A method for designing myopia prevention and control contact lenses based on modulation transfer function area distribution method

Abstract

The application is a method for designing myopia prevention and control contact lenses based on a modulation transfer function area distribution method, and belongs to the technical field of optical design. The application first confirms the setting of basic parameters of the contact lenses; then adds aspherical surface coefficients to optimize the imaging quality of each area; then brings in the modulation transfer function area distribution method to obtain the area of each ring; through confirming whether the imaging quality of each area is equal, if not, repeat the previous step; finally, the myopia prevention and control contact lenses based on the modulation transfer function area distribution method with equal imaging quality of each area are obtained. The area distribution method of the modulation transfer function is combined to divide the proportion of the defocus area and the correction area of the myopia prevention and control area, so as to balance the myopia prevention and control effect and the imaging quality. The defocus soft corneal contact lens changes the health state of the visual axis by designing different refractive correction degrees in different areas and focusing part of the light in front of the retina, so as to play a role in preventing and controlling myopia.

Description

Technical Field

[0001] This invention belongs to the field of optical design technology, and in particular to a method for designing myopia control contact lenses based on the modulation transfer function area allocation method. Background Technology

[0002] Due to improper eye use and increased screen time, the number of people with myopia has exploded, leading to the widespread use of soft contact lenses. With the growing demand for both imaging and vision prevention, research into designs that simultaneously meet imaging needs and myopia prevention goals is crucial. Defocused soft contact lenses, by designing different refractive correction powers in different areas, focus a portion of the light in front of the retina, thereby guiding the visual axis towards a healthy state and thus playing a role in myopia control.

[0003] Myopia control contact lenses are typically divided into a central correction zone and a myopia control zone. Different refractive powers are used in the myopia control zone to distribute a portion of light in front of the retina. Multi-ring designs are currently a common approach, often incorporating correction rings in the defocus zone to balance visual experience. Lenses like MISIGHT achieve a balance between myopia control and visual effect through the arrangement of defocus and correction zones. However, the optimal ratio between the defocus and correction zones has not been studied. Current designs typically estimate the proportion of each ring, failing to provide quantitative control over defocus effect and image quality. Therefore, we propose using a combined aberration allocation area method to distribute the ratio of the defocus and correction zones, achieving optimal myopia control and visual image quality.

[0004] To address the aforementioned issues, there is an urgent need to invent a method for designing myopia control contact lenses based on the modulation transfer function area allocation method. Summary of the Invention

[0005] The purpose of this invention is to provide a method for designing myopia control contact lenses based on the modulation transfer function area allocation method. This method solves the problem that the lack of scientific basis for the proportional division between the defocus zone and the correction zone of myopia control contact lenses leads to an imbalance between myopia control effect and optimal visual imaging quality. This design achieves the goal of optimal design by combining the area allocation method of the modulation transfer function, so as to balance the myopia control effect and imaging quality.

[0006] This invention discloses a method for designing myopia control contact lenses based on the modulation transfer function area allocation method, comprising the following steps:

[0007] SI: Confirm the settings of basic contact lens parameters;

[0008] S2: Add aspherical coefficients to optimize the imaging quality of each region;

[0009] S3: Substitute the modulated transfer function-based area allocation method to obtain the area of ​​each ring band;

[0010] S4: Confirm whether the imaging quality of each area is equal. If not, repeat the previous step.

[0011] S5: Obtain myopia control contact lenses based on the modulation transfer function area allocation method with equal imaging quality in each region.

[0012] In step SI, the refractive power of a myopic eye is higher than that of a normal eye. The required additional optical power value is:

[0013] Formula 1

[0014] in, The total optical power of the contact lenses designed for myopia is:

[0015] Formula 2

[0016] in, The refractive power of the anterior surface of the contact lens. t represents the refractive power of the posterior surface of the contact lens, t represents the thickness, and n represents the refractive index.

[0017] The initial structure of the myopic contact lens can be obtained by calculating using Equations 1 and 2.

[0018] Preferably, in step S2, the contact lens includes a central core correction zone, a first defocus zone, a first correction zone, a second defocus zone, ... an (n-1)th correction zone and an nth defocus zone. Both the defocus zone and the correction zone are ring structures. The first defocus zone, the correction zone and the second defocus zone are arranged alternately. The additional refractive power of the first defocus zone is less than that of the second defocus zone.

[0019] Preferably, in step S2, the substrate adopts an aspherical design, and the initial structural aspherical equation is expressed as follows:

[0020] Formula 3

[0021] Where k is the conic coefficient, A1, A2, etc. are aspherical coefficients, a is the radial diameter, and x is the axial coordinate of the contact lens.

[0022] Preferably, the lens with added aspherical parameters is applied to the eye of a myopic person for optimization. The myopic eye adopts the Atchison myopic eye model to obtain the imaging quality of each region of the initial structure.

[0023] Preferably, in step S3, the actual MTF ratio of the defocused area to the correction area can be expressed as:

[0024] Formula 4

[0025] Where FFT is the Fourier transform operation, and PSF1 and PSF2 are the initial structure imaging point spread functions when passing through each region, then the Fourier transform of the point spread function can be used to obtain... , MTF of the initial structure for each region, It is the area of ​​the j-th annulus;

[0026] The ratio of the actual MTF of adjacent regions is proportional to the area of ​​each ring. The area of ​​the central core correction zone is determined based on the size of the human pupil. The MTF in Equation 3... 校正 It does not include the central core calibration area.

[0027] Preferably, in step S3, when the ratio of the actual imaging quality MTF of each annulus to 1 is used to obtain a balanced defocus and correction effect, the area of ​​each annulus is calculated according to Equation 4:

[0028] Formula 5

[0029] in , The MTF is obtained based on the optimized initial structure of the system in step S2.

[0030] In step S5, after confirming that the imaging quality of each region is equal through steps S3 and S4, the following steps are performed: By determining the radius of each ring, the final myopia control contact lens design is obtained.

[0031] Preferably, the radius of curvature of the contact lens is set to be greater than the radius of curvature of the cornea, and the edge of the contact lens maintains a certain distance from the cornea.

[0032] Preferably, the smoothness and wearing comfort of the non-optical area of ​​the contact lens are designed, and the curvature of the contact lens edge is optimized to ensure the balance of intraocular pressure after the contact lens is inserted into the eye.

[0033] Beneficial effects

[0034] This invention guides light to the front of the retina through a defocus zone, thereby guiding the elongated retina caused by myopia back towards a normal direction. Simultaneously, a correction zone guides light onto the retina, maintaining visual image quality. The defocus and correction zones within the myopia control area are divided using a combined modulation transfer function area allocation method to balance myopia control effectiveness and image quality.

[0035] The myopia control lens of this invention consists of a central core correction zone and a myopia control zone. The myopia control zone is composed of a defocus zone and a correction zone of equal area. The defocus zone guides light to the front of the retina, thereby guiding the elongated retina caused by myopia towards a healthy state, thus playing a role in myopia control. In this invention, light is guided through the correction zone and the defocus zone by an area allocation design based on the modulation transfer function, providing good myopia control while also providing good visual imaging quality. At the same time, this invention provides a quantitative evaluation method for the defocus effect and visual imaging effect of myopia control contact lenses. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0037] Figure 1 Flowchart for the design of myopia control contact lenses based on the modulation transfer function area allocation method

[0038] Figure 2 Schematic diagram of the optical structure partitions of the retina in a contact lens;

[0039] Figure 3 This is a line graph showing the initial structure imaging quality of the first defocused area in Example 1;

[0040] Figure 4 This is a line graph showing the initial structure imaging quality of the second defocused region in Example 1;

[0041] Figure 5 This is a line graph showing the initial structural imaging quality of the correction area in Example 1;

[0042] Figure 6 The above is a histogram of the modulation transfer function after optimization in Example 1.

[0043] Figure 7 This is a line graph showing the initial structure imaging quality of the first defocused area in Example 2;

[0044] Figure 8 This is a line graph showing the initial structure imaging quality of the second defocused region in Example 2;

[0045] Figure 9 This is a line graph showing the initial structural imaging quality of the correction area in Example 2;

[0046] Figure 10 The above is a histogram of the modulation transfer function after optimization in Example 2. Detailed Implementation

[0047] This invention discloses a method for designing myopia control contact lenses based on the modulation transfer function area allocation method. By combining the modulation transfer function with the area allocation method, the method divides the myopia control area into defocus and correction zones to balance myopia control effectiveness and image quality. The defocus soft contact lens, by designing different refractive correction powers in different areas, focuses a portion of the light in front of the retina, thereby guiding the visual axis towards a healthy state.

[0048] like Figure 1-6 As shown, a method for designing myopia control contact lenses based on the modulation transfer function area allocation method includes the following steps:

[0049] SI: Confirm the settings of basic contact lens parameters;

[0050] S2: Add aspherical coefficients to optimize the imaging quality of each region;

[0051] S3: Substitute the modulated transfer function-based area allocation method to obtain the area of ​​each ring band;

[0052] S4: Confirm whether the imaging quality of each area is equal. If not, repeat the previous step.

[0053] S5: Myopia control contact lenses based on modulation transfer function area allocation method after ensuring equal imaging quality in each region.

[0054] In some embodiments, the refractive power of a myopic eye is higher than that of a normal eye. When light passes through a nearsighted person's eye, it focuses in front of the retina, causing the light information received by the retina to become blurred. Therefore, adding nearsighted contact lenses to refocus the light on the retina requires an additional optical power of:

[0055] Formula 1

[0056] in, This refers to the degree of myopia.

[0057] Contact lenses achieve refractive power through two parts: the anterior surface and the posterior surface. The refractive power of each surface can be expressed as the ratio of the difference in refractive index between the anterior and posterior surfaces to the radius of curvature. Therefore, the overall refractive power of the contact lens can be expressed as:

[0058] Formula 2

[0059] in, The refractive power of the anterior surface of the contact lens. t represents the refractive power of the posterior surface of the contact lens, t represents the thickness, and n represents the refractive index.

[0060] Typically, the radius of curvature of the posterior surface base curve of contact lenses is designed to be between 8.4 and 8.6 mm. Therefore, according to Equation 1, when the refractive index of the contact lens material is determined, the anterior surface refractive power can be calculated from the myopia degree. To determine the MTF of the initial structure, in some embodiments, the substrate adopts an aspherical design. The aspherical equation can be expressed as:

[0061] Formula 3

[0062] Where k is the conic coefficient, A1, A2, etc. are aspheric coefficients, a is the radial diameter, and x is the axial coordinate of the contact lens. Lenses with added aspheric parameters are optimized by applying them to the eyes of myopic individuals. The Atchison myopic eye model is used, which, through joint optimization of anatomical and optical aspects, is widely used in research on the optical characteristics of myopic eyes. Specific parameters of the Atchison myopic eye model are shown in Table 1. In Table 1, numbers 3 to 5 represent the asymptotic refractive indices used to simulate the natural lens (refractive indices are asymptotic 1 and asymptotic 2, with specific values ​​satisfying the Atchison eye model values; the asymptotic 1 refractive index value is equal to 1.371 + 0.037r). 2 Where r represents different positions along the aperture direction, i.e., r ranges from 0 to the maximum aperture value, and the asymptotic refractive index value is equal to 1.416 - 0.037r. 2 )lens.

[0063] Table 1: Parameters of the Atchison Myopic Eye Model

[0064] Surface markings Radius of curvature (mm) Conic coefficient Thickness (mm) Refractive index 123456 7.77 + 0.022 * D 6.40 11.48 Infinity - 5.9 - 12 -0.18-0.60-0.940.96 0.553.151.442.1616.28-0.299*D 1.376 1.336 Asymptotic 1 Asymptotic 2 1.336

[0065] Where D represents the degree of myopia.

[0066] In some embodiments, the corneal curvature radius and visual axis length vary with different myopia degrees. Simulations using Zemax software are performed, with the center of the posterior surface of the contact lens positioned close to the cornea. Because the curvature radius of the posterior surface of the contact lens is set to be greater than the corneal curvature radius, the edge of the contact lens can maintain a certain distance from the cornea, which helps with tear exchange and the maintenance of intraocular pressure. This allows for the acquisition of the initial MTF structure.

[0067] In some embodiments, myopia control is achieved by designing defocus rings. To ensure both defocus effect and clear imaging effect, defocus rings and correction rings appear alternately. The defocus area is used to image light in front of the retina, thereby guiding the retina towards a healthy direction. The correction area images onto the retina to ensure clear imaging for the human eye. Each defocus area has a different added refractive power. Generally, the defocus area in the center has a lower added refractive power, while the defocus area at the edge has a higher added refractive power, gradually transitioning so that the human eye can gradually adapt to the defocus changes and achieve the purpose of comfortable imaging.

[0068] In some embodiments, when light is uniformly incident, the final imaging effect of each region can be evaluated by the modulation transfer function (MTF). When light uniformly illuminates each region, the actual MTF ratio of the defocused region to the corrected region can be expressed as:

[0069] Formula 4

[0070] Where PSF1 and PSF2 are the image point spread functions of the initial structure when passing through each region. It is the area of ​​the j-th ring. The Fourier transform of the point spread function is the existing modulation transfer function level. , This refers to the actual modulation transfer function level. When the point spread function of each region is determined based on the initial structure, that is, when the initial structure modulation transfer function obtained by the Fourier transform of the point spread function is confirmed, the final ratio of the MTF of adjacent regions (i.e. the comparison of imaging effects) is proportional to the area of ​​each ring.

[0071] According to the above formula, if we want to provide the same quality imaging effect, the ratio of image quality MTF should be 1, that is, to provide the same quality imaging performance for adjacent areas. This helps to balance defocus and correction effects, so we can obtain:

[0072] Formula 5

[0073] After confirming that the image quality of each region is equal, then... Determine the radius of each ring. Furthermore, if the visual quality of the correction area is relatively blurry after the user wears the device, that is... If the value is greater than 1, then the area ratio of the correction region can be increased accordingly, making... The result reverts to 1, thus enabling quantitative analysis through the above formula.

[0074] Example 1

[0075] This invention incorporates a human eye system with myopia lenses. Taking the design of -3D contact lenses as an example, considering the focal point of the out-of-focus area, the human eye model in Table 1 is converted into an eye model corresponding to the corresponding out-of-focus degree. The overall structure is as follows: Figure 1As shown in Figure 2, the refractive index is 1.43. The first defocus ring is set to defocus +2.5D, and the second defocus ring is set to defocus +3.5D. The lens consists of a central core correction zone - defocus zone 1 - correction zone - defocus zone 2 - correction zone. The radius of the central core correction zone ring is set to 1.7mm to ensure imaging in the central core correction zone. The overall radius of the contact lens is 4mm, which can accommodate full visual coverage at different pupil sizes. Next, operands are added in Zemax to add aspherical coefficients to the front surface of the contact lens to optimize image quality and control edge thickness. Finally, the optimized myopia lens substrate design is obtained. The initial structure imaging quality of the first and second defocus zones is as follows: Figure 3-5 As shown.

[0076] To achieve uniform image quality in all regions outside the central region, the area ratio of each region outside the central region is calculated using the method proposed above. The modulation transfer function limit for human eye imaging needs to be evaluated is approximately 80 lp / mm. Therefore, we solve for the optimal result at 80 lp / mm. At 80 lp / mm, the modulation transfer function obtained by Zemax software optimization is 0.58343, 0.65317, and 0.6662. We take the maximum value as the ideal modulation transfer function, i.e., the transfer function of the second defocus region. Therefore, according to the provided method, the area of ​​the correction zone should be [amount missing] of the area of ​​the second defocus region. The area of ​​the first defocus zone should be times the area of ​​the second defocus zone. If the value is multiplied by a factor of 1, the optimized modulation transfer function will have the same value of 0.6662 at 80 lp / mm. Through the design method, a balanced imaging effect is provided in various regions, such as... Figure 6 As shown.

[0077] The optimized parameters of the contact lenses are shown in Table 2, after converting the area to the radius.

[0078] Table 2: Specific parameters of the optimized 3D contact lenses.

[0079] area Area (mm) Radius of curvature (mm) Conic coefficient Aspheric coefficient A1 Aspheric coefficient A2 Center correction zone, first defocus zone, correction zone, second defocus zone 0-1.71.7-2.66812.6681-3.44293.4429-4 9.1649318.70139.1649318.5287 2.4846620.0663712.4846620.104675 -2.208E-42.6139E-5-2.208E-4-3.562E-5 -2.757E-53.9671E-6-2.757E-5-4.5419E-6

[0080] Example 2

[0081] This invention incorporates a human eye system with myopia lenses. Taking the design of a -5D contact lens as an example, considering the focal point of the out-of-focus area, the human eye model in Table 1 is converted into an eye model corresponding to the corresponding out-of-focus degree. The overall structure remains the same. Figure 1As shown in Figure 2, the refractive index is 1.43. High-prescription contact lenses typically require a higher defocus amount to achieve good control. The first defocus ring is set to +3.5D, and the second defocus ring is set to +5D. Using Zemax software optimization, at 80 lp / mm, the existing initial structure modulation transfer functions of the first defocus zone, second defocus zone, and correction zone obtained by Zemax software optimization are 0.41864, 0.61326, and 0.64733, respectively. Figure 7-9 As shown, taking the maximum value as the ideal modulation transfer function, i.e., the transfer function of the second defocus region, the area of ​​the correction region should be 1 / 3 of the area of ​​the second defocus region. The area of ​​the first defocus zone should be times the area of ​​the second defocus zone. If the value is multiplied by 1, the optimized modulation transfer function will also have the same value of 0.64733 at 80 lp / mm. Figure 10 As shown, a design method provides a balanced imaging effect in each region.

[0082] Based on the above, the area is converted into radius, and the optimized parameters of the contact lenses are shown in Table 3.

[0083] Table 3. Specific parameters of the optimized 5D contact lenses.

[0084] area Area (mm) Radius of curvature (mm) Conic coefficient Aspheric coefficient A1 Aspheric coefficient A2 Center correction zone, first defocus zone, correction zone, second defocus zone 0-1.71.7-2.59462.5946-3.51573.5157-4 9.5856258.891909.5856258.624300 -0.7707301.394906-0.770730-0.767218 4.7951E-4-1.688E-44.7951E-42.202875E-5 -4.755E-5-5.164E-6-4.755E-5-1.449813E-6

[0085] The design focuses on the smoothness and wearing comfort of the non-optical area, and optimizes the curvature of the contact lens edge to ensure the balance of intraocular pressure inside and outside the contact lens. Tears can be drained from the edge, achieving a highly comfortable defocused soft corneal contact lens design.

[0086] By transforming the surface shape between molds, specifically the surface shape equation transformation of the lens—plastic mold—metal mold for defocused soft contact lenses, the design scheme provided by this patent can utilize a single-point diamond lathe to process the metal mold, utilize an injection molding machine to process the plastic mold, and utilize ultraviolet light curing to process the finished contact lens. The design method is feasible and practical.

[0087] In summary, this invention divides the visible portion of a contact lens into a correction zone and a defocus zone. After ensuring equal imaging quality in each zone, a method for designing myopia control contact lenses based on modulation transfer function area allocation is presented. By combining the area allocation method of modulation transfer function to divide the proportion of the defocus zone and the correction zone in the myopia control area, the myopia control effect and imaging quality are balanced. The defocus soft contact lens, by designing different refractive correction powers in different zones, focuses a portion of the light in front of the retina, thereby guiding the visual axis towards a healthy state and thus playing a role in myopia control.

Claims

1. A method for designing myopia control contact lenses based on the modulation transfer function area allocation method, characterized in that, Includes the following steps: SI: Confirm the settings of basic contact lens parameters; S2: Add aspherical coefficients to optimize the imaging quality of each region; S3: Substitute the modulated transfer function-based area allocation method to obtain the area of ​​each ring band; S4: Confirm whether the imaging quality of each area is equal. If not, repeat the previous step. S5: Obtain myopia control contact lenses with equal imaging quality in each region based on the modulation transfer function area allocation method. Furthermore, in step SI, the refractive power of a myopic eye is higher than that of a normal eye. The required additional optical power value is: Formula 1 in, Given the myopia refractive error, the total optical power of the designed contact lens is: Formula 2 in, The refractive power of the anterior surface of the contact lens. t represents the refractive power of the posterior surface of the contact lens, t represents the thickness, and n represents the refractive index. The initial structure of the myopic contact lens was calculated.

2. The method for designing myopia control contact lenses based on the modulation transfer function area allocation method according to claim 1, characterized in that: In step S2, the contact lens includes a central core correction zone, a first defocus zone, a first correction zone, a second defocus zone, ... an (n-1)th correction zone and an nth defocus zone. Both the defocus zone and the correction zone are ring structures. The first defocus zone, the correction zone and the second defocus zone are arranged alternately. The additional refractive power of the first defocus zone is less than that of the second defocus zone.

3. The method for designing myopia control contact lenses based on the modulation transfer function area allocation method according to claim 2, characterized in that: In step S2, the substrate adopts an aspherical design, and the initial aspherical equation of the structure is expressed as follows: Formula 3 Where k is the conic coefficient, A1, A2, etc. are aspherical coefficients, a is the radial diameter, and x is the axial coordinate of the contact lens.

4. The method for designing myopia control contact lenses based on the modulation transfer function area allocation method according to claim 3, characterized in that: The lens with added aspherical parameters was optimized by being applied to the eye of a myopic person. The myopic eye was modeled using the Atchison myopic eye model to obtain the image quality of each region of the initial structure.

5. The method for designing myopia control contact lenses based on the modulation transfer function area allocation method according to claim 4, characterized in that: In step S3, the actual MTF ratio of the defocused area to the correction area can be expressed as: Formula 4 Where FFT is the Fourier transform operation, and PSF1 and PSF2 are the initial structure imaging point spread functions when passing through each region, then the Fourier transform of the point spread function can be used to obtain... , MTF of the initial structure for each region, It is the area of ​​the j-th annulus; The ratio of the actual MTF of adjacent regions is proportional to the area of ​​each ring. The area of ​​the central core correction zone is determined based on the size of the human pupil. The MTF in Equation 3... 校正 It does not include the central core calibration area.

6. The method for designing myopia control contact lenses based on the modulation transfer function area allocation method according to claim 5, characterized in that: In step S3, the ratio of the image quality MTF of different regions, calculated according to Equation 4, should be 1 to achieve a balanced defocus and correction effect. Formula 5 In step S5, after confirming that the imaging quality of each region is equal, by... Determine the radius of each ring.

7. The method for designing myopia control contact lenses based on the modulation transfer function area allocation method according to claim 6, characterized in that: The radius of curvature of the contact lens is set to be greater than the radius of curvature of the cornea, and the edge of the contact lens is kept at a certain distance from the cornea.

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