Design and manufacturing methods for eyeglass lenses for correcting oblique astigmatism

Abstract

To provide a method for designing lenses for eyeglasses for correcting oblique astigmatism that can solve an existing issue that arises when the sense of slanting generated in correction of oblique astigmatism is reduced, and a method for manufacturing the lenses for eyeglasses.SOLUTION: The present invention relates to a method for designing lenses for eyeglasses for correcting oblique astigmatism that can reduce the sense of slanting generated when the lenses are worn, the directions of astigmatic axes of both lenses crossing each other. The shape of the curve of at least one surface of each lens is designed to be aspheric. This allows adding out-prism into the axial direction of a toric surface and the difference in the meridian magnification can be reduced. The sense of slanting can be thus reduced.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for designing and manufacturing a spectacle lens for correcting oblique astigmatism. [Background technology]

[0002] To correct astigmatism, eyeglass lenses for correcting astigmatism are generally worn. Lenses for correcting astigmatism use a cylindrical lens surface (toric surface) to cancel out the non-spherical curves of the cornea and lens of people with astigmatism. A toric surface has a surface with a different curvature, and by using this, it serves to correct light passing through a spherical surface. The axis of the toric surface is positioned according to the axis direction of the wearer's astigmatism. Non-patent document 1 describes such cylindrical lenses for correcting astigmatism. Correcting astigmatism can sometimes make the glasses uncomfortable to wear. For example, there is the slant sensation that occurs when correcting oblique astigmatism. Slant sensation occurs when viewing with both eyes through a cylindrical lens, and the view appears tilted due to the different depth perceptions that occur above and below the lens. An overview of slant sensation is provided below with reference to Figure 4. When correcting oblique astigmatism, the left and right eyeglass lenses for correcting oblique astigmatism are positioned so that the axial direction of the toric surface intersects at an angle, as shown in Figure 4. When eyeglass lenses have a toric surface, prism is generated based on the shape of the toric surface from the axial direction of the toric surface in a direction perpendicular to the axis. However, because the axial direction of the toric surface is oblique, the prism is not uniform around the circumference of the lens. As a result, when you look up and down, the three-dimensional image formed by your left and right eyes appears to move forward and backward. This is the cause of the slant sensation. For example, in Figure 4, near the in-prism area, i.e., near the upper and inner side of the lens, the image in binocular vision (stereoscopic vision) is formed at a position closer to the object screen, which is the base point of the actual convergence angle α, and at the base point of the convergence angle β (this type of appearance is called crossed parallax). On the other hand, near the out-prism area, i.e., near the lower and inner side of the lens, the image in stereoscopic vision is formed at a position farther back from the object screen, which is the base point of the actual convergence angle α, and at the base point of the convergence angle β (this type of appearance is called ipsilateral parallax). In other words, in binocular vision (stereoscopic vision), crossed parallax and ipsilateral parallax cause vertical lines to appear tilted from the front to the back. This slant perception becomes more pronounced the greater the difference in meridian magnification (prism difference). Furthermore, it becomes more pronounced the closer the astigmatic axes of the left and right lenses are to a right angle, and it becomes more pronounced the stronger the astigmatism. [Prior art documents] [Patent documents]

[0003] [Non-Patent Document 1] Glasses Portal, a comprehensive information site for glasses [online], the Japan Medical Optical Equipment Industry Association website, [searched on January 20, 2021], Internet<URL:http: / / www.jmoia.jp / glasses / meganeportal / lens / eyesandlens5.html> [Non-patent document 2] Satoshi Hasebe, "Astigmatism correction and slant sensation with eyeglass lenses - To provide better eyeglass vision -", New Eye Care Vol. 24 No. 9 September 2007, Medical Aoi Publishing, September 30, 2007, pp. 1145-1150 Summary of the Invention [Problem to be solved by the invention]

[0004] Non-Patent Document 2 discloses methods for reducing (improving) the slant sensation that occurs during oblique astigmatism correction. It proposes reducing the power (astigmatic power) of the cylindrical lens as Countermeasure 1, reducing the three-dimensional sensation by shortening the vertex distance as Countermeasure 2, and shifting the axial direction of the cylindrical lens by 90 or 180 degrees as Countermeasure 3. However, Countermeasure 1 reduces the power of the cylindrical lens, which reduces the amount of correction and increases residual astigmatism. Countermeasure 2 is that, since the lenses are glasses, the vertex distance cannot be shortened excessively. Countermeasure 3 also increases residual astigmatism. Therefore, there was a need for a better design that would reduce the slant sensation that occurs when wearing glasses to correct oblique astigmatism. The present invention was made in response to these problems existing in the prior art, and its purpose is to provide a method for designing and manufacturing a spectacle lens for correcting oblique astigmatism, which can solve the conventional problem of reducing the slant sensation that occurs during oblique astigmatism correction. [Means for solving the problem]

[0005] As a first means for solving the above problem, a method for designing eyeglass lenses for correcting oblique astigmatism, in which the astigmatism axis directions of the left and right lenses intersect, is provided for reducing the slant sensation that occurs when wearing eyeglass lenses for correcting oblique astigmatism, in which the curve shape of at least one of the front and back surfaces of the left and right lenses is designed to be aspherical. With this configuration, it is possible to reduce the sense of slant compared to when a spherical lens is used. By using an aspherical design, it is possible to add out-prism in the axial direction of the toric surface, which reduces the difference in meridian magnification, and as a result, it is possible to reduce the sense of slant. "Oblique astigmatism" refers to astigmatism in which an object is displaced obliquely when viewed. In the present invention, this refers to astigmatism in which the object is displaced in any direction other than 180 degrees or 90 degrees. This can be either single astigmatism or compound astigmatism. Furthermore, "crossing astigmatism axes" refers to a state in which the left and right astigmatism axes are arranged at an angle of up to 90 degrees, excluding cases in which the astigmatism axes are arranged parallel to one another. The binocular retinal disparity due to differences in astigmatic axis and meridian magnification affects the magnitude of the slant sensation. If the astigmatic axis direction is at 45 degrees and 135 degrees to the horizontal, and other conditions are the same, the slant sensation is greatest, and if the crossing angle of the astigmatic axis direction is 90 degrees, and other conditions are the same, the slant sensation is greatest.

[0006] As a second means, the right and left lenses are provided with an area set to a corrective power that reduces the astigmatic power in the original prescription power. As mentioned above, reducing the astigmatism power is described in Measure 1 in paragraph 0004, but if the astigmatism power is reduced after making the lens aspherical, the sense of slant can be reduced even if the reduction in astigmatism power is relatively smaller than when the lens is spherical, and the lens can still be given sufficient power to correct oblique astigmatism. As a third measure, the area set to the corrective power is the central area of the lens. This is because the central region of the lens is the area of the eyeglass lens through which the line of sight passes most frequently, and therefore it is necessary to reduce the sense of slant. On the other hand, the area outside the central region of the lens is not the area where the gaze is focused, so there is no significant burden on the wearer even if the sense of slant is not reduced, and in some cases a design that focuses on correcting oblique astigmatism is preferable. For example, for healthy people, an aspheric lens with a corrective power in the central region and the original prescription in the peripheral region will provide vision close to that of a fully corrected state, mainly during peripheral vision, and will also reduce the sense of slant, making it a design that is suitable for healthy people. As a fourth means, the area set to the correcting power is an area other than the central area of the lens. Because the central region of the lens needs to be focused on correcting oblique astigmatism as a spectacle lens, it may be better to leave the astigmatism power at the prescribed value without reducing it, and reduce the astigmatism power in regions other than the central region of the lens to reduce the slant feeling throughout the entire visual field. For example, for patients with eye diseases, an aspheric surface with the original prescription in the central region and the corrected power in the peripheral region would provide fully corrected vision during central vision and reduce the slant feeling in the peripheral region, making it a design suitable for patients with eye diseases. As a fifth means, the area set to the correcting power is an area surrounding the periphery of the central area of the lens. By designing the lens so that a region with a corrective power is provided surrounding the central region, it is possible to ensure the correction of oblique astigmatism in the central region of the lens while at the same time reducing the sense of slant in all directions of the field of view. This is also a suitable design for patients with this condition.

[0007] As a sixth measure, the astigmatism power of the original prescription power is reduced by up to 50%. This is because reducing the astigmatism power by 50% can improve wearing comfort by offsetting the slant sensation even at the expense of astigmatism correction. If the astigmatism correction exceeds 50%, the astigmatism correction effect is insufficient, resulting in a worsening wearing comfort due to residual astigmatism. However, since it is preferable for the astigmatism power to be closer to the prescription, depending on the wearer's preference, a design that deliberately reduces the astigmatism power to less than 50% may be acceptable, even if a slant sensation is observed. This is because the aspheric design suppresses the slant sensation. To suppress the slant sensation while still providing astigmatism correction, it is better to reduce the astigmatism power to 30% to 50% of the original prescription power. As a seventh measure, the angle at which the astigmatic axes of the left and right lenses intersect is designed to be shifted in a direction that makes the angle shallower. This is because the slant sensation becomes more pronounced the greater the angle at which the astigmatic axes of the left and right lenses intersect, and a prescription with a small intersection angle can reduce the rate of reduction in astigmatism power. For example, in the case of "the central area is the corrected power and the peripheral area is the original prescription," by reducing the rate of reduction in astigmatism power in the corrected power, the difference with the astigmatism power of the original prescription becomes smaller, making it possible to relatively reduce the power and aberration gradient (which affects vision) in the peripheral area. As an eighth means, the amount of displacement of the angle is set to be within the range of 15 to 45 degrees. If the angle is less than 15 degrees, it will not be very effective, and if it is more than 45 degrees, the astigmatism correction effect may actually increase. Therefore, it is best to keep the displacement between 15 and 30 degrees. As a ninth means, astigmatism correction power is added to the rear surfaces of the left and right lenses, and at least the rear surfaces of the lenses are designed aspherical. This is because it is easy to process and it is easy to design improved formulations. As a tenth means, a spectacle lens is manufactured by processing the lens surface based on design data acquired by any one of the first to ninth methods for designing a spectacle lens for correcting oblique astigmatism. In the present invention, for example, a designer at an eyeglass manufacturer carries out a design, and the eyeglass manufacturer processes lenses based on the design to manufacture eyeglass lenses.

[0008] The present invention is not limited to the configurations described in the following embodiments. The components of each embodiment and variation may be arbitrarily selected and combined. Furthermore, any component of each embodiment or variation may be arbitrarily combined with any component described in the Summary of the Invention or any component embodying any component described in the Summary of the Invention. The present invention also intends to obtain rights to these by amending this application or filing a divisional application, etc. Furthermore, the applicant intends to obtain rights to the overall design or partial design by filing a conversion application to a design application. The drawings depict the entire device in solid lines, but they also include partial designs claimed for parts of the device. For example, a partial design may be a partial design for a part of the device, or a partial design may be included for a part of the device regardless of the part. A partial design may be a part of the device, or a part of that part. [Effects of the Invention]

[0009] In the present invention, by using an aspherical design for eyeglass lenses for correcting oblique astigmatism, it is possible to add out-prism in the axial direction of the toric surface, thereby reducing the difference in meridian magnification, and as a result, reducing the sense of slant. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is an explanatory diagram for explaining a method for designing the sag of a toric surface of a spectacle lens for correcting oblique astigmatism according to an embodiment. [Figure 2] FIG. 10 is an explanatory diagram for explaining a method for designing the sag of the toric surface of the same spectacle lens for correcting oblique astigmatism. [Figure 3] FIG. 1 is a schematic diagram illustrating a general formula for calculating binocular disparity. [Figure 4] Schematic diagram for explaining the principle of slant perception. [Figure 5] 1A is an average frequency distribution diagram for Example 1-1, and FIG. 1B is an average frequency distribution diagram for Example 1-2. [Figure 6] 1A is an astigmatism distribution diagram for Example 1-1, and FIG. 1B is an astigmatism distribution diagram for Example 1-2. [Figure 7] 1 is a graph showing a graphic representation of the change in slant sensation felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 1, simulated with the horizontal axis representing the horizontal visual field and the vertical axis representing the vertical visual field. [Figure 8]4 is a graph illustrating the magnitude of the slant sensation corresponding to the angle of view in the vertical field of view felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 1. [Figure 9] 4 is a graph illustrating the magnitude of the slant sensation corresponding to the angle of the oblique visual field felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 1. [Figure 10] FIG. 10 is an explanatory diagram illustrating a graph showing an oblique field of view. [Figure 11] Average frequency distribution diagram of Example 2. [Figure 12] FIG. 10 is an astigmatism distribution diagram of Example 2. [Figure 13] 10 is a graph graphically showing the change in slant sensation felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 2, simulated with the horizontal axis representing the horizontal visual field and the vertical axis representing the vertical visual field. [Figure 14] 10 is a graph illustrating the magnitude of the slant sensation felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 2, corresponding to the angle of view in the vertical field of view. [Figure 15] 10 is a graph illustrating the magnitude of the slant sensation corresponding to the angle of the oblique visual field felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 2. [Figure 16] Average frequency distribution diagram of Example 3. [Figure 17] FIG. 10 is an astigmatism distribution diagram of Example 3. [Figure 18] 10 is a graph graphically showing the change in slant sensation felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 3, simulated with the horizontal axis representing the horizontal visual field and the vertical axis representing the vertical visual field. [Figure 19] 10 is a graph illustrating the magnitude of the slant sensation felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 3, corresponding to the angle of view in the vertical field of view. [Figure 20] 10 is a graph illustrating the magnitude of the slant sensation corresponding to the angle of the oblique visual field felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 3. [Figure 21] Average frequency distribution diagram of Example 4. [Figure 22]FIG. 10 is an astigmatism distribution diagram of Example 4. [Figure 23] 10 is a graph graphically showing the change in slant sensation felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 4, simulated with the horizontal axis representing the horizontal visual field and the vertical axis representing the vertical visual field. [Figure 24] (a) is an average frequency distribution diagram for Example 5-1, and (b) is an average frequency distribution diagram for Example 5-2. [Figure 25] 10A is an astigmatism distribution diagram for Example 5-1, and FIG. 10B is an astigmatism distribution diagram for Example 5-2. [Figure 26] 10 is a graph showing a graphic representation of the change in slant sensation felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 5, simulated with the horizontal axis representing the horizontal visual field and the vertical axis representing the vertical visual field. [Figure 27] 10 is a graph illustrating the magnitude of the slant sensation corresponding to the angle of view in the vertical field of view felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 5. [Figure 28] 10 is a graph illustrating the magnitude of the slant sensation corresponding to the angle of the oblique visual field felt when wearing eyeglass lenses for correcting oblique astigmatism in Example 5. [Figure 29] Average frequency distribution diagram of Comparative Example 1. [Figure 30] FIG. 10 is an astigmatism distribution diagram of Comparative Example 1. [Figure 31] 1 is a graph showing a graphic representation of the change in slant sensation felt when wearing eyeglass lenses for correcting oblique astigmatism in Comparative Example 1, simulated with the horizontal axis representing the horizontal field of view and the vertical axis representing the vertical field of view. [Figure 32] Average frequency distribution diagram of Comparative Example 2. [Figure 33] FIG. 10 is an astigmatism distribution diagram of Comparative Example 2. [Figure 34] 10 is a graph showing a graphic representation of the change in slant sensation felt when wearing eyeglass lenses for correcting oblique astigmatism in Comparative Example 2, simulated with the horizontal axis representing the horizontal field of view and the vertical axis representing the vertical field of view. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a spectacle lens of the present invention will be described below with reference to the drawings. The spectacle lens of this embodiment is obtained by cutting a semi-finished blank as a precursor lens by inputting processing data into an NC device, which is a processing device with a built-in computer, and controlling the computer by a program. The spectacle lens is an SV (single-vision) lens with a circular outer shape, known as a round lens, before being framed. The spectacle lens 1 is cut into a frame shape (edge shape) according to the user's request by a manufacturer or an eyeglass store.

[0012] <Processing method> This section describes an example of calculating processing data and processing eyeglass lenses. The following explanation focuses primarily on the design method (setting the toric surface) of eyeglass lenses for correcting oblique astigmatism according to the present invention. Data relating to the wearer's specific lens power, such as S power and prism, is set according to the wearer. The processing method of this embodiment is the standard method, and the eyeglass lenses used in the following examples and comparative examples also follow the standard method. Basically, the front surface (convex surface) is spherical, and the inner surface (concave surface) is an aspheric toric surface, and the inner surface is then processed. The processing uses sag data, which combines the aspheric surface shape data and the wearer's specific toric surface prescription shape data. The toric surface is designed based on the S power, C power, and astigmatism axis AX. When processing eyeglass lenses, sag is applied in a direction that passes through the geometric center of the lens surface and is perpendicular to the surface. The positive sag direction is from the lens toward the eyeball. The sag direction does not take into account the tilt of the lens when worn. The positive sag direction is from the lens toward the eyeball. The geometric center of the rear surface of the lens is the origin of coordinates. Consider a plane that passes through the origin and has the sag direction as its normal line. Within that plane, the direction horizontal to the direction of gravity is the x-axis, and the direction perpendicular to the x-axis is the y-axis. The positive direction of the y-axis is upward. The positive direction of the x-axis is toward the nose of the right eye. To provide the aspherical sag, for example, a rotationally symmetric sag function of the following equation (1) can be used.

[0013]

number

[0014] For the toric surface, in this embodiment, two types of sag are prepared: one based on the prescribed power (hereinafter referred to as the original prescription sag) and one that reduces the astigmatism of the original prescription (hereinafter referred to as the improved prescription sag), and the amount of sag is adjusted according to the distance from the center. The amount of sag of the toric surface can be expressed by the well-known general formula, Equation 2, below. Equation 2 is a well-known equation that represents a toric surface. Since Equation 2 is an approximate calculation formula, the center thickness of the lens is not used as a parameter. Equation 2 is only an example, and for more precise calculations, the center thickness may be used as a parameter. Prior art documents include, for example, Japanese Patent Laid-Open No. 2001-261846 and Japanese Patent No. 3852116. In the following equation (2), the inner surface principal curvatures are expressed as Cx = 1 / r1 and Cy = 1 / r2. Cx is the base curve, and Cy is the cross curve. The principal curvatures are the reciprocals of the principal radii of curvature. These principal curvature values are determined from the specified distance power, surface curvature, refractive index of the lens substrate, and center thickness of the lens. In this embodiment, two values of Cx and Cy are prepared according to two types of sag, and formulas for the amount of sag for two toric surfaces are obtained. In equation (2), x and y are calculated according to the angle θ of the astigmatic axis. For example, if the astigmatic axis is 180 degrees or 90 degrees, it is easy to calculate the formula Sf(x, y) representing the inner surface sag. However, if this is not the case, i.e., if it is oblique, the calculation is performed using a conversion formula for x and y according to the angle θ.

[0015]

number

[0016] There are several methods that can be used to allocate the original prescription sag and the improved prescription sag, but in this embodiment, two methods will be exemplified. (1) Sag synthesis As shown in Figure 1, sag1 and sag2 are synthesized in a predetermined area (here, due to machine limitations, an area of 48 mm x 48 mm is shown as an example) according to the distance and direction from the coordinate origin. Specifically, for standard points (x, y) evenly spaced at 8 mm intervals in a grid pattern, the amount of sag at each standard point (x, y) is calculated according to the distance and direction based on the following equation (3). Because it is necessary to determine coordinate values everywhere on the toric surface, spline interpolation calculations are performed using a known method based on the data of the calculated standard points (x, y), and the interpolated data values are used as the data values of the toric surface. In the following formula 3, if the center is the original prescription and the periphery is the improved prescription, sag1 is the original prescription and sag2 is the improved prescription. On the other hand, if the center is the improved prescription, sag1 is the improved prescription and sag2 is the original prescription.

[0017]

number

[0018] (2) Optimization calculation For example, as shown in Figure 2, the lens center power is set within an appropriate radius range (4-8 mm) from the center, and the remaining range is set to half the astigmatic power C-3.00 at the lens center. These values are for the following example. The spherical equivalent (S+C / 2) is set to be as close to the lens center as possible. Twenty-four points are arranged concentrically from the center at 15-degree intervals, and target and evaluation values are obtained in 1 mm increments within the appropriate radius range and in 4 mm increments beyond that. The target values are designed based on the prescribed S power, C power, and astigmatic axis AX. Meanwhile, the evaluation values are calculated based on the S power, C power, and astigmatic axis AX calculated by ray tracing simulation that passes through the center of rotation. The S power, C power, and astigmatic axis AX are normalized according to the Jackson cross cylinder to (S, C, AX) = (Mdp, J00, J45). The error is calculated for each corresponding coordinate so that the (Mdp, J00, J45) obtained by ray tracing in this way approaches the target (Mdp, J00, J45), and an optimization calculation is performed to determine the coordinates so that the error is minimized. For example, DLS (damped least squares method) can be used as the optimization calculation. The results obtained by optimization are used, for example, by spline interpolation to calculate the coordinates of various points and use them as the data values of the toric surface.

[0019] Next, we will explain the general formula for slant perception based on Figure 3 and equation 4. Figure 3 is a schematic diagram for explaining the general formula for calculating binocular disparity. Stereoscopic vision is possible due to the binocular disparity when viewing an object with both eyes. When looking at an object (here, an object screen, as illustrated in Figure 3) without glasses, the left and right eyes have a convergence angle on the object screen. In this case, the convergence angle at which the light reaches the object screen is defined as α. On the other hand, wearing glasses causes the optical axis to bend. The convergence angle at which the light reaches the object screen (the angle of incidence on the back surface of the lens) is defined as β. In equation 4, β - α is the binocular disparity Φ, and whether the image tilts toward the back or toward the front depends on whether the binocular disparity Φ is positive or negative. In other words, the slant sensation is a phenomenon that occurs when the binocular disparity Φ changes when the gaze is moved up or down. As explained in the background art, with lenses that correct oblique astigmatism, the convergence angle β is not constant depending on the direction of the gaze, resulting in the perception of slant sensation. In this embodiment, the distance between the nodal point and the center of rotation is 5.6 mm, the distance between the center of rotation and the rear surface of the lens is 25 mm, the visual distance D is 1 m, and the interpupillary distance IPD is 62 mm. Simulations were performed based on the perception principle of the slant feeling shown in the schematic diagram of Figure 3 to obtain examples and comparative examples. In the simulation, rays passing through the nodal points of each eye are traced from all binocular visual angle directions (θ), without considering rays passing through eye rotation. Specifically, the simulation was performed as follows. (1) Imagine a square area with a field of view of ±50 cm (±26 degrees field of view) 1 m ahead when viewed from the front, and collect coordinates within this area at specified intervals. (2) Find the exit angle from the nodal point of the ray (taking into account refraction at the front and back surfaces of the lens) connecting the nodal point to the coordinates on the object point screen. (3) Based on the exit angle from the nodal point obtained through the above, the convergence angle β is calculated for each eye, and based on the exit angle of the ray connecting the nodal point to an arbitrary point on the object screen when no lens is used, the convergence angle α is calculated for each eye. Binocular disparity Φ is found by ray tracing. (4) Based on the above calculation results, the binocular disparity required for the formula for calculating the slant feeling is calculated. (5) Applying parameters to the formula (4) calculates the slant on the coordinates, and then performing interpolation calculations between the coordinates to calculate the slant at each point.

[0020]

number

[0021] An example in which the slant feeling was simulated using a spectacle lens for correcting oblique astigmatism processed by the above-described processing method will be described below. Example 1 Example 1 is an example in which the lens back surface is designed using sag synthesis, and Example 1-1 is an example in which the central area is used as the original prescription and the periphery is used as the improved prescription. An example of specific lens data for the eyeglass lens of Example 1 is as follows. The improved power was reduced by 50% from the original prescription. Furthermore, as a reference for Example 1-1, Example 1-2 was an aspheric eyeglass lens with the same prescription power but without the improved prescription. (R eye side) Prescription power: S-0.00D C-3.00D AX45 ·Improvement degree S-0.75D C-1.50D AX45 (L eye side) Prescription power: S-0.00D C-3.00D AX135 ·Improvement degree S-0.75D C-1.50D AX135 ·Center thickness CT=1.9(mm) ·Substrate refractive index n = 1.600 Table curve: 4.58 curve (substrate refractive index equivalent) ·Surface curvature radius r0=1000·(n-1) / 4.58=131(mm) Surface curvature Co=1 / r0=0.00763(mm -1 ) ·Inner surface principal curvature Cx=(4.58-(-0.00)) / (1000·(n-1)) =0.00763(mm -1 ) Cy=(4.58-(-3.00)) / (1000·(n-1)) =0.01263(mm -1 )

[0022] FIG. 5(a) is a mean power distribution diagram for Example 1-1, and FIG. 5(b) is a mean power distribution diagram for Example 1-2. FIG. 6(a) is a mean power distribution diagram for Example 1-1, and FIG. 6(b) is a mean astigmatism distribution diagram for Example 1-2. In the following examples, the mean power distribution diagram and the astigmatism distribution diagram are shown only for the left eye side. FIG. 7 shows the results of a simulation of the slant sensation under these lens characteristics. In FIG. 7, the horizontal axis represents the horizontal field of view, and the vertical axis represents the vertical field of view (this also applies to the following examples). The color bar indicates the slant sensation, and the less gradation there is, i.e., the less difference there is between light and dark, the less the slant sensation is reduced. Compared to a spherical lens with the same prescription (Comparative Example 1) described below, both lenses have less gradation, indicating that the slant sensation is reduced. FIG. 8 compares the sense of slant at vertical viewing angles when Example 1-1 and Example 1-2 are superimposed. It can be seen that the sense of slant increases from the center toward the top and bottom. Compared to Example 1-2, Example 1-1, which has an improved prescription, showed an improvement of about 0.5 degrees. FIG. 9 compares the sense of slant at oblique viewing angles when Example 1-1 and Example 1-2 are superimposed. The oblique direction is the field of view from the upper left to the lower right, as shown in FIG. 10. Compared to Example 1-2, Example 1-1, which has an improved prescription, showed an improvement of about 4.5 degrees, mainly in the diagonally upward field of view.

[0023] Example 2 As with Example 1, Example 2 is an example in which the lens back surface is designed using sag synthesis, with the central area being the original prescription and the periphery being the improved prescription. An example of specific lens data for the eyeglass lens of Example 2 is as follows. As the improved power, the original prescription was reduced by 50%, and the astigmatism axis was shifted by 30 degrees. The crossing angle, which was 90 degrees before the displacement, became 30 degrees after the displacement. The only difference between the eyeglass lens of Example 2 and Example 1 is the astigmatic axis shift, so only the prescription power and improved power are listed as specific data for the eyeglass lens of Example 2. (R eye side) Prescription power: S-0.00D C-3.00D AX45 ·Improvement degree S-0.75D C-1.50D AX75 (L eye side) Prescription power: S-0.00D C-3.00D AX135 ·Improvement degree S-0.75D C-1.50D AX105

[0024] Fig. 11 is a diagram showing the average power distribution of Example 2. Fig. 12 is a diagram showing the astigmatism distribution of Example 2. Fig. 13 shows the results of simulating the slant feeling with these lens characteristics. Compared with a spherical lens with the same prescription, which will be described later, the gradation is reduced in both cases, and it can be seen that the slant feeling is reduced. FIG. 14 shows a comparison of the slant sensation at vertical viewing angles when Example 2 and Example 1-2 are superimposed. Compared to Example 1-2, Example 2, which has an improved prescription, showed an improvement of about 0.5 degrees. FIG. 15 shows a comparison of the slant sensation at oblique viewing angles when Example 2 and Example 1-2 are superimposed. Compared to Example 1-2, Example 2, which has an improved prescription, showed an improvement of about 7.0 degrees, mainly in the obliquely upward field of view. In other words, it can be seen that shifting the astigmatic axis by 30 degrees improves the slant sensation more than Example 1-1.

[0025] Example 3 Example 3 is an example in which the back surface of the lens is designed using optimization calculations, with the central area being the original prescription and the periphery being the improved prescription. An example of specific lens data for the eyeglass lens of Example 3 is as follows: As the improved power, the original prescription was reduced by 50% and the astigmatism axis was shifted by 30 degrees. The crossing angle, which was 90 degrees before the displacement, is now 30 degrees after the displacement. The lens data for the eyeglass lens of Example 3 is the same as Example 2, except that the design method for the back surface of the lens is different. To repeat, the prescribed power and improved power are listed below. (R eye side) Prescription power: S-0.00D C-3.00D AX45 ·Improvement degree S-0.75D C-1.50D AX75 (L eye side) Prescription power: S-0.00D C-3.00D AX135 ·Improvement degree S-0.75D C-1.50D AX105

[0026] Fig. 16 is an average dioptric power distribution diagram for Example 3. Fig. 17 is an astigmatism distribution diagram for Example 3. Fig. 18 shows the results of a simulation of slant perception with such lens characteristics. Compared with a spherical lens with the same prescription, which will be described later, both lenses have less gradation, and it can be seen that slant perception is reduced. Fig. 19 shows a comparison of the sense of slant at vertical viewing angles when Example 3 and Example 1-2 are overlapped. Compared to Example 1-2, Example 2, which has an improved prescription, showed an improvement of about 4.0 degrees. Fig. 20 shows a comparison of the sense of slant at oblique viewing angles when Example 3 and Example 1-2 are overlapped. Compared to Example 1-2, Example 3, which has an improved prescription, showed an improvement of reducing the sense of slant to about half, mainly in the diagonally upward viewing angle.

[0027] Example 4 Example 4 is an example in which the rear surface of the lens is designed using sag synthesis, with the central area being the improved prescription and the periphery being the original prescription. An example of specific lens data for the eyeglass lens of Example 4 is as follows: The improved power is a 50% reduction of the original prescription, and the astigmatism axis is not shifted. The lens data for the eyeglass lens of Example 4 is the same as that of Example 1, except for the design method for the rear surface of the lens. To repeat, the prescribed power and improved power are listed below. (R eye side) Prescription power: S-0.00D C-3.00D AX45 ·Improvement degree S-0.75D C-1.50D AX45 (L eye side) Prescription power: S-0.00D C-3.00D AX135 ·Improvement degree S-0.75D C-1.50D AX135

[0028] Fig. 21 is a diagram showing the average power distribution of Example 4. Fig. 22 is a diagram showing the astigmatism distribution of Example 4. Fig. 23 shows the results of simulating the slant feeling with such lens characteristics. Compared with a spherical lens with the same prescription, which will be described later, the gradation is reduced in both cases, and it can be seen that the slant feeling is reduced.

[0029] Example 5 Example 5 is an example in which the lens back surface is designed using sag synthesis, with the central portion being the original prescription and the periphery being the improved prescription. An example of specific lens data for the eyeglass lens of Example 5-1 is as follows. Example 5-1 has the same S power and C power as Examples 1 to 4 above, but the direction of the astigmatic axis AX is different. In addition, in the improved prescription, the left and right astigmatic axes AX are shifted in a shallower direction. The crossing angle, which was 44 degrees before the shift, becomes 11 degrees after the shift. Furthermore, as a reference for Example 5-1, Example 5-2 was an eyeglass lens with an aspherical lens and the prescribed power as is, without an improved prescription. (R eye side) Prescription power: S-0.00D C-3.00D AX68 ·Improvement degree S-0.45D C-2.10D AX86 (L eye side) Prescription power: S-0.00D C-3.00D AX112 ·Improvement degree S-0.45D C-2.10D AX97

[0030] Figure 24(a) is an average power distribution diagram for Example 5-1, and Figure 24(b) is an average power distribution diagram for Example 5-2. Also, Figure 25(a) is an astigmatism distribution diagram for Example 5-1, and Figure 25(b) is an astigmatism distribution diagram for Example 5-2. Figure 26 shows the results of a simulation of slant feeling with such lens characteristics. Compared with a spherical lens (Comparative Example 2) with the same prescription, which will be described later, both lenses have less gradation, and it can be seen that slant feeling is reduced. Figure 27 shows a comparison of the slant feeling at vertical viewing angles when Example 5-1 and Example 5-2 are overlapped. It can be seen that the slant feeling increases from the center toward the top and bottom. Compared to Example 5-2, Example 5-1, which has an improved prescription, showed an improvement of about 0.5 degrees. Figure 28 shows a comparison of the slant feeling at oblique viewing angles when Example 5-1 and Example 5-2 are overlapped. Compared to Example 5-2, Example 5-1, which has an improved prescription, showed an improvement of about 4.0 degrees, mainly in the diagonally upward viewing angle.

[0031] (Comparative Example 1) An example of specific lens data for the spectacle lens of Comparative Example 1 is as follows: Comparative Example 1 was a spherically designed lens with the same prescription power as in Examples 1 to 4, with no improved prescription. Again, write down the prescription strength. (R eye side) Prescription power: S-0.00D C-3.00D AX45 (L eye side) Prescription power: S-0.00D C-3.00D AX135

[0032] Fig. 29 is an average dioptric power distribution diagram for Comparative Example 1. Fig. 30 is an astigmatism distribution diagram for Comparative Example 1. Fig. 31 shows the results of simulating the slant feeling with these lens characteristics. With a spherical lens such as Comparative Example 1, the difference in shading is greater than in the above-mentioned Examples, and it can be seen that when this lens is worn, the slant feeling is greater than in the above-mentioned Examples.

[0033] (Comparative Example 2) An example of specific lens data for the spectacle lens of Comparative Example 1 is as follows: Comparative Example 1 was a spherically designed lens with the same prescription power as in Example 5, with no improved prescription. Again, write down the prescription strength. (R eye side) Prescription power: S-0.00D C-3.00D AX68 (L eye side) Prescription power: S-0.00D C-3.00D AX112

[0034] Fig. 32 is an average dioptric power distribution diagram for Comparative Example 1. Fig. 33 is an astigmatism distribution diagram for Comparative Example 2. Fig. 34 shows the results of a simulation of slant perception with these lens characteristics. With a spherical lens such as the Comparative Example, the difference in shading is greater than in the above Examples, and it can be seen that when this lens is worn, the slant perception is greater than in the above Examples.

[0035] The above examples are merely described as specific embodiments for illustrating the principles and concepts of the present invention. In other words, the present invention is not limited to the above embodiments. The present invention can also be embodied in modified forms, for example, as follows. The sag function of the aspheric surface and the design method of the toric surface in the above embodiment are merely examples, and other function formulas and design methods may be freely adopted. In the above embodiment, the aspherical element is added to the back surface, but it may also be added to the front surface. Furthermore, the present invention is not limited to adding the aspherical element to one surface, and adding the aspherical element to both surfaces is also included in the scope of the present invention. The present invention is applicable to both monochromatic and compound astigmatism as long as it corrects oblique astigmatism.

Claims

1. A method for designing eyeglass lenses to reduce the sense of slant that occurs when wearing eyeglass lenses for correcting oblique astigmatism, in which the astigmatism axis directions of left and right lenses intersect, comprising: A method for designing eyeglass lenses for correcting oblique astigmatism, characterized in that when the curve shape of at least one of the front and back surfaces of the left and right lenses is designed to be aspherical based on simulation results that reflect the slant obtained by calculation, the angle at which the astigmatic axis directions of the left and right lenses intersect is displaced in a direction that makes it shallower.

2. 2. The method for designing eyeglass lenses for correcting oblique astigmatism according to claim 1, wherein the eyeglass lenses have an area set to a correction power that reduces the astigmatic power in the original prescription powers of the left and right lenses.

3. 3. The method for designing eyeglass lenses for correcting oblique astigmatism according to claim 2, wherein the area set to the correction power obtained by reducing the astigmatism power in the original prescription powers of the left and right lenses is the central area of the lens.

4. 3. The method for designing eyeglass lenses for correcting oblique astigmatism according to claim 2, wherein the area set to the corrected power obtained by reducing the astigmatism power in the original prescription power of the left and right lenses is an area other than the central area of the lens.

5. 5. A method for designing eyeglass lenses for correcting oblique astigmatism according to claim 4, wherein the area set to the correction power obtained by reducing the astigmatism power in the original prescription powers of the left and right lenses is an area surrounding the periphery of the central area of the lens.

6. 6. The method for designing a spectacle lens for correcting oblique astigmatism according to any one of claims 2 to 5, wherein the astigmatism power of the original prescription power is reduced by up to 50%.

7. A method for designing eyeglass lenses for correcting oblique astigmatism as described in any one of claims 1 to 6, characterized in that the amount of angular displacement is in the range of 15 to 45 degrees.

8. 8. The method for designing eyeglass lenses for correcting oblique astigmatism according to any one of claims 1 to 7, characterized in that the corrective power obtained by reducing the astigmatic power in the original prescription powers of the left and right lenses is added to the back surfaces of the left and right lenses, and at least the back surfaces of the lenses are aspherical in design.

9. A method for manufacturing eyeglass lenses for correcting oblique astigmatism, characterized in that eyeglass lenses are manufactured by processing the lens surface based on design data obtained by a method for designing eyeglass lenses for correcting oblique astigmatism of any one of claims 1 to 8.

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