Contact lens manufacturing method and contact lens design method

Abstract

To provide a contact lens which enables correction of aberrations caused by a wearer's corneal shape.SOLUTION: A contact lens of the present invention has a lens front surface shaped such that light emitted from a reference point on an optical axis at a desired distance from a cornea posterior surface of a wearer and entering the inside of a desired lens area through the cornea is emitted in parallel with the optical axis.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a contact lens. Manufacturing method and a method for designing contact lenses. [Background technology]

[0002] Various methods for designing contact lenses to correct aberrations caused by abnormalities in the shape of the cornea have been developed (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2008-542831 [Patent Document 2] Special Publication No. 2003-506175 Summary of the Invention [Problem to be solved by the invention]

[0004] The design methods described in Patent Documents 1 and 2 do not provide sufficient correction of aberrations.

[0005] Contact lenses that allow correction of aberrations caused by the corneal shape of each wearer Manufacturing method It is desirable to provide a method for designing contact lenses. [Means for solving the problem]

[0006] A contact lens according to one embodiment of the present invention Manufacturing method teeth, The method includes the steps of: measuring the anterior and posterior corneal shapes of a contact lens wearer using a corneal topography analyzer; setting a reference point, which corresponds to an ideal lens focal position that enables correction of the wearer's eye disease, on the optical axis of the contact lens closer to the retina than the posterior corneal surface of the wearer; and calculating the shape of the anterior lens surface based on the measurement results of the anterior and posterior corneal shapes so that, when the contact lens is worn on the wearer's eyeball, for all virtual light rays that are virtually emitted from the reference point and incident on a desired lens region, the optical path length from the reference point to a plane perpendicular to the apex of the anterior lens surface is the same as the optical path length from the reference point on the optical axis to the apex of the anterior lens surface, and all virtual light rays are emitted parallel to the optical axis.

[0007] A method for designing a contact lens according to one embodiment of the present invention includes the steps of: measuring the anterior and posterior corneal shapes of a contact lens wearer using a corneal topography analyzer; setting a reference point on the optical axis of the contact lens that corresponds to an ideal lens focal position that makes it possible to correct the wearer's eye disease closer to the retina than the posterior corneal surface of the wearer; and calculating the shape of the anterior lens surface based on the measurement results of the anterior and posterior corneal shapes so that, with the contact lens attached to the wearer's eyeball, for all virtual light rays that are virtually emitted from the reference point and incident on a desired lens region, the optical path length from the reference point to a plane perpendicular to the apex of the anterior lens surface is the same as the optical path length from the reference point on the optical axis to the apex of the anterior lens surface, and all virtual light rays are emitted parallel to the optical axis; Includes:

[0008] A contact lens according to one embodiment of the present invention Manufacturing methodIn the contact lens design method, a virtual light ray is virtually emitted from a reference point on the optical axis at a desired distance from the posterior surface of the cornea of ​​the wearer, and enters the desired lens area through the cornea, and is then emitted from the front surface of the lens parallel to the optical axis. [Effects of the Invention]

[0009] According to a contact lens or a contact lens design method according to an embodiment of the present invention, a virtual ray of light is virtually emitted from a reference point on the optical axis located a desired distance from the posterior surface of the cornea of ​​a wearer, and enters a desired lens region through the cornea, and then emerges from the front surface of the lens parallel to the optical axis, thereby making it possible to correct aberrations resulting from the shape of the wearer's cornea, etc. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an explanatory diagram showing an overview of correction of eye vision. [Figure 2] FIG. 1 is an explanatory diagram schematically illustrating the image formation state of light rays in regular astigmatism. [Figure 3] FIG. 1 is an explanatory diagram schematically illustrating the imaging state of light rays in irregular astigmatism. [Figure 4] FIG. 1 is an explanatory diagram showing an overview of a normal cornea and a keratoconus. [Figure 5] FIG. 1 is an explanatory diagram showing an outline of a method for correcting irregular astigmatism. [Figure 6] FIG. 1 is an explanatory diagram showing an outline of a method for correcting irregular astigmatism. [Figure 7] FIG. 1 shows an example of the refractive power distribution of the anterior corneal surface (left image) and posterior corneal surface (right image) of an astigmatic eye (left eye) exhibiting the early stage of Stage 1 keratoconus. [Figure 8] FIG. 1 is a diagram showing an example of the refractive power distribution of the anterior corneal surface (left image) and the posterior corneal surface (right image) of a Stage 1 keratoconic eye (right eye). [Figure 9] FIG. 1 is a diagram showing an example of the refractive power distribution of the anterior corneal surface (left image) and the posterior corneal surface (right image) of a Stage 4 keratoconic eye (left eye). [Figure 10]FIG. 1 is a cross-sectional view of the cornea showing an example of a cross section of a Stage 4 keratoconic eye. [Figure 11] FIG. 1 is an explanatory diagram illustrating an overview of Snell's law. [Figure 12] FIG. 2 is an explanatory diagram showing an outline of an optical path length. [Figure 13] FIG. 1 is an explanatory diagram showing an overview of two-dimensional ray tracing by a contact lens design method according to an embodiment. [Figure 14] FIG. 1 is an explanatory diagram showing an overview of two-dimensional ray tracing by a contact lens design method according to an embodiment. [Figure 15] FIG. 2 is an explanatory diagram showing an example of parameters used in two-dimensional ray tracing by the contact lens design method according to one embodiment. [Figure 16] This is an explanatory diagram showing the analysis results of the cross-sectional shape of the protrusion of an eye with Stage 4 keratoconus, the lens shape designed based on the analysis results (top), and an image of its curved approximation (bottom). [Figure 17] This is a diagram showing the amount of aberration before and after lens wear in an astigmatic eye (Figure 7) with the early stages of Stage 1 keratoconus. [Figure 18] FIG. 10 is a diagram showing the amount of aberration before and after lens wear in a Stage 1 keratoconus eye (FIG. 8). [Figure 19] FIG. 10 is a diagram showing the amount of aberration before and after lens wear in a Stage 4 keratoconus eye (FIG. 9). [Figure 20] This figure shows the MTF before and after lens wear in an astigmatic eye (Figure 7) with early-stage Stage 1 keratoconus. [Figure 21] FIG. 10 is a graph showing the MTF before and after lens wear in a Stage 1 keratoconus eye (FIG. 8). [Figure 22] FIG. 10 is a graph showing the MTF before and after lens wear in a Stage 4 keratoconus eye (FIG. 9). [Figure 23] FIG. 10 is a diagram showing an example of the measurement results of the refractive power distribution of a corneal model lens alone. [Figure 24] FIG. 10 is a diagram showing an example of the measurement results of the refractive power distribution of a corrective lens alone. [Figure 25]FIG. 10 is a diagram showing an example of the measurement results of refractive power distribution when two corneal model lenses and two corrective lenses are superimposed. [Figure 26] FIG. 1 is a cross-sectional view showing an example of a method for designing a bifocal contact lens. [Figure 27] 1A to 1C are explanatory diagrams showing an application example of a contact lens design method according to an embodiment. [Figure 28] 1A to 1C are explanatory diagrams showing an application example of a contact lens design method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. The description will be made in the following order: 0. Comparative Examples and Background Art (Figs. 1 to 6) 1. One embodiment 1.1 Contact lens design method (Figures 7 to 25) 1.2 Modifications and application examples (Figs. 26 to 28) 1.3 Effects

[0012] <0. Comparative Examples and Background Art> For refractive errors, good vision is provided by correcting aberrations, which are optical characteristics of the eye, using ophthalmic lenses such as spectacle lenses or contact lenses that are prescribed according to the optical characteristics of the user's eyes.

[0013] However, while commonly used eyeglass lenses and contact lenses are suitable for correcting aberrations that cause myopia, hyperopia, presbyopia, and astigmatism, they are insufficient for correcting aberrations caused by irregular refractive surfaces due to abnormalities in the anterior or posterior corneal surface shape.

[0014] Furthermore, since the anterior and posterior corneal shapes are unique to each subject who requires aberration correction, in order to provide a higher quality of view (QOV), it is necessary to provide each subject with ophthalmic lenses that have a corrective effect that is tailored to their corneal shape.

[0015] Therefore, various studies have been conducted to provide ophthalmic lenses for correcting aberrations caused by abnormal corneal shapes, and for example, a method has been proposed in which the aberrations of the entire cornea are corrected by estimating the shape of the posterior corneal surface from the shape of the anterior corneal surface measured using corneal topography (see Patent Document 1). Also, a method has been proposed in which the aberrations of the entire ocular optical system are corrected from the aberrations of the entire ocular optical system and the aberrations of the anterior corneal surface measured using a wavefront sensor and corneal topography (see Patent Document 2).

[0016] However, the method proposed in Patent Document 1 is applicable only in limited cases where the correlation between the anterior corneal shape and the posterior corneal shape is not applicable in all cases, and therefore has problems in terms of versatility. Furthermore, in the method proposed in Patent Document 2, the only aberration that can be measured by the wavefront sensor is the aberration on the optical axis. Therefore, even if a contact lens is formed based on the proposed method, the contact lens can only correct the aberration on the optical axis. Therefore, the correction effect for aberrations caused by light rays from angles other than the optical axis is insufficient, making it difficult to obtain a good image. Furthermore, consideration must be given to the positional stability of the contact lens with respect to rotational and translational movements when worn.

[0017] Figure 1 shows an overview of eye vision correction. Figure 2 shows a schematic representation of how light rays incident on an eyeball 10 form an image in the case of regular astigmatism. Figure 3 shows a schematic representation of how light rays incident on an eyeball 10 form an image in the case of irregular astigmatism.

[0018] As shown in Figure 1, myopia, hyperopia, etc. can be corrected with existing general ophthalmic lenses. Regular astigmatism can be corrected with existing general astigmatism lenses. Irregular astigmatism must be corrected with irregular astigmatism lenses.

[0019] Figure 4 shows an overview of a normal cornea (A) and keratoconus (B). Figure 5 shows an overview of the method for correcting irregular astigmatism. Irregular astigmatism can occur due to eye diseases or injuries, such as keratoconus. Keratoconus is an eye disease in which the cornea (11) thins near the center and protrudes forward in a conical shape. Lenses for irregular astigmatism include spherical hard contact lenses, wavefront aberration contact lenses, and scleral lenses. Spherical hard contact lenses have two- or three-point contact with the anterior corneal surface, making them uncomfortable to wear. Wavefront aberration contact lenses are designed to cancel the measured wavefront aberration. Scleral lenses achieve the same effect as tear lenses by filling the space between the posterior lens surface and the anterior corneal surface with artificial tears. However, the wavefront aberration contact lenses and scleral lenses developed to date have been insufficient in terms of vision correction. Wavefront aberration contact lenses are difficult to apply to eyes with large changes in corneal shape due to the ambiguity in the selection of wavefront aberration terms and their sensitivity to the measurement environment. In addition, with regard to scleral lenses, depending on the material, the cornea may be exposed to extremely hypoxic conditions, and artificial tears may need to be replaced multiple times while wearing them. Contact lenses that utilize wavefront aberration and scleral lenses have been reported to effectively correct higher-order aberrations, but do not provide good visual acuity.

[0020] Therefore, it is desirable to develop contact lenses that can correct aberrations caused by abnormalities in the anterior or posterior corneal shape, and that can more easily correct aberrations suited to the corneal shape of each individual patient.It is also desirable to develop a method for designing such contact lenses.

[0021] <1. One embodiment> [1.1 Contact lens design method] One embodiment of the present invention relates to a contact lens and a method for designing the contact lens, and more particularly to a contact lens that reduces corneal aberrations to improve quality of vision (QOV), and a method for designing the contact lens.

[0022] Figure 6 shows an overview of the method for correcting irregular astigmatism. In order to solve the above-mentioned problems, the inventors of the present application have been investigating ways to eliminate aberrations caused by irregular astigmatism, and have found that contact lens 1, in which the front and back surfaces of the lens are individually designed and formed, can easily correct aberrations caused by abnormalities in corneal shape in a manner appropriate to the corneal shape of each individual subject.

[0023] (Design method overview) A mathematical model has been reported for lens design that eliminates spherical aberration and astigmatism through 3D ray tracing by keeping the optical path length constant (Rafael G. Gonzalez-Acuna, Hector A. Chaparro-Romo et al: General formula to design a freeform singlet free of spherical aberration and astigmatism. Applied Optics 58(4): 1010-1015, 2019). The report describes the results of 3D ray tracing simulations for various freeform shapes, using the condition that all rays have the same optical path length when tracing rays. By keeping the optical path length constant, the focal point of each ray can theoretically be set to a single point. In other words, it is possible to design a lens that is free of aberrations. However, the report only focuses on spherical aberration and astigmatism, and from the perspective of contact lens design, while spherical aberration can generally be corrected by providing asphericity using the Conic constant and astigmatism can be corrected with an astigmatism lens, the report is insufficient in terms of correcting aberrations other than spherical aberration and astigmatism.

[0024] Therefore, in this embodiment, we propose a new contact lens design method that reduces corneal aberrations using corneal anterior and posterior surface shape data obtained by OCT (Optical Coherence Tomography), a corneal topography analysis device. When designing the contact lens, we used corneal anterior and posterior surface shape data obtained by CASIA (registered trademark), an anterior segment OCT. Regarding ray tracing, we devised a method using two-dimensional ray tracing, taking into account that OCT is a tomographic measurement.

[0025] 7 to 10 show examples of corneas 11 to be analyzed by OCT. The subjects analyzed were an astigmatic eye (left eye) showing the early stages of Stage 1 keratoconus, an eye (right eye) with Stage 1 keratoconus, and an eye (left eye) with Stage 4 keratoconus. As will be described later, the results of the analyzed front and rear surface shapes of the cornea 11 and contact lens 1 were input as grid data into OpticStudio Zemax (registered trademark), an optical simulation software, and the effectiveness of the design method for contact lens 1 according to this embodiment was evaluated.

[0026] FIG. 7 shows an example of the refractive power distribution of the anterior corneal surface (left diagram) and posterior corneal surface (right diagram) of an astigmatic eye (left eye) showing the early stages of Stage 1 keratoconus. FIG. 8 shows an example of the refractive power distribution of the anterior corneal surface (left diagram) and posterior corneal surface (right diagram) of an eye (right eye) with Stage 1 keratoconus. FIG. 9 shows an example of the refractive power distribution of the anterior corneal surface (left diagram) and posterior corneal surface (right diagram) of an eye (left eye) with Stage 4 keratoconus. FIG. 10 is a corneal cross-sectional view showing an example of a cross-section of an eye with Stage 4 keratoconus.

[0027] In this embodiment, when designing a lens, height data of the anterior and posterior corneal surfaces was used as output data from OCT, which is capable of measuring corneal shape even when aberration cannot be measured with a wavefront sensor. The reason for selecting anterior segment OCT is that it is possible to measure not only the shape of the anterior corneal surface but also the shape of the posterior corneal surface, and it was determined that this would enable more practical lens design.

[0028] The measurement data was in the form of 32 directions (16 slices of corneal cross-sectional information) at an angle of 11.25° each, with a radius of 5.1 mm. Figures 7 to 9 show data for a 10 mm diameter. The units of values ​​in Figures 7 to 9 are diopters (D). The maximum refractive power of the anterior corneal surface in the astigmatic eye was 44.9 D, while the maximum refractive powers of the Stage 1 and Stage 4 keratoconus eyes were 49.4 D and 71.7 D, respectively. The maximum refractive power of the posterior corneal surface in the astigmatic eye was -6.4 D, while the maximum refractive powers of the Stage 1 and Stage 4 keratoconus eyes were -8.2 D and -13.3 D, respectively. Figure 10 shows a corneal cross-section in the direction where Stage 4 protrusion of the cone was observed. Figure 10 shows that the curvature of the posterior corneal surface differs between the left and right sides, and that the corneal thickness is thinner near the center. At the same time, it is clear that a design that takes the shape of the posterior corneal surface into consideration is necessary.

[0029] (Details of the design method) Next, a specific example of a method for designing a contact lens 1 according to this embodiment will be described with reference to Figs. 11 to 15. Fig. 11 shows an outline of Snell's law. Fig. 12 shows an outline of optical path length. Figs. 13 and 14 show an outline of two-dimensional ray tracing according to this design method. Fig. 15 shows an example of parameters used in two-dimensional ray tracing according to this design method.

[0030] The method for designing the contact lens 1 according to this embodiment has the following features. (1) The front surface of the lens CLf is located at a reference point Z on the optical axis Za at a desired distance from the wearer's posterior corneal surface Cr. C The shape is such that a virtual light ray is virtually emitted from the reference point Z and enters the desired lens area through the cornea 11, and is emitted parallel to the optical axis Za (see FIGS. 13 and 14). C For example, the desired lens area may be a point on the retina. Note that the desired lens area is, for example, an area within the effective diameter of the lens. (2) The posterior lens surface CLr has the same shape as the wearer's anterior corneal surface Cf. However, the posterior lens surface CLr may have a shape that is close to the shape of the wearer's anterior corneal surface Cf, rather than being completely identical. (3) The shape of the front surface of the lens CLf is determined by ray tracing according to Snell's law (see Figure 11) at the reference point Z C The calculation is based on information on the coordinate positions and angles of the virtual light rays emitted from the cornea as they pass through the posterior corneal surface Cr, the anterior corneal surface Cf, the tear film 12, and the posterior lens surface CLr (see Figures 13 and 14). (4) When the lens is attached to the wearer's eyeball 10, the reference point Z C For all virtual rays that are virtually emitted from the reference point Z and incident on the desired lens area, C The optical path length (OP1 to OP5 in FIG. 13) from the reference point Z on the optical axis Za to the plane perpendicular to the vertex P1 of the lens front surface CLf is C The optical path length L from the lens front surface CLf to the vertex P1 C (See Figure 14) The optical path length is the distance that light travels in a vacuum in the same amount of time as it travels through a medium, and is expressed as the product nd, where n is the refractive index of the medium and d is the distance (path) (See Figure 12).

[0031] In this design method, in order to calculate a more practical lens shape, not only are the optical path lengths of the light rays made the same, but the corneal posterior surface Cr and tear film 12, which were not previously considered, are used in the analysis, and wearing comfort is also taken into consideration by designing the shape of the lens posterior surface CLr to be the same as the corneal anterior surface Cf so that it is surface contact rather than point contact like with conventional spherical hard contact lenses. Furthermore, since it has been reported that by making the shapes of the lens posterior surface CLr and the corneal anterior surface Cf the same, the lens will return to its original position even if it moves due to blinking, etc., a design innovation was made to ensure axial stability, and the shape of the lens anterior surface CLf in the optimal position was calculated.

[0032] In the schematic diagram of the two-dimensional ray tracing method shown in FIG. 13, n1 is the refractive index of the aqueous humor (e.g., 1.336), n2 is the refractive index of the cornea (e.g., 1.376), n3 is the refractive index of the tear fluid (e.g., 1.336), and n4 is the refractive index of the lens (e.g., 1.455) (see FIG. 15). Regarding the thickness of the tear film 12, the thickness under the lens varies depending on the case. However, in this embodiment, since the shape of only the optical surface is calculated and the anterior corneal surface Cf and the posterior lens surface CLr have the same shape, it is assumed that the thickness variation is small, and the thickness of the tear film 12 is set to a constant value of 0.01 mm (see FIG. 15). Furthermore, assuming a hard contact lens as the type of lens, a lens center thickness of 0.2 mm is used (see FIG. 15). Regarding ray tracing, the retinal position is determined as a reference point Z C The calculations were made to start with a point where parallel light is emitted from the front surface of the lens CLf. However, this design method is not limited to cases where parallel light is emitted, and it is also possible to design light rays that are emitted to have a focal point at a certain position.

[0033] In FIG. 13, the light ray first passes through the reference point Z on the optical axis Za. C The divergent light is emitted from the posterior corneal surface Cr and enters each posterior corneal surface coordinate measured by OCT. After the light reaches the posterior corneal surface Cr, a cubic curve is used to calculate the normal vector at that point of incidence. The normal vector is calculated by differentiating this approximate curve, and the angle of incidence θ is determined by calculating the dot product with the unit vector of the incident light. The angle of refraction θ' is then calculated according to Snell's law. Using a similar method, ray tracing was performed from the posterior corneal surface Cr to the anterior corneal surface Cf and from the anterior corneal surface Cf to the posterior lens surface CLr (tear film 12).

[0034] Here, we will show how to calculate the shape coordinates of the lens front surface CLf. In this design method, as mentioned above, the sum of the optical path lengths on the optical axis Za (reference point Z C The optical path length from the reference point Z to the vertex P1 of the lens front surface CLf was calculated, and the optical path lengths of other rays were calculated in the same way. CThe refractive index was calculated by multiplying and adding the refractive indexes of (retinal position) to the posterior corneal surface Cr (OP1), the posterior corneal surface Cr to the anterior corneal surface Cf (corneal thickness) (OP2), the anterior corneal surface Cf to the posterior lens surface CLr (tear film 12) (OP3), and the posterior lens surface CLr to the anterior lens surface CLf (lens center thickness) (OP4). C Since the optical path length (OP1 to OP3) from the retina to the lens posterior surface CLr can be calculated, the optical path lengths of OP4 and OP5 can be calculated by subtracting the sum of the optical path lengths. The slope m of the refracted light ray at the lens posterior surface CLr calculated using this optical path length and Snell's law is h The coordinates (x2, z2) of the lens front surface CLf can be calculated from the coordinates (x1, z1) of the lens rear surface CLr (see FIG. 14).

[0035] The coordinates (x2, z2) of the lens front surface CLf can be calculated as follows. L C =L1+d1n4+d2 L C =L1+d1n4+(L2-d1cosθ a ) d1=(L C -L1-L2) / (n4-cosθ a ) x2=x1+d1 / (1+m h 2 ) 1 / 2 z2=m h (x2-x1)+z1 where: L C : Optical path length from the retina to the lens vertex P1 L1: Optical path length from the retina to the lens posterior surface CLr L2: Optical path length from the lens rear surface CLr to the lens vertex P1 m h : Inclination of refracted rays from the lens rear surface CLr n4: Refractive index of the lens Let's say.

[0036] (Lens performance evaluation) Figure 16 shows the analysis results of the cross-sectional shape of the protrusion of a Stage 4 keratoconic eye (cross-sectional shapes in the 68° and -248° directions), the lens shape designed based on the analysis results (top), and an image of its curved surface approximation (bottom).

[0037] Looking at the lens shape in the cross-sectional direction shown in the upper part of Figure 16, it can be seen that the lens shape is not a wavy, free-form shape even at the position where the conical protrusion was observed in Stage 4. This is because, even at the position where the protrusion of the posterior corneal surface Cr is steep, there is almost no difference in the refractive index between the cornea 11 and the aqueous humor, so there is no difference in the optical path length and the lens is formed as a simple curve.

[0038] To convert the coordinates of the anterior and posterior corneal surfaces and the coordinates of the anterior and posterior lens surfaces into a format suitable for input into the optical simulation software OpticStudio Zemax, 32-directional data was used for 3D surface approximation and grid data was generated, as shown in the lower part of Figure 16. The OCT measurement data has a radius of 5.1 mm, but the peripheral area contains a lot of noise. Furthermore, considering the use of an approximated curve and approximated surface in this embodiment, it is expected that the accuracy of the peripheral area will be poor. Therefore, the grid data was limited to a side of 4 mm, with a grid step of 0.01 mm. In this embodiment, lens performance was evaluated using the amount of aberration and the modulation transfer function (MTF) before and after wearing the lens at the optimal positional relationship where the lens center and the corneal center coincide.

[0039] Figure 17 shows the amount of aberration before and after lens wear in an astigmatic eye with early-stage Stage 1 keratoconus (Figure 7). Figure 18 shows the amount of aberration before and after lens wear in an eye with Stage 1 keratoconus (Figure 8). Figure 19 shows the amount of aberration before and after lens wear in an eye with Stage 4 keratoconus (Figure 9). Figure 20 shows the MTF before and after lens wear in an astigmatic eye with early-stage Stage 1 keratoconus (Figure 7). Figure 21 shows the MTF before and after lens wear in an eye with Stage 1 keratoconus (Figure 8). Figure 22 shows the MTF before and after lens wear in an eye with Stage 4 keratoconus (Figure 9).

[0040] Figures 17 to 19 and 20 to 22 show the amount of aberration and MTF for each eye before and after wearing the lens, calculated at a wavelength of 0.546 μm and a pupil diameter of 4 mm. In Figures 17 to 19, the Zernike coefficients were calculated using the Zernike Standard Polynomial and are shown from Z3 to Z14 on the scale of the Optical Society of America (OSA). The results in Figures 17 to 19 and 20 to 22 show the amount of aberration and MTF at the lens imaging position in the optimal positional relationship where the center of the lens and the center of the cornea coincide.

[0041] (Aberration amount) Regarding the amount of aberration of the astigmatic eye shown in Figure 17, Z3, which indicates the astigmatic component, was at a maximum of -0.644 μm before wearing the lens, but after wearing the lens, it was greatly improved to 0.001 μm. Regarding the other terms, Z4 to Z7 also had aberrations of about ±0.1 μm, but after wearing the lens, each showed improvement. Here, the amounts of aberration from the third to fifth orders are collectively expressed as the RMS value (RMS=√(Z1 2 +···+Zn 2 )) the mean diameter before wearing the lenses was 0.689 μm, while after wearing the lenses it was 0.025 μm.

[0042] The aberration amount of the Stage 1 keratoconus eye shown in Figure 18 was a maximum of -0.928 μm for Z5 before wearing the lenses, but improved to -0.057 μm after wearing the lenses. The other terms were larger than those of the astigmatic eye, with Z3 being -0.541 μm, Z4 being 0.458 μm, and Z6 being -0.332 μm, but all of these improved to -0.010 μm for Z3, -0.062 μm for Z4, and -0.037 μm for Z6. The RMS value of the aberration amounts from the third to fifth orders was 1.229 μm before wearing the lenses, but decreased to 0.102 μm after wearing the lenses.

[0043] Regarding the aberration amounts in a Stage 4 keratoconic eye shown in Figure 19, the overall scale of aberration amounts is larger than that of an astigmatic eye or a Stage 1 keratoconic eye due to greater corneal shape changes. Before lens wear, Z4 was the largest at 4.299 μm, Z3 was −2.992 μm, and Z5 was 1.151 μm, indicating large defocus and astigmatism components. Furthermore, Z7 and Z8, the coma aberration components characteristic of keratoconic eyes, were −1.059 μm and 0.269 μm, respectively. After lens wear, Z4 improved to 0.195 μm, Z3 to −1.068 μm, and Z5 to −0.208 μm. Furthermore, although the aberration amounts increased in Z6 and Z10, the coma aberration characteristic of keratoconic eyes improved to −0.381 μm for Z7 and −0.046 μm for Z8. The RMS value was 5.483 μm before wearing the lenses, but it became 1.273 μm after wearing the lenses.

[0044] (MTF) 20 to 22, the dashed line indicates the MTF results when no lens is worn, and the solid line indicates the MTF results when a lens designed by this method is worn. Furthermore, in Fig. 22, the dashed line indicates the MTF results when a spherical hard contact lens (HCL) is worn. * indicates the MTF in the tangential direction, and + indicates the MTF in the sagittal direction.

[0045] Although the present embodiment does not take into consideration the crystalline lens, assuming an ideal lens with no aberration, it is generally estimated that if the MTF is 0.1 when the spatial frequency is 100 cycles / mm, the visual acuity is 1.0. This index is used for evaluation here.

[0046] In the astigmatic eye shown in Figure 20, before wearing the lenses, the MTF in the tangential direction was 0.009 and in the sagittal direction was 0.016 at a spatial frequency of 100 cycles / mm. However, after wearing the lenses, the MTF improved to 0.304 in the tangential direction and 0.280 in the sagittal direction. From this, assuming that the crystalline lens has no aberration, it is predicted that the visual acuity will be 1.0 or higher. Furthermore, since the MTF in both directions has the same tendency, it is thought that the same contrast and visual acuity will be obtained.

[0047] In the Stage 1 keratoconus eye shown in Figure 21, before wearing the lenses, the MTF in the tangential direction was 0.037 and in the sagittal direction was 0.001 at a spatial frequency of 100 cycles / mm, but after wearing the lenses, the MTF improved to 0.117 in the tangential direction and 0.212 in the sagittal direction. Although there is a difference in both directions, assuming that there is no aberration in the crystalline lens, the visual acuity is expected to be 1.0 or higher.

[0048] In the Stage 4 keratoconus eye shown in Figure 22, before lens wear, the tangential MTF was 0.001 and the sagittal MTF was 0.003 at a spatial frequency of 100 cycles / mm. Both MTFs were below 0.01, clearly indicating poor contrast and visual acuity. In contrast, with lens wear, the tangential MTF improved to 0.075 and the sagittal MTF improved to 0.038. With lens wear, the MTF value at a spatial frequency of 50 cycles / mm is expected to translate to visual acuity of approximately 0.4-0.5. Furthermore, compared with spherical hard contact lenses, spherical hard contact lenses were slightly superior in the low-frequency range, but lenses designed using this method were superior in the high-frequency range.

[0049] As described above, the design method for contact lens 1 according to the present embodiment has proven effective in correcting aberrations. Furthermore, MTF also showed improvement before and after wearing the lenses, suggesting improvement in visual acuity even for eyes with significant corneal shape changes.

[0050] (Example) Measurements were taken using a corneal shape measuring device, and a lens (corneal model lens) made from the actual measurements and contact lens 1 (corrective lens) made from coordinate data analyzed using this design method were measured using a power mapping device.

[0051] Figure 23 shows an example of the measurement results of the refractive power distribution of a corneal model lens alone. Figure 24 shows an example of the measurement results of the refractive power distribution of a corrective lens alone. Figure 25 shows an example of the measurement results of the refractive power distribution when two corneal model lenses and two corrective lenses are stacked together. As can be seen from Figure 25, it was confirmed that the refractive power distribution of the corneal model lens alone was corrected by the corrective lens manufactured based on this design method.

[0052] (summary) As described above, the design method for contact lens 1 according to this embodiment corrects aberrations even for complex corneal shapes, and its effectiveness was confirmed by the MTF. Conventional contact lens design methods for correcting irregular astigmatism utilize wavefront aberration. Wavefront aberration is characterized by ambiguity in the selection of terms used and is highly sensitive to the measurement environment. Wavefront sensors that measure wavefront aberration using the Shack-Hartmann principle are difficult to apply to eyes with significant corneal shape changes, such as eyes with Stage 4 keratoconus. The same is true for corneas 11 with ocular damage. This design method utilizes optical coherence tomography (OCT), which is effective for such eyes, to obtain the anterior and posterior corneal shapes, making it an advantageous method for application to any shape. Furthermore, hard or custom-made contact lenses are desirable for correcting irregular astigmatism. With hard contact lenses, correction is achieved by utilizing the effect of a tear lens. However, with custom-made contact lenses, accurate measurement of the anterior and posterior corneal shapes and axial length is desirable because each individual's corneal shape is different. This design method is a contact lens design that takes into account not only the anterior corneal surface Cf but also the posterior corneal surface Cr and tear film 12, and is effective based on the results of aberration amount and MTF. Furthermore, to eliminate the discomfort caused by point contact between the lens and the corneal protrusion that occurs in eye diseases such as keratoconus, this design method designs the shape of the posterior lens surface CLr to be the same as the shape of the anterior corneal surface Cf. This changes from point contact to area contact, and is expected to improve wearing comfort.

[0053] In this design method, the optical path length is kept constant and the shape of the contact lens 1 is calculated. This theoretically leads to a single focal point with zero aberration. However, some aberration remains, especially in subjects with significant corneal shape changes. This is because the calculation is performed using a surface approximation for areas not measured by the anterior segment OCT (CASIA). This may have affected the results in subjects with significant corneal shape changes, resulting in a steeper interpolated surface. This design method used Stage 2 keratoconus eyes as an example. As the degree of corneal protrusion increases, the shape change in the rotational direction (the circumferential direction of the cornea 11) increases. Analysis was performed using 2D ray tracing to correspond to the OCT tomographic measurements. When inputting the data into the optical simulation software, 3D surface approximation was performed using 32-directional tomographic data to create grid data. Because the data used was in 11.25° increments, data was interpolated for unmeasured positions using a 3D surface approximation formula when creating the grid data. In eyes with large rotational corneal shape changes, such as those with keratoconus, the interpolation position becomes a steeply curved surface, which is thought to have affected the results. In particular, for eyes with Stage 4 keratoconus, based on the wavefront shape and aberration amount, the defocus component improved, but some aberrations in the trefoil component increased. Therefore, when applying this method to eyes with large shape changes, such as those with ocular disease, it is recommended to consider the optimal interpolation method and reduce the rotation angle in OCT measurements. Furthermore, while this design method performed 2D ray tracing for each slice of the 3D OCT shape data, it is also recommended to perform 3D ray tracing analysis.

[0054] [1.2 Modifications and application examples] In the design method described above, the focal position (reference point Z C ) is one, but it is also possible to design a multifocal lens with two or more foci for the effective diameter. In this case, the reference point Z C This can be achieved by setting multiple

[0055] As an example of a method for designing a multifocal lens, an example of a method for designing a bifocal contact lens 1A is shown schematically in Figure 26. Note that it is also possible to design a multifocal lens with three or more foci by including three or more lens regions as the desired lens region and setting three or more reference points corresponding to each of the three or more lens regions as the reference points.

[0056] The bifocal contact lens 1A includes, as desired lens regions, a first lens region 101 and a second lens region 102 within the effective diameter, for example. In this design method, a reference point Z C The first reference point Z on the optical axis Za corresponding to the first lens area 101 is C 1 and a second reference point Z on the optical axis Za corresponding to the second lens area 102. C Set 2 and .

[0057] The lens design method for each region is the same as the lens design method described above. The shape of the lens front surface CLf corresponding to the first lens region 101 is determined by the first reference point Z C The shape of the lens front surface CLf corresponding to the second lens region is such that the light beams (light beams in the first light beam region 111) emitted from the second reference point Z a and incident on the first lens region 101 through the cornea 11 are emitted parallel to the optical axis Za. C The lens posterior surface CLr has the same shape as the wearer's anterior corneal surface Cf in both the first lens region 101 and the second lens region 102.

[0058] 27 and 28 show application examples of the method for designing contact lens 1 according to this embodiment.

[0059] According to the method for designing contact lenses 1 of this embodiment, as shown in FIG. 27, by reflecting the actual corneal shape data 20, tear film data 21, and other data 22 for each wearer in the design, it is possible to produce contact lenses 1 customized for each individual, with the corrective power for each individual's eye aberrations and vision.

[0060] Furthermore, by storing the design data 20 of this personalized contact lens 1 in a database 31 (see Figure 28), it becomes possible to investigate the characteristics and trends of each disease and its severity. For custom-made lenses, storing the designed lens shapes in a database allows designers to investigate trends by eye disease and its severity, potentially leading to new lens design concepts. This design method may also be applicable to the optical analysis of major corneal diseases, such as bullous keratopathy, corneal herpes, post-corneal ulcer, Stevens-Johnson syndrome, post-corneal transplant, post-traumatic corneal scarring, corneal dystrophy, keratoconus, and corneal phlyctenular disease. When applying this design method to individual contact lens fabrication, it is desirable to calculate the average corneal power in the center and determine the starting position of ray tracing to achieve that power. While this design method does not take into account lens aberrations, if the lens has astigmatism, it is possible to incorporate astigmatism correction into the design. In this case, the starting position of ray tracing can be set to a different position for each angle, taking into account the power distribution of the crystalline lens. Furthermore, as mentioned above, this design method also makes it possible to create a multifocal contact lens 1A. The freedom of design in this design method can be an advantage in basic research.

[0061] [1.3 Effects] As described above, according to the contact lens 1 and the method for designing the contact lens 1 of the present embodiment, a reference point Z CThe light beam is emitted from the lens and enters the desired lens area through the cornea 11, and then emerges from the front surface of the lens parallel to the optical axis. This makes it possible to correct aberrations caused by the wearer's corneal shape, etc. [Explanation of symbols]

[0062] 1,1A...contact lens, 10...eyeball, 11...cornea, 12...tear film, 20...corneal shape data, 21...tear film data, 22...other data, 30...design data, 31...database, 101...first lens region, 102...second lens region, 111...first light ray region, 112...second light ray region, CLf...lens front surface, CLr...lens rear surface, Cr...corneal rear surface, Cf...corneal front surface, L C …Reference point Z C The optical path length from the lens surface to the vertex P1 of the lens front surface CLf, P1...vertex P1 of the lens front surface CLf (lens vertex), Z C …Reference point, Z C 1...first reference point, Z C 2...second reference point, Za...optical axis.

Claims

1. A step of measuring the anterior corneal shape and posterior corneal shape of a contact lens wearer using a corneal topography analyzer; a step of setting a reference point corresponding to an ideal lens focal position that can correct the eye disease of the wearer on the optical axis of the contact lens, closer to the retina than the posterior surface of the cornea of ​​the wearer; a step of calculating the shape of the front surface of the lens based on the measurement results of the anterior corneal surface shape and the posterior corneal surface shape so that, with the contact lens attached to the eyeball of the wearer, for all virtual light rays that are virtually emitted from the reference point and incident on a desired lens area, the optical path length from the reference point to a plane perpendicular to the vertex of the front surface of the lens is the same as the optical path length from the reference point on the optical axis to the vertex of the front surface of the lens, and all the virtual light rays are emitted parallel to the optical axis; Contains A method for manufacturing contact lenses.

2. The method further includes a step of forming the posterior surface of the lens into a shape that is the same as or similar to the anterior corneal shape of the wearer. The method for manufacturing the contact lens according to claim 1 .

3. In the step of calculating the shape of the front surface of the lens, the shape of the front surface of the lens is calculated by ray tracing according to Snell's law based on information on the coordinate positions and angles of the virtual ray emitted from the reference point when it passes through the posterior surface of the cornea, the anterior surface of the cornea, the tear film, and the rear surface of the lens. The method for manufacturing a contact lens according to claim 1 or 2.

4. The reference point includes at least the intersection of the optical axis and the retina. The method for manufacturing a contact lens according to any one of claims 1 to 3.

5. The desired lens region includes at least a first lens region and a second lens region, In the step of setting the reference points, at least a first reference point on the optical axis corresponding to the first lens region and a second reference point on the optical axis corresponding to the second lens region are set as the reference points, the first reference point being an intersection of the optical axis and the retina, and the second reference point being a position on the optical axis between the posterior surface of the cornea and the retina, or a position behind the retina; In the step of calculating the shape of the lens front surface, the shape of the lens front surface corresponding to the first lens region is set to a shape such that a virtual ray that is virtually emitted from the first reference point and enters the first lens region through the cornea is emitted parallel to the optical axis, The shape of the lens front surface corresponding to the second lens region is set to a shape such that a virtual ray of light that is virtually emitted from the second reference point and enters the second lens region through the cornea is emitted parallel to the optical axis. The method for manufacturing a contact lens according to any one of claims 1 to 4.

6. Measuring the anterior and posterior corneal shapes of a contact lens wearer using a corneal topography analyzer; Setting a reference point corresponding to an ideal lens focal position that can correct the eye disease of the wearer on the optical axis of the contact lens closer to the retina than the posterior surface of the cornea of ​​the wearer; calculating the shape of the front surface of the lens based on the measurement results of the anterior corneal surface shape and the posterior corneal surface shape so that, with respect to all virtual light rays that are virtually emitted from the reference point and incident on a desired lens area, the optical path length from the reference point to a plane perpendicular to the vertex of the front surface of the lens is the same as the optical path length from the reference point on the optical axis to the vertex of the front surface of the lens, and all the virtual light rays are emitted parallel to the optical axis when the contact lens is worn on the eyeball of the wearer; Contains How contact lenses are designed.

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