A fully free-viewing astigmatism correcting intraocular lens

Abstract

This application relates to intraocular lenses (IOLs) in medical devices, specifically to a fully free-form astigmatism correction IOL. This IOL comprises an optical portion and a mechanical portion. One surface of its optical portion is a fully free-form surface, and the other surface is spherical or aspherical. The fully free-form surface is customized using an irregular xy polynomial based on the patient's corneal astigmatism value. This invention allows for free adjustment of various types of astigmatism, achieving full optical surface aberration adjustment, and providing customized IOLs for astigmatism patients. This invention addresses the limitations of traditional astigmatism lenses, solving the problem of residual astigmatism in patients with irregular astigmatism due to the asymmetrical distribution of irregular astigmatism angles, and achieving astigmatism correction at fully free angles on the optical surface.

Description

Technical Field

[0001] This application relates to intraocular lenses in medical devices, specifically to a fully free-astigmatism correcting intraocular lens. Background Technology

[0002] Astigmatism is a common refractive error caused by irregular curvature of the cornea or lens of the eye, preventing light from forming a single focal point on the retina and instead creating multiple focal points or focal lines. This causes blurred vision, double vision, or distorted vision, especially noticeable when viewing fine lines or objects with low contrast. Astigmatism can exist alone or be associated with myopia or hyperopia. The causes of astigmatism are mainly divided into two categories: congenital and acquired. Congenital factors may include a slight irregularity in the shape of the cornea or lens at birth, which may change with age. Acquired astigmatism may be caused by eye trauma, corneal diseases, long-term poor eye habits, or eyelid pressure. Post-cataract surgery astigmatism correction is mainly used to correct irregular curvature of the cornea. If a patient with astigmatism does not have an astigmatism-correcting intraocular lens implanted after the natural lens is emulsified and removed, it will cause great visual distress for the patient after surgery: blurred or distorted vision at both near and far distances; eye fatigue and headaches (especially after prolonged use of the eyes); and decreased night vision (such as glare or ghosting when driving).

[0003] Currently, commonly used astigmatic intraocular lenses (IOLs) offer astigmatism correction ranging from 0.75D to 8D. They employ an allosteric surface design, meaning that the highest and lowest angle values ​​on the astigmatic surface of the IOL are located in two orthogonal directions, corresponding to the directions and differences between the flat K (flat curvature) and steep K (steep curvature) on the cornea. For example... Figure 1 As shown, corneal topography in typical astigmatism patients usually exhibits a symmetrical "butterfly" or "bowtie" pattern, indicating a difference in maximum and minimum corneal curvature along a meridian (e.g., vertical or horizontal) (i.e., the astigmatic axis). This type of astigmatism is regular astigmatism; whether with or against the rules, the directions of maximum and minimum curvature are orthogonal. Therefore, astigmatism can be corrected if the implanted intraocular lens ensures that the curvature in these two directions is exactly complementary, the directions of maximum and minimum curvature are exactly opposite to those of the cornea, and the correction power matches the cornea. The formula used for conventional astigmatism correction lenses is as follows:

[0004]

[0005] Where z is the sag of the torus, and C x and C y Let k be the reciprocal of the radius of curvature in the x and y directions, respectively. xand ky are the conic coefficients in the x and y directions, respectively. x and y are the directions of maximum and minimum curvature, respectively, where the major axis direction (maximum curvature) is the astigmatism correction power.

[0006] However, if the corneal astigmatism is irregular, conventional astigmatism correction methods will not achieve the best results. For example... Figure 2 As shown, the distribution of corneal curvature is irregular and asymmetrical. This corneal topography map shows that the curvature varies along a line, and the highest and lowest optical powers cannot be orthogonally perpendicular, thus rendering ordinary astigmatism corrective lenses ineffective. From the above formula, it can be deduced that the astigmatic surface must have its major and minor axes perpendicular to each other. When the corneal asymmetry reaches a certain level, this correction method fails, especially when the Symmetry Regularity Index (SRI) is less than 0.5 or the Surface Asymmetry Index (SAI) is less than 0.3. Taking the steep K direction as the x-axis, when astigmatism on the positive x-axis is corrected, the negative x-axis will cause corresponding reverse astigmatism, failing to achieve optimal visual acuity. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a fully free-adjusting intraocular lens for astigmatism correction. This intraocular lens can freely adjust various types of astigmatism, achieving full optical plane aberration correction, and can provide customized intraocular lenses for astigmatism patients. The specific technical solution is as follows:

[0008] A fully free-form astigmatism corrective intraocular lens comprises an optical portion and a mechanical portion. One surface of the optical portion is a fully free-form surface, and the other surface is a spherical or aspherical surface. The customization steps for the fully free-form surface are as follows:

[0009] (1) Measure and obtain the patient's corneal topography, obtain the distribution of the patient's corneal curvature radius Rc, and determine the patient's corneal astigmatism value Cc (i.e., the difference between the maximum and minimum optical power on the patient's corneal surface); the optical power distribution on the patient's corneal surface is asymmetrical or non-uniform;

[0010] (2) Set the distribution trend of the radius of curvature R of the freeform surface to be exactly opposite to the radius of curvature Rc of the corneal surface (that is, the minimum radius of curvature in the freeform surface is consistent with the distribution area of ​​the maximum radius of curvature of the patient's corneal surface, and the maximum radius of curvature in the freeform surface is consistent with the distribution area of ​​the minimum radius of curvature of the patient's corneal surface); set the astigmatism value C of the freeform surface of the lens to be the opposite of the astigmatism value Cc of the patient's corneal surface, that is, C = -Cc, where the distribution of the maximum radius of curvature and the minimum radius of curvature of the freeform surface is free, and the angle between the two is 0 to 180°;

[0011] (3) Fix the astigmatism value C of the freeform surface to the constant value determined in step (2), use the xy irregular polynomial to determine the surface function of the freeform surface, and calculate the actual ray path by combining equations (1)-(6) with optical software to obtain the surface function Z(x,y) of the freeform surface:

[0012]

[0013] R 2 =k x 2 +k y 2 (2)

[0014]

[0015]

[0016]

[0017]

[0018] Among them, a ij The coefficients are polynomials, obtained by optical design software through least squares optimization based on the R values ​​set for different regions. i and j are the powers of x and y, respectively, and N and M are positive integers. The steep K direction is used as the y-axis, and the direction perpendicular to the steep K direction is used as the x-axis.

[0019] Rmin is the minimum radius of curvature of the fully free surface, and Rmax is the maximum radius of curvature of the fully free surface;

[0020] k x k y Let R be the radius of curvature of a point on a fully free surface, decomposed into the radii of curvature in the x and y directions.

[0021] H is the Gaussian curvature of the freeform surface, and K is the average curvature of the freeform surface;

[0022] Z x , Z y Let Z(x, y) be the first derivative with respect to x and y. xx , Z yy , Z xy Let Z(x, y) be the second derivative of Z(x, y) with respect to x and y.

[0023] Furthermore, the diameter of the freeform surface is ≥6mm, and the optical power distribution along any axis passing through the center of the circle is asymmetrical.

[0024] Furthermore, the astigmatism value C on different axes of the freeform surface ranges from 0 to 10D, and the difference in optical power between adjacent 1° axes is less than 0.22D.

[0025] Furthermore, the optical portion of the intraocular lens features markings for the intraocular lens astigmatism correction angle.

[0026] Furthermore, for regular astigmatism, the astigmatism correction angle markings of the intraocular lens are parallel and symmetrical, and the marking axis is the axis with the minimum surface curvature of the optical part or the highest optical power.

[0027] Furthermore, for cases of irregular astigmatism, the astigmatism correction angle markings of the intraocular lens are displayed separately, and the corresponding axis markings with the minimum surface curvature or the highest optical power should be distinguished from other angle markings.

[0028] Furthermore, the astigmatism correction angle markers for intraocular lenses are rectangular or continuous dots.

[0029] This invention relates to an astigmatism-correcting intraocular lens (IOL) capable of correcting regular or irregular astigmatism along all axes. It is particularly suitable for correcting astigmatism in patients with irregular astigmatism. A customized IOL can be made to fit the individual patient's specific astigmatism needs, completely resolving astigmatism post-surgery and improving post-operative vision. This invention addresses the limitations of traditional astigmatism lenses, specifically the asymmetrical distribution of irregular astigmatism angles, and resolves the residual astigmatism issue in patients with irregular astigmatism, achieving astigmatism correction at fully free angles on the optical surface. Attached Figure Description

[0030] Figure 1 Corneal topography for patients with regular astigmatism (Example 2);

[0031] Figure 2 Corneal topography for patients with irregular astigmatism (Example 1);

[0032] Figure 3 A diagram showing the astigmatism correction angle of an intraocular lens for regular astigmatism;

[0033] Figure 4 A diagram showing the astigmatism correction angle of an intraocular lens for irregular astigmatism;

[0034] Figure 5 This is a surface curvature radius distribution diagram of the free-form surface of the intraocular lens in Example 1;

[0035] Figure 6 This is a surface optical power distribution diagram of the freeform surface of the intraocular lens in Example 1;

[0036] Figure 7 This is a surface marking diagram of the freeform surface of the intraocular lens in Example 1;

[0037] Figure 8Image quality of corneal modeling for a patient with irregular astigmatism in Example 1;

[0038] Figure 9 Image quality of patient 1 after wearing a custom-made intraocular lens;

[0039] Figure 10 Example 2 shows the distribution trend of focal length obtained through software optimization.

[0040] Figure 11 This is a diagram illustrating the astigmatic axis markings for Example 2.

[0041] Figure 12 Image quality of corneal modeling for a patient with regular astigmatism in Example 2;

[0042] Figure 13 This is an image quality image of the patient in Example 2 after wearing a custom-made intraocular lens. Detailed Implementation

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] Example 1

[0045] This example focuses on a patient with keratoconus astigmatism, a relatively typical type of irregular astigmatism, whose corneal topography is as follows: Figure 2 As shown, its astigmatism is a completely asymmetrical distribution. With the steep K direction as the y-axis and the direction perpendicular to the steep K direction as the x-axis, its cornea in the fourth quadrant has a steep K value of 49.77D, and the average K value of the rest is 44.20D. Its astigmatism value is 5.5D, and it is asymmetrically distributed, with abrupt bulges only on the y-axis.

[0046] Astigmatism in this region is corrected by creating a freeform surface using xy polynomials, such that the degree in the corresponding y-axis direction is exactly 5.5D smaller than that in other regions. In the optical design software, by setting functions (1)-(6), the difference between the optical power value at this angle and the average optical power of the rest is set to -5.5D. The remaining average optical power is the part other than the crystal surface region corresponding to the steep K region. The coefficients of the polynomials are optimized by the least squares method, and the final surface curvature radius distribution of the freeform surface of the artificial lens is as follows: Figure 5 As shown, its surface optical power distribution is as follows: Figure 6 As shown, it can be seen that the focal power is low in the negative half-axis region of the y-axis, while the focal power is evenly distributed in the remaining areas, which is exactly the opposite of the corneal focal power distribution of patients with irregular astigmatism.

[0047] The region corresponding to the highest power of this intraocular lens is the region corresponding to the lowest power of the cornea. There should be an axial marker in the direction of the highest power, such as... Figure 4 As shown, two types of intraocular lens (IOL) astigmatism correction angle markings are used: a rectangular shape and continuous dots. These represent the axes of minimum and maximum surface curvature, respectively, and also indicate the two directions of maximum and minimum optical power of the IOL surface. Horizontal stripes mark the direction of maximum power, and three dots mark the direction of minimum power. The surface markings of this IOL's freeform surface should be as follows... Figure 7 As shown.

[0048] A corneal model of a patient with irregular astigmatism was created and used to replace the normal cornea of ​​the model eye in ISO 11979-2:2024, 5th edition, Ophthalmic Implants—Intraocular Lenses. The image quality was as follows: Figure 8 As shown, the MTF (modulator-demodulator transfer function) value in the sagittal direction is very low, and the patient is affected by astigmatism, unable to obtain good corrected visual acuity regardless of the prescription of the glasses. However, after replacing the natural lens with the aforementioned fully free-astigmatism correcting intraocular lens, the image quality is as follows... Figure 9 As shown, the MTF in both directions can achieve a theoretical value of no less than 80% of the diffraction limit, proving that after astigmatism correction through simulated implantation of this crystal, the patient can obtain the expected better vision.

[0049] Example 2

[0050] This embodiment is for a patient with regular corneal astigmatism, whose corneal topography is as follows: Figure 1 As shown, this is a regular, regular astigmatism. It has a relatively large refractive power in the vertical direction, which is the steep K-direction, with a refractive power of 44.99D. The direction perpendicular to the steep K-direction is the horizontal K-direction, which has a relatively small refractive power of 43.46D. This is regular astigmatism, and it can be corrected by applying a 1.5D astigmatism correction in both the meridional and sagittal directions (corresponding to the y-axis and x-axis) of the intraocular lens's optical surface.

[0051] Astigmatism in this region is corrected by creating a freeform surface using xy polynomials, ensuring that the refractive power along the y-axis is exactly 1.5D smaller than that along the x-axis, opposite to the surface refractive power of the cornea. After designing the optimization parameters in optical design software, the distribution trend of the power can be obtained through automatic optimization, such as... Figure 10 As shown. The astigmatism correction angle markings of regular astigmatic intraocular lenses are parallel and symmetrical, with the marking axis being the axis of highest optical power on the optical surface, such as... Figure 11 As shown.

[0052] A corneal model of a patient with regular astigmatism was created, replacing the normal cornea of ​​the model eye in ISO 11979-2:2024, 5th edition—Ophthalmic implants—Intraocular lenses. The image quality was as follows: Figure 12 As shown, the MTF value in the sagittal direction is very low, and the patient is affected by astigmatism, unable to achieve good corrected visual acuity regardless of the prescription of the glasses. However, after replacing the natural lens with a superior astigmatism-correcting intraocular lens, the image quality is as follows... Figure 13 As shown, good MTF values ​​can be obtained in both directions, proving that patients can achieve the expected good vision after astigmatism correction through simulated implantation of this lens.

[0053] The preferred embodiments of this patent have been described in detail above. However, this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this patent.

Claims

1. A fully free-flowing astigmatism-correcting intraocular lens, characterized in that: It comprises optical and mechanical parts. One surface of the optical part is a freeform surface, and the other surface is a spherical or aspherical surface. The customization steps for the freeform surface are as follows: (1) Measure and obtain the patient's corneal topography, obtain the distribution of the patient's corneal radius of curvature Rc, and determine the patient's corneal astigmatism value Cc; the optical power distribution on the patient's corneal surface is asymmetrical or non-uniform; (2) Set the distribution trend of the curvature radius R of the freeform surface to be exactly opposite to the curvature radius Rc of the patient's corneal surface. Set the astigmatism value C of the freeform surface of the lens to be the opposite of the astigmatism value Cc of the patient's corneal surface, i.e., C = -Cc. The distribution of the maximum and minimum curvature radii of the freeform surface is free, and the angle between them is 0 to 180°. (3) Fix the astigmatism value C of the freeform surface to the constant value determined in step (2), use the xy irregular polynomial to determine the surface function of the freeform surface, and calculate the actual ray path by combining equations (1)-(6) with optical software to obtain the surface function Z(x,y) of the freeform surface: Among them, a ij The coefficients are polynomials, obtained by optical design software through least squares optimization based on the R values ​​set for different regions. i and j are the powers of x and y, respectively, and N and M are positive integers. The steep K direction is used as the y-axis, and the direction perpendicular to the steep K direction is used as the x-axis. Rmin is the minimum radius of curvature of the fully free surface, and Rmax is the maximum radius of curvature of the fully free surface; k x k y Let R be the radius of curvature of a point on a fully free surface, decomposed into the radii of curvature in the x and y directions. H is the Gaussian curvature of the freeform surface, and K is the average curvature of the freeform surface; Z x Z y Let Z(x, y) be the first derivative with respect to x and y. xx Z yy Z xy Let Z(x, y) be the second derivative of Z(x, y) with respect to x and y.

2. The astigmatism-correcting intraocular lens according to claim 1, characterized in that: The diameter of the freeform surface is ≥6mm, and the optical power distribution along any axis passing through the center of the circle is asymmetrical.

3. The astigmatism-correcting intraocular lens according to claim 1, characterized in that: The astigmatism value C on the freeform surface ranges from 0 to 10D along different axes, and the difference in optical power between adjacent 1° axes is less than 0.22D.

4. The astigmatism-correcting intraocular lens according to claim 1, characterized in that: The optical component of the intraocular lens has markings indicating the astigmatism correction angle.

5. The astigmatism-correcting intraocular lens according to claim 4, characterized in that: For regular astigmatism, the astigmatism correction angle markings of the intraocular lens are parallel and symmetrical, and the marking axis is the axis with the minimum surface curvature of the optical part or the highest optical power.

6. The astigmatism-correcting intraocular lens according to claim 4, characterized in that: For cases of irregular astigmatism, the astigmatism correction angle markings of the intraocular lens are displayed separately, and the corresponding axis markings with the minimum surface curvature or the highest optical power should be distinguished from other angle markings.

7. The astigmatism-correcting intraocular lens according to claim 6, characterized in that: The astigmatism correction angle markings for intraocular lenses are either rectangular or continuous dots.

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