Diffractive multifocal small aperture ophthalmic lens

Abstract

The transmissive ophthalmic lens comprises a first surface opposite the second surface. The first surface comprises a centrally located diffractive multifocal zone surrounded by a peripherally located refractive non-multifocal zone. The second surface is a refractive non-multifocal surface. The refractive non-multifocal zone forms a far focus. The diffractive multifocal zone is 2.5 millimeters or less in diameter to create a far focus and an add focus, and 1.5 mm or more in diameter for multi-peak performance. The first and second grooves of the diffractive multifocal zone may be only two grooves. At least 20% of light is directed within the diffractive multifocal zone to one of the far focus and the add focus. The diffractive multifocal zone may have a peripheral zone that is a two-sign aspheric surface near the far focus, and a base curve with aspheric grooves configured to minimize spherical aberration at the add focus.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This international patent application claims priority to U.S. Utility Application No. 18 / 191,816, filed March 28, 2023, which claims priority to U.S. Provisional Application No. 63 / 362,387, filed April 1, 2022, U.S. Provisional Application No. 63 / 371,501, filed August 15, 2022, and U.S. Provisional Application No. 63 / 376,086, filed September 17, 2022, the entire disclosures of which are incorporated herein by reference in their entirety.

[0002] The present invention relates generally to multifocal ophthalmic lenses that have a higher extended depth of focus (DOF) performance than monofocal lenses of the same shape and material, and more particularly to extended DOF diffractive multifocal small aperture intraocular lenses (phakic intraocular lenses, intraocular contact lenses, and aphakic intraocular lenses), corneal inlays, and contact lenses. [Background technology]

[0003] Ophthalmic lenses, as disclosed herein, refer to phakic or aphakic intraocular lenses (IOLs), including intraocular contact lenses (ICLs) that are inserted into the eye, corneal inlays (CIs) that are inserted into the cornea of ​​the eye, and contact lenses (CLs) that are worn on the front surface of the eye.

[0004] In describing the present invention, the following definitions are used. A monofocal lens is a lens with a fixed, single power. The lens provides good quality vision within a small range of viewing distances, usually significantly smaller than those required for near or intermediate to far vision. In this case, far vision is usually defined as a distance of about 6 feet (about 2 meters) or more from the eye. Near vision is closer to the eye, about 2 feet (about 50 centimeters). Intermediate vision is intermediate between far vision and near vision. Monofocal ophthalmic lenses usually exhibit a distance power or a distance focus, and are said to form a distant image of an object located at a distant distance. Monofocal lenses may have a cylinder power to correct for astigmatism of the eye, and are referred to herein as non-multifocal lenses. That is, monofocal lenses may include cylinder.

[0005] There has been a great deal of effort to develop lenses for the correction of presbyopia in the form of refractive or diffractive lenses in which the image-forming refractive, diffractive or combination thereof is located in the lens surface within the so-called effective aperture. Lenses of this type provide multiple powers, so-called bifocal or multifocal lenses. References to the terms bifocal and multifocal are used interchangeably in this application. Multifocal ophthalmic lenses can provide refractive powers, diffractive powers or a combination of both, and can provide additional powers in addition to the distance power, called add power (AP), additional foci in addition to the far focus, called add foci, and additional images in addition to the far image, called add images, formed by objects located at distances other than the far distance. Multifocal lenses may have a cylindrical power to correct astigmatism of the eye, and throughout this application references to multifocal lenses also include cylinder.

[0006] A multifocal ophthalmic lens has a multifocal surface for providing an add power and an opposing refractive surface, which is the refractive surface of the multifocal lens that is opposite the multifocal surface with light passing through both surfaces through the effective aperture of the lens.

[0007] A diffractive lens generally consists of a number of equal-area toric surface zones on the imageable surface, called the base curve, which are called diffractive grooves or simply grooves. In a simple paraxial form, the grooves, echelettes, or surface relief features are j 2 In other words, the focal length (f) of the m-th diffraction order (m=±1, ±2, etc.) for the design wavelength (λ) can be accurately approximated by the following formula:

number

number

[0008] If the step size is zero or randomly sized, or the groove areas are randomly sized, the lens becomes refractive, ie, the corresponding image position is governed by Snell's law.

number

[0009] The image forming area of ​​a lens with a given optical specification is called the effective aperture (CA). For monofocal ophthalmic lenses, there is one effective aperture to form the far focus, while for multifocal ophthalmic lenses, there may be several different effective apertures, one to form the far focus and one to form the CA. F and another one (CA A ) forms an add focus in addition to the far focus. Furthermore, the pupil of the eye defines the effective aperture (CA YThere are many publications on pupil diameter under different light conditions, for example the paper by HH Telec et al. on the effect of age and light on pupil diameter, published in Beyoglu Eye J 2018;3(2), 80-85;DOI:10.14744 / bej.2018.43534. YP = 3.0 mm, and in the elderly (over 60 years old), it is about 0.5 mm smaller, CA' YP This confirms the validity of the reference pupil for daytime (photopic) conditions, which is CA = 2.5 mm. The pupil of the eye dilates under low light conditions, called mesopic conditions. Optical tests that mimic pupil diameter under mesopic conditions have shown that CA = 2.5 mm. YM = 4.5mm diameter is used as a reference. Thus, there are two different states of the multifocal ophthalmic lens in the optical system of the eye: (1) CA under daytime (photopic) conditions A >CA YP and the corresponding multifocal lenses are called "full aperture lenses" or FALs. (2) CA under daylight conditions A <CA' YP and the corresponding multifocal lens is called a "small aperture lens" or SAL. Thus, SA A Multifocal lenses with a focal length of ≦2.5 mm are defined as small aperture lenses regardless of age. To accommodate mesopic conditions, full aperture lenses are CA A >CA YM =4.5mm is often indicated.

[0010] Thus, the specifications of a refractive multifocal lens are characterized by a focal distribution defined by Snell's law. The specifications of a diffractive multifocal lens are characterized by a focal distribution defined by the base curve curvature of the zeroth diffraction order and the phase coefficients of the non-zeroth diffraction orders. There are different types of refractive-diffractive multifocal designs. A refractive-diffractive multifocal lens may be a zonal design. In a zonal design, a zone of refractive properties and a zone of diffractive properties are arranged. An example is given in U.S. Patent No. 7,073,396 to Portney, the disclosure of which is incorporated herein by reference in its entirety. Another option for a refractive-diffractive design is to include a base curve with multifocal properties as the refractive multifocal properties defined by Snell's law (this is why the zeroth diffraction focus or power is often referred to as the refractive focus or power of a diffractive lens). The non-zero diffraction orders provide additional multifocal specifications. An example is given in U.S. Patent No. 8,610,362 to Portney. Another option for refractive-diffractive multifocal lenses was introduced in U.S. Patent No. 6,536,899 to Fiala, the disclosure of which is incorporated herein by reference in its entirety, in which each diffractive step between the diffractive grooves is changed to a refractive subzone of power matching one of the diffractive powers, leaving the remainder of the original diffractive grooves to maintain the diffractive specifications.

[0011] The complementary term to the term Addition (AP) used is Depth of Focus (DOF). DOF refers to the range of acceptable image quality set by certain clinically meaningful image qualities. For example, clinically, DOF is typically defined by the visual range in diopters that does not fall below visual acuity (VA) 20 / 40 according to the Snellen chart. In in vitro clinical testing, DOF is typically defined as the image range in diopters or focal shift in millimeters that exhibits a Modulation Transfer Function (MTF) of at least 0.1 for a selected spatial frequency in line pairs per millimeter (lp / mm), and the corresponding test characteristic is called the Through Focus Response (TFR) for a given spatial frequency. TFR testing is typically performed in an Eye Model, and a spatial frequency of 50 lp / mm is used to represent 20 / 40 visual acuity clinically. On the other hand, the add power (AP) can be defined for a multifocal ophthalmic lens with distinct foci, such as bifocal or trifocal, that exhibits multi-peak performance on the TFR. AP is a measure of the distance in diopters from the peak image at the add focus to the far focus. When a multifocal ophthalmic lens exhibits a continuous focus range with so-called single-peak performance on the TFR without a distinct image peak, DOF and AP are used interchangeably, since they represent the same magnitude of the visual range within the single-peak performance. And DOF is a more general term than AP, and single-focus lenses also exhibit DOF>0 (clinically about 0.5D) even when there is no add power and AP=0. Both the terms AP and DOF are used interchangeably in this application, unless there is a need to use them specifically as specific measures of the image-forming properties of an ophthalmic lens.

[0012] For the correction of presbyopia, the first attention was paid to the development of refractive and diffractive ophthalmic lenses of the FAL type, providing effective add powers, initially at near focus only, so-called bifocal, and later at near and intermediate focus, so-called trifocal. Although such multifocal ophthalmic lenses, especially in the form of IOLs, have achieved good image effects, the drawback is that some patients experience undesirable visual effects called dysphotopsia, e.g. glare artifacts of light such as arcs, stripes, stars, and rings, collectively named halos. Dysphotopsia is specific to distance vision phenomena observed in low light conditions, especially when viewing bright objects against a dark background (such as street lamps or car lights) or as shadow areas in high contrast transitions when viewing objects (such as the ridges of buildings against a light background, the ridges of tree trunks and branches). Although the majority of patients can tolerate the halos they experience with IOLs and less severe halos with CLs, many discontinue the use of multifocal CLs, especially at higher add powers, or request lens exchange in the case of multifocal IOLs.

[0013] More recently, the focus of multifocal ophthalmic IOL development for presbyopia correction has shifted to the problem of halos, with many innovations emerging in recent years. The efforts have also been combined with the reduction of the visual range from far to intermediate, resulting in a new class of IOLs that represents an improvement over monofocal IOLs. The corresponding IOLs are called Extended Depth of Focus, or EDOF IOLs for short. For convenience, the term EDOF lenses is expanded in this patent application to include contact lenses and inlays with the same problem of halo mitigation, and to any visual range.

[0014] The development of EDOF ophthalmic lenses has been the subject of many innovations, and these considerations are necessary to recognize the originality of the present discovery. The requirements for EDOF ophthalmic lenses to replace monofocal ophthalmic lenses can be summarized into three points: (1) substantially suppressing halo to the same extent as monofocal lenses, (2) effectively extending the DOF by at least 1D over monofocal lenses, i.e., DOF≧1.5D, and (3) providing comparable monofocal image quality for distance vision under different lighting conditions. These serve as a basis for analyzing the prior art and the present invention, since fulfilling all three challenges can make an effective successor to monofocal ophthalmic lenses.

[0015] One approach to suppressing halos is described in U.S. Patent No. 10,656,437 to Limon et al., the disclosure of which is incorporated herein by reference in its entirety, which has a diffractive (phase) pattern that extends the DOF at near and far, respectively, reducing the size of the halo by 25%. The principle used was similar to that in U.S. Patent No. 6,557,998 to Portney, the disclosure of which is incorporated herein by reference in its entirety, for a refractive multifocal lens to extend the DOF at near and far, respectively. This design approach to establish image continuity between near and far has shown only a very modest effect on suppressing halos.

[0016] Another approach was to reduce the add power to a narrower range from distance to intermediate while still maintaining the FAL diffractive properties. This has been applied commercially in the Tecnis Symfony IOL (Johnson & Johnson) and the AT LARA 829MP (Zeiss). This approach did not solve the halo problem.

[0017] More recently, attention has shifted to ophthalmic lenses with SAL properties of multifocal refractive designs. A corresponding refractive multifocal design with increased power in the central zone is described in U.S. Patent No. 11,506,914 to Canovas et al., the disclosure of which is incorporated herein by reference in its entirety (the highest power was closer to the center of the lens). Extended DFO refractive IOLs with a central zone of variable curvature are described in U.S. Patent Application No. 2022 / 0287825 to Ribiero et al. and U.S. Patent Application No. 2022 / 0287826 to Tiwari, the disclosures of both of which are incorporated herein by reference in their entirety. EDOF IOL lenses based on a corresponding approach have been marketed: Acrysof IQ Vivity IOL (Alcon), Tecnis Eyhance IOL (Johnson & Johnson), and LuxSmart Crystal (Bausch + Lomb). The design approach involves a refractive multifocal geometry with enhanced power in a small central lens region less than 2.5 mm in diameter. Although this approach has largely resolved issues with halos and distance image quality under different light conditions, it has only provided limited results in terms of DOF, improving by only about 0.5D over monofocal lenses, as clinically demonstrated by commercially available EDOF IOLs. Thus, approaches using refractive multifocal SALs have lacked the effective extension of DOF beyond monofocal lenses.

[0018] The pinhole principle (small aperture effect) was also proposed as a principle for EDOF lens design. That is, a small diameter is created by a mask to expand the DOF. This is described in U.S. Patent No. 10,449,039 by Cristie et al. and U.S. Patent Application No. 2020 / 0192121 by Anderson, the entire disclosures of which are incorporated herein by reference. Here, a colored ring was provided on the corneal inlay or contact lens to create the small aperture effect of the extended DOF. A commercially available EDOF IOL based on the pinhole effect was developed as the AcuFocus IC-8 IOL (Bausch + Lomb). Although this approach was able to address halos, the expansion of DOF over a comparable monofocal lens was nevertheless limited to about 0.5D. Furthermore, the presence of an opaque mask limited image quality, as light accommodation was lost with the dilation of the eye's pupil in low light conditions. Several studies have shown that visual acuity is improved in photopic, i.e., daytime, conditions (approximately 100 cd / m 2 ) to mesopic, or twilight conditions (approximately 1 cd / m 2 ), which represents a safety issue for the use of light-blocking masks under mesopic conditions. Due to this limitation, the AcuFocus IC-8 IIOL was only prescribed for implantation in one eye, allowing the other eye to compensate for the lens' limitations on image quality under reduced light (mesopic) conditions. This results in the potential loss of binocular vision. Binocular vision is an important factor in vision improvement, as it has the potential to improve visual acuity by a factor of √2 over monocular acuity.

[0019] Thus, the pinhole-only approach has shown limited DOF extension beyond monofocal lenses. U.S. Patent No. 10,517,716 to Luque, the disclosure of which is incorporated herein by reference in its entirety, describes an intraocular lens with an opaque mask disposed on its surface. The opaque mask has small zones with multifocal refractive or diffractive shapes to extend the DOF beyond that produced by the small aperture effect. Luque describes diffractive design options for such small zones in the opaque mask, but does not provide any details on designing or exposing grooves in the central mask aperture. In fact, Luque describes a preference for a refractive design, since the primary advantage of diffractive surfaces over refractive lenses, pupil independency, does not apply to small aperture lenses produced by mask application, and light directed to high diffraction orders can cause halos. It will be shown in this application of the present invention that refractive multifocal designs have very limited advantages for extending DOF in small aperture lenses, resulting in poorer image quality compared to the present invention. Furthermore, the presence of a mask in a refractive or diffractive multifocal design will limit image quality in low light conditions and will likely only be suitable for monocular use, similar to the experience with the AcuFocus IC-8 IOL. The present invention will demonstrate that extended DOF can be achieved without a mask, and that exceptional distance image quality can be achieved without sacrificing the need to suppress halos.

[0020] In summary, none of the cited prior art and corresponding clinical products for addressing halos achieve other objectives necessary to replace monofocal ophthalmic lenses, such as extending DOF more than monofocal lenses, achieving distance image quality comparable to monofocal lenses under different light conditions, etc. The present invention provides a lens design and method that resolves the conflict between the above objectives (halo suppression, DOF extension, and high distance image quality) as demonstrated in commercial products and prior art. Ophthalmic lenses of the described design can be applied to any ophthalmic lens application involving presbyopia correction as a successful successor to monofocal ophthalmic lenses to further expand the patient's benefit in meeting their visual needs. Summary of the Invention [Means for solving the problem]

[0021] The ophthalmic lens according to the invention comprises an anterior surface and a posterior surface. The lens has a central diffractive multifocal zone with a diameter of 2.5 mm or less. This defines the lens as a diffractive multifocal (DM) small aperture lens (SAL). This limitation on the size of the multifocal zone was determined to mitigate the halo produced by multifocal ophthalmic lenses. Up until now, diffractive lenses have been used for full aperture lenses, i.e. diffractive multifocal zones with a diameter of at least 4 mm, due to the main advantage of diffractive multifocals, which is that they can split the light in a constant ratio regardless of the pupil of the eye. This means that if the light is split, for example 50 / 50, between the far focus and the add focus, the same light split will be maintained for a 2.5 mm pupil and a 5 mm pupil, ensuring image quality at each focus even with different pupil sizes. No person skilled in the art had previously witnessed or anticipated the advantages of diffractive multifocal lenses for small aperture applications. And it is an unexpected result of the present invention that a lens having a diffractive multifocal zone of 2.5 mm diameter or less is superior to a refractive multifocal small aperture lens of 2.5 mm diameter or less due to its ability to achieve multi-peak performance for excellent image quality and extended DOF at far focus with similar suppression of halo. Moreover, it was equally desirable to have a diffractive multifocal zone of 1.5 mm diameter or more to ensure the multi-peak performance of the diffractive multifocal small aperture lens according to the present invention. That is, the invention described herein was not obvious to the present inventors or to other skilled persons that an ophthalmic lens having a diffractive multifocal zone within a diameter of 1.5 mm to 2.5 mm provides better performance than a refractive multifocal small aperture in terms of extended depth of focus and better image quality at far focus and add focus as a result of multi-peak performance compared to the single-peak performance produced by a refractive multifocal small aperture lens. Indeed, the prior art (e.g., U.S. Patent No. 10,517,716 to Lugue) did not consider the use of diffractive multifocal lenses for small aperture applications.

[0022] The central zone represents the add power of the diffractive multifocal design and contains two circular diffractive grooves that run around the circumference. The central diffractive multifocal zone generates the add focus of higher diffraction orders and the far focus of zero diffraction order generated by the virtual base curve of the diffractive multifocal ophthalmic lens, where at least 20% of the light is directed to each focus. Only such diffractive foci form an image and are referred to as diffractive foci in the present invention. The peripheral zone outside the central diffractive multifocal zone is a transparent refractive non-multifocal surface for generating the far focus. It is adjacent to the central diffractive multifocal zone. The base curve or the opposite surface of the central diffractive multifocal zone is a non-multifocal surface that can be spherical, aspheric or toric. The corresponding diffractive multifocal small aperture ophthalmic lens is abbreviated as DM SAL.

[0023] In a preferred embodiment of the invention, the base curve of the central diffractive zone continues into the refractive peripheral zone, which together form a surface shape to produce a far focus at different aperture sizes up to about 8 mm diameter. Such surface shapes can be spherical or aspheric, including two-sign aspheric, as described in U.S. Patent No. 8,894,706 to Portney, the entire contents of which are incorporated herein by reference.

[0024] In another embodiment of the invention, the radius of the central diffractive multifocal zone coincides with the outer radius of the second (peripheral) circular groove of the central diffractive multifocal zone.

[0025] In yet another embodiment of the present invention, the sag at the inner diameter of the peripheral refractive zone matches the sag of the diffractive multifocal zone at their junction, so that there is no surface step at the transition between the central diffractive multifocal zone and the peripheral refractive zone.

[0026] In another embodiment of the present invention, the diffractive multifocal small aperture lens provides a smaller magnitude of add power and a larger magnitude of add power. Such lenses are called diffractive trifocal small aperture lenses. The periodicity of the diffractive trifocal surface is a superposition of a periodicity of larger grooves and a periodicity of smaller grooves, which are synchronized such that two smaller grooves coincide with one larger groove. The periodicity of the larger grooves is for realizing the smaller add power, and the central diffractive multifocal small aperture zone is sized to include two such grooves. The periodicity of the smaller grooves is for realizing the larger add power, and the central diffractive multifocal small aperture zone includes four such grooves.

[0027] In a preferred embodiment of the present invention, the diffractive multifocal small aperture lens has an add power between 1.0D and 2.5D at the spectacle plane, providing a continuous image quality range from distance power to add power, where the image quality is close to or above the minimum clinically relevant image quality for in vitro testing with a modulation transfer function (MTF) for a spatial frequency of 50 lp / mm, equivalent to a visual acuity of 20 / 40 on the Snellen chart. The minimum clinically relevant image quality is set to MTF(50 lp / mm)=0.1.

[0028] The present invention further includes a diffractive multifocal surface structure that converts an optical step between adjacent grooves into a plurality of sub-steps with a refractive portion between adjacent sub-steps that are shaped to refract light to one of the diffractive foci of the diffractive multifocal zone. The alternating sub-steps and refractive portion structure reduces the optical step to small sub-steps, thereby minimizing light scattering at the transition between grooves and creating a smooth optical transition between grooves to avoid damage to adjacent ocular tissues by the diffractive surface, e.g., the cornea by the diffractive posterior surface of a diffractive contact lens, the stroma by a diffractive corneal inlay, and the crystalline lens by the diffractive posterior surface of an intraocular contact lens (ICL). The conversion of the optical steps into a set of substeps and refractive sections does not depend on the groove shape, base curve, or groove periodicity of the diffractive surface, but only on the step height and the selected minimum size of the substeps that minimizes light scattering and smooths the diffractive surface.

[0029] The present invention further describes a method for guiding the design of a multifocal small aperture ophthalmic lens (applicable to any multifocal lens) to exhibit single or multi-peak performance on the Through Focus Response (TFR) at a selected clinically relevant image quality. The visual acuity of the 20 / 40 row of the Snellen chart is the most common clinically relevant image quality in clinical testing, and corresponds to a clinically relevant image quality with MTF=0.1 for 50 lp / mm in in vitro lens testing on a reference eye model. The method guides the multifocal lens configuration in the selection of the multifocal zone diameter, the add power size, and the optical design of the multifocal ophthalmic lens to provide a suitable multi-peak performance characterized by the add power as the separation between the image peaks. The small aperture lens (SAL) design with multi-peak performance allows for enhanced image quality at the distinct optical powers located at the far and add foci, and provides a continuous DOF ​​by extending the DOF at the expense of degrading the image quality between the image peaks without compromising the clinically relevant image quality. Clinically meaningful image quality in the design method is defined as MTF(50lp / mm)=0.1. The method demonstrates the limitations of designs with single-peak performance typically exhibited by refractive small aperture lenses with respect to reduced DOF range and reduced distance image quality. The preferred SAL design according to the present invention exhibits multi-peak performance with 1.75±0.5D add providing minimum image quality between image peaks under photopic conditions close to clinically meaningful image quality MTF(50lp / mm)=0.1 (within 10%) and achieves continuous DOF.

[0030] In the present specification, the advantages of diffractive multifocal small aperture ophthalmic lens designs over refractive small aperture designs will be demonstrated and explained due to the basic characteristics of diffractive lenses as a combination of two virtual lenses with equivalent effective apertures. Each virtual lens is independently identifiable. One is a refractive lens defined by a base curve shape with image forming characteristics determined by Snell's law, and the other is a diffractive lens defined by a periodic structure of diffractive surface grooves with image forming characteristics determined by a phase coefficient. It is generally recognized that diffractive ophthalmic lenses are more beneficial than refractive lenses for full aperture lens applications due to their pupil-independent nature, where the light distribution between foci and therefore image quality is maintained even with different pupil sizes. An unexpected discovery of the present invention is that diffractive ophthalmic lenses are similarly more beneficial than refractive lenses for small aperture lens applications by achieving multi-peak performance with the same effective apertures for their virtual refractive and diffractive lenses. The multi-peak performance of the diffractive multifocal small aperture lens according to the present invention allows for not only significant halo suppression over prior art lenses, but also extended depth of focus and high distance image quality under different lighting conditions. The diffractive multifocal small aperture lens according to the present invention meets the necessary requirements to be a successful successor to monofocal lenses, enhancing patients' quality of vision beyond what existing products offer.

[0031] The accompanying drawings illustrate the invention. Such drawings are as follows: [Brief description of the drawings]

[0032] [Figure 1] Figure 1 shows a prior art full aperture diffractive multifocal lens with two diffractive foci and the out-of-focus blur at each focus. The out-of-focus blur at the far focus, formed by the out-of-focus image at the add focus, is the source of halo in multifocal lenses. [Diagram 2]Figure 2 illustrates the groove definition for a trifocal diffractive lens, where the overlapping blaze shapes of the synchronized diffractive bifocal surfaces produce a surface structure with low and high periodicity equivalent to the groove periodicity of each of the synchronized diffractive bifocal surfaces. [Diagram 3] Figure 3 shows a prior art small aperture lens based on the pinhole principle, which is one option to extend the DOF and suppress out-of-focus blur of the far image, suppressing halos at the expense of image quality under mesopic conditions. [Figure 4] Figure 4 shows a prior art refractive multifocal small aperture lens. The central refractive multifocal zone is designed to suppress out-of-focus blur at the far focus, thereby suppressing halos. Surface structure and asphericity in the central multifocal refractive zone are used to create a progressive, zonal, or combination of refractive powers to extend the DOF over a comparable single focus lens, but with limited results. [Diagram 5] Figure 5 shows a diffractive bifocal small aperture lens according to the present invention. The central diffractive zone is composed of two grooves to form two diffractive foci. The zeroth diffraction order is assigned to the far focus, and the first diffraction order is assigned to the add power. It was an unexpected result that the diffractive multifocal small aperture lens according to the present invention demonstrated a significant improvement in DOF and image quality for far vision over the refractive multifocal small aperture lens, while similarly reducing the magnitude of defocus blur from the full aperture multifocal lens. [Figure 6] Fig. 6 illustrates the optical design in terms of the longitudinal spherical aberration of two virtual lenses forming a diffractive small aperture lens. One virtual lens is a refractive lens formed by the combination of a base curve and a peripheral refractive zone represented by the far longitudinal spherical aberration LSAF. The other virtual lens is a diffractive lens formed by the phase coefficients of two grooves at the add focus represented by the added longitudinal spherical aberration LSAA. [Figure 7]Figure 7 shows a prior art technique for dealing with the optical steps of a diffractive multifocal surface by turning the optical steps into refractive subzones that refract the light to one of the multifocal focal points. This technique is sensitive to the height of the optical steps as well as the base curve shape and periodicity of the diffractive grooves, limiting its implementation to a small range of diffractive surface shapes. [Figure 8] Figures 8A, 8B and 8C show optical step modifications of a diffractive surface according to the present invention that minimize light scattering at the steps and also smooth the diffractive surface to minimize irritation to adjacent eye tissue. This is accomplished by splitting the optical step into a set of significantly reduced minor steps and a refractive section that directs light to one of the diffractive multifocal focuses. [Figure 9] Figure 9 illustrates a diffractive small aperture IOL according to the present invention. One has a single optical step between the first (central) and second (peripheral) grooves, which connects to the peripheral refractive zone without a step, the so-called "single transition" design. The other is a further variation of the single transition design, where the remaining optical step is smoothed using the technique shown in Figure 8C, the so-called "smooth transition" design. [Figure 10] 10A and 10B show in vitro measurements of the through-focus response at 50 lp / mm of a diffractive multifocal small aperture IOL according to the present invention, called the EDOF IVB IOL, including a smooth transition design, called the EDOF IVB IOL, performed in the SA Reference Eye Model with a 3 mm pupil diameter representing photopic conditions and a 4.5 mm pupil diameter representing mesopic conditions. [Figure 11] 11 shows the theoretical TFR for 50 lp / mm with SA eye model and 3 mm aperture for a diffractive multifocal EDOF IVB IOL according to the present invention and a prior art refractive multifocal small aperture IOL similar to the present invention in terms of light splitting between distance, central zone size, 1.75 add power, etc. The comparison demonstrates the superiority of the multi-peak performance of the diffractive multifocal SAL over the single-peak performance of the refractive multifocal SAL in terms of extended DOF range and distance image quality. [Figure 12] 12 illustrates a design method according to the present invention for constructing a multifocal lens to exhibit multi-peak performance. The method guides the selection of the size of the central multifocal zone, the add power, and the optical design of the lens surfaces. [Figure 13] Figures 13A-13D compare the out-of-focus distance blur, a source of halo, between a diffractive multifocal small aperture IOL (EDOF IVB IOL) and its analog, the refractive multifocal small aperture IOL referenced in Figure 11. The overall magnitude of the blur was comparable between the two small aperture designs, but there were differences in the distribution of light within the blur, reflecting the differences between diffractive and refractive multifocal principles. The comparison of light distribution supports the advantage of diffractive multifocal SALs over refractive multifocal SALs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] FIG. 1 shows a full aperture diffractive multifocal lens 100 of the prior art. In this lens, the full aperture is the effective aperture of the multifocal posterior surface 130, and the effective aperture occupies almost the entire lens surface, except for a small peripheral surface 110 outside the effective aperture. The lens 100 has a front refractive surface 120. The lens 100 forms two diffractive foci: a far focus 160 on an optical axis 220 at a retinal surface 170, and an add focus 180 on an optical axis 220 at an add image surface 190 located at a distance of the add power from the retinal surface 170. Marginal rays 140 and 140' pass through the focus 160 and form a defocus blur 210 at the add image surface 190. Marginal rays 150 and 150' pass through the add focus 180 and form a defocus distance blur 200 at the retinal surface 170. The blur 200 at the far focus is the source of the halo that occurs in hyperopia, and therefore its size and light intensity determine how uncomfortable the halo is for the patient. According to the illustrated ray trajectory shape, the blur at distance varies with the size of the zone that constitutes the add focus and the magnitude of the add power: the larger the zone size, the more blur, and the larger the add power, the more blur.

[0034] FIG. 2 illustrates a trifocal diffractive shape with no base curve contribution, which is the superposition of two blaze shapes of a diffractive bifocal surface. The blaze shape of the bifocal diffractive shape with high periodicity is called (surface A) and has 10 grooves (groove 1', etc.). The blaze shape of the bifocal diffractive shape with low periodicity is called (surface B) and has 5 grooves (groove 1, etc.). The surface shape of the trifocal diffractive lens without base curve contribution is called surface C, with structure 226 having the same low periodicity as the low periodicity of each groove of surface B, and structure 225 having the same high periodicity as the high periodicity of each groove of surface A. The periodicity of the grooves is defined in the bifocal lens by the period width of each groove, as shown in surfaces A and B. The periodicity of the structure is defined in the trifocal lens by the period width of each structure 225 or 226, as shown in surface C. The trifocal diffractive lens shows a more complex shape than the bifocal diffractive lens, defined by high and low periodicity structures. A trifocal diffractive lens has also been described in U.S. Patent No. 8,500,805 to Kobayashi et al., the entire disclosure of which is incorporated herein by reference, as having two superimposed blazed bifocal planes, where every diffractive groove of the low periodic blazed surface (B) matches every other groove of the high periodic blazed surface (A), i.e., the width of groove 1 on surface (B) matches the combined widths of grooves 1' and 2' on surface (A), the width of groove 2 matches the combined widths of grooves 3' and 4', and so on. Blazed surfaces (A) and (B) are said to be synchronized to form a trifocal plane (C) of structures with matching periodicities. Similar to the groove synchronization between surfaces A and B, high structure 225 and low structure 226 are also synchronized in trifocal plane (C). The low periodicity results in a low add power (AP) in the 3 focal planes (C) and the high periodicity results in a high add power (AP') in the 3 focal planes (C). Typically, the groove periodicity is selected such that AP' provides a near focus (around 3D add) and AP provides an intermediate focus (around 1.5D add).

[0035] As an example, in the case of an IOL, if the low periodic structure of surface (C) forms AP=1.75D at the IOL surface, the synchronized high frequency structure of surface (C) will form AP'≈3.00D at the IOL surface. According to the definition according to this patent application, the grooves of the trifocal surface (C) are defined as low periodic structures with the corresponding width of the low periodic grooves of surface (B). Thus, the diffractive trifocal small aperture lens has a central multifocal zone constructed with grooves 1" and 2" whose periodicity matches at least grooves 1 and 2 of the low periodic blazed diffractive shape. If only two structure widths of low periodicity, i.e., grooves 1" and 2", are used within the 2.5 mm diameter of the diffractive multifocal zone, the four structure widths of the high periodicity structure (two structure widths for each groove 1" and groove 2") are also included in the multifocal zone. If more low-periodic structures can be fitted within the 2.5 mm multifocal zone diameter, a diffractive trifocal small aperture lens can be constructed containing twice the number of high-periodic structure widths (two high-periodic structure widths for every low-periodic structure width).

[0036] FIG. 3 shows a prior art small aperture lens 230 based on the pinhole principle, which is one option for suppressing defocus blur and suppressing halos in distant images. The central small aperture 250 of the lens 230 is transparent and forms a focal point 270 on the optical axis 310, as shown by the peripheral light 260 and 260'. The part 240 of the lens 230 outside the aperture 250 is made opaque by other means, a mask, or a non-transparent material. The blur 300 at the retinal plane 280 is defined by the clinical image quality, which is generally set as 20 / 40 on the Snellen chart. The DOF is defined by the distance from the plane 290 where the blur 300' reaches the clinical image quality, for example the image quality of 20 / 40 vision. Comparing the blur 300 in FIG. 3 with the blur 200 in FIG. 1 for the DOF in FIG. 3 corresponding to the AP in FIG. 1, demonstrates that the magnitude of the blur at the retinal plane is significantly reduced for the lens operating on the pinhole principle compared to the full aperture lens. The magnitude of the blur is proportional to the size of the effective aperture 250 .

[0037] Since the retinal response is highly dependent on the amount of light that reaches it, the problem with pinhole lenses is that they reduce the amount of light passing through the lens, resulting in poor image quality, especially in low light conditions (mesopic vision). As a compromise, it is possible to select the effective aperture of an ophthalmic lens to pass enough light for operation under daytime (photopic) conditions, thereby expanding the DOF by at least 0.5D over monofocal lenses and also dealing with halos, but the use of such lenses is limited to unilateral applications where the fellow eye can assist vision under mesopic conditions.

[0038] FIG. 4 shows a prior art refractive small aperture lens 310. The lens 310 has a central refractive multifocal zone 330 that extends the DOF and suppresses blur 320 at the far focal point 380 at the retinal plane 390 to suppress halos. The opposite surface 350 is a refractive surface and a peripheral zone 340 that also forms the far focal point. The lens 310 trades the pinhole principle of the lens 230, which extends the DOF, for an increase in light by having a multifocal refractive surface 330 within the lens small aperture and a transparent refractive peripheral zone 340 outside the small central zone. In this case, a full aperture lens is used to form the far focal point 380 and a small aperture lens is used to form the add focal point 400 at the add surface 410. The full aperture peripheral rays 360 and 360' form a far focus 380 at the retinal plane 390, and the multifocal subaperture peripheral rays 370 and 370' may intersect the optical axis 420 within the range of the add power, i.e., from the far focus 380 to the add focus 400, but rays 370 and 370' are close to the add focus 400 so as to be effective for the extension of the DOF of the lens 310. The asphericity of the refractive surface in the central multifocal zone 330 can achieve the following (1), (2) or (3): (1) Gradual power change - e.g., a continuous change in power from the far focus at the center of the lens to the add focus at the periphery of the multifocal subaperture; (2) Zonal power change - the multifocal zone 330 consists of zones of distance and add power, e.g., a central zone of distance power and a peripheral zone of add power. (3) A combination of progressive and zonal designs in the central multifocal zone 330 for DOF enhancement over comparable monofocal lenses. The small aperture size 330 poses a challenge for progressive designs because it limits the area associated with the amount of light directed to, for example, 0.25D increments, i.e., each increment of power within the add range. The small multifocal zone diameter limits the add range because at least 20% of the light is required at each increment to provide an imaging effect - five 0.25D increments are required to provide 20% of the light at each increment. Zonal designs similarly result in limited DOF, as shown in FIG. 11. A combination of progressive and zonal designs is similarly unlikely to improve DOF.In the case of IOLs, this analysis is supported by clinical testing using clinical data from commercially available refractive SALs, such as Vivity, Eyhance, etc. LuxSmart Crystal IOLs extend DOF by approximately 0.5D over monofocal IOLs, i.e., they provide approximately 1D of DOF.

[0039] FIG. 5 shows a diffractive multifocal small aperture lens (DM SAL) 430 of the present invention. The lens 430 has a central diffractive multifocal zone 450 consisting of two grooves (groove 1 is element 451 and groove 2 is element 452). It also has a central step 470 between the grooves and a peripheral step 480 between groove 2 and the peripheral refractive zone 460. Each groove forms two foci: a far focus 530 at the retinal plane 540 and an add focus 550 at the add surface 560, which is the add power away from the retinal plane 540. The opposite surface 490 of the lens 430 is a non-multifocal refractive surface, i.e. spherical, aspheric or toric. The peripheral rays 500 and 500′ of the full aperture including the peripheral zone 460 form the far focus 530 on their intersection with the optical axis 570. Similarly, the peripheral rays 510 and 510' of the multifocal subaperture 450 coincide with the diffractive focus of the zeroth diffraction order to generate the far focus 530. The peripheral rays 520 and 520' of the multifocal subaperture zone 450 form the diffractive focus of the first diffraction order 550 at an add power from the retinal plane 540. The rays 520 and 520' generate a blur 440 at the retinal plane 540. The magnitude of the blur 440 is determined by the size of the diffractive multifocal subaperture zone 450; the smaller the zone, the smaller the blur 440. The minimum size of the zone 450 is the size of two diffractive grooves, groove 1 (central groove) as shown at 451 and groove 2 (peripheral groove) as shown at 452. It was an unexpected result of the present invention that the two grooves with the refractive peripheral zone provide outstanding image quality with an extended DOF beyond that of the refractive SAL design.

[0040] The peripheral step 480 can be eliminated by adjusting the sag at the periphery of the multifocal subaperture, i.e. by adjusting the lens thickness in the central diffractive zone 450, or by adjusting the sag of the refractive peripheral zone 460. The magnitude of the step is only on the order of 1-2 microns, and such adjustment does not affect the optical performance of the lens 430. Adjusting the sag leads to a "single transition" design of the diffractive multifocal subaperture lens as shown in FIG. 9, which leaves only one step 470 to account for light scattering or possible irritation to adjacent ocular tissues.

[0041] FIG. 6 shows an example of optimizing an ophthalmic lens design according to the present invention on the example of an EDOF IVB IOL. Similar optimizations can be applied to diffractive multifocal small aperture contact lenses, corneal inlays, and intraocular contact lenses. The basic principle of a diffractive bifocal lens is that it can be represented by two virtual lenses: one is a virtual refractive lens defined by a base curve, which produces a zeroth diffraction order assigned to the far focus; the other is a virtual diffractive lens defined by a diffractive groove shape, which produces a first diffraction order assigned to the add focus. Spherical aberration LSA at the far focus L F is virtually refracted by the base curve and the spherical aberration curve LSA FB The light rays that are refracted in the refractive peripheral zone and fall within half the diameter of the full aperture (the radius of the full aperture) and outside the small aperture radius are LSA FP The spherical aberration and the add focus are plotted along the horizontal axis, which represents the focus shift along the optical axis, where the location of the far focus FF is defined as zero on the axis, and the add power is located at the distance from the far focus to the add focus (AF). In optimizing the lens according to the invention, the LSA F presents a two-sign aspheric shape to extend the DOF around the far focus under photopic conditions (pupils up to 3 mm) and an LSA with sign change to suppress the contribution of spherical aberration to image quality in enlarged pupils (pupils 4-5 mm) corresponding to mesopic conditions. F The spherical aberration LSA at the addition focus formed by the groove Ais minimized to focus the light at the add focus, i.e., the grooves are designed to create a spherical wavefront, which maximizes the light concentration at the add focus for optimal quality of the added image.

[0042] The base curve with the peripheral refractive zone is defined by a standard aspheric form of the refractive aspheric surface.

number

[0043] The groove phase coefficient to produce a certain wavefront shape at the add focus is defined by a phase function.

number

[0044] FIG. 7 shows a prior art technique for addressing the optical step 460 of a diffractive multifocal lens 580 with an opposing refractive surface 590 by eliminating the width of the diffractive grooves 620 and 630, reducing them to grooves 620' and 630', and replacing the diffractive surface optical step 600 with a refractive subzone 610. The refractive subzone 610 is shaped to refract light to one of the diffractive focal points of the lens 580. The diffractive lens 580 is a combination of the diffractive grooves and the refractive subzone. The inclusion of the subzone 610 without substantial reduction of the grooves 620' and 630' depends on the base curve shape (convex, concave, its slope), the periodicity of the grooves, and the step height of the diffractive surface, so that the use of the technique is limited to certain diffractive surface configurations, such as convex surfaces.

[0045] 8A-8C show a variation in which the diffractive surface step has been similarly transformed into a refractive-diffractive shape. FIG. 8A shows a diffractive lens 650 with the original optical step 660, the counter surface 670, and the diffractive grooves 680 and 690. FIG. 8B shows a diffractive lens 700, which is a modification of the diffractive lens 650. The diffractive lens 700 has a transitional section consisting of a refractive section 710 and two small steps 720 and 730, which transform the original grooves 680 and 690 into grooves 680' and 690'. The lens counter surface is 670'. The refractive section 710 is shaped to refract light into one of the diffractive focal points of the lens 700. FIG. 8C shows a variation in which the transitional section has transformed the diffractive lens 650 into lens 750. The transition section consists of two refractive sections 760 and 770 connected by three small steps 780, 790, and 800, which convert the original grooves 680 and 690 into grooves 680'' and 690''. The opposite lens surface is 670''. Each refractive section 760 or 770 is shaped to refract light into one of the diffractive focal points of lens 750.

[0046] The selection of the multiple sections and the step heights depends on the goal of the step deformation. For example, to minimize light scattering, the step height should be H S< λ·n', where λ = blue wavelength of light, e.g., 0.4 microns, and n' = the refractive index of the surrounding lens medium. If the original step has height H, then the number of sections is in the ratio H / H S If the goal is to maximize contact lens comfort at the diffractive surface, then the minimum tear thickness under the contact lens (PoLTF) should be H less than the reported minimum thickness of 1 micron in order to fit each small zone within the minimum PoLTF and minimize corneal contact at the sulcus transitions. S Therefore, the smoothing technique of the present invention for smooth transition design minimizes light scattering at the steps between the grooves without losing light outside the diffractive focus, and avoids irritation of adjacent ocular tissues by diffractive surface steps.

[0047] Figure 9 shows pictures of EDOF IVB IOLs in two designs: one with one visible central step between the central and peripheral sulci and a smooth transition between the peripheral sulcus and the peripheral refractive zone, called a "single transition" design, and the other is a further modification of the single transition design with a smooth central step according to the technique shown in Figure 8C, called a "smooth transition" design.

[0048] Figures 10A and 10B show the results of optical testing of the EDOF VB IOL with smooth transition design. The tests used an optical bench Trioptics Optispheric IOL PRO2 for Through Focus Response (TFR), defined as MTF measurements for a spatial frequency of 50 lp / mm, taken at different diopter powers. TFR is an in vitro measurement of image contrast and selected spatial frequencies corresponding to a Snellen visual acuity of 20 / 40, commonly used in clinical trials to measure quality of vision. Tests were performed according to ISO specifications using a SA corneal lens representing the reference human cornea and a 3 mm pupil for photopic conditions (Figure 10A) and a 4.5 mm pupil for mesopic conditions (Figure 10B).

[0049] The in vitro MTF(50lp / mm) at 3mm shows a multi-peak performance with a distance peak of 0.53 and an add peak at the 0.2 level, separated by an add = 1.75D at the IOL surface. MTF(50lp / mm) = 0.53 represents good image quality, corresponding to the image quality of monofocal IOLs close to 4mm pupils, which is commonly encountered clinically and has not been reported to cause any visual problems. MTF(50lp / mm) = 0.1 represents clinically meaningful image quality, meaning that patients fitted with lenses that achieve MTF(50lp / mm) = 0.1 are expected to achieve visual acuity of 20 / 40 as well. The optimal design of the EDOF IVB IOL shows that the minimum image quality between the distance peak and the add peak is close to the clinically meaningful image quality defined as 0.1. This results in a DOF of 2D for a 3mm pupil, i.e. the expected visual range for 20 / 40 or better vision is from far distances to approximately 50cm from the eye.

[0050] According to FIG. 10B, the far image quality at 4.5 mm pupil is also remarkable, and the TFR also shows an add focus peak above MTF(50 lp / mm)=0.1. Similar results were recorded in the diffractive small aperture contact lens test. FIGS. 10A and 10B show good far image quality even under low light conditions (4.5 mm pupil) and also a significantly extended DOF over refractive small aperture ophthalmic lenses and pinhole ophthalmic lenses. Such impressive optical test results demonstrated by the diffractive small aperture ophthalmic lenses as shown by the example of EDOF IVB IOL by FIGS. 10A and 10B unexpectedly led to the analysis of the imaging capabilities of such lenses and also the development of a design methodology for small aperture ophthalmic lens design that meets the requirements for halo suppression, significantly extended DOF, and good far image quality.

[0051] FIG. 11 shows the theoretical TFR (50 lp / mm) of a diffractive multifocal small aperture lens (EDOF IVB IOL) on the SA eye model (reference corneal lens). The setup is the same as in the in vitro test of FIG. 10A. The horizontal axis represents the focus shift in millimeters instead of the diopter power used in the in vitro test, so that the add focus peak in FIG. 11 is located on the opposite side from the far focus peak compared to FIG. 10A. Similar to the TFR in FIG. 10A, the theoretical TFR (50 lp / mm) of the EDOF IVB IOL is calculated using the add power = 1.75D and DOF = 1.75D measured in diopters. D This paper demonstrates the multi-peak performance of diffractive multifocal small aperture lenses characterized by a DOF of 2D. As mentioned above, DOF is measured as the TFR (50 lp / mm) range of 0.1 modulation or greater, which defines clinically meaningful image quality.

[0052] FIG. 11 also includes the TFR (50 lp / mm) of the refractive multifocal small aperture IOL in the same SA eye model with a 3 mm pupil. The refractive multifocal central zone has the same zone diameter as the diffractive multifocal central zone of 2.3 mm. It is a zonal design that divides the light equally between two foci that are also spaced 1.75 D apart to match the AP of the diffractive multifocal small aperture lens, i.e., it has a central zone and peripheral small zone of equal area that refracts light to the far focus (0.0 mm) and a focus located 1.75 D from the far focus. The small zone and the peripheral zone at the far focus were aspherized to maximize light collection at the far focus and the 1.75 D add focus. The refractive design was the closest design to the diffractive design in terms of light distribution, allowing the best comparison between both multifocal small aperture designs. Despite the light collection at two foci, the theoretical TFR (50 lp / mm) of the refractive small aperture lens was 0.0 mm, ... RIt shows single-peak performance with a broad but single peak centered at the far focus at ≈1.7D. It is noteworthy that the far image quality of the refractive SAL is lower than that of the diffractive SAL. The theoretical comparison between the diffractive and refractive SALs largely supported the in vitro optical testing considerations and the clinical trial results. Thus, when the small aperture size is the same, the light division between the foci is very similar, and the focus is focused to the same add power, the multi-peak performance is superior to the single-peak performance in terms of far image quality and DOF.

[0053] FIG. 12 illustrates the formation of the multi-peak and single-peak performances shown in FIG. 11 and illustrates a design method to achieve multi-peak performance in a multifocal small aperture lens or any kind of multifocal lens. The example of the diffractive SAL and the refractive SAL in FIG. 11 is used to illustrate the method. The method comprises the following steps: Each of the diffractive and refractive lenses is a bifocal lens and can be represented by two virtual single-focus lenses that focus light at a distance focus and an add focus. The method is based on determining the TFR for a selected spatial frequency, for example 50 lp / mm, and obtaining a TFR (50 lp / m) for each virtual lens. In the case of the diffractive SAL, one virtual lens is a refractive lens whose TFR forms a zero-order distance peak, and the other is a virtual diffractive lens whose TFR forms a first-order add peak. The refractive SAL is also represented by two virtual lenses. One virtual lens includes a lens area with a distance power and its TFR forms a distance zone peak. Another virtual lens consists of a region of add power, whose TFR forms the add zone peak. Instead of a clinically relevant image quality, we use a "single / multi-band" with a 0.05 modulation range that is located above the clinically relevant image quality level. Typically, the clinically relevant image quality is 0.1 modulation as shown in Figure 11, but it may be different depending on the application of the method. In this method, the TFR of a multifocal lens combining two virtual single-focus lenses with a distance focus and an add focus shows single-peak performance if the TFR of the minimum overlap between the focal peaks of each virtual lens is above the single / multi-band, and shows multi-peak performance if the minimum overlap between the focal peaks of each virtual lens is below the single / multi-band. According to Figure 12, the minimum overlap (R) of the refractive multifocal small aperture IOL is above the single / multi-band, resulting in the single-peak performance shown in Figure 11. The minimum overlap (D) for diffractive multifocal small aperture IOLs is below the single / multiple zones, resulting in the multi-peak performance shown in Figure 11. Thus, the method leads to the selection of different combinations of multifocal zone diameter, add power, or optical design of the virtual lens to change the width of one or both TFRs of the virtual lens to convert single-peak performance to multi-peak performance or vice versa.

[0054] To explain the consideration physically, the overlap between the TFRs of each virtual lens represents the degree of optical interference between the light rays at each focus, which are directed to different focuses. For example, the TFR of the far zone peak of the refractive small aperture lens is very wide due to its small central small zone diameter, which results in a pinhole effect. The corresponding light rays still remain concentrated intensity at the add focus, which reduces the quality of the image formed by the add focus virtual lens of the refractive small aperture lens. Since the add zone peak generated by the ring-shaped small zone is low to begin with, the add zone peak at the add focus is completely suppressed in the integrated TFR of the refractive small aperture lens, thus resulting in a single-peak performance with the TFR peak centered at the far focus. Despite the similar light division, each virtual lens of the diffractive small aperture lens has the same effective aperture, both of which are defined by the size of the central multifocal zone, and as a result, for a selected add power and multifocal zone size, produces a relatively narrow and high image peak (add focus peak and far focus peak) with very small overlap. As a result, interference between the rays at each focus is limited, leading to diffractive small aperture lenses exhibiting multi-peak TFR performance.

[0055] The advantages of diffractive lenses for full aperture ophthalmic lenses, with their ability to maintain image quality at different foci even as the eye's pupil changes, are generally accepted. The present method describes the advantages of diffractive lenses for small aperture ophthalmic lenses, which do not take into account the eye's pupil changes. The advantages of diffractive lenses lie in their ability to generate multi-peak performance with excellent DOF and distance image quality, with a small size of the central multifocal zone required to address halos.

[0056] 13A-13D compare the causes of halo defocus blur for the diffractive multifocal small aperture IOL analyzed in FIG. 12 with the refractive multifocal small aperture IOL using spot diagrams, i.e., images of point sources. FIGS. 13A and 13B show the diffractive SAL focused image 820 and blur 810 for a 3 mm pupil and the focused image 830 and blur 810 for a 4.5 mm pupil. Due to the small aperture design with a small multifocal zone, the blur at distance is pupil independent, i.e., the small blur size and intensity is maintained with an enlarged pupil, which occurs under low light conditions, thus making the halo less noticeable. FIGS. 13C and 13D show the refractive SAL focused image 850 and blur 840 for a 3 mm pupil and the focused image 860 and blur 840 for a 4.5 mm pupil. Due to the small aperture design, the blur is pupil independent, similar to the diffractive design.

[0057] A comparison of the diffractive multifocal SAL blur 810 with the refractive multifocal SAL blur 840 demonstrates another potential advantage of diffractive lenses. The light distribution in the blur 810 is uniform because the effective aperture of the added focal virtual lens is the same size as the central multifocal zone. The light distribution in the refractive multifocal SAL blur 840 is not uniform because the effective aperture of the added focal virtual lens is ring-shaped, thus creating an area of ​​higher light intensity that may be more noticeable as a halo.

[0058] If we refer to the invention disclosed herein in its entirety by reference to a diffractive multifocal lens with a distance focus and an add focus, we automatically know that there will be at least two grooves. The reason for the 2.5 mm limitation is that this fits the definition of a "small aperture lens" known to those skilled in the art, that is, the pupil of the reference eye is 2.5 mm for an elderly patient in daylight, and in low light the pupil is even more dilated, so that the entire multifocal zone is always exposed, and therefore such a multifocal diameter is independent of the light conditions.

[0059] On the other hand, if the multifocal zone is too small, the peak from the virtual lens will be too broad. From the inventors' findings, it is assumed that the diffractive multifocal zone should be as small as possible to minimize the halo (this is dictated by the minimum number of grooves of 2), but not too small, since only a low percentage of light reaches the add focus in the pupil of the reference eye. Also, a strong pinhole effect should be avoided, as the light beam formed by the pinhole at the add focus will extend the focal depth, and therefore likely to interfere with the focused light beam at the far focus, leading to a single-peak performance. Thus, the minimum size of the multifocal zone is also about 1.5 millimeters.

[0060] The applicant teaches that at least 20% of the light directed within the diffractive multifocal zone of a transmissive ophthalmic lens is incident on one of the far and add foci. This 20% refers to the percentage of light split by the diffractive multifocal zone but not the peripheral zone, which is generated by the diffractive multifocal zone. The central property of a diffractive lens is that the grooves work together to create constructive interference at certain points called diffraction orders. The height (step height) controls how the light is split between these diffraction orders. A person skilled in the art can choose one diffraction order, e.g. the zeroth order, as the far focus and another, e.g. the first order, as the add focus. The position of the diffraction order is determined by the periodicity of the grooves: the wider the grooves (low periodicity), the greater the separation between the foci, i.e. the lower the add power (as in surface B of FIG. 2), and the narrower the grooves (high periodicity), the closer the separation between the foci, i.e. the higher the add power (as in surface A of FIG. 2). At one step height, at least 20% of the light may be focused at the far focus to produce the minimum image intensity required to make distant objects visible, and approximately 65% ​​is directed to the add focus because the nature of diffractive lenses splits the remaining light among the higher diffraction orders. One skilled in the art can select a different step height to direct at least 20% of the light to be focused at the add focus to produce an appropriate light intensity image of objects closer to the eye at the add focus at the retina.

Claims

1. A transmissive ophthalmic lens having a first surface. the first surface is opposite the second surface; the first surface comprising a centrally disposed diffractive multifocal zone surrounded by peripherally disposed refractive non-multifocal zones; the second surface is a refractive non-multifocal surface; the diffractive multifocal zone is 2.5 millimeters or less and configured to mitigate halo and 1.5 mm or more and configured such that the transmissive ophthalmic lens exhibits multi-peak performance with a distance focus and an add focus; at least 20% of light directed within the diffractive multifocal zone of the transmissive ophthalmic lens is incident on one of the far focus and the add focus; A transmissive ophthalmic lens, wherein the refractive non-multifocal zone is configured to form the far focus.

2. 10. The lens of claim 1, wherein the first groove and the second groove of the diffractive multifocal zone are the only two grooves.

3. 3. The lens of claim 2, comprising a transition from the second groove to the peripherally disposed refractive non-multifocal zone that does not include a step.

4. 3. The lens of claim 2, including a smooth transition from the second groove to a peripherally disposed refractive non-multifocal zone.

5. The lens of claim 1 , wherein the non-multifocal refractive surface of the second surface is spherical, aspheric, or cylindrical.

6. The lens of claim 1 , wherein the transmissive ophthalmic lens is an intraocular lens.

7. 10. The lens of claim 1, wherein the transmissive ophthalmic lens is an intraocular contact lens.

8. The lens of claim 1 , wherein the transmissive ophthalmic lens is a corneal inlay lens.

9. The lens of claim 1 , wherein the transmissive ophthalmic lens is a contact lens.

10. 10. The lens of claim 1, wherein the diffractive multifocal zone has a base curve that is aspheric.

11. 10. The lens of claim 1, wherein the diffractive multifocal zone has a base curve with the refractive non-multifocal zone being a two-sign aspheric surface.

12. 10. The lens of claim 1, wherein the diffractive multifocal zone comprises aspheric diffractive grooves for minimizing spherical aberration at the add focus.

13. 10. The lens of claim 1, wherein the diffractive multifocal zone comprises a base curve with the refractive non-multifocal zone being a two-sign aspheric surface configured for the far focus, and aspheric diffractive grooves configured to minimize spherical aberration at the add focus.

14. 10. The lens of claim 1, wherein the diffractive multifocal zone comprises high and low periodic structures synchronous with each other, each width of the low periodic structures including two widths of the high periodic structures.

15. 3. The lens of claim 2, wherein the diffractive multifocal zone comprises no more than two grooves of low periodic structure, each groove consisting of two widths of high periodic structure.

16. 3. The lens of claim 2, wherein a transition is disposed between the first groove and the second groove, the transition consisting of a refractive portion connected to each groove by a step, the refractive portion configured to refract light to either the far focus or the add focus.

17. 3. The lens of claim 2, wherein a smooth transition is disposed between the first groove and the second groove, the transition consisting of a refractive portion connected to each groove, the refractive portion configured to refract light to either the far focus or the add focus.

18. 10. The lens of claim 1, wherein the diffractive multifocal zone is configured to exhibit multi-peak performance with an add power of 1.75±0.5D.

19. A transmissive ophthalmic lens comprising: a first surface; the first surface is opposite from the second surface; the first surface comprising a centrally disposed diffractive multifocal zone surrounded by peripherally disposed refractive non-multifocal zones; the second surface is a refractive non-multifocal surface; the diffractive multifocal zone is 2.5 millimeters or less and configured to mitigate halo and 1.5 mm or more and configured such that the transmissive ophthalmic lens exhibits multi-peak performance with a distance focus and an add focus; the first groove and the second groove of the diffractive multifocal zone are the only two grooves; at least 20% of the light directed within the diffractive multifocal zone is incident on one of the far focus and the add focus; the diffractive multifocal zone having a base curve that is a two-sign aspheric surface near a far focus and aspheric grooves configured to minimize spherical aberration at the add focus; A transmissive ophthalmic lens, wherein the refractive non-multifocal zone is configured to form the far focus.

20. 1. A method of designing a multifocal ophthalmic lens for multi-peak performance, comprising: providing the multifocal ophthalmic lens with a first surface, the first surface being opposite a second surface, the first surface comprising a centrally located diffractive multifocal zone surrounded by peripherally located refractive non-multifocal zones, the second surface being a refractive non-multifocal surface; dividing the diffractive multifocal zone into two virtual monofocal lenses each producing a corresponding distance focus and an add focus; Selecting clinically relevant image qualities to generate single / multi-band images; obtaining a through-focus response of each virtual monofocal lens at a selected spatial frequency for a selected eye model and pupil size; overlapping the through focus responses at each corresponding far focus and add focus to determine a minimum overlap; Comparing the minimum overlap with the single / multiple bands, Above the single / multiple zones, the performance of the multifocal lens is expected to exhibit single-peak performance; below said single / multiple bands, said multi-peak performance is achieved; modifying one or more of a diffractive multifocal zone diameter, an add power, or an optical design of a virtual lens to modify one or both widths of the through-focus response of the virtual lens to convert the single-peak performance to the multi-peak performance; A method for providing the above.

Images