WO2023161591A1

WO2023161591A1 - Intraocular lens with diluted-luminosity optics

Info

Publication number: WO2023161591A1
Application number: PCT/FR2023/050259
Authority: WO
Inventors: Frédéric Hehn
Original assignee: Hehn Frederic
Priority date: 2022-02-24
Filing date: 2023-02-24
Publication date: 2023-08-31
Also published as: FR3132836A1

Abstract

The invention relates to an intraocular lens (12) having an optical centre and an optical axis (y). The intraocular lens (12) moreover has a radius of curvature that is continuous and increasing from the optical centre to a peripheral edge of the intraocular lens (12) as a function of the distance to the optical axis (y) so that the intraocular lens (12) has an asphericity value substantially equal to the following value: [Math 30] -2_n2 where n is the refractive index of the intraocular lens (12).

Description

Title: Intraocular lens with optics by dilution

The field of the invention relates to ophthalmology, and more particularly to intraocular lenses.

[0002] Cataract is an opacification of the lens of the eye responsible for a progressive loss of sight and increased sensitivity to light. Mainly related to aging, cataracts can also be caused by trauma, long-term treatment with corticosteroids or certain chronic diseases such as diabetes.

[0003] It has been known for several decades to treat cataracts by a surgical intervention consisting in replacing the opacified lens of the patient's eye with an intraocular lens - or implant. Replacement with an artificial lens is the only solution since it is not possible to restore the transparency of the clouded lens.

[0004] Furthermore, an intraocular lens can also be used to treat certain visual deficiencies, in particular myopia, hyperopia, astigmatism or even presbyopia. Generally, in such a case, the natural lens is preserved, so that the intraocular lens constitutes an additive implant. This is called phakic implantation. It should be noted that these visual deficiencies can be treated by laser surgery to modify the profile of the cornea but that some patients have contraindications to such an operation, especially if they suffer from an autoimmune disease or corneal pathology.

[0005] The work of the Applicant led him to propose, in international application WO 2013/110888, an intraocular lens allowing both to treat cataracts and to correct myopia (or hyperopia) and presbyopia.

[0006] Research in the field of intraocular lenses is however still very recent and, in the particular case of the joint treatment of cataracts and presbyopia, current solutions do not make it possible to obtain a satisfactory depth of field. In particular, existing intraocular lenses do not offer a sufficiently sharp image of an object in near vision.

The present invention improves the situation. As such, the present invention relates to an intraocular lens, having an optical center and an optical axis, characterized in that it has an increasing and continuous radius of curvature from the optical center to a peripheral edge of the intraocular lens as a function of the distance from the optical axis so that the intraocular lens has an asphericity value substantially equal to the following value:

[0009] [Math. 1]

—2 n ²

[0010] where n is the refractive index of the intraocular lens.

[0011] In one or more embodiments, the intraocular lens comprises a variable portion over which the radius of curvature is strictly increasing. The variable portion is connected and symmetrical with respect to the optical axis.

[0012] The radius of curvature and the distance to the optical axis are for example linked by a polynomial relationship on the variable portion.

In one or more embodiments, the radius of curvature at a given point of the variable portion is determined as follows:

[0014] [Math. 2]

[0015] where: - x is the distance from the given point to the optical axis;

- xi is a predetermined distance;

- r(x) is the radius of curvature at the given point;

- Ro is the radius of curvature at the optical center; And

- a is a constant depending on the asphericity value.

[0016] In one or more embodiments, the constant a is calculated as follows: [Math. 3]

Where: - p is the radius of the intraocular lens; and - 1 is the length of the variable portion. [0017] In one or more embodiments, the variable portion covers the entire intraocular lens and:

[0018] [Math. 4] x ₁ = 0

[0019] [Math. 5] a = Q

[0020] where Q is the asphericity value of the intraocular lens.

[0021] In one or more embodiments, the intraocular lens comprises at least one constant portion over which the radius of curvature is substantially constant. Each constant portion is connected and symmetrical with respect to the optical axis.

In one or more embodiments, a constant portion is a central portion extending from the optical center and over which the distance to the optical axis is less than or equal to a first predetermined distance.

The predetermined distance xi is for example equal to the first predetermined distance.

[0024] In one or more embodiments, a constant portion is an eccentric portion extending to the peripheral edge and over which the distance to the optical axis is greater than or equal to a second predetermined distance.

In one or more embodiments:

[0026] [Math. 6] a < Q

[0027] where Q is the asphericity value of the intraocular lens.

In one or more embodiments, the refractive index is between 1.46 and 1.54 and the asphericity has a value between -0.94 and -0.84.

The present invention also relates to a method for determining a radius of curvature profile of an intraocular lens having an optical center and an optical axis, characterized in that it comprises the following operations implemented by an interface :

- receive ocular biometric measurements from a patient; - receiving parameters of the intraocular lens comprising at least one refractive index value; and in that it further comprises the following operations implemented by a processing unit:

- determining a radius of curvature value at the optical center of the intraocular lens according to the ocular biometric measurements and one or more of the parameters of the intraocular lens;

- determining, as a function of the radius of curvature value at the optical center of the lens, an increasing and continuous radius of curvature profile from the optical center of the desired intraocular lens to a peripheral edge of the intraocular lens as a function of the distance to the optical axis of the intraocular lens so that the latter has an asphericity value substantially equal to the following value:

[0030] [Math. 7]

—2 n ²

where n is the refractive index of the intraocular lens.

The present invention also relates to a computer program comprising instructions for implementing the above method, when the instructions are executed by at least one processor.

[0033] A non-transitory computer-readable storage medium storing this computer program is also contemplated.

Finally, the present invention further relates to a method of manufacturing an intraocular lens, characterized in that a radius of curvature profile of the intraocular lens is determined according to the method described above, and in that the lens intraocular lens is manufactured according to this radius of curvature profile.

The intraocular lens is made for example of a material comprising at least polymethyl methacrylate.

[0036] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the appended drawings, in which:

[0037] [Fig. 1] illustrates an optical diagram of an eye; [0038] [Fig. 2] illustrates an optical diagram of the eye of [Fig. 1] in which the natural lens has been replaced by an intraocular lens according to the invention;

[0039] [Fig. 3] illustrates the formation of a circle of confusion with lenses of distinct asphericities;

[0040] [Fig. 4] illustrates a point spread function obtained in far vision for the lenses of [Fig. 3];

[0041] [Fig. 5] illustrates a point spread function obtained in near vision for the lenses of [Fig. 3];

[0042] [Fig. 6] illustrates a point spread function obtained in intermediate vision for the lenses of [Fig. 3];

[0043] [Fig. 7] illustrates a system for determining a radius of curvature profile of an intraocular lens according to the invention;

[0044] [Fig. 8] illustrates a method of manufacturing an intraocular lens according to the invention;

[0045] [Fig. 9] illustrates an embodiment of the radius of curvature profile of the intraocular lens according to the invention; And

[0046] [Fig. 10] illustrates another embodiment of the radius of curvature profile of the intraocular lens according to the invention.

[0047] The [Fig. 1] illustrates an optical diagram of an eye 2. Such a diagram makes it possible to model the eye 2 in the form of a simplified optical system.

[0048] As illustrated in [Fig. 1], eye 2 has a cornea 4, a pupil 6, a lens 8 and a retina 10.

The cornea 4 is the transparent anterior part of the eyeball and fulfills the function of transmission and refraction of light. Indeed, the cornea 4, comparable to a converging lens, makes it possible to make the incident light rays converge towards the lens 8 which plays a complementary role in the refraction of light.

The profile of the cornea 4 can be characterized by an asphericity value, often denoted Q in the literature. This value Q translates the nature of the variation in the radius of curvature from the top of the cornea 4 towards its periphery. The top corresponds to the intersection of the optical axis y of the cornea 4 with its external surface, that is to say the surface furthest from the pupil 6. In [FIG. 1], the optical axis y of the cornea 4 coincides with the optical axis of the lens 8.

Thus, when the value Q is strictly negative (Q<0), the radius of curvature of the cornea 4 increases from the top towards the periphery. We then speak of a prolate profile. Conversely, when the Q value is strictly positive (Q>0), the radius of curvature of the cornea 4 decreases from the top to the periphery. We then speak of an Oblate profile. Finally, when the value Q is zero (Q=0), the radius of curvature of the cornea 4 is constant. The cornea 4 then has a spherical profile.

[0052] In general, a prolate or even hyper-prolate profile is advantageous since it makes it possible to improve visual performance in near vision. The Applicant has also worked on the subject by developing a process, called “advanced isovision” (known by the English name “advanced isovision”), consisting in reducing, by laser treatment on the periphery of the cornea 4, the value Q of asphericity. This method also makes it possible to maintain satisfactory performance for distance vision since the latter essentially solicits the central part of the cornea 4, close to the top.

[0053] Laser surgery may however be contraindicated for certain patients, in particular those suffering from an autoimmune disease or a corneal pathology. For these patients, the only solution is the implantation of an intraocular lens.

The pupil 6 is a circular orifice making it possible, by its contraction or its expansion, to regulate the quantity of light entering the eye 2. The pupil 6 can for example be compared to the diaphragm used in a photographic lens. The diameter of the pupil 6 thus varies according to the ambient light.

In the example illustrated in [Fig. 1], the pupil 6 is represented in a state of maximum contraction, reached by stimulation of the circular fibers of the iris, in response to high ambient light. In such a case, which corresponds to daytime vision, the diameter of the pupil 6 is said to be “photopic”. This photopic diameter is denoted here d _p .

When the ambient light is average, for example at dusk, the pupil 6 is in a state of average dilation and its diameter is then qualified as “mesopic”. Finally, in the example illustrated in [Fig. 2], the pupil 6 is shown in a state of maximum dilation, achieved by stimulation of the radial fibers of the iris, in response to very low ambient light. In such a case, which corresponds to night vision, the diameter of the pupil 6 is said to be “scotopic”. This scotopic diameter is denoted here d _s .

The lens 8 can be likened to a biconvex lens capable of deforming to allow the focusing, at the center of the retina 10, of an object in near vision, in intermediate vision or in far vision. It is the action of the ciliary muscle that makes it possible to modify the curvature of the lens 8 and in particular to increase it significantly to form a sharp image of a close object on the retina 10. This is called accommodation.

Like the cornea 4, the profile of the lens 8 can be characterized by an asphericity value, also denoted Q, which again reflects the nature of the variation in the radius of curvature from the center of the lens 8 towards its periphery. The center can refer here to the intersection of the optical axis y of the lens 8 with its external surface, that is to say the convex surface facing the cornea 4, or with its internal surface, that is i.e. the convex surface facing the retina 10.

[0060] The lens 8 has a negative asphericity value Q and the accommodation consists of further reducing the Q value. However, in presbyopic patients, the lens 8 loses its ability to deform and the patient experiences difficulties see nearby objects clearly enough.

Finally, the retina 10 is a neuro-sensory membrane lining the back of the eye 2 and composed of a large number of photoreceptors - called cones and rods - whose role is to convert the light rays received into electrical signals . These electrical signals can then be transmitted to the brain through the optic nerve.

[0062] As explained previously, the lens 8 can, often due to aging, undergo a progressive opacification responsible for a decline in sight and an increased sensitivity to light. This well-known condition - cataract - is cured by replacing the crystalline lens 8 with an intraocular lens.

[0063] The [Fig. 2] thus illustrates an optical diagram of the eye 2 in which the natural lens 8 has been replaced by an intraocular lens 12.

[0064] By comparison with the lens 8 shown in [Fig. 1], it should be noted that the intraocular lens 12 practically comes into contact with the pupil 6. The pupillary diameter makes it possible to identify, in a given state of expansion or contraction of the pupil 6, the part of the intraocular lens 12 stressed and traversed by light rays.

[0065] In the case illustrated in [Fig. 2], the intraocular lens 12 replaces the lens 8. However, the intraocular lens 12 can also be a phakic (or phakic) intraocular lens, in which case the lens 8 is retained. A phakic intraocular lens can be placed in front or behind the pupil 6 and makes it possible to correct certain visual deficiencies, in particular presbyopia. In the context of the invention, the intraocular lens 12 can denote both an intraocular lens replacing the lens 8 and a phakic intraocular lens.

The rest of the description presents the characteristics of the intraocular lens 12 according to the invention which makes it possible to treat both cataracts and presbyopia. This intraocular lens 12 is able to replace the natural lens 8 and to offer a satisfactory depth of field, in particular by improving the resolution for near vision objects.

[0067] First of all, it should be remembered that asphericity, whether for the cornea 4, the lens 8 or the intraocular lens 12, is associated with spherical aberrations. For a lens, we speak of spherical aberration - or aberration of sphericity - when para-axial light rays, therefore parallel to the optical axis of the lens, refracted respectively by a peripheral zone and a central zone of the lens do not not converge on the same plane.

This phenomenon is the consequence of the imperfection of the lens at the output of which the wavefront is not completely flat. We can then define a phase shift with respect to a theoretical perfect lens and approximate it by a combination of Zernike polynomials. In particular, the following Zernike polynomial - called a radial polynomial - corresponds to the spherical aberration:

Furthermore, for a given lens having a refractive index n, the coefficient of the previous Zernike polynomial, in the linear combination of the wavefront phase shift, is zero if the asphericity value Q of the lens is the next one :

[0071] [Math. 9]

Indeed, the following form of the Zernike polynomial coefficient corresponding to spherical aberration can be deduced, among others, from the work of Guang-ming Dai, in particular in the article "Theoretical analysis for spherical aberration induction with low - order correction in refractive surgery” (Applied Optics, vol. 51, No. 18, p. 3966-3976, June 20, 2012):

[0073] [Math. 10]

[0074] where: - n is the refractive index of the lens;

- p is the pupillary radius; And

- Ro is the radius of curvature at the optical center of the lens.

[0075] Consequently, when the asphericity value Q of a lens is equal to the remarkable value −1/n ² , the paraxial light rays converge in the same plane.

When the asphericity value Q of the lens is strictly greater than the remarkable value -1/n ² , the para-axial light rays refracted by the peripheral zone of the lens converge on a plane closer to the lens than para-axial rays refracted by the central zone of the lens. In other words, the peripheral para-axial rays converge in front of the central para-axial rays. We then speak of positive spherical aberrations.

Conversely, when the asphericity value Q of the lens is strictly lower than the remarkable value -1/n ² , the para-axial light rays refracted by the peripheral zone of the lens converge on a plane more away from the lens than the para-axial rays refracted by the central zone of the lens. In other words, the peripheral para-axial rays converge behind the central para-axial rays. We then speak of negative spherical aberrations.

The work of the Applicant led him to take an interest in lenses having an asphericity value Q different from the remarkable value −1/n ² . The Applicant has thus studied the optical performance of lenses having an asphericity value Q that is multiple of the remarkable value -1/n ² , therefore values of asphericity Q of the type -k/n ² , where k is a relative integer.

The Applicant then discovered that a lens having an asphericity value Q equal to -2/n ² has remarkable properties and makes it possible to improve the depth of field and to obtain a much sharper image of a nearby object. These different results are illustrated in [Fig. 3], [Fig. 4], [Fig. 5] and [Fig. 6], and explained below.

[0080] The [Fig. 3] illustrates the formation of a circle of confusion with lenses of distinct asphericities. The first converging lens Li has an asphericity value Q equal to -1/n ² while the second converging lens L2 has an asphericity value Q equal to -2/n ² . For each of these lenses, a light source S has been positioned on the optical axis y of the lens at a distance D corresponding to near vision. Consequently, the light rays coming from the light source S and passing through the peripheral edge of the lens are divergent rays.

[0081] As illustrated in [Fig. 3], the para-axial rays from the light source S converge at the object focal point F of the lens which corresponds to the intersection of the optical axis y and the object focal plane PF of the lens. This principle is the same for the first convergent lens Li and the second convergent lens L2.

The divergent rays coming from the light source S converge, them, in a distinct focal point of the object focal point F - denoted Fi for the first convergent lens Li and F2 for the second convergent lens L2 - which corresponds to the intersection of the optical axis y and of the focal plane PFi for the first convergent lens Li or PF2 for the second convergent lens L2. It can be seen that the focal point F2 is much further from the object focal point F than the focal point Fi.

The first convergent lens Li and the second convergent lens L2 both have a negative asphericity value Q, which means that the radius of curvature varies increasingly from the optical center towards the peripheral edge. The curvature, which is inversely proportional to the radius of curvature, therefore varies in a decreasing manner from the optical center towards the peripheral edge. Consequently, when the value of asphericity Q is negative, the capacity of the converging lens to focus the light rays decreases as these move away from the optical center of the lens. The lower the Q asphericity value, the greater the difference between the lens's ability to to converge the central light rays and the ability of the lens to converge the peripheral light rays.

[0084] The circle of confusion is illustrated in [Fig. 3] for each of the converging lenses Li and L2. The circle of confusion of the first converging lens Li is denoted CCi while the circle of confusion of the second converging lens L2 is denoted CC2. In reality, this is a purely schematic illustration since the circle of confusion is in fact included in the object focal plane PF orthogonal to the optical axis y. The circle of confusion, which in fact designates a luminous disc, corresponds to the projection in the object focal plane PF of the light rays coming from the light source S.

It appears that the circle of confusion CC2 is wider than the circle of confusion CCi and therefore has a lower luminous illumination. This difference in illuminance between the two circles of confusion results in a difference in sharpness for the image of the light source S in the object focal plane PF. In other words, since the circle of confusion CC2 is wider than the circle of confusion CCi, the luminous intensity of the rays coming from the light source S is distributed over a larger surface and the image of the light source S in the object focal plane PF is therefore more easily distinguished. The image of the source S in the object focal plane PF appears much sharper with the second convergent lens L2 than with the first convergent lens Li.

This reduction in the luminous illumination represents a “dilution” of the luminosity. The Applicant thus calls “optics by dilution” the use of an asphericity value Q equal to −2/n ² acting as a bandwidth to filter the divergent rays. Close to this value of asphericity Q, the divergent rays are no longer perceived by the retina 10 because they are too weak and only the paraxial light rays form a particularly well focused point spreading function, therefore a sharp image in the object focal plane PF.

In near vision, it is therefore more advantageous for the intraocular lens 12 to present an asphericity value Q equal to −2/n ² rather than −1/n ² to reduce the luminous illumination of the circle confusion and thus improve the sharpness of the image.

[0088] The Applicant has thus developed an approach that runs counter to what is usually sought for the correction of presbyopia. Until now, the challenge in the field of intraocular lenses was to succeed in making the divergent rays converge closer to the object focal point of the intraocular lens 12, located in the center of the retina 10, to obtain a clear vision of a nearby object. The Applicant here proposes a completely different paradigm in which the intraocular lens 12 has an asphericity and a radius of curvature profile making it possible to "diverge" the divergent rays even more or, to be more precise, to make them converge at a focal point - F2 on [Fig. 3] - furthest from the object focal point - F in [Fig. 3] - where the para-axial rays converge. The resulting circle of confusion - CC2 in [Fig. 3] - thus has lower illumination and the image of an object in the object focal plane is consequently sharper.

[0089] Moreover, even if a very large part of the light rays coming from a close object are divergent and are therefore far from the object focal point of the paraxial rays, at least part of the light rays coming from a object, even close, are para-axial and sufficient to obtain an image in the object focal plane.

The Applicant has carried out a comparative simulation of the performance of the converging lens Li, having an asphericity value Q equal to -1/n ² , and of the converging lens L2, having an asphericity value Q equal to -2/n ² . For each of these converging lenses, the light source S was first positioned at a distance D corresponding to far vision, here D=10m, then to near vision, here D=0.2m, and finally to an intermediate vision, here D=0.5m. For each convergent lens and for each distance, light rays were emitted by the light source S destined for the convergent lens tested. The result of the simulation consisted of recording all the impacts of incident light rays in the object focal plane PF, measuring the distance of each impact from the object focal point F and displaying, in the form of a histogram, the distribution of the impacts. . The result obtained corresponds to a point spread function.

As explained above, the intraocular lens 12 is intended to replace the lens 8 to allow focusing, at the center of the retina 10, of an object in near vision, in intermediate vision or in far vision. In the simulation presented here, the converging lens L2 corresponds to the intraocular lens 12, the light source S corresponds to any object and the object focal point F therefore corresponds to the center of the retina 10.

[0092] The [Fig. 4] illustrates the point spread function obtained in far vision for the lenses L1 and L2. As illustrated in this figure, the convergent lens Li has a peak of less than 20% around the object focal point F, while the convergent lens L2 has a peak close to 40%, which means that the convergent lens L2 has a greater capacity than the convergent lens Li to make the incident light rays converge in distance vision at the object focal point F. It is also observed that the spreading function of the convergent lens Li is more extensive than that of the convergent lens L2 , which means that the impacts of incident light rays farthest from the object focal point F are closer to it for the converging lens L2 than for the converging lens Li.

[0094] The [Fig. 5] illustrates the point spread function obtained in near vision for the Li and L2 lenses.

The histograms obtained in this figure are consistent with [Fig. 3] and the preceding considerations on the circle of confusion. It is observed in particular, for the converging lens L2, that the peaks at approximately 5% are located at the ends of the spreading function, which is not the case for the peaks at approximately 12% for the converging lens Li. moreover, the spreading function obtained for the converging lens L2 is much larger than that obtained for the converging lens Li, which confirms that the converging lens L2 makes it possible to make the divergent incident light rays “diverge” more or more precisely to make them converge at a greater distance from the object focal point F.

[0096] Finally, [Fig. 6] illustrates the point spread function obtained in intermediate vision for the Li and L2 lenses.

The histogram obtained for intermediate vision presents both characteristics that are observed for far vision and characteristics that are observed for near vision. Thus, for the converging lens L2, there is a high peak at the object focal point F and peaks at the ends of the spreading function.

It is therefore particularly advantageous for the intraocular lens 12 to have an asphericity value Q equal to -2/n ² . Such an intraocular lens 12 not only makes it possible to obtain a sharper image of an object in near vision, which is necessary for the correction of presbyopia, but also to obtain better performance in far vision and in vision intermediate. This results in a better depth of field for the patient. [0099] The [Fig. 7] illustrates a system 14 for determining a radius of curvature profile of the intraocular lens 12.

[0100] The system 14 can be made available to a practitioner or a healthcare professional, for example an ophthalmic surgeon, when a patient suffering from cataracts, presbyopia or both must undergo a surgical intervention. for the replacement of the lens 8 of one eye 2 by the intraocular lens 12. Of course, such an operation can also consist of replacing the lens 8 of both eyes of the patient.

The system 14 is configured to determine a profile of the radius of curvature of the intraocular lens 12 suitable both for the correction of cataracts and presbyopia. The radius of curvature profile obtained can then be used to select an intraocular lens 12 that already exists and is ready to be used for the operation. Alternatively, the radius of curvature profile can also be used to fabricate a custom intraocular lens 12.

The system 14 thus makes it possible to implement, at least in part, the method of manufacturing the intraocular lens 12 illustrated in [FIG. 8].

[0103] As illustrated in [Fig. 7], the system 14 comprises an interface 16, a processing unit 18 and a database 20.

The interface 16 is configured to allow the practitioner or healthcare professional to interact with the system 14 to generate a profile of radius of curvature adapted to the patient. The interface 16 is for example a man-machine interface allowing a user to enter the data necessary for the generation of the radius of curvature profile.

The interface 16 can be provided with display means, for example a touch screen or not, and include printing means for printing information relating to the determined radius of curvature profile.

[0106] With reference to [Fig. 8], the interface 16 receives, during an operation 800, ocular biometric measurements of a patient.

[0107] Ocular biometry is a preoperative examination making it possible to calculate the desired power of the intraocular lens 12. This examination results in the measurement of several characteristics of the patient's eye 2, the subsequent use of which, to calculate the power of the intraocular lens 12, depends on the mathematical model used. [0108] As a general rule, the ocular biometric measurements include at least the axial length and the keratometry.

The axial length corresponds to the distance between the anterior face of the cornea 4 and the fovea at the level of the retinal pigment epithelium 10. The anterior face of the cornea 4 designates the face furthest from the pupil 6 On average, the axial length is 23 millimeters (mm). Of course, the axial length may be different from one patient to another, especially in myopic or farsighted patients. It is thus observed that the axial length is higher in myopic patients than in emmetropic patients and that, conversely, the axial length is lower in hypermetropic patients than in emmetropic patients. The axial length is often denoted L.

[0110] Keratometry, often denoted K, makes it possible to quantify the refractive power of the cornea 4. The keratometry can be calculated by measuring the radii of curvature of the anterior surface of the cornea 4 along the two main meridians thereof .

[yes] More generally, the measurements taken in the context of ocular biometrics may relate to corneal topography, for example the toricity, symmetry and asphericity of the cornea 4.

In the context of ocular biometrics, it is also possible to measure the depth of the anterior chamber. The depth of the anterior chamber corresponds to the distance between the epithelium of the cornea 4 and the anterior capsule of the lens 8. The depth of the anterior chamber averages 3.11 millimeters (mm) and varies depending on the ametropia or the patient's age.

The ocular biometric measurements are for example entered, via the interface 16, by the practitioner or the healthcare professional taking part in the operation.

The person skilled in the art understands that ocular biometrics is well known in itself and is not strictly speaking the subject of the present invention. Therefore, the preceding considerations are not exhaustive and ocular biometrics measurements may include other measurements than those cited here.

During an operation 810, the interface 16 receives parameters from the intraocular lens 12 comprising at least one refractive index value n. The refractive index n is indeed necessary since, as explained above, the intraocular lens 12 must have a radius of curvature profile such that it has an asphericity value Q equal to -2/n ² .

[0117] Typically, the material used to manufacture the intraocular lens 12 comprises at least polymethyl methacrylate. This material can be hydrophilic, in which case the refractive index is approximately 1.46, which corresponds to an asphericity value Q approximately equal to -0.938. Alternatively, this material may be hydrophobic, in which case the refractive index is approximately 1.54, which corresponds to an asphericity value Q approximately equal to -0.842. Generally speaking, the refractive index is between 1.46 and 1.54, in which case the target value of asphericity Q is ideally between -0.94 and -0.84.

Furthermore, the practitioner or the healthcare professional can enter other parameters via the interface 16, in particular the constant A which is well known in the field of ocular biometrics. The constant A was introduced during the development of the SRK regression formula - named after its inventors Sanders, Retzlaff and Kraff - and its value, evaluated statistically, is approximately equal to 118. This value can be adjusted by the practitioner or healthcare professional using the system 14 via the interface 16. The SRK regression formula makes it possible to evaluate the power of the intraocular lens 12 as follows:

[0119] [Math. 11]

P = A - 2.5L - 0.9K

[0120] where P is the power of the intraocular lens 12.

[0121] Here again, the person skilled in the art understands that other parameters relating to the desired intraocular lens 12 can be entered via the interface 16.

The processing unit 18 is configured, in general, to determine the characteristics of the desired intraocular lens 12 and, in particular, the radius of curvature profile thereof.

[0123] As illustrated in [Eig. 7], the processing unit 18 comprises a memory 22 and a processor 24.

The memory 22 is configured to store instructions whose implementation, by the processor 24, results in the operation of the processing unit 18. The memory 22 is for example a non-transitory computer-readable storage medium storing the instructions in the form of a computer program

[0125] Referring again to [Fig. 8], the processing unit 18 determines, during an operation 820, a radius of curvature value Ro at the optical center of the desired intraocular lens 12 as a function of the ocular biometric measurements and one or more of the parameters of the intraocular lens 12.

Several mathematical models are likely to be used by the processing unit 18 to determine the value of the radius of curvature Ro at the optical center of the intraocular lens 12. Thus, in addition to the first generation SRK regression formula mentioned above, other formulas - called theoretical - can be used to calculate the power of the desired intraocular lens 12 and deduce therefrom the value of the radius of curvature Ro. The two formulas are in fact linked by the following relationship:

[0127] [Math. 12]

Among these theoretical formulas, mention may in particular be made of the second generation SRK II formula, the third generation SRK T, Holladay and Hoffer Q formulas, the fourth generation Holladay 2 and Haigis formulas or else the Barrett II formula of fifth generation. It should be noted that several of these formulas also take into account the relative position of the intraocular lens 12 with respect to the cornea 4 of the eye 2 of the patient.

During an operation 830, the processing unit 18 determines, as a function of the radius of curvature value Ro at the optical center of the lens, an increasing and continuous radius of curvature profile from the optical center of the desired intraocular lens 12 towards a peripheral edge of the intraocular lens 12 as a function of the distance to the optical axis y of the intraocular lens 12 so that the latter has an asphericity value Q substantially equal to -2/n ² .

[0130] The radius of curvature profile will be discussed below with reference to [Fig. 9] and in [Fig. 10], [0131] By “substantially equal”, it is understood here that, ideally, the value of asphericity Q of the intraocular lens 12 is equal to −2/n ² to obtain the performances presented previously with reference to [FIG. 3], [Fig. 4], [Fig. 5] and [Fig. 6].

However, in practice, it is difficult to achieve exactly the desired asphericity value Q for the intraocular lens 12, in particular because of the inaccuracies inherent in the means and equipment used, whether at the level of the system 14 for the determination of the radius of curvature profile or during the subsequent manufacture of the intraocular lens 12. Advantageously, the asphericity value Q actually achieved by the manufactured intraocular lens 12 deviates by 5% from the ideal value -2/n ² . Preferably, this error percentage is 1%.

Finally, during an operation 840, the intraocular lens 12 is manufactured according to the radius of curvature profile determined by the processing unit 18. Here again, the manufacture of an intraocular lens from a profile radius of curvature is widely known in the field of ophthalmology. The operations of such manufacture are therefore not detailed here, nor are the technical means necessary for the manufacture of the intraocular lens 12.

As explained above, the intraocular lens 12 is for example made of a material comprising at least polymethyl methacrylate.

The database 20 is configured to store information collected or calculated by the processing unit 18. For example, the database 20 can store all or part of a patient's ocular biometric measurements as well as any or part of the parameters of the intraocular lens 12 and the profile of the radius of curvature of the intraocular lens 12. Such information can in particular be useful if the same patient subsequently has to undergo a new surgical intervention.

[0136] In the example illustrated in [Lig. 7], the database 20 is located at the level of the system 14. However, the database 20 can also be remote from the system 14 and be located, for example, at the level of a remote server, for example accessible via a extended network.

The radius of curvature profile, which is the subject of operation 830 in particular, is commented on below with reference to [Lig. 9] and [Lig. 10] which illustrate the variation of the radius of curvature of the intraocular lens 12 from the optical center towards an edge peripheral of the intraocular lens 12 as a function of the distance x to the optical axis y. The radius of curvature profile is here symmetrical with respect to the optical axis y.

The radius of curvature at the optical center of the intraocular lens 12 is denoted Ro, while the radius of curvature at the peripheral edge of the intraocular lens 12 is denoted R _p . The r(x) value of the radius of curvature and the distance x to the optical axis y are in millimeters (mm).

It can be noted that the distance x to the optical axis y of a given point of the intraocular lens 12 can also correspond to a pupillary radius since, as illustrated in [Fig. 2], the intraocular lens 12 almost comes into contact with the pupil 6 and that the axis of symmetry of the latter coincides with the optical axis y of the intraocular lens 12.

Furthermore, the desired power P at the optical center of the intraocular lens 12 is here equal to 23 m ¹ - the diopter (δ) is also used as a unit of equivalent vergence. The refractive index n here is approximately equal to 1.49. It is possible to deduce therefrom approximately the value of the asphericity Q and the radius of curvature Ro at the optical center of the intraocular lens 12.

[0141] [Math. 13]

-2

Q = - - “—0.90

1.49 ²

[0142] [Math. 14]

1.49 - 1

R _o = * 21.3 mm

⁰ 23/1000

The intraocular lens 12 comprises a variable portion over which the radius of curvature is strictly increasing. The variable portion is connected and symmetrical with respect to the optical axis y.

[0144] In the radius of curvature profile illustrated in [Fig. 9], the variable portion covers the intraocular lens 12 entirely. In other words, the intraocular lens 12 has a strictly increasing and continuous radius of curvature from the optical center to the peripheral edge of the intraocular lens 12 as a function of the distance x from the optical axis y. The intraocular lens 12 can also comprise at least one constant portion over which the radius of curvature is substantially constant. Each constant portion is connected and symmetrical with respect to the optical axis y.

[0146] By “substantially constant”, it is understood here that, ideally, the radius of curvature is the same at all points of the constant portion. However, in practice, it is difficult to obtain perfect stability, in particular because of the inaccuracies inherent in the means and equipment used, whether at the level of the system 14 for determining the radius of curvature profile or during subsequent manufacture. of the intraocular lens 12. Advantageously, over a constant portion of the manufactured intraocular lens 12, the radius of curvature value deviates by 5% from the target value. Preferably, this error percentage is 1%.

[0147] In the radius of curvature profile illustrated in [Fig. 10], the intraocular lens 12 comprises a constant portion corresponding to a zone Zi, a variable portion corresponds to a zone Z2 and another constant portion corresponds to a zone Z3. On the contrary, the radius of curvature profile illustrated in [Fig. 9] does not include a constant portion.

The constant portion Zi is a central portion extending from the optical center and over which the distance x to the optical axis y is less than or equal to a first predetermined distance. The first predetermined distance is here approximately equal to 0.75 mm.

The constant portion Z3 is an eccentric portion extending as far as the peripheral edge and over which the distance x to the optical axis y is greater than or equal to a second predetermined distance. The second predetermined distance is here approximately equal to 4.5 mm.

The variable portion Z2 is a portion over which the distance x to the optical axis y is between the first predetermined distance and the second predetermined distance.

On the variable portion, the radius of curvature and the distance x to the optical axis y are for example linked by a polynomial relationship. This polynomial relation is typically of degree 2.

The radius of curvature at a given point of the variable portion can be determined as follows depending on the distance x to the optical axis y: [0153] [Math. 15] r(x) =

[0154] where: - x is the distance from the given point to the optical axis y;

- xi is a predetermined distance;

- r(x) is the radius of curvature at the given point;

- Ro is the radius of curvature at the optical center; And

- a is a constant depending on the asphericity value Q.

When the intraocular lens 12 comprises a variable portion and a constant portion corresponding to a central portion, and the radius of curvature satisfies the previous equation, the predetermined distance xi is equal to the first predetermined distance.

The constant a allows the intraocular lens 12 to reach the target value of asphericity Q by an appropriate increase in the radius of curvature on the variable portion. The constant a is less than or equal to the target asphericity value Q and is therefore strictly negative. The constant a is all the lower in absolute value as the variable portion occupies a large surface of the intraocular lens 12. In other words, the presence of one or more constant portions results in a constant a that is higher in absolute value than in the absence of any constant portion.

[0157] The radius of curvature profile illustrated in [Fig. 9] does not include any constant portion - therefore no constant portion corresponding to a central portion - and is therefore obtained with the following parameters:

[0158] [Math. 16] x ₁ = 0

[0159] [Math. 17] a = Q

The equation verified by the radius of curvature of the intraocular lens 12 is then the following:

[0161] [Math. 18] r(x) =

[0162] Conversely, in the embodiment illustrated in [Fig. 10], the intraocular lens 12 comprises the constant portion Zi and the constant portion Z3. The radius of curvature profile on the variable portion Z2 is obtained with the following parameters:

[0163] [Math. 19] x ₁ > 0

[0164] [Math. 20] a < Q

The constant a is strictly less than the asphericity value Q to compensate for the interruption or delay in progression of the radius of curvature caused by each constant portion. Thus, the constant a of the equation of the radius of curvature of [Fig. 10] is less than that of the radius of curvature equation of [Fig. 9], so as to achieve, at the peripheral edge of the intraocular lens 12, the same value of radius of curvature R _p starting from the same radius of curvature Ro at the optical center of the intraocular lens 12.

The constant a depends on the length of the variable portion, or more precisely on the difference in distance x to the optical axis y between the inner edge of the variable portion, that is to say the edge furthest close to the optical center of the intraocular lens 12, and the outer edge of the variable portion, that is to say the edge furthest from the optical center of the intraocular lens 12.

The constant a is for example calculated as a function of the ratio between the length of the variable portion and the radius of the intraocular lens 12. The radius of the intraocular lens 12 designates here the distance x to the optical axis y of the edge peripheral of the intraocular lens 12. In [Fig. 9] and [Fig. 10], the radius of the intraocular lens 12 is equal to 5 mm.

The constant a can thus be calculated as follows:

[0169] [Math. 21]

where: - p is the radius of the intraocular lens 12; and - 1 is the length of the variable portion. For an intraocular lens 12 optionally comprising a constant portion corresponding to a central portion and/or a constant portion corresponding to an eccentric portion, the constant a can then be calculated as follows:

[0172] [Math. 22]

[0173] where: - xi is the first predetermined distance, which is equal to the predetermined distance of the equation of the radius of curvature on the variable portion; And

- X2 is the second predetermined distance.

[0174] It is noted in particular that, when the intraocular lens 12 does not comprise any constant portion, as illustrated in [Fig. 9], the first predetermined distance is zero and the second predetermined distance is equal to the radius of the intraocular lens 12, so that we find a = Q.

The present invention makes it possible to highlight the ophthalmic performance of an intraocular lens having an asphericity value Q substantially equal to −2/n ² . However, the preceding considerations and results may have applications in fields of optics other than ophthalmology, in particular optical systems involving one or more converging lenses. By way of examples, the teaching of the present invention can be used in the design of a telescope, an optical microscope, an astronomical telescope or even a photographic lens to improve the depth of field. It is then advantageous for each convergent lens of such an optical system (or only part of the convergent lenses) to have an asphericity value Q substantially equal to −2/n ² . In particular, the series association of several coaxial convergent lenses having such characteristics allows filtering of the divergent light rays. Concerning again the field of ophthalmology, a value of asphericity Q substantially equal to −2/n ² can also be advantageous for a contact lens, also called a corneal lens.

Claims

[Claim 1] Intraocular lens (12), having an optical center and an optical axis (y), characterized in that it has an increasing and continuous radius of curvature from the optical center towards a peripheral edge of the intraocular lens (12 ) as a function of the distance (x) to the optical axis (y) so that the intraocular lens (12) has an asphericity value (Q) substantially equal to the following value: [Math. 23]

—2 n ² where n is the refractive index of the intraocular lens (12).

[Claim 2] Intraocular lens (12) according to claim 1, characterized in that it comprises a variable portion (Z2) on which the radius of curvature is strictly increasing, said variable portion being connected and symmetrical with respect to the axis optical (y).

[Claim 3] Intraocular lens (12) according to claim 2, characterized in that the radius of curvature and the distance (x) to the optical axis (y) are related by a polynomial relation on the variable portion.

[Claim 4] Intraocular lens (12) according to Claim 2 or 3, characterized in that the radius of curvature at a given point of the variable portion is determined as follows:

[Math. 24]

where: - x is the distance from the given point to the optical axis (y);

- xi is a predetermined distance;

- r(x) is the radius of curvature at the given point;

- Ro is the radius of curvature at the optical center; And

- a is a constant depending on the asphericity value (Q).

[Claim 5] Intraocular lens (12) according to claim 4, characterized in that the constant a is calculated as follows:

[Math. 25]

where: - p is the radius of the intraocular lens (12); And

- 1 is the length of the variable portion.

[Claim 6] Intraocular lens (12) according to claim 4 or 5, characterized in that the variable portion covers the intraocular lens (12) entirely and in that: [Math. 26] x ₁ = 0

[Math. 27] a = Q where Q is the asphericity value of the intraocular lens (12).

[Claim 7] Intraocular lens (12) according to one of Claims 2 to 5, characterized in that it comprises at least one constant portion over which the radius of curvature is substantially constant, each constant portion being connected and symmetrical with respect to to the optical axis (y).

[Claim s] Intraocular lens (12) according to claim 7, characterized in that a constant portion is a central portion (Zi) extending from the optical center and over which the distance (x) to the optical axis ( y) is less than or equal to a first predetermined distance.

[Claim 9] Intraocular lens (12) according to claim 8 taken in combination with claim 4 or 5, characterized in that the predetermined distance xi is equal to the first predetermined distance.

[Claim 10] Intraocular lens (12) according to one of Claims 7 to 9, characterized in that a constant portion is an eccentric portion (Z3) extending as far as the peripheral edge and over which the distance (x) to the optical axis (y) is greater than or equal to a second predetermined distance.

[Claim 11] Intraocular lens (12) according to one of Claims 7 to 10 taken in combination with Claim 4 or 5, characterized in that:

[Math. 28] a < Q where Q is the asphericity value of the intraocular lens (12). [Claim 12] Intraocular lens (12) according to one of the preceding claims, characterized in that the refractive index (n) is between 1.46 and 1.54 and in that the asphericity has a value ( Q) between -0.94 and -0.84.

[Claim 13] Method for determining a radius of curvature profile of an intraocular lens (12) having an optical center and an optical axis (y), characterized in that it comprises the following operations implemented by a interface (16):

- receiving (800) ocular biometric measurements from a patient;

- receiving (810) parameters of the intraocular lens (12) comprising at least one refractive index value (n); and in that it further comprises the following operations implemented by a processing unit (18):

- determining (820) a radius of curvature value (Ro) at the optical center of the intraocular lens (12) as a function of the ocular biometric measurements and one or more of the parameters of the intraocular lens (12);

- determining (830), as a function of the radius of curvature value at the optical center of the lens, an increasing and continuous radius of curvature profile from the optical center of the desired intraocular lens (12) towards a peripheral edge of said intraocular lens (12) as a function of the distance (x) to the optical axis (y) of said intraocular lens (12) so that the latter has an asphericity value (Q) substantially equal to the following value: [Math . 29]

—2 n ² where n is the refractive index of the intraocular lens (12).

[Claim 14] Computer program comprising instructions for implementing the method according to claim 13, when said instructions are executed by at least one processor (24).

[Claim 15] A method of manufacturing an intraocular lens (12), characterized in that a radius of curvature profile of said intraocular lens (12) is determined according to the method of claim 13, and in that the lens intraocular (12) is fabricated (840) according to this radius of curvature profile.