CONTACT LENSES AND METHODS RELATING THERETO

A contact lens (301) and methods of manufacturing such a lens (301) are described. The lens (301) includes an optic zone (302). The optic zone (302) comprises a central region (305), the central region (305) having a first optical axis, a centre of curvature that is on the first optical axis, and a diameter that is less than 2.0 mm. The optic zone (302) comprises an annular region (303). The annular region (303) comprises a plurality of concentric treatment zones (303a, 303b), wherein each treatment zone (303a, 303b) has a radial sagittal power profile that increases with increasing radial distance from the optical axis.

TECHNICAL FIELD

The present invention relates to contact lenses. The present invention relates especially, but not exclusively, to contact lenses for slowing the progression of myopia. The present invention also relates especially, but not exclusively, to contact lenses for use by presbyopes. The present invention also relates to methods of manufacturing such lenses.

BACKGROUND

Many people, including children and adults require contact lenses to correct for myopia (short-sightedness) and many adults may require lenses to correct for presbyopia (an age-related inability to accommodate and hence inability to focus on near objects).

Uncorrected myopic eyes focus incoming light from distant objects to a location in front of the retina. Consequently, the light converges towards a plane in front of the retina and diverges towards, and is out of focus upon arrival at, the retina. Conventional lenses (e.g., spectacle lenses and contact lenses) for correcting myopia reduce the convergence (for contact lenses), or cause divergence (for spectacle lenses) of incoming light from distant objects before it reaches the eye, so that the location of the focus is shifted onto the retina.

The internal lenses of presbyopic eyes do not change shape to add the required power necessary to focus on near objects. Conventional lenses (e.g., spectacle lenses and contact lenses) for correcting presbyopia include the missing extra plus power in bifocal or progressive lenses, which include regions that are optimised for near vision and regions that are optimised for distance vision. Presbyopia may also be treated using bifocal or multifocal lenses, or monovision lenses (wherein different prescription are provided for each eye, one eye being provided with a distance vision lens, and one eye being provided with a near vision lens).

It was suggested several decades ago that progression of myopia in children or young people could be slowed or prevented by under-correcting, i.e., moving the focus towards but not quite onto the retina. However, that approach necessarily results in degraded distance vision compared with the vision obtained with a lens that fully corrects for myopia. Moreover, it is now regarded as doubtful that under-correction is effective in controlling developing myopia. A more recent approach to correct for myopia is to provide lenses having both one or more regions that provide full correction of distance vision and one or more regions that under-correct, or deliberately induce, myopic defocus. It has been suggested that this approach can prevent or slow down the development or progression of myopia in children or young people, whilst providing good distance vision.

In the case of lenses having regions that provide defocus, the regions that provide full-correction of distance vision are usually referred to as base power regions and the regions that provide under-correction or deliberately induce myopic defocus are usually referred to as myopic defocus regions or add power regions (because the dioptric power is more positive, or less negative, than the power of the distance regions). A surface (typically the anterior surface) of the add power region(s) has a smaller radius of curvature than that of the distance power region(s) and therefore provides a more positive or less negative power to the eye. The add power region(s) are designed to focus incoming parallel light (i.e., light from a distance) within the eye in front of the retina (i.e., closer to the lens), whilst the distance power region(s) are designed to focus light and form an image at the retina (i.e., further away from the lens).

A known type of contact lens that reduces the progression of myopia is a dual-focus contact lens, available under the name of MISIGHT (CooperVision, Inc.). This dual-focus lens is different than bifocal or multifocal contact lenses configured to improve the vision of presbyopes, in that the dual-focus lens is configured with certain optical dimensions to enable a person who is able to accommodate to use the distance correction (i.e., the base power) for viewing both distant objects and near objects. The treatment zones of the dual-focus lens that have the add power also provide a myopically defocused image at both distant and near viewing distances.

Whilst these lenses have been found to be beneficial in preventing or slowing down the development or progression of myopia, annular add power regions can give rise to unwanted visual side effects. Light that is focused by the annular add power regions in front of the retina diverges from the focus to form a defocused annulus at the retina. Under some circumstances, wearers of these lenses therefore may see a ring or ‘halo’ surrounding images that are formed on the retina, particularly for small bright objects such as street lights and car headlights. Also, rather than using the natural accommodation of the eye (i.e., the eye's natural ability to change focal length) to bring nearby objects into focus, in theory, wearers can make use of the additional focus in front of the retina that results from the annular add power region to focus near objects; in other words, wearers can inadvertently use the lenses in the same manner as presbyopia correction lenses are used, which is undesirable for young subjects and may compromise their ability to slow myopia progression by removing the myopically defocused light.

Further lenses have been developed which can be used in the treatment of myopia, and which are designed to eliminate the halo that is observed around focused distance images. In these lenses, the annular region is configured such that no single, on-axis image is formed in front of the retina, thereby preventing such an image from being used to avoid the need for the eye to accommodate near targets. Rather, distant point light sources are imaged by the annular region to a ring-shaped focal line at a near add power focal surface, preventing a useful image from being generated at this plane. The second advantage of this type of lens is that the rays forming the ring image can overlap when reaching the retina leading to a small spot size of light, without a surrounding ‘halo’ effect, on the retina.

For treating myopia, it is recognised that it may be beneficial to provide a lens that introduces additional myopic defocus. For treating presbyopia, it may be beneficial to provide a lens that gives rise to an extended depth of focus.

SUMMARY

According to a first aspect, the present disclosure provides a contact lens including an optic zone. The optic zone comprises a central region, the central region having a first optical axis, a centre of curvature that is on the first optical axis, and a diameter that is less than 2.0 mm. The optic zone comprises an annular region, wherein the annular region comprises a plurality of concentric treatment zones. Each treatment zone has a radial sagittal power profile that increases with increasing distance from the optical axis.

According to a second aspect, the present disclosure provides a method of manufacturing a lens. The method may comprise forming a contact lens. The contact lens includes an optic zone comprising a central region, the central region having a first optical axis, a centre of curvature that is on the first optical axis, and a diameter that is less than 2.0 mm. The optic zone comprises an annular region comprising a plurality of treatment zones, wherein each treatment zone has a radial sagittal power profile that increases with increasing radial distance from the optical axis.

It will of course be appreciated that features described in relation to one aspect of the present disclosure may be incorporated into other aspects of the present disclosure. For example, the method of the disclosure may incorporate features described with reference to the apparatus of the disclosure and vice versa.

DETAILED DESCRIPTION

According to a first aspect, the present disclosure provides a contact lens. The lens includes an optic zone comprising a central region, the central region having a first optical axis, a centre of curvature that is on the first optical axis, and a diameter that is less than 2.0 mm. The optic zone comprises an annular region, wherein the annular region comprises a plurality of concentric treatment zones. Each treatment zone has a radial sagittal power profile that increases with increasing radial distance from the optical axis.

As used herein, the term contact lens refers to an ophthalmic lens that can be placed onto the anterior surface of the eye. It will be appreciated that such a contact lens will provide clinically acceptable on-eye movement and not bind to the eye or eyes of a person. The contact lens may be in the form of a corneal lens (e.g., a lens that rests on the cornea of the eye). The contact lens may be a soft contact lens, such as a hydrogel contact lens or a silicone hydrogel contact lens. The lens may be a lens for use in preventing or slowing the development or progression of myopia. The lens may be a lens for use in providing an extended depth of focus to a presbyopic eye.

A contact lens according to the present disclosure comprises an optic zone. The optic zone encompasses the parts of the lens that have optical functionality. The optic zone is configured to be positioned over the pupil of an eye when in use. For contact lenses according to the present disclosure, the optic zone comprises a small central region, and an annular region that surrounds the central region. The optic zone may be surrounded by a peripheral zone. The peripheral zone is not part of the optic zone, but sits outside the optic zone and above the iris when the lens is worn, and it provides mechanical functions, for example, increasing the size of the lens thereby making the lens easier to handle, providing ballasting to prevent rotation of the lens, and/or providing a shaped region that improves comfort for the lens wearer. The peripheral zone may extend to the edge of the contact lens.

A contact lens according to an embodiment of the disclosure may include a ballast to orient the lens when positioned on the eye of a wearer. Embodiments of the disclosure incorporating a ballast into the contact lens will, when placed on the eye of a wearer, rotate under the action of the wearer's eyelid to a pre-determined angle of repose; for example, the ballast may be a wedge and the rotation may result from the action of the eyelid on the wedge. It is well-known in the art to ballast a contact lens to orient a contact lens; for example, toric contact lenses are ballasted to orient the lens so that the orthogonal cylindrical corrections provided by the lens align correctly for the astigmatism of the wearer's eye.

The contact lens may be substantially circular in shape and have a diameter from about 4 mm to about 20 mm. The optic zone may be substantially circular in shape and may have a diameter from about 2 mm to about 10 mm. In some embodiments, the contact lens has a diameter from 13 mm to 15 mm, and the optic zone has a diameter from 7 mm to 9 mm.

The first optic axis may lie along the centreline of the lens. The central region may have a substantially circular shape. The central region may have a substantially oval or elliptical shape. The central region has a small diameter of less than 2.0 mm. The central region may have a diameter of less than 1 mm, less than 0.5 mm, or less than 0.25 mm. If the central region is substantially elliptical or oval in shape, the maximum diameter may be less than 2.0 mm, less than 1.0 mm or less than 0.5 mm, or less than 0.25 mm.

The annular region may extend radially outwards from a perimeter of the central region. The perimeter of the central region may define a boundary between the central region and the annular region, and the annular region may therefore be adjacent to the central region. The annular region may be a substantially annular region that surrounds the optic zone. It may have a substantially circular shape or a substantially elliptical shape. It may fully surround the optic zone. It may partially surround the optical zone.

The annular region comprises a plurality of concentric treatment zones. The annular region may comprise between 2 and 10 concentric treatment zones, preferably between 4 and 8 concentric treatment zones. Each treatment zone may have a radial width of between about 0.1 and 2.5 mm, preferably between about 0.2 and 1.2 mm, more preferably between about 0.3 and 1.0 mm. Each treatment zone may have the same radial width. The treatment zones may have different radial widths.

Each treatment zone may directly abut an adjacent treatment zone, i.e., an outer perimeter of a first treatment zone may define a boundary between the first treatment zone and a second treatment zone. The second treatment zone may therefore be adjacent to the first treatment zone.

In the context of the present disclosure, the power of the central region and the treatment zones of the lens can be defined as radial curvature power, a circumferential curvature power, a radial sagittal power, and a circumferential sagittal power.

The curvature and sagittal powers of the lens are defined as follows:

For a wavefront W, at a point a radial distance r (pupil radius) from a line normal to the centre of the wavefront, W(r)=A*r2, where A is a function.

The wavefront curvature or curvature power, Pc, is a function of the second derivative of the wavefront. The wavefront slope, or slope-based or sagittal power PS, is a function of the first derivative of the wavefront and varies with the slope of the wavefront.

and for a simple spherical lens,

and for a simple spherical lens

For a simple co-axial lens with spherical wavefront, with paraxial assumptions, PC=PS.

The radial curvature power is the curvature power in a direction extending radially outward from the optical axis of the lens. The circumferential curvature power is the curvature power at a constant radial coordinate, extending around the circumference of the lens.

The radial sagittal power is the sagittal power in a direction extending radially outward from the optical axis of the lens. The circumferential sagittal power is the sagittal power at a constant radial coordinate, extending around the circumference of the lens.

The curvature power and the sagittal power of the lens can be determined using optical design software. For example, the radial curvature power can be determined by analyzing the effect of the contact lens on a wavefront of light transmitted through the lens. An example of optical design software is available from ZEMAX (Washington, USA) under the name of Optical Design Studio.

In embodiments of the present disclosure, each treatment zone is radially tilted relative to the central zone. As a result, each treatment zone has a radial sagittal power profile that increases with increasing radial distance from the optical axis. The radial sagittal power profile of the central region may be approximately flat. Alternatively, the radial sagittal power profile across the central region may have a curved profile. The radial sagittal power profile across the central region may have a quadratic or parabolic shape. As used herein, the tilting of the treatment zones means radial tilting rather than lateral tilting. Thus, for example, in a radial cross section of the lens, an outer end of an arc defining the anterior surface of the first annular region may be displaced above or below its position in a corresponding un-tilted treatment zone. Correspondingly, in three dimensions, a circumferential boundary (formed by the ends of the radial arcs) of the treatment zones may be displaced above or below its position in a corresponding un-tilted treatment zone. In practice, the tilting may be embodied in the optical design of an anterior surface of the treatment zones of the lens. The tilting may alternatively be embodied in the optical design of a posterior surface of the treatment zones of the lens, or embodied in the optical design of both anterior and posterior surfaces of the treatment zones of the lens.

Radially tilting a treatment zone relative to the central zone shifts the centre of curvature of that treatment zone away from the optical axis. A larger radial tilt relative to the central region will give rise to a greater shift in the centre of curvature of the treatment zone, and a steeper gradient of the radial sagittal power profile. Light rays from a distant point source passing through a radially tilted treatment zone will not focus towards a single point on the optical axis, but instead, will focus towards an off-axis point. For an annular treatment zone having a constant radial sagittal power, light rays from a distant point source passing through a radially tilted treatment zone will form an annular ring at a focal surface. The diameter of the annular ring will depend, in part, on the tilt of the treatment zone relative to the central region. The diameter of the annular ring will also be dependent upon the radial distance of the treatment zone from the optical axis, and the radial add power of the treatment zone.

In a lens having concentric annular regions that provide focusing, light can be considered to be “focused” by the annular regions in two different ways.

In a first form of focusing, light is focused by the local curvature of the annular region. Considering a transverse 2D cross-section through the lens, and in the approximation of geometric optics, adjacent rays passing through the radial width of the annular region (i.e. through a single “side” of the annulus, i.e. through a portion of a radius between the inner circumference of the annular region and the outer circumference of the annular region) from a distant source are focused by the local curvature of the annular region to a point; and the points from each of the radial widths around the annulus together form a ring of focal points around the optic axis of the lens. This local focusing, resulting from the local curvature within the radial width of the annular region, is referred to herein as focusing and the surface containing the focal ring is referred to as a focal surface. The curvature power of the annular region depends on the degree of (local) focusing.

In a second form of focusing, light can be focused by the global curvature of one or more of the annuli taken together. Considering again a transverse 2D cross-section through the lens, and in the approximation of geometric optics, a light ray from a distant source that passes through the midpoint of the radial width of the annular region travels in a direction determined by the radial position of the annulus on the lens and the radial “tilt” of the annular region. The tilt can be selected to ensure that light rays passing through the midpoints of the radial width on opposite “sides” of the annulus converge to a point on the optic axis. When the lens includes a plurality of the annuli, the rays passing through the midpoints of the radial widths of all of the annuli can converge to the same point. The rays passing through the whole of the annulus (and not just the midpoints) can converge to a small spot at this point. In order to more clearly distinguish it from the first form of focusing, this global focusing, resulting from the curvature of the lens and the radial tilt of the annuli, is referred to herein as convergence and the surface containing the point to which the midpoints converge is referred to as a convergence surface. The sagittal power of the annular region depends on the degree of (global) convergence.

The terms focal surface and convergence surface, as used herein, do not refer to physical surfaces, but to surfaces that could be drawn through points where light from distant objects would be focused or reach a locally minimal spot size. The eye focuses light onto the retina, which is curved, and in a perfectly focused eye, the curvature of the surface would match the curvature of the retina, therefore the eye does not focus light onto a flat mathematical plane. However, in the art, the curved surface of the retina is commonly referred to as a plane.

In embodiments of the present disclosure, at least two of the treatment zones may have different radial sagittal power profiles. At the boundary between the central zone and a first, innermost annular zone there may be a change in gradient of the radial sagittal power profile. At the boundary between adjacent treatment zones there may be a change in gradient of the radial sagittal power. The annular region may comprise between 2 and 10 concentric treatment zones, preferably between 4 and 8 concentric treatment zones. Each treatment zone may have a different radial sagittal power profile. Alternatively, alternate treatment zones may have the same radial sagittal power profile. The radial sagittal power profile of each treatment zone may have a gradient of between about 0.5 D/mm and about 20.0 D/mm, preferably between about 0.5 D/mm and about 10.0 D/mm, more preferably between about 1.0 D/mm and about 5.0 D/mm. A first, innermost treatment zone (i.e., closest to the central region), may have a first radial sagittal power profile gradient. A second, adjacent treatment zone may have a second, different radial sagittal power profile gradient, and a third treatment zone adjacent to the second treatment zone may have the same radial sagittal power profile gradient as the first treatment zone.

Radially tilting a treatment zone relative to the central region alters the radial sagittal power profile of that treatment zone, as this is a function of the first derivative of the wavefront, but it will not alter the radial curvature power of that treatment zone, which is a function of the second derivative of the wavefront.

For lenses according to embodiments of the present disclosure, the central region may have a substantially flat radial sagittal power profile. The radial sagittal power of the central region will be equal to the radial curvature power of the central region. This may hereafter be referred to as the base power of the central region. The radial sagittal power across the central region may have curved profile. The radial sagittal power profile across the central region may have a parabolic or quadratic shape.

Lenses according to embodiments of the present disclosure will have a nominal distance power (typically the power that is written on the contact lens packaging). The nominal distance power of the lens depends upon the position of a best distal focal surface, and this is dependent upon the path of light rays from distant point sources that pass through the treatment zones. As discussed above, light rays from a distant point source that pass through the midpoint of the radial width of each treatment zone (i.e. halfway across the radial width of each treatment zone) converge to a point centred on the optical axis and contained in a convergence surface. To a first approximation, a best distal focal surface may be defined as the convergence surface where the spot size of light passing through the radial width of each treatment zone is at its smallest. The position of this best distal focal surface determines the nominal distance power of the lens.

For lenses used in the treatment of myopia, the nominal distance power of the lens will be negative or close to zero. The nominal distance power may be between +0.5 diopters (D) and −15.0 D. The nominal distance power may be between −0.25 D to −15.0 D.

For lenses according to embodiments of the present disclosure, the central region may have a base power that is approximately equal to the nominal distance power. The central region may have a base power that is less than (i.e., less positive, or more negative) than the nominal distance power. The central region may have a radial sagittal power that varies with a curved profile. The average radial sagittal power across the central region may be approximately equal to the nominal distance power, or may be less than (i.e., less positive or more negative) than the nominal distance power. The average radial sagittal power across the central region may be more than (i.e., more positive or less negative) than the nominal distance power.

For lenses according to embodiments of the present disclosure, at least one treatment zone may have a radial curvature power that is greater than the nominal distance power of the lens. Each treatment zone may have a radial curvature power that is greater than the nominal distance power of the lens. Each treatment zone may therefore provide a radial curvature add power. Hereafter, the difference in radial curvature power of each treatment zone and the nominal distance power may be referred to as a radial curvature add power, or a curvature add power.

Increasing the radius of curvature of a treatment zone will alter the radial curvature power of that treatment zone, as this is a function of the second derivative of the wavefront. The radial curvature power of each treatment zone may be determined by the curvature of at least one surface of the annular region. The radial curvature power of each treatment zone may result from the curvature of an anterior surface and/or a posterior surface of the lens. Each treatment zone may have a greater curvature, or a smaller radius of curvature, than the central region. The anterior surface of each treatment zone may have a greater curvature, or smaller radius of curvature than the curvature of the central region. Alternatively, or additionally, the posterior surface of each treatment zone may have a greater curvature than the curvature of the central region.

The nominal distance power of the lens may be positive, and each treatment zone may have a curvature power that is more positive than the nominal distance power. In this case, light from a distant point source passing through each treatment zone will be focused towards an add power focal surface that is closer to the lens than the distal focal surface.

The nominal distance power of the lens may be negative, and each treatment zone may have a curvature power that is less negative than the nominal distance power, or each treatment zone may have a positive curvature power. Considering the lens positioned on the cornea, if the curvature power of a treatment zone is less negative than the base power, light from a distant point source passing through that treatment zone will be focused towards an add power focal surface that is more anterior in the eye than the distal focal surface. Considering the lens when it is not positioned on the cornea, if the curvature power of a treatment zone is positive, an add power focal surface will be on the opposite (image) side of the lens than the distal focal surface (which will be a virtual focal surface on the object side of the lens); if the curvature power of a treatment zone is negative (but less negative than the nominal distance power), a virtual add power focal surface will be further from the lens than a virtual distal focal surface.

For lenses according to embodiments of the present disclosure, the radial curvature power of the central region may be equal to, or approximately equal to, the nominal distance power. In this case, when the lens is on an eye, light from a distant point source passing through the central region may be focused to a spot on the first optical axis at a distal focal surface. Alternatively, the central region may have a radial curvature add power that is less than the nominal distance power. In this case, when the lens is on an eye, light from a distant point source passing through the central region may be focused to a spot on the first optical axis that is closer to the lens than the distal focal surface.

A first, innermost treatment zone may have a first radial curvature power value that is greater (i.e., more positive or less negative) than the nominal distance power. When the lens is positioned on an eye, a first, innermost, treatment zone may focus light from a distant point source towards a focal surface that is closer to the lens than the distal focal surface.

Each treatment zone may have a different radial curvature add power. The radial curvature power a first, innermost treatment zone may have a first value, and the radial curvature power of an adjacent, second treatment zone, positioned at a greater radial distance from the first optical axis may have a second, greater value. This may improve vision for a lens wearer. Alternatively, a second treatment zone, positioned at a greater radial distance from the first optical axis may have a second, smaller value. A first, innermost treatment zone may have a radial curvature add power of between +0.5 D and +20.0 D, preferably between about +2.0 and +10.0 D, more preferably between about +1.0 D and +5.0 D. A second, adjacent treatment zone may have a greater radial curvature add power of between +0.5 D and +20.0 D, preferably between +4.0 D and +20.0 D. The radial curvature add power of the treatment zones may alternate between a high radial curvature add power value, and a low radial curvature add power value, the high radial curvature power being greater than the nominal distance power of the lens. The high radial curvature add power value and the low radial curvature add power value may both be greater than the nominal distance power of the lens. The high radial curvature add power may be between +4.0 D and +20.0 D. The low radial curvature add power may be between +1.0 D and +5.0 D. For a lens on an eye, high radial curvature add power treatment zones will focus light from a distant point source towards the near focal surface that is closer to the lens than the distal focal surface. Low radial curvature add power treatment zones may focus light from a distant point source towards a middle focal surface that lies in between the near focal surface and the distal focal surface.

Alternatively, each treatment zone may have the same radial curvature add power. The radial curvature add power of each treatment zone may be greater than the nominal distance power.

At the boundaries between adjacent treatment zones, there may be a sharp, discontinuous increase or decrease in radial curvature power, depending upon the relative radial curvature add powers of the treatment zones

At the boundaries between adjacent treatment zones, there may be a sharp, discontinuous increase or decrease in radial sagittal power. At a point halfway across the radial width of a first, innermost treatment zone, the radial sagittal power may match the nominal distance power of the lens. At a point halfway across the radial width of any or all of the treatment zones, the radial sagittal power may match the nominal distance power of the lens.

The radial sagittal power may be the same at a point halfway across the width of each treatment zone.

At any of the boundaries between adjacent treatment zones there may be a sharp increase in radial sagittal power. The radial sagittal power at a point halfway across the radial width of each treatment zone will be less than the radial curvature power of that treatment zone. At least one treatment zone may be a sagittal add treatment zone, having a radial sagittal power that is greater than the nominal distance power of the lens across the width of that treatment zone. For each treatment zone, the radial curvature power may be greater than the radial sagittal power across the width of the treatment zone. Sagittal add treatment zones are radially tilted in a manner such that the radial sagittal power is greater than the nominal distance power of the lens across the width of that treatment zone. The radial sagittal power across the width of a sagittal add treatment zone will be less than it would be for a co-axial, or on-axis treatment zone having the same radial curvature add power. For these treatment zones, light from a distant point source passing through the radial midpoint of the treatment zone will be focused towards a sagittal add power focal surface. For a lens on an eye, the sagittal add power focal surface will be closer to the lens than the distal focal surface for that lens.

The contact lens may comprise an elastomer material, a silicone elastomer material, a hydrogel material, or a silicone hydrogel material, or combinations thereof. As understood in the field of contact lenses, a hydrogel is a material that retains water in an equilibrium state and is free of a silicone-containing chemical. A silicone hydrogel is a hydrogel that includes a silicone-containing chemical. Hydrogel materials and silicone hydrogel materials, as described in the context of the present disclosure, have an equilibrium water content (EWC) of at least 10% to about 90% (wt/wt). In some embodiments, the hydrogel material or silicone hydrogel material has an EWC from about 30% to about 70% (wt/wt). In comparison, a silicone elastomer material, as described in the context of the present disclosure, has a water content from about 0% to less than 10% (wt/wt). Typically, the silicone elastomer materials used with the present methods or apparatus have a water content from 0.1% to 3% (wt/wt). Examples of suitable lens formulations include those having the following United States Adopted Names (USANs): methafilcon A, ocufilcon A, ocufilcon B, ocufilcon C, ocufilcon D, omafilcon A, omafilcon B, comfilcon A, enfilcon A, stenfilcon A, fanfilcon A, etafilcon A, senofilcon A, senofilcon B, senofilcon C, narafilcon A, narafilcon B, balafilcon A, samfilcon A, lotrafilcon A, lotrafilcon B, somofilcon A, riofilcon A, delefilcon A, verofilcon A, kalifilcon A, and the like.

Alternatively, the lens may comprise, consist essentially of, or consist of a silicone elastomer material. For example, the lens may comprise, consist essentially of, or consist of a silicone elastomer material having a Shore A hardness from 3 to 50. The shore A hardness can be determined using conventional methods, as understood by persons of ordinary skill in the art (for example, using a method DIN 53505). Other silicone elastomer materials can be obtained from NuSil Technology or Dow Chemical Company, for example.

According to a second aspect, the present disclosure provides a method of manufacturing a lens. The method may comprise forming a contact lens. The contact lens includes an optic zone comprising a central region, the central region having a first optical axis, a base radial sagittal power, a centre of curvature that is on the first optical axis, and a diameter that is less than 2.0 mm. The optic zone comprises an annular region comprising a plurality of treatment zones, wherein each treatment zone has a radial sagittal power profile that increases with increasing radial distance from the optical axis.

The lens may include any of the features set out above in respect of the first aspect of the invention.

The method of manufacturing may comprise forming a female mold member with a concave lens forming surface and a male mold member with a convex lens forming surface. The method may comprise filling a gap between the female and male mold members with bulk lens material. The method may further comprise curing the bulk lens material to forms the lens.

The contact lens may be a formed using a lathing process. The lens can be formed by cast molding processes, spin cast molding processes, or lathing processes, or a combination thereof. As understood by persons skilled in the art, cast molding refers to the molding of a lens by placing a lens forming material between a female mold member having a concave lens member forming surface, and a male mold member having a convex lens member forming surface.

FIG.1Ashows a schematic top view of a prior art lens for use in the slowing progression of myopia (e.g., myopia control).FIG.1Bshows a schematic cross-sectional side view of the lens ofFIG.1A. The lens1comprises an optic zone2, which approximately covers the pupil, and a peripheral zone4that sits over the iris. The peripheral zone4provides mechanical functions, including increasing the size of the lens thereby making the lens1easier to handle, providing ballasting to prevent rotation of the lens1, and providing a shaped region that improves comfort for the lens1wearer. The optic zone2provides the optical functionality of the lens1, and the optic zone2comprises an annular region3and a central region5. For this lens1, the central region5has a base curvature power that corresponds to the distance power of the lens1. The annular region3has a greater radial curvature power than the base curvature power of the central region5.FIG.2Ais a schematic ray diagram showing how the lens1ofFIGS.1A-1Bfocuses light when the lens is positioned on an eye. The focus11of the annular region3lies on a proximal focal surface13, and the focus15for the central region5lies on a distal focal surface17, which is further away from the posterior surface of the lens1. The focus11of the annular region3and the focus15of the central region5share a common optical axis19. As shown inFIGS.2A and2C, for a point source at infinity, light rays focused by the central region5form a focused image23at the distal focal surface17. As shown inFIGS.2A and2B, light rays focused by the central region5also produce an unfocused blur spot27at the proximal focal surface13.

As shown inFIGS.2A and2B, light rays focused by the annular region3form a focused, on-axis image21at the proximal focal surface13. Light rays focused by the annular region3diverge after the proximal focal surface13, and, as shown inFIGS.2A and2C, the diverging light rays produce an unfocused annulus25at the distal focal surface17. As discussed above, the unfocused annulus25image may result in wearers of the lens seeing a ‘halo’ around focused distance images. The annular region3of the lens1ofFIGS.1A-2Cmay be referred to as a co-axial annular region3, because light rays from a distant point source passing through the annular region3are focused to a spot on the optical axis19.

FIGS.3A and3Bshows a schematic top view of another known lens101. Similar to the lens1shown inFIGS.1A and1Bthe lens101comprises an optic zone102and a peripheral zone104surrounding the optic zone102. The optic zone102comprises a central region105and a first annular region103that surrounds the central region105. As shown inFIGS.4A and4D, the central region105has a centre of curvature that is on an optical axis119. The first annular region103is radially tilted relative to the central region105, and the first annular region103has an off-axis centre of curvature that is a first distance from the optical axis119. The anterior surface of the first annular region103has a greater curvature than the anterior surface of the central region105, and therefore provides a greater curvature power than the base curvature power of the central region105.FIG.4Dis a partial ray diagram for the lens101ofFIGS.3A-B, when the lens101is positioned on an eye, together with circles indicating the radii of curvature of the central distance region (solid circle) and the annular add region (dashed circle) of the lens101. As shown inFIG.4D, the anterior surface of the central region105defines a portion of a surface of a sphere of larger radius109. The anterior surface of the annular region103defines a curved annular surface with smaller radius106.

FIGS.4A and4Cshows a light pattern at a distal focal surface117of the lens ofFIGS.3A-Bformed from a distant point source, when the lens101is positioned on an eye. At the distal focal surface117light rays passing through the central region105are focused. Light rays passing through the midpoints of the width of the annular region103converge at the same point as the light rays passing though the central region105are focused. The annular region103acts as an optical beam stop, which leads to a small spot133of light at the distal focal surface117.

FIG.4Bshows a light pattern at a proximal focal surface113of the lens101ofFIGS.3A-Bformed from a distant point source, when the lens101is positioned on an eye. A single image is not formed at the proximal focal surface113. At the proximal focal surface113, for a point source at infinity, light rays passing through the central region105generate a blur circle128. However, light rays from a distant point source passing through the annular region103generate an annular ring122, as shown inFIG.4B, which surrounds the blur circle128.FIG.4Bshows the light pattern generated for a distant point source.

In contrast to the lens1ofFIGS.1A and1B, the lens101ofFIGS.2A and2Bdoes not generate a single image or an on-axis image at the proximal focal surface113that could be used to avoid the need for the eye to accommodate for near objects. For an extended object at distance, the image formed at the proximal focal surface113is a convolution of (i) the focused image of the extended object that would be obtained with a conventional lens having the optical power of the annular region and (ii) an optical transfer function representing the optical effect of the annular region103.

In contrast to the prior art lens ofFIGS.1A and1B, an annulus or ‘halo’ effect does not occur at the distal focal surface117. The annular region103of the lens101ofFIG.3A-Bmay be referred to as a non-coaxial annular region103, or an off-axis annular region103, because light rays from a distant point source passing through the annular region103are not focused at a spot on the optical axis119.

FIG.5Ashows a comparison between a radial sagittal power profile231(dashed line) of a lens having two co-axial, or on-axis add power annular regions spanning widths203,203′ (i.e., annular regions that focus light from a distant point source towards a spot on the optical axis), and a radial sagittal power profile233(solid line) of a lens having two non-coaxial or off-axis add power annular regions, spanning widths203,203′ (i.e. annular regions that do not focus light towards a spot on the optical axis).FIG.5Bshows a corresponding comparison of a radial curvature profile232(dashed line) of a lens having two co-axial add power annular regions spanning widths203and203′, and a radial curvature power profile234(solid line) of a lens having two non-coaxial add power annular regions spanning widths203,203′. The radial sagittal power and radial curvature power in Dioptres (D) is plotted as a function of radial distance from the centre of the lenses (r=0). Both lenses have a flat radial sagittal profile and radial curvature power spanning a central region205. At the boundary of the central region205and the first annular region203, for the on-axis, or co-axial lens, there is a sharp increase in the radial sagittal power231and a sharp increase in the radial curvature power232; the radial sagittal power profile231and radial curvature power profile232are constant across the width of the annular region203. At the boundary of the central region205and the annular region203, for the non-coaxial lens, there is a sharp increase in radial curvature power234, but a sharp decrease in the radial sagittal power233. The radial sagittal power233increases with a constant gradient across the radial width of the annular region203for the non-coaxial lens, as a result of the radial tilting of the annular region relative to the central region. At a point halfway across the width of the annular region203for the non-coaxial lens, the radial sagittal power233matches the radial sagittal power233across the central region205, which corresponds to the distance power of the lens in this case. Both lenses have a second annular region positioned at a greater radial distance from the centre of the lens. Both lenses have the same radial curvature power232,234across both annular regions203,203′. For the co-axial lens the radial sagittal power231across the width203′ of the second annular region is substantially identical to the radial sagittal power231across the first annular region203. For the non-coaxial lens, less radial sagittal add power is required to achieve the same radial curvature power, and so the gradient of the radial sagittal power profile233across the second annular region203′ is less than the gradient across the first annular region203. Both lenses have a distance power region207that has a substantially flat radial sagittal power profile231,233and substantially flat radial curvature power profile232,234, in between the first203and second203′ annular regions. The radial curvature power232,234across the distance power region207matches the radial curvature power232,234across the central region205.

FIG.6Ashows a schematic top view of a lens301according to an embodiment of the present disclosure.FIG.6Bshows a schematic cross-sectional view of the lens301ofFIG.6A. The lens301comprises an optic zone302, which approximately covers the pupil, and a peripheral zone304that sits over the iris. The peripheral zone304provides mechanical functions, including increasing the size of the lens thereby making the lens301easier to handle, providing ballasting to prevent rotation of the lens301, and providing a shaped region that improves comfort for the lens301wearer. The optic zone302provides the optical functionality of the lens301. The optic zone302comprises a small central region305having a diameter of 0.5 mm, and an annular region303surrounding the central region305. The annular region303comprises two concentric treatment zones303a,303b. Each treatment zone303a,303bis radially tilted relative to the central zone305. Each treatment zone303a,303bprovides a radial curvature add power. For this lens301, the radial curvature add power results from a greater curvature of the anterior surface of the lens301. The inner treatment zone303a, has a low radial curvature add power, and the outer treatment zone303bhas a high radial curvature add power.

FIG.7shows the radial sagittal power profile331and the radial curvature power profile332taken along a radial diameter of the lens301shown inFIGS.6A and6B. Across the width of the central region305, the radial sagittal power profile331is flat. Across the width of the central region305, the radial sagittal power331is equal to the radial curvature power332. For the lens601ofFIGS.6A and6B, the radial sagittal power331and radial curvature power332across the central region305are more negative than the nominal distance power of the lens (indicated by the dashed line330).

At the boundary between the central zone305and the inner treatment zone303a, there is an increase in radial curvature power332. The inner treatment zone303ahas a greater curvature than the central zone305and therefore provides a radial add curvature power. The radial curvature power332is approximately constant across the width of the inner treatment zone303a. At the boundary between the inner treatment zone303aand the outer treatment zone303b, there is another sharp increase in the radial curvature power332. The outer treatment zone303bhas a greater curvature than the innermost treatment zone303aand provides a greater radial curvature add power.

Across the inner treatment zone303a, the radial sagittal power331increases with a constant positive gradient. At a point halfway across the radial width of each treatment zone303a,303b, the radial sagittal power331matches the nominal distance power of the lens303. The gradient of the radial sagittal power profile331across the outer treatment zone303bis greater than the gradient across the inner treatment zone303a.

FIG.8is a schematic partial ray diagram (not to scale) showing how the treatment zones303a,303bof the lens301ofFIGS.6A and6Bfocus light when the lens301is positioned on the eye. Light from a distant point source passing through the small central zone305is focused towards a spot on the optical axis319at a central zone focal surface318. The inner treatment zone303aand outer treatment zone303bare both radially tilted relative to the central zone305, and therefore light from a distant point source passing through the treatment zones303a,303bis not focused towards a single spot on the optical axis319. Light rays from a distant point source that pass through the radial midpoint of each treatment zone303a,303bconverge at a convergence surface317that intersects the optical axis319, and is positioned posterior to the lens301when the lens301is positioned on the eye. This convergence surface317is the best distal focal surface, and determines, to a first approximation the nominal distance power of the lens301. For the lens301ofFIGS.6A-6B, the nominal distance power is greater than the radial curvature power of the central region305, and therefore the best distal focal surface is anterior in the eye compared to the central zone focal surface318.

For the lens301shown inFIGS.6A and6B, each treatment zone303a,303bhas a radial curvature power that is greater than the nominal distance power and the radial curvature power of the central region305. Light from a distant point source that passes through the treatment zones303a,303bis therefore focused towards surfaces341,343that are anterior in the eye compared to the nominal distance focal surface317and the central zone focal surface318. The radial curvature power profile is approximately constant across the width of each treatment zone303a,303b.

The innermost radial treatment zone303ahas a low radial curvature add power. The focal surface341for light rays from a distant point source passing through this treatment zone303ais therefore shifted closer to the lens301than the distal focal surface317. This inner treatment zone303ais radially tilted relative to the central zone305, and light rays from a distant point source passing through this treatment zone303aare therefore not focused towards a single spot on the optical axis319. Instead, light rays from a distant point source passing through the innermost treatment zone303aform an annular ring337at a low add focal surface341.

The outer treatment zone303b, which is positioned adjacent to the inner treatment zone303a, at a greater radial distance from the optical axis319, has a high radial curvature add power, which is greater than the radial curvature add power of the inner treatment303a. This outer treatment zone303btherefore focuses light from a distant point source towards a high add focal surface343that is closer to the lens301compared to the distal focal surface317and compared to the low add focal surface341. The outer treatment zone303bis also tilted relative to the central zone305, and so light from a distant point source passing through the second treatment zone303bis not focused towards a spot on the optical axis319, but instead forms an annular ring339at the high add focal surface343.

FIG.9Ashows a schematic top view of a lens401according to another embodiment of the present disclosure.FIG.9Bshows a schematic cross-sectional view of the lens ofFIG.9A. The lens401comprises an optic zone402, which approximately covers the pupil, and a peripheral zone404that sits over the iris. The peripheral zone404provides mechanical functions, including increasing the size of the lens401thereby making the lens401easier to handle, providing ballasting to prevent rotation of the lens401, and providing a shaped region that improves comfort for the lens401wearer. The optic zone402provides the optical functionality of the lens401. The optic zone402comprises a small central region405having a diameter of 0.5 mm, and an annular region403surrounding the central region405. The annular region403comprises two concentric treatment zones403a,403b. Both treatment zones403a,403bare radially tilted relative to the central zone405. Both treatment zones403a,403bhave a radial curvature power that is greater than the radial curvature power of the central zone405, and greater than the nominal distance power of the lens401. For this lens401, each treatment zone403a,403bprovides the same radial curvature add power relative to the central region405.

FIG.10shows the radial sagittal power profile431and radial curvature power profile432taken along a radial diameter of the lens401shown inFIGS.9A and9B. Across the width of the central region405, the radial sagittal power profile431and radial curvature profile432are flat. Across the width of the central region405, the radial sagittal power431is equal to the radial curvature power432, and this may hereafter be referred to as the base power. For the lens401ofFIGS.9A and9B, the base power is equal to the nominal distance power of the lens (indicated by the dashed line430).

At the boundary between the central zone405and the inner treatment zone403a, there is a sharp increase in the radial curvature power432. The inner treatment zone403ahas a greater curvature than the central zone405and therefore provides a radial add curvature power. The radial curvature power432is constant across the width of the innermost treatment zone403a. At the boundary between the inner treatment zone403aand the outer treatment zone403b, there is no change in the radial curvature power432. The outer treatment zone403bhas the same radial curvature add power as the inner treatment zone403a.

At the boundary between the central zone405and the inner treatment zone403a, there is a sharp decrease in the radial sagittal power431, and across the inner treatment zone403a, the radial sagittal power431increases with a constant positive gradient. At the boundary between the inner treatment zone403aand the outer treatment zone403b, there is another sharp decrease in the radial sagittal power431. The gradient of the radial sagittal power profile431is smaller across the outer treatment zone403b, because at greater radial distances from the optical axis, a smaller radial sagittal power is required to produce the same radial curvature power.

FIG.11is a schematic partial ray diagram (not to scale) showing how the treatment zones403a,403b, of the lens401ofFIGS.9A and9Bfocus light when the lens401is positioned on the eye. Light from a distant point source passing through the small central zone405is focused towards a spot on the optical axis419at a central zone focal surface418. The inner treatment zone403aand outer treatment zone403bare both radially tilted relative to the central zone405, and therefore light from a distant point source passing through the treatment zones403a,403bis not focused towards a single spot on the optical axis419. Light rays from a distant point source that pass through the radial midpoint of each treatment zone403a,403bconverge at a convergence surface417that intersects the optical axis419, and is positioned posterior to the lens401when the lens401is positioned on the eye. This convergence surface417is the best distal focal surface, and determines, to a first approximation the nominal distance power of the lens401. For the lens401ofFIGS.9A-9B, the best distal focal surface coincides with the central zone focal surface418.

For the lens401shown inFIGS.9A and9B, both treatment zones403a,403bhave the same radial curvature add power. As a result of the radial curvature add power, light from a distant point source that passes through treatment zone403aor treatment zone403b, is focused at an add power focal surface441that is closer to the lens401than the distal focal surface417.

This innermost treatment zone403ais radially tilted relative to the central zone405, and light rays from a distant point source passing through this treatment zone403aare therefore not focused towards a single spot on the optical axis419. Instead, as shown inFIG.11, light rays from a distant point source passing through the innermost treatment zone403aform an annular ring437at an add power focal surface441.

The outer treatment zone403bis also tilted relative to the central zone405and relative to the inner treatment zone. Light from a distant point source passing through the outer treatment zone403bis not focused towards a spot on the optical axis419, but instead forms an annular ring439at the add power focal surface441. As the outer treatment zone403bis positioned at a greater radial distance from the optical axis than the inner treatment zone403a, and as the relative radial tilts of the inner403aand outer403btreatment zones are different, the diameter of the annular ring439formed from light passing through the outer treatment zone403bis greater than the diameter of the annular ring437formed from light passing through the inner treatment zone403a.

FIG.12Ashows a schematic top view of a lens501for use in the slowing progression of myopia (e.g., myopia control) according to another embodiment of the present disclosure.FIG.12Bshows a schematic cross-sectional view of the lens501ofFIG.12A. The lens501comprises an optic zone502, which approximately covers the pupil, and a peripheral zone504that sits over the iris. The peripheral zone504provides mechanical functions, including increasing the size of the lens thereby making the lens501easier to handle, providing ballasting to prevent rotation of the lens501, and providing a shaped region that improves comfort for the lens501wearer. The optic zone502provides the optical functionality of the lens501. The optic zone502comprises a small central region505having a diameter of 0.5 mm, and an annular region503surrounding the central region505. The annular region503comprises two concentric treatment zones503a,503b. Both of the treatment zones503a,503bare radially tilted relative to the central zone505, and both treatment zones503a,503bprovide a radial curvature add power relative to the central region505and relative to the nominal distance power of the lens505.

FIG.13shows the radial sagittal power profile531and radial curvature power profile532taken along a radial diameter of the lens501shown inFIGS.12A and12B. Across the width of the central region505, the radial sagittal power profile531and radial curvature power profile532are flat. Across the width of the central region505, the radial sagittal power531is equal to the radial curvature power532. For the lens501ofFIGS.12A and12B, the radial sagittal power531and radial curvature power532across the central region505is more negative than the nominal distance power of the lens (indicated by the dashed line530).

Both of the treatment zones503a,503bhave a radial curvature power532that is greater than the nominal distance power. At the boundary between the central zone505and the inner treatment zone503a, there is a sharp increase in the radial curvature power profile532. The inner treatment zone503ahas a greater curvature than the central zone505and the nominal distance power of the lens501and therefore provides a radial add curvature power. The radial curvature power532is constant across the width of the innermost treatment zone503a. At the boundary between the inner treatment zone503aand the outer treatment zone503b, there is a further increase in the radial curvature power532. The outer treatment zone503bhas a greater radial curvature add power than the inner treatment zone503a.

Across the innermost treatment zone503a, the radial sagittal power531increases with a constant positive gradient. The outer treatment zone503bhas been tilted relative to the central region505and the inner treatment zone503a, and the radial sagittal power531is greater across the width of the outer treatment zone503than across the width of the inner treatment zone503a. Across the width of the outer treatment zone503b, the radial sagittal power531increases with a constant gradient. Across the width of the outer treatment zone503b, the radial curvature power532of the outer treatment zone is greater than the radial sagittal power531.

FIG.14is a schematic partial ray diagram (not to scale) showing how the treatment zones503a,503b, of the lens501ofFIGS.12A and12Bfocus light when the lens501is positioned on the eye. Light from a distant point source passing through the small central zone505is focused towards a spot on the optical axis519at a central zone focal surface518. The inner treatment zone503aand outer treatment zone503bare both radially tilted relative to the central zone505, and therefore light from a distant point source passing through the treatment zones503a,503bis not focused towards a single spot on the optical axis519. Light rays from a distant point source that pass through the radial midpoint of the treatment zones503a,503bconverge at a convergence surface517that intersects the optical axis519, and is positioned posterior to the lens501when the lens501is positioned on the eye. The convergence surface517is the best distal focal surface, and determines, to a first approximation, the nominal distance power of the lens501. For the lens501ofFIGS.12A-12B, the nominal distance power is less negative than the radial curvature power of the central region505, and therefore the best distal focal surface517is closer to the lens501than the central zone focal surface518.

For the lens501shown inFIGS.12A and12B, the inner treatment zone503ahas a radial curvature power that is greater than the nominal distance power and the radial curvature power of the central region505, but less than the radial curvature power of the outer treatment zone503b. As a result, light from a distant point source that passes through the inner treatment zone503ais focused towards a low add power focal surface541that is closer to the lens501than the distal focal surface517and the central zone focal surface518. The inner treatment zone503ais radially tilted relative to the central zone505and so light from a distant point source passing through the inner treatment zone503aforms an annular ring537at the low add power focal surface541. The outer treatment zone503bis tilted relative to the central region505and the inner treatment zone503a, and the outer treatment zone503bhas a radial sagittal power across its width that is greater than the radial sagittal power across the inner treatment zone503a. Light rays from a distant point source that pass through the radial midpoint of the outer treatment zone503b(i.e., a point halfway across the radial width of the outer treatment zone503b) converge at a point544on the optical axis at a sagittal add power convergence surface545. Light rays from a distant point source that passes through the outer treatment zone503bare focused towards a high add power focal surface543that is closer to the lens501than the low add power focal surface541, the distal focal surface517and the central zone focal surface518. The outer treatment zone503bis radially tilted relative to the central zone505and so light from a distant point source passing through the outer treatment zone503bforms an annular ring539at the high add power focal surface541.

FIG.15is a flowchart showing a method660of manufacturing a contact lens, according to an embodiment of the present disclosure. The contact lens includes an optic zone comprising a central region, the central region having a first optical axis, a base radial sagittal power, a centre of curvature that is on the first optical axis, and a radial diameter that is less than 0.5 mm. The optic zone comprises an annular region comprising a plurality of treatment zones, wherein each treatment zone has a radial sagittal power profile that increases with increasing radial distance from the optical axis. The lens may include any of the features set out above. In a first step661the method comprises forming a female mold member with a concave lens forming surface and a male mold member with a convex lens forming surface. In a second step663, the method comprises filling a gap between the female and male mold members with bulk lens material. In a third step665, the method comprises curing the bulk lens material to form the lens.

In alternative embodiments of the present disclosure, the lens may be formed using a lathing process, a cast molding processes, spin cast molding processes, or lathing processes, or a combination thereof.

It will be appreciated by those of ordinary skill in the art that features of these example embodiments may be combined in other embodiments that fall within the scope of the present disclosure.

In the example embodiments of the present disclosure described inFIGS.6A-14above, the contact lenses include two concentric treatment zones. In other embodiments, the contact lens may include more than two concentric treatment zones. For example, the contact lens may include between two and ten concentric treatment zones. In the example embodiments of the present disclosure described inFIGS.6A-14above, the treatment zones have approximately the same radial width. In other embodiments, the treatment zones may have different radial widths.

In embodiments of the present disclosure, the coaxial regions and non-coaxial regions of the contact lens may have the same curvature power. In other embodiments, the coaxial regions and non-coaxial regions of the contact lens may have different curvature powers.

Whilst in the foregoing description, integers or elements are mentioned which have known obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as advantageous, convenient or the like are optional, and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the disclosure, may not be desirable and may therefore be absent in other embodiments.