DIFFRACTIVE EYE IMPLANT WITH ENLARGED NEAR VISION

Description

FIELD OF THE INVENTION

[0001] The present invention lies in the field of ocular implants.

[0002] Its particular purpose is a diffractive ocular implant with extended near vision. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] A cataract is the loss of transparency of the natural lens. The natural lens contributes one-third of the light reaching the eye. Cataract surgery involves removing the natural lens to restore clear vision. In the 1950s, Dr. Ridley implanted the first intraocular lenses in the sulcus to correct aphakia and thus restore one-third of the missing optical power. Intraocular lenses are now implanted in the capsular bag.

[0004] Without accommodation (at rest), objects located at a far distance are focused (sharp) on the retina of an emmetropic eye (neither myopic, nor hyperopic, nor astigmatic).

[0005] To clearly visualize close objects (from intermediate to near distance) the young natural lens has the ability to deform. Thus, under the action of the ciliary muscles which relax the zonular fibers by contracting, the anterior and posterior radii of curvature of the natural lens increase its optical power by several diopters.

[0006] The loss of this accommodation comes with age and appears in all cases after cataract surgery during which the natural lens is replaced by an artificial lens that does not have the capacity to modify its power according to the desired viewing distance.

[0007] Some so-called accommodative implants (deformable polymers, mobile optics) attempt to restore accommodation, but the results are not satisfactory today (partly because of fibrosis of the capsular bag which, over time, blocks the possibilities of deformation).

[0008] To compensate for this loss of accommodation, many multifocal implants have been developed. They are based on the division of light energy into several vision zones. In the early 2000s, diffractive optics demonstrated their superiority in distance and near vision compared to refractive optics.

[0009] Diffractive optics allow for a wide range of diffraction energy distribution choices depending on the chosen viewing distances. The optical quality resulting from the chosen profile is defined by its MTF (modulation transfer function).

[0010] The MTF is a number between 0 and 1 (or 0% and 100%) that represents the contrast of the image (the image may be non-contrasted because it is defocused or because the energy is shared between several foci). The MTF "through focus", abbreviated to MTF-TF, represents the MTF as a function of defocus (which is represented either as a function of viewing distance or as a function of addition (1D=1 / 1m)). The MTF-TF is used to determine the depth of field.

[0011] It has been shown in the literature that regardless of the optical profile or technology, visual outcomes are related to the MTF profile of the implanted IOL (acronym for intraocular lens or implant). Thus, on average, binocular visual acuity is better than: 0 LogMAR (10 / 10) when the MTF is 0.40; between 0 and 0.05 LogMAR (9 / 10) for an MTF of 0.20; 0.1 LogMAR (8 / 10) for an MTF of 0.15, when the MTF is at 3 mm and 50 cycles / mm, MAR meaning "Minimum Angle Resolution".

[0012] The first diffractive optics were bifocal optics with a peak MTF for distance vision (0D addition) and another peak for near vision (+3D or +4D addition). These implants allow clear vision for reading (around 40 cm) but patients must wear a correction for intermediate vision (between 40 and 90 cm).

[0013] In order to get closer to ideal vision (without glasses correction), with clear and continuous vision at all near vision distances (from 40 to 90 cm), several solutions have been developed: the “Mix & Match”; the “EDOF”; the trifocal implants. The "Mix & Match":

[0014] Mix and Match involves using two bifocal implants with different additions for each eye (one eye for near vision, the other for intermediate vision).

[0015] The objective is to provide a contrasted image in intermediate vision, which is not the case with trifocal implants. The +1.75D / +4D and +1.5D / +3D combinations (additions in IOL plane) gave interesting "defocus" curves (i.e. visual acuity as a function of viewing distance). But the limit of this solution is the patient's binocular vision comfort. In order to preserve binocular balance, an addition difference of 0.5D was proposed and the +2.5D / +3D combination (additions in IOL plane) showed similar results to trifocals, except in the 1D and 1.5D zone (in corneal plane). EDOF (acronym for "extended depth of focus" or "extended depth of field"):

[0016] Extended depth of focus implants are bifocal (or sometimes trifocal) implants with lower additions to allow good intermediate vision. It should be noted that the lower the addition of an implant, the greater its depth of focus will be at distance because the addition is a "1 / x" function of the distance. These implants allow comfort for computer vision (intermediate vision), but it is necessary to wear corrective lenses for near vision. Trifocal implants:

[0017] Trifocal implants are diffractive "IOLs" whose energy is distributed into 3 vision peaks: distance, intermediate, and near. They therefore provide clear vision and intermediate vision where bifocal implants only provided clear near vision. Currently, trifocal implants are the most advanced "high-end" solution for achieving clear vision from infinity to near.

[0018] But trifocal implants have three distinct vision peaks with a contrast discontinuity, the MTF-TF, between near and intermediate vision. On some trifocal implants this discontinuity is visible on the MTF-TF at 50 cycles / mm, which represents intermediate letter sizes. Vision is therefore clear at 40 and 80 cm, but not at 60 cm.

[0019] On other implants, we find this discontinuity on the FTM-TF at 100 cycles / mm, that is to say for smaller letter sizes.

[0020] The prior art of interest with respect to the present invention consists of documents FR 3 072 020, US 2007 / 182921 and WO 03 / 107076.

[0021] The objective of the present invention is to overcome the drawbacks indicated above and to propose an intraocular implant which makes it possible to obtain clear and continuous vision over the entire useful near vision zone and requiring the deciphering of small characters (reading a book placed 40 cm from the reader, mobile phone, tablet, laptop placed 60 cm from the user, desktop computer placed 80 cm away, etc.). SUMMARY OF THE INVENTION

[0022] Thus, the present invention relates to a diffractive ocular implant according to claim 1.

[0023] Thanks to the invention, we gain depth of field in near vision, while maintaining good distance vision, without discontinuity up to spatial frequencies at 100 cycles / mm.

[0024] Other optional advantageous features of the invention are the subject of the dependent claims.

[0025] Throughout this application, the term "correct distance vision" means vision such that the MTF is greater than 20% at 50 cycles / mm on a 3 mm pupil.

[0026] As for the expression "extended near vision", its definition is given by the formulation "characterized by the fact that it presents a phase transfer curve as a function of the viewing distance (abbreviated PTF-TF) with an absence of discontinuity over a depth of field of at least 1.3D in the corneal plane, that is to say over a range of additions in the corneal plane of at least 1.3D, the addition in the corneal plane being understood as the inverse of the distance between the object seen and the cornea, advantageously greater than 1.45D". BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other features and advantages of the invention will become apparent upon reading the following description of embodiments of the invention. This description is made with reference to the appended drawings in which: there figure 1 is a FTM-TF curve of a commercial trifocal implant; the figure 2 is a commercial bifocal implant FTM-TF curve; the figure 3 is an FTM-TF curve of an implant according to the invention figure 4 is a view of a "half-profile" of an implant according to the invention, it being understood that in this figure, the variability of the scales represented is due to apodization; the Figure 5 is a view of a "half-profile" of an implant according to the invention, it being understood that in this figure, the variability of the scales represented is due to apodization; the figure 6 is an FTM-TF curve of an implant according to the invention; the figure 7 is an FTM-TF curve of an implant according to the invention; the figure 8is an FTM-TF curve of an implant according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] In the following and unless otherwise stated, the addition is indicated corneal plane. Concept of phase transfer function (PTF):

[0029] Any optical system can be represented by its "point spread function" (abbreviated "PSF").

[0030] The PSF represents the spatial distribution of light intensity in the image plane of an optical system, formed from a point source object. The more point-like the PSF, the better the optical quality. This PSF, which is in the spatial domain, is very important because converted into the frequency domain, it is then the "optical transfer function" (abbreviated "OTF") which makes it possible to simulate the image of any object seen through the optics of the system studied.

[0031] She expresses herself thus: OTF ω x ω y = ∫ ∫ − ∞ + ∞ PSF x y e i xω x + yω y dx dy = Re OTF ω x ω y + i Im OTF ω x ω y

[0032] Or ω x , ω yrepresent the spatial frequencies in Fourier space, x,y the spatial dimensions in real space and Re and Im the real and imaginary parts of a complex number, i being the square root of -1 in the space of complex numbers.

[0033] The modulation transfer function is the modulus of the optical transfer function, i.e., the square root of its real and imaginary parts to the power of 2.

[0034] She expresses herself thus: MTF ω x ω y = Re OTF ω x ω y 2 + Im OTF ω x ω y 2

[0035] The phase transfer function PTF is the argument of the optical transfer function. It is expressed as: OTF ω x ω y = MTF ω x ω y e − i PTF ω x ω y

[0036] To achieve seamless viewing comfort over a wide depth of field, it is useful to think in terms of "phase" and "phase inversion". Indeed, when the MTF-TF becomes zero after a peak and then presents a new peak, this often corresponds to a phase inversion, which means that for a given spatial frequency (100 / cycles / mm in the case of an MTF-TF curve at 100 / cycles / mm), the perceptible signal is inverted. Thus, for example, a black test pattern on a white background becomes white on a black background.

[0037] In the case of IOLs, phase inversion can occur at high frequencies but also depending on defocus. Thus, for commercial trifocal implants, between intermediate vision and near vision, the implant is no longer focused enough and there is phase inversion.

[0038] This is the case of the figure 1 in which we are dealing with a commercial trifocal implant.

[0039] In this figure, we find, on the abscissa, the addition (from O to 3D in the corneal plane) and on the ordinates the MTF (on the left) and the phase (on the right).

[0040] The following curves were drawn: curve A: MTF curve; curve B: real part of the OTF curve; curve C: imaginary part of the OTF curve; curve D: phase transfer curve.

[0041] Unless expressly stated, the figures below use the same parameters.

[0042] We actually observe a phase inversion around the 1.5D addition (in corneal plane). This implant therefore does not allow clear and continuous vision without phase inversion between intermediate vision and near vision. Definition of the parameters referred to in this application :

[0043] The FTM-TF curves (or TFFTM = "modulation transfer function through focus") represent the quality of the optics (in % - or ratio between 0 and 1-) of image contrast for an initial object having a contrast of 100%) as a function of the viewing distance (described in addition in Diopters: 0 D = distance vision / +1 to +2D = intermediate addition / 3 D = near addition in corneal plane).

[0044] These are curves simulated with optical simulation software such as the one known under the brand name Zemax for intraocular implants placed in an average eye model.

[0045] A FT-MF curve is established for a given spatial frequency. Usually, for multifocal implants, the FT-MF at 50 cycles / mm is of interest. FT-MFs at 25 cycles / mm (coarser objects) and 100 cycles / mm (finer objects) are also of interest.

[0046] A 50 cycles / mm (for example) FTM-TF curve of a given optical profile depends on the pupil of the optical system and the wavelength of the light used.

[0047] Thus, we are preferentially interested in a green wavelength (546nm) but it may also be interesting to plot the photopic MTF-TF corresponding to the integral of the wavelengths of daylight, as well as the scotopic MTF-TF (night vision).

[0048] Similarly, we are preferentially interested in a pupil of 3 mm in diameter (corresponding to well-lit vision (reading and day vision), but the continuity of FTM-TF can be interesting for pupils of 2 to 6 mm.

[0049] An MTF value greater than 0.15 is considered to provide satisfactory near vision to the wearer.

[0050] Near vision, VP, is typically +3D (corneal plane addition), but can be between +2D and +4D.

[0051] Intermediate vision, VI, is typically +1.5D (corneal plane addition), but can be between +1D and +2D. Implants according to the invention :

[0052] The constant phase extended near vision implants according to the invention can be defined as follows: They are diffractive implants having far vision and near vision whose phase of the optical transfer function is constant over an intermediate to extended near vision zone, i.e. without phase inversion up to a spatial frequency of 100 cycles / mm, this optical transfer function being constant over a range of addition values ​​which is at least 30% (and preferably 45%) wider than that of a conventional bifocal implant, such as that called ARtis PL M, marketed by the present applicant.

[0053] To the figure 2attached is the phase transfer function at 100 cycles / mm as a function of the addition for a “classic” bifocal implant with +3 D ​​addition.

[0054] We note that the phase is constant (curve D) over the zone 1.35 D to 2.3 5D, i.e. over a depth of 1 D in the corneal plane.

[0055] An example of a constant phase widened near vision profile of an implant according to the invention is shown in figure 3 .

[0056] We note that the phase is constant over the zone 0.6D to 2.05 D, or over a depth of 1.45D in the corneal plane.

[0057] Such curves can be obtained from different diffractive optical implants, which will be described below.

[0058] It is obviously considered that an implant of this type comprises a body with at least one optical surface having an optical axis and a plurality of diffractive zones arranged concentrically around this optical axis, these concentric zones each having at least one radius r.

[0059] For a bifocal implant, the radii of the successive rings have a radius r N such that: r N = 2 N λ . f p relationship in which: N is the ring number (counted from the center); fp is the focal length corresponding to the addition for near vision λ is the design wavelength (typically 546 nm).

[0060] The height h of the diffractive steps (ladders) of the zones is: h = α λ Δ n relationship in which: Δn is the variation in refractive index (i.e. the difference between the refractive index of the implant material and that of the aqueous humor of the eye, or of the surrounding environment in the case of an intracorneal implant); α is the profile height factor.

[0061] If α=0.5, then the relative energy distribution is 50% for distance vision and 50% for near vision.

[0062] The shape of the diffractive echelons of each zone is called "kinoform" and is described by a parabola on each echelon such that: Profil x = ∝ ⋅ λ Δ n ⋅ r N 2 − x 2 r N 2 − r N − 1 2

[0063] Where x is the radial position.

[0064] According to the invention, an implant having a continuous phase profile between near vision and intermediate vision is produced by using diffractive profiles giving an extended depth of field.

[0065] The central zone of such an implant is defined by a profile whose radius of successive rings r N is fixed by an equation of the type: r N = 2 N λ f p + 2 . λ . F 2 N . Δ f expression in which F2(N) is a polynomial of the variable N of order 3 minimum. F2(N) can have as expression F 2 N = cte + a . N + b . N 2 + c . N 3 + d . N 4 + ⋯ Or : N is an integer greater than 1; λ is the design wavelength; fp is the focal length corresponding to the addition for near vision; Δ f is the focal length variation; cte is a constant consisting of a real number between -5 and +5; a, b, c and d are real numbers between -5 and +5.

[0066] Note that F2(N) can be a function whose limited or Taylor expansion is equivalent to the polynomial expressed above. By the term "equivalent" we mean that the limited or Taylor expansion of said function gives the same result as the function F2(N) expressed above.

[0067] For purely indicative purposes, these implants may include a central region (for example, 1.5 to 6 mm in diameter) with extended depth of field and possibly a “peripheral” zone region that can be described as classic (for example, 2 to 6 mm in diameter).

[0068] To the figure 4 is shown the "half" profile of an implant I1 in accordance with the present invention.

[0069] By "half" profile, we mean the fact that the ordinate axis, which translates the height of the scales of these implants in micrometers, is merged with their optical axis AO and that we have represented only the profile which extends on one side of this axis.

[0070] In this figure, said central and peripheral regions are respectively referenced RC and RP.

[0071] It should be noted here that the profile of the fourth ladder visible in this figure has been cut, due to the beginning of the peripheral region RP.

[0072] Although "kinoform", the ladders could have a different shape (sine, cosine for example), this different shape not drastically modifying the present invention.

[0073] In the case presented here, the different diffractive zones have a circular outline. However, according to alternative embodiments, not shown here, these diffractive zones have an elliptical outline of which r N is the small ray.

[0074] Still according to the embodiment presented here, the central region RC has an extended depth of field, has a radius of at least one millimeter and is surrounded by a peripheral region RP refractive or diffractive, monofocal or multifocal, for example of bifocal equation: r N = 2 N λ . f p .

[0075] Conversely, it could be the opposite, so that it would be the central region RC, with a radius of at least one millimeter, which would be refractive or diffractive, monofocal or multifocal, for example with a bifocal equation: r N = 2 N λ . f p

[0076] To the Figure 5 is shown the "half-profile" of another I2 implant in accordance with the present invention.

[0077] The main parameters of implants according to the invention are given below. Example 1 :

[0078] Function F(N) of order 4 (which corresponds to the profile of the Figure 5 and to the curves of the figure 6 ) : Table 1 Central region: rings 1 to 4 f p 1 1000 / 3.05 ∝ 1 0.5 D f 800 Peripheral region: rings 6 to 12 f p 2 1000 / 2.77 ∝ 2 0.5 Central region: r 1 N = 2 λ . N . f p 1 + 2 λ . N . N − 1 5 3 . Δ f Profil 1 x = ∝ 1 . λ Δ n . r 1 N 2 − x 2 r 1 N 2 − r 1 N − 1 2 Peripheral region: r 2 N = 2 N λ . f p 2 Profil 2 x = ∝ 2 . λ Δ n . r 2 N 2 − x 2 r 2 N 2 − r 2 N − 1 2

[0079] As can be seen on the figure 6, the phase is constant over the area from 0.5D to 2.05, i.e. over a depth of 1.55D in the corneal plane. Example 2 (which corresponds to the profile of figure 4 and the curves of figure 7)

[0080] Function F(N) of order 5: Table 2 Central region: rings 1 to 4 f p 1 1000 / 3.05 ∝ 1 0.5 D f 1400 Peripheral region rings 6 to 12 f p 2 1000 / 2.77 ∝ 2 0.5 central region: r 1 N = 2 λ . N . f p 1 + 2 λ . N . N − 1 5 4 . Δ f Profil 1 x = ∝ 1 . λ Δ n . r 1 N 2 − x 2 r 1 N 2 − r 1 N − 1 2 peripheral region: r 2 N = 2 N λ . f p 2 Profil 2 x = ∝ 2 . λ Δ n . r 2 N 2 − x 2 r 2 N 2 − r 2 N − 1 2

[0081] As can be seen on the figure 7 , the phase is constant over the area from 0.5D to 2.14D, i.e. over a depth of 1.64D at the corneal plane.

[0082] Finally, in the embodiment of the figure 8 , the phase is constant over the area from 1.1D to 3.3D, or over a depth of 2.2 in the corneal plane.

[0083] As indicated above, the diffractive profiles (also called steps or ladders) of the implants according to the invention can be apodized (that is to say that we are dealing with a reduction in the height of the steps between the center and the periphery) as a function of the radius (which constitutes the variable x), according to the following equation: Profil Apodisé x = Profil x * Apodisation x

[0084] The function "apodization(x)" is a decreasing function such that, for 0 <abs(x)<r max (r max = rayon maximal du profil diffractif), alors 0<Apodisation(x) ≤1.

[0085] For example, this function can take the following form: Apodization (x) = (1- abs(ax / b)^c) with a, b and c consisting of real numbers.

[0086] The diffractive profile may be composed of concentric, circular or oval diffractive steps (echelettes). In other embodiments the diffractive effect may be obtained by alternating solid areas and empty areas (holes, slits), which modifies the local refractive index by zones and generates diffraction in the same way as the echelettes.

[0087] Expressed differently, this diffractive profile can be defined not by a geometric shape, but by a variation in the refractive index of the material(s) that compose it and that will create the same effect. The modification of the refractive index can for example be obtained by alternating solid zones with the index "n mat" and empty zones with the index "n0" (made up of holes, slits), which modifies the local refractive index by zones and generates diffraction in the same way as the echelettes.

[0088] The implants according to the invention can correct presbyopia. They can also correct other ametropias (myopia, hyperopia, astigmatism).

[0089] These may be intracorneal implants (lenticules), anterior chamber (phakic or pseudophakic), or intraocular posterior chamber or sulcus).

Claims

1. A diffractive ocular implant with correct distance vision, i.e., a vision such that the modulation transfer function (MTF) of said implant is greater than 20% at 50 cycles / mm on a 3mm pupil, and enlarged near vision (I1, I2), i.e., with an absence of discontinuity of its phase transfer curve as a function of the viewing distance (abbreviated PTF-TF), characterized by the fact that: - it has a phase transfer curve as a function of the viewing distance (PTF-TF) with an absence of discontinuity over a depth of field of at least 1.3D in the corneal plane, i.e., over an area of additions in the corneal plane of at least 1.3D, the addition in the corneal plane being understood as the inverse of the distance between the object viewed and the cornea, advantageously greater than 1.45D, which absence of discontinuity is located between intermediate vision and near vision, i.e. between 0.5D and 4D for spatial frequencies from 0 to 100 cycles / mm for a pupil of at least 3 mm in diameter, - it comprises a body with at least one optical surface having an optical axis (AO) and a plurality of diffractive zones arranged concentrically around said optical axis (AO), these concentric zones each having at least one radius r and being distributed between a central region (RC) and a peripheral region (RP), at least one central region (RC) or peripheral region (RP) of said diffractive zones having a profile of N successive echelettes, the successive rN of which, as one moves away from said optical axis (AO), respond to the relation: r N = 2 N λ f p + 2 . λ . F 2 N . Δ f relation wherein: N is an integer greater than or equal to 1 and taking successive integer values up to N max, wherein N max is at least 4 ; λ is the conception wavelength; fp is the focal length corresponding to the addition for near vision; Δf is the focal length variation;, which is not zero, positive or negative, and whose absolute value is less than 10,000; F2(N) is either a polynomial of the variable N of order between 3 and 5, which is expressed as follows: F 2 N = cte + a . N + b . N 2 + c . N 3 + d . N 4 + ⋯ , - and that the maximum height h of said successive echelettes (diffractive steps) being given by the relation: h = α λ Δ n relation wherein: - Δn is the refractive index variation, i.e., the difference between the refractive index of the implant material and that of the aqueous humor of the eye or the surrounding environment; - α is the height factor of the echelette, comprised between 0.25 and 1.75.

2. The implant (I1, I2) according to claim 1, characterized by the fact that "cte" is a real number comprised between -5 and +5.

3. The implant (I1, I2) according to claim 1 or 2, characterized by the fact that a, b, c, d etc. are real numbers comprised between -5 and +5.

4. The implant (I1, I2) according to one of claims 1 to 3, characterized by the fact that said diffractive zones have a circular contour.

5. The implant (I1, I2) according to one of claims 1 to 3, characterized by the fact that said diffractive zones have an elliptical contour of which rN is the small radius.

6. The implant (I1, I2) according to one of claims 1 to 3, characterized by the fact that said diffractive zones are made up by alternating full zones of an index "nmat" and empty zones of an index "n0", said empty zones consisting of slits or holes.

7. The implant (I1, I2) according to one of claims 1 to 6, characterized by the fact that said curve has no discontinuity from 0.8D in the corneal plane.

8. The implant (I1, I2) according to one of claims 1 to 6, characterized by the fact that said curve has no discontinuity from 2D in the corneal plane.

9. The implant (I1, I2) according to one of claims 1 to 8, characterized by the fact that said region is a central region (RC) which has a radius of at least one millimeter and which is surrounded by a peripheral region (PR) which is refractive or diffractive, monofocal or multifocal, for example with a bifocal equation: rN = 2 N λ . f p .

10. The implant (I1, I2) according to one of claims 1 to 8, characterized by the fact that said region is a peripheral region (RP), which surrounds a central region (RC), the latter having a radius of at least one millimeter and being refractive or diffractive, monofocal or multifocal, for example with a bifocal equation: r N = 2 N λ . f p .

11. The implant (I1, I2) according to one of claims 1 to 10, characterized by the fact that function F2(N) is a polynomial of the variable N of order 3.

12. The implant (I1, I2) according to one of the preceding claims, characterized by the fact that it is chosen in the following group: intracorneal implant, anterior chamber (phakic or pseudophakic), posterior intraocular chamber or sulcus implant.

13. The implant (I1, I2) according to one of the preceding claims, characterized by the fact that it has an aspherical surface.

14. The implant (I1, I2) according to one of claims 1 to 5 and 7 to 13, characterized by the fact that it has an apodized profile, i.e., the height of said echelettes decreases as one moves away from said optical axis, in order to limit the halo phenomenon in night vision.