EP4655639A1 - A multifocal diffractive ocular lens with adaptive power - Google Patents

Abstract

An ophthalmic multifocal lens, arranged to provide far vision, and at least one other usable vision at most at a range of 1 meter with at least three contiguous diffractive orders of which at least two are useful is proposed. Said useful orders comprise at least one positive and at least one negative diffractive order, said diffraction grating operating as an optical wave splitter is configured to have a variable period in quadratic space, said ophthalmic lens comprising at least one first concentric region wherein said variable period of said diffraction grating is configured to monotonically change in relation to the radius of the lens, said lens comprises a preferred diffractive order, and; said lens comprises at least a counteracting mechanism configured to keep power of said preferred diffractive order stable.

Description

A MULTIFOCAL DIFFRACTIVE OCULAR LENS WITH ADAPTIVE POWER

Technical Field of the Present Invention

The present disclosure generally relates to ophthalmic lenses as well as to ophthalmic contact and intra-ocular multifocal lenses, more specifically ones where the multifocality is provided by a diffractive structure that is arranged with varying diffractive power in a way best serve human vision over different pupil sizes under various light conditions.

Background of the Present Invention

Diffractive lenses for ophthalmological applications are constructed as hybrid lenses with a diffractive pattern added onto a refractive body. Often one side of the lens is purely refractive, while the other side has a diffractive grating superpositioned over a refractive base line. The refractive baseline can be spherical, or alternatively have an aspherical shape. The diffractive part can in general be applied to any of the two sides of the lens, since when a diffractive pattern is to be combined with a refractive surface with some special feature it generally does not matter if they are added to the same side or if one is added to a first side and the other to a second side of the lens. Concurrently, two diffractive patterns may be combined either by super positioning on one side, or by adding them on separate sides in an overlapping fashion. The optical power of the lens for a specific diffraction order can be calculated by addition of the refractive base power and the optical power of that diffraction order. The most well-researched type of diffraction lens proper is the monofocal phase-matched Fresnel lens as taught by Rossi et al. in their 1995 study titled "Refractive and diffractive properties of planar micro-optical elements". This type of lens makes use of a sawtooth diffractive unit cell and a step height corresponding to a phase modulation of exactly 2n.

Most diffractive multifocal lenses that are available in the market today are still ones that are based on a so-called "sawtooth" diffractive grating where the 0^th order of said grating is used to provide far vision for a user. Far vision is generally configured to be the lowest power that is usable for the eye, so the order of the usable orders that has the lowest power is generally assumed to be used for far vision. Whereas said sawtooth diffractive grating is the most light-efficient configuration for a strictly bifocal lens, this effect is not translated well into other multifocal lenses with higher numbers of foci. Most multifocal lenses with more than two foci still use a configuration where the 0^th order is utilized to provide far vision to the user akin to the case in sawtooth diffractive gratings, due to it being relatively easier to design a lens that provides high quality vision at the 0^th order. Far vision is usually prioritized, especially for intraocular lenses as surgical success is usually determined by the functionality of far vision.

However, recent progress has shown that several important advantages are associated with designing lenses that utilize an order other than the 0^th order for providing far vision, specifically those having useful orders simultaneously on both sides of the zeroth order. Specific sets of advantages arising from such designs differ between various types of possible configurations. As an example, binary diffractive lenses, utilizing typically -1^st order, +l^st order as well as the 0^th order, contain fewer rings than corresponding trifocal sawtooth lenses, and have grating peaks that are less narrow, however retaining sharp transitions. Ophthalmic lenses based on binary grating and their advantages have been known for a long time, as demonstrated by WO1994011765A1. Such gratings can be either trifocal or bifocal, depending on the height of the structure. Symmetric sinusoidal diffractive gratings, i.e. sinusoidal diffractive gratings that have their orders evenly arranged around the 0^th order are the most lightefficient gratings possible for diffractive lenses with an odd number of usable focal points, they avoid sharp transitions in the diffractive profile, increase manufacturability, and biocompatibility. Asymmetric diffractive lenses, that are lenses with a different number of usable orders on each side of the 0^th order can, in some cases, be advantageous and retain most of the benefits of symmetrical sinusoidal gratings. Additionally, the asymmetric diffractive gratings may have a smaller relative difference in power between the 0^th order and the order used for far vision, which can be an advantage. Useful asymmetric gratings can be sinusoidal (that is, lacking discontinuities) or utilizing sharp transitions sawtooth-like. The latter is exemplified in WO2021245506. Increasing the number of diffractive orders increases the total potential light efficiency, e.g. an asymmetric diffractive lens having four orders can be more efficient than a symmetric lens utilizing three orders, an asymmetric lens having six orders can be more efficient than a corresponding symmetric lens using five orders.

There are several examples in the prior art, where several of these drawbacks with lenses based on gratings utilizing orders on both sides of the 0^th order have been overcome or mitigated to a certain extent. IL105434, as an example, discloses a light efficient trifocal lens. Yet another document EP20170183354 describes a way to optimize performance by horizontally shifting a given diffractive grating, but without strong aperture adaption.

WO2021089178A1 describes a way to construct a multifocal lens combining a monofocal central zone, providing far vision only, and a symmetric multifocal grating. That document discusses in great detail how to combine a monofocal center zone with a symmetric diffraction grating to achieve as high light efficiency as possible. It also provides a description on how to achieve a desired intensity distribution for one aperture. The addition of a purely monofocal central zone decreases, however, the total light efficiency compared to a lens with a highly efficient grating of the whole lens surface.

W02019020435A1 discloses a multifocal lens comprising a diffraction grating designed to operate as an optical wave splitter for distributing light incident at said lens body in said refractive and diffractive focal points. Said diffraction grating has an optical transfer function comprising a continuous periodic phase profile function extending in radial direction of the lens body. Said continuous periodic phase profile function also comprises an argument modulated as a function of radial distance to said optical axis of said lens body, thereby tuning said distributing of light incident at said lens body.

WO2022177517A1 discloses an ophthalmic multifocal lens with a light transmissive body with an optical axis and a refractive baseline extending over part of the body of the lens. It also discloses a first portion coinciding with a central area of said lens body and a multifocal second portion extending concentrically radially; said second portion further comprising a symmetric multifocal diffractive grating superpositioned onto said baseline, covering a portion of the lens, its shape and resulting light intensity distribution changing with distance to optical axis. In other words, this disclosure describes aperture- adaptive diffractive lenses with greater light efficiency and higher effective efficiency due to better adaption to the anatomy of the eye. It further describes a way to shape each period of the diffraction individually to provide at each aperture (and corresponding pupil size) the desired intensity distribution between e.g. far, intermediate, and near vision.

However, in spite of this progress diffractive lenses using diffraction orders on both sides of the 0^th order made according to prior art still have certain drawbacks compared to sawtooth lenses: First, they often have worse chromatic aberrations at the far distance. Second, when such a diffraction grating is tuned for desired performance according to the prior art, the actual diffractive power will often vary as a function of the radius, especially for small apertures. Third, it is still difficult to reduce intensity of light directed towards focal points closer to the user than far vision. There is sometimes a tendency for the 0^th order to dominate more than the desirable level, especially for large apertures. An even larger problem is proper reduction of near vision intensity. As a fourth point, one inherent advantage of the sawtooth based lenses is the possibility of the apodized diffractive lens. For example, an apodized trifocal, sawtooth-based lens can decrease the intensity provided to near and intermediate vision at large pupil sizes simply by decreasing the height of the diffractive profile. In the art such solutions exist to an extent, such as an adaptive diffractive lens described WO2022177517A1, but it would be advantageous to be able to design lenses with an even more pronounced adaptive behavior than made possible by that document. Apodization can also help with the reduction of the intensity of positive dysphotopsia for large apertures. This is something that has not been properly addressed for diffractive lenses where apodization is not possible.

Well-functioning diffractive lenses with useful orders on both sides of the 0^th order can optionally possess sharp transitions in the diffraction profile. Lenses with sharp transitions including e.g. lenses with sawtooth profiles or binary profiles such as WO9411765, give rise to machining difficulties and, for a finished lens, scattering of light, increased incidence of several unwanted optical phenomena such as stray light and glare i.e. sight difficulty under bright light conditions such as direct or reflected sunlight or artificial light such as car headlamps at night, and halo effects i.e. white or colored light rings or spots seen at dim light, i.e. under mesopic conditions. These effects are collectively dubbed as positive dysphotopsias. Diffractive lenses without sharp transitions are often better performing with respect to these issues, next to also having higher potential diffraction efficiency, at the very least for multifocal lenses with an odd number of focal points. It has also been suggested that sinusoidal or smooth diffractive profiles are more biocompatible compared to sawtooth profiles because of reduction in the debris precipitation effect, as explained in Osipov et al. in their 2015 study "Application of nanoimprinting technique for fabrication of trifocal diffractive lens with sine-like radial profile" as published in Journal of biomedical optics 2Q, no. 2 (2015): 025008. However, it is known that good results in general can be reached with diffractive lenses having sharp transitions, even if good manufacturing of such lenses as a whole is more difficult and require larger investments in manufacturing equipment.

Because of reasons given above it is often advantageous to use multifocal, hybrid lenses utilizing diffractive gratings with both positive and negative useful diffraction orders. However, as detailed above, such lenses that exist in the prior art have several limitations.

For a lens to provide vision enough for a user to be spectacle independent it needs to provide far, intermediate, and near vision. In photopic conditions, when small pupils are present a full multifocal vision with an especially strong far vision is desired. But a central aperture of the lens that provides a very narrow far vision runs an increased risk of diopter mismatch. A central portion of the lens providing slightly stronger power than the intended power of far vision will decrease this risk. This is especially important since quality of the far vision is indeed what determines clinical success of cataract surgery. Additionally, such a distribution is also able to provide higher overall light efficiency when splitting the light with a diffraction grating, as will be demonstrated hereinafter. Because of the well-known pinhole effect, causing a small pupil to provide a much higher depth of focus, small shifts in power for tiny pupils have no negative effect on vision. It is also important to be able to exactly choose the dominant power for very small apertures of a lens since different autorefractometry technologies might measure the post-operative power at different apertures and there might arise a need to change only the 1 mm dominant power to comply with a specific autorefractometry technology.

In mesopic conditions with slightly larger pupils the pinhole effect is no longer in effect making it very important for multifocal lens intended for spectacle independence to provide a strong near vision in addition to far vision. For full spectacle independence intermediate vision is also desired.

Due to the accommodation reflex human pupils constrict when viewing near objects, even in scotopic environments. Because of this, light focused for near vision at large pupils is physiologically not possible to use. Intermediate vision is much less afflicted by this problem, which on balance proves that reduction of light directed to near vision for large apertures is much more important than reduction of intermediate vision. Designing according to this principle ensures physiological efficiency of light in addition to technical light efficiency.

Accordingly, there is a need for an improved ophthalmic lens that utilizes the advantages of diffractive gratings with usable orders on both sides of the zeroth order, including very high light efficiency, fewer diffractive rings, and the possibility to have biologically and manufacturing-wise more suitable diffractive profiles in a way that allows for exact placement of the dominant optical power for any aperture; while improving the still unsolved problems with such lenses, including the limited possibility to properly tune energy distribution over a range of apertures, the problem in some such lenses of sharp undesired diffractive peaks for larger apertures causing positive dysphotopsia, and the problem in some such diffractive lenses of power varying with aperture for small apertures.

Objects of the Present Invention

Primary object of the present invention is to provide an ophthalmic multifocal lens, comprising a refractive baseline, an optical axis and providing at least three focal points, one of them providing far vision to a user.

Another object of the present invention is to provide an ophthalmic multifocal lens that provides far vision in a configuration using a diffractive order other than the 0^th order, while retaining a high quality comparable to configurations that use the 0^th order to provide far vision.

A further object of the present invention is to provide an ophthalmic multifocal lens comprising a diffractive grating that combines a very sharp far vision - where the lens at each aperture contributes to a far vision at the same net power - with peaks for e.g. intermediate and near vision which are, at least for one range of apertures, purposefully broadened.

A still further object of the present invention is to provide an ophthalmic multifocal lens wherein said lens significantly reduces clinically relevant incidence of glare, halo and similar positive dysphotopsia for an intraocular lens using a diffractive order other than the 0^th order to provide far vision. A still further object of the present invention is to provide an ophthalmic multifocal lens that allows for a configuration of the center of said diffractive lens that, regardless of horizontal shift applied on a diffractive in the lens, enables lenses where all desired diffractive orders of said lens contribute to exactly the same net power for each aperture.

A still further object of the present invention is to provide an ophthalmic multifocal lens design method whereby sinusoidal diffractive lenses with higher overall light efficiency with high peak intensities are manufacturable.

Brief Description of the Present Invention

In a first aspect, there is provided an ophthalmic multifocal lens, at least comprising a focal point for far vision. The lens having a light transmissive lens body comprising a diffraction grating having useful diffraction orders on both sides of the zeroth order extending concentrically in a radial direction from an optical axis of the lens body across a part of a surface of the lens body. The lens comprises at least a refractive baseline, as well as a varying pitch. A well- formed diffractive lens has, as known in the art, a pitch that is in absolute terms (i.e. measured in millimeters) varies with the radius, however is constant in quadratic (r²) space. As such, a diffractive lens with varying pitch is a lens where the pitch of the diffractive grating is not kept constant in r² space.

Lenses manufactured according to the present disclosure, as a result of having a varying pitch, enable more pronounced and adaptive behavior. A prominent feature of several of the disclosed diffractive lenses is the strong reduction of near vision from mesopic condition to scotopic condition. A feature of some of the disclosed lenses caused by use of a varying pitch in a central portion of the lens causes one or more of the diffractive peaks to keep their respective power unchanged as a function of aperture sizes. Present disclosure also enables production of diffractive multifocal lenses with a better compromise between the overall diffractive efficiency and quality of vision, specifically quality of vision for the most critical distance, which typically is far vision. Also, said lenses display a higher total light efficiency for identical intensity peaks.

Present disclosure also enables diffractive lenses to be manufactured that significantly reduce the halo effect, and other similar positive dysphotopsias. This is achieved both by aforementioned higher light efficiency, as well as the lowering of the maximum intensity of the undesired peaks that are the main culprit behind effects such as halo/glare, the main disadvantage of multifocal lenses in the art. Another aspect that aids this also the decreased near intensity for large apertures.

Present disclosure also provides a new type of diffractive extended depth for lenses, capable of providing e.g. a very strong far vision with a power that is constant across all apertures combined with much broader peaks for intermediate and near vision, to provide true continuous vision for large parts of the total usable focal depth.

Brief Description of the Figures of the Present Invention

Accompanying drawings are given solely for the purpose of exemplifying a multifocal aphakic diffractive multifocal lens, whose advantages over prior art were outlined above and will be explained in brief hereinafter.

The drawings are not meant to delimit the scope of protection as identified in the claims nor should they be referred to alone in an effort to interpret the scope identified in said claims without recourse to the technical disclosure in the description of the present invention.

Figure 1 demonstrates a simplified anatomy of the human eye.

Figures 2a and 2b demonstrate a front and side view, respectively, of an ophthalmic multifocal aphakic intraocular lens as known in the art.

Figure 2c demonstrates the diffractive profile and the intensity graph of an adaptive lens optimized for maximized diffractive peaks, designed according to the prior art.

Figure 2d demonstrates the diffractive profile and the intensity graph of an adaptive lens optimized for maximized total light total intensity within the usable region, designed according to the prior art.

Figures 3a and 3b demonstrate a front and side view, respectively, of an ophthalmic multifocal aphakic intraocular lens made according to the present invention.

Figures 3c and 3d demonstrate in real space and r² space, respectively, the diffractive profile of a diffractive lens made according to the present invention.

Figure 3e demonstrates the change in pitch as a function of radius in a diffractive profile of a diffractive lens made according to the present invention.

Figure 3f demonstrates the corrective profile of a lens made according to the present invention.

Figure 3g demonstrates the full profile, less the refractive baseline, of a lens made according to the present invention.

Figure 3h demonstrates the modelled light intensity distribution of a lens made according to the present invention.

Figure 3i shows measurements of a lens manufactured according to the present invention.

Figure 4a is a comparison of two diffractive profiles with high overall optical efficiency, the upper profile is made according to the prior art, while the lower profile is made according to the present invention

Figure 4b demonstrates the modelled intensity graph of the two diffractive lens profiles in Figure 4a.

Figures 5a and 5b demonstrate, respectively, the profile, less the refractive baseline, and the intensity graph of another diffractive lens made according to the patent.

Figures 6a and 6b demonstrate, respectively, the profile, less the refractive baseline, and the intensity graph of yet another diffractive lens made according to the patent.

Figure 6c demonstrates the profile of the diffractive profile shown in Figure 6a plotted in r² space, less refractive baseline as well as the corrective profile.

Figures 7a and 7b demonstrate the profile and relative intensity, respectively, of a quadrifocal lens made according to the present invention. Figure 8a demonstrates the profile of a binary diffractive lens, made according to the present invention.

Figure 8b demonstrates the change in pitch as a function of radius in the binary diffractive lens of Figure 8a.

Figure 8c demonstrates the absolute intensity graph of the binary diffractive lens from Figure 8a.

Detailed Description of the Present Invention

10 Eye

11 Cornea

12 Pupil

13 Natural crystalline lens

14 Retina

15 Posterior cavity

16 Anterior and posterior chambers

17 Far vision

18 Intermediate vision

19 Near vision

20 Optical axis

29 Optical axis

30 Ophthalmic lens

31 Lens body

32 Haptic(s)

33 Center part

34 Front surface 35 Rear surface

36 Diffraction grating

37 Optic diameter

38 Outer diameter

39 Center thickness

50 Multifocal aphakic intraocular lens

51 Multifocal diffractive profile with varying pitch

52 Anterior surface

53 Posterior surface

54 Lens body

55 Corrective profile with varying power

One important property of diffractive gratings is the distinction between symmetric and asymmetric diffraction gratings. When ascribing symmetric or asymmetric property to multifocal ophthalmic lenses, what is considered is which diffraction orders it makes use of or renders useful. Symmetric diffractive lenses utilize orders in a way that is symmetric around the 0^th order. Note that symmetric diffraction gratings are defined by which orders they utilize, not by the intensity of light distribution in these orders. Some symmetric diffractive lenses may be tuned so that there is a significant difference in light intensity between e.g., +1 and -1 orders, i.e. they have an unequal light distribution. A diffraction grating tuned as such would still be considered a symmetric diffraction grating. Lenses based on symmetric gratings can be trifocal, making use of order -1, 0, and +1, or pentafocal, making use of order -2, -1, 0, +1, and +2. Such symmetric gratings can be sinusoidal or non-sinusoidal. A commonly known non-sinusoidal symmetric grating is the binary grating. However, gratings not making use of the 0^th order can also be considered symmetric. Specifically, the symmetric case of a grating making use of the four order -2, -1, +1, and +2 can, in some cases, be useful for ophthalmic lenses.

The vast majority of ophthalmic diffractive trifocal lenses make use of sawtooth profiles. Combining sawtooth profiles of two bifocal diffractive lenses to achieve trifocality is known in the art. This results in diffractive lenses with the usable orders arranged asymmetrically with respect to the 0^th order, e.g. a trifocal lens might make use of orders 0, +1, and +2 orders or 0, +2, and +3. Such diffraction gratings are henceforth referenced as asymmetric gratings. But there are also asymmetric gratings that make use of focal points on both sides of the zeroth order. Such gratings can have discontinuities and be sawtoothlike, or they can alternatively be sinusoidal gratings without any discontinuities.

Many things will affect which type of grating is most suitable. Diffractive lenses having a continuous and smooth profile without any sharp edges are suitable across a greater range of manufacturing technologies and are often less expensive to realize with needed precision. They also have better biocompatibility, and at least for an odd number of diffraction orders, they also display the highest possible diffraction efficiency. Whereas, it has been proven that gratings having discontinuities can be manufactured and used advantageously as intraocular lenses. The best grating to choose often depends on a combination of available manufacturing equipment and the goals of the lens in question.

The highest possible diffraction efficiency for most useful intensity distribution for diffractive multifocal lenses with an odd number of foci, including trifocal lenses, is provided by smooth sinusoidal surfaces with usable orders symmetrically arranged around the 0^th order.

When comparing diffractive surfaces, an important factor is the diffractive efficiency. Diffraction efficiency is a measure of how much of the optical power is directed into the desired diffraction orders, or, when referring to diffractive lenses in particular, how much of the optical power is directed into the desired focal points. For bifocal lenses, where the surface of the lens body is optimized to provide an as good vision as possible at two distinct distances, the highest possible diffraction efficiency is reached by using the principles of a phase- matched Fresnel lens, which makes use of a sawtooth or jagged type diffraction pattern. Reference is made to the publication "Refractive and diffractive properties of planar micro-optical elements", by M. Rossi et al., in Applied Optics Vol. 34, No. 26 (1995) p. 5996-6007, which is herein incorporated by reference.

It can be advantageous to first consider linear phase grating since that field has a well-developed theory and can be utilized for diffractive lenses. It is accordingly one way of calculating the diffractive unit cell to be used. For the special case of a trifocal linear grating with an equal intensity distribution to each order, it is shown specifically that the optimal solution is a structure without sharp edges in the publication "Analytical derivation of the optimum triplicator", by F. Gori et al., in Optics Communication 157 (1998), p. 13-16, which publication is herein incorporated by reference.

The publication "Theory of optimal beam splitting by phase gratings. I. Onedimensional gratings", by L. A. Romero and F. M. Dickey, in Journal of the Optical Society of America Vol. 24, No. 8 (2007) p. 2280-2295, which publication is herein incorporated by reference, discloses this more generally, proving that at the very least that optimal gratings for equal splitting into odd number of orders have continuous profiles. This latter paper provides the mathematical tools to find the optimal linear phase grating for any given set of target orders and any given intensity distribution among those target orders. The optimal grating is defined as the linear diffraction grating with the highest diffraction efficiency for the specified intensity distribution. It is noted that the publications by Gori et al. and Romero et al. discuss linear phase gratings only with the intent of creating beam splitters. By treating the x-axis of the linear grating as the r² space of a diffractive lens, any such linear phase can be turned into a lens. This optimization theory is one of several good ways to find a way to start developing a lens grating. However, optimizing for the highest diffraction efficiency is not always the best option for a diffractive unit cell to be used in a grating, there are important effects specific for lenses not taken into account by optimization of linear phase gratings, optimizing for these effects can be advantageous when designing lenses according to the present invention. It is demonstrated, according to the present disclosure, that if low height is seen as a desirable trait for a diffractive grating, then the cosine-half step grating can in certain cases be strictly better than corresponding optimized grating. Additionally, the known optimization process does not take into account the dramatic effect of horizontal shifting of diffractive gratings in diffractive lens designs. To find the actual, final diffractive unit cell for optimum performance one should rely on a combination Fourier modelling and actual manufacturing followed by measurements.

There are different ways to calculate and tune diffractive lenses having useful orders on both sides of the 0^th order in the art. One way is to use optimized linear grating transformed into diffractive lenses, as described above and in further detail PCT/EP2019/080758. One early example of a lens based on a symmetric diffractive grating is the 7-focal lens described in the paper by Golub et al., titled "Computer generated diffractive multi-focal lens" published in Journal of modern optics 39, no. 6 (1992): 1245-1251. As a continuation of this, additional embodiments in the already mentioned Osipov 2015 study as well as the study published in 2012 by Osipov et al. called "Fabrication of three- focal diffractive lenses by two-photon polymerization technique" published in Applied Physics A 107, no. 3 (2012): 525-529. In these papers trifocal, symmetric lenses made by modifications to a sinus grating are disclosed. In these studies by Osipov et al. only one unit cell is used per lens, but with what is now known, the diffractive grating for an properly adaptive lens could be constructed from a set of modified sinus gratings made as described. A different approach is also disclosed in US5760871A and IL104316, where a so called asymmetric super Gaussian formula is used to design trifocal gratings with unequal intensity distribution. A set of such diffraction unit cells could be used together, with proper transition zones, to form a proper diffraction grating for an adaptive lens according to the patent. Yet another method is the one described in W02020053864A1, where the Gerchberg-Saxton iterative algorithm is used to design the surface profile of a pentafocal (having five focal points) lens with a symmetric diffraction grating. How to construct a proper trifocal lens based on a binary was disclosed in WO9411765.

The lens according to the present invention is an ophthalmic lens comprising at least a refractive baseline and a diffractive grating super positioned on to the refractive baseline, arranged so that, for a design wavelength, orders on both sides of the 0^th order are made usable for a user of the lens.

A strong far vision is the typical criterion to ascertain the success of cataract surgery. This is because a strong far vision is important for all apertures. In this document there is a lot of specific discussion of lens performance at different apertures. To simplify the text the apertures and pupil sizes that are all defined in the anterior lens plane, assuming an average human eye. But to be clear, the corresponding pupil sizes are larger, the exact sizes of which will differ slightly from person to person. In the average human eye a 2 mm aperture in the lens plane corresponds to a 2.35 mm pupil diameter, 3 mm in the lens plane corresponds to 3.515 mm, 4.5 mm to 5.28 mm, and 6 mm to 7.04 mm.

One important aspect of the present invention is adaptivity. Adaptivity is here defined as a measure of functional light utilization for the human eye. The eye has a much larger depth of field at pupil sizes that are smaller, due to the pinhole effect. Pupil size, not being solely dependent on the pupillary light reflex, is also dependent on the accommodation reflex, which causes the pupil not sufficiently enlarging while focusing on objects of closer proximity. Adaptive intraocular lenses are designed to change the light intensity to different focal points of that specific lens as a function of pupil size. This includes shifting light from near vision to far vision for larger pupil sizes, but also to prioritize intermediate vision over near vision for larger apertures, and even to remove or spread light from near vision even when it cannot be redistributed to other usable gratings. The latter is done minimize problems with halo. Further reasoning of the importance of adaptivity in diffractive lenses can be found in WO2022177517A1. In said document, adaptivity is achieved by changing the shape of the diffractive unit cell as a function of aperture, but it also clearly shows that there exists a limit for that type of tuning for lenses having usable orders on both sides of the 0^th order. The present invention discloses, among other things, a way to further increase adaptivity in already adaptive lens designs, but also how to introduce adaptive behavior in other lens designs with usable diffractive orders on both sides of the 0^th order.

For small pupil sizes the pinhole effect is important to consider. A constriction of the pupil increases the depth of focus of the lens, which for tiny pupils generally provides a relatively good vision at all distances even with a lens that is providing only a single focus. Many modern multifocal and enhanced depth- of-focus (EDOF) lenses takes advantage of this effect by allowing the light provided by the lens to be dominated by intermediate or near vision. The central argument of this practice is that if this is provided in the center of the lens, it is expected to work well enough for the user in photopic conditions, due to large depth of field for tiny apertures, while this intensity provided for near and/or intermediate vision can be of use especially for mesopic conditions with slightly larger pupil sizes. However, the addition of near and intermediate powers is important for mesopic conditions to enable viable vision for most ranges. Usually, it is desirable in mesopic conditions to keep the near vision stronger than the intermediate vision to provide a good reading capability without the use of glasses, but in scotopic vision the near vision stops being useful and can instead have a deleterious effect.

Foremost idea given in the teaching as part of the present disclosure is that it is advantageous to vary the pitch of a diffractive grating on the lens over the aperture of said lens when the aperture-dependent change in power is fully, or in cases partially, counteracted by a different mechanism in the lens. Said counteracting mechanisms could be multiple. According to one embodiment, said counteracting mechanism can be configured such that a power shift is effectuated by the diffractive structure itself. This is a first type of counteracting mechanism. A given diffractive pattern will cause an offset for small diameters for all non-0^th order diffractive orders. The magnitude of said offset is a function of the horizontal shift of the diffractive grating. Shifting the diffractive grating horizontally in order to tune intensity distribution over the usable diffractive orders is applicable, however this shift causes a variation of power of the non- zeroth order diffractive orders for a central portion of the lens. To avoid misunderstanding, it should here be noted that a horizontal shift simply means a choice of starting position of the diffractive unit cell at the optical axis. Any point in the diffractive unit cell can be arranged to coincide with the optical axis, but different choices will have dramatical effect on the behavior of the lens. When a starting point is different between two designs using the same diffractive unit cell, it is said the grating is horizontally shifted for different designs. Overall lens efficiency can be much improved by compensating for this. A second way to construct a counteracting mechanism is through a change in refractive power. In this case, said change in refractive power may be in the form of a purposefully added spherical aberration or a direct change of the lens curvature as a function of the aperture, i.e. distance from the optical axis.

These two different types of counteracting mechanisms function differently. The former type of counteracting mechanism aligns all non-O^th orders to increase efficiency for a given portion of the lens for e.g. far and near vision. The latter type of counteracting mechanism uses an arrangement to increase efficiency or maintain efficiency at a high level for far vision, while enabling a broadening for other foci, thus sacrificing intensity at those foci for at least some certain pupil sizes.

There exist examples in the art which claim to utilize combination of several pitches. EP2377493B1 describes a trifocal lens based on a combination of two different pitches. However, as both different pitches are synchronized there is no deviation of placement of the actually repeated period. US10747022B2 describes different multifocal lenses with varying number of foci, utilizing sawtooth gratings combining different pitches into one grating. However, as all different pitches are synchronized there is no deviation of placement of the actually repeated period. US2021196452 discloses sawtooth diffractive lenses where each so called echelette in the sawtooth grating has a different width in r²-space than any other echelette in a set of echelettes, where each set is repeated two or more times, that is, the grating can also be described as one regular diffractive grating having a longer period and several peak per period. There are examples where sinusoidal-like patterns with a pitch in r²-space that increases with increasing aperture are used in the prior art. This is usually done to enhance the depth of field of a monofocal base. US2004230299 describes monofocal lenses with an added sinusoidal pattern, to provide an extended depth of field. The sinusoidal patterns illustrated as part of the teaching of said document lack constant pitch in r²-space. It is, in effect, is a diffractive sinusoidal grating with additive power that is changing as a function of the radius, but it is used to not to create a multifocal lens and the changing power is not counteracted by a second mechanism.

W02019021184A1 discloses multifocal lenses using morphed sinusoidal phase shift structures in a central portion of the lens to provide far vision and an extended depth of field for closer vision with lower contrast. The proscribed patterns are shallow gratings with varying height and pitches that, in r²-space, are increasing strongly with increasing aperture. If the pitches were to be understood as a regular diffractive lens e.g., the example lens described by the data in Table 1 would provide diffractive first order power, calculated from the pitches, that vary from above 3.5D to below 0.5 from center to periphery. The document proscribes the use of a refractive base that coincides or nearly coincides with far vision of the patient.

The change of refractive power to be used as a counteracting mechanism can be calculated in several interchangeable ways. Often a lens designer will use the standard equation for lens sag of an aspheric lens. This standard equation, as seen in Equation 1, gives the sag zfor each distance rfrom the optical axis, determined by the radius of curvature R, the conic constant K, and the higher order constants oc4, ae ...: to calculate the refractive base for a diffractive lens. Using this equation one way to create a counteracting mechanism is to choose the correct 4^th order constant, oc4. It can be tuned as a function of lens aperture for further optimization. Constants a/for i greater than 4 can also often be used to further tune the lens behavior. An alternative way is to use a conic constant, K, or a combination of conic constant and higher order constants. A further alternative approach is to recalculate r in the sag equation for each aperture to directly create a change in refractive power to counteract the change in diffractive power at any given lens aperture. A recalculated r can also sometimes advantageously be supplemented with changes to conic constant and higher order constants. What is being proscribed as part of the second type of counteracting mechanism is any lens curvature that counteracts the change in diffractive power for the specific diffractive order in question.

Diffraction efficiency is an important concept when comparing different diffractive multifocal lenses. Typically, when diffraction efficiency is discussed in the literature what is considered is the portion of the incoming light that is distributed to the peaks of the desired diffraction orders. For the very practical task of detailed design of diffractive lenses a slightly higher degree of specificity turns out to be needed. Because of this, two different measurements for diffraction efficiency will be used in this document hereinafter. First, peakbased diffraction efficiency, is here can be calculated by summation of light intensity in each peak. Calculated it is strictly not an efficiency, but it is an important tool for optimization. For very similar results this could be calculated as the portion of energy going into the desired peaks. Second, focal regionbased diffraction efficiency is the portion of the incoming light that ends up within a certain focal rage. Peak-based diffraction efficiency is important because relates to highest attainable acuity for the specific ranges, but it does not take into account light spread in between two contiguous diffraction orders. Because of this focal region-based diffraction efficiency is important to assess the total amount of light directed towards the desired focal range. Importantly, intensity in between two desired orders can contribute to increase continuity of vision as well as it removes energy that could create positive dysphotopsias.

Figure 1 shows, in a simplified manner, the anatomy of the human eye 10, for the purpose of illustrating the present disclosure. The front part of the eye 10 is formed by the cornea 11, a spherical clear tissue that covers the pupil 12. The pupil 12 is the adaptable light receiving part of the eye 10 that controls the amount of light received in the eye 10. Light rays passing the pupil 12 are received at the natural crystalline lens 13, a small clear and flexible disk inside the eye 10, that focuses light rays onto the retina 14 at the rear part of the eye 10. The retina 14 serves the image forming by the eye 10. The posterior cavity 15, i.e. the space between the retina 14 and the lens 13, is filled with vitreous humour, a clear, jelly-like substance. The anterior and posterior chambers 16, i.e. the space between the lens 13 and the cornea 11, is filled with aqueous humour, a clear, watery liquid. Reference numeral 20 indicates the optical axis of the eye 10.

For a sharp and clear far field view by the eye 10, the lens 13 should be relatively flat, while for a sharp and clear near field view the lens 13 should be relatively curved. The curvature of the lens 13 is controlled by the ciliary muscles (not shown) that are in turn controlled from the human brain. A healthy eye 10 is able to accommodate, i.e. to control the lens 13, in a manner for providing a clear and sharp view of images at any distance in front of the cornea 11, between far field and near field.

Ophthalmic or artificial lenses are applied to correct vision by the eye 10 in combination with the lens 13, in which cases the ophthalmic lens is positioned in front of the cornea 11, or to replace the lens 13. In the latter case also indicated as aphakic ophthalmic lenses.

Multifocal ophthalmic lenses are used to enhance or correct vision by the eye 10 for various distances. In the case of trifocal ophthalmic lenses, for example, the ophthalmic lens is arranged for sharp and clear vision at three more or less discrete distances or focal points, often including far intermediate, and near vision, in Figure 1 indicated by reference numerals 17, 18 and 19, respectively. Far vision is in optical terms when the incoming light rays are parallel or close to parallel. Light rays emanating from objects arranged at or near these distances or focal points 17, 18 and 19 are correctly focused at the retina 14, i.e. such that clear and sharp images of these objects are projected. The focal points 17, 18 and 19, in practice, may correspond to focal distances ranging from a few meters to tens of centimeters, to centimeters, respectively. Usually, ophthalmologists choose lenses for the patients so that the far focus allows the patient to focus on parallel light, in the common optical terminology it is that the far is focused on infinity. Ophthalmologists will, when testing patients, commonly measure near vision as 40 cm distance from the eyes and intermediate vision at a distance of 66 cm, but other values can be used.

The amount of correction that an ophthalmic lens provides is called the optical power, OP, and is expressed in Diopter, D. The optical power OP is calculated as the inverse of a focal distance f measured in meters. That is, OP = 1/f, wherein f is a respective focal distance from the lens to a respective focal point for far 17, intermediate 18 or near vision 19. Figure 2 generally demonstrates a multifocal ophthalmic aphakic intraocular lens known in the art. Diffractive lenses for ophthalmology applications make use of a combination of a diffractive grating and a refractive lens body.

Figure 2a shows a top view of a typical ophthalmic multifocal aphakic intraocular lens 30, and Figure 2b shows a side view of the lens 30. The lens 30 comprises a light transmissive circular disk-shaped lens body 31 and a pair of haptics 32, that extend outwardly from the lens body 31, for supporting the lens 30 in the human eye. Note that this is one example of a haptic, and there are many known haptic designs. The lens body 31 has a biconvex shape, comprising a center part 33, a front or anterior surface 34 and a rear or posterior surface 35. The lens body 31 further comprises an optical axis 29 extending transverse to front and rear surfaces 34, 35 and through the center of the center part 33. Those skilled in the art will appreciate that the optical axis 29 is a virtual axis, for the purpose of referring the optical properties of the lens 30. The convex lens body 31, in a practical embodiment, provides a refractive optical power of about 20 D.

In the embodiment shown, at the front surface 34 of the lens body 31 a periodic light transmissive diffraction grating or relief 36 is arranged, comprised of rings or zones extending concentrically with respect to the optical axis 29 through the center part 33 over at least part of the front surface 34 of the lens body 31. The diffraction grating or relief 36 provides a set of diffractive focal points. Although not shown, the diffraction grating or relief 36 may also be arranged at the rear surface 35 of the lens body 31, or at both surfaces 34, 35. In practice, the diffraction grating 36 is not limited to concentric circular or annular ring-shaped zones, but includes concentric elliptic or oval shaped zones, for example, or more in general any type of concentric rotational zone shapes. In practice the optic diameter 37 of the lens body 31 is about 5 - 7 mm, while the total outer diameter 38 of the lens 30 including the haptics 31 is about 12- 14 mm. The lens 30 may have a center thickness 39 of about 1 mm. In the case of ophthalmic multifocal contact lenses and spectacle or eye glass lenses, the haptics 32 at the lens body 31 are not provided, while the lens body 31 may have a plano-convex, a biconcave or plano-concave shape, or combinations of convex and concave shapes. The lens body may comprise any of Hydrophobic Acrylic, Hydrophilic Acrylic, Silicone materials, or any other suitable light transmissive material for use in the human eye in case of an aphakic ophthalmic lens.

Figure 2c illustrates an adaptive lens made according to the teachings of PCT/TR2021/050154. As is explained in that document a diffractive grating can be horizontally shifted to tune diffraction efficiency and intensity distribution. The intensity distribution is then further tuned by varying the shape of each period of the grating. The upper part of Figure 2c illustrates the diffractive profile of the lens. The lower part shows the modelled intensity distribution of said lens, assuming a base refractive power of 20D and a refractive index of the lens material of 1.525. This graph shows the intensity at different apertures. The light intensity is expressed in arbitrary units, but the exact same arbitrary scale will be used for all graphs in this document showing absolute simulated intensity. The examples are calculated using MATI_AB^TM-based simulation software. Those skilled in the art will appreciate that these optical powers or focal points may differ for actual lenses, dependent on the target focal points. This lens is optimized to provide a large intensity for far vision around 18.2D and overall as high peak-based diffractive efficiency. This lens has 13 diffractive rings, if calculated as fully formed peaks. Figure 2d illustrates an adaptive lens made according to the teachings of PCT/TR2021/050154. As is explained in that document a diffractive grating can be horizontally shifted to tune diffraction efficiency and intensity distribution. The intensity distribution is then further tuned by varying the shape of each period of the grating. The upper part of Figure 2d illustrates the diffractive profile of the lens. The lower part shows the modelled intensity distribution of said lens, assuming a base refractive power of 20D and a refractive index of the lens material of 1.525. This lens is optimized for high focal region-based diffraction. The only difference between the two lenses is that the grating in Figure 2d is shifted 11% of a period compared to the grating in Figure 2c. The most notable difference in the intensity distributions compared to the lens described in Figure 2c is that in the present figure the absolute diffractive power for small apertures is lower. Since this lens makes use of a symmetric diffraction grating with -1^st order being responsible for far vision and the +l^st order being responsible for near vision this means that in absolute terms the far power for small apertures is higher than the desired value, while the opposite is true for near power. With increasing aperture, the power moves close to the nominal values. This arrangement increases total light efficiency, however displays other drawbacks. If one defines the region of usable light as between 17.7D and 22.3D the lens in Figure 2d has a modelled increase in total light efficiency of 3.9% at a 6 mm aperture and an increase of 3.4% at a 3 mm aperture over the lens in Figure 2c. This, however, comes at a cost of a reduced sum of peak intensities of 2.9% at a 3 mm aperture and 2.7% at a 6 mm aperture. The intensity of the far peak is decreased with 8.4% at a 3 mm aperture, and 5.1% at a 6 mm aperture. Because of this the lens presented in Figure 2c would usually be preferred. But it would be much preferred to have a lens that can in a better way combine the total light efficiency with the sharp peaks for apertures of 3 mm and below. This lens has 13 diffractive rings, if calculated as fully formed peaks. Those skilled in the art will appreciate that the lens body 41 may comprise a plano-convex, a biconcave or plano-concave shape, and combinations of convex and concave shapes or curvatures (not shown).

Figure 3a shows a top view of an ophthalmic multifocal aphakic intraocular lens 50, working in accordance with the present invention, and Figure 3b shows a side view of the lens 50. The difference over the prior art, exemplified in Figure 2 are in the optics of the lens. The lens body 54 has a biconvex shape, comprising a front or anterior surface 52 and a rear or posterior surface 53. The skilled person would know that for some embodiments one or both of the anterior surface 52 and the posterior surface 53 might be concave or planar, depending on the refractive baseline required for a specific application. In a specific embodiment of the invention the lens body, in accordance with the present disclosure, the anterior surface 52 is formed as a summation of a multifocal diffractive profile with varying pitch 51 and a refractive profile. When constructing and analyzing the lens, the full refractive profile should be viewed as a summation of a refractive baseline on the one hand, and on the other hand a corrective profile with varying power 55, shown in Figure 3f. The varying power of the corrective profile is configured to counteract the change in diffractive power with respect to the diffractive order responsible for providing far vision. The refractive baseline is substantially monofocal and any substantially monofocal design can be used. It is of course well-known that any monofocal design takes into consideration both the anterior and posterior sides. The point being that any useful monofocal design can be used to define the refractive baselines of the current invention. The example lens shown here is constructed such that, for a design wavelength, the -1^st diffractive order of the multifocal diffractive profile with varying pitch 51 contributes usefully to the far vision of the lens, the 0^th order of the symmetric multifocal diffractive grating contributes usefully to the intermediate vision of the lens, and the +l^st diffraction order contributes usefully to near vision. In other embodiments according to the patent the number of focal points is a higher number, such as 4, 5, or 7. Some advantageous configurations makes use of diffractive orders that are not symmetrically arranged around the 0^th order, for example can it be advantageous to use the set of orders (-1, 0, +1, +2) or (-1, 0, +1, +2, +3). Note that the anterior surface 52 is drawn with a refractive baseline with larger radius, i.e. lower optical power, than typical, this is done purely for illustrative purposes, to keep the diffractive component visible.

It is obvious to the skilled person that this is only one possible configuration. It is possible, for example, to place the diffractive part of the optics on the posterior side, to distribute the diffractive grating over both sides, to separate the corrective profile with varying power 55 and the multifocal diffractive profile with varying pitch 51, so that one is placed on the posterior side 53 and the other on the anterior side 52, or superposition the diffractive grating to either side of a plano-convex or plano-concave lens. When a diffractive pattern is said to be combined with a refractive surface it can be interpreted as a superposition on one side of the lens, or that they are combined by inhabiting one side of the lens each.

The shape or height profile of the refractive baseline for any of the portions of the lens may be selected among a plurality of continuous refraction profiles known from monofocal lenses, such as spherical or any variant of aspherical profiles. Most modern intraocular monofocal lenses are aspherical with the asphericity chosen to either be neutral and thus causing no further aberration in the eye, or they are purposefully induced to, given the optics of an average eye to exhibit negative spherical aberration to neutralize, fully or partly, the positive spherical aberration usually present in the human cornea. Those choices should all be seen as different ways to create monofocal bases. The invention described in the present disclosure can be incorporated with any such monofocal base. The manufacturing of refractive of diffractive surfaces can be carried out by any of laser micro machining, diamond turning, 3D printing, or any other machining or lithographic surface processing technique.

Present invention describes a way to create lens that substantially maintains the desired features of the prior art lens in Figures 2c, 2d, and 4a, and that increases diffraction efficiency, significantly increases the amount of light usable for the human eye and has several additional advantages.

Figure 3c shows a trifocal diffraction grating of a lens made according to the present invention less the full refractive profile. This is a diffraction grating based on a base grating that has a shift between the ones for the gratings in Figure 2c and 2d, but with a pitch that is changed as a function of lens radius, in according with the present invention. The grating in Figure 2d is shifted 11% of a period compared to the grating in Figure 2c. The grating in Figure 3c is shifted 8% compared to the grating in Figure 2c. By applying the present invention this profile was further tuned to find a good compromise between peak-based and focal region-based diffraction efficiency while increasing the desired adaptive behavior with especially weaker near vision intensity for large pupil sizes. This lens has 11 diffractive rings, if calculated as fully formed peaks. That means that it has two fewer rings than the two prior art lenses in Figures 2c and 2d, while maintaining the same add power and having a higher quality far vision.

Figure 3d illustrates the diffraction grating according to the invention shown in Figure 3c with the grating plotted in quadratic space. In standard trifocal lenses the pitch of the diffractive grating would be, as well-known, fixed. As can be seen in the figure the quadratic space pitch of the grating is increasing with increasing lens radius. The change rate is also dependent on the radius.

Figure 3e illustrates the change in pitch of the diffractive grating as a function of lens radius of the example lens according to the invention in Figures 3a and 3b. The pitch is expressed in quadratic space. This explains further the construction of the diffractive grating in Figure 3c. In this specific embodiment, there are two distinct zones of changing pitch. The first one is between the optical axis 29 and a lens radius of about 1.5 mm. Here the pitch of the diffractive grating is increasing to compensate for the structural shift in power. The magnitude of this shift is determined by the shape of the grating and the choice of horizontal offset. This is further illustrated by Figures 2c-d. Note that for some other choices of horizontal offset of the grating the shift in power will be in the opposite direction. To compensate for this one would construct a lens with a pitch that decreases with increasing radius. Such a choice is also a valid and useful choice according to the present invention. The second zone of increasing pitch is in between 1.6 mm and the edge of the optical part of the lens. To keep the power for the prioritized diffractive order (in this case corresponding to far vision for a user) fixed with changing pupil size this change in diffractive power needs to be compensated (counteracted) by a change in power of the refractive profile.

The lens design described in Figures 3a through 3h is made for a refractive index of 1.525 and an assumed design wavelength, A, of 550 nm and a target Far power, P, of about 1.8D below that of the refractive base. For the period in quadratic space, T, then for this grating, Equation 2 gives: For a standard case of diffractive lenses, this would result in a diffractive lens with static grating pitch in quadratic space of 0.611 mm². In the currently discussed lens design made as part of the present invention, this pitch is attained at a radius of 1.64 mm. Even though the pitch is changed, the optical power of the -1^st diffraction order remains substantially the same. The plateau between 1.5 mm and 1.6 mm has a pitch of 0.606. Such a design in a lens according to the disclosure can be achieved without any sophisticated software, to find a fully optimized design it is required to have a way to model the diffraction grating, provided that grating modelling is not difficult. The change in power is calculated for each point of lens, so that the effective power changes gradually within each period, instead of stepwise with each period. It should also be noted that, while the change in pitch here is substantially linear within each region, this may not always be the best choice. In fact, it can often be advantageous to vary the pitch in one of a number of other ways. For the case of the structural counteracting mechanism, it is often advantageous to vary the pitch to be more exactly tuned to the structural power change. For the case of the use of change of refractive power as a counteracting mechanism, the choice of a linear change is arbitrarily chosen, whereas other choices are often advantageous.

Figure 3f illustrates the corrective profile of the lens of the anterior surface 52. To construct the full refractive profile of a lens according to the invention the corrective profile is summed with refractive baseline. The refractive baseline of a lens consists of a spherical component as well as a possible additional aspherical component. The refractive baseline defines the curvature that would be use for a corresponding monofocal lens. When designing monofocal lenses there are several options, historically purely spherical lenses have often been, also for IOLS. As discussed hitherto, selection of the monofocal base may be made from spherical lenses, as well as a large array of aspherical lenses. Any such design can be chosen for the refractive baseline to use for the present invention.

The corrective profile shown in Figure 3f is in this case zero up to about 1.6 mm from the optical axis (radius of 1.6 mm), then it increases to compensate for the change in power caused by the change of pitch of the diffractive grating. Such a change in refractive power is in this specific not needed for the inner 1.5 mm of the lens radius, as the change in diffractive pitch here is counteracted by the structural counteracting mechanism. Note that while in this case the counteracting mechanism based on structural properties of the diffractive grating and the counteracting mechanism based on change of refractive power are separated, they can be combined by superposition and applied partly or fully to the same part of the lens.

Figure 3g shows the profile of the anterior surface 52, less the refractive baseline. The profile in this figure is the sum of the multifocal diffraction profile with varying diffractive power 51 profile in Figure 3c and the corrective profile with varying power 55 in Figure 3f.

Figure 3h illustrates the modelled light intensity distribution of a lens using the diffractive lens described in Figures 3c-3g, made according to the invention. The lens is modelled assuming a refractive base of 20D. The -1^st diffractive order provides in this case light for far vision for a user at about 18.2D, the 0^th order provides intermediate vision slightly below 20D, and the +l^st order provides near vision at about 21.8D. This lens design is intended to have three usable diffractive orders, corresponding to far, intermediate, and near vision, respectively, so that the lowest usable diffractive order corresponds to far vision and the highest usable order corresponds to near vision. Usually, a focus is considered usable if the MTF is above 0.1 at 50 Ip/mm for at least some aperture of 2 mm or larger. In this the lowest peak, the intermediate peak has an MTF above 0.1 even for 100 Ip/mm (for apertures of 2 mm and larger) and about 0.16 for the 3 mm aperture. For larger apertures it is even higher. It should be said that MTF values (at 50 Ip/mm) below 0.1 can be of use to a person and can advantageously be used in design to provide some functional vision and some additional continuous vision, but it is a limit that is often practically used to distinguish between an explicitly provided vision and something that might provide functional vision in some patient, but not all.

Compared to the prior art this lens combines a very strong preferred diffractive order, here used to provide far vision, with a strengthened and improved adaptive behavior with especially a near vision that decreases dramatically in intensity for lens apertures above 3 mm (1.5 mm and above from the optical axis). Compared to the diffractive lens described in Figure 2c this lens has a total light efficiency that is 3.3% higher at a 3 mm aperture, and 2.9% higher at 6 mm. The peak-based diffraction efficiency intensities are 1.3% higher at 2 mm, equal at 3 mm, and 21.7% lower at a 6mm aperture. The far intensity is 2.6% lower at a 3 mm aperture, and 5.9% higher at a 6mm aperture. The increased light efficiency at 3 mm is due to the change in pitch counteracted by the structural properties of the diffractive grating. This leads to a much- improved overall performance for the lens in terms of both focal region-based and peak-based diffraction efficiency when compared to the lenses demonstrated in Figures 2c and 2d. The 2.6% drop in far intensity at a 3 mm aperture is a compromise, but a small one. For periphery of the lens the intensity of the +l^st order, responsible for near vision is strongly decreased, which is desired. The near peak intensity is decreased with 45.6% compared to the lens in Figure 2c. Note that the lens in Figure 2c already is an adaptive lens, meaning that the near intensity is decreasing in relative terms with increasing aperture. Also note that since a 6 mm aperture in this case corresponds to scotopic conditions, the large drop in especially the near vision is a highly desired feature.

Disclosed lens also has decreased halo prevalence. Halo is considered the foremost major problem with modern multifocal diffractive intraocular lenses. To understand the problem of halo, one needs to consider that halo is mostly an issue in scotopic conditions (presupposing a large pupil). The problem of halo in an intraocular lens can be predicted by three main parameters: the portion of light not focusing withing the useful focal region, the highest intensity peaks outside the usable range (especially the peaks closest to the usable range of interest), and the intensity of the near vision for large pupils. Large portion of useful light decreases halo, high intensity peaks outside the usable range increases halo effect, and a strong near intensity for large pupils increases halo effects. The lens described in Figures 3a-h have compared to the two prior art lenses in Figures 2c and 2d higher focal region-based efficiency, lower peaks outside of the usable range, and a much lower near intensity for apertures of 4.5 mm and larger. It is important to understand that the lower intensity at the near (and to some extent the intermediate peak) doesn't mean that this light is lost, instead it is spread out towards optical power close to the diffractive order responsible for far vision.

Figure 3i contains measurements of a lens constructed according to the patent. The lens is very similar to the lens described in Figures 3a through 3h, but with a different refractive base and with a diffractive grating adapted for a lens with a refractive index of 1.4618. The -1^st diffractive order provides in this case light for far vision for a user at about 18.2D, the 0^th order provides intermediate vision slightly below 20D, and the +l^st order provides near vision at about 21.7D. The two measurements are carried out simultaneously on one lens with a physical optical bench measurement (the equipment used was the PMTF machine from company Lambda-X, using Eye model 1 according to ISO 11979- 2). The upper part of the figure consists of the data for 50 line pairs per millimeter (Ip/mm), while the lower part consists of the data for 100 line pairs per millimeter. These measurement results confirm the many of the desired advantages with the invention: The peak power of the far around 18.2D is kept stable in terms of power for all measured apertures, the MTF of the near focus around 21.7D is increasing up to around a 3mm pupil and is very rapidly decreasing for larger pupils, and the intermediate peak is broadened compared to the prior art. The lens measured in Figure 3i has three usable foci.

According to Figure 4a, the diffractive profile at the top shows a profile that is optimized for minimum light intensity being lost outside of the usable range (between the outer bounds of far and near vision). The upper profile in Figure 4a is made according to prior art. The lower profile in Figure 4a is made according to the patent. The corresponding modelled intensity distribution of the profiles in Figure 4a can be found in the upper and lower intensity graphs, respectively, in Figure 4b. For both designs the -1^st diffractive order provides in this case light for far vision for a user at about 18.2D, the 0^th order provides intermediate vision slightly below 20D, and the +l^st order provides near vision at about 21.8D. The three diffractive orders -1, 0, and +1 are intended to be usable. However, for small apertures the additional power, in absolute terms, of the diffractive orders responsible for the far and near vision are too small, that is they are close to the 0^th order. In the central part of the lower profile, made according to the patent, the pitch of the profile is higher than that in the profile above. With increasing aperture, it gradually becomes identical to that of the profile above. The upper and lower intensity graphs in Figure 4b relate to the upper and lower diffractive profile, respectively, in Figure 4a. It is clearly visible in the absolute intensity graph that for the profile made according to the patent the power of the peaks responsible for far and near vision, respectively, is more stable with changing aperture. Having more stable peaks means higher intensity. This is an important result for lens design. This improvement is reached with very small losses to focal region-based diffraction efficiency while keeping the resulting optical powers constant. In the lower profile in Figure 4a, a higher absolute diffractive is chosen addition is chosen. The space of diffractive zones is then decreasing with increasing aperture, this decrease of power is, however, counteracted by an increase of absolute diffractive power. Because of this both the near and the far powers, respectively, ends up exactly lining up at the same respective power for each aperture in the profile made according to the patent.

The two diffractive lens profiles in Figure 4a are constructed for a lens material with a refractive index of 1.4618.

The role of the present invention in the embodiment of the invention described by the lower portion of Figures 4a and 4b, respectively, could be said to harmonize the add powers of the center of the lens with the add power of the rest of the lens. The counteracting mechanism in the lower design is the structural property of the diffractive grating itself. This is the same design principle that is used for the central 1.5 mm of the lens profile in Figure 3g, and explained in detail in Figures 3a through 3i. This embodiment of the present invention presents a way to design for a better compromise between total light efficiency and maximum peak intensity for the main desired peaks. However, in this embodiment the near intensity peak around 21.8D is not as radically decreasing for large apertures, and the undesired peak around 23.6D is sharp for the 4.5mm aperture, and not attenuated as the corresponding peak in Figure 3h is. In Figure 4a both the prior art lens and the lens made according to the present have 13 diffractive rings each.

The two diffractive profiles in Fig. 4a have the same lateral position, measured as horizontal shift in portion of a period, chosen for high light efficiency. The central trough (around the optical axis) is slightly smaller in the lower profile due to a higher pitch, but functionally this is very different from a lateral shift. Without the insight of the present invention the efficient placement of the grating used for both diffractive profiles in Figure 4a could not have been used for a trifocal lens, due to power uniformity being too low. Thus, the present invention broadens the scope of profile types that can be used for commercially viable lenses as well as outcomes that can be reached.

Figure 5a demonstrates a lens profile for a lens made according to the present invention, shown here less the refractive baseline. This profile consists of diffractive profile with changing pitch summed with a corrective profile. The pitch of the diffractive grating in r² space increases with increasing aperture, leading to decreasing absolute diffractive power. This decrease of diffractive power will with increasing aperture increase the far power, provided by lowest usable diffraction order (-1), and decrease the optical power of the highest usable diffraction order (+1). However, as per the invention this is counteracted for the preferred order, the -1^st order, by the changing power of the corrective profile, clearly visible in the profile as the dominating curvature. In this specific case the change of pitch in the diffractive profile as well as the change of optical power in the refractive profile both start at the center of the lens. The corrective profile can be calculated by changing the lens curvature as a function of the aperture correct for the change of power in the diffractive grating. Alternatively, the corrective profile can simply be implemented as fourth order aberration, oc4, (spherical aberration) from equation 2. These two methods both work well. A third option is finding a conic constant that changes the power in an appropriate way, this is also proven to work. For the best performance small changes can be made onto any of these methods with the use of modelling software. This lens has 9 diffractive rings, if calculated as fully formed peaks, showcasing that a rather dramatic decrease of ring number is possible for highly functional multifocal lenses. Such lenses could also be used as EDOF lenses.

Figure 5b shows the intensity distribution of the lens in Figure 5a. The lens described in Figure 5a and 5b has three usable orders, -1, 0, and +1, providing vision for a user at, respectively, around 18.5D, 19.8D, and 21.3D. designs the -1^st diffractive order provides in this case light for far vision for a user at about 18.2D, the 0^th order provides intermediate vision slightly below 20D, and the +l^st order provides near vision at about 21.8D. The peak at 18.5D provides the far vision in this lens, and the most striking quality of this lens is that with increasing aperture the decreasing diffractive power is perfectly matched with the negative spherical aberration so that the order responsible for the far vision is well-matched and creates a quality intensity peak at all apertures, while the powers for the 0^th and +l^st diffractive orders are intentionally unmatched. It can be noted that in this specific configuration the powers of the 0^th order and the +l^st are slightly lower than those of the intermediate and near vision, respectively. This creates a new type of diffractive extended depth of focus lens where the far peak is sharp, but the other orders are helping to create a more continuous vision. For EDOF lenses the highest optical powers are often chosen to be closer to far vision than in other multifocal lenses. Since the light is more spread out in an EDOF design this might be a necessary economy if light energy. The profile in Figure 5a has the profile placement chosen so that there is mostly a continuity of vision between far and intermediate vision, but with a point of very low provided intensity around 20.5D. The lens described by Figure 5a and Figure 5b is meant to provide three usable orders. If the 5b is compared, aperture by aperture to the upper figure in 3i the relationship between the peak can be estimated to be similar. It is then easy to see that all three peaks in Figure 5b can be expected to provide peak MTF well above 0.1 measured at 50lp/mm for some apertures at 2 mm or larger.

Figures 6a and 6b describe a lens according to the present invention and its intensity distribution. The lens in Figure 6a is very similar to that of Figure 5a. Shown here is the diffractive profile summed with a corrective profile. The main difference here is that the horizontal shift of the diffractive grating is changed to provide continuous vision between the intermediate and near power and an intensity dip between the far and intermediate power. As the lens in Figure 5a this lens has nine diffractive rings.

Figure 6b shows the intensity distribution of the lens in Figure 6a. Parts of the design is very similar to that of the lens described in Figure 5a and Figure 5b, namely that with increasing aperture the decreasing diffractive power is perfectly matched with the negative spherical aberration so that the -1^st order responsible for the far vision is well-matched and creates a quality intensity peak at all apertures, while the powers corresponding to the 0^th and +l^st orders are intentionally unmatched. This creates a new type of diffractive EDOF lens where the far peak is sharp, but the other orders are helping to create a more continuous vision. However, the profile in Figure 6a makes use of a profile that is horizontally shifted compared to that in 5a and has one of the peaks (diffractive ring) of the diffracting grating coinciding with the optical axis. This choice creates a sort of continuity of vision between 0^th and +l^st orders, with a point of lowest provided intensity between the -1^st (far vision) and 0^th order. The specific lens design described by Figure 6a and Figure 6b is meant to provide only two usable orders by the definition of a usable order having an MTF of at least 0.1 measured at 50lp/mm for apertures of 2 mm or larger. The far power provides vision around 18.6D and the highest usable order provides vision around 21.3D. While there is no usable focus between the highest and lowest usable orders, there is a continuity of vision for much of this region. For many patients, this would mean that this lens provides functional vision for most distances, except for distances that are very near. It can also be seen in Figure 6b that the undesired peaks are very low, so one would expect a significantly smaller problem with halo than in most other lenses with diffractive gratings.

The effect of choice of the horizontal shift (which controls the shape of the central part of the lens) can be used to similar effect on the lenses in Figure 4a.

Figure 6c shows the diffractive profile in Figure 6a plotted in the r² space. It can be clearly seen here that the period, in quadratic space, is increasing with increasing aperture.

Figure 7a illustrates the profile of a quadrifocal lens made according to the present invention, that is a lens providing four diffractive orders. This specific lens is designed to have a refractive power of 20D and a refractive index of the lens material of 1.54. This profile shows the summation of the diffractive profile and the refractive profile, in other words the full lens profile less the refractive baseline. The diffractive profile used here is a sinusoidal, continuous profile intended to split the light into four contiguous orders. The corrective profile becomes non-zero at a distance of 1.6 mm from the optical axis and then decreases power continuously with increasing aperture. The period in quadratic space of the quadrifocal diffractive grating increases over the same part of the lens. It can also be seen in Figure 7a that the shape of the diffractive profile changes as a function of distance to the optical axis. This change is made to further increase light being directed towards far vision.

Figure 7b shows the relative intensity distribution of the lens in Figure 7a. The relative intensity graph compares the intensities between different powers for each modelled aperture. The absolute intensities of the highest intensity order is, however, very similar to that shown in Figure 6b. The lens described in Figure 7a and 7b has four orders, -1, 0, +1, and +2, providing vision for a user at, respectively, around 18.8D, 19.95, 21.3D, and 22.4D. -1^st order corresponds to far vision and is kept stable and strong for each aperture. The 0^th order has a low relative intensity and might in actual realization of this lens be usable or non-usable, depending on implementation details. The usable +l^st order helps provide intermediate vision, and the usable +2^nd order corresponds to near vision. It can be understood from Figure 7b that for the 4.5 mm and 6 mm lens apertures the relative intensity directed towards foci other than the one corresponding to far vision decreases significantly, while far visions is kept stable. A lens with this intensity distribution can combine a very strong far with a continuous vision from about 1 m to close reading distance. For photopic and mesopic vision a very strong near vision can also be provided.

Figure 8a illustrates the profile of a trifocal lens using a binary diffraction pattern, made according to the present invention. Binary ophthalmic lenses in the prior art provide intensity from one highest and one lowest diffraction order, typically having equal intensity and then a 0^th order, the intensity of which can be adjusted by choosing the height of the binary pattern. The diffractive profile presented here provides a significant improvement for ophthalmic trifocal binary lenses over the prior art. The diffractive profile in Figure 8a has two separate concentric regions where the period length in quadratic space is increasing as a function of increasing aperture, which is more clearly demonstrated in Figure 8b. The profile in Figure 8b shows the summation of the diffractive profile and the refractive profile, in other words the full lens profile less the refractive baseline. The optical axis at the optical center of the lens up to a radius of 1.45 mm of is counteracted by the structure itself, as has been discussed with regards to trifocal sinusoidal lenses demonstrated in Figures 3a through 3i as well as in Figures 4a and 4b. This increase of quadratic space grating period increases intensity of both the highest and the lowest diffraction grating compared to a lens without this feature. Then, in the concentric region between 1.9 mm and the edge of the optic surface at 3 mm radius, the change in pitch is counteracted by a corrective profile to blur undesired diffractive order and reduce the peaks of the desired diffractive orders other than the lowest usable diffractive order for the periphery of the lens.

Figure 8c shows the modeled absolute intensity distribution of the lens profile in Figure 8a. This lens is designed to have a refractive power of 20D and a refractive index of 1.54. It has three usable orders (-1, 0, and +1) which provide vision at distances corresponding to far, intermediate, and near vision (18.3D, 20.0D, and 21.6D, respectively). By comparing the peaks for the 2 mm and the 3 mm apertures it can be seen that the shift in pitch in the central part of the lens is not strong enough to align the peaks completely. This current configuration is a compromise that increases the Near and Far vision compared to prior art, while still keeping the 2 mm peaks of -1^st and +l^st orders closer to the 0^th order, which improves the focal region-based diffraction efficiency. For large apertures the far vision is kept stable and sharp, while the higher orders are broadened. The +l^st order, providing far vision, is strongly decreased for larger apertures. Additionally, this lens has a continuous vision between the intermediate and near visions. A lens with this intensity distribution can combine a very strong far with a continuous vision from about 80 cm to close reading distance. This tuned binary lens is a significant improvement over the prior art for ophthalmic binary lenses.

Other variations to the disclosed examples and embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof. Same reference signs refer to equal or equivalent elements or operations.

According to an aspect of the present disclosure, an ophthalmic multifocal lens, arranged to provide far vision, and at least one other usable vision at most at a range of 1 meter, said lens having a light transmissive lens body with an optical axis and a refractive baseline that extends over at least a part of the lens body, and a diffraction grating configured to operate as an optical wave splitter, extending concentrically in radial direction, superpositioned onto at least one part of the refractive baseline, said lens further comprising at least three contiguous diffractive orders of which at least two are useful diffractive orders is proposed.

According to another aspect of the present disclosure, said useful diffractive orders are configured to comprise at least one positive diffractive order, and at least one negative diffractive order. According to another aspect of the present disclosure, said diffraction grating configured to operate as an optical wave splitter is configured to have a variable period in quadratic space.

According to another aspect of the present disclosure, said ophthalmic lens comprising at least one first concentric region wherein said variable period of said diffraction grating is configured to monotonically change in relation to the radius of the lens.

According to yet another aspect of the present disclosure, said lens comprises a preferred diffractive order.

According to yet another aspect of the present disclosure, said lens comprises at least a counteracting mechanism configured to keep power of said preferred diffractive order stable.

According to yet another aspect of the present disclosure, said at least one first concentric region is configured to span across at least two periods of said diffraction grating.

According to yet another aspect of the present disclosure, said at least one counteracting mechanism is constructed such that a shift in power is effectuated on the diffractive structure itself.

According to yet another aspect of the present disclosure, said at least one counteracting mechanism is configured to produce a change in refractive power whereby a corrective profile is engaged. According to yet another aspect of the present disclosure, said lens comprises two counteracting mechanisms.

According to yet another aspect of the present disclosure, said preferred order is arranged to provide far vision.

According to yet another aspect of the present disclosure, said at least two usable orders are selectable from the following diffraction orders: -3, -2, -1, 0, + 1, +2, +3.

According to yet another aspect of the present disclosure, said at least three contiguous orders comprise -1, 0, and +1.

According to yet another aspect of the present disclosure, the diffraction efficiency of at least one of the diffractive orders between highest and lowest useful orders is configured to, at an aperture corresponding to mesopic conditions, provide and MTF less than 0.1 measured at 50 Ip/mm.

According to yet another aspect of the present disclosure, near vision is configured to correspond to the highest usable diffraction order.

According to yet another aspect of the present disclosure, the intermediate vision is configured to correspond to the highest usable diffraction order.

According to yet another aspect of the present disclosure, said diffraction grating has a sinusoidal, continuous profile.

Claims

1) An ophthalmic multifocal lens, arranged to provide far vision, and at least one other usable vision at most at a range of 1 meter, said lens having a light transmissive lens body with an optical axis and a refractive baseline that extends over at least a part of the lens body, and a diffraction grating configured to operate as an optical wave splitter, extending concentrically in radial direction, superpositioned onto at least one part of the refractive baseline, said lens further comprising at least three contiguous diffractive orders of which at least two are useful diffractive orders, characterized in that said useful diffractive orders are configured to comprise at least one positive diffractive order, and at least one negative diffractive order, said diffraction grating configured to operate as an optical wave splitter is configured to have a variable period in quadratic space, said ophthalmic lens comprising at least one first concentric region wherein said variable period of said diffraction grating is configured to monotonically change in relation to the radius of the lens, said lens comprises a preferred diffractive order, and; said lens comprises at least a counteracting mechanism configured to keep power of said preferred diffractive order stable.

2) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 meter, as set forth in Claim 1 characterized in that said at least one first concentric region is configured to span across at least two periods of said diffraction grating.

3) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 meter, as set forth in Claim 1 characterized in that said at least one counteracting mechanism is constructed such that a shift in power is effectuated on the diffractive structure itself.

4) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 meter, as set forth in Claim 1 characterized in that said at least one counteracting mechanism is configured to produce a change in refractive power whereby a corrective profile is engaged.

5) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 meter as set forth in any preceding Claim characterized in that said lens comprises two counteracting mechanisms.

6) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 m as set forth in any preceding Claim characterized in that preferred order is arranged to provide far vision.

7) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 meter as set forth in any preceding Claim characterized in that said at least two usable orders are selectable from the following diffraction orders: -3, -2, -1, 0, +1, +2, +3.

8) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 meter as set forth in any preceding Claim characterized in that said at least three contiguous orders comprise orders -1, 0, and +1. 9) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 meter as set forth in any preceding Claim characterized in that the diffraction efficiency of at least one of the diffractive orders between highest and lowest useful orders is configured to, at an aperture corresponding to mesopic conditions, provide and MTF less than 0.1 measured at 50 Ip/mm.

10) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 meter as set forth in any preceding Claim characterized in that near vision is configured to correspond to the highest usable diffraction order.

11) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 meter as set forth in Claims 1 through 9 characterized in that intermediate vision is configured to correspond to the highest usable diffraction order.

12) An ophthalmic multifocal lens, arranged to provide far vision and at least one other usable vision at most at a range of 1 m as set forth in any preceding Claim characterized in that said diffraction grating has a sinusoidal, continuous profile.