Adaptive multi-focus diffractive ophthalmic lens

Abstract

An ophthalmic multifocal lens providing distance, intermediate and near vision, comprising an optically transparent body with an optical axis and a refractive baseline extending across a portion of the lens body, a first portion coinciding with a central region of the lens body, and a concentrically radially extending multifocal second portion, the second portion further comprising a symmetric multifocal diffraction grating superimposed on the baseline and covering a portion of the lens, the shape and resulting light intensity distribution of which varies with distance to the optical axis, the first portion being substantially concave and connected to a ridge of the grating closest to the optical axis, providing a predominant optical power between intended distance and intermediate powers, and configured such that the ratio of energy intended for distance vision to energy intended for near vision is lower for a predetermined aperture.

Description

Technical Field

[0001] The present disclosure generally relates to ophthalmic lenses, and more particularly to ophthalmic contact and intraocular multifocal lenses, where the multifocality is provided by a diffractive structure configured to best serve human vision across a variety of pupil sizes.

Background Art

[0002] Diffractive lenses for ophthalmic use are configured as hybrid lenses with a diffractive pattern added on a refractive body. Often one surface of the lens is purely refractive and the other surface has a diffractive grating superimposed on a refractive baseline. The refractive baseline may be spherical or some kind of aspherical shape. A high-order single-focus diffractive pattern can also function as a pure refractive shape. The diffractive portion can generally be applied to either of the two surfaces of the lens. When combining a diffractive pattern with a refractive surface having a special structure, it is generally not a problem whether they are added to the same surface, or one is added to the first surface and the other is added to the second surface of the lens. At the same time, two diffractive patterns may be combined by superimposing them on one surface or by adding them so that they overlap on separate surfaces. The optical power of a lens for a particular diffractive order can be calculated by adding the refractive base power and the optical power of that diffractive order.

[0003] In the anatomical structure of the eye, light passes through an opening within the iris called the pupil, then reaches the lens and is focused on the retina. Since the size of the pupil is regulated by the iris muscles, the pupil contracts rapidly when exposed to bright light and dilates (expands) in dim light. The pupil aperture also narrows when focusing on nearby objects and expands for more distant viewing. At its maximum contraction, an adult's pupil may be less than 1 mm in diameter and can increase up to 10 times its maximum diameter. The size of the human pupil can vary as a result of age, disease, trauma, or other abnormalities within the visual system, including dysfunction of the pathways that control pupil movement.

[0004] Based on the pupil response in combination with the specific responses of cones and rods in the retina of the eye, three main eye function modes are observed under different illuminance levels (cd / m2), namely bright light (bright light), dim light (low light conditions), and twilight (intermediate). The luminance level, background, and surroundings of the observed object determine the activities of rods and cones by the retinal illuminance level (light intensity).

[0005] Furthermore, the visual system is more sensitive to light incident through the center of the eye's pupil than to light incident from around the pupil. This is called the first type of Stiles–Crawford effect (SCE-I) and is also known as "retinal directional sensitivity," which describes the angular dependence of retinal sensitivity. The axial ray incident on the pupil near its center is parallel to the retinal receptor and is more effective than the off-axis oblique ray incident on the pupil near its edge. Therefore, the light passing through the periphery of the pupil is less efficient in terms of visual stimulation than the light passing near the center of the pupil (i.e., the axial light forms a sharper image than the off-axis light) and increases the depth of focus (see the reference (W. Fink and D. Micol, “computer-based simulation of visual perception under various eye defects using Zernike polynomials,” J. Biomed. Opt., vol. 11, no. 5, p. 054011, 2006)). The SCE can significantly improve the defocused image quality and defocused visual acuity (especially for tasks that require visual phase perception) (see the reference (X. Zhang, M. Ye, A. Bradley, and L. Thibos, “Apodization by the Stiles-Crawford effect moderates the visual impact of retinal image defocus,” J. Opt. Soc. Am. A, vol. 16, no. 4, p. 812, 1999)).

[0006] Note that the diffraction grating functioning as a lens has a pitch that varies absolutely with the radius. The pitch depends on the refractive index, the design wavelength, and the optical power of the first diffraction order. The pitch is determined such that the optical path difference (OPD) through the lens to the focus of the first diffraction order has exactly one wavelength difference per period. To show the periodicity of the diffraction grating, the diffraction lens profile is often plotted against the square of the radius. When plotted in this way, the period (grating pitch) is equidistant, and the period pitch in the r2 space is 2λ / D. Here, λ is the design wavelength and D is the optical diffraction power (diopter) of the first order. This forms the basis of a well-formed phase-matched diffraction lens.

[0007] The term "diffraction lens" is sometimes used for well-known Fresnel lenses. A Fresnel lens consists of concentric zones with vertical steps at the zone junctions. The zones within a Fresnel lens often have equal widths, and the optical properties of each zone can be analyzed using refraction theory. However, the diffraction lens described here is a lens that requires diffraction analysis.

[0008] The most well-studied type of diffraction lens is the single-focus phase-matched Fresnel lens taught by the 1995 study (Rossi et al., "Refractive and diffractive properties of planar micro-optical elements"). This type of lens uses a sawtooth diffraction unit cell and a step height corresponding exactly to a phase modulation of 2π.

[0009] It is often desirable to provide more than one focus. In an ophthalmic lens, for example, it is advantageous to provide both distance and near vision simultaneously. The most optically efficient lens possible for providing two foci uses a sawtooth profile similar to the phase-matching Fresnel described above, but with a reduced height. The highest possible diffraction efficiency of such a lens is close to 81%. For diffractive lenses optimized for three or more foci, as will be described below, the sawtooth pattern is not the most efficient, and higher diffraction efficiencies are possible.

[0010] In recent years, lenses providing three distinct foci, often distance, intermediate, and near vision, have become increasingly common.

[0011] PCT / EP2019 / 080758 describes a method of constructing a multifocal lens that combines a single-focus central zone providing only distance vision with a symmetric multifocal grating. This document details how to combine the single-focus central zone and the symmetric diffractive grating to achieve the highest possible optical efficiency. It also explains how to achieve the desired intensity distribution for one aperture. However, the addition of a pure single-focus central zone reduces the overall optical efficiency compared to a lens with a highly efficient grating over the entire lens surface.

[0012] WO2020053864A1 discloses a multifocal lens that utilizes a symmetric diffractive grating technically having five foci. Near vision is dominant with an aperture of about 2 mm or less. Further, the peak-to-peak height of the diffractive grating is higher than desirable. Measured at a 2 mm aperture, the lens behaves as a bifocal lens with two fairly broad peaks as presented, and at 3 mm, it behaves substantially as a trifocal lens.

[0013] Most of the ophthalmic diffractive trifocal lenses use a sawtooth profile. To achieve trifocality, it is known in the art to combine the sawtooth profiles of two diffractive bifocal lenses. This results in a diffractive lens with available orders asymmetrically arranged with respect to the zero order. For example, a trifocal lens uses orders of zero, +1, +2 or zero, +2, +3. US9320594 discloses a diffractive trifocal lens in which the optical thickness of the surface profile varies monotonically with the radius within each zone, and the different steps in the optical thickness at the junctions between adjacent zones define the step height. The step height of each individual zone may vary periodically from one zone to another, thereby adjusting the diffraction order efficiency of the optical element, and the step heights are arranged alternately between two values. EP2377493 proposes a method for manufacturing an intraocular lens for aphakic eyes that can more reliably ensure a multifocal effect and reduce the influence of aperture changes and lens decentration. EP2503962 discloses an intraocular lens including a front surface and a rear surface and having a substantially front-rear optical axis, one of these front and rear surfaces including a first diffraction profile forming at least one first diffraction focus of +1 order on the optical axis and a second diffraction profile forming a second diffraction focus of +1 order, the two diffraction foci being distinct, and at least one part of the second diffraction profile overlapping at least one part of the first diffraction profile. Further, it explains how to use the so-called apodization of a sawtooth diffraction grating to increase the relative intensity of distance vision as the aperture increases. When discussing apodization with respect to a diffractive lens, it is understood to refer to the depth of the diffraction pattern that decreases as the aperture increases. WO2019130030A1 also explains apodization and inverse apodization of a sawtooth diffractive lens, referring to the profile height that increases as the aperture increases to decrease and increase the relative intensity to distance vision. The combination of these two concepts is called cross-apodization. US9223148 proposes a lens with three or more powers, one of which is refractive and the other is at least diffractive.US50117000 proposes a multi-focus profile phase plate having a plurality of annular concentric zones spaced according to the formula r(k) = sqrt(constant x, k), where r(k) is the zone radius and k is the zone, with repeating steps incorporated into the profile and having an optical path length greater than or less than 1 / 2 wavelength.

[0014] One of the prior art documents in the technical field of the present invention can be referred to EP3435143, which teaches an ophthalmic multi-focus diffractive lens including foci for near vision, intermediate vision, and far vision. The lens comprises a light-transmissive lens body providing a refractive focus, and a periodic light-transmissive diffraction grating extending concentrically over at least a portion of the surface of the lens body to provide a set of diffractive foci. The diffraction grating is designed to operate as a light splitter, the refractive focus provides a focus for intermediate vision, and the diffractive foci provide foci for near vision and far vision. The diffraction grating has a phase profile arranged to change the phase of the incident light at the lens body and optimize the overall efficiency of the light distribution at the refractive and diffractive foci. The order of this lens is symmetrically arranged around the zero order and operates at least at -1 order, 0 order, and +1 order.

[0015] Diffractive lenses with sharp transitions in the diffraction profile, such as lenses with a sawtooth profile or a binary profile, cause difficulties in processing and, in the finished lens, cause light scattering, increasing the occurrence of some undesirable optical phenomena such as stray light and glare, the difficulty of observation in the presence of bright light such as direct or reflected sunlight, or artificial light such as automotive headlights at night, and the halo effect, i.e., the generation of rings or spots of dim light, i.e., white or colored light visible under low light conditions. Diffractive lenses without sharp transitions perform better against these problems and have a higher potential diffraction efficiency for multifocal lenses with at least an odd number of foci. Also, sinusoidal or smooth diffraction profiles are suggested to be more biocompatible compared to sawtooth profiles due to a reduction in debris deposition effects, as described in the literature (Osipov et al. "Application of nanoimprinting technique for fabrication of trifocal diffractive lens with sine-like radial profile" as published in Journal of biomedical optics 20, no. 2 (2015): 025008).

[0016] According to the teachings of WO2019020435, the light distribution at the focus of an ophthalmic lens including a diffraction grating having a continuous periodic phase profile function and the usable orders symmetrically arranged around the zero order can be adjusted over a relatively large intensity range by modulating one or both of the argument and amplitude of the phase profile function as a function of the radius or radial distance with respect to the optical axis of the lens body. Regarding the teachings of EP20170183354 and the aforementioned WO2019020435, which include a trifocal lens operating at -1 order, 0 order, and +1 order, trifocal lenses known in this field have been proposed several years ago. A general method of constructing the lens is also known from the teachings of US5017000. The resulting diffractive lens is a diffractive lens operating at 0 order, +1 order, and +2 order.

[0017] According to the teachings of WO2019020435, a triple-focus lens can be constructed by starting from a linear phase grating optimized for equal light distribution between diffraction efficiency and the available diffraction orders. The linear phase grating has been studied and developed with the intention of creating a beam splitter. The general theory of the optimization of the linear phase grating is taught by the literature (Romero and Dickey, "Theory of optimal beam splitting by phase gratings. I. One-dimensional gratings" in Journal of the Optical Society of America Vol. 24, No. 8 (2007) p. 2280-2295). Existing literature on diffraction phase gratings has focused on finding the optimal solution, which means the maximum diffraction efficiency in the case of an equal intensity distribution between a specific number of orders.

[0018] For the reasons described above, it is often advantageous to use a multi-focus hybrid lens that utilizes a smooth diffraction grating that employs both positive and negative diffraction orders. However, such lenses existing in the prior art have several limitations.

[0019] Features that are often discussed and desired in multifocal lenses that provide distance, intermediate, and near vision are to provide a relatively uniform intensity distribution for low light conditions, while for larger pupils available in low light conditions, to provide a much stronger relative intensity for distance vision. In a sawtooth multifocal diffractive lens, this is often provided with the aid of apodization, and in this context, reference is made to a diffractive grating with decreasing height as the radius increases, as taught in the literature (Davison, J. A., & Simpson, M. J. (2006). "History and development of the apodized diffractive intraocular lens". Journal of Cataract & Refractive Surgery, 32(5), 849-858). Generally, in a diffractive multifocal lens, the height of the diffractive grating can be decreased (increased) to increase (decrease) the refractive focus, i.e., the intensity of the zero order. In an asymmetric lens, for example, using the zero order, +1 order, +2 order as in the aforementioned literature, apodization results in an increased energy distribution for distance vision as the aperture increases. For a lens using a symmetric diffractive grating that provides distance, near, and intermediate vision, this simple method cannot be used for this purpose because the refractive focus within the symmetric grating is at or near intermediate vision. The above-mentioned WO201911300A1 describes a method of improving the intensity distribution of a sawtooth diffractive lens using cross-apodization.

[0020] US8486141B2 discloses a multi-zone single-focus ophthalmic lens including an inner zone, an intermediate zone, and an outer zone. The inner zone has a first optical power. The intermediate zone surrounds the inner zone and has a second optical power that differs from the first power by at least less than about 0.75 diopters. The outer zone surrounds the intermediate zone and has a third optical power that differs from the second optical power. In certain embodiments, the third optical power is equal to the first optical power. US9968440B2 discloses an ophthalmic lens including an optical element having a front surface, a rear surface, and an optical axis. At least one of the front surface and the rear surface includes a first zone extending from the optical axis to a first radial boundary and a second zone extending from the first radial boundary to the edge of the optical element. The first zone includes an inner region and an outer region separated by a phase shift mechanism, and the phase shift includes ridges extending outwardly from the inner region and the outer region. US7073906B1 discloses a central aspheric single-focus zone arranged concentrically in zones using an asymmetric diffraction grating.

[0021] For a lens to provide sufficient vision without the user relying on glasses, it is necessary to provide myopia, intermediate vision, and hyperopia. Under bright conditions, when there is a small pupil, a complete multifocal vision with particularly strong hyperopia is desirable. However, the central aperture of a lens that provides an extremely narrow hyperopia increases the risk of dioptric mismatch. The central part of the lens that provides a power slightly stronger than the intended power of hyperopia will reduce this risk. This is particularly important as the quality of hyperopia actually determines the clinical success of cataract surgery. Furthermore, such a distribution can also provide higher overall light efficiency when splitting light using a diffraction grating, as shown below. The well-known pinhole effect provides a higher depth of focus due to a small pupil, so a small power shift with a small pupil does not have a negative impact on vision. It is also important that the dominant power for an extremely small aperture of the lens can be accurately selected. Various autorefractometer technologies may measure the postoperative power at various apertures, and changing only the dominant power of 1 mm may create a need to conform to a specific autorefractometer technology.

[0022] Under low light conditions with a slightly larger pupil, the pinhole effect is not an effect that is extremely important for a multifocal lens intended for glasses-free vision to provide strong myopia in addition to hyperopia. For complete glasses-free vision, intermediate vision is also desired.

[0023] Due to the accommodation reflex, the human pupil constricts when looking at nearby objects even in a dark environment. Therefore, the light collected for myopia with a large pupil cannot be physiologically used. Intermediate vision is not as troubled by this problem, but, on balance, the reduction of light towards myopia for a large aperture is much more important than the reduction of intermediate vision. Designing according to this principle ensures the physiological efficiency of light in addition to the technical light efficiency.

[0024] Accordingly, there is a need for an improved ophthalmic lens that utilizes the advantages of a symmetric diffraction grating to enable the precise placement of the dominant optical power for a small aperture and to enable an appropriately adjusted energy distribution over a range of the aperture to ensure the physiological efficiency of the incident light, including a very high light efficiency. Summary of the Invention Problems to be Solved by the Invention

[0025] A first object of the present invention is to provide an ophthalmic multifocal lens that includes a refractive baseline and an optical axis and provides at least three foci, one of which provides the user with a distant vision.

[0026] Another object of the present invention is to provide an ophthalmic multifocal lens having at least a first portion and a second portion, the portions being arranged concentrically around the optical axis, with the first portion being the innermost.

[0027] A further object of the present invention is to provide an ophthalmic multifocal lens comprising a symmetric diffraction grating that provides at least three foci in combination with the second portion, the 0th order of the diffraction grating adding to the optical power of the second portion, while the first portion has the resulting dominant power that is between the intended distant vision power and the intermediate vision power for the design wavelength.

[0028] Yet another object of the present invention is to provide an ophthalmic multifocal lens that provides the ability to combine increased diffraction efficiency with a more anatomically accurate use of an optical lens using a symmetric sine wave diffraction grating, and the energy distribution is appropriately adapted for each aperture.

[0029] Yet another object of the present invention is to provide an ophthalmic multifocal lens that enables in vivo measurement of the lens in a lens portion having a refractive power different from the refractive baseline of the second portion with retained efficiency.

[0030] A further object of the present invention is to provide an ophthalmic multifocal lens with optimized multifocality in which the diffraction efficiency is significantly improved.

Means for Solving the Problems

[0031] In a first aspect, an ophthalmic multifocal lens is provided that includes at least a focus for distance vision. The lens has a light-transmissive lens body that includes a symmetric (i.e., the optical power is symmetrically aligned about the zero order) diffraction grating that extends concentrically in a radial direction from the optical axis of the lens body across a portion of the surface of the lens body. The lens includes at least a refractive baseline and at least a first portion and a second portion, these portions are arranged concentrically around the optical axis, and a concave shape in the center of the first portion is superimposed on the refractive baseline, providing an optical power between the intended distance vision power and the intermediate vision power. In the second portion, the symmetric diffraction grating superimposed on the refractive baseline is configured such that, for the design wavelength, the zero order of the symmetric diffraction grating substantially coincides with the power of the refractive baseline and the intended intermediate power of the lens.

[0032] The present disclosure provides that by carefully controlling the dominant power in the central region of the multifocal lens with a symmetric diffraction grating, and further by carefully controlling the exact shape and height of each ridge of the symmetric diffraction grating, the relative energy provided for myopia is higher for an aperture of about 3 mm than for apertures of 2 mm and 4.5 mm, and the relative myopic energy of 5 mm or more is suppressed below the intermediate energy, enabling the production of a lens that provides extremely high diffraction efficiency and higher physiological light efficiency, based on the insight.

[0033] As described above, a diffractive lens having a continuous and smooth profile without sharp edges is less affected by glare or scattering due to the non-uniformity of the path through which the incident light passes through the lens. Also, for example, compared to sawtooth or binary gratings and reliefs, it is easier to manufacture according to the calculated profile and generates less halo. In any case, higher diffraction efficiency results in less stray light. In manufacturing techniques based on diamond turning or similar forms of machining, a smooth profile is more reliable, faster, and cheaper to manufacture than a profile with sharp edges such as a sawtooth profile or a binary profile.

[0034] For example, in the manufacture of ophthalmic lenses by microfabrication or diamond turning, an important step is mechanical polishing to remove cutting marks. To comply with the quality requirements and medical regulations for intraocular lenses, it is necessary to remove all visible cutting marks. However, obtaining extremely low levels of cutting marks requires expensive machinery and slow cutting. When polishing the lens after cutting, the machine can be operated at high speed. Sharp corners, corners, or edges in the height profile of the diffractive lens complicate the process of mechanical polishing. If mechanical polishing is not possible from the perspective of the lens height profile, it is necessary to utilize chemical polishing that requires harmful chemicals or to manufacture the lens without the need for polishing. The latter significantly increases the manufacturing cost due to one or both of lower yield and more expensive machinery.

[0035] The smooth diffractive geometry according to the present disclosure enables polishing and thus results in a significant increase in yield compared to lenses having sharp transitions in these height profiles.

Brief Description of the Drawings

[0036] The accompanying drawings are provided only for the purpose of illustrating a multifocal aphakic diffractive multifocal lens, and the advantages over the prior art are outlined as above and briefly described below.

[0037] The drawings are not intended to limit the scope of protection specified within the claims and should not be referred to alone for interpreting the scope specified in the claims without relying on the technical disclosure in the description of the present invention.

[0038]

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DETAILED DESCRIPTION OF THE INVENTION

[0039] 10 eyes 11 cornea 12 pupil 13 natural lens 14 retina 15 posterior cavity 16 anterior and posterior chambers 17 distance vision 18 intermediate vision 19 near vision 20 optical axis 29 optical axis 30 ophthalmic lens 31 lens body 32 haptic 33 central part 34 front surface 35 rear surface 36 diffraction grating 37 optical diameter 38 outer diameter 39 central thickness 40 lens 41 lens body 42 diffraction grating 43 DOE 44 light-receiving surface 45 central part 46 primary ray 47 secondary ray 48 optical axis 50 multifocal intraocular lens 51 central lens part 52 symmetric multifocal grating 53 peripheral lens part 54 front surface 55 rear surface 56 lens body 150 lens body surface 151 symmetric multifocal diffraction grating 152 single-focus central zone 153 transition point 154 intermediate vision focus 155 distance vision focus 156 near vision focus

[0040] Most of the ophthalmic diffractive trifocal lenses use a sawtooth profile. Combining the sawtooth profiles of two diffractive doublet lenses to achieve trifocality is known in the art. As a result, a diffractive lens with available orders asymmetrically arranged with respect to the zero order is obtained. For example, a trifocal lens may use orders 0, +1, +2 or 0, +2, +3. Such diffractive gratings are hereinafter referred to as asymmetric gratings.

[0041] One important characteristic of a diffractive grating is the distinction between a symmetric diffractive grating and an asymmetric diffractive grating. When attributing symmetry or asymmetry to a multifocal ophthalmic lens, the consideration is which orders are used or made useful. A symmetric diffractive lens utilizes the orders in a symmetric manner about the zero order. Note that a symmetric diffractive grating is defined by which orders are utilized, rather than the intensity of the light distribution at these orders. Some symmetric diffractive lenses may be adjusted, for example, such that there is a significant difference in light intensity between the +1 order and the -1 order, i.e., having an unequal light distribution. Such an adjusted diffractive grating is still considered a symmetric diffractive grating. The most symmetric gratings described in this document use odd consecutive orders and the zero order. For example, the grating used for a trifocal lens using orders -1, 0, +1, or the grating for a pentafocal lens utilizing orders -2, -1, 0, +1, +2. However, a grating that does not use the zero order can also be considered symmetric. Specifically, the symmetric case of a grating using four orders -2, -1, +1, +2 can, in some cases, be useful for an ophthalmic lens.

[0042] The highest possible diffraction efficiency for the most useful intensity distribution for diffractive multifocal lenses with an odd number of foci, including trifocal lenses, is provided by a smooth sinusoidal surface with available orders symmetrically arranged about the zero order.

[0043] When comparing diffractive surfaces, an important factor is the diffraction efficiency. The diffraction efficiency is a measure of how much of the optical power is directed towards the desired diffraction order, or, particularly for a diffractive lens, how much of the optical power is directed towards the desired focal point. In a bifocal lens, the surface of the lens body is optimized to provide the best possible vision at two different distances, and the highest possible diffraction efficiency is achieved by using the principle of the phase-matched Fresnel lens, which uses a sawtooth or jagged diffraction pattern. Reference is made to the document ("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 incorporated herein by reference.

[0044] This field has well-developed theories and is available for diffractive lenses, so it is often convenient to first consider linear phase gratings. In the special case of a triple-focus linear grating with an equal intensity distribution for each order, the optimum solution is shown in detail in the document ("Analytical derivation of the optimum triplicator", by F. Gori et al., in Optics Communication 157 (1998), p. 13-16), which is incorporated herein by reference.

[0045] The literature ("Theory of optimal beam splitting by phase gratings. I. One-dimensional gratings", by L. A. Romero and F. M. Dickey, in Journal of the Optical Society of America Vol. 24, No. 8 (2007) p. 2280-229) is incorporated herein by reference and discloses more generally, and at least demonstrates that the optimal grating for equal splitting into odd orders has a continuous profile. This latter literature provides a mathematical tool for finding the optimal linear phase grating for any given set of target orders and any given intensity distribution between those target orders. The optimal grating is defined as a linear diffraction grating with the highest diffraction efficiency for a particular intensity distribution. Note that the literature (Gori et al.) and the literature (Romero et al.) discuss linear phase gratings only with the intention of generating beam splitters. By treating the x-axis of the linear grating as the r2 space of a diffraction lens, such linear phases can be adjusted to the lens. Using the theory from the study by the literature (Romero, Dickey), it is possible to define the target orders and the relative intensity distribution of the individual orders and find the equation of the optimal (most efficient) grating for those input values. Furthermore, at least symmetric gratings with a continuous set of orders have been shown to have an optimal grating without discontinuities for relatively even intensity distributions. Some symmetric gratings with a discontinuous set of orders also have a grating without discontinuities. Although only gratings with an even intensity distribution are shown in the study by the literature (Romero, Dickey), it is also documented that the provided theoretical gratings with a non-uniform distribution can be used. It should be noted that this is a specific method of optimizing the linear phase grating. Furthermore, since there are specific effects on the lens that are not considered by some optimizations of the linear phase grating, it is advantageous to optimize these effects when designing the lens according to the present invention.

[0046] One important part of the lens design according to the present invention is to find a set of symmetric diffractive unit cells without discontinuities that can be used together to provide the desired intensity distribution. In this field, there are various methods for calculating and adjusting symmetric diffractive lenses. One method is to use an optimized linear grating converted into a diffractive lens, as described above and as described in PCT / EP2019 / 080758. One early example of a lens based on a symmetric diffractive grating is the 7-focal lens described in the literature (Golub et al., "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 Osipov2015 study and the literature published in 2012 (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.). These documents disclose triple-focus symmetric lenses fabricated by changing to a sinus lattice. In these Osipov2015 studies, only one unit cell is used per lens, but using our knowledge, a diffractive grating for a suitable adaptive lens can be constructed from a set of modified sinus lattices fabricated as described. Different methods are also disclosed in US5760871A and IL104316, using the so-called asymmetric super-Gaussian formula to design a triple-focus grating with a non-uniform intensity distribution. Such a set of diffractive unit cells can be used with a suitable transition zone to form a suitable diffractive grating for the adaptive lens according to this patent. Still another method is the one described in WO2020053864A1, which uses the Gerachberg-Saxton iterative algorithm to design the surface profile of a five-focus (having five foci) lens with a symmetric diffractive grating.

[0047] The lens according to the present invention is an ophthalmic lens including at least a refractive baseline and at least a first part and a second part arranged concentrically around an optical axis. Therefore, the concave shape at the center of the first part is superimposed on the refractive baseline, providing an optical power between the intended powers of far vision and intermediate vision. In the second part, a symmetric diffraction grating superimposed on the refractive baseline is configured such that the zero order of the symmetric diffraction grating for the design wavelength substantially coincides with the power of the refractive baseline and the intended intermediate power of the lens.

[0048] The proposed multifocal ophthalmic lens addresses the problems known in this field. That is, as long as a symmetric multifocal diffraction grating is applied, some problems tend to present themselves, such as a combination of a single - focus central zone (providing only far vision) and a multifocal grating with a fixed diffraction efficiency optimized for a 3 - mm aperture, which, as is known in this field, results in an unbalanced lens, and near vision becomes particularly overly strong for large apertures. Another of these technical difficulties to be solved is that when a precisely single - focus central zone with optical power exactly coincides with the diffractive foci responsible for far vision, it results in a reduction in overall efficiency.

[0049] Despite the difficulties described above, strong far vision is a typical measure for confirming the success of cataract surgery. This is because strong far vision is important for all apertures.

[0050] Thus, the disclosed invention specifically relates to the creation of an adaptive multifocal lens including a symmetric multifocal diffraction grating. Here, adaptability is defined as a measure of the functional light utilization of the human eye. Due to the pinhole effect, the smaller the pupil size, the greater the depth of field of the eye. The pupil size depends not only on the pupillary light reflex but also on the accommodation reflex, which ensures that the pupil does not fully dilate while focusing on closer objects. Further, the disclosed invention addresses this issue by adjusting the power of the central portion of the multifocal lens to maintain a 1 mm inner aperture that basically provides distant vision while increasing its efficiency, thus increasing the success rate of cataract surgery. This will be detailed below.

[0051] According to the literature (Kanellopoulos and Asimellis, titled "Clear-cornea cataract surgery: pupil size and shape changes, along with anterior chamber volume and depth changes. A Scheimpflug imaging study." Clinical Ophthalmology (Auckland, NZ) 8 (2014): 2141), cataract surgery reduces the clear pupil by an average of 0.27 mm. Furthermore, since it can be measured by optical examination, the pupil size reported in the medical literature is often the apparent pupil. However, the more relevant pupil is the anatomical pupil (phakic eye) located closer to the natural lens. From the study of the literature (Kanellopoulos and Asimellis), the apparent pupil can be regarded as the entrance pupil of the eye's optical system, while the anatomical pupil is the aperture stop. According to the model of the above-mentioned study, the apparent pupil is 13.1% larger than the anatomical pupil. This, of course, will vary among individuals and among environmental conditions. The aperture referred to in this specification is the physical aperture of the eye, specifically for aphakic and pseudophakic eyes. In the medical literature, the naturally occurring pupil size is often 2 mm to 8 mm, but for IOLs, the relevant aperture size is often at most 5 mm in diameter and at most 6 mm.

[0052] In addition to the pupillary light reflex, the pupil also responds to the accommodation reflex. The accommodation reflex is a response to focusing on a nearby object, and one of its effects is to constrict the pupil. Due to this latter effect, the pupil does not become too large even under dark conditions when focusing on a nearby object. Therefore, the additional near vision provided by the intraocular lens with a large pupil is mostly wasted and ideally not provided.

[0053] For small pupil sizes, it is important to consider the pinhole effect. Pupil constriction increases the depth of focus of the lens, and for small pupils, this effect generally provides a lens that offers a single focus for relatively good vision at all distances. Many of the latest multifocal and extended depth of focus (EDOF) lenses utilize this effect by having the light provided by the lens be dominated by intermediate or near vision. The argument is that for a small aperture, when this is provided at the center of the lens, it works well enough for the user in bright conditions due to the large depth of field, while this intensity provided for near and / or intermediate vision can be used especially for low light conditions with a slightly larger pupil size. An example of a non-diffractive higher power in the central region where the power decreases as the radius increases is disclosed in US10028825, and a so-called continuous power progressive intraocular lens introduces a power that changes without using a sharp step. This is acceptable but not an ideal solution. Excellent distance vision is considered the most important parameter of the IOL because the quality of distance vision actually determines the clinical success of cataract surgery. For this reason, it is important for the IOL to provide strong distance vision for all apertures, with the exception of extremely small pupils. Furthermore, ophthalmologists often predict that the autorefractor will measure the distance vision of the postoperative eye, and the central power overly removed from the distance power of the lens can cause confusion in the evaluation of cataract surgery success. However, for extremely small apertures, a small power shift towards a stronger diopter can be used to increase the so-called landing zone or sweet spot to increase the chance of clinical success, but in an ideal case, this shift should not be so large as to reach all the way up to an intermediate addition (between about 1.5D and 2.2D), nor should it be so large as to reach up to a near addition (between about 3D and 4.4D). The ideal shift at a 1mm aperture should be less than 1.2D, and in either case, the dominant focus at 1mm should be less than that of the intended intermediate power. Here, it should be noted that at a 1mm aperture, usually there is no multifocality developed.The measured intensity or MTF curve will have one dominant peak.

[0054] On the other hand, the addition of myopic power and intermediate power is important for low light conditions in order to enable the available vision over a wide range. Usually, it is desirable to maintain myopic vision stronger than intermediate vision in order to provide good reading ability without using glasses.

[0055] And what is desirable is a multifocal lens, the multifocality is provided by a multifocal symmetric grating, and for a small pupil (e.g., 1 mm), the dominant focus should correspond to a far vision with an optical power slightly stronger than the intended far vision power, or at least weaker than the intended power of the intermediate vision. For a 2 mm aperture, well-developed multifocality (at least three foci) should exist. For a pupil size of about 3 mm, the ideal diffractive multifocal lens should provide strong far vision, strong near vision, and some intermediate vision. For pupils larger than 4.5 mm, the energy directed towards near vision cannot be fully utilized by the eye. Therefore, the additional energy directed towards near vision should be minimized or made small, and the energy towards near vision for a 4.5 mm pupil should be smaller than both intermediate and near vision.

[0056] FIG. 1 shows, for the purpose of explaining the present disclosure, in a simplified manner the biological structure of a human eye 10. The front part of the eye 10 is formed by a spherical transparent tissue covering the cornea 11 and the pupil 12. The pupil 12 is an adaptable light receiving part of the eye 10 that controls the amount of light received by the eye 10. The light rays passing through the pupil 12 are received by the natural lens 13, a small transparent and flexible disk inside the eye 10, and the light rays are focused onto the retina 14 at the rear part of the eye 10. The retina 14 helps in image formation by the eye 10. The posterior chamber 15, i.e., the space between the retina 14 and the lens 13, is filled with vitreous humor, a transparent and jelly-like substance. The anterior-posterior chamber 16, i.e., the space between the lens 13 and the cornea 11, is filled with aqueous humor, a transparent and watery liquid. The reference numeral 20 indicates the optical axis of the eye 10.

[0057] In a clear and distinct far vision by the eye 10, the lens 13 needs to be relatively flat, while in a clear and distinct near vision, the lens 13 needs to be relatively curved. The curvature of the lens 13 is controlled by ciliary muscles (not shown) that are sequentially controlled from the human brain. A healthy eye 10 can adjust, i.e., control, the lens 13 in a way that provides a clear and distinct vision of an image at any distance in front of the cornea 11 between the far vision and the near vision.

[0058] An ophthalmic lens or an intraocular lens is worn in combination with the lens 13 to correct the vision by the eye 10. In this case, the ophthalmic lens is positioned in front of the cornea 11 or replaces the lens 13. In the latter case, it is also shown as an aphakic ophthalmic lens.

[0059] A multifocal ophthalmic lens is used to enhance or correct the vision by the eye 10 for various distances. For example, in the case of a trifocal ophthalmic lens, the ophthalmic lens is arranged for a clear and distinct field of vision at approximately three separate distances or focal points, often including far vision, intermediate vision, and near vision, respectively indicated by reference numerals 17, 18, and 19 in FIG. 1. Far vision is an optical term when the incident light rays are parallel or nearly parallel. Light rays emitted from an object placed at or near these distances or focal points 17, 18, 19 are correctly focused on the retina 14, i.e., a clear and distinct image of these objects is projected. The focal points 17, 18, 19 can actually correspond to focal lengths in the range from several meters to several tens of centimeters, and down to several centimeters. Usually, an ophthalmologist selects a lens for a patient such that the far focal point allows the patient to focus on parallel light, which in ordinary optical terms means that the far focal point is focused at infinity. When examining a patient, an ophthalmologist usually measures the near vision at a distance of 40 cm from the eye and the intermediate vision at a distance of 66 cm from the eye, although other values can also be used.

[0060] The correction amount provided by an ophthalmic lens is called the optical power OP and is expressed in diopters D. The 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 individual foci for distance vision 17, intermediate vision 18, and near vision 19. For example, the optical power of a cascade (in series) of multiple lenses is obtained by adding the optical powers of the constituent lenses. The optical power of the lens 13 of a healthy human is about 20D.

[0061] Figure 2a shows a top view of a typical ophthalmic multifocal intraocular lens 30, and Figure 2b shows a side view of the lens 30. The lens 30 includes a light-transmissive circular disk-shaped lens body 31 and a pair of haptics 32 extending outward from the lens body 31 to support the lens 30 within the human eye. Note that this is an example of a haptic, and there are many known haptic designs. The lens body 31 has a biconvex shape including a central portion 33, a front surface or front face 34, and a rear surface or back face 35. The lens body 31 further includes an optical axis 29 extending through the center of the central portion 33 across the front surface 34 and the rear surface 35. Those skilled in the art will understand that the optical axis 29 is a virtual axis for the purpose of referring to the optical characteristics of the lens 30. The convex lens body 31 provides a refractive optical power of about 20D in an actual embodiment.

[0062] In the illustrated embodiment, on the front surface 34 of the lens body 31, a periodic light-transmissive diffraction grating or relief 36 consisting of a ring or zone extending concentrically with respect to the optical axis 29 passing through the central portion 33 is disposed over at least a part 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 be disposed on the rear surface 35 of the lens body 31 or both surfaces 34, 35. In fact, the diffraction grating 36 is not limited to concentric or annular ring-shaped zones, but includes concentric elliptical or oval-shaped zones, for example, more generally any type of concentrically rotating zone shape.

[0063] In fact, the optical diameter 37 of the lens body 31 is about 5 - 7 mm, and the total outer diameter 38 of the lens 30 including the haptic 31 is about 12 - 14 mm. The lens 30 may have a central thickness 39 of about 1 mm. In the case of ophthalmic multifocal contact lenses and glasses or spectacle lenses, the haptic 32 in the lens body 31 is not provided, but the lens body 31 may have a plano-convex shape, a biconcave shape, or a plano-concave shape, or a combination of convex and concave shapes. The lens body may include any of hydrophobic acrylic, hydrophilic acrylic, silicone material, or other suitable light-transmissive materials for use in the human eye in the case of aphakic ophthalmic lenses.

[0064] Figure 3 schematically shows the optical operation of a known periodic light-transmissive diffraction grating or relief 42 of a lens 40 including a biconvex light-transmissive circular disk-shaped lens body 41. This type of lens is also called a hybrid lens as it combines refractive power and diffractive power. The lens 40 is shown in a cross-sectional view in the radial direction of the lens body. The diffraction grating or relief 42 includes a plurality of repeating adjacent prism-shaped transparent diffractive optical elements DOE43. The DOE43 extends in concentric zones around the central portion 45 of the lens body 41 in a manner similar to the rings or zones of the grating or relief 36 shown in Figure 2a. For illustrative purposes, the DOE43 of the diffraction grating 42 is shown as a well-known jagged or sawtooth-type element including a continuous inclined receiving surface 44 such as a straight or curved inclined receiving surface 44. A grating or relief in which the DOE43 alternates back and forth between two heights and is spaced radially from the lens body 41 is called a binary-type relief (not shown). The repeating period or pitch of the DOE43 monotonically decreases radially from the center or optical axis of the lens and varies with the square of the radial distance.

[0065] The pitch depends on the refractive index, the design wavelength, and the optical power of the first diffraction order. The pitch is determined such that the optical path difference (OPD) through the lens to the focus of the first diffraction order has exactly one wavelength difference per period. To show the periodicity of the diffraction grating, the diffraction lens profile is often plotted against the square of the radius. When plotted in this way, the period (grating pitch) is equidistant, and the period pitch in the r2 space is |2λf|. Here, λ is the design wavelength and f is the reciprocal of the optical power of the first diffraction order.

[0066] In this field, one surface of the lens is purely refractive and the other surface has a diffraction grating superimposed on the refractive baseline. The refractive baseline may be, for example, spherical or may have a certain aspherical shape. The diffraction pattern is added on the refractive baseline and may generally be applied to either of the two surfaces of the lens. Therefore, when combining the diffraction pattern with a refractive surface having certain special features, it is generally not very important whether they are added to the same surface, or one is added to the first surface and the other is added to the second surface of the lens. At the same time, two diffraction patterns may be combined by superimposing them on one surface or by adding them so that they overlap on separate surfaces. In the disclosure related to the present invention, it should always be understood that combining two lens structures enables both possibilities. The optical power of a lens of a specific diffraction order can be calculated by adding the refractive base power and the optical power of that diffraction order.

[0067] The incident light rays or primary light rays 46 passing through the grating 42 and the lens body 41 are diffracted and refracted respectively, generating output light rays or secondary light rays 47. The refracted and diffracted light rays 47, i.e., the secondary light rays, form multiple foci on the optical axis 48 of the lens 40 due to the constructive interference of the light waves 47. When the optical path difference between the light waves 47 reaching from the lens body 41 at a specific focus is an integral multiple of its wavelength, constructive interference occurs, i.e., the light waves are in phase, and their amplitudes are added so as to be enhanced. When the difference in the optical path lengths traveled by interfering the light waves 47 from the lens body 41 is an odd multiple of half the wavelength, the peak of one wave meets the valley of another wave, and the light waves 47 partially or completely cancel each other out, i.e., the light waves are out of phase and do not form a focus on the optical axis 48 of the lens body 41.

[0068] The points of constructive interference at various distances from the lens body 41 are generally referred to as diffraction orders. The focus corresponding to the focus caused by the refractive action of the curvature of the lens 40 is indicated by order zero, 0. Other foci are called order +m and -m (m is a positive integer value), i.e., m = +1, +2, +3, etc., when the individual foci occur at a certain distance to the left of the zero order, i.e., in the direction towards the lens body 41, when viewed within the plane of the drawing, and are called order m = -1, -2, -3, etc., when the individual foci occur at a certain distance to the right of the zero order, i.e., in the direction away from the lens body 41, when viewed within the plane of the drawing. For example, as shown in FIG. 3.

[0069] It should be noted that the above assignment of positive and negative diffraction orders in some publications and handbooks may be reversed with respect to their positions relative to the zero order. This is the case here even when directly applying the theory in the publication Romero et al., for example. Unless otherwise indicated, this specification follows the convention as shown in FIG. 3.

[0070] Diffractive relief 42 can be designed to provide foci at various distances from the lens body 41. The periodic spacing or pitch of the DOE 43 substantially determines the location where the points of destructive and constructive interference occur on the optical axis 48 of the lens, i.e., the position of the diffraction order on the optical axis 48. The shape and height of the DOE 43 control the point of constructive interference, i.e., the amount of incident light provided at a specific diffraction order.

[0071] In the case of a diffraction grating or relief 42 that provides regularly spaced diffraction orders on both sides of the zero order, the grating or relief is called a symmetric light wave splitter or diffraction grating, and the incident light ray 46 is diffracted or split into orders symmetrically arranged with respect to the zero order. A grating or relief that produces an irregular spacing of diffraction orders, such as +1, +2, -3, -5, etc., is called an asymmetric diffraction grating. The ordinary case of a diffraction grating that can be used at the 0 order and the +1 order, or at the 0 order, the +1 order, and the +2 order, is also an asymmetric diffraction grating.

[0072] The optical energy of light waves (secondary light rays 47) that are focused or diffracted at foci or orders that do not contribute to image formation on the retina 14 of the human eye 10 is lost, reducing the overall efficiency of the lens 40 and the quality of the image perceived by a human using such a lens. In fact, for optimal design of the lens, it is advantageous, for example, as shown in FIG. 1, if foci for providing or correcting myopia, intermediate vision, and hyperopia to the human eye can be preset. A diffraction grating 42 is provided that maximizes the overall efficiency of the optical energy received from the incident light ray 46 at these preset foci.

[0073] In the scientific literature, a diffraction grating that optimizes the overall efficiency of the light distribution at a preset or target diffraction order is found by determining a linear phase-only function or phase profile that generates a target diffraction order at which the overall efficiency η or figure of merit, defined as the sum of the normalized optical energies of all these target orders, is maximized. And these diffraction gratings can be shaped onto the lens by adjusting the arguments so as to have equidistant periods in the r2 space.

[0074] One skilled in the art will understand that the lens body 41 may include plano-convex, biconcave or plano-concave shapes, as well as combinations of convex and concave shapes or curvatures (not shown).

[0075] Figures 4a and 4b show the lens according to PCT / EP2019 / 080758 and the functionality of said lens by combining a single-focus central zone and a symmetric multifocal lattice. Figure 4a shows, as an example, the height profile or amplitude profile of another embodiment of a trifocal ophthalmic lens according to the present disclosure along a linear scale as a function of the radial distance r expressed in millimeters. The amplitude profile or height profile of the embodiment of the ophthalmic lens shown in Figure 15a includes the surface of the lens body 150 and further includes a single-focus central zone indicated by reference numerals 152 and the diffraction grating 151. The optical axis passing through the center of the lens body is assumed to be at a radial position r = 0, while the radial distance r measured in the outward direction from the optical axis is expressed in millimeters along the vertical axis. The reference numeral 160 refers to the outer periphery of the front surface 34 of the lens body 30 as shown in Figures 2a and 2b. The central zone 152 is single-focus and in this example is arranged to have the same power as that of the focus of the diffraction grating 151.

[0076] At the transition point 153, at the radial position of the lens body at a distance of about 0.5 mm from the optical axis, the continuous amplitude profile h(r)152 of the single-focus central zone ends and continues to the symmetric multifocal diffraction grating profile H(r)151 of the diffraction grating. In the illustrated embodiment, the transition point 153 is on the surface 150 of the lens body.

[0077] In this example, it is assumed that the design wavelength λ of the lens is 550 nm, the refractive index n of the lens body is set to 1.492, and the refractive index n_m of the medium surrounding the lens body is assumed to be 1.336.

[0078] Figure 4b shows the intensity simulation of the lens of Figure 4a for four different aperture sizes, 1 mm, 2 mm, 3 mm, and 4.5 mm. The aperture or pupil is assumed to correspond to the double radius of the lens. Energy is shown on a relative scale along the vertical axis, and the maximum number is set to 1 for each aperture. The light intensity distribution of the computer simulation assumes a biconvex lens body of an ophthalmic lens of the type shown in Figures 2a and 2b. The 0th order focal point is targeted to be 20 diopters D respectively, and the focal points for near and far vision are targeted to be 21.675 D and 18.325 D respectively, and are designed to be positioned symmetrically with respect to the 0th order. Reference numeral 154 refers to diffraction order 0 that provides a focus for intermediate vision, reference numeral 155 refers to the focus for far vision at 18.325 D, and reference numeral 156 refers to the focus for near vision at 21.675 D. It can be seen from the graph that the exact positions of these peaks vary slightly with the aperture, and as discussed elsewhere, this effect can be intentionally used in lens design.

[0079] The lens configured in this way provides good far vision even with a very small pupil. In such a design, there are two main drawbacks. First, inserting a single - focus central zone into the diffraction grating reduces the diffraction efficiency. Second, when using this architecture to provide full vision (including far, intermediate, and near vision), for example, it is necessary to balance the intensity distribution to provide a desired intensity distribution for bright - field conditions, such as for an aperture diameter of 3 mm. In a trifocal lens, this typically involves providing a stronger far vision compared to other distances, but also a relatively strong near vision and some intermediate vision. Due to the skew towards the near vision required by the diffraction grating to form a strong far vision at the center, such a design leads to relatively too much near - vision energy that is too strong for larger apertures.

[0080] Figure 5a shows a top view of an ophthalmic multifocal intraocular lens 50 operating in accordance with the present invention, and Figure 5b shows a side view of the lens 50. The difference from the prior art illustrated in Figure 2 is the optical system of the lens. The lens body 56 has a biconvex shape including a front surface or front face 54 and a rear surface or back face 55. Those skilled in the art will appreciate that in some embodiments, depending on the refractive baseline required for a particular application, one or both of the front surface 54 and the rear surface 55 may be concave or planar. In the present application of the present invention, the lens body according to the present disclosure includes a peripheral lens portion 53 and a central lens portion 51 combined with a symmetric multifocal diffraction grating 52. The lens is configured such that, at the design wavelength, one of the diffraction orders of the symmetric multifocal diffraction grating 52 contributes to the distance vision of the lens, the zero order of the symmetric multifocal diffraction grating contributes to the intermediate vision of the lens, and still other diffraction orders contribute to the near vision. In some embodiments, the symmetric multifocal grating has three foci, and in other embodiments, the number of foci is a larger odd number, such as 5, 7, or 9. The central lens portion 51 has a dominant major optical power somewhere between the power of the intermediate vision and the power of the distance vision. Figures 5a and 5b show a lens in which one side of the lens is purely refractive and the other side has a diffraction grating superimposed on the refractive baseline. As described above in connection with Figure 3, this is only one possible configuration. For example, it is possible to distribute the diffraction grating on both sides, or it is possible to superimpose the diffraction grating on one side of a plano-convex lens or a plano-concave lens. When the diffraction pattern is combined with the refractive surface, it can have any of these meanings.

[0081] The shape or height profile of the refractive baseline for any part of the lens may be selected from a plurality of continuous refractive profiles known from single-focus lenses such as spherical lenses, or may be selected based on a single-focus diffractive surface or an aspherical surface, which are among the most common known shapes of single-focus lenses known in this field. The single-focus diffractive surface refers to the phase-matching Fresnel lens described above. By adjusting the phase-matching number, an arbitrarily wide seamless single-focus zone can be generated by the diffractive optical element. In one lens, it is possible to combine different types of refractive surfaces, and as a result, the central part and the peripheral part are composed of different types of refractive surfaces. The manufacture of the refractive surface and the diffractive surface can be carried out by any of laser micromachining, diamond turning, 3D printing, or, for example, other machining or lithographic surface processing techniques.

[0082] The present invention describes a method of creating a lens that maintains the advantages of the prior art lens of FIG. 4a, increases the diffraction efficiency, and significantly increases the amount of light available for use by the human eye.

[0083] This includes changes to two parts of the lens, the central part of the lens, within an aperture of approximately 1 mm, and the symmetric multifocal diffraction grating. By changing these two structures simultaneously, the desired characteristics can be achieved. FIG. 6 illustrates such possible changes to the central part of the lens profile.

[0084] One very important property of a multifocal lens turns out to be the exact placement of the dominant optical power for a very small aperture, for example, when measured with a 1 mm aperture. Figure 4a shows a lens profile where the optical power of the central zone is perfectly aligned with one of the non-zero orders of a symmetric multifocal diffraction grating, while the central zone in Figure 6a shows the profile of a lens with a single-focus central zone that is slightly adjusted towards the zero order used for intermediate vision. Exactly as in Figure 4a and as in PCT / EP2019 / 080758, the so-called transition point is near the peak closest to the optical axis (the optical axis passes vertically through the center of the lens profile on which this image is plotted), as indicated by the vertical dashed line in the figure.

[0085] The single-focus central zone adds a local negative optical power at the center of the lens with respect to the refractive baseline. In the prior art, it was prohibited that this power should be the same as the absolute power of the diffraction order responsible for distance vision. However, a slight power shift in the single-focus central zone can be used to achieve a better light distribution. It has been found that a small decrease in the power of the central zone has several favorable effects. (1) When precisely selected, it increases the overall diffraction efficiency across all parts of the light available to the eye. (2) It reduces the intensity of unusable light that has a power lower than the intended distance vision. (3) By broadening the peak of vision, it widens the landing zone, for example, in the way of selecting the power at a 1 mm aperture. In some configurations, it can generate an asymmetric peak for the focus providing distance vision. In particular, the widening of the landing zone (sweet spot) due to a slight power shift towards a stronger diopter for a very small aperture can be important for increasing the chances of clinical success.

[0086] Regarding the specific examples presented here, FIG. 6b shows the simulated relative intensity peaks for four different apertures. The power shift reduces the unwanted peak (present here around 17D) and redirects a portion of that light to the zero order (intermediate vision). The peak responsible for distant vision is seen around 18.35D. These features can be compared to FIG. 4b, and the most influential change is the reduction of the unwanted peak around 17D in FIG. 6, which means that more light becomes useful to the eye.

[0087] The lens profile of FIG. 6a uses the same diffraction grating as that of the lens in FIG. 4a, but in FIG. 6a, the central zone has an absolute negative power that is 0.275D less. The symmetric diffraction grating is configured to provide a degree separation of 1.675D. On the other hand, the single - focus central zone has a curvature arranged to add negative power relative to the refractive baseline of the lens, which is 1.4D. As simulated in FIG. 6b, the dominant peak for the small 1 - mm aperture is not at the nominal power of 1.675D of the diffraction order that coincides with distant vision, but at 1.2D below the intended intermediate peak. This increases the overall efficiency and slightly broadens the peak for distant vision. It is an extremely important and useful tool when used the right way.

[0088] A purely single - focal shape has been selected for the central part of these lenses. The reason is that it is advantageous to have a very dominant far - vision with a small aperture and at least a stronger far - vision than others with all larger apertures. However, it is not necessary to use a purely single - focal zone to achieve this. Figures 7a, 7b, and 7c illustrate different selections of the central zone. It is advantageous to use a transition zone between the central part and the diffraction grating located near the peak of the first peak of the diffraction grating. Figure 7a shows such a lens profile. The vertical dashed line in Figure 7a indicates the transition point corresponding to the center of the transition zone. To avoid a sharp change in the profile, there is a smooth transition between the central part targeted precisely for far - vision and the first ridge of the symmetric diffraction grating that is fully trifocal and arranged to be slightly advantageous for near - vision. This specific example is not adding a transition between two heights, but rather making a smooth transition between two zones occur in the parameter space.

[0089] Such central portions can be constructed as aspherical lens segments, as modified spherical segments, or as several spherical segments stitched together, rather than being purely single - focused. Further, it can be calculated by the same means used to calculate the diffractive unit cells for a multifocal symmetric diffractive grating. Several different methods for creating such unit cells have been discussed earlier in this document. When using the latter method, it is often convenient to strongly promote the diffractive foci responsible for far vision and create a unit cell that uses only a portion of that unit cell. The more skewed it is towards far vision, the more it can be fabricated to resemble a purely single - focused lens portion. Near the correct position of the crest closest to the center of the lens, it transitions to a diffractive grating with a substantially different light distribution. In such a lens with a nominal order separation of 1.675D, as in this example, it can be noted that the first grating period, counted from the lens center, ends at an aperture of 1.62mm (a distance of 0.81mm from the center). This is a large portion of the lens and needs to be carefully configured and requires one or more features to achieve the desired light distribution. In this case, the transition point is at an aperture of 1.25mm and a unit cell like that shown in Figure 7c was used for the central zone. This shape is strongly targeted at far vision, as can be seen in a plot of the efficiency distribution of the unit cell in question (here arranged to coincide with the +1 order of the unit cell). However, the portion between the two vertical dashed lines was not used. Instead, the optical axis of the lens approximately coincides with the dashed line on the right side of the image of the unit cell. And the central portion of the lens consists of approximately a portion of the unit cell not shown between the two vertical dashed lines. Near the left - hand vertical line (close to the left shoulder of the unit cell), the lens data is created by a transition within the parameter space. Of course, it is also possible to create a sharp transition between the central zone and the multifocal diffractive grating. For example, as illustrated in Figure 7a, the central zone is essentially single - focused but has a shape more similar to that of a diffractive grating, which increases the overall efficiency of the lens. This further provides an opportunity to adjust the overall efficiency and exact power of the peak at a 1mm aperture.

[0090] Figure 7b shows the simulated relative intensity peaks for four different apertures. The symmetric diffraction grating is configured to provide a degree separation of 1.675D. As simulated in Figure 7b, the dominant peak for the small 1mm aperture is only 0.65D below the intended middle peak. The unwanted peak at 17D is clearly smaller than the corresponding peaks in Figures 4b and 6b and shows a higher efficiency for the lens of Figure 7a. This higher efficiency occurs clearly in the simulation and also in the measurements from the actual lens. However, this graph also very clearly describes the major drawback of the lens of Figure 7a, namely, the high energy directed towards myopia for the large aperture. For the 4.5mm aperture, the myopic energy is here much higher than that for intermediate vision and has a similar intensity to that for hyperopia. Much of this myopic light from the large aperture cannot be used by the eye. So even with a high diffraction efficiency, the physiological light efficiency for the large aperture is much lower than ideal. To solve this problem, what is needed is a fully adaptive lens.

[0091] Figure 8 shows the individual activation of rods and cones in the eye. Due to the luminance level and pupil diameter, cones are dominant under photopic conditions, while rods are dominant under mesopic and scotopic conditions.

[0092] Based on the specific responses of cones and rods in the retina of the eye, three main eye function modes are observed under various illuminance levels (cd / m²), bright light (bright light), dim light (low light conditions), and twilight (intermediate). The luminance levels of the object, background, and periphery being observed determine the activities of rods and cones by the retinal illuminance level (light intensity). Thus, as shown in FIG. 8, the spectral response of the eye is directly related to and affected by the illuminance level to which it is exposed. The pupil size is a linear function of the logarithm (log cd / m²) of the equivalent luminance calculated for a large field of view in order to adapt the luminance from bright light conditions to twilight conditions (additional information can be found in the literature (W. Adrian, "Spectral sensitivity of the pupillary system," Clin. Exp. Optom., vol. 86, no. 4, pp. 235-238, 2003)).

[0093] The pupil size plays an important role in achieving the functional visual acuity level in pseudophakic eyes. This is because the eye cannot generate refractive changes in response to the proximity of an object. The pupil diameter is a major predictor for increased pseudoaccommodation and near vision, and reading performance by determining the retinal blur area and depth of field (see the literature (E. Fonseca, P. Fiadeiro, R. Gomes, A. S. Trancon, A. Baptista, and P. Serra, "Pupil function in pseudophakia: Proximal miosis behavior and optical influence," Photonics, vol. 6, no. 4, 2019)).

[0094] Diffraction is the dominant limiting factor at small pupil diameters, while at large sizes, aberration is more involved in retinal blur (see reference (A. Roorda and D. R. Williams, "The arrangement of the three cone classes in the living human eye," Nature, vol. 397, no. 6719, pp. 520-522, 1999)). Figure 9 shows the typical point spread function (PSF) of the eye as a function of pupil size. Studies have shown that the balance between diffraction (blurring the image for small pupils) and aberration (affecting lateral resolution) lies somewhere between 2 mm and 4 mm pupil size, depending on the individual (see reference (A. Roorda et al., "What can adaptive optics do for a scanning laser ophthalmoscope?", Bull. Soc. Belge Ophtalmol., no. 302, pp. 231-244, 2006)). The greater aberration for large pupils is also another reason why light towards near vision is not physiologically available.

[0095] Figure 9 shows the point spread function (SPF) for various eyes and conditions. The top row shows the point spread function of an eye without aberration. As the pupil size increases, the size of the PSF decreases, offering the potential for higher resolution. The bottom row shows the point spread function of an eye with typical aberration. In this case, especially for larger pupil sizes, the PSF is blurred.

[0096] Furthermore, pupil size is a function of accommodation stimulus position for various ages (see reference (J. F. Zapata-Diaz, H. Radhakrishnan, W. N. Charman, and N. Lopez-Gil, "Accommodation and age-dependent eye model based on in vivo measurements," J. Optom., vol. 12, no. 1, pp. 3-13, 2019)). The correlation between maximum pupil size and age represents a decrease of -0.23 mm in distance pupil diameter per decade of life, such that individuals in their 50s show an average pupil of 5.0 mm and individuals in their 80s show an average pupil of 4.1 mm (see reference (E. Fonseca, P. Fiadeiro, R. Gomes, A. S. Trancon, A. Baptista, and P. Serra, "Pupil function in pseudophakia: Proximal miosis behavior and optical influence," Photonics, vol. 6, no. 4, 2019)).

[0097] For example, due to traumatic eye conditions such as cataract surgery, the ability of the pupil system to dilate may be reduced. Thus, pseudophakic eyes do not dilate as much as normal under static illuminance conditions in the dark, low light, and light (see reference (H. K. Bhatia, S. Sharma, and P. Laxminarayana, "Ophthalmology and Clinical Research Report ClinMed International Library," pp. 2-5, 2015), reference (A. J. Kanellopoulos, G. Asimellis, and S. Georgiadou, "Digital pupillometry and centroid shift changes after cataract surgery," J. Cataract Refract. Surg., vol. 41, no. 2, pp. 408-414, 2015)).

[0098] Furthermore, the measurement conditions may affect the retinal illumination level. The most scientific studies are based on monocular pupil measurement, but in fact, binocular vision should be used to evaluate IOL performance. Binocular dynamic pupillometry is necessary to accurately determine pupil size under binocular conditions. Light stimulation is known to cause more pupil constriction than monocular vision because the indirect reflection of the binocular pupil system is added to the direct reflection for monocular stimulation.

[0099] If the surgeon can accurately and reproducibly determine the preoperative pupil size, they can predict the postoperative pupil size that affects the refractive outcome and subsequent patient satisfaction after cataract surgery. This is the basis of pupil-customized cataract surgery (PCCS), which means predicting and maximizing postoperative visual performance and subsequent patient satisfaction through preoperative evaluation of the pupil size of cataract patients (see the literature Cataract surgery: Maximizing outcomes through research by H. Bissen-Miyajima, M. P. Weikert, and D. D. Koch, published in 2014).

[0100] As previously mentioned, the visual system is more sensitive to light incident through the center of the eye's pupil than to light incident from around the pupil due to SCE. SCE can significantly improve defocus (blurred focus) image quality and defocus vision, especially for tasks that require adaptive phase perception.

[0101] These findings are clinically useful when evaluating visual performance after cataract surgery and are important in terms of IOL design. Diffractive multifocal intraocular lenses provide visual acuity for distance, intermediate, and near vision. The ideal energy distribution among these differs for various pupil sizes. For small pupils, the dominant focus should be on distance vision with a slightly stronger optical power compared to distance vision. For a pupil size of about 3 mm, an ideal diffractive multifocal lens should provide strong distance vision, strong near vision, and some intermediate vision. For pupils larger than 4.5 mm directed towards near vision, the eye cannot be used well. Therefore, as little additional energy as possible should be directed towards near vision, and the energy going towards near vision for a 4.5 mm pupil should be less than that for both intermediate and distance vision.

[0102] Therefore, an ideal multifocal intraocular lens should distribute light energy between foci such that, at low mesopic illumination levels, approximately 80% of the light energy is directed towards distance and near vision, while at scotopic illumination levels, this approximately 80% of the light energy is ideally distributed between distance and intermediate vision.

[0103] Figure 10a shows an example of a lens according to the present invention. In order to obtain a fully adapted lens, the intensity distribution of the diffraction grating should vary as a function of the distance from the optical center. Figure 10a shows a lens profile (low refractive base line) that is substantially concave and strongly promotes hyperopia, but uses a central zone adjusted to better harmonize with the multifocal grating of the lens. A transition point at an aperture of 1.25 mm near the first peak is introduced into a symmetric multifocal grating consisting of a set of differently adjusted diffraction unit cells. The first period outside the central part constitutes a relatively balanced diffraction grating that promotes myopia more than intermediate and hyperopia, and this transitions in several steps to a diffraction grating that strongly promotes hyperopia with increasing distance from the optical center and particularly discriminates against myopia for both hyperopia and intermediate vision. Of course, in the region of the lens between the central part and the approximately 3 mm aperture, even if myopia is slightly favored, due to the central part that promotes hyperopia, hyperopia has a dominant intensity share for all pupil sizes in this range.

[0104] Of course, it is possible and often useful to create an adaptive lens having a fully monofocal central zone, such as that of Figure 6a for example. In such a configuration, a precisely defined focus for all diameters results in an adaptive lens that is smaller than that of the transition point. An adaptive lens using a precise monofocal central zone has a slightly lower overall optical efficiency compared to the type of lens described in Figure 10, but lens designs with a precise monofocal central zone have actually been shown to be more robust in response to manufacturing and material perturbations. Material perturbations can be slight differences in refractive index between material batches. The monofocal central zone can also have several advantages for postoperative autorefractometer measurements. For these reasons, the choice of the central zone needs to be made on a case-by-case basis.

[0105] Figure 10b shows the relative intensity peaks simulated for four different apertures. The symmetric diffraction grating is configured to provide a nominal order separation of 1.675D. However, as shown in the simulation data, the dominant peak at the small 1mm aperture is 0.6D below the intended intermediate peak. Summarizing the data in Figure 10b, (1) the dominant focus at the 1mm aperture is positioned between the hyperopic power and the intermediate power (18.32D and 20D respectively), (2) the portion of energy directed towards myopia (at approximately 21.7D) is higher at 3mm than for any of the other apertures shown, the intermediate energy is (3) weaker at the 2mm aperture than both hyperopia and myopia, and (4) at 4.5mm, the myopic intensity is weaker than hyperopia and intermediate. For all apertures of 2mm and above, it is the strongest type of vision.

[0106] To create an adaptive diffractive lens according to the present invention, it is necessary to use the diffraction efficiency that changes as a function of the aperture. Figures 10c, 10d, and 10e show examples of the underlying linear grating diffraction unit cells and their individual diffraction efficiencies. The efficiency is calculated in a standard way from the linear grating profile data. This diffraction efficiency calculation can of course be performed for any unit cell of any shape. In this particular lens, using the convention employed, the -1 order corresponds to the light arranged for myopia, the 0 order corresponds to the light arranged for intermediate vision, and the +1 order corresponds to the light arranged for hyperopia. The total diffraction efficiency given for each of these three figures is the sum of the diffraction efficiencies of the three desired diffraction orders. Figure 10c shows the diffraction efficiency of the profile shape used in the lens portion marked as G1 in Figure 10a. Myopia is promoted to be advantageous at other depths, while hyperopia and intermediate ones are maintained similarly. Figure 10d shows the diffraction efficiency of the profile shape used in the lens portion marked as G2 in Figure 10a. Hyperopia is here promoted to be advantageous at other depths, but in particular the light distributed to myopia is kept extremely low. Figure 10e shows the diffraction efficiency of the profile shape used in the lens portion marked as G3 in Figure 10a. The energy distributed to hyperopia and intermediate vision is maintained relatively similarly, but the additional myopic light is kept extremely low. For large apertures, especially those exceeding 4.5 mm, the benefit in intensity provided for myopia is extremely small or zero. The limitations of the grating and / or refractive shape used here result in undesirable effects. As will be further discussed below, for example, it is possible to construct an adaptive lens according to the present invention using a peripheral bifocal sawtooth grating or a peripheral portion with a refractive power corresponding to myopia. These are two examples of ways to reduce the additional intensity to myopia to almost zero. Of course, negative optical characteristics such as, for example, glare and halo effects can be imparted.

[0107] It is important to understand that these unit cells are specific examples. In the lens shown in FIG. 10a, there are several different unit cells. As a function of the aperture, it is often convenient to slowly advance the relative intensity distribution. It is possible to use unit cells with diffraction efficiencies and resulting energy distributions that are extremely different from those shown in this example.

[0108] FIG. 11a shows another lens diffraction profile according to the present invention and shows one additional way to vary the dominant power in the central portion of the lens. In FIG. 6a, a lens profile is shown in which the dominant power at a small aperture is adjusted by varying the curvature of the central zone. The placement of the dominant optical power at a small aperture, such as 1 mm, can also be adjusted very carefully by a horizontal shift of the central profile in the central portion (i.e., in a direction perpendicular to the optical axis). The lens profile of FIG. 11a is identical to the profile shown in FIG. 10a up to an aperture of about 2.4 mm, except for this horizontal shift. FIG. 11b shows the relative intensity peaks simulated for four different apertures. It is meaningful to compare this model data with the data of FIG. 10b. Due to this relatively small change in the profile of FIG. 11a, the dominant peak at 1 mm has shifted to approximately 0.8 D, which is closer to the power intended for distance vision. This configuration provides a slightly lower overall efficiency when calculated over the entire visual acuity range, but provides stronger distance vision. Further, for extremely small apertures, it provides a dominant power close to that of the intended hyperopic power, which is advantageous for some circumstances, for example, some methods of measuring the power of the eye postoperatively.

[0109] One additional change between the lens profiles of FIGS. 10a and 11a is that the latter exhibits a higher diffractive lens profile outside an aperture of approximately 2.4 mm. This lens profile is here targeted at being stronger for very large apertures and increasing the intensity for distant vision. One possible design choice is to use a bifocal sawtooth grating for apertures larger than, for example, 4.5 mm, even if a stronger reduction of myopic light is desired for large apertures. Such bifocal sawtooth gratings can be arranged to provide additional light for distant and intermediate vision. Yet another option is to use a single-focus sawtooth structure for large apertures. Such structures would need to be much higher than multifocal gratings.

[0110] It should be noted that the central part and the diffractive grating can be separated up to near the peak closest to the lens center, and a small horizontal shift of the central part does not need to be joined by an equal shift of the diffractive grating. Similarly, a shift of the diffractive grating does not need to be joined by an equal shift of the central zone. On the contrary, it is often convenient to shift the central part and the diffractive grating relative to each other. Specifically, it is often convenient to perform the shift such that the ridge closest to the lens center is thinner than that typically predicted by the formula of a well-formed lens. It can often be said that different ways of expressing this are that it is convenient to bring the central zone and the first valley of the diffractive grating closer to each other than predicted from the standard formula of a Fresnel zone plate. Such a configuration can increase the overall light efficiency and is a feasible way to construct the lens according to the present invention.

[0111] Figure 12a shows yet another lens profile for the adaptive multifocal lens according to the present invention. It is important to understand that the refractive baseline shown here is low and is the same throughout the optics. One important feature of this lens profile is that it includes a purely refractive portion arranged to provide light for distance vision only. In this example, this refractive portion covers substantially all of the aperture outside a 5 mm aperture. Such a refractive portion should not be considered when calculating the height between the peaks of the diffraction profile. Having a refractive portion around the multifocal lens can make a good way to form a strong adaptive lens. In this case, all light will be directed towards distance vision for apertures larger than 5 mm. This will increase the risk of the halo effect.

[0112] A second important feature of the diffraction lens profile of Figure 12a is that it is purely a single focus center. In this example, the central zone is formed to have a negative power that is 0.125 D lower than the nominal absolute difference between the powers responsible for the distance power and the intermediate power. The transition point between the central zone and the symmetric multifocal diffraction grating is marked by a vertical dashed line at an aperture of 1.14 mm. The symmetric diffraction grating is constructed in a manner relatively similar to that shown in Figure 10a. The diffraction grating targets near vision up to an aperture of about 2.8 mm and, with increasing aperture, is gradually adjusted more strongly for distance vision and to some extent for intermediate vision.

[0113] Figure 12b shows the relative intensity peaks simulated for four different apertures. The symmetric diffraction grating is configured to provide a nominal order separation of 1.675D. As shown in the simulation data, for the small 1mm aperture, the dominant peak is 1.4D below the intended intermediate peak. Summarizing the data in Figure 12b, here: (1) the dominant focus in the 1mm aperture is positioned between the intended hyperopic power and the intermediate power (18.32D and 20D respectively), (2) the myopic intensity is stronger at 3mm than for any of the other apertures shown, relative to that of the hyperopic intensity, (3) the intermediate intensity is weaker at the 2mm aperture than both hyperopic and myopic, and (4) at 4.5mm, the myopic intensity is weaker than hyperopic and intermediate. For all apertures of 2mm and above, hyperopia is the strongest type of vision. The unwanted peak near 17D is larger than, for example, the peak shown in Figure 10b, which is due to the choice of the central zone.

[0114] Figure 13a is a diagram of a possible target energy distribution for a lens design according to the patent. This ideal distribution for an adaptive diffractive multifocal lens is based on the discussion of the function of the human eye earlier in this document. The figure shows the desired energy distribution for an aperture up to 6 mm for each of near vision, intermediate vision, and far vision. Values within plus or minus 5 percent can be assumed to be within the ideal region. Often, lenses fabricated in accordance with the present invention may not fall within the ideal region for all types of vision or for all apertures. Further, it should be noted that this shows an ideal result considering only the energy distribution. In particular, the very dramatic exchange of intermediate and near energy from a bright pupil to a dark pupil is difficult to fully achieve. When designing a lens according to the present invention, it is often necessary to consider whether the main prioritization for the peripheral portion of that particular design should be the correct energy distribution or the minimization of aberrations and unwanted optical phenomena. A very efficient way to vary the energy distribution for a large aperture involves a dual-focus sawtooth grating and a purely single-focus zone. For example, the dual-focus sawtooth grating can be configured to provide only far and intermediate vision light for a large aperture. The peripheral single-focus zone as shown in Figure 12a can be configured to provide only light for far vision. However, both of these structures can increase the risk of unwanted optical phenomena, particularly the halo effect.

[0115] Figure 13b shows the simulated energy distribution between far vision, intermediate vision, and near vision for the hybrid lens of Figure 10a as a function of the aperture. The aperture is here considered as simply doubling the lens radius. In this simulation, far vision is dominant at all apertures, and for a 2 mm aperture, the energy for near vision and intermediate vision is relatively similar. The near vision energy has the largest plateau for apertures from 2.5 mm to 3 mm, while the intermediate energy has the smallest plateau for approximately the same apertures. For apertures larger than 3.1 mm, the near vision energy decreases with increasing aperture, while the intermediate energy increases with increasing aperture. The crossover point is estimated to be near an aperture of 4.5 mm. The data in the graph is constructed by first calculating the spectrum with 8 apertures per diffraction grating period and then calculating all with a total of 105 different apertures. At each aperture, the intensity of each vision is approximated by a local maximum peak at the position of the individual type of vision. And then, using each point in the graph data for the entire period, the graph is plotted using the sliding average value for each vision type. For example, if the calculation were performed only at the valleys or peaks, the line would be less wavy.

[0116] Other variations to the disclosed examples and embodiments can be understood and effected by those skilled in the art in practicing the present invention from a study of the drawings, disclosure, and appended claims. In the claims, the term "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 measured values are recited in mutually different dependent claims does not indicate that a combination of these measured values cannot be advantageously used. Reference signs in the claims should not be construed as limiting their scope. The same reference signs refer to equal or equivalent elements or acts.

[0117] According to the present invention disclosed, an ophthalmic multifocal lens configured to provide distance vision, intermediate vision and near vision is proposed, said lens having a light transmissive body with an optical axis, and a refractive baseline extending across a part of said lens body, said lens further having a first part that coincides with the central region of said light transmissive lens body and extends concentrically in the radial direction, and a multifocal second part that extends concentrically in the radial direction.

[0118] According to one embodiment of the present invention disclosed, the second part of the ophthalmic multifocal lens further includes a symmetric multifocal diffraction grating superimposed on said refractive baseline and covering a part of the lens, the shape and the resulting light intensity distribution of which vary with respect to the distance to the optical axis.

[0119] According to one embodiment of the present invention disclosed, said first part of said ophthalmic lens is configured such that a substantially concave shape is superimposed on said refractive baseline around the optical axis and is connected to the ridge of said symmetric multifocal diffraction grating closest to the optical axis.

[0120] According to one embodiment of the present invention disclosed, said refractive baseline provides a focus that substantially coincides with the intermediate power.

[0121] According to one embodiment of the present invention disclosed, said first part of said ophthalmic lens is configured to provide a dominant optical power that is between the intended powers of distance vision and intermediate vision, and the single focal central zone has a curvature configured to add a negative power to the refractive baseline of the lens.

[0122] According to one embodiment of the disclosed invention, the disclosed embodiment provides a transition zone between the central part and the diffraction grating located near the peak of the first peak of the diffraction grating.

[0123] According to an embodiment of the present invention disclosed, the ophthalmic multifocal lens has a ratio of the energy intended for myopia to the energy intended for hyperopia, and the ratio is configured to be lower at an aperture of 3 mm compared to the same ratio at apertures of 2 mm and 4.5 mm.

[0124] According to an embodiment of the present invention disclosed, the ophthalmic multifocal lens is configured such that the energy intended for myopia for an aperture of 5 mm is weaker than the energy intended for intermediate vision and hyperopia, and the ophthalmic multifocal lens is configured such that the intermediate energy for an aperture of 3 mm is weaker than both the myopic and hyperopic energies.

[0125] According to an embodiment of the present invention disclosed, the ophthalmic multifocal lens is configured such that the modulation transfer function ratio between hyperopia and myopia is lower at an aperture of 3 mm than that at apertures of 2 mm and 4.5 mm when measured at 50 lines per millimeter.

[0126] According to an embodiment of the present invention disclosed, the symmetric multifocal diffraction grating further includes a waveform diffraction pattern including alternately arranged peak and valley amplitude values, and when measured along a direction perpendicular to the optical axis, the first portion is concave from a point coinciding with the optical axis of the lens to a point configured to be closer to the peak amplitude value than the valley amplitude.

[0127] According to an embodiment of the present invention disclosed, the power difference between intermediate vision and hyperopia is configured to be between 1.5 D and 2.2 D, while the power difference between hyperopia and myopia is configured to be between 3 D and 4.4 D.

[0128] According to an embodiment of the present invention disclosed, the first portion includes a shape configured for single focus.

[0129] According to an embodiment of the disclosed invention, the symmetric multifocal diffractive grating provides a plurality of foci selected from a group including three, five, seven, nine (not limited thereto) foci.

[0130] According to an embodiment of the disclosed invention, at least one of the first part, the second part, or both of the parts is combined with a sawtooth diffractive grating that is substantially single - focal for the design wavelength.

[0131] According to an embodiment of the disclosed invention, for apertures larger than 3.5 mm, the lens comprises at least one optically active mechanism from a group including an asymmetric diffractive grating, a shape providing refractive power other than the refractive baseline, a symmetric diffractive grating having an odd number of foci different from the symmetric multifocal diffractive grating (not limited thereto).

[0132] According to an embodiment of the disclosed invention, within a 4.5 mm aperture, the symmetric multifocal diffractive grating includes at least two periods of the symmetric multifocal grating, and for the at least two periods, the diffraction efficiency of the order responsible for near vision for the corresponding linear grating unit cell has a relationship such that it is at least 10 percent higher than that of the two periods closest to the optical axis compared to the periods located further away from the optical axis.

[0133] According to an embodiment of the disclosed invention, the highest point of the peak closest to the optical axis of the multifocal grating is arranged at a vertical distance within the range from 0.45 mm to 0.73 mm from the optical axis.

[0134] According to an embodiment of the disclosed invention, the point of the first part that coincides with the optical axis of the multifocal lens is configured to be lower compared to the refractive baseline than other valleys within 3 mm of the center of the multifocal lens.

[0135] According to one embodiment of the disclosed invention, the maximum peak-to-valley height of the symmetric multifocal diffraction grating is less than 50 percent of full phase modulation, calculated such that the valleys of the first portion are omitted at the design wavelength.

[0136] According to one embodiment of the disclosed invention, the lens has a dominant power between the depicted far vision power and the intermediate power when measured with a concentric 1 mm aperture.

[0137] According to one embodiment of the disclosed invention, the lens has a dominant power that is at most 1.2 D stronger than the power intended for far vision when measured with a concentric 1 mm aperture.

[0138] According to at least one embodiment of the disclosed invention, an ophthalmic multifocal lens is proposed that includes at least three foci and provides light for near vision, intermediate vision, and far vision.

[0139] According to at least one embodiment of the disclosed invention, the multifocality of the lens is provided by a multifocal symmetric grating superimposed on a refractive baseline.

[0140] According to at least one embodiment of the disclosed invention, the multifocal symmetric grating covers a continuous portion of the lens, which can cover the entire optical portion or a portion smaller than that.

[0141] According to at least one embodiment of the disclosed invention, the multifocal symmetric grating differs in terms of shape and intensity distribution as a function of the distance to the optical axis.

[0142] According to at least one embodiment of the disclosed invention, the lens has a central zone that provides a dominant peak of power that is less than 1.2 D stronger than the intended far vision power of the lens.

[0143] According to at least one embodiment of the present invention disclosed, the central zone has a concave shape with a small baseline curvature and is connected to a multifocal diffraction grating at a transition point.

[0144] According to at least one embodiment of the present invention disclosed, the ratio of the hyperopic energy to the myopic energy is lower for an aperture of 3 mm than for apertures of 2 mm and 4.5 mm.

[0145] According to at least one embodiment of the present invention disclosed, for an aperture of 3 mm, the intermediate energy is weaker than both the hyperopic and myopic powers.

[0146] According to at least one embodiment of the present invention disclosed, when measured at 50 lines and 100 lines per millimeter for apertures from 1.5 mm to 6 mm, the modulation transfer function (MTF) of the hyperopic power is at least 35% higher than that of the myopic power and at least 20% higher than that of the intermediate vision power.

[0147] According to at least one embodiment of the present invention disclosed, the MTF ratio of the hyperopic power to the myopic power is lower for an aperture of 3 mm than for apertures of 2 mm and 4.5 mm.

[0148] According to at least one embodiment of the present invention disclosed, the diffraction grating includes a wavy diffraction pattern having alternately arranged peak and valley amplitude values, and the transition point is located closer to the peak amplitude value of the diffraction grating than to the valley amplitude value.

[0149] According to at least one embodiment of the present invention disclosed, for the intermediate vision, the additive power value is 1.5 D to 2.2 D, and at the myopic focus, it is 3 D to 4.4 D.

[0150] According to at least one embodiment of the present invention disclosed, the valleys of each period of the multifocal symmetric diffraction grating are aligned with the refractive baseline.

[0151] According to at least one embodiment of the disclosed invention, the central zone includes a single focus zone.

[0152] According to at least one embodiment of the disclosed invention, the multifocal lens is a trifocal lens, and thus the multifocal symmetric grating provides three foci.

[0153] According to at least one embodiment of the disclosed invention, the multifocal symmetric grating provides a plurality of foci selected from a group including 4, 5, 7, 9 (not limited thereto) foci.

[0154] According to at least one embodiment of the disclosed invention, the multifocal symmetric grating includes at least two diffractive cells having significantly different shapes from each other.

[0155] According to at least one embodiment of the disclosed invention, the multifocal symmetric grating includes at least a first part and a second part, and the diffraction efficiency of the order responsible for near vision is at least 30% higher in the first part than in the second part.

[0156] According to at least one embodiment of the disclosed invention, the central zone has a diameter between 0.9 mm and 1.4 mm.

[0157] According to at least one embodiment of the disclosed invention, the maximum peak-to-peak height of the multifocal symmetric grating is less than 80% of the full phase modulation, preferably less than 50% of the full phase modulation.

[0158] According to at least one embodiment of the disclosed invention, the diffraction grating outside the central zone is arranged closer to the central zone than a diffraction lens following the interval of a well-formed Fresnel lens.

Claims

1. An ophthalmic multifocal lens configured to provide distance vision, intermediate vision, and near vision, The lens has a light-transmissive lens body with an optical axis and a refractive baseline extending across a portion of the lens body, The lens further has a first portion that coincides with the central region of the light-transmissive lens body and extends concentrically in the radial direction, and a second portion that is multifocal and extends concentrically in the radial direction, The second portion of the ophthalmic multifocal lens further includes a symmetric multifocal diffraction grating that is superimposed on the refractive baseline and covers a portion of the lens, and whose shape and resulting light intensity distribution vary with respect to the distance from the optical axis. The symmetric multifocal diffraction grating includes one diffraction order contributing to distance vision and one diffraction order contributing to near vision, The zero order of the symmetric multifocal diffraction grating superimposed on the refractive baseline substantially coincides with the power of the refractive baseline and the intended intermediate power of the lens, The first portion of the ophthalmic lens is configured such that a substantially concave shape is superimposed on the refractive baseline around the optical axis and is connected to the ridge of the symmetric multifocal diffraction grating closest to the optical axis, The refractive baseline provides a focal point that substantially coincides with the intermediate power, The first portion of the ophthalmic lens is configured to provide a dominant optical power between the intended distance vision power and the intermediate vision power, The ophthalmic multifocal lens, At an aperture of 5 millimeters, the energy intended for near vision is weaker than the energy intended for both intermediate vision and distance vision respectively, At an aperture of 3 millimeters, the intermediate energy is configured to be weaker than both the near vision energy and the distance vision energy. An ophthalmic multifocal lens characterized by this.

2. The ophthalmic multifocal lens has a ratio of the energy intended for myopia to the energy intended for hyperopia, and the ratio is configured to be lower at an aperture of 3 mm compared to the same ratio at apertures of 2 mm and 4.5 mm, and is an ophthalmic multifocal lens configured to provide hyperopia, intermediate vision, and myopia as recited in claim 1.

3. The ophthalmic multifocal lens is configured such that, when measured at 50 lines per millimeter, the modulation transfer function ratio between hyperopia and myopia is lower at a 3 mm aperture than that at 2 mm and 4.5 mm apertures, and is an ophthalmic multifocal lens configured to provide hyperopia, intermediate vision, and myopia as recited in claim 1 or 2.

4. The symmetric multifocal diffraction grating further includes a waveform diffraction pattern including alternately arranged peak and valley amplitude values. When measured along a direction perpendicular to the optical axis, the first portion is concave from a point coinciding with the optical axis of the lens to a point configured to be closer by the peak amplitude value than the valley amplitude, and is an ophthalmic multifocal lens configured to provide hyperopia, intermediate vision, and myopia as recited in any one of claims 1 to 3.

5. The power difference between intermediate vision and hyperopia is configured to be between 1.5 diopters and 2.2 diopters, while the power difference between hyperopia and myopia is configured to be between 3 diopters and 4.4 diopters, and is an ophthalmic multifocal lens configured to provide hyperopia, intermediate vision, and myopia as recited in any one of claims 1 to 4.

6. The first portion includes a shape configured for single focus, and is an ophthalmic multifocal lens configured to provide hyperopia, intermediate vision, and myopia as recited in any one of claims 1 to 5.

7. The symmetric multifocal diffractive grating provides a plurality of foci selected from the group consisting of 3, 5, 7, and 9 foci, and is configured to provide myopic vision, intermediate vision, and near vision according to any one of claims 1 to 6. Ophthalmic multifocal lens.

8. At least one of the first part, the second part, or both of the parts is combined with a sawtooth diffractive grating that is substantially single-focus for the design wavelength, and is characterized by any one of claims 1 to 7. Ophthalmic multifocal lens configured to provide myopic vision, intermediate vision, and near vision.

9. For apertures larger than 3.5 mm, the lens includes at least one optically active mechanism from the group including an asymmetric diffractive grating, a shape that provides refractive power other than the refractive baseline, and a symmetric diffractive grating with an odd number of foci different from the symmetric multifocal diffractive grating. An ophthalmic multifocal lens configured to provide myopic vision, intermediate vision, and near vision according to any one of claims 1 to 8.

10. Within the 4.5 mm aperture, the symmetric multifocal diffractive grating includes at least two periods of the symmetric multifocal grating, and for the at least two periods, the diffraction efficiency of the order responsible for near vision is closer to the optical axis than the periods located further from the optical axis. It has a relationship that is at least 10% higher than that of the two periods closest to the optical axis, and is characterized by any one of claims 1 to 9. Ophthalmic multifocal lens configured to provide myopic vision, intermediate vision, and near vision.

11. The highest point of the peak closest to the optical axis of the multifocal grating with respect to the refractive baseline is arranged at a vertical distance within the range from 0.47 mm to 0.75 mm from the optical axis, and is characterized by any one of claims 1 to 10. Ophthalmic multifocal lens configured to provide myopic vision, intermediate vision, and near vision.

12. The point of the first portion that coincides with the optical axis of the multifocal lens is configured to be lower than the refractive baseline compared to other valleys within 3 mm of the center of the multifocal lens, an ophthalmic multifocal lens configured to provide myopic vision, intermediate vision, and near vision according to any one of claims 1 to 11.

13. The maximum peak-to-valley height of the symmetric multifocal diffraction grating is less than 50 percent of full phase modulation, calculated such that the valleys of the first portion are omitted at the design wavelength, an ophthalmic multifocal lens configured to provide myopic vision, intermediate vision, and near vision according to any one of claims 1 to 12.

14. The lens has a dominant power between the intended myopic power and the intermediate power when measured with a concentric 1 mm aperture, an ophthalmic multifocal lens configured to provide myopic vision, intermediate vision, and near vision according to any one of claims 1 to 13.

15. The lens has a dominant power that is at least 0.2 diopters and at most 1.2 diopters stronger than the intended power for myopic vision when measured with a concentric 1 mm aperture, an ophthalmic multifocal lens configured to provide myopic vision, intermediate vision, and near vision according to any one of claims 1 to 14.

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