Intraocular lens and method of designing the same

Abstract

The present application belongs to the technical field of biological implant, and particularly relates to an intraocular lens and a design method thereof. The intraocular lens comprises an optical part and a haptic, the optical part has an anterior surface and a posterior surface, and the posterior surface is inclined relative to the anterior surface. The anterior surface is designed as an aspheric surface, a plane, a spherical surface or a free-form surface, and the posterior surface is designed as a plane, an aspheric surface, a spherical surface or a free-form surface. The intraocular lens designed by the method of the present application can maintain similar optical performance to the ideal position when the position is out of alignment, and can achieve good optical performance when the eccentricity and the tilt are large.

Description

Technical Field

[0001] This invention belongs to the field of biological implant technology, specifically relating to an artificial lens and its design method. Background Technology

[0002] An intraocular lens (IOL) is an artificial lens used to replace a cloudy lens in the eye. It is suitable for conditions such as cataracts, myopia, and presbyopia. Ideally, the IOL should be centered within the eye. However, due to factors such as eye structure, IOL structure, IOL materials, and surgical techniques, the IOL may deviate from its ideal position post-surgery, resulting in misalignment. The impact of misalignment on post-IOL visual function is multifaceted: aspheric IOLs are more sensitive to deviance or tilt than spherical IOLs; non-rotationally symmetric multifocal IOLs exhibit significant differences in optical quality after deviance and tilt in different directions; and aberration-corrected aspheric IOLs are more sensitive to deviance or tilt than standard aberration-free aspheric IOLs.

[0003] Currently, a few IOLs, through special surface designs, can maintain certain optical performance under different eccentricities and tilts, but their optical performance still differs significantly from that at the ideal position. When the eccentricity or tilt is large, the optical performance of these IOLs will still deteriorate severely.

[0004] In summary, existing intraocular lens designs generally have the following shortcomings:

[0005] (1) When the position is off-center or tilted, the optical performance of the IOL will decrease significantly;

[0006] (2) Even if the IOL can adapt to a certain degree of eccentricity and tilt, its optical performance will still be severely reduced when the eccentricity and tilt are large. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for designing an intraocular lens (IOL). The unique aspect lies in the tilting of the posterior surface of the IOL relative to its anterior surface. This simple tilting of the posterior surface effectively adapts to IOL misalignment. The anterior surface of the optics of the IOL proposed in this invention is an aspherical, planar, spherical, or freeform surface, while the posterior surface is a planar, aspherical, spherical, or freeform surface.

[0008] The technical solution for achieving the objective of this invention is as follows:

[0009] A first aspect of the present invention is to provide an artificial lens comprising an optical portion and a haptic, wherein the anterior surface of the optical portion is an aspherical, planar, spherical, or freeform surface, and the posterior surface is a planar, aspherical, spherical, or freeform surface, wherein the posterior surface is inclined relative to the anterior surface.

[0010] The loops can be C-type loops or other types, and there are two or more, preferably two, distributed at both ends of the optical part to support the optical part.

[0011] Furthermore, the intraocular lens is a monofocal intraocular lens, a multifocal intraocular lens, an extended depth-of-focus intraocular lens, an adjustable intraocular lens, or an astigmatic intraocular lens.

[0012] Furthermore, the artificial lens is located behind or in front of the iris.

[0013] Furthermore, the artificial lens has 1 to 10 optical components.

[0014] A second aspect of the present invention is to provide a method for designing the above-described intraocular lens, comprising the following steps:

[0015] S1 sets the anterior surface of the intraocular lens to be aspherical, planar, spherical, or freeform, and the posterior surface to be planar, aspherical, spherical, or freeform, with no inclination of the posterior surface relative to the anterior surface;

[0016] S2 establishes an aberration evaluation function under non-misalignment conditions, using the quadratic surface coefficient or aspheric surface coefficient of the anterior surface of the intraocular lens as variables to optimize system aberrations;

[0017] S3, under the misalignment state, establishes the aberration field center evaluation function and structural constraints, and optimizes the initial structure by using the tilt of the posterior surface of the intraocular lens relative to the anterior surface as a variable.

[0018] S4 establishes an MTF or aberration evaluation function, and optimizes it using the radius of curvature of the anterior surface of the intraocular lens and its quadratic surface coefficient or aspheric surface coefficient as variables to obtain the final structure.

[0019] Furthermore, the formula for the aberration evaluation function described in S2 is as follows:

[0020] F1(Q3)=w1(W 040 ) 2 +w2(W 131 ) 2

[0021] Where Q3 is the quadratic curvature coefficient of the anterior surface of the intraocular lens, and W... 040 W is the third-order spherical aberration coefficient of the system. 131 These are the three-level coma coefficients of the system, with w1 and w2 being the corresponding weight coefficients.

[0022] Furthermore, the aberration field center evaluation function described in S3 is:

[0023] F2(Q3,ΔADE,ΔBDE)=w3(X131 ) 2 +w4(Y 131 ) 2

[0024] Where Q3 is the quadratic curvature coefficient of the anterior surface of the intraocular lens; ΔADE and ΔBDE are the tilt adjustment amounts of the posterior surface of the intraocular lens, respectively, which are the rotation angles of the posterior surface relative to the anterior surface about the X and Y axes, respectively, conforming to the right-hand rule; X 131 Y 131 These are the coordinates of the coma field center; w3 and w4 are the corresponding weight coefficients.

[0025] Furthermore, the structural constraint formula described in S3 is as follows:

[0026] T x ,T y ≥0.2mm

[0027] Among them, T x T y These represent the minimum thickness of the optical portion of the intraocular lens along the X and Y axes, respectively.

[0028] Furthermore, the MTF evaluation function described in S4 is:

[0029] F3(Q3,R3)=w5(M obj -M) 2

[0030] Among them, M obj is the target value of the modulation transfer function, M is the modulation transfer function value of the optical system, and w5 is the weighting coefficient.

[0031] The advantages of this invention compared to the prior art are as follows:

[0032] 1. The intraocular lens designed by the method of this invention can maintain optical performance similar to that of the ideal position even when misaligned;

[0033] 2. The artificial lens designed by the method of the present invention can achieve good optical performance even when the eccentricity and tilt are large. Attached Figure Description

[0034] Figure 1 It is the definition of a coordinate system;

[0035] Figure 2 This is a schematic diagram of an eye model including an aspheric intraocular lens;

[0036] Figure 3 It is the MTFA (mean value of meridional and sagittal modulation transfer functions) curve of the eye model;

[0037] Figure 2In the diagram: 1 represents the incident light ray, 2 represents the cornea, 3 represents the iris, 4 represents the aqueous humor, 5 represents the aspheric intraocular lens, 6 represents the vitreous body, and 7 represents the retina. Detailed Implementation

[0038] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0039] Studies have shown that aspheric intraocular lenses can correct corneal aberrations in the human eye. Asphericity can generally be represented by the following formula:

[0040]

[0041] Note: c is the curvature of the aspherical reference sphere; Q is the conic constant; r is the radial height; a2, a4, and a6 are multinomial coefficients, with a2 usually taking the value 0.

[0042] An object in three-dimensional space has six degrees of freedom, which means there are six types of misalignment on the optical surface: three types of eccentric misalignment (XDE, YDE, and ZDE) and three types of tilt misalignment (ADE, BDE, and CDE). XDE, YDE, and ZDE represent the translations of the optical surface along the positive x-axis, positive y-axis, and positive z-axis of the local coordinate system of that surface, respectively, while ADE, BDE, and CDE represent the rotations around the positive x-axis, positive y-axis, and positive z-axis, respectively. To be consistent with optical calculation software, the rotation angles (ADE, BDE, and CDE) of this invention follow the right-hand rule. The anterior surface of the aspherical intraocular lens of this invention is rotationally symmetric, so CDE has no effect; the CDE of the posterior surface can be decomposed into ADE and BDE, and ZDE can be reflected in the axial spacing of the optical surface. Therefore, only XDE, YDE, ADE, and BDE are considered here.

[0043] In rotationally symmetric optical systems, due to various factors (such as lens shape, material, wavelength, etc.), light rays passing through optical elements may not be perfectly focused at a single point, resulting in image errors known as aberrations. There are many types of aberrations, common ones including spherical aberration, coma, astigmatism, field curvature, distortion, and chromatic aberration. Seidel was the first to systematically study the geometric aberrations of rotationally symmetric optical systems, while Hopkins provided an expansion of the wave aberrations of rotationally symmetric systems.

[0044]

[0045] Note: H is the field vector, ρ is the pupil vector, Ф is the angle between the two vectors, and W is the aberration coefficient. klm The three subscripts, from left to right, are the field vector length, the pupil vector length, and the power of the cosine of the angle between the two vectors; p, n, and m are integers.

[0046] When 2(p+n+m)=4, there are 5 aberration coefficients, namely W 040 (Ball difference), W 131 (Coma), W 222 (like scattered), W 220 (Scene music) and W 311 (Distortion). For intraocular lenses, we mainly study spherical aberration and coma. Therefore, by using the quadratic surface coefficient of the anterior surface of the intraocular lens as a variable, we can optimize the aberrations of the rotationally symmetric optical system. The aberration constraint formula for the system is as follows:

[0047] F1(Q3)=w1(W 040 ) 2 +w2(W 131 ) 2 (3)

[0048] Where Q3 is the quadratic curvature coefficient of the anterior surface of the intraocular lens, and W... 040 W is the third-order spherical aberration coefficient of the system. 131 These are the three-level coma coefficients of the system, with w1 and w2 being the corresponding weight coefficients.

[0049] When the optical system is misaligned, the effective field of view vector is used. Replacing H with H, we can obtain the wave aberration expression for the misaligned optical system:

[0050]

[0051] When 2(p+n+m)=4, we can obtain the expression for the third-order spherical aberration of the misaligned optical system:

[0052]

[0053] Among them, W 040j Let be the third-order spherical aberration coefficient of the j-th surface.

[0054] From this, we can conclude that third-order spherical aberration is constant across the entire field of view. This is because third-order spherical aberration is proportional to the fourth power of the aperture size and is independent of the field of view size. Since the system's non-rotational symmetry only affects the field-dependent nature of aberrations, third-order spherical aberration is independent of XDE, YDE, ADE, and BDE, and only depends on the axial spacing of the optical elements. Therefore, regarding aberration field center constraints, this invention only focuses on the aberration field center corresponding to third-order coma.

[0055] When 2(p+n+m)=4, we can obtain the expression for the third-order coma of the misaligned optical system:

[0056]

[0057] in,

[0058] Compared to the coma expansion of rotationally symmetric systems, the third-order coma of eccentrically tilted systems has an additional constant that does not change with the size of the field of view. This corresponds to the constant coma in the field of view, which is related to the third-order coma coefficient and the aberration field offset vector σ for each surface. j This means that the third-order coma node (the field point with the smallest coma) of the misaligned system is no longer located at the center of the field of view, but has shifted, the amount of which is determined by the coma field eccentricity vector. The decision is made because the maximum number of nodes that an aberration can have is equal to the power of the field vector of that aberration, so an misaligned optical system will have at most one third-order coma node.

[0059] Since only IOLs are misaligned in the intraocular lens mentioned in this invention, the coordinates of the coma field center within the field of view are as follows:

[0060]

[0061] Where k = 5.5°, representing the kappa angle, which is the angle between the visual axis and the pupil axis of the human eye; and Represent Components in the X and Y directions; X 131 The X and Y coordinates represent the center of the coma field. 131 The Y-coordinate represents the center of the coma field.

[0062] This invention uses the quadratic curvature coefficient of the anterior surface of the intraocular lens and the tilt of the posterior surface relative to the anterior surface as variables to bring the coma field center of the system as close as possible to the center of the field of view, thus allowing the coma distribution of the system to be recorrected. Therefore, the formula for constraining the aberration field center is as follows:

[0063] F2(Q3,ΔADE,ΔBDE)=w3(X 131 ) 2 +w4(Y 131 ) 2 (8)

[0064] Where Q3 is the quadratic curvature coefficient of the anterior surface of the intraocular lens; ΔADE and ΔBDE are the tilt adjustment amounts of the posterior surface of the intraocular lens, specifically the rotation angles of the posterior surface relative to the anterior surface around the X and Y axes, respectively, conforming to the right-hand rule; X 131 Y131 These are the coordinates of the coma field center; w3 and w4 are the corresponding weight coefficients.

[0065] However, the tilt angle between the posterior and anterior surfaces of the intraocular lens cannot be too large; otherwise, the lens edge will be too thin to be processed. Therefore, the structural constraint formula for the intraocular lens is as follows:

[0066] T x ,T y ≥0.2mm(9)

[0067] Among them, T x T y These represent the minimum thickness of the optical portion of the intraocular lens along the X and Y axes, respectively.

[0068] Therefore, based on nodal aberration theory, we obtained the initial structure of the intraocular lens (IOL). Then, using the modulation transfer function (MTF) as a constraint for optimization, we obtained the final structure. The optimization variables are the radius of curvature of the anterior surface of the IOL and its quadratic surface coefficients. The MTF constraint formula is as follows:

[0069] F3(Q3,R3)=w5(M obj -M) 2 (10)

[0070] Among them, M obj is the target value of the modulation transfer function, M is the modulation transfer function value of the optical system, and w5 is the weighting coefficient.

[0071] In this example, the surface shape of the intraocular lens adopts formula (1), the anterior surface is aspherical, and the posterior surface is an inclined plane. The specific design steps are as follows:

[0072] S1 establishes an eye model with corneal spherical aberration and an intraocular lens, with parameters shown in Table 1;

[0073] In the non-disordered state, S2 establishes an aberration evaluation function as shown in formula (3), and optimizes the system aberration by using the quadratic surface coefficient of the anterior surface of the intraocular lens as a variable. The parameters are shown in Table 1, and the weight coefficients are all 1.

[0074] S3 is in the misaligned state, the misalignment of the intraocular lens is XDE=0.3mm, YDE=0.25mm, ADE=-5°, BDE=4°. The aberration field center evaluation function and structural constraints are established as shown in formulas (8) and (9). The initial structure is obtained by using the tilt of the posterior surface of the intraocular lens relative to the anterior surface as a variable. The weight coefficients are all 1.

[0075] S4 uses the radius of curvature of the anterior surface of the intraocular lens and its quadratic surface coefficient as variables to perform MTF optimization, as shown in formula (10), to obtain the final structure, M obj =0.7, the final parameters of the intraocular lens are shown in Table 2, and the weighting coefficient is 1 for all parameters.

[0076] Table 1. Parameters of the eye model with aspheric intraocular lens loaded.

[0077]

[0078] The system wavelength is λ = 543 nm, the entrance pupil diameter is D = 3.4 mm, and the MTF optimized resolution is 100 lp / mm; the incident light is parallel light.

[0079] Table 2 shows the final optimized IOL parameters.

[0080]

[0081] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A method for designing an intraocular lens, characterized in that, The steps are as follows: S1 sets the anterior surface of the intraocular lens to be aspherical, planar, spherical, or freeform, and the posterior surface to be planar, aspherical, spherical, or freeform, with no inclination of the posterior surface relative to the anterior surface; S2 In the non-misaligned state, an aberration evaluation function is established, using the quadratic surface coefficient or aspheric surface coefficient of the anterior surface of the intraocular lens as variables to optimize the system aberrations; S3 In the misaligned state, an aberration field center evaluation function and structural constraints are established, and the initial structure is obtained by optimizing the tilt of the posterior surface of the intraocular lens relative to the anterior surface as a variable. S4 Establish MTF Alternatively, an aberration evaluation function can be used to optimize the final structure by using the radius of curvature of the anterior surface of the intraocular lens and its quadratic surface coefficient or aspheric surface coefficient as variables. The formula for the aberration evaluation function described in S2 is as follows: in, Q 3 is the quadratic curvature coefficient of the anterior surface of the intraocular lens. W 040 It is the third-order spherical aberration coefficient of the system. W 131 It is the system's third-order coma coefficient. w 1 and w 2 represents the corresponding weight coefficients; The aberration field center evaluation function described in S3 is: in, Q 3 is the quadratic curvature coefficient of the anterior surface of the intraocular lens; , These are the posterior surface tilt adjustment amount of the intraocular lens, which is the amount of tilt adjustment of the posterior surface relative to the anterior surface. X , Y The rotation angle of the axis conforms to the right-hand rule; X 131 , Y 131 These are the coordinates of the center of the coma field; w 3 and w 4 represents the corresponding weighting coefficients; The structural constraint formulas described in S3 are as follows: in, T x , T y These represent the optical components of the intraocular lens along... X , Y Minimum thickness of the shaft; S4 states MTF The evaluation function is: in, M obj It is the target value of the modulation transfer function. M The value of the modulation transfer function of the optical system. w 5 is the weighting coefficient.

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