Full-free astigmatism correction artificial lens

Abstract

The invention relates to an artificial lens in medical instruments, in particular to a full-free astigmatism correction artificial lens. The artificial lens comprises an optical part and a mechanical part, one surface of the optical part is a full-free-form surface, and the other surface of the optical part is a spherical surface or an aspheric surface; the full-free curved surface is customized by using an xy irregular polynomial according to the astigmatism degree value of the cornea of a patient. According to the artificial lens, various types of astigmatism can be freely adjusted, all-optical surface aberration adjustment is achieved, and a customized artificial lens can be provided for an astigmatism patient. Aiming at the limitation of a traditional astigmatism crystal and the problem of asymmetric distribution of irregular astigmatism angles, the problem of residual astigmatism of a patient with irregular astigmatism is solved, and the aim of carrying out astigmatism correction at full-free angles on an optical surface is fulfilled.

Description

Technical Field

[0001] This application relates to intraocular lenses in medical devices, and specifically to a total free astigmatism correction intraocular lens. Background Art

[0002] Astigmatism is a common refractive error. Due to the irregular curvature of the eye's cornea or lens, light entering the eye cannot form a single focal point on the retina but forms multiple focal points or focal lines. This causes blurred vision, double vision, or distortion, especially when looking at fine lines or objects with low contrast. Astigmatism may exist alone or be accompanied by myopia or hyperopia. The causes of astigmatism are mainly divided into two categories: congenital factors and acquired factors. Congenital factors may be slight irregularities in the shape of the cornea or lens at birth, which may change with age. Acquired astigmatism may be due to eye trauma, corneal diseases, long-term bad eye use habits, or eyelid compression. Astigmatism correction after cataract surgery is mainly used to correct the irregular curvature of the cornea. If a patient with corneal astigmatism has their natural lens emulsified and aspirated without implanting an astigmatism correction intraocular lens, it will cause great visual distress to the patient after surgery: both distant and near vision are blurred or distorted; eye fatigue, headache (especially after long-term eye use); decreased night vision (such as glare or trailing of lights when driving).

[0003] Currently, the astigmatism degrees of commonly used astigmatism intraocular lenses range from 0.75D to 8D, and a toric design is adopted, that is, there are the highest and lowest angular values on two orthogonal directions on the astigmatic surface of the intraocular lens, corresponding to the directions and differences of the flat K (flat curvature) and steep K (steep curvature) on the cornea. As Figure 1 shown, the corneal topographies of ordinary astigmatism patients usually present a symmetric "butterfly shape" or "bowtie pattern" (Bowtie Pattern), indicating that there are maximum and minimum differences (i.e., the astigmatism axis) in the curvature of the cornea in a certain meridian direction (such as vertical or horizontal). This type of astigmatism belongs to regular astigmatism. Whether it is with-the-rule astigmatism or against-the-rule astigmatism, the directions of the maximum curvature and the minimum curvature are orthogonal to each other. Therefore, as long as the implanted intraocular lens ensures that the curvatures in these two directions are exactly complementary, the directions of the maximum and minimum curvatures are exactly opposite to those of the cornea, and the correction degrees match, astigmatism can be corrected. The calculation formula used for conventional astigmatism correction lenses is as follows:

[0004]

[0005] Among them, z is the sagittal height of the toric surface, and are respectively the reciprocals of the curvature radii in the x direction and the y direction, and They are the conic coefficients in the x - direction and y - direction respectively. x and y are the directions of the maximum curvature and the minimum curvature respectively, where the major axis direction (maximum curvature) is the astigmatic correction power.

[0006] However, if the corneal astigmatism is irregular astigmatism, the conventional astigmatism correction cannot achieve the best astigmatic correction effect. For example, Figure 2 As shown, the distribution of corneal curvature is irregular and asymmetric. The corneal topography shows that the curvature on a line is variable, and the highest and lowest powers are not orthogonal. Then the ordinary astigmatic correction lens loses its correction function. It can be concluded from the above formula that the astigmatic surface must have its major axis and minor axis perpendicular to each other. When the corneal asymmetry reaches a certain degree, 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. We take the steep K direction as the x - direction. When the astigmatism on the positive x - axis is corrected, the astigmatism on the negative x - axis will cause a corresponding reverse astigmatism, and the best visual effect cannot be achieved. Summary of the Invention

[0007] To solve the above problems, the present invention provides a fully free astigmatic correction intraocular lens, which can freely adjust various types of astigmatism, realize the adjustment of the entire optical surface aberration, and can provide customized intraocular lenses for astigmatic patients. The specific technical solutions are as follows:

[0008] A fully free astigmatic correction intraocular lens, which comprises an optical part and a mechanical part. One surface of its optical part is a fully free surface, and the other surface is a spherical or aspherical surface; the customization steps of the fully free surface are as follows:

[0009] (1) Measure and obtain the corneal topography of the patient, obtain the distribution of the corneal curvature radius Rc of the patient, and determine the corneal astigmatism value Cc of the patient (that is, the difference between the maximum and minimum powers on the corneal surface of the patient); the power distribution on the corneal surface of the patient is asymmetric or non - uniform;

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

[0011] (3) Fix the astigmatism value C of the full freeform surface as a fixed value determined in step (2). Use an xy irregular polynomial to determine the surface function of the full freeform surface. Calculate the actual light path through equations (1)-(6) combined with optical software to obtain the surface function of the full freeform surface :

[0012] (1)

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

[0014] (3)

[0015] (4) (5)

[0016] (6)

[0017] Among them, are polynomial coefficients, optimized by the optical design software through the least squares method according to the R values set in different regions. i and j are the powers of x and y respectively, and N and M are positive integers;

[0018] Rmin is the minimum radius of curvature of the full freeform surface, and Rmax is the maximum radius of curvature of the full freeform surface;

[0019] k x 、k y are the radii of curvature of a certain point on the full freeform surface decomposed in the x and y directions of the radius of curvature R;

[0020] H is the Gaussian curvature of the full freeform surface, and K is the mean curvature of the full freeform surface;

[0021] are the first-order derivatives of Z(x, y) with respect to x and y, are the second-order derivatives of Z(x, y) with respect to x and y.

[0022] Furthermore, the diameter of the full freeform surface ≥ 6 mm, and the optical power distribution in any axial direction passing through the center of the circle is asymmetric.

[0023] Furthermore, the astigmatism value C in different axial directions on the full freeform surface ranges from 0 to 10 D, and the difference in optical power between every adjacent 1° axial position is less than 0.22 D.

[0024] Furthermore, the optical part of the intraocular lens has markings for the astigmatism correction angle of the intraocular lens.

[0025] Furthermore, for regular astigmatism, the markings for the astigmatism correction angle of the intraocular lens are parallel and symmetric, and the marked axis is the axis with the minimum surface curvature or the highest optical power of the optical part surface.

[0026] Furthermore, for irregular astigmatism, the markings for the astigmatism correction angle of the intraocular lens are shown separately, and the marked axis with the minimum surface curvature or the highest optical power corresponding to it should be distinguished from other angle markings.

[0027] Furthermore, the markings for the astigmatism correction angle of the intraocular lens are in the shape of a rectangle or continuous dots.

[0028] The present invention is an astigmatism correction intraocular lens that can correct regular or irregular astigmatism in all directions. It is particularly suitable for astigmatism correction of patients with irregular astigmatism. A customized intraocular lens suitable for their astigmatism correction can be customized for patients with irregular astigmatism, which can completely solve the astigmatism problem of astigmatism patients after surgery and improve postoperative vision. Aiming at the limitations of traditional astigmatism lenses and the asymmetric distribution problem of irregular astigmatism angles, the present invention solves the residual astigmatism problem of patients with irregular astigmatism and realizes the purpose of astigmatism correction at all free angles on the optical surface. Brief Description of the Drawings

[0029] Figure 1 Is the corneal topography of a patient with regular astigmatism (Example 2);

[0030] Figure 2 Is the corneal topography of a patient with irregular astigmatism (Example 1);

[0031] Figure 3 Is the marking diagram of the astigmatism correction angle of the regular astigmatism intraocular lens;

[0032] Figure 4 Is the marking diagram of the astigmatism correction angle of the irregular astigmatism intraocular lens;

[0033] Figure 5 Is the distribution diagram of the surface curvature radius of the full free surface of the intraocular lens in Example 1;

[0034] Figure 6 Is the distribution diagram of the surface optical power of the full free surface of the intraocular lens in Example 1;

[0035] Figure 7 Is the surface marking diagram of the full free surface of the intraocular lens in Example 1;

[0036] Figure 8 Is the corneal modeling image quality diagram of a patient with irregular astigmatism in Example 1;

[0037] Figure 9 The image quality diagram of the patient in Example 1 wearing a customized intraocular lens;

[0038] Figure 10 For Example 2, the distribution trend diagram of the diopter can be obtained by software self-optimization;

[0039] Figure 11 The astigmatism axis position identification diagram for Example 2;

[0040] Figure 12 The corneal modeling image quality diagram of the regular astigmatism patient in Example 2;

[0041] Figure 13 The image quality diagram of the patient in Example 2 wearing a customized intraocular lens. Detailed implementation manners

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] Example 1

[0044] This embodiment is for keratoconus astigmatism patients, which is a relatively typical type of irregular astigmatism. Its corneal topographic map is as Figure 2 shown. Its astigmatism state is a completely asymmetric astigmatism distribution. Taking the steep K direction as the y-axis and the direction perpendicular to the steep K direction as the x-axis, the cornea in the fourth quadrant has a steep K value of 49.77D, and the remaining average K value is 44.20D. Its astigmatism value is 5.5D and is asymmetrically distributed, with only a sudden bulge on the y-axis.

[0045] The xy polynomial is used to create a free-form surface to correct the astigmatism in this area, so that the degree in the corresponding y-axis direction is exactly 5.5D smaller than that in other areas. In the optical design software, the function settings in formulas (1)-(6) are used to set the difference between the optical power value at this angle and the average optical power of the rest to be -5.5D. The remaining average power is the part except for the crystal surface area corresponding to the steep K area. The coefficients of the polynomial are optimized by the least squares method. Finally, the surface curvature radius distribution of the entire free-form surface of the intraocular lens is as Figure 5 shown, and its surface optical power distribution is as Figure 6 shown. It can be seen that the optical power in the negative half-axis region of the y-axis is low, and the remaining optical powers are evenly distributed, exactly opposite to the corneal optical power distribution of irregular astigmatism patients.

[0046] The area corresponding to the highest dioptric power of the intraocular lens is the area corresponding to the lowest dioptric power of the cornea. There should be an axis mark in the direction of the highest dioptric power, such as Figure 4 shown. The astigmatism correction angle marks of the two intraocular lenses are rectangular and continuous dot-shaped respectively. They represent the axes with the smallest surface curvature and the largest surface curvature respectively, and are also the identifiers of the two directions with the largest and smallest surface dioptric power of the intraocular lens. The highest dioptric power direction is marked with a horizontal stripe, and the lowest dioptric power direction is marked with a three-point style. The surface marks of the all-free-form surface of the intraocular lens should be as Figure 7 shown.

[0047] Model the cornea of patients with irregular astigmatism and replace the normal cornea of the model eye in "ISO 11979-2:2024, 5th Edition, Ophthalmic Implants - Intraocular Lenses". Its image quality is as Figure 8 shown. The MTF (modulation transfer function) value in the sagittal direction is very low. Affected by astigmatism, the patient cannot obtain good corrected vision no matter how many degrees of glasses are worn. After replacing the natural lens with the above all-free-form astigmatism correction intraocular lens, its image quality performance is as Figure 9 shown. The MTF in both directions can obtain a theoretical value not lower than 80% of the diffraction limit, which proves that after astigmatism correction through the simulated implantation of this lens, the patient can obtain the expected better vision.

[0048] Example 2

[0049] This example is for patients with regular corneal astigmatism. The corneal topographic map of this patient is as Figure 1 shown. It is a regular with-the-rule astigmatism, which has a relatively large refractive power in the vertical direction. This is the steep K direction, and the diopter in the steep K direction is 44.99D. The direction perpendicular to the steep K direction is the flat K direction, which has a relatively small refractive power, 43.46D. This is regular astigmatism. Only by applying a 1.5D astigmatism degree in the two perpendicular meridional and sagittal directions (corresponding to the y-axis and x-axis directions) on the optical surface of the intraocular lens can the regular astigmatism on the corneal surface of the patient be corrected.

[0050] Use the xy polynomial to create a free-form surface to correct the astigmatism in this area, so that the refractive power in the y-axis direction is exactly 1.5D smaller than that in the x-axis direction, which is opposite to the corneal surface refractive power. After setting the optimization index in the optical design software, self-optimization can obtain the distribution trend of the dioptric power, such as Figure 10 shown. The astigmatism correction angle marks of the regular astigmatism intraocular lens are parallel and symmetric, and the marked axis is the axis with the highest surface dioptric power of the optical part, such as Figure 11 shown.

[0051] Model the cornea of patients with regular astigmatism and replace the normal cornea of the model eye in "ISO 11979-2:2024, 5th edition, Ophthalmic implants - Intraocular lenses". Its image quality is as Figure 12 shown. The MTF value in the sagittal direction is very low. Affected by astigmatism, patients cannot obtain good corrected vision no matter how many degrees of glasses they wear. After replacing the natural lens with the above astigmatism correction intraocular lens, its image quality performance is as Figure 13 shown. Good MTF values can be obtained in both directions, proving that after astigmatism correction through the simulated implantation of this lens, patients can obtain better vision as expected.

[0052] The above has described the preferred embodiments of this patent in detail. However, this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can also be made without departing from the purpose of this patent.

Claims

1. A fully free astigmatism correcting intraocular lens, characterized in that: It includes an optical part and a mechanical part. One surface of its optical part is a fully free-form surface, and the other surface is a spherical surface or an aspherical surface. The customization steps of the fully free-form surface are as follows: (1) Measure the patient's corneal topographic map, obtain the distribution of the corneal curvature radius Rc of the patient, and determine the corneal astigmatism value Cc of the patient. The dioptric power distribution on the patient's corneal surface is asymmetric or non-uniform. (2) Set the distribution trend of the curvature radius R of the fully free-form surface to be exactly opposite to that of the corneal surface curvature radius Rc of the patient. Set the astigmatism value C of the fully free-form surface of the intraocular lens to be the opposite of the corneal astigmatism value Cc of the patient, that is, C = -Cc, where the distribution of the maximum curvature radius and the minimum curvature radius of the fully free-form surface is free, and the included angle between the two is 0° to 180°. (3) The fixed astigmatism value C of the full free-form surface is a fixed value determined in step (2). The surface function of the full free-form surface is determined by an xy irregular polynomial. The actual light path is calculated by combining equations (1)-(6) with optical software to obtain the surface function of the full free-form surface. : （1） R 2 = k x 2 + k y 2 (2) （3） （4） （5） （6） Among them, are polynomial coefficients, which are obtained by optimizing through the least bisquare method according to the R values set in different regions by optical design software. i and j are the powers of x and y respectively, and N and M are positive integers; Rmin is the minimum curvature radius of the fully free-form surface, and Rmax is the maximum curvature radius of the fully free-form surface. k x 、k y are the radii of curvature in the x- and y-directions obtained by decomposing the radius of curvature R of a point on a fully free-form surface. H is the Gaussian curvature of the fully free-form surface, and K is the mean curvature of the fully free-form surface. is the first-order derivative of Z(x, y) with respect to x and y, is the second-order derivative of Z(x, y) with respect to x and y.

2. The fully free astigmatism correcting intraocular lens according to claim 1, wherein: The diameter of the fully free-form surface is ≥6 mm, and the dioptric power distribution in any axial direction passing through the center of the circle is asymmetric.

3. The total freedom astigmatism correcting intraocular lens according to claim 1, characterized in that: The range of the astigmatism value C in different axial directions on the fully free-form surface is 0 to 10 D, and the dioptric power difference between every adjacent 1° axial position is less than 0.22 D.

4. The free-form astigmatism correcting intraocular lens according to claim 1, wherein: The optical part of the intraocular lens is marked with the intraocular lens astigmatism correction angle.

5. The fully free astigmatism correcting intraocular lens according to claim 4, characterized in that: For regular astigmatism, the intraocular lens astigmatism correction angle marks are parallel and symmetric, and the marked axial position is the axial position with the minimum surface curvature or the highest dioptric power of the optical part surface.

6. The full-free astigmatism correcting intraocular lens according to claim 4, wherein: For irregular astigmatism, the intraocular lens astigmatism correction angle marks are shown separately, and the marked axial position with the minimum corresponding surface curvature or the highest dioptric power should be distinguished from other angle markings.

7. The total freedom astigmatism correction intraocular lens according to claim 6, characterized in that: The intraocular lens astigmatism correction angle marks are in the shape of a rectangle or continuous dots.

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