WO2022039682A1 - Lentille oculaire diffractive zonale - Google Patents

Lentille oculaire diffractive zonale Download PDF

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Publication number
WO2022039682A1
WO2022039682A1 PCT/TR2020/050735 TR2020050735W WO2022039682A1 WO 2022039682 A1 WO2022039682 A1 WO 2022039682A1 TR 2020050735 W TR2020050735 W TR 2020050735W WO 2022039682 A1 WO2022039682 A1 WO 2022039682A1
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Prior art keywords
lens
grating
diffractive
multifocal
ophthalmic
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PCT/TR2020/050735
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English (en)
Inventor
Sven Thage Sigvard HOLMSTRÖM
Amin TABATABAEI MOHSENI
Original Assignee
Vsy Biyoteknoloji Ve Ilac Sanayi A.S.
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Application filed by Vsy Biyoteknoloji Ve Ilac Sanayi A.S. filed Critical Vsy Biyoteknoloji Ve Ilac Sanayi A.S.
Priority to EP20780384.2A priority Critical patent/EP4200664A1/fr
Priority to PCT/TR2020/050735 priority patent/WO2022039682A1/fr
Publication of WO2022039682A1 publication Critical patent/WO2022039682A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
    • G02C7/00—Optical parts
    • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
    • G02C7/04—Contact lenses for the eyes
    • G02C7/041—Contact lenses for the eyes bifocal; multifocal
    • G02C7/042—Simultaneous type
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/14—Eye parts, e.g. lenses, corneal implants; Implanting instruments specially adapted therefor; Artificial eyes
    • A61F2/16—Intraocular lenses
    • A61F2/1613—Intraocular lenses having special lens configurations, e.g. multipart lenses; having particular optical properties, e.g. pseudo-accommodative lenses, lenses having aberration corrections, diffractive lenses, lenses for variably absorbing electromagnetic radiation, lenses having variable focus
    • A61F2/1654—Diffractive lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
    • G02C7/00—Optical parts
    • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
    • G02C7/06—Lenses; Lens systems ; Methods of designing lenses bifocal; multifocal ; progressive
    • G—PHYSICS
    • G02—OPTICS
    • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
    • G02C2202/00—Generic optical aspects applicable to one or more of the subgroups of G02C7/00
    • G02C2202/20—Diffractive and Fresnel lenses or lens portions

Definitions

  • the present disclosure generally relates to ophthalmic lenses and, more specifically, to ophthalmic eyeglasses, ophthalmic contact and intra-ocular multifocal lenses, the multifocality being provided by a combination of diffraction zone(s) and refraction zone(s).
  • Diffractive lenses for ophthalmological applications are constructed as hybrid lenses with a diffractive pattern added onto a refractive body. Often one side of the lens is purely refractive, while the other side has a diffractive grating superpositioned over a refractive base line.
  • the refractive baseline can be spherical, or alternatively have an aspherical shape of sorts.
  • the diffractive pattern is added onto the refractive baseline.
  • the diffractive part can in general be applied to any of the two sides of the lens, since when a diffractive pattern is to be combined with a refractive surface with some special feature it generally does not matter if they are added to the same side or if one is added to a first side and the other to a second side of the lens.
  • two diffractive patterns may be combined either by superpositioning on one side, or by adding them on separate sides in an overlapping fashion.
  • the optical power of the lens for a specific diffraction order can be calculated by addition of the refractive base power and the optical power of that diffraction order.
  • a diffraction grating that functions as a lens has a pitch that in absolute terms varies 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 so that the optical path difference (OPD) through the lens to the focal point of the first diffraction order has a difference of exactly one wavelength per period.
  • OPD optical path difference
  • diffractive lens is sometimes used for the well-known Fresnel lenses.
  • a Fresnel lens consists of concentric zones with vertical steps in the zone junctures.
  • the zones in a Fresnel lens are often of equal width and the optical properties of each zone can be analyzed with refractive theory.
  • the diffractive lenses discussed here are lenses which require diffractive analysis.
  • phase-matched Fresnel lens As taught by Rossi et al. in their 1995 study titled "Refractive and diffractive properties of planar micro-optical elements".
  • This type of lens makes use of a sawtooth diffractive unit cell and a step height corresponding to a phase modulation of exactly 2n.
  • planar microlenses that display refractive as well as diffractive behavior in a manner adjustable by phase-matching number M j for each diffractive zone. An increased M j increases the height as well as the width of respective zone.
  • each M j equals 1 all energy goes into the first order, meaning that these are monofocal diffractive lenses.
  • the only diffractive shape available with 100% efficiency is a sawtooth profile constructed to have full modulation of a design wavelength, that is that the vertical jump in zone junctures corresponds to an phase retardation that is an integer multiple of the number of wavelengths.
  • ophthalmic diffractive trifocal lenses make use of sawtooth profiles. Combining sawtooth profiles of two bifocal diffractive lenses to achieve trifocality is known in the art. This results in diffractive lenses with the usable orders arranged asymmetrically with respect to the 0 th order, e.g. a trifocal lens might make use of orders 0, +1, and +2 orders or 0, +2, and +3.
  • a diffractive trifocal lens is disclosed wherein the optical thickness of the surface profile changes monotonically with radius within each zone, while a distinct step in optical thickness at the junction between adjacent zones defines a step height.
  • the step heights for respective zones may differ from one zone to another periodically so as to tailor diffraction order efficiencies of the optical element wherein the step heights may alternate between two values.
  • EP 2377493 a method of manufacturing an aphakic intraocular lens that is capable of ensuring every multi-focusing effect more securely, while reducing the impact of aperture changes and lens eccentricity is suggested.
  • EP 2503962 discloses an intraocular lens including an anterior surface and a posterior surface and having a substantially antero-posterior optical axis wherein one of these anterior and posterior surfaces includes a first diffractive profile forming at least one first diffractive focal point of order +1 on said optical axis, and a second diffractive profile forming a second diffractive focal point of order +1, said two diffractive focal points are distinct and at least one portion of said second diffractive profile is superposed to at least one portion of the first diffractive profile.
  • US 9223148 proposes a lens with more than two powers, one of which is refractive and one other diffractive in the least.
  • EP 3435143 teaches an ophthalmic multifocal diffractive lens comprising focal points for near, intermediate and far vision.
  • the lens comprises a light transmissive lens body providing a refractive focal point, and a periodic light transmissive diffraction grating, extending concentrically over at least part of a surface of the lens body and providing a set of diffractive focal points.
  • the diffraction grating is designed to operate as an optical wave splitter, the refractive focal point providing the focal point for intermediate vision and the diffractive focal points providing the focal points for near and far vision.
  • the diffraction grating has a phase profile arranged for varying a phase of incident light at the lens body optimizing overall efficiency of light distribution in the refractive and diffractive focal points.
  • the orders of this lens are arranged symmetrically around the 0 th order and operates in at least the -1, 0, and +1 orders.
  • Diffractive lenses with sharp transitions in the diffraction profile including e.g. lenses with sawtooth profiles and binary profiles, give rise to machining difficulties and, for a finished lens, scattering of light, increased incidence of several unwanted optical phenomena such as stray light and glare i.e.
  • a general approach to construct a lens is also known from the teaching of US5017000.
  • the resulting diffractive lens is a diffractive lens operating in the 0, +1, and +2 orders.
  • a trifocal lens can be constructed by starting from a linear phase grating optimized for diffraction efficiency and an equal light distribution between usable diffraction orders.
  • Linear phase gratings have been researched and developed with the intent of creating beam splitters.
  • the general theory of optimization of linear phase gratings is taught in Romero and Dickey's 2007 study titled "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.
  • the existing literature on diffractive phase grating has focussed on finding optimal solution, meaning maximized diffraction efficiency, for the case of equal intensity distribution among a certain number of orders.
  • the new focussing properties of the eye as a whole have to be measured. That is, the complete visual system consisting of the new lens and the remainder of the eye of the user is measured integrally, as a first objective indication of the result of the implantation of the IOL.
  • an autorefractometer In practice, most physicians rely on a simple measurement by an autorefractometer. For sawtooth type IOLS, for example, the measurement indeed typically returns the far focus.
  • some combinations of autorefractometers and lenses can provide the power of the refractive base, which is often not at same optical power as far vision.
  • the height of the grating can be reduced to increase the intensity of the refractive focal point.
  • sawtooth diffractive gratings this can be used to increase one of the outermost diffraction orders relative to all other orders, which can sometimes be advantageous.
  • a feature often desired in multifocal lenses is to provide a relatively even intensity distribution for mesopic conditions while providing a much stronger relative intensity for far vision for the larger pupils available in scotopic conditions.
  • sawtooth multifocal diffractive lenses this is often provided with the help of apodization, which in this context refers to a diffractive grating with decreasing height with increasing radius, as taught in 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.
  • a lens using a smooth sinusoidal grating this simple method can't be used for this purpose.
  • Aforementioned W02019020435 discloses lenses derived from a linear phase grating optimized for equal intensity between three orders. The intensity distribution is then fine tuned by laterally shifting the diffraction grating along the radial direction.
  • the current state of the art does not allow for the use of lenses using smooth sinusoidal gratings with higher diffraction efficiency than this.
  • One underlying reason for this is because gratings with very high diffraction efficiencies require undesired intensity distributions when used in well-known configurations.
  • an improved ophthalmic lens that makes use of smooth sinusoidal diffractive gratings, but solves the limitations of such lenses in current state-of-the-art and make possible lens designs that provide larger freedom in tuning and controlling the relative intensities of three or more diffraction orders or focal points, in particular to provide markedly different intensity ratios for different aperture sizes, providing a possibility to measure a diffractive focal point easily and improving the ability to take advantage of diffraction gratings with very high diffraction efficiency.
  • Primary object of the present invention is to provide an ophthalmic multifocal lens, at least comprising three focal points, one of them providing far vision.
  • Another object of the present invention is to provide an ophthalmic multifocal lens comprising at least a first and a second portion, providing a first and a second refractive optical power respectively, the portions being arranged concentrically.
  • a further object of the present invention is to provide an ophthalmic multifocal lens comprising a symmetric diffractive grating providing at least three focal points combined with the first portion, the 0 th order of said diffractive grating adds, for a design wavelength, to the optical power of the first portion.
  • a still further object of the present invention is to provide an ophthalmic multifocal lens comprising a symmetric diffractive grating such that one of the diffraction orders other than the 0 th order of the diffractive grating adds to the refractive optical power of the second portion.
  • a still further object of the present invention is to provide an ophthalmic multifocal lens wherein the refractive base powers of the first and second portions are different, and at least one of the two have a sawtooth diffractive grating with arbitrary height.
  • a still further object of the present invention is to provide an ophthalmic multifocal lens with optimized multifocality wherein the diffractive efficiency is greatly improved.
  • an ophthalmic multifocal lens at least comprising a focal point for far vision.
  • the lens having a light transmissive lens body comprising a symmetric (i.e. optical powers are symmetrically aligned around 0 th order) diffraction grating extending concentrically in radial direction from an optical axis of the lens body across a part of a surface of the lens body.
  • the lens comprises at least a first and a second portion, each portion having a different refractive base line and each portion providing a refractive optical power that is different than that of any other portion, the portions being arranged concentrically, and a symmetric diffractive grating on the first portion, arranged so that, for a design wavelength, at least two of the focal points of the diffraction grating coincide with and are contributed to by the refractive power of the two portions.
  • asymmetric diffraction gratings e.g. sawtooth lenses.
  • Sawtooth gratings often make use of the zeroth order and one or more orders on one side of the zeroth order (i.e. they are all either positive of negative).
  • symmetric diffractive lenses make use of orders that are ordered symmetrically around the Oth order.
  • Symmetric diffraction gratings as the terms are used here, are defined by which orders they utilize, not by the relative light distribution in these orders.
  • a symmetric diffraction grating can be tuned to provide different light intensities to each order.
  • the lens body in accordance with the present disclosure, comprises a first portion that coincides with the central area of the lens body and is combined with a multifocal symmetric diffraction grating, one of the non-zero orders providing at least far vision for a user, and a second portion with a substantially different refractive base power that provides additional far vision.
  • the present disclosure is based on the insights that by providing a multifocal center of the ophthalmic lens, having a non-zero order focal point coinciding with the refractive power of the periphery, make possible lens designs with well-developed and highly efficiency multifocality for small apertures (photoopic and mesopic conditions), but with dominating Far vision for large pupils (Scotopic vision), it provides opportunity for accurate in-vivo measurements of the far vision of the lens, and it allows for useful and practical designs with very high diffraction efficiencies of the underlying linear diffraction grating, as, for example, the strong far vision of the periphery can balance the weaker diffractive far vision of a highly efficient grating.
  • the focal point of the monofocal peripheral portion coincides with the target focal point for far vision, for example, this provides to ophthalmologists a portion of the lens that can be measured unambiguously.
  • the present invention allows for a very different intensity distributions for different pupil sizes without the need of any diffraction patterns containing sharp edges, such as those in sawtooth or binary diffraction profiles.
  • lenses according to the invention can provide three or more foci for photopic and mesopic conditions with a higher diffraction efficiency than what is possible using asymmetric diffraction gratings combined with e.g. a very strong far vision provided in scotopic conditions.
  • a typical autorefractometer will measure at the perimeter of the pupil of the patient. However, an ophthalmologist often will measure in light conditions that render the pupil to be approximately 3 mm in diameter. If, for example, the multifocal central portion of a lens according to the present invention is 2.3 mm in diameter a 3 mm pupil would with the type of autorefractometer mentioned return the refractive power provided by the peripheral portion.
  • lenses having a continuous and smooth profile without any sharp edges are less susceptible to glare or scattering due to non-uniformities in the path that incident light travels through the lens, and also to produce less halos, while being easier to manufacture according to a calculated profile compared to sawtooth type or binary type gratings or reliefs, for example.
  • a higher diffraction efficiency in any case leads to less stray light.
  • For manufacturing technologies based on diamond turning or similar forms of machining a smooth profile will be more reliable as well as faster and cheaper to fabricate than profiles with sharp edges such as sawtooth or binary profiles.
  • Smooth diffractive geometries in accordance with the present disclosure allow for polishing and therefore lead to a significant increase in yield, compared to lenses having sharp transitions in their height profile.
  • Present invention aims to teach combinations of certain types of gratings and zones with differing refractive base power, that are enabling technical outcomes related to the improvement of the shortcomings noted in the prior art.
  • teaching of the present invention puts forth lenses having multifocal portions with orders symmetrically arranged around the 0 th order with monofocal portions, arranged concentrically with respect to one another.
  • teaching of the present invention also provides multifocal lenses marked with a wider set of intensity distribution profiles, most notably those with a wider difference in intensity distribution between different apertures. Addressing this, lenses with strong multifocality for small apertures (e.g. photopic and mesopic condition), but with a dominant far vision aspect for larger pupils, i.e. scotopic vision are proposed.
  • the highest possible diffraction efficiency for most useful intensity distribution for diffractive trifocal lenses is provided by smooth sinusoidal surfaces with usable orders symmetrically arranged around the 0 th order.
  • the orders of such a lens are arranged symmetrically around the 0 th order and operates in at least the -1, 0, and +1 orders. Gratings with that arrangement of usable orders will henceforth be referenced as symmetric gratings.
  • Diffraction efficiency is a measure of how much of the optical power is directed into the desired diffraction orders, or, when talking about diffractive lenses in particular, how much of the optical power is directed into the desired focal points.
  • Diffraction efficiency is a measure of how much of the optical power is directed into the desired diffraction orders, or, when talking about diffractive lenses in particular, how much of the optical power is directed into the desired focal points.
  • the highest possible diffraction efficiency is reached by using the principles of a phase- matched Fresnel lens, which makes use of a sawtooth or jagged type diffraction pattern.
  • Fresnel lenses Because of the sharp edges of a sawtooth or jagged type diffraction pattern, as a consequence of the discontinuities in the diffraction profile, Fresnel lenses have all the drawbacks described above, in particular with respect to glare and halos, while it is also difficult to fabricate such structures with high precision. However, for a trifocal lens, lenses designed to provide an as good vision as possible to three distinct focal points, the optimal grating is one without any sharp edges.
  • a lens such as an intraocular lens more remarkably a multi-zonal multifocal intraocular lens that is capable of correcting optical aberrations for a variety of human eyes with different corneas under a wide range of lighting conditions and that may perform in different orientations is proposed.
  • the lens according to the present invention is an intraocular lens comprising at least a first and a second portion, wherein each portion having a different refractive baseline and each said portion provides an optical power that is unidentical to that of any other portion.
  • said at least a first and a second portion are arranged concentrically; the first portion comprising a symmetric diffractive grating, one of the diffraction orders (other than the Oth order) thereof substantially coinciding with the optical power of the second portion.
  • FIG. 1 shows, in a simplified manner, the anatomy of the human eye 10, for the purpose of illustrating the present disclosure.
  • the front part of the eye 10 is formed by the cornea 11, a spherical clear tissue that covers the pupil 12.
  • the pupil 12 is the adaptable light receiving part of the eye 10 that controls the amount of light received in the eye 10.
  • Light rays passing the pupil 12 are received at the natural crystalline lens 13, a small clear and flexible disk inside the eye 10, that focuses light rays onto the retina 14 at the rear part of the eye 10.
  • the retina 14 serves the image forming by the eye 10.
  • the posterior cavity 15, i.e. the space between the retina 14 and the lens 13, is filled with vitreous humour, a clear, jelly-like substance.
  • the anterior and posterior chambers 16, i.e. the space between the lens 13 and the cornea 11, is filled with aqueous humour, a clear, watery liquid.
  • Reference numeral 20 indicates the optical axis of the eye 10.
  • the lens 13 For a sharp and clear far field view by the eye 10, the lens 13 should be relatively flat, while for a sharp and clear near field view the lens 13 should be relatively curved.
  • the curvature of the lens 13 is controlled by the ciliary muscles (not shown) that are in turn controlled from the human brain.
  • a healthy eye 10 is able to accommodate, i.e. to control the lens 13, in a manner for providing a clear and sharp view of images at any distance in front of the cornea 11, between far field and near field.
  • Ophthalmic or artificial lenses are applied to correct vision by the eye 10 in combination with the lens 13, in which cases the ophthalmic lens is positioned in front of the cornea 11, or to replace the lens 13. In the latter case also indicated as aphakic ophthalmic lenses.
  • Multifocal ophthalmic lenses are used to enhance or correct vision by the eye 10 for various distances.
  • the ophthalmic lens is arranged for sharp and clear vision at three more or less discrete distances or focal points, often including far intermediate, and near vision, in Figure 1 indicated by reference numerals 17, 18 and 19, respectively.
  • Far vision is in optical terms when the incoming light rays are parallel or close to parallel.
  • Light rays emanating from objects arranged at or near these distances or focal points 17, 18 and 19 are correctly focused at the retina 14, i.e. such that clear and sharp images of these objects are projected.
  • the focal points 17, 18 and 19 may correspond to focal distances ranging from a few meters, to tens of centimeters, to centimeters, respectively.
  • ophthalmologists choose lenses for the patients so that the far focus allows the patient to focus on parallel light, in the common optical terminology it is that the far is focused on infinity.
  • Ophthalmologists will, when testing patients, commonly measure near vision as 40 cm distance from the eyes and intermediate vision at a distance of 66 cm, but other values can be used.
  • the amount of correction that an ophthalmic lens provides is called the optical power, OP, and is expressed in Diopter, D.
  • the optical power of a cascade of lenses is found by adding the optical powers of the constituting lenses, for example.
  • the optical power of a healthy human lens 13 is about 20 D.
  • FIG 2a shows a top view of a typical ophthalmic multifocal aphakic intraocular lens 30, and Figure 2b shows a side view of the lens 30.
  • the lens 30 comprises a light transmissive circular disk-shaped lens body 31 and a pair of haptics 32, that extend outwardly from the lens body 31, for supporting the lens 30 in the human eye. Note that this is one example of a haptic, and there are many known haptic designs.
  • the lens body 31 has a biconvex shape, comprising a center part 33, a front or anterior surface 34 and a rear or posterior surface 35.
  • the lens body 31 further comprises an optical axis 29 extending transverse to front and rear surfaces 34, 35 and through the center of the center part 33.
  • the optical axis 29 is a virtual axis, for the purpose of referring the optical properties of the lens 30.
  • the convex lens body 31, in a practical embodiment, provides a refractive optical power of about 20 D.
  • a periodic light transmissive diffraction grating or relief 36 is arranged, comprised of rings or zones extending concentrically with respect to the optical axis 29 through the center part 33 over at least part of the front surface 34 of the lens body 31.
  • the diffraction grating or relief 36 provides a set of diffractive focal points.
  • the diffraction grating or relief 36 may also be arranged at the rear surface 35 of the lens body 31, or at both surfaces 34, 35.
  • the diffraction grating 36 is not limited to concentric circular or annular ring-shaped zones, but includes concentric elliptic or oval shaped zones, for example, or more in general any type of concentric rotational zone shapes.
  • the optic diameter 37 of the lens body 31 is about 5 - 7 mm, while the total outer diameter 38 of the lens 30 including the haptics 31 is about 12- 14 mm.
  • the lens 30 may have a center thickness 39 of about 1 mm.
  • the haptics 32 at the lens body 31 are not provided, while the lens body 31 may have a plano-convex, a biconcave or plano-concave shape, or combinations of convex and concave shapes.
  • the lens body may comprise any of Hydrophobic Acrylic, Hydrophilic Acrylic, Silicone materials, or any other suitable light transmissive material for use in the human eye in case of an aphakic ophthalmic lens.
  • FIG 3 schematically illustrates, the optical operation of a known periodic light transmissive diffraction grating or relief 42 of a lens 40 comprising a biconvex light transmissive circular disk-shaped lens body 41.
  • This type of lens, combining refractive and diffractive power is also referred to as a hybrid lens.
  • the lens 40 is shown in a cross-sectional view in radial direction of the lens body.
  • the diffraction grating or relief 42 comprises a plurality of repetitive, contiguously arranged, prism shaped transparent diffractive optical elements, DOEs, 43.
  • the DOEs 43 extend in concentric zones around the center part 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.
  • the DOEs 43 of the diffraction grating 42 are shown as well-known jagged or saw-tooth type elements, comprising a continuous, sloping light receiving surface 44, such as a linear or curved sloping light receiving surface 44.
  • Gratings or reliefs in which the DOEs 43 alternate between two heights, spaced apart in radial direction of the lens body 41, are called binary type reliefs (not shown).
  • the repetition period or pitch of the DOEs 43 monotonically decreases in radial direction from the center or optical axis of the lens and varies with the square of the radial distance. Pitch depends on the refractive index, the design wavelength, and the optical power of the first diffraction order.
  • Pitch is determined so that the optical path difference (OPD) through the lens to the focal point of the first order has a difference of exactly one wavelength per period.
  • OPD optical path difference
  • the periods (grating pitch) are equidistant, more exactly the period pitch in r 2 is
  • one side of the lens is purely refractive, while the other side has a diffractive grating super positioned over a refractive base line.
  • the refractive baseline can be e.g. spherical or having some sort of aspherical shape.
  • the diffractive pattern, which is added onto the refractive baseline may in general be applied to any of the two sides of the lens. Therefore; if a diffractive pattern is to be combined with a refractive surface with some special feature, it generally bears little importance if they are added to the same side or, if one is added to a first side and the other to a second side of the lens.
  • two diffractive patterns may be combined either by superpositioning on one side, or by adding them in an overlapping fashion on separate sides.
  • combining of two lens structures shall always be understood as allowing for both possibilities.
  • the optical power of the lens for a specific diffraction order are calculable by addition of the refractive base power and the optical power of that diffractive order.
  • An incident or primary light beam 46 that passes the grating 42 and the lens body 41 is, respectively, diffracted and refracted and results in an output or secondary light beam 47.
  • the refracted and diffracted light waves i.e. secondary light beams 47 form a plurality of focal points at the optical axis 48 of the lens 40, due to constructive interference of the light waves 47.
  • Constructive interference occurs when the optical path difference between light waves 47 arriving from the lens body 41, at a particular focal point, is an integer multiple of their wavelength, i.e. the light waves are in-phase, such that their amplitudes add-up in a reinforcing manner.
  • the difference in optical path length travelled by interfering light waves 47 from the lens body 41 is an odd multiple of half of the wavelength, such that a crest of one wave meets a trough of another wave, the light waves 47 partly or completely extinguish each other, i.e. the light waves are out of phase, not resulting in focal points at the optical axis 48 of the lens body 41.
  • the points of constructive interference at various distances from the lens body 41 are generally designated diffraction orders.
  • the focal point that corresponds to the focal point that originates due to refractive operation of the curvature of the lens 40 is indicated by order zero, 0.
  • m +1, +2, +3, etc.
  • the diffraction relief 42 can be designed to provide focal points at different distances from the lens body 41.
  • the periodic spacing or pitch of the DOEs 43 substantially determines where the points of destructive and constructive interference occur at the optical axis 48 of the lens, i.e. the position of the diffractive orders at the optical axis 48.
  • the grating or relief In case of a diffraction grating or relief 42 providing diffraction orders that are regularly spaced at both sides of the zero order, the grating or relief is called a symmetric wave splitter or diffractive grating, as the incident light beam 46 is diffracted or split into orders that are symmetrically arranged with respect to the zero order.
  • a grating or relief producing a non-regular spacing of diffractive orders, such as +1, +2, -3, -5 is called an asymmetric diffractive grating.
  • the common cases of diffraction gratings producing usable orders at 0 th order and +1 or 0 th , +1, and +2 are also asymmetric diffractive gratings.
  • optical points for providing or correcting far, intermediate and near vision to the human eye can be set beforehand, and a diffraction grating 42 is provided that maximizes the overall efficiency of the light energy received from the incident light beam 46 in these pre-set focal points is optimal.
  • a diffraction grating optimizing overall efficiency of the light distribution in pre-set or target diffraction orders is found from determining a linear phase-only function or phase profile that generates the target diffraction orders with a maximum overall efficiency q or figure of merit defined as the sum of the normalized light energies of all these target orders.
  • These diffractive gratings can then be shaped into lenses by adjusting the argument so that they have equidistant periods in the r 2 space.
  • the lens body 41 may comprise a plano-convex, a biconcave or plano-concave shape, and combinations of convex and concave shapes or curvatures (not shown).
  • Figure 4a shows a top view of an ophthalmic multifocal aphakic intraocular lens 50, working in accordance with the present invention
  • Figure 4b shows a side view of the lens 50.
  • the difference over the prior art, exemplified in Figure 2 are in the optics of the lens.
  • the lens body 56 has a biconvex shape, comprising a front or anterior surface 54 and a rear or posterior surface 55.
  • the skilled person would know that for some embodiments one or both of the anterior surface 54 and the posterior surface 55 might be concave or planar, depending on the refractive baseline needed for a specific application.
  • the lens body in accordance with the present disclosure, comprises a peripheral lens portion 53 and a central lens portion 51 that is combined with a symmetric multifocal diffraction grating 52.
  • the central lens portion 51 and the peripheral lens portion 53 have different refractive powers.
  • the lens is constructed such that, for a design wavelength, the one of the diffractive orders of the symmetric multifocal diffraction grating 52 contributes to the refractive focal point of the peripheral lens portion 53.
  • Figure 4 shows a lens where one side of the lens is purely refractive, while the other side has a diffractive grating super positioned over a refractive base line. As explained above in relation to Figure 3 this is only one configuration. It is possible, for example, to distribute the diffractive grating over both sides, or superposition the diffractive grating to either side of a plano-convex or plano- concave lens.
  • the shape or height profile of the refractive base line for any of the portions of the lens may be selected among a plurality of continuous refraction profiles known from monofocal lenses, such as spherical, or based on monofocal diffractive surface, or aspherical surfaces, which are among the most general known shapes of monofocal lenses known in the art.
  • Monofocal diffractive surfaces refers to the phase-matched Fresnel lenses discussed earlier. By adjusting the phase matching number an arbitrarily wide unbroken monofocal zone can be created through diffractive optics. It is possible combine different types of refractive surfaces in one lens, so that the central portion and the peripheral portion consist of different types of refractive surfaces.
  • the manufacturing of refractive of diffractive surfaces can be carried out by any of laser micro machining, diamond turning, 3D printing, or any other machining or lithographic surface processing technique, for example.
  • Figure 5 shows a monofocal diffractive lens operating in the first order.
  • Figure 5a of these images shows the diffractive profile as it actually is, while 5b shows the lens plotted versus the square of the radius, clearly showing the periodicity in r 2 -space.
  • the vertical axes show the profile height H(r).
  • the pitch is determined so that the optical path difference (OPD) through the lens to the focal point of the first diffraction order has a difference of exactly one wavelength per period.
  • OPD optical path difference
  • To show the periodicity of a diffraction grating one will often, as here, plot the diffractive lens profile versus the square of the radius (often referred to as r 2 - space).
  • the periods (grating pitch) is equidistant, more exactly the period pitch in r 2 -space is 2 ⁇ /D, where A is the design wavelength and D the optical diffractive power of the first order in diopters.
  • the lens in Figure 5 is a monofocal lens of the first order, which is accomplished by making use of a sawtooth diffractive unit cell and a step height corresponding to a phase modulation of exactly 2n (two pi, or two times pi). All energy in a lens of such fashion goes into the +1 order, or -1 order, depending on the definition. This is the only type of diffraction grating with 100% diffraction efficiency.
  • phase matching number By adjusting the phase matching number to m the height of each zone is increased to m2 ⁇ and the width of each zone in r 2 -space is multiplied with m.
  • Such a lens is said to be a monofocal diffractive lens operating in the m th order.
  • Lenses with m>1 are sometimes referred to as a Multi-Order Diffractive (MOD) lens, which is sometimes used to decrease the thickness of a lens and to decrease longitudinal chromatic aberrations.
  • MOD Multi-Order Diffractive
  • Figure 6 shows a trifocal diffractive lens profile of the sawtooth type and its spectrum.
  • the upper graph of this figure conveys the diffractive profile of said lens, plotting the height versus the radius from the optical center.
  • the lower graph contains the spectrum of said lens, with the intensity, I, as a function of the diopter.
  • the intensity is displayed in arbitrary units. If the height of the monofocal diffractive lens in Figure 5 is decreased so the phase modulation corresponding to the step height is less than 2n the light will be split between the 0 th order and the 1 st order.
  • One way to create a trifocal diffractive lens is to combine two such bifocal diffractive lenses with different first diffractive orders.
  • a feature often desired in multifocal lenses is to provide a relatively even intensity distribution for mesopic conditions while providing a much stronger relative intensity for far vision for the larger pupils available in scotopic conditions.
  • sawtooth multifocal diffractive lenses this is often provided with the help of apodization, which in this context refers to a diffractive grating with decreasing height with increasing radius, as taught in 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.
  • apodization directly applied onto a multifocal lens based on a symmetric grating would lead to a very strong 0 th order for large pupils.
  • the diffractive lens profile shown in Figure 6 providing far vision, intermediate vision, and near vision.
  • the lens is modelled for a refractive base of 18.5D, which is directly used for far vision.
  • the diffractive powers of the lens are 1.5D (intermediate vision), and 3D (near vision).
  • asymmetric diffractive gratings The vast majority of diffractive ophthalmological lenses known in the art utilize "asymmetric" diffractive gratings, as demonstrated with reference to Figures 5 and 6.
  • asymmetric diffractive gratings When ascribing symmetric or asymmetric property to multifocal ophthalmic lenses, what is considered is which orders it makes use of, or renders useful.
  • Symmetric diffractive lenses utilize of orders in a way that is symmetric around the 0 th order. Note that symmetric diffraction gratings are defined by which orders they utilize, not by the light distribution in these orders. Some symmetric diffractive lenses may be tuned so that there is a significant difference in light intensity between e.g. +1 and -1 orders.
  • tuning the diffraction grating's unit cell needs to be manipulated so as to become asymmetric, however this is not what is referred to with symmetric or asymmetric diffraction gratings.
  • a diffraction grating tuned as such would still be considered a symmetric diffraction grating.
  • symmetric and asymmetric are not commonly used referring to diffraction gratings, they are nonetheless very suitable for the teaching of the disclosed invention, and are in line with the use of terms in the literature in the way that a diffraction grating is often defined by which orders are rendered useful to the user. In a bifocal lens, more than two orders will have non-zero light intensity, but the intensity difference (in particularly at the design wavelength) tends to be obvious.
  • Figure 7 shows again a trifocal lens according to EP20170183354 and W02019020435, this time with the modelled spectrum.
  • This symmetric lens operates in the the -1, 0, and +1 orders.
  • Such symmetric lenses tend to perform in higher diffraction efficiencies than the asymmetric sawtooth lenses.
  • comparatively smoother shapes of the gratings are quite desirable due to a greatly limited prevalence of scattered light, glare and halos.
  • the Osipov 2015 study additionally puts forward the idea that, lenses with smooth gratings should be "more biocompatible because of the reduction of the debris precipitation effect".
  • the commonly investigated case is the case of equal intensity distribution between the chosen orders.
  • the highest attainable diffraction efficiency for equal intensity distribution in a linear grating for three focal points is 92.56%.
  • the phase profile, lin (x) for such a linear grating was originally defined by Gori et al. as: wherein: ⁇ lin (x) is the phase profile of a linear phase grating, x is the axis or distance over which the grating extends, [mm]. With this definition one period is exactly 1 unit long.
  • a lens with a phase profile function (r) built on this grating could be defined as wherein: S is the lateral shift and has a constant value ranging between
  • A(r) is the amplitude modulation function, often chosen to have a constant value
  • T is the period or pitch of the diffraction grating in r 2 space, [mm 2 ].
  • the value of the amplitude modulation function 4(r) may be constant over the lens surface, such as between 1.05 - 1.15, for example, in order to take into account a reduction in the height of the diffractive grating by a finishing operation of the lens, such as by polishing. For lens bodies not requiring such a finishing operation, the value of A(r may be 1. Note that this formula provides the phase modulation. When creating an actual lens the refractive index of the lens material as well as the surrounding medium have to be taken into account, which is trivial for the skilled person.
  • the lateral shift, S is a way to express the phase shift of the periodic grating, the choice of which tunes the behaviour of the lens. Since the term phase has multiple meaning in this document the term is elsewhere in the document simply referred to as the lateral shift.
  • Reference numeral 60 in Figure 7a shows an example of height profile or amplitude profile of a continuous periodic diffraction profile in r 2 space, expressed in mm 2 , as disclosed by W02019020435, and Figure 7b shows the same height function along a linear scale as function of the radial distance r, based on the phase profile function ( ⁇ (r) according to equation (2).
  • the lens is strictly periodic in r 2 -space, as expected.
  • the amplitude of the height profile H(r) 61 is depicted at pm-scale along the vertical axis.
  • the design wavelength of the lens is assumed at 550 nm
  • the index of refraction of the lens body is set to 1.4618
  • the index of refraction of the medium surrounding the lens body is assumed to be 1.336.
  • the amplitude modulation function A(r) is a constant at 1.07
  • the period T 0.733 mm 2 in r 2 space
  • the lateral shift S 0.
  • Reference numeral 60 refers to the outer circumference or baseline curvature of the front surface 34 of the lens body 30 having a diffraction grating or relief 36 comprising the height profile H(r) 61 (see Figures 2a and 2b).
  • a diffractive profile can be located on either or both of the front and back surfaces of a lens.
  • the amount of light diffracted by the lens having the height profile H(r) 51 is shown by computer simulated light intensity distributions in Figure 7c.
  • Reference numeral 64 refers to diffraction order 0, providing a focal point for intermediate vision
  • reference numeral 62 refers to diffraction order -1, providing a focal point for far vision
  • reference numeral 63 refers to the +1 diffraction order, providing a focal point for near vision.
  • the intensity /of the diffracted light is depicted in arbitrary units along the vertical axis as a function of the optical power in diopter, D, depicted along the horizontal axis.
  • the computer simulated light intensity distributions assume a biconvex lens body 31 of an ophthalmic lens 30 of the type shown in Figures 2a, 2b, designed for targeting a zero order focal point at 20 diopter, D, and first order focal points at 21.5 D and 18.5 D, symmetrically positioned with respect to the zero order. That is, providing a focal point for intermediate vision at 20 D for the zeroth order focal point, providing a focal point for far vision at 18.5 D by diffraction order -1, and 25 providing a focal point for near vision at 21.5 D by the +1 diffraction order.
  • these optical powers or focal points may differ for actual lenses, dependent on the target focal points.
  • the examples are calculated using MATLABTM based simulation software. For this specific example, a pupil size of 6 mm diameter is assumed.
  • Figure 8a shows a height profile 71 as a function of the radial distance r of a diffraction grating in an embodiment of a trifocal intraocular ophthalmic lens.
  • the design wavelength ⁇ , the index of refraction n of the lens body, the index of refraction n m of the medium surrounding the lens body, the amplitude modulation function A(r), and the period T in r 2 space, for this embodiment, are identical to the parameters of the embodiment illustrated by Figures 7a - 7c.
  • diffractive profile is laterally shifted, as illustrated in Figure 8a is modulated by the lateral shift S having a fixed non-zero value.
  • Reference numeral 70 refers to the outer circumference or baseline curvature of the front surface 34 of the lens body 30 having a diffraction grating or relief 36, comprising the height profile H(r) 71, extending from the optical axis.
  • Figures 8b, 8c and 8d show computer simulated light intensity distributions for the lens of Figure 8a for varying pupil sizes.
  • the relative intensity, rel. I, of the refracted and diffracted light with respect to the maximum intensity in one focal point is depicted as a function of the optical power in diopter, D, depicted along the horizontal axis.
  • the examples are again calculated using MATLABTM based simulation software.
  • the computer simulated light intensity distributions assume a biconvex lens body designed for targeting a zero-order focal point at 20 diopter, D, and first order focal points at 21.5 D and 18.5 D, symmetrically positioned with respect to the zeroth order.
  • Figure 8b shows the light intensity distribution 72 for a pupil size having a diameter of 1 mm.
  • Figure 8b shows the light intensity distribution 72 for a pupil size having a diameter of 1 mm.
  • the focal point actually measured with the autorefractometer is not one of the diffractive focal points but the intermediate or refractive focal point.
  • Figure 8c shows the light intensity distribution for a pupil size having a diameter of 3 mm.
  • a pupil of such size covers a larger part of the diffractive profile and of the convex surface of the lens as for the 1 mm pupil size shown in Figure 8b.
  • Reference numeral 73 refers to diffraction order 0, providing the focal point for intermediate vision.
  • Reference numeral 74 refers to the -1 diffraction order, providing a focal point for far vision
  • reference numeral 75 refers to the +1 diffraction order, providing a focal point for near vision.
  • a greater part of the incident light is distributed in the focal point for near vision 75, compared to the amount of light distributed in the focal points for intermediate 73 and far vision 74.
  • Figure 8d shows the light intensity distribution for a pupil size having a diameter of 6 mm.
  • a pupil of such size generally covers the whole optical system of an ophthalmic lens.
  • Reference numeral 73 again, refers to diffraction order 0, providing the focal point for intermediate vision
  • reference numeral 74 refers to diffraction order -1, providing the focal point for far vision
  • reference numeral 75 refers to the +1 diffraction order, providing the focal point for near vision.
  • Figure 9 Shows one more lens using the optimal diffractive unit cell for equal distribution over three orders ([1 1 1]).
  • Figure 9a shows the unit cell for and a histogram showing the resulting order distribution.
  • the diffraction efficiency of the optimal diffraction grating for an equal split over three orders is 92.56%.
  • Figure 9b show the diffractive profile of a lens based on the unit cell above.
  • Figure 9c the resulting energy distribution of the lens in Figure 9b can be seen.
  • the spectrum is modelled at an aperture of 3mm and 20D base refractive power is assumed.
  • equation (1) the optimal linear phase grating for a trifocal grating with equal intensity distribution is shown. It is often advantageous to design a specific optical grating with the required properties.
  • the grating in equation (3) can be used for a trifocal part of a lens by substituting x with the square of the lens radius r. More precisely, to arrive at the equivalent of equation (2) x should be replaced by (r 2 - S(r))/T. Note that the complete apparatus to find the optimum grating is in not included in the present document, as this is available in the referenced literature.
  • the formula in (3) can also be arbitrarily extended to describe other configurations. Of special interest are lenses with four, five, and seven focal points.
  • phase profile ⁇ lin (x) as defined in (3) one arrives at: wherein: (r) is a continuous periodic phase profile function of the lens diffraction grating, r is the radial distance or radius outwardly from the optical axis of the lens body, [mm],
  • A(r) is the amplitude modulation function, often chosen to have a constant value
  • S(r) is the lateral shift and has a constant value ranging between 0 and , and
  • T is the period or pitch of the diffraction grating in r 2 space, [mm 2 ].
  • a diffraction grating having a (near, intermediate, far) split of [1.2, 1, 1], for example, a way to express an optimal diffractive grating fulfilling these requirements is by applying the teachings of Romero et al. in terms of equation (3), having a diffraction efficiency and the constants set as follows:
  • Figure 10 is analogous to Figure 9, but based on the diffractive unit cell optimized for the intensity distribution [1.2 1 1]. This distribution has a diffraction efficiency of 91.26, that is somewhat lower than that for the equal distribution. The way the it is done here the orders in the lens are related to the intensities as [Near, Intermediate, Far]. The chosen convention is that strongest power (corresponding to the focal point closest to the user) is listed first, and the weakest power last.
  • the diffractive lens profile in Figure 10c is identical to the diffractive lens profile in Figure 9c except for the unit cell chosen, with identical refractive indices and lateral shift. The spectrum is modelled at an aperture of 3mm and 20D base refractive power is assumed.
  • Figure 11 is analogous to Figure 9 and Figure 10, but based on the diffractive unit cell optimized for the intensity distribution [1.1 1.2 1].
  • This distribution has a diffraction efficiency of 93.88, that is somewhat higher than that for the equal distribution in Figure 9 as well as higher than the unit cell used in Figure 10. It is notable that the diffraction efficiency of this unit cell is higher than that for the qual intensity split over three orders, which is usually referred to as the optimal split in the literature.
  • the optimal split in the literature For the specific case of trifocal gratings very high diffraction efficiencies are reached for high 0 th order intensities, this is however not a general rule, as is discussed further down. Specifically, this is not the case for diffraction gratings optimized for five focal points.
  • the diffractive lens profile in Figure 11c is identical to the diffractive lens profile in Figure 9c and in Figure 10c, except for the unit cell chosen, with identical refractive indices and lateral shift.
  • the spectrum is modelled at an aperture of 3mm and 20D base refractive power is assumed. It is demonstrated in Figure 11c that the relative Far intensity is decreased compared to Figure 9c as well as Figure 10c.
  • the spectrum is modelled at an aperture of 3mm and 20D base refractive power is assumed.
  • Figure 12 illustrates how selection of diffractive gratings combined with choice of the lateral shift can be used to design a suitable multifocal lens to show the relationship between the diffraction efficiency of the grating and the behaviour of the resulting lens.
  • optical is typically used for the most efficient grating for a certain number of orders with equal intensity distribution over those orders. However, this is by no means necessarily the case for lenses: For certain lens configurations, a higher total diffraction efficiency can be utilized very well. As can be understood from the demonstrations in Figures 9, 10, and 11, the highest possible diffraction efficiency is dependent on the required intensity distribution.
  • the intensity distribution can be tuned (within some limits) by lateral shift of the grating. This is explained in detail in EP20170183354 (See Figures 6 and 7). A shift with a full period will provide the original lens.
  • Figures 12a, 12b, and 12c. show for three different gratings how the simulated intensities for Far, Near, and Intermediate change at a 3mm aperture for different amount of lateral shift when constructing the lens. Each lateral shift is set as a portion of the period.
  • the three gratings for gratings 1, 2, and 3 are, respectively, optimized for light distributions [1 1 1], [1 1.2 1], and [1.1 0.8 1.2].
  • gratings have the respective diffractions efficiencies of 92.56%, 94.51%, and 88.62%.
  • the lenses are configured to provide far vision, intermediate vision (at the 0 th order), and near vision.
  • intermediate vision at the 0 th order
  • near vision For each diffraction unit cell these three graphs show the intensity for each focal point as a function of the lateral shift, S, in equation (4).
  • the behaviour in figures 9a through 9c is the expected, where a higher chosen 0 th order leads to a higher intermediate. The same being true, mutatis mutandis, for the other orders. It should, however, be noted that an order that is stronger in the underlying linear phase grating is not necessarily stronger for each possible S.
  • Figure 12d plots the sum intensity, in arbitrary units, for each grating. A high sum indicates an efficient diffractive lens.
  • the graph in Figure 12d compares the summation of the three intensities for each chosen diffractive grating. The summation of peaks is very good indication of effective diffractive efficiency. It can be seen that change in this parameter overall corresponds closely to the change in diffraction efficiency between gratings.
  • high diffraction efficiency lenses will of course provide more usable light to the eye, but they also reduce the amount of light going to undesired diffraction orders and light going to undesired effects such as halo and glare.
  • trifocal gratings with very high diffraction efficiency used over the full optics of the lens will lead to undesired intensity distributions.
  • symmetrical lenses a very high diffraction efficiency tends to lead to a very strong zeroth order.
  • Figure 13a shows a pentafocal (having five focal points) diffractive unit cell optimized for the intensity distribution [0.8 1.2 0.80 1.20.80].
  • This linear phase grating yields a very high diffraction efficiency of 98.98%. This is significantly higher than the optimized diffractive grating for the pentafocal grating with an equal intensity split, [1 1 1 1 1], for which the intensity distribution is 92.13%.
  • Figure 13b show the diffractive lens based on the diffractive unit cell in Figure 13a.
  • This specific implementation has the pitch of the diffractive grating arranged to provide 2.13 D between the strongest and the weakest focus assuming a design wavelength of the lens of 550 nm, the index of refraction of the lens body is for this embodiment set to 1.492, and the index of refraction of the medium surrounding the lens body is assumed to be 1.336.
  • This specific example would thus to a user provide five focal points mostly distributed over and in between far and intermediate vision.
  • By rearranging the pitch of the diffractive grating it is of course possible to have a pentafocal lens providing near vision in addition for far and intermediate vision.
  • Figure 13c is the modelled spectrum corresponding to the diffractive lens profile in Figure 13b, shown as relative intensities, with the highest peak set equal to 1. The spectrum is modelled at an aperture of 6mm and 20D base refractive power is assumed.
  • Figures 14a, 14b, 14c and 14d show one way to construct a lens according to the invention by combining a trifocal area with a different refractive base than the periphery of the lens.
  • Mj phase matching numbers
  • An m of 3 means that the period in r 2 space is three times as long and also that the modulation of the step height is identical to 3 times the design wavelength (in this case the design wavelength is 550nm).
  • Figure 14b shows a completely trifocal lens constructed from a linear phase grating optimized for the light distribution of [1 1.05 0.95] with a diffraction efficiency of 93.34%, higher than a grating optimized for equal intensity splitting.
  • S as defined by (3) and (4) is set to 0.62 * T.
  • Figure 14c shows the profile of a lens made according to the present invention. It can for example be constructed by addition of the central portions of Figures 14a and 14b, the cut-off point being indicated by the dashed lines. The cut-off point is here configured to utilize approximately three periods of the trifocal grating.
  • the height of the trifocal grating in Figure 14b has been adjusted according to get a desired light distribution.
  • the role of the monofocal grating in figure 14A is only to add refractive power to the central portion.
  • any type of refractive surface can be used, such as spherical or any form of aspherical surface.
  • a properly designed aspherical refractive surface is advantageous.
  • a refractive base of 18.32D is added (not shown in any figure).
  • For pupil sizes smaller than or close to the diameter than the central portion such a lens provides strong trifocal behaviour, in this case with a relatively even light distribution. For larger pupils the far vision will increase relative to other foci. For a 6mm pupil, appearing normally in scotopic conditions only, this lens will mostly function as a monofocal lens.
  • the refractive power of the central zone is 1.675D higher than that of the base refractive power of the periphery.
  • the central portion of the lens has a refractive (zeroth order) providing intermediate vision, while the periphery of the lens provides far vision.
  • the two non-0 th diffractive orders of the trifocal part of the lens provide near vision and enhance the far vision, respectively.
  • the lens profile is shown less the base refractive power of far vision. In effect, for a relatively small pupil (for photopic and mesopic vision) the lens provides a focal point for far vision and two additional focal at approximately 1.675D and 3.35D.
  • This type of lens geometry enables multifocal lenses with a wider set of intensity distribution profiles, especially with a wider difference in intensity distribution between different apertures.
  • the type of lens shown in Figure 14c provides for smaller pupils (photopic and some mesopic environments) the functionality of a highly light efficient, tunable symmetric diffractive gratings, while for larger pupils (scotopic and some mesopic environments) the lens will work more and more as a monofocal lens optimized for far vision.
  • a lens utilizing a diffraction grating as the one in Figure 14b with a high diopter, very high diffraction efficiency over the entire optics of the lens would not be suitable for e.g. an intraocular lens.
  • Such an intensity profile is often desired for photopic and mesopic conditions, but is not suitable for scotopic conditions.
  • the configuration provided in Figure 14c the high diffraction grating can be utilized fully for smaller pupils, while providing very strong far vision for large pupils.
  • this lens configuration provides for an ophthalmologist a way to carry out in-vivo measurements from a monofocal portion of the lens, which is sometimes advantageous.
  • this monofocal portion coincide with the far vision, which is most of the times the preferred focal point to measure.
  • Figure 15 shows another lens according to the present invention.
  • Figure 15a is a trifocal diffractive unit cell optimized for the intensity distribution [1 0.95 1.1]. This linear phase grating yields a diffraction efficiency of 91.38%.
  • Figure 15b a lens profile is shown, less the refractive base of 18.32D.
  • the unit in Figure 15a is used to create a simple trifocal grating (not shown) with a first order optical power of 1.675D and an S, as defined by (3) and (4), set to 0.57 * T.
  • the trifocal grating is retained in a central portion of the lens only and is combined with an additional refractive power of 1.675D, in accordance with the present invention.
  • the cut-off point is here chosen to retain two periods of the diffractive grating.
  • the modelling for different aperture sizes in Figure 15c shows similar results to the modelling in Figure 14d, but with some obvious differences.
  • the lens in 15b has a smaller multifocal portion leading to a less pronounced trifocality at the 3mm aperture and a stronger far vision.
  • One way to make use of symmetric diffractive gratings with more than three focal points is to make lens similar to the ones described in Figure 14c and Figure 15b, but with a diffractive grating for four or more significant orders. Such a lens would provide an even more continuous vision.
  • focal points of the symmetric diffractive lens according to the patent are arranged for far vision, intermediate vision, and one or more diffractive order forming focal point(s) at optical power(s) in between the far and intermediate visions.
  • Existing EDOF lenses on the market often target only far and intermediate powers, but don't offer a continuous vision between these distances.
  • Linear phase gratings have in this document been shown as one possible starting point to create multifocal lenses.
  • the existing theory and understanding of such gratings can also be used to analyze lenses, if the underlying linear phase grating can be extracted from the lens.
  • the simplified flow diagram 160 in Figure 16 illustrates steps of a method of measuring the profile of an ophthalmic multifocal lens and to determine the diffraction efficiency of the underlying diffraction grating. The direction of the flow is from the top to the bottom of the drawing.
  • a region of the lens is selected and measured, preferably along a line normal to the optical axis.
  • a part of the refractive base is actually a monofocal phase matched Fresnel lens or an MOD lens, when this is the case also this monofocal diffractive structure is to be subtracted from the measured profile.
  • a third step, block 163, the resulting lens profile is plotted versus the square root of the distance from the optical center.
  • the underlying linear phase is obtained by converting the height profile in the previous step to a phase profile using the design wavelength, refractive index of said ophthalmic lens and the refractive index of the designated environment in the eye.
  • a fifth step, block 164 the diffraction efficiency for the usable orders and the linear grating is calculated. Once the phase profile of the underlying linear phase grating is known, it is possible to calculate the diffraction efficiency. If the phase grating is (x) then the transmission function can be written as
  • each diffraction order or of a combination of diffraction orders can be found by study of the Fourier coefficients of the transmission function. If the length of the diffractive unit cell is 1, the Fourier coefficients can be written as
  • an ophthalmic multifocal lens comprising at least three focal points, said lens having a light transmissive lens body comprising at least a first portion with a first refractive base power that coincides with the central area of said light transmissive lens body and a second portion with a second refractive base power is proposed.
  • said ophthalmic multifocal lens further comprises a multifocal symmetric grating combined with said first portion, wherein the combination with said first portion is configured such that the 0 th order of said multifocal symmetric grating substantially coincides with the base refractive power of said first portion and the second refractive base power adds to one of the diffractive, non-Oth order power of said grating.
  • the first refractive base of the said first portion and said a second refractive base of said second portion ophthalmic multifocal lens are unequal.
  • said at least one first portion, said at least one second portion, or both said portions comprise sawtooth diffractive grating.
  • said sawtooth diffractive grating is monofocal.
  • said multifocal lens is a trifocal lens and as such said multifocal symmetric grating provides three focal points.
  • said multifocal lens is a pentafocal lens and as such said multifocal symmetric grating provides five focal points.
  • said multifocal symmetric grating provides a number of focal points selected from a group including, but not limited to, four, seven, nine focal points.
  • said multifocal symmetric grating of said at least one first portion and said multifocal symmetric grating of said at least one second portion provide different numbers of focal points.
  • said multiple focal points provided by said multifocal symmetric gratings are configured for far, intermediate and near vision.
  • said multiple focal points provided by said multifocal symmetric gratings are arranged so that the power difference between the focal point having the highest optical power and the focal point having the lowest optical power does not exceed 2 Diopter.
  • said ophthalmic multifocal lens further comprises a transition zone between said at least one first portion and said at least one second portion, whereby a refractive base power or a range of refractive base powers between the refractive powers of said at least one first and at least one second portion is provided.
  • a method of measuring the profile of an ophthalmic multifocal lens preferably from the optical center of said ophthalmic lens and outwards is proposed.
  • said method comprises the step of selecting the region of the measured profile with a diffractive pattern.
  • said method comprises the step of removal of the curvature of the base refractive power of the selected region.
  • said method comprises the step of removal of any diffractive periodic grating(s) with a maximum phase modulation higher than the design wavelength of said ophthalmic lens.
  • said method comprises the step of plotting the resulting lens profile versus the square root of the distance from the optical center.
  • said method comprises the step of obtaining linear phase grating via converting the height profile in the previous step to a phase profile using the refractive index of said ophthalmic lens and the refractive index of the designated environment in the eye.
  • said method comprises the step of computing the diffraction efficiency for the usable orders and the design wavelength of the linear grating.

Abstract

L'invention concerne une lentille ophtalmique multifocale, comprenant au moins trois points focaux, ladite lentille ayant un corps de lentille transmettant la lumière comprenant au moins une première partie ayant une première puissance de base de réfraction qui coïncide avec la zone centrale dudit corps de lentille transmettant la lumière et une seconde partie ayant une seconde puissance de base de réfraction est proposée. Ladite lentille ophtalmique multifocale comprend en outre un réseau symétrique multifocal combiné à ladite première partie, la combinaison avec ladite première partie étant conçue de telle sorte que l'ordre 0 dudit réseau symétrique multifocal coïncide sensiblement avec la puissance de réfraction de base de ladite première partie et la seconde puissance de base de réfraction s'ajoute à l'une des puissance de diffraction d'ordre 0 dudit réseau.
PCT/TR2020/050735 2020-08-21 2020-08-21 Lentille oculaire diffractive zonale WO2022039682A1 (fr)

Priority Applications (2)

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EP20780384.2A EP4200664A1 (fr) 2020-08-21 2020-08-21 Lentille oculaire diffractive zonale
PCT/TR2020/050735 WO2022039682A1 (fr) 2020-08-21 2020-08-21 Lentille oculaire diffractive zonale

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