Trifocal ophthalmic lens

Abstract

The present invention relates to a trifocal intraocular lens comprising an optical part (102) and a periphery that are separated by an optical boundary, wherein the optical part (102) is formed by a refractive base (106) and a diffractive profile (101) superimposed on the refractive base (106) to provide focused vision at near, intermediate and far distances. The diffractive profile changes from a sinusoidal shape at the centre to a kinoform shape towards the periphery, so that the zero diffraction order is determined by the refraction of the refractive base designed to focus the light incident on the lens for intermediate vision. The refractive base combined with the first positive order of the diffractive element is designed to focus the light incident on the lens for near vision, and the refractive element combined with the first negative order of the diffractive element is designed to focus the light incident on the lens for far vision. In this way, apodisation is avoided during design and manufacture and trifocal performance is improved.

Description

[0001] TRIFOCAL OPHTHALMIC LENS

[0002] STATE OF THE ART

[0003] The present invention relates to a diffractive ophthalmic lens, more specifically to a trifocal ophthalmic lens.

[0004] A diffractive multifocal intraocular lens (IOL) is a medical device with optical properties designed for implantation within the eyeball (FIG 1). These lenses allow for increased depth of field when the eye loses its natural ability to accommodate.

[0005] The classic diffractive profile of a multifocal lens is described by a function that segments into different zones of equal area, arranged periodically according to the square of the radial coordinate, known as Fresnel zones. In general, each zone ends and begins with a more or less abrupt discontinuity with respect to the adjacent zones, forming a rotationally symmetric structure that acts as a phase diffraction grating. This periodic structure of optical regions introduces phase shifts in the incident light. In the field of diffractive multifocal lenses, it is common practice to incorporate the diffractive structure onto a base refracting surface. From the more or less constructive combination of light generated by each phase shift, the so-called diffraction orders are created along the direction of light propagation. Diffraction orders are identified by an integer "m".Order 0 corresponds to the light refracted by the base refracting surface onto which the diffractive structure has been superimposed, while subsequent orders correspond to the diffracted orders generated by the semi-periodic Fresnel structure. Those orders that concentrate the greatest proportion of light energy establish the main focal points. The percentage of light distributed at each focal point, known as the energy efficiency distribution, depends on the shape of the etched profile in each zone and the phase shift introduced between them.

[0006] Furthermore, since the phase shift varies with wavelength, the energy distribution is also influenced by the spectral composition of the incident light. This is particularly important because human vision develops under polychromatic lighting conditions, and the variation in power with wavelength generates longitudinal chromatic aberration (LCA). In particular, the LCA in positive diffractive orders behaves in the opposite way to that of refractive elements, allowing the integration of a diffractive element with a refractive one to result in the +1 order LCA being compensated while the -1 order LCA is added.

[0007] Multifocal IOLs, designed to meet the growing need for near vision, must generate at least three focal points to enable distance (DV), intermediate (VI), and near (VP) vision. Throughout the technological evolution in this field, various strategies have been implemented to achieve trifocality, combining refractive and diffractive designs, or using macro-profiles that incorporate kinoform or sinusoidal diffractive structures. Kinoform profiles exhibit a sawtooth relief with discontinuities that generate finite phase shifts between pentodes and lack symmetry with respect to their zero diffractive order. In particular, this design allows 100% of the energy to be concentrated at the order m = +1 when the phase shift is 2TT.Multifocality appears with phase jumps other than 2TT, making it possible to distribute energy asymmetrically between two orders m = ± 1, using for example only m = 0 and m = + 1.

[0008] Examples of designs that have used this technique can be found in patents EP2503962(B1) (Houbrechts et al., 2012), EP1982229(B1) (X. Zhang et al., 2008), EP3731782(B1) (Kontur et al., 2022), and US8678583(B2) (Cohen, 2012). The profiles described in these patents allow for trifocal performance by amplifying the diffractive orders (m = +0) (distance vision), (m = +1) (intermediate vision), and (m = +2) (near vision). However, their application faces the drawback that orders higher than (m = +1) often exhibit reduced image quality. Although the combination of a diffractive element with a refractive one can partially mitigate the LCA in the order (m = +1), this aberration tends to compromise the quality of the retinal image, with a more significant degradation in the higher orders am = +1.

[0009] As a solution, the trend has been to optimize designs to take advantage of the lowest diffraction orders, prioritizing, whenever possible, positive diffractive orders.

[0010] An example of a trifocal diffraction profile that uses the lowest diffraction orders is one whose relief behaves like a sinusoidal curve. In a trifocal sinusoidal lens, the -1 order is used for VL, the 0 order for VI, and the +1 order for VP. Theoretically, a sinusoidal diffraction profile with a given amplitude or phase shift between adjacent zones can distribute the energy equally among its three principal foci of lowest order (m = 0 and m = ±1).

[0011] However, for applications in the human eye, a good diffractive design does not necessarily require an equal distribution of energy among the three foci. Unfortunately, due to symmetry, a sinusoidal diffractive profile does not allow for an asymmetrical distribution of energy among its foci with respect to the zero-order foci. In other words, the energy of the +1 order (VP) must always be equal to the energy of the -1 order (VL). This condition limits the possibility of redirecting more energy to the intermediate focus without compromising the efficiency of the VL and VP foci.

[0012] However, even if the phase shift of the profile is modified to increase the efficiency of the m = -1 order, which is most affected by the LCA, this generates several drawbacks. On the one hand, the efficiency of the m = +1 order is unnecessarily improved, which does not require an increase in image quality since its LCA is compensated. On the other hand, this strategy significantly reduces the efficiency of the m = 0 order corresponding to the VI, compromising its performance by prioritizing the m = -1 order. Additionally, it is considered useful to be able to modify the behavior of a diffractive lens in a controlled manner for different ambient lighting conditions. One technique used to modify the efficiency profile of these lenses is the apodization of the phase shift of the diffractive profile, which allows, to some extent, adjustment of the energy distribution according to pupillary dynamics, thus improving visual performance under different lighting conditions.Examples of designs that have used this technique can be found in patents EP2396683(B1) (Schwiegerling, 2020), EP2503962(B1) (Houbrechts et al., 2013), US8678583(B2) (Cohen, 2014), and EP0888564(B1) (Lee & Simpson, 2002). However, a fundamental limitation of apodization is its inability to independently alter the energy distribution among the different diffraction orders in a manner different from the profile being apodized. Apodization does not allow for increased efficiency at the intermediate vision focus of a sinusoidal profile (m = 0 and m = ± 1) without symmetrically affecting the far and near vision foci (m = -1 and m = +1, respectively). SUMMARY OF THE INVENTION.

[0013] The present invention addresses the aforementioned problems by means of a multifocal intraocular lens that provides at least three focal points, where the energy efficiency of each point varies independently with respect to the pupil diameter. This eliminates the need for apodization.

[0014] The inventors have observed that it is possible to design a trifocal optical element more advantageously than is possible with a sinusoidal or kinoform profile. They propose implementing a profile that evolves parametrically from a central sinusoidal diffractive profile to a peripheral kinoform profile, or vice versa.

[0015] In this way, an energy distribution of the diffractive orders (-1, 0, and +1) can be obtained independently of each other as the pupillary aperture diameter changes. This improves trifocal performance across the entire pupillary aperture range, and particularly in VL and VI, compared to the sinusoidal solutions of the previous state of the art, which can be highly valued in clinical practice.

[0016] The present invention relates to an intraocular lens comprising an anterior and a posterior optical surface, where at least one of the anterior or posterior surfaces incorporates a diffractive profile. A characteristic of the invention is that the diffractive profile includes phase-change elements whose morphology evolves individually from the central axis to the periphery of the lens in order to produce a radial and independent variation in the energy efficiencies of the diffractive orders. This design strategy allows, compared to profiles employing orders of -1, 0, and +1, such as sinusoidal profiles, an improvement in the performance of the visual field focus without simultaneously and reflexively improving the near field focus. This ultimately allows for an improvement in the efficiency of the left anterior chamber focus.

[0017] The diffractive profile corresponds to an evolution from the center to the periphery of the optical zone or vice versa, from a first sinusoidal diffractive profile to a kinoform diffractive profile in which:

[0018] The first diffractive profile is sinusoidal, with a diffractive order of -1 corresponding to distance vision, 0 to intermediate vision, and a positive first diffractive order of +1 corresponding to near vision. The second diffractive profile is kinoform, with a negative first diffractive order corresponding to distance vision and a zero order corresponding to the intermediate vision of the first profile.

[0019] A preferred embodiment of the invention relates to a multifocal optic in which the phase shift of the diffractive profile is the same across the entire optical surface. Another possible embodiment relates to a diffractive profile whose phase shift evolves from the central axis of the lens to the periphery of the optical surface to achieve performance appropriate to the available pupillary dynamics.

[0020] One possible realization refers to a multifocal optic in which the diffractive profile covers the entire optical surface.

[0021] BRIEF DESCRIPTION OF THE FIGURES

[0022] To better understand the present disclosure, a series of figures are presented with an explanatory, but not limiting, character of the invention.

[0023] • FIG 1. is a front view of a manufactured lens showing the basic elements of the present invention.

[0024] • FIG 2A is a graphical representation of the diffractive phase variation profile versus the square of the radial distance with respect to the optical axis of a conventional multifocal lens composed of a sinusoidal profile with a single phase jump covering the entire optical surface.

[0025] • FIG 2B is a cross-sectional view of the lens in FIG 1 where the diffractive profile shown in FIG 2A is schematically and exaggeratedly represented along the radial direction of the base refracting surface.

[0026] • FIG 3A is a graphical representation of the diffractive phase variation profile versus the square of the radial distance with respect to the optical axis of the lens described in the invention according to certain embodiments.

[0027] • FIG 3B is a cross-sectional view of the lens in FIG 1 where the diffractive profile shown in FIG 3A is schematically and exaggeratedly represented along the radial direction of the base refracting surface according to certain forms of realization.

[0028] • FIG 4 is a graphical representation of the diffractive phase variation profile versus the square of the radial distance with respect to the optical axis of the lens described in FIG 2 compared with the lens described in FIG 3. • FIG 5 is a graphical representation of the diffractive phase variation profile versus the square of the radial distance with respect to the optical axis according to certain embodiments of the present invention having a phase amplitude that varies with the radius.

[0029] • FIG. 6 shows the modulation transfer function (MTF) as a function of object vergence and a spatial frequency of 50 lines / mm, of the lens in FIG 2 whose diffractive profile has a phase shift of 0.9, considering apertures of different diameters, i.e., different pupil sizes.

[0030] • Figures 7 to 9 show the MTF curves corresponding to the diffractive profiles presented in Figure 2 with a phase shift of 1.2 compared with the present invention presented in Figure 3, as a function of object vergence, at a spatial frequency of 50 lines / mm, considering apertures of different diameters, i.e., different pupil sizes.

[0031] • Figures 10 to 13 show the MTF curves corresponding to the diffractive profile presented in Figure 2 with a phase shift of 1.2, as a function of object vergence, at a spatial frequency of 50 lines 1 mm, considering apertures of different diameters, i.e., different pupil sizes, compared with another embodiment of the present invention presented in Figure 5.

[0032] DETAILED DESCRIPTION

[0033] In accordance with the schematic figures mentioned above, some examples of possible embodiments of the present invention will be detailed. These descriptions do not limit the invention, which may include various structural and dimensional features without departing from the scope according to the claims. The present invention relates to an intraocular lens. Figure 1 illustrates an embodiment of the invention in which the lens is intraocular (100) and has a diffractive surface profile (101). It includes an optical body (102) composed of a refractive base (106) that can adopt a combination of spherical, aspherical, and / or toric geometries in order to compensate for optical aberrations and / or astigmatism. The refractive base (106) has an anterior face centered on an optical axis (103). Over the posterior face, and covering its entirety, a diffractive profile (101) is superimposed to produce focused vision at near, intermediate and far distances.Thus, the zero diffractive order is determined by the refraction of the lens base curve. Although the diffractive surface profile (101) described above is shown and described as being located on the anterior surface of the optic, the present invention contemplates that it may additionally or alternatively be located on the posterior surface of the optic. The intraocular lens (100) may include a plurality of haptics (104) to stabilize the position of the lens within the eye of a patient.

[0034] The intraocular lens (100) described above can be manufactured using various techniques and materials. For example, the optical body (102) can be formed from an optically transparent and biocompatible material for the intended purpose. Some suitable materials are, without limitation, PMMA, silicone, or acrylic polymers, which are appropriate for IOLs. The haptics (104) of an intraocular lens (100) can be manufactured as an integral unit or formed separately and assembled using techniques known in the prior art.

[0035] Figure 2A illustrates a graphical representation of the diffractive phase variation profile versus the square of the radial distance with respect to the optical axis of a sinusoidal diffractive profile (105) whose phase shift is constant along the radial coordinate. For clarity, the phase corresponding to the refractive base curve (106) of the lens has not been shown. Figure 2B illustrates a cross-sectional view of the lens whose diffractive phase variation profile has been described in Figure 2A. For illustrative purposes, the amplitude of the diffractive profile (105) superimposed on the refractive base curve (106) of the lens has been exaggerated.

[0036] The present invention relates to an intraocular lens with a diffractive profile (101) in which each diffractive zone (101, 20n) has a geometry and phase shift that varies progressively from the first zone (101, 201), located near the center of the anterior or posterior surface of the lens, to the last zone (101, 215), near the periphery. The morphological evolution of the function of each diffractive zone (101, 20n) is determined by a specific rate of variation (107), such that a reduced rate of variation results in greater geometric similarity of the intermediate zones to the first diffractive zone (101, 201), while a high rate of variation induces greater morphological convergence towards the last zone (101, 215). The modification of the shape of the zones allows the incident light power to be distributed asymmetrically among the diffractive orders, as the diameter of the pupillary aperture increases.

[0037] In a particular embodiment, illustrated in FIGURE 3A, the phase variation profile of the diffractive pattern (101) is shown graphically. The first diffractive zone (101, 201) follows a sinusoidal function, while the last zone (101, 215) is defined by a kinoform function of constant amplitude along the profile. Thus, the diffractive pattern evolves from a sinusoidal shape at the center to a kinoform shape towards the periphery. FIGURE 3B schematically shows the diffractive profile (101), in which, for illustrative purposes, the dimensions of the diffractive structures on the refractive baseline curve (106) have been exaggerated.

[0038] FIGURE 4 compares the phase variation profile described in a particular embodiment of the invention shown in FIGURE 3 with a conventional sinusoidal morphology profile (105) shown in FIGURE 2. As can be seen, the sinusoidal morphology gradually changes from the central axis, transforming as the radial coordinate increases towards the periphery, until it adopts a morphology characteristic of a kinoform pattern.

[0039] In an advantageous embodiment, FIGURE 5 graphically shows the phase variation profile of the diffractive design (101) of the intraocular lens, where the phase jump of the diffractive zones (101', 20n') varies from the center to the periphery of the lens from an initial value (108) to a final value (109).

[0040] Figure 6 illustrates the MTF as a function of the lens's object vergence with the sinusoidal diffractive profile with a phase-step of 0.9, described in Figure 2, evaluated at a spatial frequency of 50 lines / mm. The different curves represent the MTF for apertures with different diameters. With a pupillary aperture diameter of 4.5 mm, the sinusoidal profile, represented by the dotted curve, exhibits equienergetic trifocal behavior in the orders of -1, 0, and +1, unlike the other pupillary apertures. In Figures... 7 and 8 compare the MTF curves (110) associated with the sinusoidal diffractive profile with a phase shift of 1.2 (105) with the MTF curves (111) associated with the profile described in the present invention in one of its embodiments (101, 20n) for an aperture diameter of 4.5 mm and 3 mm, respectively.It is observed that, even when modulated with a different phase shift, the sinusoidal diffractive profile does not improve the MTF value at the order of m = -1, associated with distance vision. However, the profile according to the proposed implementation does increase this value. Furthermore, it offers a higher MTF value at the order of m = 0, corresponding to visual acuity.

[0041] Figure 9 shows the MTF curves (110) associated with the sinusoidal diffractive profile with a phase shift of 1.2 (105) compared with the MTF curves (111) associated with the profile described in the present invention in one of its embodiments (101,20) for an aperture diameter of 2 mm. It can be seen that, with the sinusoidal profile, the order m = 0 practically disappears as its energy disperses towards higher orders am = ±1, which eliminates the VL. In contrast, the profile described in the invention not only maintains trifocal behavior for reduced apertures, but also achieves higher MTF values ​​in the orders m = -1 and m = 0 compared with the sinusoidal profile. Furthermore, unlike what is observed in Figures 7 and 8, even the order m = +1, corresponding to the VP, reaches the value provided by the sinusoidal profile. In Figures 7 and 8, the MTF curves (111) are also higher. 10 and 11 compare the MTF (110) curves associated with the sinusoidal diffractive profile with a phase jump of 1.2 (105) with the MTF curves (11 T) associated with the profile described in the present invention in an alternative embodiment described in FIG 5 (10T, 20n') for an aperture diameter of 4.5 mm and 3 mm, respectively. The variation in the modulation of the profile of the invention along the radial coordinate provides a different behavior for pupils of diameter 4.5 mm where the VI increases with respect to smaller aperture diameters.

[0042] Although certain embodiments have been illustrated and described in this document, those skilled in the art will recognize that they can be replaced by various alternative implementations or variants that achieve the same objectives without departing from the scope of the present invention. This document is intended to encompass any adaptation or variation of the embodiments discussed herein. Furthermore, the terms and expressions used in this specification are for descriptive and non-limiting purposes. Their use is not intended to exclude equivalents of the features shown and described, or parts thereof, it being recognized that the scope of the invention is defined and limited exclusively by the claims.

Claims

CLAIMS 1. A trifocal intraocular lens (100) comprising a body with an optical part (102) and a periphery separated by an optical boundary, wherein the optical part (102) is composed of a refractive base (106) having an anterior and a posterior face centered on an optical axis (103), wherein at least one of the faces is provided with a diffractive profile (101) superimposed on the refractive base (106) to produce focused vision at near, intermediate and far distances, and wherein the diffractive profile evolves from a sinusoidal shape in the center to a kinoform shape towards the periphery, such that the zero diffractive order is determined by the refractive base, characterized in that the diffractive profile (101) distributes the incident light to the zero order, a first negative order and a first positive order,The refractive base combined with the first positive order of the diffractive element is adapted to focus the incident light on the lens for near vision, the refractive element is adapted to focus the incident light on the lens for intermediate vision, and the refractive element combined with the first negative order of the diffractive element is adapted to focus the incident light on the lens for distance vision.

2. The lens of claim 1, characterized in that the diffractive profile (101) is circularly symmetric and comprises a plurality of periodic zones whose geometry varies radially from the optical axis (103) to the limit of the diffractive profile to radially modulate the phase of the incident optical field.

3. The lens of any of claims 1 and 2, characterized in that said diffractive profile (101') has a distribution of the energy efficiencies of the three principal diffractive orders that change radially from the optical axis (103) to the limit of the diffractive profile.

4. The lens of any of claims 1-3, characterized in that the amplitude of the diffractive profile (101') varies radially from an initial value (108) on the axis of symmetry (103) to a final value (109) at the optical limit of the lens.

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