region, the outer region surrounding the central region; The lens power diagram in the outer region includes the spiral; and The lens power diagram does not vary periodically within the central region.

8. The multifocal ophthalmic lens of claim 7, wherein the central zone has a diameter that is less than 50% of the diameter of the portions.

9. The multifocal ophthalmic lens of claim 8, wherein: The lens includes a transition zone surrounding the central zone and the outer zone surrounding the transition zone; and The lens power map varies such that the transition zone provides a smooth transition between the central zone and the outer zones.

10. The multifocal ophthalmic lens of claim 1 or 2, wherein a twist rate of the helix varies as a function of radial distance from the center of the portion.

11. The multifocal ophthalmic lens of claim 1 or 2, wherein the width of one or more arms of the spiral is different from the corresponding width of other arms of the spiral.

12. The multifocal ophthalmic lens according to claim 11, wherein: At a predetermined radial distance from the center of the portion, the spiral changes its direction of rotation.

13. The multifocal ophthalmic lens of claim 1 or 2, 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 mold for a lens, or an insert for a mold for making a lens to form a first surface power map; operating a lathe to shape a second surface of the lens, mold, or insert to form a second surface power map; in: 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 variation across at least a portion of the lens, mold or insert, the spiral having a first periodic component in a radial direction extending outward from a center of the portion and a second periodic component in an azimuthal direction about the center of the portion, the period of the second periodic component being substantially constant across the portion.

15. A method of improving a person's vision, the method comprising: A multifocal ophthalmic lens according to any one of claims 1 to 13 is provided to a person in need of improved vision.

16. The multifocal ophthalmic lens of claim 1 or 2, wherein the ophthalmic lens is a center distance contact lens or a center near contact lens.

17. The multifocal ophthalmic lens of claim 7, wherein the central zone has an optical power corresponding to distance vision correction.

18. The multifocal ophthalmic lens of claim 7, wherein the central zone has an optical power corresponding to near vision correction.

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