WO2018055073A1 - Intraocular lens with an extended depth of focus - Google Patents

Abstract

An intraocular lens designed to be mounted in an eye, said lens comprising at least one rear face designed to be directed towards the retina and one front face designed to be turned towards the cornea. The front face comprises at least one front optical surface comprising first asphericities that define a through-focus modulation transfer function (FTM₁₁), for a spatial frequency of 30 cycles per millimetre, which is asymmetrical. The rear face comprises at least one rear optical surface comprising second asphericities defining a through-focus modulation transfer function (FTM₁₂), for a spatial frequency of 30 cycles per millimetre, which is asymmetrical and opposite that of the front optical surface such that the lens has an extended depth of focus.

Description

 INTRAOCULAR LENS WITH EXTENDED FIELD DEPTH

TECHNICAL FIELD AND PRIOR ART The present invention relates to the field of optics, in particular an intraocular lens used during a cataract surgery.

In known manner, an eye has a lens that fulfills a convergent lens function inside the eye. Cataract is a pathology that opacifies the lens partially or totally, which can lead to a gradual decline in vision. In order to improve the view of patients with cataracts, it is known to perform a surgical operation during which the surgeon performs ablation of the opacified lens after section of the cornea and opening of the lens capsule. Such a cataract operation is followed by the establishment, simultaneous or subsequent, of an intraocular implant intended to replace the opaque lens.

It is known that such an intraocular implant generally comprises, on the one hand, a central lens and, on the other hand, fastening means preferably made in the form of elastically deformable arms and connected by one of their ends to the outer periphery of said central lens. These arms are intended for positioning and fixing the intraocular implant so as to make the latter integral with the eye.

In practice, it is very difficult to obtain precise positioning since the latter depends on the anatomical configuration of the eye. In addition, an intraocular implant placed in the capsular sac of an operated eye of the cataract undergoes cicatricial contractions of said capsular bag, when the latter has a postoperative cicatricial fibrosis. Such scarring contractions can cause displacement of the intraocular implant in the capsular bag. In practice, following a cataract operation, there remains a postoperative refractive error of at least about +/- 0.5 diopter, which usually forces a patient to use a pair of glasses.

By way of example, the physical parameters of an example of conventional monofocal lens according to the prior art, comprising a front optical surface and a rear optical surface, are represented below. Radius (mm) Thickness Refractive Index Diameter Conical

 (Mm)

 Front optical surface 10,734 0,973 1, 46 3 -1, 1 19

 Rear optical surface -14,291 -1, 1 19

With reference to FIG. 1, a continuous line represents the modulation transfer function as a function of the FTMA focusing error, better known to those skilled in the art under its English designation Through Focus MTF for "Through Focus Modulation". Transfer Function ", the classic monofocal intraocular lens in a standard eye, which offers a good quality of vision in the focal plane but a degraded vision for a refractive error greater than +/- 0.3D (for 50 cycles per millimeter).

There is also known an optics extended depth of field, sometimes called by the skilled person under the English designation EDOF for "Extended Depth Of Focus". In contrast to a monofocal lens, an EDOF lens offers a compromise between a slightly poorer image quality in the focal plane but greater than that afforded by a conventional monofocal lens over a larger defocus range. The EDOF lenses proposed until today do not adequately solve the problem of residual refractive error because they are designed to solve the problem of loss of accommodation.

The patent application WO201 2/0371 54 discloses a method for increasing the depth of field by performing a wavefront encoding. The patent application WO201 4/1 35986 proposes to use cubic or "lenticular" phases for the lens in order to increase the depth of field. The patent application US201 2/1 581 31 defines a multizone profile for a lens (symmetrical zones, aspherical zones). The patent application US201 2/1 47321 relates to unsymmetrical lenses. Finally, patent application US2004 / 230299 teaches modulating the optical surface, in particular by means of a polynomial. The object of the invention is to remedy at least some of these drawbacks, in particular that of the residual refractive error, by proposing an intraocular lens. allowing to offer a good quality of vision for an extended depth of field, ie, for a refractive error superior or equal to +/- 0,5D.

GENERAL PRESENTATION OF THE INVENTION

To this end, the invention relates to an intraocular lens adapted to be mounted in an eye, said lens having at least one rear face adapted to be directed towards the retina and a front face adapted to be turned towards the cornea. The invention is remarkable in that the front face comprises at least one front optical surface comprising first aspherities defining a modulation transfer function as a function of the focusing error, for a spatial frequency of 30 cycles per millimeter, which is asymmetrical, and in that the rear face comprises at least one rear optical surface having second aspherities defining a modulation transfer function as a function of the focusing error, for a spatial frequency of 30 cycles per millimeter, which is asymmetrical and opposite to that of the forward optical surface so that the lens has an extended depth of field. The presence of asphericity leads to the formation of optical aberrations which are generally avoided. Thanks to the invention, advantage is taken of optical aberrations to obtain two modulation transfer functions, as a function of the focusing error, asymmetrical in order to form a lens whose overall modulation transfer function, as a function of the focusing error, has an extended depth of field for a spatial frequency of 10 to 100 cycles per millimeter.

The modulation transfer functions are presented at a spatial frequency of 30 cycles per millimeter but they could also be presented for frequencies of 10 to 100 cycles per millimeter.

Advantageously, the optical aberrations combine to increase the depth of field. The combination of optical aberrations is, for example, discussed in Michael P. eating's book "Geometry, Physical, and Visual Optics" (Elsevier Health Sciences, June 6, 1988) (page 547) and "Optics and Lasers: Including Fibers". and Optical Waveguides "by Matt Young (Springer, June 29, 2013) (page 144). Preferably, the front face comprises a single front optical surface. More preferably, the rear face comprises a single rear optical surface. According to one aspect of the invention, the lens defines an overall modulation transfer function, at a spatial frequency of 50 cycles per millimeter, as a function of the focusing error, whose minimum value is greater than 0.2 and whose the maximum value is greater than 0.3 for a refractive error of ± 0.5 diopters. Preferably, the lens defines a global modulation transfer function, at a spatial frequency of 50 cycles per millimeter, as a function of the focusing error, the minimum value of which is greater than 0.1 and the maximum value of which is greater than 0.2 for a refractive error of ± 0.75 diopter This value is defined for the position of best focus when the lens is placed in a model eye as described in ISO 1 1979-2: 1999 (F ).

Preferably, each modulation transfer function depending on the focusing error, having a low inclination slope and a steep inclination slope, the low inclination slopes have opposite inclinations. Preferably, the slopes of low inclination are opposite one another. Thus, the optical aberrations associated with each modulation transfer function as a function of the focusing error compensate / combine to define a global modulation transfer function with a greater depth of field.

According to a preferred aspect, the first aspherities of the front optical surface comprise asphericity coefficients of order greater than 2. Preferably, the first aspherities of the front optical surface comprise only evenly ordered asphericity coefficients. to simplify manufacturing and not to cause astigmatism. In a preferred manner, the first aspherifiers of the front optical surface and the second aspherities of the rear optical surface have ashericity coefficients of the same sign, their absolute values being identical or different. According to one aspect, the aspherities comprise coefficients of asphericity of order 4, 6 or 8 preferably comprised (in absolute value) between 0.00005 and 0.05.

The invention also relates to an intraocular implant comprising a lens as presented above and elastically deformable fixing means and connected to said lens.

The invention more particularly relates to a monofocal lens.

According to another aspect of the invention, the invention relates to a toric lens for the correction, in particular, of astigmatism.

The invention also applies to a contact lens comprising at least one front face adapted to be directed towards the outside and a rear face adapted to be turned towards the eye. The front face comprises at least one front optical surface having first aspherities defining a modulation transfer function as a function of the focusing error, for a spatial frequency of 30 cycles per millimeter, which is asymmetrical, and in that the front face backplane comprises at least one rear optical surface having second aspherities defining a modulation transfer function as a function of the focusing error, for a spatial frequency of 30 cycles per millimeter, which is asymmetrical and opposite to that of the front optical surface so that the lens has an extended depth of field.

PRESENTATION OF FIGURES

The invention will be better understood on reading the description which will follow, given solely by way of example, and referring to the appended drawings in which:

FIG. 1 is a schematic representation of a modulation transfer function as a function of the focusing error for a monofocal lens. of the prior art and a lens according to the invention for a spatial frequency of 50 cycles per millimeter;

 Figure 2 is a sectional view of an embodiment of a lens according to the invention; and

 FIG. 3 represents, on the one hand, the modulation transfer function as a function of the focusing error at 30 cycles per mm, of a front optical surface, and, on the other hand, the modulation transfer function as a function the focusing error at 30 cycles per mm, of a rear optical surface. It should be noted that the figures disclose the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate.

DESCRIPTION OF ONE OR MORE MODES OF REALIZATION AND IMPLEMENTATION

There will be presented a monofocal intraocular lens 1 according to one embodiment of the invention. The monofocal intraocular lens 1 is adapted to be mounted in an eye, particularly in the capsular bag of an eye during a cataract operation. As will be presented later, the invention applies to other lenses than monofocal lenses.

As illustrated in FIG. 2, the monofocal intraocular lens 1 has a rear face 1B adapted to be directed towards the retina of the eye and a front face 1A adapted to be turned towards the cornea of the eye. Such a lens 1 is refractive and can be used in a cataract operation.

In this embodiment, with reference to FIG. 2, the front face 1 A comprises a single optical surface before 11 while the rear face 1 B comprises a single rear optical surface 12. According to the invention, the front optical surface 1 1 comprises first aspherities while the rear optical surface 12 comprises second aspherities.

In known manner, an optical surface with aspherities generates optical aberrations. An optical aberration, known to those skilled in the art, is defined with respect to the paraxial optics and materializes the fact that all the rays coming from of the same object point do not converge towards the same image point. In the field of intraocular lenses, optical aberrations are generally minimized to improve the patient's vision quality. According to the invention, optical aberrations are advantageously used to form a monofocal lens 1 whose depth of field is increased. Such an approach involves an inventive step because it goes against a strong technical bias and recognized vis-à-vis the use of optical aberrations for an imaging system. For example, computer aided design tools for intraocular lenses are designed to help limit optical aberrations and promote the design of intraocular lenses having rotational symmetry. In a known manner, asphericity is a parameter of the sagitta equation of the optical surface. Preferably, asphericity coefficients of order greater than 2 are used to increase the depth of field as will be presented later. In known manner, the equation of sagitta is described by the following equation: l + Jl - (l + k) c ² r ² in which

 - z is sagitta

 - r is a radial coordinate

 - c is the inverse of the radius of curvature

 - k is the conical constant

- ai is a term of higher order asphericity. According to the invention, the first aspherities of the optical surface before 1 1 define a function of modulation transfer as a function of the focusing error, for a spatial frequency of 30 cycles per millimeter, asymmetric while the second aspherities of the surface rear optics 12 define a function of modulation transfer according to the focusing error, for a spatial frequency of 30 cycles per millimeter, asymmetrical and opposite to that of the optical surface before 1 1 so that the lens 1 has an extended depth of field. In other words, the front and rear surfaces cause aberrations that combine to increase the depth of field. The modulation transfer function, as a function of the focusing error, is known to those skilled in the art under the English name "through focus MTF". As a reminder, the FTM modulation transfer function is the module of the optical transfer function.

By way of example, with reference to FIG. 3, modulation transfer functions are shown as a function of the FTM n, FTM12 focusing error of the optical surfaces 1 1, 1 2. Each modulation transfer function in FIG. FTMn, FTM 12, focusing error function defines a steep slope and a low inclination slope. Advantageously, by parameterizing the aspherities, the slopes of the modulation transfer function FTMn, FTM 12 are adapted, which makes it possible to obtain a lens whose overall depth of field can be adapted in a practical manner.

Aspherentials are defined such that the aberrations associated with asymmetric FTMn, FTM12 modulation transfer functions combine to increase the depth of field compared to a conventional intraocular lens. With reference to FIG. 1, the overall modulation transfer function as a function of the FTMB focusing error of the lens 1, has an increased depth of field compared to a lens 1 according to the prior art. Preferably, the maximum value of the overall modulation transfer function as a function of the FTMB focusing error is greater than 0.2 (for 50 cycles / mm), preferably greater than 0.28 (for 1 00 cycles / mm) so as to obtain a good quality of vision when the refractive error is between -0.50D and +0.50D, preferably between -0.75D and +0.75D.

The asphericity of the two optical surfaces 1 1, 1 2 may be identical or different (in absolute value), the important thing being that overall the aspherities define modulation transfer functions as a function of the focusing error FTM n, FTM 12 asymmetrical. Preferably, the aspherities comprise only even order coefficients. Preferably, the aspherities comprise asperity coefficients of order 4 (in absolute value) of between 0.0001 and 0.05. Preferably, the aspherities comprise asperity coefficients of order 6 (in absolute value) of between 0.00005 and 0.05. By way of example, the physical parameters of an example of a monofocal lens 1 according to the invention are shown below.

With reference to FIG. 3, the modulation transfer functions as a function of the focusing error FTMn, FTM 12 resulting respectively from optical surfaces 1 1, 1 2 having 4-fold asphericity terms are represented. and 8 of the sagitta equation of optical surfaces.

The modulation function as a function of the focusing error FTM n respectively corresponds to the modulation function of a lens comprising the front optical surface 11 and a flat rear optical surface. The FTM modulation function 12 is similarly defined.

Due to the combination of optical aberrations, the monofocal lens 1 has a global modulation function as a function of the extended FTMB focusing error compared to a modulation function according to the prior art FTMA focusing error. as shown in Figure 1.

By imposing aspheric coefficients defining optical surfaces 1 1, 1 2 for 30 cycles per mm, the optical surfaces will focus the light in a combined manner to obtain a lens with extended depth of field. Advantageously, the global modulation function as a function of the FTMB focusing error obtained is substantially symmetrical on both sides of the best focus position. Advantageously, the optical surfaces 1 1, 1 2 are determined independently so as to obtain an overall modulation function as a function of the optimal FTMB focusing error. Such a construction goes against the computer-aided design tools, which is evidence of inventive activity.

Also, the asphericity coefficients may have high values (> 0.001) which correspond to surface variations that are simpler to achieve in practice than those corresponding to low values. Preferably, such surface variations can be achieved by means of conventional industrial equipment.

Advantageously, the asphericity coefficients of order greater than 2 make it possible to modify the curvature of an optical surface 11, 12, in particular at the periphery, and thus to better control the resulting spherical aberrations.

It has been presented a front face 1 A having a single optical surface 1 1 but it goes without saying that it could include a different number, for example, two. The same goes for the rear panel 1 B.

It has been presented a monofocal intraocular lens 1 but it goes without saying that the invention applies to other types of lenses, in particular, a so-called "toric" lens at least one of the optical surfaces is toric.

It has been presented an intraocular lens 1 as such, but it goes without saying that the invention also applies to an intraocular implant comprising an intraocular lens 1 and fastening means or support, in particular, deformable arms.

Claims

1. Intraocular lens (1) adapted to be mounted in an eye, said lens (1) having at least one rear face (1B) adapted to be directed towards the retina and a front face (1A) adapted to be turned towards the horny, lens characterized by the fact that  the front face (1A) comprises at least one front optical surface (11) comprising first aspherities defining a modulation transfer function as a function of the focusing error (FTMn), for a spatial frequency of 30 cycles per millimeter, which is asymmetrical, and that  the rear face (1B) comprises at least one rear optical surface (12) comprising second aspherities defining a modulation transfer function as a function of the focusing error (FTM12), for a spatial frequency of 30 cycles per millimeter, which is asymmetrical and opposite to that of the front optical surface (11) so that the lens (1) has an extended depth of field. 2. Intraocular lens (1) according to claim 1, wherein the front face (1A) comprises a single front optical surface (11). 3. Intraocular lens (1) according to one of claims 1 to 2, wherein the rear face (1 B) comprises a single rear optical surface (12). 4. Intraocular lens (1) according to one of claims 1 to 3, wherein the modulation transfer function as a function of the focusing error (FTMn, FTM12) define a global modulation transfer function according to the focusing error (FTMB), at a spatial frequency of 50 cycles per millimeter, the minimum value of which is greater than 0.2 for a refractive error of ± 0.5 diopters. Intraocular lens (1) according to one of claims 1 to 4, wherein each function of modulation transfer according to the focusing error (FTMn, FTM12) having a low inclination slope and a steep inclination slope. slopes of low inclinations have opposite inclinations. 6. Intraocular lens (1) according to claim 5, wherein the slopes of low inclination are opposite one another. 7. Intraocular lens (1) according to one of claims 1 to 6, wherein the first asphericity of the front optical surface (1 1) comprise coefficients of asphericity of order greater than 2. 8. Intraocular lens (1) according to one of claims 1 to 7, wherein the first asphericity of the front optical surface (1 1) comprise only asparagus coefficients of even order. 9. Intraocular lens (1) according to one of claims 1 to 8, wherein the first asphericity of the front optical surface (1 1) and the second asphericity of the rear optical surface (12) have coefficients of asphericity of same sign. 10. Intraocular lens (1) according to one of claims 1 to 9 wherein at least one of the optical surfaces is toric. 1. Intraocular implant comprising a lens (1) according to one of the preceding claims and elastically deformable fixing means and connected to said lens (1).