Intraocular lens with diluted-luminosity optics

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

Description Title: Dilution Optics Intraocular Lens

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

[0002] A cataract is a clouding of the eye's lens that causes a gradual decrease in vision and increased sensitivity to light. Primarily associated with 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 surgically by replacing the clouded lens of the patient's eye with an intraocular lens—or implant. Replacement with an artificial lens is the only solution, as 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 impairments, including myopia, hyperopia, astigmatism, and presbyopia. Generally, in such cases, the natural lens is preserved, so the intraocular lens acts as an additive implant. This is known as phakic implantation. It should be noted that these visual impairments can be treated with laser surgery to reshape the cornea, but some patients have contraindications to such an operation, particularly if they suffer from an autoimmune disease or a corneal condition.

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

[0006] Research in the field of intraocular lenses is still very recent, and in the specific case of combined cataract and presbyopia treatment, current solutions do not provide a satisfactory depth of field. In particular, existing intraocular lenses do not offer a sufficiently sharp image of a near object.

[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 continuously from the optical center to a peripheral edge of the intraocular lens as a function of the distance to the optical axis, such that the intraocular lens has an asphericity value substantially equal to the following value:

[0009] [Math. 1] —2 n2

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

[0011] In one or more embodiments, the intraocular lens 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.

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

[0013] 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] x1= 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 on which the radius of curvature is substantially constant. Each constant portion is connected and symmetrical with respect to the optical axis.

[0022] In one or more embodiments, a constant portion is a central portion extending from the optical center and on which the distance to the optical axis is less than or equal to a first predetermined distance.

[0023] 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 on which the distance to the optical axis is greater than or equal to a second predetermined distance.

[0025] In one or more embodiments:

[0026] [Math. 6] a < Q

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

[0028] 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.

[0029] 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 biometry measurements from a patient; - to receive intraocular lens parameters including at least one refractive index value; and in that it further includes the following operations performed by a processing unit: - determine a radius of curvature value at the optical center of the intraocular lens based on ocular biometry measurements and one or more of the intraocular lens parameters; - determine, as a function of the radius of curvature value 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 towards a peripheral edge of the intraocular lens as a function of the distance to the optical axis of the intraocular lens such that the latter has an asphericity value substantially equal to the following value:

[0030] [Math. 7] —2 n 2

[0031] where n is the refractive index of the intraocular lens.

[0032] The present invention also relates to a computer program comprising instructions for implementing the previous method, when the instructions are executed by at least one processor.

[0033] A non-transient, machine-readable storage medium storing this computer program is also targeted.

[0034] 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.

[0035] The intraocular lens is manufactured, for example, from a material comprising at least polymethyl methacrylate.

[0036] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on 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 crystalline 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 spreading function obtained in distance vision for the lenses of [Fig. 3];

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

[0042] [Fig. 6] illustrates a dot spreading 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 for 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] Figure 1 illustrates an optical diagram of an eye 2. Such a diagram allows the eye 2 to be modeled as a simplified optical system.

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

[0049] The cornea 4 is the transparent anterior part of the eyeball and performs 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 refracting light.

[0050] The corneal profile 4 can be characterized by an asphericity value, often denoted Q in the literature. This Q value reflects the nature of the variation in the radius of curvature from the apex of the cornea 4 to its periphery. The apex 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. On [Fig. 1], the optical axis y of the cornea 4 coincides with the optical axis of the lens 8.

[0051] Thus, when the Q value is strictly negative (Q<0), the radius of curvature of the cornea increases from the apex to the periphery. This is referred to as a prolate profile. Conversely, when the Q value is strictly positive (Q>0), the radius of curvature of the cornea decreases from the apex to the periphery. This is referred to as an oblate profile. Finally, when the Q value is zero (Q=0), the radius of curvature of the cornea is constant. The cornea then has a spherical profile.

[0052] Generally speaking, a prolate or even hyperprolate corneal profile is advantageous as it improves near vision performance. The Applicant has, in fact, worked on this subject by developing a procedure called "advanced isovision," which involves reducing the Q value of asphericity through laser treatment at the periphery of the cornea. This procedure also maintains satisfactory performance for distance vision, since distance vision primarily uses the central part of the cornea, near the apex.

[0053] However, laser surgery may be contraindicated for some patients, particularly those with autoimmune diseases or corneal disorders. For these patients, the only solution is the implantation of an intraocular lens.

[0054] Pupil 6 is a circular opening that, by contracting or dilating, regulates the amount of light entering the eye 2. Pupil 6 can be compared, for example, to the diaphragm used in a camera lens. The diameter of pupil 6 thus varies according to the ambient light.

[0055] In the example illustrated in [Fig. 1], 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 light. In such a case, which corresponds to daytime vision, the diameter of pupil 6 is said to be "photopic". This photopic diameter is denoted here as d p .

[0056] When the ambient light is average, for example at twilight, pupil 6 is in a state of average dilation and its diameter is then described as "mesopic".

[0057] Finally, in the example illustrated in [Fig. 2], 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 pupil 6 is said to be "scotopic." This scotopic diameter is denoted here as d s .

[0058] The lens 8 can be likened to a biconvex lens capable of changing shape to focus an object onto the center of the retina 10 for near, intermediate, or far vision. The action of the ciliary muscle modifies the curvature of the lens 8, notably increasing it significantly to form a clear image of a nearby object on the retina 10. This process is called accommodation.

[0059] 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 to its periphery. The center here can refer to the intersection of the optical axis y of the lens 8 with its external surface, i.e., the convex surface facing the cornea 4, or with its internal surface, i.e., the convex surface facing the retina 10.

[0060] The crystalline lens 8 has a negative asphericity value Q and accommodation consists of further decreasing the Q value. However, in presbyopic patients, the crystalline lens 8 loses its ability to deform and the patient experiences difficulty seeing close objects with sufficient clarity.

[0061] 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 received light rays into electrical signals. These electrical signals can then be transmitted to the brain via the optic nerve.

[0062] As explained previously, the lens of the eye (8) can, often due to aging, undergo progressive clouding, leading to decreased vision and increased sensitivity to light. This well-known condition—cataracts—is treated by replacing the lens with an intraocular lens.

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

[0064] Compared to the lens 8 shown in [Fig. 1], it should be noted that the intraocular lens 12 comes practically into contact with the pupil 6. The pupillary diameter allows identification, in a given state of dilation or contraction of the pupil 6, of the part of the intraocular lens 12 that is stimulated and traversed by light rays.

[0065] In the case illustrated in [Fig. 2], the intraocular lens 12 replaces the crystalline lens 8. However, the intraocular lens 12 can also be a phakic intraocular lens, in which case the crystalline lens 8 is retained. A phakic intraocular lens can be placed in front of or behind the pupil 6 and allows for the correction of certain visual impairments, particularly presbyopia. In the context of the invention, the intraocular lens 12 can refer to either an intraocular lens replacing the crystalline lens 8 or a phakic intraocular lens.

[0066] The following description presents the characteristics of the intraocular lens 12 according to the invention, which allows for the treatment of both cataracts and presbyopia. This intraocular lens 12 is suitable for replacing the natural lens 8 and for providing a satisfactory depth of field, particularly by improving resolution for near objects.

[0067] First, it is important to remember that asphericity, whether in 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, parallel to the optical axis of the lens, refracted respectively by a peripheral and a central zone of the lens, do not converge on the same plane.

[0068] This phenomenon results from an imperfection in the lens, where the wavefront is not perfectly flat. We can then define a phase shift relative to a theoretical perfect lens and approximate this using a combination of Zernike polynomials. In particular, the following Zernike polynomial—known as the radial polynomial—corresponds to spherical aberration:

[0070] Furthermore, for a given lens with 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 as follows:

[0071] [Math. 9]

[0072] Indeed, the following form of the coefficient of the Zernike polynomial corresponding to spherical aberration can be deduced, among other things, 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):

[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] Therefore, 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.

[0076] When the asphericity value Q of the lens is strictly greater than the notable value -1 / n 2The 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. This is referred to as positive spherical aberration.

[0077] Conversely, when the asphericity value Q of the lens is strictly less than the remarkable value -1 / n 2 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. This is referred to as negative spherical aberration.

[0078] The Applicant's work led him to become interested in lenses with an asphericity value Q different from the notable value -1 / n 2 The Applicant thus studied the optical performance of lenses having an asphericity value Q that is a multiple of the remarkable value -1 / n 2 , therefore asphericity values ​​Q of the type -k / n 2 , where k is an integer.

[0079] The Applicant then discovered that a lens with an asphericity value Q equal to -2 / n 2 It has remarkable properties and allows for improved depth of field and 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] Figure 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 was positioned on the optical axis y of the lens at a distance D corresponding to near vision. Consequently, the light rays emanating from the light source S and passing through the peripheral edge of the lens are diverging rays.

[0081] 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.

[0082] 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. We observe that the focal point F2 is much further from the object focal point F than the focal point Fi.

[0083] The first converging lens L1 and the second converging lens L2 both have a negative asphericity value Q, meaning that the radius of curvature increases from the optical center to the peripheral edge. The curvature, which is inversely proportional to the radius of curvature, therefore decreases from the optical center to the peripheral edge. Consequently, when the asphericity value Q is negative, the converging lens's ability to focus light rays decreases as they move away from the lens's optical center. The lower the asphericity value Q, 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 CC1, 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 actually contained within the object focal plane PF, which is orthogonal to the optical axis y. The circle of confusion, which in fact represents a luminous disk, corresponds to the projection onto the object focal plane PF of the light rays emanating from the light source S.

[0085] It appears that the circle of confusion CC2 is larger than the circle of confusion CCi and therefore has a lower illumination. This difference in 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 larger than the circle of confusion CCi, the light intensity of the rays from the light source S is spread over a larger area, 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 Li.

[0086] This decrease in light intensity represents a "dilution" of the brightness. The Applicant thus refers to the use of an asphericity value Q equal to -2 / n as "dilution optics". 2 acting as a bandwidth to filter diverging rays. Near this asphericity value Q, diverging rays are no longer perceived by the retina 10 because they are too weak and only paraxial light rays form a particularly well-focused point spread function, therefore a sharp image in the object focal plane PF.

[0087] For near vision, it is therefore more advantageous for the intraocular lens 12 to have an asphericity value Q equal to -2 / n 2 rather than -1 / n 2 to reduce the light intensity of the circle of confusion and thus improve image sharpness.

[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 has been to succeed in making diverging rays converge. as close as possible to the object focal point of the intraocular lens 12, located at the center of the retina 10, to obtain a clear vision of a nearby object. The Applicant proposes here a completely different paradigm in which the intraocular lens 12 has an asphericity and a radius of curvature profile that allows the diverging rays to be diverged even further, or, more precisely, to converge 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 presents a lower illumination, and the image of an object in the object focal plane is consequently sharper.

[0089] Furthermore, even though a very large part of the light rays from a nearby object are divergent and therefore far from the object focal point of the paraxial rays, at least some of the light rays from an object, even a nearby one, are paraxial and sufficient to obtain an image in the object focal plane.

[0090] The Applicant carried out a comparative simulation of the performance of the converging lens Li, which has an asphericity value Q equal to -1 / n 2 and the converging lens L2, having an asphericity value Q equal to -2 / n 2For each of these converging lenses, the light source S was first positioned at a distance D corresponding to distance vision (here D = 10 m), then at near vision (here D = 0.2 m), and finally at intermediate vision (here D = 0.5 m). For each converging lens and for each distance, light rays were emitted from the light source S towards the converging lens under test. The simulation involved recording all the light rays incident on the object focal plane PF, measuring the distance of each ray to the object focal point F, and displaying the distribution of these ray impacts as a histogram. The resulting image represents a spread function of the focal point.

[0091] As explained previously, the intraocular lens 12 is designed to replace the crystalline lens 8 to allow focusing, at the center of the retina 10, of an object for near, intermediate, 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.

[0092] Figure 4 illustrates the point spread function obtained in distance vision for lenses Li and L2.

[0093] As illustrated in this figure, the converging lens Li exhibits a peak of less than 20% around the object focal point F, while the converging lens L2 exhibits a peak close to 40%. This means that the converging lens L2 has a greater capacity than the converging lens Li to converge incident light rays in distance vision at the object focal point F. We also observe that the spreading function of the converging lens Li is more extensive than that of the converging lens L2, meaning 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 Li.

[0094] Figure 5 illustrates the point spreading function obtained in near vision for lenses Li and L2.

[0095] The histograms obtained in this figure are consistent with [Fig. 3] and the preceding considerations on the circle of confusion. In particular, for the converging lens L2, the peaks at approximately 5% are located at the extremes of the spreading function, which is not the case for the peaks at approximately 12% for the converging lens Li. Furthermore, the spreading function obtained for the converging lens L2 is much broader than that obtained for the converging lens Li, which confirms that the converging lens L2 allows the diverging incident light rays to "diverge" more, or more precisely, to converge at a greater distance from the object focal point F.

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

[0097] The histogram obtained for intermediate vision exhibits characteristics observed for both distance and near vision. For example, for the converging lens L2, there is a high peak at the object focal point F and peaks at the extremes of the spreading function.

[0098] 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 not only provides a sharper image of an object in near vision, which is necessary for presbyopia correction, but also improves performance in distance and intermediate vision. This results in a greater depth of field for the patient.

[0099] Figure 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 healthcare professional, for example an ophthalmic surgeon, when a patient suffering from cataracts, presbyopia or both needs to undergo surgery to replace the lens 8 of one eye 2 with the intraocular lens 12. Of course, such an operation can also consist of replacing the lens 8 of both of the patient's eyes.

[0101] The system 14 is configured to determine a radius of curvature profile for the intraocular lens 12 suitable for both cataract and presbyopia correction. The resulting radius of curvature profile can then be used to select an existing intraocular lens 12 ready for use in the procedure. Alternatively, the radius of curvature profile can also be used to manufacture a custom-made intraocular lens 12.

[0102] System 14 thus makes it possible to implement at least in part the manufacturing process of 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.

[0104] Interface 16 is configured to allow the practitioner or healthcare professional to interact with system 14 to generate a radius of curvature profile tailored to the patient. Interface 16 is, for example, a human-machine interface allowing a user to enter the data necessary to generate the radius of curvature profile.

[0105] The interface 16 may be equipped 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], interface 16 receives, during an operation 800, ocular biometry measurements of a patient.

[0107] Ocular biometry is a preoperative examination used to calculate the desired power of the intraocular lens 12. This examination involves measuring 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] Typically, ocular biometry measurements include at least axial length and keratometry.

[0109] The axial length corresponds to the distance between the anterior surface of the cornea 4 and the fovea at the level of the retinal pigment epithelium 10. The anterior surface of the cornea 4 is the surface furthest from the pupil 6. On average, the axial length is 23 millimeters (mm). Of course, the axial length can vary from one patient to another, particularly in myopic or hyperopic patients. Thus, the axial length is observed to be greater in myopic patients than in emmetropic patients, and conversely, the axial length is less in hyperopic patients than in emmetropic patients. The axial length is often denoted L.

[0110] Keratometry, often denoted K, allows the refractive power of the cornea to be quantified. Keratometry can be calculated by measuring the radii of curvature of the anterior surface of the cornea along its two principal meridians. [yes] More generally, measurements taken in the context of ocular biometry may concern corneal topography, for example toricity, symmetry and asphericity of the cornea 4.

[0112] In ocular biometry, it is also possible to measure the depth of the anterior chamber. The depth of the anterior chamber corresponds to the distance between the corneal epithelium 4 and the anterior capsule of the lens 8. The average depth of the anterior chamber is 3.11 millimeters (mm) and varies depending on the patient's refractive error or age.

[0113] For example, ocular biometric measurements are entered, via interface 16, by the practitioner or healthcare professional involved in the operation.

[0114] Those skilled in the art understand that ocular biometry is well known in itself and is not strictly the subject of the present invention. Therefore, the preceding considerations are not exhaustive, and ocular biometry measurements may include other measurements than those mentioned here.

[0115] During an operation 810, the interface 16 receives parameters from the intraocular lens 12 including at least one refractive index value n.

[0116] 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 / n 2 .

[0117] 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, corresponding to an asphericity Q value of approximately -0.938. Alternatively, this material may be hydrophobic, in which case the refractive index is approximately 1.54, corresponding to an asphericity Q value of approximately -0.842. Generally, the refractive index is between 1.46 and 1.54, in which case the target asphericity Q value is ideally between -0.94 and -0.84.

[0118] Furthermore, the practitioner or healthcare professional can enter other parameters via interface 16, including the A constant, well-known in the field of ocular biometry. The A constant was introduced during the development of the SRK regression formula—named after its inventors Sanders, Retzlaff, and Kraff—and its statistically evaluated value is approximately 118. This value can be adjusted by the practitioner or healthcare professional using system 14 via interface 16. The SRK regression formula allows the power of the intraocular lens 12 to be evaluated 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 interface 16.

[0122] The processing unit 18 is configured, in general, to determine characteristics of the desired intraocular lens 12 and, in particular, its radius of curvature profile.

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

[0124] Memory 22 is configured to store instructions whose implementation by the processor 24 results in the operation of the processing unit 18. 22 is, for example, a computer-readable, non-transient storage medium that stores instructions in the form of a computer program

[0125] With further reference to [Fig. 8], the processing unit 18 determines, during an operation 820, a desired radius of curvature value Ro at the optical center of the intraocular lens 12 based on ocular biometry measurements and one or more of the parameters of the intraocular lens 12.

[0126] Several mathematical models can 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—known as theoretical formulas—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 indeed linked by the following relationship:

[0127] [Math. 12]

[0128] Among these theoretical formulas, we can notably mention the second-generation SRK II formula, the third-generation SRK T, Holladay, and Hoffer Q formulas, the fourth-generation Holladay 2 and Haigis formulas, and 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.

[0129] During operation 830, the processing unit 18 determines, based on the radius of curvature Ro at the optical center of the lens, a continuously increasing 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 from the optical axis y of the intraocular lens 12, such that the latter has an asphericity value Q approximately equal to -2 / n 2 .

[0130] The radius of curvature profile will be discussed below with reference to [Fig. 9] and [Fig. 10],

[0131] By "approximately equal", it is understood here that, ideally, the asphericity value 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].

[0132] However, in practice, it is difficult to achieve precisely the desired asphericity value Q for the intraocular lens 12, particularly due to inaccuracies inherent in the means and equipment used, whether in the system 14 for determining the radius of curvature profile or during the subsequent manufacturing 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 2Preferably, this error percentage is 1%.

[0133] Finally, during operation 840, the intraocular lens 12 is manufactured according to the radius of curvature profile determined by the processing unit 18. Again, the manufacture of an intraocular lens from a radius of curvature profile is widely known in the field of ophthalmology. The operations involved in such a manufacture are therefore not detailed here, nor are the technical means required to manufacture the intraocular lens 12.

[0134] As explained previously, the intraocular lens 12 is for example made of a material comprising at least polymethyl methacrylate.

[0135] 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 biometry measurements 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 can be particularly useful if the same patient subsequently undergoes further surgery.

[0136] In the example illustrated on [Lig. 7], database 20 is located at system 14. However, database 20 can also be located remotely from system 14 and, for example, at a remote server, for example accessible via a wide area network.

[0137] The radius of curvature profile, which is the subject of operation 830, is discussed 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 to 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 symmetrical here with respect to the optical axis y.

[0138] 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 value r(x) of the radius of curvature and the distance x to the optical axis y are in millimeters (mm).

[0139] 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 ray since, as illustrated in [Fig. 2], the intraocular lens 12 comes almost into contact with the pupil 6 and the axis of symmetry of the latter is coincident with the optical axis y of the intraocular lens 12.

[0140] Furthermore, the desired power P at the optical center of the intraocular lens 12 is here equal to 23 m 1 - The diopter (θ) is also used as the unit of equivalent power. The refractive index n is approximately 1.49 here. From this, we can approximately deduce 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

[0143] The intraocular lens 12 includes a variable portion on which the radius of curvature is strictly increasing. The variable portion is connected and symmetrical with respect to the optical y-axis.

[0144] In the radius of curvature profile illustrated in [Fig. 9], the variable portion covers the entire intraocular lens 12. 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 to the optical axis y.

[0145] The intraocular lens 12 may also include at least one constant portion on which the radius of curvature is substantially constant. Each constant portion is connected and symmetrical with respect to the optical y-axis.

[0146] By "substantially constant," it is understood 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, particularly due to inaccuracies inherent in the means and equipment used, whether in the system 14 for determining the radius of curvature profile or during the subsequent manufacturing of the intraocular lens 12. Advantageously, on a constant portion of the manufactured intraocular lens 12, the radius of curvature deviates by 5% from the target value. Preferably, this percentage error 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 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 include a constant portion.

[0148] The constant portion Zi is a central portion extending from the optical center and on 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.

[0149] 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 approximately 4.5 mm here.

[0150] The variable portion Z2 is a portion on which the distance x to the optical axis y is between the first predetermined distance and the second predetermined distance.

[0151] 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 relationship is typically of degree 2.

[0152] 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.

[0155] 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.

[0156] The constant α allows the intraocular lens 12 to achieve the target asphericity Q through an appropriate increase in the radius of curvature on the variable portion. The constant α is less than or equal to the target asphericity Q and is therefore strictly negative. The constant α is lower in absolute value the larger the variable portion occupies on the intraocular lens 12. In other words, the presence of one or more constant portions results in a higher absolute value of the constant α 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 thus obtained with the following parameters:

[0158] [Math. 16] x1= 0

[0159] [Math. 17] a = Q

[0160] The equation satisfied 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] x1> 0

[0164] [Math. 20] a < Q

[0165] The constant a is strictly less than the asphericity value Q to compensate for the interruption or delay in the progression of the radius of curvature caused by each constant portion. Thus, the constant a in the equation for the radius of curvature of [Fig. 10] is less than that in the equation for the radius of curvature 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.

[0166] 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.

[0167] 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. On [Fig. 9] and [Fig. 10], the radius of the intraocular lens 12 is equal to 5 mm.

[0168] The constant a can therefore be calculated as follows:

[0169] [Math. 21]

[0170] where: - p is the radius of the intraocular lens 12; and - 1 is the length of the variable portion.

[0171] 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:

[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] In particular, it is observed that, when the intraocular lens 12 does not include 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.

[0175] The present invention highlights the ophthalmic performance of an intraocular lens having an asphericity value Q approximately equal to -2 / n 2However, the preceding considerations and results may have applications in areas of optics other than ophthalmology, particularly optical systems involving one or more converging lenses. For example, the principles of the present invention can be used in the design of a telescope, an optical microscope, a refractor telescope, or even a photographic lens to improve its depth of field. It is then advantageous for each converging lens in such an optical system (or only some of the converging lenses) to have an asphericity value Q approximately equal to -2 / n 2 In particular, the series arrangement of several coaxial converging lenses with such characteristics allows for the filtering of diverging light rays. Again, in the field of ophthalmology, an asphericity value Q approximately equal to -2 / n 2can also be advantageous for a contact lens, also called a comenic lens.

Claims

Demands

1. Intraocular lens (12), having an optical center and an optical axis (y), characterized in that it has a radius of curvature that increases continuously from the optical center to a peripheral edge of the intraocular lens (12) as a function of the distance (x) to the optical axis (y) such 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).

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 symmetric 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) to the optical axis (y) are related 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: [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).

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.

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: [Math. 26] x1= 0 [Math. 27] a = Q where Q is the asphericity value of the intraocular lens (12).

7. Intraocular lens (12) according to any 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 symmetric with respect to the optical axis (y). [Claims] Intraocular lens (12) according to claim 7, characterized in that a constant portion is a central portion (Zi) extending from the optical center and on 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 any one of claims 7 to 9, characterized in that a constant portion is an eccentric portion (Z3) 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.

11. Intraocular lens (12) according to any 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).

12. Intraocular lens (12) according to any 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. A 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): - receive (800) ocular biometry measurements from a patient; - receive (810) parameters from the intraocular lens (12) comprising at least one refractive index value (n); and further comprising the following operations carried out by a processing unit (18): - determine (820) a value of radius of curvature (Ro) at the optical center of the intraocular lens (12) as a function of ocular biometry measurements and one or more of the parameters of the intraocular lens (12); - determine (830), as a function of the value of the radius of curvature 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) to 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) such that the latter has an asphericity value (Q) substantially equal to the following value: [Math. 29] —2 n 2where n is the refractive index of the intraocular lens (12).

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

15. 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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