Dilution optic intraocular lens

Abstract

The invention relates to an intraocular lens (12) having an optical center and an optical axis (y). The intraocular lens (12) further has a continuously increasing radius of curvature from the optical center to a peripheral edge of the intraocular lens (12) as a function of the distance from the optical axis (y) such that the intraocular lens (12) has an asphericity value substantially equal to the following value: where n is the refractive index of the intraocular lens (12).

Description

Title of the invention: Intraocular lens with dilution optics

[0001] The field of the invention relates to ophthalmology, and more particularly to intraocular lenses.

[0002] Cataracts are cloudings of the lens of the eye that cause progressive loss of vision and increased sensitivity to light. Primarily linked 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 that cataracts can be treated by surgical intervention consisting of replacing the clouded 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, including 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, particularly if they suffer from an autoimmune disease or a pathology of the cornea.

[0005] The Applicant's work led him to propose, in international application WO 2013 / 110888, an intraocular lens capable of both treating cataracts and correcting 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 allow a satisfactory depth of field to be obtained. In particular, existing intraocular lenses do not provide a sufficiently clear image of an object in near vision.

[0007] The present invention improves the situation.

[0008] In this respect, the present invention relates to an intraocular lens, having an optical center and an optical axis, characterized in that it has a radius of curvature that increases and continues from the optical center towards 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: “2 “2

[0009] where n is the refractive index of the intraocular lens.

[0010] 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.

[0011] The radius of curvature and the distance to the optical axis are for example linked by a polynomial relationship on the variable portion.

[0012] In one or more embodiments, the radius of curvature at a given point of the variable portion is determined as follows: -a^x-

[0013] where: - x is the distance of 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.

[0014] In one or more embodiments, the constant a is calculated as follows: a = Q^ F

[0015] where: - p is the radius of the intraocular lens; and -1 is the length of the variable portion.

[0016] In one or more embodiments, the variable portion covers the intraocular lens in its entirety and: = 0" = Q

[0017] where Q is the asphericity value of the intraocular lens.

[0018] 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.

[0019] 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.

[0020] The predetermined distance Xi is for example equal to the first predetermined distance.

[0021] 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.

[0022] In one or more embodiments: a<2

[0023] where Q is the asphericity value of the intraocular lens.

[0024] 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.

[0025] 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: - receive ocular biometric measurements from a patient; - receiving parameters of the intraocular lens including at least one refractive index value; - determining a radius of curvature value at the optical center of the intraocular lens based on ocular biometry measurements and one or more of the parameters of the intraocular lens; - determining, as a function of the curvature radius value at the optical center of the lens, a continuous increasing curvature radius profile from the optical center of the desired intraocular lens to a peripheral edge of the intraocular lens as a function of the distance from the optical axis of the intraocular lens so that the latter has an asphericity value substantially equal to the following value: -2 ri2

[0026] where n is the refractive index of the intraocular lens.

[0027] The present invention also relates to a computer program comprising instructions for implementing the preceding method, when the instructions are executed by at least one processor.

[0028] A non-transitory computer-readable storage medium storing this computer program is also contemplated.

[0029] Finally, the present invention further relates to a method for 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 intraocular lens is manufactured according to this radius of curvature profile.

[0030] The intraocular lens is manufactured for example from a material comprising at least polymethyl methacrylate.

[0031] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0032] [Fig.l] illustrates an optical diagram of an eye;

[0033] [Fig.2] illustrates an optical diagram of the eye of [Fig.l] in which the lens natural has been replaced by an intraocular lens according to the invention;

[0034] [Fig.3] illustrates the formation of a circle of confusion with lenses of asphericities distinct;

[0035] [Fig.4] illustrates a point spread function obtained in distance vision for the lenses of [Fig.3];

[0036] [Fig.5] illustrates a point spread function obtained in near vision for the lenses of [Fig.3];

[0037] [Fig.6] illustrates a point spread function obtained in intermediate vision for the lenses of [Fig.3];

[0038] [Fig.7] illustrates a system for determining a curvature radius profile of a intraocular lens according to the invention;

[0039] [Fig.8] illustrates a method of manufacturing an intraocular lens according to the invention;

[0040] [Fig.9] illustrates an embodiment of the lens curvature radius profile in traocular according to the invention; and

[0041] [Fig. 10] illustrates another embodiment of the radius of curvature profile of the intraocular lens according to the invention.

[0042] [Fig.l] 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.

[0043] As illustrated in [Fig.l], the eye 2 comprises a cornea 4, a pupil 6, a lens 8 and a retina 10.

[0044] The cornea 4 is the transparent anterior part of the eyeball and fulfills the function of transmitting and refracting light. Indeed, the cornea 4, comparable to a converging lens, allows incident light rays to converge towards the crystalline lens 8 which plays a complementary role in the refraction of light.

[0045] The profile of the cornea 4 can be characterized by an asphericity value, often noted Q in the literature. This value Q reflects the nature of the variation in the radius of curvature from the apex of the cornea 4 towards its periphery. The apex corresponds to the intersection of the optical axis y of the cornea 4 with its external surface, i.e. the surface furthest from the pupil 6. In [Fig.l], the optical axis y of the cornea 4 merges with the optical axis of the lens 8.

[0046] Thus, when the value Q is strictly negative (Q<0), the radius of curvature of the cornea 4 increases from the apex towards the periphery. This is called a prolate profile. Conversely, when the value Q is strictly positive (Q>0), the radius of curvature of the cornea 4 decreases from the apex towards the periphery. This is called 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.

[0047] Generally speaking, a prolate or even hyper-prolate profile is advantageous since it allows for improved visual performance in near vision. Applicant has also worked on the subject by developing a process, called "advanced isovision", consisting of reducing, by laser treatment on the periphery of the cornea 4, the Q value of the asphericity. This process also makes it possible to maintain satisfactory performance for distance vision since this mainly uses the central part of the cornea 4, near the apex.

[0048] However, laser surgery may be contraindicated for certain patients, particularly those with autoimmune disease or corneal pathology. For these patients, the only solution is the implantation of an intraocular lens.

[0049] The pupil 6 is a circular orifice which, by its contraction or dilation, allows the quantity of light entering the eye 2 to be regulated. The pupil 6 can for example be compared to the diaphragm used in a photographic lens. The diameter of the pupil 6 thus varies depending on the ambient brightness.

[0050] In the example illustrated in [Fig.l], the pupil 6 is shown in a state of maximum contraction, achieved by stimulation of the circular fibers of the iris, in response to high ambient brightness. In such a case, which corresponds to daytime vision, the diameter of the pupil 6 is said to be “photopic”. This photopic diameter is noted here d p-

[0051] When the ambient brightness is average, for example at dusk, the pupil 6 is in a state of average dilation and its diameter is then described as “mesopic”.

[0052] 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 noted here ds.

[0053] The crystalline lens 8 can be likened to a biconvex lens capable of deforming to enable the focusing, at the center of the retina 10, of an object in near vision, intermediate vision or distance vision. It is the action of the ciliary muscle which makes it possible to modify the curvature of the crystalline lens 8 and in particular to increase it significantly to form a clear image of a close object on the retina 10. This is called accommodation.

[0054] Like the cornea 4, the profile of the lens 8 can be characterized by an asphericity value, also noted Q, which again reflects the nature of the variation in the radius of curvature from the center of the lens 8 toward 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 to say the convex surface facing the retina 10.

[0055] The 8-lens has a negative Q asphericity value and accommodation consists of further reducing the Q value. However, in presbyopic patients, the 8-lens loses its ability to deform and the patient has difficulty seeing close objects sufficiently clearly.

[0056] 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 by the optic nerve.

[0057] As explained above, the crystalline lens 8 can, often due to aging, undergo progressive opacification responsible for a decrease in vision and increased sensitivity to light. This well-known condition - cataract - is treated by replacing the crystalline lens 8 with an intraocular lens.

[0058] [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.

[0059] By comparison with the crystalline lens 8 shown in [Fig. 1], it should be noted that the intraocular lens 12 practically comes into contact with the pupil 6. The pupil diameter makes it possible to identify, in a given state of dilation or contraction of the pupil 6, the part of the intraocular lens 12 stressed and crossed by light rays.

[0060] In the case illustrated in [Fig.2], the intraocular lens 12 replaces the crystalline lens 8. However, the intraocular lens 12 may also be a phakic (or phakic) intraocular lens, in which case the crystalline lens 8 is retained. A phakic intraocular lens may be placed in front of 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 may designate both an intraocular lens replacing the crystalline lens 8 and a phakic intraocular lens.

[0061] The remainder 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 capable of replacing the natural crystalline lens 8 and of offering a satisfactory depth of field, in particular by improving the resolution for objects in near vision.

[0062] First of all, it should be recalled that asphericity, whether for the cornea 4, the crystalline 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 paraxial 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 converge on the same plane.

[0063] This phenomenon is the consequence of the imperfection of the lens at the exit from which the wavefront is not completely flat. We can then define a phase shift relative to a theoretical perfect lens and approximate it by a combination of Zernike polynomials. In particular, the following Zernike polynomial - called the radial polynomial - corresponds to the spherical aberration: ^(p) = 6p4-6p2 + 1

[0064] Furthermore, for a given lens having a refractive index n, the coefficient of the preceding Zernike polynomial, in the linear combination of the phase shift of the wavefront, is zero if the asphericity value Q of the lens is as follows:

[0065] Indeed, the following form of the coefficient of the Zernike polynomial corresponding to spherical aberration can be deduced, among others, from the work of Guang-ming Dai, notably 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): 4” 48^

[0066] 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.

[0067] Therefore, when the asphericity value Q of a lens is equal to the remarkable value -1 / n2, the paraxial light rays converge in the same plane.

[0068] When the asphericity value Q of the lens is strictly greater than the remarkable value -1 / n2, the paraxial light rays refracted by the peripheral zone of the lens converge on a plane closer to the lens than the paraxial rays refracted by the central zone of the lens. In other words, the peripheral paraxial rays converge in front of the central paraxial rays. We then speak of positive spherical aberrations.

[0069] Conversely, when the asphericity value Q of the lens is strictly less than the remarkable value -1 / n2, the paraxial light rays refracted by the peripheral zone of the lens converge on a plane further from the lens than the paraxial rays refracted by the central zone of the lens. In other words, the peripheral paraxial rays converge behind the central paraxial rays. We then speak of negative spherical aberrations.

[0070] The Applicant's work led him to become interested in lenses having an asphericity value Q different from the remarkable value -1 / n2. The Applicant thus studied the optical performances of lenses having an asphericity value Q multiple of the remarkable value -1 / n2, therefore asphericity values ​​Q of the type -k / n2, where k is a relative integer.

[0071] The Applicant then discovered that a lens having an asphericity value Q equal to -2 / n2 has remarkable properties and makes it possible to improve the depth of field and to obtain a much sharper image of a close object. These different results are illustrated in [Fig.3], [Fig.4], [Fig.5] and [Fig.6], and explained below.

[0072] [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 / n2 while the second converging lens L2 has an asphericity value Q equal to -2 / n2. 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 diverging rays.

[0073] As illustrated in [Fig.3], the paraxial 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 converging lens Li and the second converging lens L2.

[0074] The diverging rays from the light source S converge at a focal point distinct from the object focal point F - denoted Fi for the first converging lens Li and F2 for the second converging lens L2 - which corresponds to the intersection of the optical axis y and the focal plane PFi for the first converging lens Li or PF2 for the second converging lens L2. It can be seen that the focal point F2 is much further from the object focal point F than the focal point Fb

[0075] Both the first converging lens Li and the second converging lens L2 have a negative asphericity value Q, meaning that the radius of curvature varies increasingly from the optical center to the peripheral edge. The curvature, which is inversely proportional to the radius of curvature, therefore varies decreasingly from the optical center to the peripheral edge. Therefore, when the asphericity value Q is negative, the ability of the converging lens to focus the light rays decreases as they move away from the optical center of the lens. The lower the asphericity value Q, the greater the difference between the ability of the lens to converge the central light rays and the ability of the lens to converge the peripheral light rays.

[0076] 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 disk, corresponds to the projection in the object focal plane PF of the light rays coming from the light source S.

[0077] 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 luminous illumination 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 converging lens L2 than with the first converging lens Lp.

[0078] This reduction in the luminous illumination represents a “dilution” of the brightness. The Applicant thus calls “dilution optics” the use of an asphericity value Q equal to -2 / n2 acting as a bandwidth to filter the divergent rays. Near this asphericity value 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 spread function, therefore a sharp image in the object focal plane PF.

[0079] In near vision, it is therefore more advantageous for the intraocular lens 12 to have an asphericity value Q equal to -2 / n2 rather than -1 / n2 to reduce the luminous illumination of the circle of confusion and thus improve the sharpness of the image.

[0080] The Applicant has thus developed an approach that goes against the grain of what is usually sought for the correction of presbyopia. Until now, the challenge in the field of intraocular lenses was to succeed in converging the diverging rays as close as possible to the object focal point of the intraocular lens 12, located at the center of the retina 10, to obtain clear vision of a close object. The Applicant proposes here 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 diverging rays even more or, to be more precise, to converge them at a focal point - F2 in [Fig. 3] - further from the object focal point - F in [Fig. 3] - where the paraxial 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.

[0081] Furthermore, even if a very large part of the light rays coming from a nearby 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 an object, even a nearby one, are paraxial and sufficient to obtain an image in the object focal plane.

[0082] The Applicant carried out a comparative simulation of the performances of the converging lens Lb having an asphericity value Q equal to -1 / n2, and of the converging lens L2, having an asphericity value Q equal to -2 / n2. For each of these converging lenses, the light source S was positioned first at a distance D corresponding to far vision, here D=10m, then to near vision, here D=0.2m, and finally to intermediate vision, here D=0.5m. For each converging lens and for each distance, light rays were emitted by the light source S to the converging 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 to 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.

[0083] As explained previously, the intraocular lens 12 is intended to replace the crystalline lens 8 to allow the focusing, at the center of the retina 10, of an object in near vision, intermediate vision or 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.

[0084] [Fig.4] illustrates the point spread function obtained in distance vision for the Li and L2 lenses.

[0085] As illustrated in this figure, the converging lens Li has a peak less than 20% around the object focal point F, while the converging lens L2 has a peak close to 40%, which means that the converging lens L2 has a greater capacity than the converging lens Li to converge the incident light rays in far vision to the object focal point F. It is also observed that the spreading function of the converging lens Li is more extensive than that of the converging lens L2, which means that the impacts of incident light rays furthest from the object focal point F are closer to it for the converging lens L2 than for the converging lens Lh.

[0086] [Fig.5] illustrates the point spread function obtained in near vision for the Li and L2 lenses.

[0087] The histograms obtained in this figure are consistent with [Fig.3] and the previous considerations on the circle of confusion. We observe 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 around 12% for the converging lens Lh. Furthermore, the spreading function obtained for the converging lens L2 is much more extensive than that obtained for the converging lens LH, which confirms that the converging lens L2 makes it possible to "diverge" the diverging incident light rays more or more precisely to make them converge at a greater distance from the object focal point F.

[0088] Finally, [Fig.6] illustrates the point spread function obtained in intermediate vision for the lenses Li and L2.

[0089] The histogram obtained for intermediate vision presents both characteristics observed for distance vision and characteristics observed for near vision. Thus, for the converging lens L2, we find a high peak at the object focal point F and peaks at the ends of the spread function.

[0090] It is therefore particularly advantageous for the intraocular lens 12 to have an asphericity value Q equal to -2 / n2. 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 distance vision and intermediate vision. This results in a better depth of field for the patient.

[0091] [Fig.7] illustrates a system 14 for determining a radius of curvature profile of the intraocular lens 12.

[0092] The system 14 may be made available to a practitioner or healthcare professional, for example an ophthalmic surgeon, when a patient suffering from cataracts, presbyopia or both must undergo surgery for the replacement of the lens 8 of one eye 2 with the intraocular lens 12. Of course, such an operation may also consist of replacing the lens 8 of both eyes of the patient.

[0093] The system 14 is configured to determine a radius of curvature profile of the intraocular lens 12 suitable for both cataract and presbyopia correction. The obtained radius of curvature profile can then be used to select an intraocular lens 12 already existing and ready to be used for the operation. Alternatively, the radius of curvature profile can also be used to manufacture a custom-made intraocular lens 12.

[0094] The system 14 thus makes it possible to implement at least in part the manufacturing method of the intraocular lens 12 illustrated in [Fig.8].

[0095] As illustrated in [Fig.7], the system 14 comprises an interface 16, a processing unit 18 and a database 20.

[0096] The interface 16 is configured to allow the practitioner or healthcare professional to interact with the system 14 to generate a curvature radius profile adapted to the patient. The interface 16 is, for example, a human-machine interface allowing a user to enter the data necessary for generating the curvature radius profile.

[0097] The interface 16 may be provided with display means, for example a touch screen or not, and include printing means for printing information relating to the determined curvature radius profile.

[0098] With reference to [Fig.8], the interface 16 receives, during an operation 800, ocular biometric measurements from a patient.

[0099] Ocular biometry is a preoperative examination for calculating 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, for calculating the power of the intraocular lens 12, depends on the mathematical model used.

[0100] Typically, ocular biometry measurements include at least axial length and keratometry.

[0101] 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 can be different from one patient to another, in particular in myopic or hyperopic patients. It is thus observed that the axial length is greater in myopic patients than in emmetropic patients and that, conversely, the axial length is shorter in hyperopic patients than in emmetropic patients. The axial length is often noted L.

[0102] Keratometry, often noted K, makes it possible to quantify the refractive power of the cornea 4. Keratometry can be calculated by measuring the radii of curvature of the anterior face of the cornea 4 along its two principal meridians.

[0103] More generally, the measurements carried out within the framework of ocular biometry may concern the corneal topography, for example the toricity, the symmetry and the asphericity of the cornea 4.

[0104] In ocular biometry, it is also possible to measure the anterior chamber depth. The anterior chamber depth corresponds to the distance between the corneal epithelium 4 and the anterior lens capsule 8. The anterior chamber depth is on average 3.11 millimeters (mm) and varies depending on the ametropia or age of the patient.

[0105] The ocular biometric measurements are for example entered, via the interface 16, by the practitioner or health professional taking part in the operation.

[0106] Those skilled in the art understand that ocular biometrics is well known in itself- itself and is not strictly speaking the subject of the present invention. Consequently, the preceding considerations are not exhaustive and the ocular biometric measurements may include other measurements than those cited here.

[0107] During an operation 810, the interface 16 receives parameters of the intraocular lens 12 comprising at least one refractive index value n.

[0108] The refractive index n is indeed necessary since, as explained previously, the intraocular lens 12 must have a radius of curvature profile such that it has an asphericity value Q equal to -2 / n2.

[0109] Typically, the material used to manufacture the intraocular lens 12 comprises at least polymethyl methacrylate. This material may 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, the refractive index is between 1.46 and 1.54, in which case the target asphericity value Q is ideally between -0.94 and -0.84.

[0110] Furthermore, the practitioner or healthcare professional can enter other parameters via the interface 16, in particular the constant A 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: P = A-2.5L-(W

[0111] where P is the power of the intraocular lens 12.

[0112] Again, those skilled in the art will understand that other parameters relating to the desired intraocular lens 12 may be entered via the interface 16.

[0113] The processing unit 18 is configured, in a general manner, to determine characteristics of the desired intraocular lens 12 and, in particular, the radius of curvature profile thereof.

[0114] As illustrated in [Fig.7], the processing unit 18 comprises a memory 22 and a processor 24.

[0115] 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 storage medium readable by computer storing the instructions in the form of a computer program.

[0116] Referring again to [Fig.8], the processing unit 18 determines, during a operation 820, a value of radius of curvature Ro at the optical center of the intraocular lens 12 desired as a function of the ocular biometry measurements and one or more of the parameters of the intraocular lens 12.

[0117] 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 desired power of the intraocular lens 12 and deduce the value of the radius of curvature Ro. The two formulas are in fact linked by the following relationship: p

[0118] Among these theoretical formulas, we can notably cite 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 the fifth generation Barrett II formula. 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 patient's eye 2.

[0119] 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, a profile of increasing and continuous radius of curvature 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 from the optical axis y of the intraocular lens 12 so that the latter has an asphericity value Q substantially equal to -2 / n2.

[0120] The curvature radius profile will be discussed below with reference to [Fig.9] and [Fig.10],

[0121] By "substantially equal", it is understood here that, ideally, the asphericity value Q of the intraocular lens 12 is equal to -2 / n2 to obtain the performances presented previously with reference to [Fig.3], [Fig.4], [Fig.5] and [Fig.6].

[0122] However, in practice, it is difficult to exactly achieve the desired asphericity value Q for the intraocular lens 12, in particular due to 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 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 / n2. Preferably, this percentage error is 1%.

[0123] Finally, during an operation 840, the intraocular lens 12 is manufactured according to the curvature radius profile determined by the processing unit 18. Here again, the fa The fabrication of an intraocular lens from a curvature radius profile is widely known in the field of ophthalmology. The operations of such fabrication are therefore not detailed here, nor are the technical means necessary for the fabrication of the intraocular lens 12.

[0124] As explained previously, the intraocular lens 12 is for example manufactured from a material comprising at least polymethyl methacrylate.

[0125] The database 20 is configured to store information collected or calculated by the processing unit 18. For example, the database 20 may store all or part of the ocular biometric measurements of a patient as well as all or part of the parameters of the intraocular lens 12 and the radius of curvature profile of the intraocular lens 12. Such information may in particular be useful if the same patient is subsequently required to undergo a new surgical procedure.

[0126] In the example illustrated in [Fig.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 wide area network.

[0127] The radius of curvature profile, which is notably the subject of operation 830, is commented on below with reference to [Fig.9] and [Fig. 10] which illustrate the variation of the radius of curvature of the intraocular lens 12 from the optical center towards a peripheral edge of the intraocular lens 12 as a function of the distance x from the optical axis y. The radius of curvature profile is here symmetrical with respect to the optical axis y.

[0128] 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 Rp. The value r(x) of the radius of curvature and the distance x to the optical axis y are in millimeters (mm).

[0129] It may be noted that the distance x to the optical axis y of a given point of the intraocular lens 12 may 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 the axis of symmetry of the latter coincides with the optical axis y of the intraocular lens 12.

[0130] Furthermore, the desired power P at the optical center of the intraocular lens 12 is here equal to 23 m1 - the diopter (Å) is also used as the equivalent vergence unit. The refractive index n is here approximately equal to 1.49. From this, the value of the asphericity Q and the radius of curvature Ro at the optical center of the intraocular lens 12 can be approximately deduced:

[0131] 2 = ^«-0.90 1.49"

[0132] d _ MM 3 Ao- 23 / 1000 ~ - L? mm

[0133] The intraocular lens 12 comprises a variable portion on which the radius of curvature is strictly increasing. The variable portion is connected and symmetrical with respect to the optical axis y.

[0134] In the radius of curvature profile illustrated in [Fig.9], the variable portion covers the intraocular lens 12 in its entirety. 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.

[0135] The intraocular lens 12 may 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.

[0136] By “substantially constant” it is meant here that, ideally, the radius of curvature is the same at every point of the constant portion. However, in practice, it is difficult to obtain perfect stability, in particular due to 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 the subsequent manufacture of the intraocular lens 12. Advantageously, on a constant portion of the manufactured intraocular lens 12, the radius of curvature value deviates by 5% from the target value. Preferably, this percentage error is 1%.

[0137] In the radius of curvature profile illustrated in [Fig. 10], the intraocular lens 12 comprises a constant portion corresponding to a zone Zb, a variable portion corresponding to a zone Z2 and another constant portion corresponding to a zone Z3. In contrast, the radius of curvature profile illustrated in [Fig. 9] does not comprise a constant portion.

[0138] 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.

[0139] The constant portion Z3 is an eccentric portion extending to the peripheral edge and on 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.

[0140] 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.

[0141] On the variable portion, the radius of curvature and the distance x to the optical axis y are for example linked by a polynomial relation. This polynomial relation is typically of degree 2.

[0142] The radius of curvature at a given point of the variable portion can be determined as follows as a function of the distance x from the optical axis y: F0 = ^R02 - a*(x - xj2

[0143] Or : - 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.

[0144] 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 preceding equation, the predetermined distance Xi is equal to the first predetermined distance.

[0145] The constant a allows the intraocular lens 12 to reach the target asphericity value Q by an appropriate growth of 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 area of ​​the intraocular lens 12. In other words, the presence of one or more constant portions results in a constant a higher in absolute value than in the absence of any constant portion.

[0146] 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:

[0147]

[0148]

[0149] The equation verified by the radius of curvature of the intraocular lens 12 is then the following:

[0150] 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:

[0151]

[0152]

[0153] The constant a is strictly less than the asphericity value Q to compensate the interruption or delay in the 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 equation of the radius of curvature of [Fig.9], so as to reach, at the peripheral edge of the intraocular lens 12, the same value of radius of curvature Rp starting from the same radius of curvature Ro at the optical center of the intraocular lens 12.

[0154] 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, i.e. the edge closest to the optical center of the intraocular lens 12, and the outer edge of the variable portion, i.e. the edge furthest from the optical center of the intraocular lens 12.

[0155] 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 here designates the distance x to the optical axis y of the peripheral edge of the intraocular lens 12. In [Fig.9] and [Fig. 10], the radius of the intraocular lens 12 is equal to 5 mm.

[0156] The constant a can thus be calculated as follows:

[0157] where: - p is the radius of the intraocular lens 12; and -1 is the length of the variable portion.

[0158] For an intraocular lens 12 possibly 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:

[0159] 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.

[0160] 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.

[0161] The present invention makes it possible to highlight the ophthalmic performances of an intraocular lens having an asphericity value Q substantially equal to -2 / n2. However, the preceding considerations and results may have applications in fields of optics other than ophthalmology, in particular systems optics involving one or more converging lenses. As 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 objective to improve the depth of field. It is then advantageous for each converging lens of such an optical system (or only part of the converging lenses) to have an asphericity value Q substantially equal to -2 / n2. In particular, the series association of several coaxial converging lenses having such characteristics allows filtering of diverging light rays. Concerning again the field of ophthalmology, an asphericity value Q substantially equal to -2 / n2 can also be advantageous for a contact lens, also called a corneal lens.

Claims

Claims

1. Intraocular lens (12), having an optical center and an optical axis (y), characterized in that it has a radius of curvature increasing and continuously from the optical center towards a peripheral edge of the intraocular lens (12) as a function of the distance (x) from the optical axis (y) so that the intraocular lens (12) has an asphericity value (Q) substantially equal to the following value: H2 where n is the refractive index of the intraocular lens (12).

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 optical axis (y).

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

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: r(x) -^^-^(x-xj2 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).

5. Intraocular lens (12) according to claim 4, characterized in that the constant a is calculated as follows: where: - p is the radius of the intraocular lens (12); and -1 is the length of the variable portion.

6. Intraocular lens (12) according to claim 4 or 5, characterized in that the variable portion covers the intraocular lens (12) in its entirety and in that: X! = 0 a = Q where Q is the asphericity value of the intraocular lens (12).

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

8. 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.

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.

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

11. Intraocular lens (12) according to one of claims 7 to 10 taken in combination with claim 4 or 5, characterized in that: a< Q where Q is the asphericity value of the intraocular lens (12).

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.

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 an interface (16): - receiving (800) ocular biometry measurements of 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 biometry measurements and one or more of the parameters of the intraocular lens (12) traocular (12); - determining (830), as a function of the curvature radius value at the optical center of the lens, a continuous and increasing curvature radius 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) from the optical axis (y) of said intraocular lens (12) so that the latter has an asphericity value (Q) substantially equal to the following value: where n is the refractive index of the intraocular lens (12).

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

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 intraocular lens (12) is manufactured (840) according to this radius of curvature profile.

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