WO2025078144A1 - Intracorneal implant - Google Patents

Abstract

The invention relates to a transparent intracorneal implant (2), which has a rotationally symmetrical shape and which has a first, anterior face (20) and a second, posterior face (21) opposite said first, anterior face, and also a centred optical axis, this implant (2) comprising a set of peripheral through-holes (22), the axis (A) of which is parallel to said optical axis, which bring said first, anterior face (20) into communication with said second, posterior face (21), characterized in that the inner wall of at least some of said peripheral through-holes (22) locally comprises an inclined surface (23), which is inclined with respect to said optical axis and with respect to a plane perpendicular to said optical axis, and in that the area (E1) of their opening (24) on the anterior face (20) side is greater than or less than the area (E2) of their opening (25) on the posterior face (21) side.

Description

Intracorneal implant

GENERAL TECHNICAL FIELD

The present invention lies in the field of multifocal intracorneal implants.

STATE OF THE ART

Presbyopia is the progressive loss of our eye's ability to correctly accommodate near objects. It is an inevitable phenomenon linked to the loss of elasticity of the lens with age and which affects the entire population. The number of people worldwide suffering from presbyopia was estimated at 1.8 billion in 2015, including approximately 20 million French people (source: Fricke et al., "Global Prevalence of Presbyopia and Vision Impairment from Uncorrected Presbyopia"). The correction of presbyopia therefore represents a significant economic and societal challenge.

There is currently no accepted solution to restore the accommodative function of the lens.

Near vision loss is most often corrected by the use of glasses (reading glasses or glasses with lenses of varying power (bifocals, progressive lenses, etc.)), lenses (multifocal or monofocal, but with different powers for each eye), laser surgery (Lasik technique ("Laser-Assisted In-Situ Keratomileusis"), PRK technique ("Photorefractive Keratectomy")), or through the use of implants.

These implants can be of two types, namely intraocular (the removal of the lens de facto resulting in presbyopia) or intracorneal (the implant is placed in the cornea, within the stroma).

From an optical point of view, the techniques involved can be grouped into three categories.

The first is monovision: one eye is corrected for near vision, the other for distance vision, and the oculocerebral system selects the clear image.

The second is multifocality: the eye is corrected for two or three precise distances, thanks to a multifocal profile (introduced by an implant, such as the implant called “Symbiose” of the present applicant, or induced on the cornea by photoablation). The third is increasing the depth of field, through an approach similar to the multifocal approach or by pupil reduction (such as the implant known under the registered trademark KAMRA).

Among the various correction methods listed above, corneal implants represent a solution that is still underdeveloped. This is partly due to the difficulty of meeting the biocompatibility constraints specific to the cornea.

On the contrary, they present several advantages over existing solutions.

Indeed, they can allow one to do without lenses or glasses, are less invasive than intraocular implants, potentially pose less risk to the cornea than laser surgery (Lasik) and above all, unlike these solutions, they are not definitive since they are additive (no tissue is removed, which preserves the integrity of the cornea for other future options) and can be removed at any time.

Current intracorneal implants can be grouped into three categories depending on the approach used to modify the optical power of the eye.

Thus, the implant can act only by changing the curvature of the cornea (as described in particular in EP1989585). It can have its own power (such as the one known under the brand name “Presbia Flexivue Microlens”) or combine both techniques.

Another approach, cited previously, does not modify the power of the eye but only increases the depth of field by reducing the diameter of the pupil (as described in particular in EP2258311).

However, regardless of the category, an important constraint is that the implant does not negatively disrupt the passage of nutrients, oxygen and waste through the cornea.

In fact, the cornea is not vascularized and receives its oxygen and nutrients from tears and aqueous humor.

The first attempts at intracorneal implants were clinical failures because the materials used (hydrogel, hydroxyethyl methacrylate and methyl methacrylate) did not allow efficient transfer of oxygen and nutrients through the cornea.

Two approaches can be implemented to address this constraint: - Use a suitable material, i.e. permeable and which does not disrupt the metabolism of the cornea;

- make drainage holes in the implant to allow nutrients to pass through (see for example the aforementioned document EP2258311).

Currently, despite progress in the development of hydrogel materials or the use of donor tissues, no perfectly suitable material exists.

The use of drainage holes is a solution that causes light to diffract through these holes.

Thus, many patent publications describe a plurality of holes, pores, perforations, fractures or even structures whose orientation, spacing and shape make it possible to reduce the visible effects of diffraction (see for example document US10004593) and which also serve the passage of nutrients.

An intracorneal implant has thus been proposed to correct presbyopia, with a central hole sized to increase the depth of field and peripheral through holes distributed around the central through hole, which not only allow the passage of nutrients, but also generate a near focus for the eye.

In any case, the use of holes to create an optical function is known.

Each of the presbyopia corrections presented above has its drawbacks.

For example, wearing progressive glasses is a constraint and they are not always well accepted.

Intraocular lenses require removal of the lens, so this invasive procedure is performed after the patient has developed cataracts.

One of the techniques mentioned above drastically reduces the size of the pupil. Therefore, the implant can only be implanted in one eye and provides little improvement to the patient's vision.

In document W02017/109250 an implant is described which creates three optical foci, but with the same quantity of light in the two opposite foci (order 1 and -1). Knowing that it is preferable to have a higher amount of energy for distance vision (for example 60% in relative distribution), two options are possible:

- Use only two of these foci, one for near vision and the other for distance, and lose as much energy as that which goes into near vision;

- Use the three orders of diffraction, one for near vision, one for intermediate vision and one for distance vision. But this leaves only a fairly low diffraction energy for distance vision, far from the 60% usually attributed.

Documents WO00/25704, US2004/019379, as well as the article “Walter D FURLAN ET AL. “A new trifocal corneal inlay for presbyopia”, ARXIV.ORG, CORNELL UNIVERSITY LIBRARY” constitute prior art of interest. Document WO00/25704 describes an implant that has through holes. However, these holes only serve to modify the elasticity of the implant and nothing is said about their shape.

The present invention aims to improve the implant described above and to propose an intracorneal implant which is not only multifocal, but which also allows the distribution of energy to be controlled in various focal planes, while being permeable to nutrients.

PRESENTATION OF THE INVENTION

Thus, a first aspect of the invention relates to a transparent intracorneal implant, which has a shape of revolution and which has a first anterior face and a second posterior face opposite said first anterior face, as well as a centered optical axis, this implant comprising a set of peripheral through-holes, with an axis parallel to said optical axis, which connect said first and second anterior and posterior faces, characterized in that the internal wall of at least a portion of said peripheral through-holes locally comprises an inclined surface, which is inclined relative to said optical axis and relative to a plane perpendicular to said optical axis and that the area of their opening on the side of said anterior face is greater or less than the area of their opening on the side of said posterior face. Thanks to the presence of peripheral through holes which locally have an inclined surface and which can be described as "truncated holes", the symmetry of the distribution of light energy along the optical axis of the implant is broken and 45 to 70%, and preferably 60% of energy is obtained in distance vision.

Furthermore, an implant as defined above, the area of the opening on the side of said anterior face of which is greater than the area of the opening on the side of said posterior face, has the same optical characteristics as an implant the area of the opening on the side of said anterior face of which is less than the area of the opening on the side of said posterior face.

By the term "locally" is meant that the inclined surface has a projected area in the plane of the implant greater than 0% and less than 100% of the area of the hole projected in the plane of the implant, preferably between 40% and 95%, and even more preferably between 80% and 90%.

Other advantages of the invention will become apparent from the following description.

According to other advantageous and non-limiting characteristics of this device, taken alone or according to a technically compatible combination of at least two of them:

- at least a portion of said peripheral holes is inscribed in a shape of revolution or substantially of revolution;

- said inclined surface is radially external or radially internal;

- it also includes an additional central through hole which connects said first and second anterior and posterior faces and which is centered on said optical axis;

- said inclined surface is flat;

- said inclined surface is curved;

- said inclined surface has a parabolic or sinusoidal profile;

- said inclined surface comprises an alternation of flat faces perpendicular to each other, which gives it a staircase profile;

- said inclined surface has an inclination of between 5 and 45°; - it has peripheral through holes without said inclined surface;

- said peripheral holes are distributed in concentric rings centered on said optical axis;

- at least a portion of said peripheral through holes which locally comprise an inclined surface are present in one ring out of two;

- said holes are generally cylindrical in shape;

- said holes are inscribed in a shape of revolution with a trapezoidal base;

- it has a thickness of between 2 and 100 micrometers, and preferably between 3 and 20 micrometers.

DESCRIPTION OF FIGURES

Other characteristics and advantages of the invention will appear from the description which will now be given, with reference to the appended drawings, which represent, for informational but non-limiting purposes, a possible embodiment.

On these drawings:

Figure 1 is a representation of an Airy spot, that is, a point spread function of a perfect optical system;

Figure 2 is a phase screen of a conventional so-called “photon sieve” implant;

Figure 3 is the energy curve along the optical axis (more precisely the Strehl ratio circumscribed to the Airy spot) of the implant of Figure 2;

Figure 4 is a phase screen of one embodiment of an implant according to the present invention;

Figure 5 is a perspective view of a region of the implant of Figure 4, intended to illustrate the shape of the holes therein;

Figure 6A is a cross-sectional view of the region illustrated in Figure 5;

Figure 6B is a view similar to Figure 6A, the hole shown being devoid of an inclined surface; Figure 7 is the energy curve along the optical axis (more precisely the Strehl ratio circumscribed to the Airy spot) of the implant of Figure 4;

Figure 8 is a phase screen of a variant of the implant according to the present invention;

Figure 9 is a very simplified diagram of an alternative embodiment of a “truncated hole” that the implant according to the invention comprises;

Figure 10 is a view similar to Figure 9, of yet another alternative embodiment of a “truncated hole” included in the implant according to the invention;

Figure 11 is a view similar to Figure 9, of yet another alternative embodiment of a “truncated hole” included in the implant according to the invention;

Figure 12 is a phase screen of another variation of the implant according to the present invention;

Figure 13 is the energy curve along the optical axis (more precisely the Strehl ratio circumscribed to the Airy spot) of the implant of Figure 12;

Figure 14 is a view similar to that of Figure 6A, with the truncated hole shown being located near a central hole;

Figure 15 is a variant of the embodiment of Figure 14, which constitutes an optical equivalent thereof;

Figure 16 is a variation of the embodiment of Figure 14;

Figure 17 is a variant of the embodiment of Figure 16, which constitutes an optical equivalent thereof.

DETAILED DESCRIPTION OF THE INVENTION

Introduction

The Point Spread Function (PSF) is the spatial impulse response. It is a mathematical function that describes the response of an imaging system to a point source. The PSF of a perfect optical system is the Airy task of Figure 1. The fact that the image of a point through a perfect optical system is not a point is due to diffraction.

The closer the image transmitted through an optical system is to the Airy spot, the sharper and brighter the image. The sharper and brighter the image, the more energy there is in the "PSF". This high energy value in the "PSF" is reflected by a peak in the "Energy through focus" curve (abbreviated "ETF", which can be translated as "distribution of light energy along the optical axis"). Such a curve has the distance between the different foci of the lens on the abscissa. Zero corresponds to distance vision, intermediate and near vision are found for negative abscissas.

Another possible x-axis is the power in diopters corresponding to the difference in distance between the foci. Zero always corresponds to distance vision, intermediate and near vision are at the addition values necessary to see clearly at these distances.

The y-axis indicates a ratio between the energy of the proposed implant at a given distance and the energy at the same distance of a perfect lens.

To calculate the "Energy through focus", the "PSF" is calculated for different values along the optical axis. The energy in the central circle of the implant's PSF is then calculated, which is normalized with the energy at the center of the Airy spot of a perfect lens. This gives a value for each of the calculation distances, which makes it possible to obtain the "Energy through focus" curve.

Basis of the present invention

The design of the implant according to the present invention is based on the principle of transparent photon sieves (hereinafter PS).

The transparent photon sieves are essentially a Fresnel zonal plate where holes 10 (through, i.e. opening onto the two opposite faces of the implant), in addition to a central hole 11 aligned with the optical axis, are distributed over the open areas, as shown in Figure 2.

These transparent photon sieves are transparent plates that induce a phase shift of half a wavelength. As can be seen on Figure 2, the holes 10 are arranged in concentric circles so that the combination of the half-wavelength phase shift and the arrangement of the holes makes it possible to obtain constructive interference in 2 foci.

In a standard design as shown in this figure, the holes 11 are arranged in n concentric circles (or rings) whose radii R _n are given by the relation:

[Math. 1]

Relationship in which n is the ring number, f the focal length of the photon sieve and X the wavelength. The associated phase profile allows constructive interference to be obtained at two foci.

In the same standard design as shown in this figure, the holes 11 have a diameter D _n given by the relation:

[Math. 2]

Relation in which n is the ring number, f the focal length of the photon sieve and X the wavelength, K between 0.7 and 2.

In Figure 2, the dimensions of the implant are shown in meters on the x-axis and y-axis, and the grayscale on the right of the figure illustrates the phase of the implant (the "zero" corresponds to the presence of a through hole (perforated part), while "n" or "3.14" corresponds to the absence of a hole (smooth part)).

Figure 3 shows the energy curve as a function of defocus associated with the PS photon sieve of Figure 2, in an eye with a power of 60D.

The thickness of the PS is chosen to produce a phase shift of n between the smooth part and the holey part (respectively the white part and the black part in the image of Figure 2).

In this example, the central hole 11 and holes 10 have a diameter of 700 and 175 micrometers respectively.

The central peak of the curve corresponds to light passing through the implant without forming interference (order 0), and the left and right peaks, of equal dimensions, correspond to order -1 and +1 respectively. Photon sieves are therefore circular diffraction gratings.

The theory of diffraction gratings says that for a binary grating (presence of a hole/absence of a hole), we will always have as much energy in order 1 as in order -1.

Knowing that to correct presbyopia, we seek to make implants that distribute light along the optical axis, keeping if possible 60% of energy for distance vision, and the rest of the energy distributed as much as possible on near vision (which corresponds to the positive diffraction orders), such a goal cannot be achieved with the transparent photon sieves of figure 2 which deliver a significant quantity of lost energy in the negative orders.

In the present application and in order to have a metric suitable for analyzing the focusing properties of the PS, use is made of the encircled Strehl ratio (ES) defined as the ratio of the encircled (or circumscribed) energy of the PSF on an area delimited by the first ring of the Airy spot, to the encircled energy in the Airy spot, always in its first ring.

The focal length chosen to calculate the diameter of the Airy spot (visible in Figure 1) is that of the eye (60D). This corresponds to the case where the intracorneal implant only provides additional power for intermediate and near vision.

Possible embodiments of an implant according to the present invention

Starting from conventional photon sieves such as that shown in Figure 2, the present applicant has found that by "introducing" a "slope" into at least part of the holes of the photon sieve such as that of Figure 2, the symmetry of the distribution of light energy along the optical axis is broken.

Thus and as illustrated in figure 4 which represents a possible embodiment of the invention, the latter relates to a transparent corneal implant 2, which has a shape of revolution and which has a first anterior face 20 and a second posterior face 21 opposite the first anterior face, as well as a centered optical axis X.

In this figure, on the abscissa x and ordinate y are the possible dimensions of the implant, expressed in meters and the level scale of gray placed on the right of the figure illustrates the phase of the implant (“-n” corresponding to the presence of a through hole (perforated part), while “n” corresponds to an absence of hole (smooth part)).

This implant comprises a set of peripheral through holes 22 which are inscribed in a form of revolution and are of axis A, which is parallel to the optical axis X. They connect the first and second anterior 20 and posterior 21 faces.

According to the invention, the internal wall of at least a portion of these peripheral through holes 22 locally comprises an inclined surface 23, which is inclined relative to the optical axis X and relative to a plane perpendicular to this optical axis.

Furthermore, the area of their opening on the side of the anterior face 20 is greater than the area of their opening on the side of the posterior face 21.

Reference may be made to Figures 5 and 6A which illustrate a possible embodiment of one of these holes. For convenience of language, throughout the present application, such a hole 22 may be referred to hereinafter as a “truncated hole” and the inclined surface may be referred to as a “slope”. Conversely, a hole without an inclined surface may be referred to as a “non-truncated hole”.

Furthermore, when "slope" is used in the mathematical sense of the term, it is referred to as inclination.

In this figure, we see that the hole 22 is part of a shape of revolution, in this case a right cylinder. However, such a shape could be substantially of revolution in the sense that the wall of the hole could locally have at least one region which is not of revolution.

Shapes other than those of a right cylinder with axis A parallel to the optical axis X of the implant can be considered, as will be seen later.

In Figure 6A, the opening of the hole 22 on the side of the anterior face 20 has been referenced 24 and the opening on the side of the posterior face 21 has been referenced 25. The corresponding areas of these openings have the references E1 and E2.

Simply for comparison, a non-truncated hole 10 has been shown in Figure 6B. It has a diameter D identical to that of the shape of revolution in which the hole 22 is inscribed.

According to a possible embodiment which is illustrated in Figure 5, each hole 22 has an inclined surface 23 which is radially external. This means that this surface 23 is turned radially towards the outside of the implant, that is to say towards its periphery.

According to another possible embodiment, each hole 22 has an inclined surface 23 which is radially internal. This means that this surface is turned radially towards the inside of the implant, that is to say towards its center.

Figure 7 shows the energy curve as a function of defocus associated with the implant of Figure 4 in a 60D eye.

The thickness of the implant is chosen to produce a phase shift of 2 n between the holed and non-holed regions. The highest peak of the curve corresponds to light passing through the implant without forming interference (order 0), while the other two correspond to orders +1 and +2, which can be used for intermediate and near vision, respectively.

Thus, the objective of obtaining 45 to 70%, and preferably 60% of energy in distance vision, is achieved.

Advantageously, the inclined surface 23 is flat and has an inclination of between 5 and 45°.

As mentioned above, the surface 23 can be turned radially towards the outside of the implant, i.e. towards its periphery.

In this case, the energy distribution along the optical axis will be symmetrical to that of the implant in Figure 4 relative to 0D. This is of no interest in the correction of presbyopia, but can be used to correct high myopia.

The sizing of the smallest E2 area must of course be chosen to allow the passage of nutrient molecules when the implant is in place in a patient's eye.

As noted above, the implant thickness can be chosen, for example, to produce a phase shift of 2n. This configuration has several advantages.

Thus, the size of the central hole 11 of the implant of figure 4, which connects the first and second anterior 20 and posterior 21 faces and which is centered on said optical axis has practically no impact on the distribution of light. Under these conditions, it is entirely possible to do without it.

Furthermore, still with reference to figure 4, the implant 2 comprises, apart from the central hole 11, exclusively “truncated holes” 22. However, for the same reason as previously, it is possible to add to the implant “non-truncated” holes 10 such as the one shown in Figure 6B. Such “straight holes” make it possible to obtain additional drainage capacity without modifying the optical power of the implant. They therefore have only a physiological function.

The embodiment of the implant of Figure 8 has such characteristics. Indeed, it has alternating rings of “truncated holes” 22 and “non-truncated holes” 10.

The relationship Rn expressed above is valid for all the “truncated holes” 22 of this embodiment. For the non-truncated holes 10 which are here also represented in the form of concentric rings, they could be placed anywhere on the implant. There is also no optical constraint on the size of holes which only participate in drainage.

In variants not shown, this "distribution" in regular and alternating rings is replaced by a random distribution.

In the embodiments described so far, the inclined surface 23 which has been considered is strictly planar.

However, the present applicant has noticed that the objective of the present invention is also fulfilled, even when this surface is not strictly flat.

Thus, it is possible to implement the present invention by using an implant whose "truncated holes" have an inclined surface which is curved. This is shown in Figures 9 and 10 in which the inclined surface 23 has a parabolic, respectively sinusoidal, profile.

In the embodiment of figure 11, the inclined surface 23 comprises an alternation of flat faces perpendicular to each other (i.e. parallel, respectively perpendicular to the axes X and A), which gives it a staircase profile.

In these three figures, the reference numerals designate the same elements as in Figure 6A.

In these embodiments, the “average slope” of the surface 23, that is to say its inclination, preferably has the values indicated above.

In the preceding examples, the holes 22 are part of a shape of revolution, in this case a right cylinder with a circular base.

However, other embodiments may be envisaged, for example star-shaped, elliptical, etc. An example of this is given in Figure 12, where the "truncated" holes 22 are part of a trapezoidal-based revolution shape.

Again, when examining Figure 13 which shows the energy curve as a function of defocus associated with the implant of Figure 6A, it is noted that the objective of the present invention is also achieved.

Other shapes can be considered, for example to modify monochromatic or chromatic aberrations.

In Figure 14 is shown a truncated hole 22 which has the same configuration as that of Figure 6A. In this figure as well as the following ones, the direction of the light is defined by the arrow L. The hole 22 is shown close to the central hole 11, so that it can be seen that the inclined surface 23 is oriented towards the center of the implant.

In the embodiment of Figure 15, the truncated hole 22 also has an inclined surface 23 which is oriented towards the center of the implant. However, it is noted that the inclined surface 23 is inverted compared to the embodiment of Figure 14, which means that its opening 24 which opens onto the anterior face 20 has an area E1 which is less than the area E2 of the opening 25 which opens onto the posterior face 21.

Optically, these two embodiments are equivalent in the sense that their optical properties are the same.

The embodiment of figure 16 differs from that of figure 14 in that the inclined surface 23 of the hole 22 is oriented towards the periphery of the implant.

In the variant of Figure 17, the inclined surface 23 is reversed compared to the embodiment of Figure 16.

Again, in these last two embodiments, the optical properties of the implant are the same.

The main technical advantage of the invention is to have a distribution of light energy along the optical axis compatible with correcting presbyopia (with a greater distribution of light energy for distance vision than for intermediate or near vision).

The key element of the invention is the presence of an inclined surface inside the holes which makes it possible to obtain an asymmetry of the energy distribution and therefore to devote a larger part to distance vision. One possibility for manufacturing such an implant is, for example, the use of a photolithography technique on biocompatible materials or laser engraving on films of biocompatible materials.

Claims

1. Transparent intracorneal implant (2), which has a shape of revolution and which has a first anterior face (20) and a second posterior face (21) opposite said first anterior face, as well as a centered optical axis (X), this implant (2) comprising a set of peripheral through-holes (10, 22), of axis (A) parallel to said optical axis, which connect said first (20) and second (21) anterior and posterior faces, characterized in that the internal wall of at least a part of said peripheral through-holes (22) locally comprises an inclined surface (23), which is inclined relative to said optical axis (X) and relative to a plane perpendicular to said optical axis (X) and that the area (E1) of their opening (24) on the side of said anterior face (20) is greater or less than the area (E2) of their opening (25) on the side of said posterior face (21). 2. Implant (2) according to claim 1, characterized in that at least a portion of said peripheral holes (10, 22) are inscribed in a shape of revolution or substantially of revolution. 3. Implant (2) according to claim 1 or 2, characterized in that said inclined surface (23) is radially external or radially internal. 4. Implant (2) according to one of claims 1 to 3, characterized in that it also comprises an additional central through hole (11) which connects said first and second anterior and posterior faces (20, 21) and which is centered on said optical axis (X). 5. Implant (2) according to claim 1 or 2, characterized in that said inclined surface (23) is flat. 6. Implant (2) according to claim 1 or 2, characterized in that said inclined surface (23) is curved. 7. Implant (2) according to claim 4, characterized in that said inclined surface (23) has a parabolic or sinusoidal profile. 8. Implant (2) according to claim 1 or 2, characterized in that said inclined surface (23) comprises an alternation of flat faces perpendicular to each other, which gives it a staircase profile. 9. Implant (2) according to one of the preceding claims, characterized in that said inclined surface (23) has an inclination of between 5 and 45°. 10. Implant (2) according to one of the preceding claims, characterized in that it comprises peripheral through holes (10) devoid of said inclined surface. 11. Implant (2) according to one of the preceding claims, characterized in that said peripheral holes (10, 22) are distributed in concentric rings centered on said optical axis (X). 12. Implant (2) according to claim 11, characterized in that at least a portion of said peripheral through holes (22) which locally comprise an inclined surface (23) are present in one ring out of two. 13. Implant (2) according to one of the preceding claims, characterized in that said holes (10, 22) are inscribed in a generally cylindrical shape. 14. Implant (2) according to one of claims 1 to 12, characterized in that said holes (10, 22) are inscribed in a shape of revolution with a trapezoidal base. 15. Implant (2) according to one of claims 1 to 14, characterized in that it has a thickness of between 2 and 100 micrometers, and preferably between 3 and 20 micrometers.