Quadrofocal diffractive ophthalmic lenses

Abstract

An ophthalmic multifocal lens is presented, configured to provide distance vision and at least one other usable visual acuity. The lens comprises a translucent lens body having an optical axis and a refractive baseline, the refractive baseline extending to at least a portion of the lens body, and a diffraction grating configured to act as an optical splitter, extending concentrically in the radial direction and superimposed on at least a portion of the refractive baseline. The diffraction grating configured to act as an optical splitter is further configured to be continuous within at least a central 3 mm aperture, wherein the distance vision is provided by the -1st order diffraction, and the near vision is provided by the 2nd order diffraction.

Description

Technical Field

[0001] The present disclosure generally relates to ophthalmic lenses, ophthalmic contact lenses, and intraocular multifocal lenses, and more particularly to lenses having a smooth diffractive structure without discontinuities arranged to provide four diffractive orders so as to optimize human vision over different pupil diameters under various light conditions.

Background Art

[0002] Diffractive lenses for ophthalmic applications are configured as hybrid lenses in which a diffractive pattern is added to a refractive body. In many cases, one surface of the lens is purely refractive and the other surface has a diffractive grating superimposed on a refractive baseline. The refractive baseline can be spherical or can have an aspherical shape. The diffractive portion can generally be applied to either of the two surfaces of the lens, because when the diffractive pattern is combined with a refractive surface having some special feature, it generally does not matter whether they are added to the same surface of the lens or one is added to the first surface and the other is added to the second surface. At the same time, two diffractive patterns can be combined by superimposing them on one surface or by adding them to separate surfaces so that they overlap. The optical power of the lens for a particular diffractive order can be calculated by adding the refractive baseline power and the optical power of that diffractive order.

[0003] The most studied original diffractive lens is the single - focus phase - matching Fresnel lens taught by the study of Rossi et al. entitled "Refractive and diffractive properties of planar micro - optical elements" in 1995. This type of lens utilizes serrated diffractive unit cells and step heights corresponding to a phase modulation of exactly 2Π.

[0004] Most diffractive multifocal lenses available on the market today are still based on so-called "sawtooth" diffraction gratings, with the zeroth order of this grating used to provide the user with distance vision. Since distance vision is generally configured to be the lowest power usable by the eye, it is assumed that the lowest power of the usable orders is usually used for distance vision. While this sawtooth diffraction grating is the most optically efficient configuration for strictly bifocal lenses, this effect does not apply well to other multifocal lenses with more focal points. Most multifocal lenses with two or more focal points still use a configuration where the zeroth order is used to provide the user with distance vision, similar to the sawtooth diffraction grating, because it is relatively easy to design lenses that provide high-quality visual acuity at the zeroth order. Distance vision is usually preferred, especially for intraocular lenses, as the success of surgical procedures is usually judged by the functionality of distance vision.

[0005] However, recent advances have shown that designing lenses that utilize orders other than 0th order to provide distance vision, particularly lenses with simultaneously useful orders on both sides of 0th order, offers numerous significant advantages. The specific advantages derived from such designs vary depending on the various types of possible configurations. For example, binary diffraction lenses, typically utilizing -1st, +1st, and 0th order, have fewer rings and narrower grating peaks than the corresponding trifocal sawtooth lenses, but still retain abrupt transitions. Ophthalmic lenses based on binary gratings and their advantages have long been known, as demonstrated in International Publication No. 1994011765 A1. Such gratings can be either trifocal or bifocal, depending on the height of the structure. Symmetric sinusoidal diffraction gratings, i.e., sinusoidal diffraction gratings with orders evenly distributed around 0th order, are the most optically efficient gratings possible for diffraction lenses with an odd number of usable foci. These avoid abrupt transitions in the diffraction profile, improving manufacturability and biocompatibility. The latter point was originally suggested in the 2015 study by Osipov et al., "Application of nanoimprinting technique for fabrication of trifocal diffractive lens with sine-like radial profile," published in the Journal of biomedical optics 20, no.2 (2015):025008. A diffraction profile without discontinuities (sine-like lens) has several very important advantages. These include being less prone to undesirable optical phenomena such as halos, glare, and other positive dyphotopsia, having good manufacturing costs, allowing for the use of a wider variety of manufacturing techniques, and enabling continuous adjustment of the light intensity distribution on a subperiodic scale. For symmetric trifocal and pentfocal lenses (lenses with five diffraction orders), this point is discussed in detail in International Publication No. 2019020435 A1 and International Publication No. 2022177517 A1.

[0006] Asymmetric diffraction lenses, i.e., lenses with a different number of usable orders on both sides of the zeroth order, can be advantageous. Asymmetric diffraction gratings have a small relative power difference between the zeroth order and the order used for far viewing, which can be used as an advantage. Having far power close to the zeroth order reduces undesirable diopter offset in, for example, autorefractometry measurements, and chromatic aberration caused by diffraction can be selected to be smaller than in the case of lenses with symmetric gratings. A sawtooth-like asymmetric diffraction lens is exemplified in International Publication No. 2021245506. It features a steep vertical step, and no method is known for appropriately adjusting the light distribution according to the lens aperture. Increasing the number of diffraction orders increases the overall potential optical efficiency. For example, an asymmetric diffraction lens with four orders can be more efficient than a symmetric lens using three orders, and an asymmetric lens with six orders can be more efficient than the corresponding symmetric lens using five orders. Increasing the number of diffraction orders also reduces the number of diffraction rings, which often means easier manufacturing.

[0007] Symmetric sinusoidal continuous diffraction multifocal lenses can be found in the literature. International Publication No. 2019020435 A1 discloses a multifocal lens comprising a diffraction grating designed to act as an optical wave splitter for distributing light incident on the lens body at the refractive and diffraction focals. This diffraction grating has an optical transfer function that includes a continuous periodic phase profile function extending radially across the lens body. This continuous periodic phase profile function also includes an argument modulated as a function of the radial distance from the optical axis of the lens body, thereby adjusting the distribution of light incident on the lens body.

[0008] International Publication No. 2022177517 A1 discloses an ophthalmic multifocal lens having a translucent body with an optical axis and a refractive baseline extending to a portion of the lens body. It also discloses a first portion coinciding with the central region of the lens body and a second multifocal portion concentrically extending radially; this second portion further includes a symmetric multifocal diffraction grating superimposed on the baseline, covering a portion of the lens, the shape of which and the resulting light intensity distribution change with distance from the optical axis. In other words, the disclosure describes an aperture-adaptive diffraction lens having higher light efficiency and higher effective efficiency for better fit to the anatomical structure of the eye. Furthermore, it describes a method for individually shaping each period of diffraction at each aperture (and corresponding pupil diameter) to provide desired intensity distributions, for example, between far vision, intermediate vision, and near vision.

[0009] However, asymmetric lenses have several advantages, so it would be desirable to be able to form a multifocal lens having an asymmetric diffraction grating with usable orders on both sides of the zeroth order, while retaining the advantages of known sinusoidal lenses.

[0010] U.S. Patent No. 1,0993798B2 presents a multifocal diffracting lens having a sawtooth pattern utilizing four consecutive diffraction orders, wherein one of two intermediate orders is suppressed.

[0011] International Publication No. 2021245506 teaches a lens having a diffraction profile that is not explicitly claimed but is thought to have four diffraction orders (at least one on each side of the zeroth order). The diffraction profile presented utilizes a steep vertical step. This document discusses only three usable focal points: far vision, intermediate vision, and near vision.

[0012] To provide the user with sufficient visual acuity to eliminate the need for glasses, the lens must offer distance, intermediate, and near vision. In photopic conditions, especially in the presence of small pupils, complete multifocal vision with particularly strong distance vision is desired. A central aperture of a lens that provides very narrow distance vision increases the risk of diopter mismatch. A central portion of the lens that provides slightly stronger power than the intended distance vision power reduces this risk. This is particularly important because the quality of distance vision is actually the determining factor in the clinical success of cataract surgery.

[0013] Due to the well-known pinhole effect, a deeper depth of field can be achieved with smaller pupils, and a small shift in power for extremely small pupils does not have a negative impact on visual acuity.

[0014] In twilight conditions where the pupil is slightly dilated, the pinhole effect no longer applies, and for multifocal lenses intended to eliminate the need for glasses, providing strong near vision in addition to distance vision becomes crucial. Intermediate vision is also desirable to completely eliminate the need for glasses.

[0015] Due to the accommodative reflex, the human pupil constricts when viewing nearby objects, even in dim light. Therefore, light focused for near vision through a large pupil is physiologically unusable. Intermediate vision is far less affected by this problem, and overall, reducing the light directed towards near vision through a large aperture proves far more important than reducing intermediate vision. Designing according to this principle ensures physiological light efficiency in addition to technical light efficiency. Furthermore, intermediate vision can be further subdivided. For larger pupils, less light is available in the higher range of intermediate vision. For a complete multifocal lens, the desired intensity distribution for each distance is primarily determined by human physiology.

[0016] Multifocal ophthalmic lenses are often optimized to provide visual acuity at two or three distances, arranged to coincide with distance, intermediate, and near vision. This is primarily because visual acuity is clinically measured at these specific distances. However, for the sake of patient well-being, especially for patients who wish to avoid wearing glasses, it is often preferable to provide more continuous visual acuity. Examples of this approach combined with multifocal gratings exist in the prior art. International Publication No. 202005386 presents a lens using a symmetrical grating that provides five focal points, where the highest and lowest orders, along with the central order, correspond to distance, intermediate, and near vision, while the remaining two orders provide a degree of continuous visual acuity.

[0017] Therefore, there is a need for an improved ophthalmic lens that takes advantage of the benefits of a smooth diffraction grating without discontinuities, has a zero-order bilateral usable diffraction profile that allows for very high optical efficiency, less diffraction ring, and precise placement of the principal optical power for any aperture, and has the potential to have a more biologically and manufacturably suitable diffraction profile that allows aperture-dependent adjustment of the light intensity distribution; and a lens that combines these features with an asymmetric diffraction grating having a zero-order bilateral usable diffraction profile that can distribute intermediate light more accurately with respect to pupil diameter. [Overview of the project] [Problems that the invention aims to solve]

[0018] The primary objective of this invention is to provide an ophthalmic multifocal lens comprising a refractive baseline and an optical axis, one of which provides at least four focal points that give the user distance vision.

[0019] Another object of the present invention is to provide an ophthalmic multifocal lens that provides distance vision in a configuration using diffraction orders other than the zeroth order, while maintaining a quality comparable to a configuration using the zeroth order to provide distance vision.

[0020] A further object of the present invention is to provide an ophthalmic multifocal lens comprising a seamless, smooth diffraction grating having the lowest diffraction order for distance vision, the highest diffraction order for near vision, and two intermediate diffraction orders that contribute to intermediate vision or provide increased continuous visual acuity.

[0021] A further object of the present invention is to provide an ophthalmic multifocal lens having an aperture-dependent intensity distribution such that the higher of two intermediate diffraction orders provides the user with a higher light intensity of one of the two at a 3 mm lens aperture, while the lower of the two intermediate orders provides the user with a higher light intensity at some larger lens apertures. [Means for solving the problem]

[0022] In a first embodiment, an ophthalmic multifocal lens is provided having at least a focal point for distance vision. The lens has a translucent lens body comprising a diffraction grating having useful diffraction orders on both sides of the zeroth order, extending concentrically radially from the optical axis of the lens body across a portion of the surface of the lens body. According to at least one embodiment, the diffraction grating is configured to utilize diffraction orders of the following orders: -1, 0, +1, and +2. The lens comprises at least a refractive baseline. A well-formed diffractive lens, as is well known in the art, changes with radius in absolute value (i.e., measured in millimeters), however, in secondary space (r 2 ) has a constant pitch.

[0023] A lens manufactured according to this disclosure has at least four focal points and utilizes a diffraction grating that is discontinuous with respect to at least the three innermost diffraction rings. The -1st order of the diffraction grating is positioned to correspond to distance vision, while the +2nd order is positioned to provide the user with near vision. This quadfocal lens can be tuned in several ways to achieve different types of multifocal lenses. A selection is possible among several main configurations, each of which provides continuous visual acuity at different distances. Furthermore, the intensity distribution of each main configuration can be tuned as a function of the lens aperture by changing the diffraction unit cell as a function of the lens aperture. For larger apertures associated with scotopic environments, it is often preferable to shift light from near vision and more distant intermediate vision to distance vision (order -1) or the 0th order.

[0024] One important feature of this disclosure is a shoulder structure directed toward the center of the lens within a single unit cell. This feature is often advantageous for dispersing light into three or four focal points. For parts of the lens, such as the periphery, where further distance vision is desired, this feature may be smaller.

[0025] This disclosure also provides features for further improvement by configuring a sinusoidal or smooth quadrfocal grating with the lowest intensity point between the -1st and 0th order. This results in an ophthalmic lens configuration that is highly suitable for users who wish to live without glasses. Lens configurations including such features provide strong distance vision while also utilizing light available for near, intermediate, and beyond vision. Overall, for 2mm and 3mm lens apertures, a very high degree of continuous visual acuity is achieved across the entire range from distance to near vision. For larger apertures, more light intensity enters the distance vision as desired.

[0026] The drawings are attached solely for the purpose of illustrating a quadrfocal aphakic diffractive lens having advantages over the prior art outlined above and briefly described below.

[0027] These drawings are not intended to limit the scope of protection specified in the claims, and should not be referred to alone for interpreting the scope specified in the claims without referring to the technical disclosure in the description of the present invention.

Brief Description of the Drawings

[0028] [Figure 1] Figure 1 shows a simplified anatomical structure of the human eye. [Figure 2a] Figure 2a shows a front view of a multi-focal intraocular lens for ophthalmology known in the art. [Figure 2b] Figure 2b shows a side view of a multi-focal intraocular lens for ophthalmology known in the art. [Figure 3a] Figure 3a shows a front view of a multi-focal intraocular lens for ophthalmology formed according to the present invention. [Figure 3b] Figure 3b shows a side view of a multi-focal intraocular lens for ophthalmology formed according to the present invention. [Figure 4a] Figure 4a shows a surface profile obtained by subtracting the refractive baseline of three four-focal lenses formed according to the present invention. [Figure 4b] Figure 4b shows a surface profile obtained by subtracting the refractive baseline of three four-focal lenses formed according to the present invention. [Figure 4c] Figure 4c shows a surface profile obtained by subtracting the refractive baseline of three four-focal lenses formed according to the present invention. [Figure 4d] Figure 4d shows the modeled relative intensity of the diffraction profile in Figure 4a. [Figure 4e] Figure 4e shows the modeled relative intensity of the diffraction profile in Figure 4b. [Figure 4f] Figure 4f shows the modeled relative intensity of the diffraction profile in Figure 4c. [Figure 5a]Figure 5a shows the profile of another diffractive lens formed according to the present invention, with the refractive baseline subtracted. [Figure 5b] Figure 5b shows a modeled relative intensity graph of another diffraction lens formed according to the present invention. [Figure 5c] Figure 5c shows the profile of another diffractive lens formed according to the present invention, with the refractive baseline subtracted. [Figure 5d] Figure 5d shows a modeled relative intensity graph of another diffractive lens formed according to the present invention. [Modes for carrying out the invention]

[0029] One of the important characteristics of diffraction gratings is the distinction between symmetric and asymmetric diffraction gratings. When imparting symmetric or asymmetric characteristics to multifocal ophthalmic lenses, the choice of diffraction order to use or make useful is considered. Symmetric diffraction lenses utilize orders such that they are symmetric with respect to order 0. It should be noted that symmetric diffraction gratings are defined by the orders used, not by the intensity of the light distribution at those orders. Some symmetric diffraction lenses can be tuned to have a significant difference in light intensity between, for example, orders +1 and -1, i.e., to have an uneven light distribution. Such tuned diffraction gratings are still considered symmetric diffraction gratings. Lenses based on symmetric gratings can be trifocal, utilizing orders -1, 0, and +1, or quinfocal, utilizing orders -2, -1, 0, +1, and +2. Such symmetric gratings can be sinusoidal or non-sinusoidal. A commonly known non-sinusoidal symmetric grating is a binary grating. However, gratings that do not utilize order 0 can also be considered symmetrical. Specifically, symmetrical examples of lattices utilizing four orders—-2, -1, +1, and +2—may be useful for ophthalmic lenses in some cases.

[0030] The majority of ophthalmic trifocal diffractive lenses utilize a sawtooth profile. It is known in the art that trifocality can be achieved by combining the sawtooth profiles of two bifocal diffractive lenses. This can result in diffractive lenses with usable orders arranged asymmetrically with respect to the zeroth order; for example, a trifocal lens may utilize orders 0, +1, and +2, or orders 0, +2, and +3. Such diffraction gratings are hereafter referred to as asymmetric gratings. However, asymmetric gratings also exist that utilize both foci of the zeroth order. Such gratings can have discontinuities and can be sawtooth-like, or they can instead be sinusoidal gratings with no discontinuities at all.

[0031] For diffractive multifocal lenses with an odd number of foci, including trifocal lenses, the best possible diffraction efficiency for the most useful intensity distribution is achieved by a smooth sinusoidal surface with usable orders arranged symmetrically around the zeroth order.

[0032] When comparing diffractive surfaces, diffraction efficiency is a crucial factor. Diffractive efficiency is a measure of how much of the optical power is directed to the desired order of diffraction, or, in the case of diffractive lenses in particular, how much of the optical power is directed to the desired focal point. For bifocal lenses, where the surface of the lens body is optimized to provide the best possible visual acuity at two different distances, the best possible diffraction efficiency is achieved by using the principle of phase-matched Fresnel lenses, which utilize a serrated or jagged diffraction pattern. See the publication “Refractive and diffractive properties of planar micro-optical elements,” M. Rossi et al., Applied Optics Vol.34, No.26(1995), pp. 5996-6007, which is incorporated herein by reference.

[0033] In this field, it may be advantageous to consider linear phase gratings first, as they have well-developed theories and are applicable to diffractive lenses. Therefore, this is one method for calculating the diffractive unit cells used. For a special case of a three-focal linear grating with a uniform intensity distribution for each order, the optimal solution is a structure without sharp edges, as specifically demonstrated in the publication "Analytical derivation of the optimum triplicator," F. Gori et al., Optics Communication 157 (1998), pp. 13-16 (this publication is referenced herein by reference).

[0034] The publication "Theory of optimal beam splitting by phase gratings. I. One-dimensional gratings," by LAROMERO and FMDickey, Journal of the Optical Society of America, Vol. 24, No. 8 (2007), pp. 2280-2295 (this publication is referenced herein by reference) discloses this more generally, demonstrating that the optimal grating for evenly splitting into at least an odd number of orders has a continuous profile. This latter paper provides mathematical tools for finding the optimal linear phase grating for any given set of target orders and any given intensity distribution between these target orders. The optimal grating is defined as a linear diffraction grating that has the highest diffraction efficiency for a particular intensity distribution. Note that in the publication by Gori et al. and Romero et al., linear phase gratings are discussed only with the intention of forming a beam splitter. The x-axis of the linear grating is the r of the diffraction lens. 2By treating it as space, it is possible to adjust any such linear phase to the lens. This optimization theory is one of several good methods for finding a way to begin developing lens gratings. However, optimization for the best diffraction efficiency is not always the best choice for the diffraction unit cells used in the grating, and there are important lens-specific effects that are not considered by the optimization of linear phase gratings, and optimizing for these effects can be advantageous in designing lenses according to the present invention. According to this disclosure, it has been demonstrated that a cosine half-step grating may, in certain cases, be strictly superior to the corresponding optimized grating when a low height is considered a desirable characteristic for the diffraction grating. Furthermore, known optimization processes do not take into account the dramatic effect of horizontal shift of the diffraction grating in diffraction lens design. To find the actual final diffraction unit cells with optimal performance, a combination of Fourier modeling and actual manufacturing followed by measurements should be relied upon.

[0035] In the field of technology, different methods exist for calculating and tuning diffractive lenses with useful orders on both sides of the zeroth order. One method, as mentioned above and further detailed in the international publication PCT / EP2019 / 080758, is to use an optimized linear grating converted into a diffractive lens. An early example of a lens based on a symmetric diffractive grating is the seven-focal lens described in the paper: Golub et al., "Computer generated diffractive multi-focal lens", Journal of modern optics 39, no.6(1992):1245~1251. Further embodiments are already described in the Osipov 2015 study and the 2012 study: Osipov et al., "Fabrication of three-focal diffractive lenses by two-photon polymerization technique", Applied Physics A 107, no.3(2012):525~529. These papers disclose trifocal symmetric lenses formed by modifying sinusoidal gratings. Different approaches are disclosed in U.S. Patent No. 5,760,871A and Israeli Patent No. 104316, which use a so-called asymmetric super-Gaussian formula to design trifocal gratings with uneven intensity distributions. Yet another method is described in International Publication No. 2020053864 A1, which uses a Gerchberg-Saxton iterative algorithm to design the surface profile of a pentfocal (having five focal points) lens with a symmetric diffraction grating. A method for constructing a suitable trifocal lens based on binary data is disclosed in International Publication No. 9411765.

[0036] The lens according to the present invention is an ophthalmic lens comprising at least a refractive baseline and a diffraction grating superimposed on the refractive baseline, which is arranged such that the zeroth order on both sides of the design wavelength are usable by the lens user.

[0037] Strong distance vision is a typical criterion for confirming the success of cataract surgery. This is because strong distance vision is important for all apertures. This document contains many specific considerations regarding lens performance at different apertures. For the sake of simplicity, apertures and pupil diameters are all defined in the forward lens plane, assuming an average human eye. However, for clarity, the corresponding pupil diameters are larger, and their exact size will vary slightly from person to person. In an average human eye, a 2mm aperture in the lens plane corresponds to a 2.35mm pupil diameter, 3mm corresponds to 3.515mm, 4.5mm to 5.28mm, and 6mm to 7.04mm.

[0038] An important aspect of the present invention is adjusting the intensity distribution as a function of the lens aperture. Generally, the eye has a fairly large depth of field at small pupil diameters due to the pinhole effect. Pupil diameter depends not only on the pupillary light reflection but also on the accommodative reflection, which causes the pupil to dilate insufficiently when focusing on closer objects. For this reason, it is often advantageous to shift the light from near vision to far vision for large pupil diameters, while for larger apertures, it is advantageous to prioritize intermediate vision over near vision, and furthermore, if the light cannot be redistributed to other usable gratings, to remove or diffuse the light from near vision. In certain cases of quadrupole lenses, it may be advantageous to shift the light intensity from +1st order to 0th order. Often the intermediate distance corresponds to +1st order, but other configurations are also possible. Reducing the intensity of near vision is done in part to minimize the halo problem.

[0039] For small pupil diameters, it is important to consider the pinhole effect. Pupil constriction increases the depth of focus of the lens, and for very small pupils, this effect generally provides relatively good visual acuity at all distances, even with lenses that offer only a single focal point. Many modern multifocal and extended depth of focus (EDOF) lenses utilize this effect by making the light provided by the lens primarily usable for intermediate or near vision. The argument, when placed in the center of the lens, works well for the user in photopic conditions due to the large depth of field for a very small aperture, while the intensity provided for near and / or intermediate vision can be particularly useful in twilight conditions with slightly larger pupil diameters. However, in twilight conditions, additional near and intermediate vision power is important to ensure usable visual acuity at most distances. Normally, in twilight conditions, it is desirable to maintain near vision stronger than intermediate vision to enable good reading without the use of glasses. However, in scotopic conditions, near vision is no longer useful and may even be harmful.

[0040] This document does not include physical measurements, only modeled light intensity distributions. However, where physical lens measurements are discussed in this document, measurements performed on a physical optical bench using Eye model 1 according to ISO 11979-2 are referred to. In this standard, Eye model 1 uses a neutral cornea. Eye model 1 can be used to measure either intensity or focus-pass modulation transfer function (MTF). MTF is always measured at a specific frequency and is measured in lines per millimeter (lp / mm). It is common to compare MTF values ​​at 50 lp / mm or 100 lp / mm.

[0041] The inventors have found that a highly advantageous method for constructing a multifocal lens is to utilize a four-focal diffraction grating that provides far vision using the -1st order and near vision using the near vision. These four-focal gratings are formed so that each diffraction ring has a shoulder above the main peak that is about half the height of the main peak. This shoulder is located on the central side of the peak it is associated with. The shape of the diffraction unit cells is not discontinuous, and the exact shape can be modified to achieve different intensity distributions.

[0042] Figure 1 shows a simplified anatomical structure of a human eye 10 for illustrative purposes of this disclosure. The anterior part of the eye 10 is formed by the cornea 11, which is a spherical, transparent tissue covering the pupil 12. The pupil 12 is the adaptable light-receiving part of the eye 10, which controls the amount of light received by the eye 10. Light rays passing through the pupil 12 are received by the natural lens 13, a small, transparent, flexible disc inside the eye 10, which focuses the light rays onto the retina 14 at the posterior part of the eye 10. The retina 14 contributes to image formation by the eye 10. The vitreous cavity 15, i.e., the space between the retina 14 and the lens 13, is filled with vitreous fluid, a transparent, jelly-like substance. The anterior and posterior chambers 16, i.e., the space between the lens 13 and the cornea 11, are filled with aqueous humor, a transparent, watery liquid. Reference numeral 20 indicates the optical axis of the eye 10.

[0043] For a clear and sharp distant field of vision by the eye 10, the lens 13 should be relatively flat, while for a clear and sharp near field of vision, the lens 13 should be relatively curved. The curvature of the lens 13 is controlled by the ciliary muscle (not shown), which is controlled by the human brain. A healthy eye 10 is able to adapt, or control, the lens 13 to provide a clear and sharp field of vision at any distance in front of the cornea 11 between the distant and near fields of vision.

[0044] An ophthalmic lens or artificial lens is fitted in combination with the crystalline lens 13 to correct vision in the eye 10, in which case the ophthalmic lens is positioned in front of the cornea 11 or replaces the crystalline lens 13. In the latter case, it is also referred to as an aphakic ophthalmic lens.

[0045] Multifocal ophthalmic lenses are used to enhance or correct the visual acuity of the eye 10 at various distances. In the case of trifocal ophthalmic lenses, for example, the ophthalmic lens is arranged to provide a clear and sharp field of view at three nearly distinct distances or focal points, often including far vision, intermediate vision, and near vision, indicated by reference numerals 17, 18, and 19 in Figure 1, respectively. Far vision is an optical term for when the incident light is parallel or nearly parallel. Light rays emitted from objects located at or near these distances or focal points 17, 18, and 19 are properly focused on the retina 14, i.e., a clear and sharp image of these objects is projected. In practice, focal points 17, 18, and 19 can correspond to focal lengths ranging from several meters to tens of centimeters and several centimeters, respectively. Typically, an ophthalmologist selects a lens so that the patient's far focus is in focus on parallel light. In general optical terminology, this means that the far point is in focus at infinity. When examining a patient, ophthalmologists typically measure near vision at a distance of 40 cm from the eye and intermediate vision at a distance of 66 cm, although other values ​​can also be used.

[0046] The amount of correction provided by an ophthalmic lens is called optical power (OP) and is expressed in diopters (D). Optical power OP is calculated as the reciprocal of the focal length f measured in meters. That is, OP = 1 / f, where f is the individual focal length from the lens to the respective focal points for distance vision 17, intermediate vision 18, or near vision 19.

[0047] Figure 2 shows a multifocal aphakic intraocular lens for ophthalmic use that is generally known in the technical field. Diffractive lenses for ophthalmic applications utilize a combination of a diffraction grating and a refractive lens body.

[0048] Figure 2a shows a top view of a typical ophthalmic multifocal aphakia intraocular lens 30, and Figure 2b shows a side view of the lens 30. The lens 30 comprises a translucent circular disc-shaped lens body 31 and a pair of haptics 32 extending outward from the lens body 31 to support the lens 30 in the human eye. Note that this is one example of a haptic, and many known haptic designs exist. The lens body 31 has a biconvex shape including a central part 33, an anterior or frontal surface 34 and a posterior or rearal surface 35. The lens body 31 further comprises an optical axis 29 that traverses the anterior and rearal surfaces 34,35 and passes through the center of the central part 33. Those skilled in the art will understand that the optical axis 29 is a virtual axis for the purpose of referring to the optical properties of the lens 30. In actual embodiments, the convex lens body 31 yields refractive optical power of about 2D to 35D, with about 20D to 22D being the most common.

[0049] In the illustrated embodiment, a periodic translucent diffraction grating or relief 36 is positioned on the front surface 34 of the lens body 31, including a ring or zone extending concentrically with respect to the optical axis 29 passing through the center 33, over at least a portion of the front surface 34 of the lens body 31. The diffraction grating or relief 36 provides a set of diffraction foci. Although not shown, the diffraction grating or relief 36 may also be positioned on the rear surface 35 of the lens body 31, or on both sides 34, 35. In fact, the diffraction grating 36 is not limited to concentric circular or annular ring-shaped zones, but includes, for example, concentric elliptical or oval-shaped zones, or more generally, any type of concentric rotating zone shape.

[0050] In practice, the optical diameter 37 of the lens body 31 is approximately 5-7 mm, while the total outer diameter 38 of the lens 30 including the haptic 32 is approximately 12-14 mm. The lens 30 may have a central thickness 39 of approximately 1 mm. In the case of ophthalmic multifocal contact lenses and eyeglasses or spectacle lenses, the lens body 31 does not have a haptic 32, while the lens body 31 may have a plano-convex shape, a biconcave shape, a plano-concave shape, or a combination of a convex and concave shape. The lens body may contain hydrophobic acrylic, hydrophilic acrylic, silicone material, or any other translucent material suitable for use in the human eye in the case of aphakia ophthalmic lenses.

[0051] Those skilled in the art will understand that the lens body 31 may include a plano-convex shape, a biconcave shape, or a plano-concave shape, as well as a combination of a convex shape and a concave shape or a curved surface (not shown).

[0052] Figure 3a shows a top view of an ophthalmic multifocal aphakic intraocular lens 50 operating according to the present invention, and Figure 3b shows a side view of the lens 50. The difference from the prior art illustrated in Figures 2a and 2b lies in the optical system of the lens. The lens body 54 has a biconvex shape including an anterior or frontal surface 52 and a rear or rearal surface 53. In some embodiments, those skilled in the art will know that one or both of the anterior surface 52 and the rearal surface 53 may be concave or planar, depending on the refractive baseline required for a particular application. In this application according to the present invention, the lens body according to the present disclosure has an anterior surface 52 formed as the sum of a multifocal diffraction profile 51 and a refractive profile. The refractive profile is often equal to the refractive baseline. In some cases, the refractive profile can be configured as the sum of the refractive baseline and a corrected profile. The refractive baseline is substantially monofocal, and any substantially monofocal design can be used. It is well known that any monofocal design takes both the anterior and rear sides into consideration. The key point is that any useful single-focal design can be used to define the refractive baseline of the present invention. The multifocal diffraction profile operates in a favorable and consecutive set of orders (-1, 0, +1, +2), with the -1st order positioned to provide the user with far vision and the +2nd order positioned to provide near vision. It should be noted that the front side 52 is depicted with a refractive baseline having a larger radius than typical, i.e., lower optical power, which is done purely for illustrative purposes to keep the diffracting components visible.

[0053] It will be obvious to those skilled in the art that this is merely one possible configuration. For example, it is possible to place the diffracting portion of the optical system on the rear side. When it is stated that the diffraction pattern is combined with the refractive surface, it can be interpreted as a superposition on one surface of the lens, or as them being combined by occupying each of the surfaces of the lens.

[0054] The shape or height profile of the refractive baseline for any portion of the lens can be selected from a plurality of known continuous refractive profiles from monofocal lenses, such as variations of either a spherical or aspherical profile. Most modern intraocular monofocal lenses are aspherical, and the asphericity is selected to be neutral and therefore not to cause further aberrations in the eye, or they are intentionally designed to exhibit negative spherical aberration to completely or partially cancel out the positive spherical aberration normally present in the human cornea, assuming the optical system of an average eye. All of these selections should be considered as different ways of forming a monofocal base. The present invention disclosed herein can be combined with any such monofocal base. The refractive or diffracting surface can be manufactured by laser microfabrication, diamond turning, 3D printing, or any other processing or lithographic surface processing technique.

[0055] Figures 4a, 4b, and 4c show the lens profiles of lenses formed according to the present invention, respectively, with the refractive baseline subtracted. These profiles were calculated for a refractive index of 1.5359 and later modeled. All three diffraction profiles utilize a diffraction unit cell with four main diffraction orders. The diffraction profiles are shown here from the center of the lens, coinciding with the optical axis, to the edge of the optical surface with a radius of approximately 3 mm. The only, but major, difference between the three profiles is the different horizontal shifts involved in each profile, which define the three main types of highly useful quadfocal lenses that can be manufactured.

[0056] Figures 4d, 4e, and 4f show the modeled relative intensity distributions for different lens apertures of the lens profiles in Figures 4a, 4b, and 4c, respectively.

[0057] In the lens profile in Figure 4a, the diffraction rings are positioned approximately centered on the optical axis and have four diffraction orders: -1, 0, +1, and +2. As shown in Figure 4d, these provide the user with visual acuity at approximately 19.0D, 20.1D, 21.1D, and 22.0D, respectively. The -1st order corresponds to distance vision, while near vision is addressed by the +2nd order with a 3D addition, which is above but close to the lower limit of near addition for clinical interest. The +1st order results in a 2D addition, which is close to the ideal position for intermediate addition. The 0th order is a 1D addition for distance vision, which is considerably lower than intermediate vision but can certainly contribute to the same total depth of focus. The repeating diffraction unit cell in Figure 4a has higher peaks, with a peak interval of 1.65 μm in this case, where a gentle shoulder toward the center of the lens is present at each major peak. In this configuration of a sinusoidal or smooth four-focal grating, the lowest intensity trough is located between the -1st and 0th orders. This results in an ophthalmic lens configuration that is highly suitable for users who do not wish to wear glasses. This configuration provides strong but separated distance vision and fairly continuous visual acuity for near, intermediate, and beyond vision. For 2mm and 3mm lens apertures, a very high degree of continuous visual acuity is obtained across the entire range from distance to near vision. For larger apertures, more light intensity enters the distance field, as desired. The deepest intensity dip in a 2mm lens aperture is between the -1st and 0th order.

[0058] In the lens profile shown in Figure 4b, the valleys of the diffraction ring are positioned approximately centered on the optical axis, with four diffraction orders of -1, 0, +1, and +2, providing the user with visual acuity at approximately 19.0D, 19.9, 21.0D, and 22.0D, as shown in Figure 4e. This lens functions similarly to those described in Figures 4a and 4d, however, in this configuration of a sinusoidal or smooth four-focal grating, the lowest intensity valley is located between the 0th and +1st orders. The lowest intensity point is not as low as in Figure 4d. For 2mm and 3mm lens apertures, this lens primarily provides continuous visual acuity between distance and near vision. This version also forms a very suitable configuration for ophthalmic lenses for users who wish to go without glasses. This configuration provides strong distance vision extended by the 0th order. Intermediate and near vision are also provided, although the continuity of visual acuity is not as good as in the intermediate-near vision configuration. In Figure 4b, it can be seen that the unit cell associated with this lens changes significantly as a function of the lens aperture. This is done to provide the desired aperture-dependent adjustment. One very advantageous feature found during the examination of these diffraction profiles is that the grating becomes lower when the grating is adjusted to provide more intensity in the far view (i.e., light corresponding to the lowest diffraction order). For a trifocal sinusoidal grating, increasing the intensity in the far view requires a higher profile. This is a significant advantage as it allows for a lower grating at the periphery of the lens. A high diffraction pattern at the periphery of the lens increases the risk of dyphotopsia. This effect is very clear here.

[0059] In the lens profile shown in Figure 4c, the gentle shoulders of the diffraction grating are positioned approximately centered on the optical axis, resulting in a configuration with four diffraction orders: -1, 0, +1, and +2. As shown in Figure 4f, these provide the user with visual acuity at approximately 19.0D, 20.1D, 21.0D, and 22.1D, respectively. However, in this configuration, the +1st order is significantly suppressed due to its position at the center of the lens. This lens functions similarly to those described in Figures 4a, 4d, 4b, and 4e, however, this configuration of a sinusoidal or smooth four-focal grating has its lowest intensity point approximately coincide with the +1st order, making it nearly a trifocal lens. Furthermore, the 2nd order around 18D may even have a higher intensity than the +1st order. This version forms a configuration that provides good distance and near vision and some intermediate vision, but there is no precisely positioned order to provide strong intermediate vision. Since no lenses with similar characteristics are known in the art, such a novel lens can function as a bifocal lens for near and far vision, but with substantially extended far vision. The deepest intensity dip in a 2 mm lens aperture is exactly between the 0th and +2nd order.

[0060] Figure 5a shows the lens profile of a lens formed according to the present invention, shown here with the refractive baseline subtracted. This profile was calculated for a refractive index of 1.5359 and later modeled. The diffraction profile is shown here from the center of the lens, coinciding with the optical axis, to the edge of the optical surface with a radius of approximately 3 mm. The profile in Figure 5a uses a four-focal unit cell adjusted to provide less near vision and more far vision as the aperture increases. It can also be seen that the profile curves downward beyond a distance of 1.5 mm from the optical axis. This is due to the addition of positive spherical aberration to the profile to further adjust the lens performance. This added spherical aberration is the correction profile. The profile in Figure 5a consists of the diffraction profile plus the correction profile. The perfect lens curvature is the sum of the refractive profile, diffraction profile, and correction profile.

[0061] Figure 5b shows the modeled relative intensity distribution of the lens profile in Figure 5a at different lens apertures. The lens has four diffraction orders: -1, 0, +1, and +2, providing the user with visual acuity at approximately 18.8D, 20.1D, 21.3D, and 22.4D, respectively. The -1st order corresponds to distance vision and is addressed by the +2nd order with an added 3.6D for near vision, which is in the upper region of near addition. The +1st order provides an added 2.5D, which is just above the desired range for intermediate addition. The 0th order results in an added 1.3D, which is somewhat below the lower limit of intermediate addition. This lens is similar in light distribution to the lenses described in Figures 4a and 4d, having a well-developed continuous visual acuity between the 0th and +2nd orders. For larger apertures, the relative light intensity decreases significantly for the 2nd and +1st orders. The intensity of the 0th order increases significantly with increasing aperture. This increase in intensity at the 0th order is, to some extent, due to the adjustment of the diffraction unit cell accompanying aperture expansion, but is also affected by the positive spherical aberration added for apertures larger than 3 mm (radius of 1.5 mm). This lens has four truly usable orders, each adjusted according to the lens aperture. The intermediate focus is replaced here by two different foci, with the lower power focus (0th order) being dominant in photopic environments, while the higher power focus is dominant in scotopic environments.

[0062] Figure 5c shows the lens profile of a lens formed according to the present invention, shown here with the refractive baseline subtracted. This profile was calculated for a refractive index of 1.5359 and later modeled. The diffraction profile is shown here from the center of the lens, coinciding with the optical axis, to the edge of the optical surface with a radius of approximately 3 mm. The profile in Figure 5c is adjusted using a four-focal unit cell that provides less near vision and more far vision as the aperture increases, specifically sharply adjusted after the first two diffraction rings.

[0063] Figure 5d shows the modeled relative intensity distribution of the lens profile in Figure 5c at different lens apertures. The lens has four diffraction orders: -1, 0, +1, and +2, providing the user with visual acuity at approximately 18.8D, 20.0D, 21.1D, and 22.4D, respectively. The -1st order corresponds to distance vision and is addressed by the +2nd order with an added 3.6D for near vision, which is in the upper region of near addition. The +1st order provides an added 2.3D, which is in the upper range of intermediate addition but is a good choice for intermediate addition. The 0th order results in an added 1.2D, which is below the lower limit of intermediate addition. This configuration has extended distance vision for all apertures, which is combined with the 0th order for stronger and wider distance vision. For larger apertures, the relative light intensity decreases with respect to the 2nd and +1st orders, and the intensity of the 0th order becomes stronger than that of the +1st order. The purpose of this design is to provide the maximum physiologically usable light, since large additions are not possible for large pupil diameters.

[0064] Other variations of the examples and embodiments of the disclosure are understandable and implementable by those skilled in the art in practicing the claimed invention, based on a review of the drawings, disclosure, and appended claims. In the claims, the term “including” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude the plural. The mere fact that certain means are mentioned in different dependent claims does not indicate that a combination of these means cannot be used advantageously. No reference numeral in the claims should be construed as limiting its scope. The same reference numeral refers to the same or equivalent element or operation.

[0065] In aspects of the present disclosure, an ophthalmic multifocal lens is presented, configured to provide distance vision and at least one other usable visual acuity, comprising a translucent lens body having an optical axis and a refractive baseline, wherein the refractive baseline extends to at least a portion of the lens body, and a diffraction grating configured to act as an optical wave splitter, extending concentrically in the radial direction and superimposed on at least a portion of the refractive baseline.

[0066] According to other aspects of the present disclosure, the diffraction grating configured to operate as an optical splitter is further configured to be continuous within at least a central 3 mm aperture.

[0067] According to yet another aspect of this disclosure, the distant view is provided by the -1 order of diffraction.

[0068] According to yet another aspect of this disclosure, the near view is provided by a +2 order diffraction.

[0069] According to yet another aspect of the present disclosure, at least two complete consecutive periods of the diffraction grating include prominent shoulders, i.e., projections on the diffraction ring, the projections being located on the central portion of the ring.

[0070] According to yet another aspect of this disclosure, for all lens apertures exceeding 4 millimeters, the intensity provided by the -1st order is configured to be higher than the intensity provided by the +2nd order.

[0071] According to yet another aspect of this disclosure, for a lens aperture of 3 to 4 millimeters, the intensity provided by the -1st order is configured to be greater than that provided by the 0th and +1st orders, respectively.

[0072] According to yet another aspect of this disclosure, for a 3 mm lens aperture, the +1st order is configured to provide a stronger light intensity than that provided by the 0th order, while for lens apertures greater than 5 mm, the 0th order is configured to provide a stronger light intensity than that provided by the +1st order.

[0073] According to yet another aspect of this disclosure, either the +1st or 0th order is suppressed to have a light intensity of less than 10% as measured by Eye model 1 in accordance with ISO 11979-2.

[0074] According to yet another aspect of this disclosure, a correction profile is added to the diffraction profile to increase the order of -1, 0, +1, or +2. [Explanation of Symbols]

[0075] 10 eyes 11 Cornea 12 Pupil 13 Natural lens 14 Retina 15 Vitreous cavity 16 Anterior and posterior chambers 17 Far vision 18 Intermediate vision 19 Near vision 20 Optical axis 29 Optical axis 30 Ophthalmic Lenses 31 Lens body 32 Haptic 33 Center 34 Front side 35 Posterior side 36 Diffraction Gratings 37 optical diameter 38 Outer diameter 39 Center thickness 50 Multifocal Aphakic Intraocular Lenses 51 Multifocal Diffraction Profiles 52 Front and side view 53 Posterior side 54 Lens body

Claims

1. An ophthalmic multifocal lens configured to provide distance vision and at least one other usable visual acuity, comprising a translucent lens body having an optical axis and a refractive baseline, wherein the refractive baseline extends to at least a portion of the lens body, and a diffraction grating configured to act as an optical wave splitter, extending concentrically in the radial direction and superimposed on at least a portion of the refractive baseline, The diffraction grating, configured to operate as an optical wave splitter, is further configured to be continuous within at least a central 3 mm aperture. The aforementioned distant view is provided by the -1st order diffraction, and The aforementioned near vision is provided by a +2 order diffraction, characterized by the lens.

2. An ophthalmic multifocal lens configured to provide distance vision and at least one other usable visual acuity as described in claim 1, wherein at least two complete consecutive periods of the diffraction grating include prominent shoulders, i.e., projections on the diffraction ring, the projections being located on the central portion of the ring.

3. An ophthalmic multifocal lens configured to provide distance vision and at least one other usable visual acuity as described in claims 1 and 2, characterized in that for all lens apertures exceeding 4 millimeters, the intensity provided by the -1st order is higher than the intensity provided by the +2nd order.

4. An ophthalmic multifocal lens configured to provide distance vision and at least one other usable visual acuity as described in any one of claims 1 to 3, characterized in that, for a lens aperture of 3 mm to 4 mm, the intensity provided by the -1st order is greater than that provided by the 0th and +1st orders, respectively.

5. An ophthalmic multifocal lens configured to provide distance vision and at least one other usable visual acuity as described in any one of claims 1 to 4, characterized in that, with a 3 mm lens aperture, the +1st order is configured to provide a stronger light intensity than that provided by the 0th order, while with a lens aperture of 5 mm or more, the 0th order is configured to provide a stronger light intensity than that provided by the +1st order.

6. An ophthalmic multifocal lens configured to provide distance vision and at least one other usable visual acuity as described in any one of claims 1 to 5, characterized in that the +1st order or the 0th order is suppressed to have a diffraction efficiency of less than 10% as measured by Eye model 1 in accordance with ISO 11979-2.

7. An ophthalmic multifocal lens configured to provide distance vision and at least one other usable visual acuity as described in any one of claims 1 to 6, characterized in that a correction profile is added to the diffraction profile to increase one of the order -1, 0, +1, or +2.

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