Myopia prevention and control contact lens based on modulation transfer function area distribution method

Abstract

The invention relates to a myopia prevention and control contact lens based on a modulation transfer function area distribution method, and belongs to the technical field of optical design. Then adding an aspheric coefficient to optimize the imaging quality of each region; substituting into an area distribution method based on a modulation transfer function to obtain the area of each ring belt; determining whether the imaging quality of each area is equal or not, and if not, repeating the previous step; and finally, obtaining the myopia prevention and control contact lens based on the modulation transfer function area distribution method, wherein the imaging quality of each region is equal. According to the out-of-focus soft corneal contact lens, the proportion of an out-of-focus area and a correction area of a myopia prevention and control area is divided through an area distribution method of a combined modulation transfer function, so that the myopia prevention and control effect and the imaging quality are balanced, different refractive correction degrees are designed in different areas, a part of light is focused in front of the retina, and the myopia prevention and control effect is improved. Therefore, the visual axis is guided to change towards the health state, and the effect of preventing and controlling myopia is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical design, and in particular to a myopia prevention and control contact lens based on a modulation transfer function area allocation method. Background Art

[0002] Due to improper use of eyes in life and increased time spent on electronic screens, the number of people with myopia has exploded, so soft contact lenses are widely used. With people's growing demand for imaging and vision prevention, design research that can simultaneously meet imaging needs and myopia prevention purposes is crucial. Defocused soft contact lenses focus part of the light in front of the retina by designing different refractive correction degrees in different areas, thereby guiding the visual axis to change towards a healthy state, thereby playing a role in preventing and controlling myopia.

[0003] Myopia prevention and control contact lenses are usually divided into a central core correction area and a myopia prevention and control area. In the myopia prevention and control area, different refractive powers are designed to allocate part of the light to the front of the retina. Multi-ring design is a common design method at present. Usually, a correction ring needs to be added to the defocus area to balance the visual experience. MISIGHT et al. achieve a balance between myopia prevention and control and visual effects by arranging the defocus area and the correction area. However, the optimal ratio between the defocus area and the correction area has not been studied. The current design usually divides the ratio of each ring by estimation, and cannot achieve quantitative control of the defocus effect and imaging quality. Therefore, we propose to allocate the ratio of the defocus area and the correction area through the area allocation method of joint aberration allocation to achieve the optimal myopia prevention and control effect and the optimal visual imaging quality effect.

[0004] In order to solve the above problems, it is urgent to invent a myopia prevention and control contact lens based on the modulation transfer function area allocation method to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a design of a myopia prevention and control contact lens based on the modulation transfer function area allocation method, which solves the problem that there is no scientific basis for the proportional division between the defocus area and the correction area of ​​the myopia prevention and control contact lens, resulting in an imbalance between the myopia prevention and control effect and the optimized visual imaging quality. The present design achieves the purpose of optimal design by combining the division of the area allocation method of the modulation transfer function to balance the myopia prevention and control effect and the imaging quality.

[0006] The present invention discloses a myopia prevention and control contact lens based on a modulation transfer function area allocation method, comprising the following steps:

[0007] SI: confirm the setting of basic parameters of contact lenses;

[0008] S2: Add asphericity coefficients to optimize the imaging quality of each area;

[0009] S3: Substitute the area allocation method based on the modulation transfer function to obtain the area of ​​each ring zone;

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

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

[0012] Preferably, in step S1, the diopter of the myopic eye is higher than that of the normal eye. 近视 , the additional focal power value is:

[0013] φ=-φ 近视 Formula 1

[0014] Among them, φ 近视 The overall optical power of contact lenses designed for myopia is:

[0015]

[0016] Among them, φ 前 is the diopter of the front surface of the contact lens, φ 后 is the diopter of the back surface of the contact lens, t is the thickness, and n is the refractive index.

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

[0018] Preferably, in step S2, the contact lens includes a central core correction area, a first defocus area, a first correction area, a second defocus area...an n-1th correction area and an nth defocus area, the defocus area and the correction area are both annular structures, the first defocus area, the correction area and the second defocus area are arranged alternately, and the additional refractive power of the first defocus area is less than the additional refractive power of the second defocus area.

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

[0020]

[0021] Among them, k is the cone coefficient, A1, A2, etc. are aspheric coefficients, a is the radial diameter, and x is the axial coordinate of the contact lens.

[0022] Preferably, the lens with added aspheric parameters is brought into the myopic human eye for optimization, and the myopic human eye adopts the Atchison myopic human eye model to obtain the imaging quality of each area 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]

[0025] Among them, FFT is the Fourier transform operation, PSF1 and PSF2 are the initial structure imaging point spread functions when passing through each area, and then MTF1 and MTF2 can be obtained according to the Fourier transform of the point spread function to obtain the MTF of the initial structure of each area, S j is the area of ​​the jth ring;

[0026] The ratio of the actual MTF of adjacent areas is proportional to the area of ​​each ring zone. The area of ​​the central core correction area is determined according to the size of the human pupil. The MTF in formula 3 is 校正 The central core correction area is not included.

[0027] Preferably, in step S3, when the ratio of the actual imaging quality MTF of each annular zone is set to 1 to obtain a balanced defocus and correction effect, the area of ​​each annular zone is solved according to Formula 4:

[0028] MTF1(S j -S j-1 )=MTF2(S j-1 -S j-2 ) Formula 5

[0029] Among them, MTF1 and MTF2 are obtained according to the MTF after the initial structure optimization of the system in step S2.

[0030] In step S5, after confirming that the imaging quality of each area is equal through steps S3 and S4, Determine the radius of each ring zone to obtain the final myopia prevention and control contact lens design.

[0031] Preferably, the curvature radius of the contact lens is set to be larger than the curvature radius 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 edge of the contact lens is optimized to ensure that the internal and external intraocular pressures are balanced after the contact lens is inserted into the eye.

[0033] Beneficial Effects

[0034] The present invention can guide light to the front of the retina through the defocus area, thereby guiding the retina that is elongated due to myopia to develop in the normal direction, while the correction area guides light to the retina to maintain the visual imaging quality. The defocus area and correction area ratio of the myopia prevention and control area are divided by the area allocation method of the joint modulation transfer function to balance the myopia prevention and control effect and imaging quality.

[0035] The myopia prevention and control lens of the present invention is composed of a central core correction area and a myopia prevention and control area, wherein the myopia prevention and control area is composed of a defocus area and a correction area of ​​equal area, and the defocus area guides light to the front of the retina, thereby guiding the retina that has been elongated due to myopia to develop towards a healthy state, thereby playing a role in myopia prevention and control. In the present invention, light is guided through the correction area and the defocus area by an area allocation design based on a modulation transfer function, providing good myopia prevention and control effect while providing good visual imaging quality. At the same time, the invention provides a quantitative evaluation method between the defocus effect and the visual imaging effect of myopia prevention and control contact lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0037] Figure 1 Design flow chart for myopia prevention and control contact lenses based on modulation transfer function area allocation method

[0038] Figure 2 Schematic diagram of the optical structure of the retina part of the contact lens;

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

[0040] Figure 4 This is a line graph of the initial structural imaging quality of the second defocus area in Example 1;

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

[0042] Figure 6 The modulation transfer function histogram after optimization of Example 1;

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

[0044] Figure 8 This is a line graph of the initial structural imaging quality of the second defocus area in Example 2;

[0045] Fig. 9 This is a line graph of the imaging quality of the initial structure of the correction area in Example 2;

[0046] Fig.10 This is the modulation transfer function histogram after optimization of Example 2. DETAILED DESCRIPTION

[0047] The present invention discloses a myopia prevention and control contact lens based on the modulation transfer function area allocation method, which divides the defocus area and the correction area ratio of the myopia prevention and control area by combining the modulation transfer function area allocation method to balance the myopia prevention and control effect and the imaging quality. The defocus soft corneal contact lens focuses part of the light in front of the retina by designing different refractive correction degrees in different areas, thereby guiding the visual axis to change towards a healthy state.

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

[0049] SI: confirm the setting of basic parameters of contact lenses;

[0050] S2: Add asphericity coefficients to optimize the imaging quality of each area;

[0051] S3: Substitute the area allocation method based on the modulation transfer function to obtain the area of ​​each ring zone;

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

[0053] S5: Myopia prevention and control contact lenses based on the modulation transfer function area allocation method after the imaging quality of each area is equal.

[0054] In some embodiments, the refractive power of myopic eyes is higher than that of normal eyes. 近视 , light passes through the myopic eye and focuses in front of the retina, causing the light information received by the retina to be blurred. If a myopic contact lens is added to refocus the light on the retina, the additional focal length value required is:

[0055] φ=-φ 近视 Formula 1

[0056] Among them, φ 近视 It is the diopter degree of myopia.

[0057] Contact lenses perform refraction by two parts, namely the front surface and the back surface. The refractive power of each surface can be expressed as the ratio of the difference between the front and back refractive indices to the radius of curvature. The overall refractive power of the contact lens can be expressed as:

[0058]

[0059] Among them, φ 前 is the diopter of the front surface of the contact lens, φ 后 is the diopter of the back surface of the contact lens, t is the thickness, and n is the refractive index.

[0060] Usually, the base curve radius of the back surface of the contact lens is designed to be between 8.4 and 8.6 mm. According to Formula 1, when the refractive index of the contact lens material is determined, the front surface diopter can be inversely calculated according to the myopia degree. To determine the MTF of the initial structure, in some embodiments, the substrate adopts an aspherical design, and the aspherical equation can be expressed as:

[0061]

[0062] Among them, k is the cone coefficient, A1, A2, etc. are aspheric coefficients, a is the radial diameter, and x is the axial coordinate of the contact lens. The lens with added aspheric parameters is brought into the myopic human eye for optimization. The myopic human eye adopts the Atchison myopic human eye model. This model is widely used in the study of the optical properties of myopic human eyes through the joint optimization of anatomy and optics. The specific parameters of the Atchison myopic human eye model are shown in Table 1. In Table 1, numbers 3 to 5 represent the progressive refractive index selected to simulate the natural lens (the refractive index is progressive 1, progressive 2, and the specific values ​​meet the Atchison human eye model values. The progressive 1 refractive index value is equal to 1.371+0.037r 2 , r is the different positions in the aperture direction, that is, r is from 0 to the maximum aperture value, and the progressive 2 refractive index value is equal to 1.416-0.037r 2 )lens.

[0063] Table 1: Atchison myopic eye model parameters

[0064]

[0065] Where D is the degree of myopia.

[0066] In some embodiments, the corneal curvature radius and visual axis length will change with different myopia degrees, and the Zemax software is used to simulate it. The center of the back surface of the contact lens is set close to the cornea. Since the curvature radius of the back surface of the contact lens is set larger than the curvature radius of the cornea, the edge of the contact lens can maintain a certain distance from the cornea, which is helpful for the exchange of tears and the maintenance of intraocular pressure. Then the MTF of the initial structure can be obtained.

[0067] In some embodiments, myopia prevention and control is achieved by designing defocus rings. In order to ensure both the defocus effect and the clear imaging effect, the defocus rings and the correction rings appear alternately. The defocus area is used to image the light in front of the retina, thereby pulling the retina to develop in a healthy direction. The correction area is imaged on the retina to ensure clear imaging of the human eye. Each defocus area has a different additional refractive power. Normally, the defocus area in the center has a lower additional refractive power, and the defocus area at the edge has a higher additional refractive power. The gradual transition allows the eye to gradually adapt to the defocus changes and achieve the purpose of comfortable imaging.

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

[0069]

[0070] Where PSF1 and PSF2 are the imaging point spread functions of the initial structure when passing through each area, S j is the area of ​​the jth ring zone. The Fourier transform of the point spread function is the existing modulation transfer function level, MTF 离焦 ,MTF 校正 That is the actual modulation transfer function level. When the point spread function of each area is determined according to the initial structure, that is, when the initial structure modulation transfer function is confirmed by the Fourier transform of the point spread function, the final ratio of the MTF of adjacent areas (that is, the contrast of imaging effects) is proportional to the area of ​​each annulus.

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

[0072] MTF1(S j -S j-1 )=MTF2(S j-1 -S j-2 ) Formula 5

[0073] After confirming that the image quality of each area is equal, Determine the radius of each ring band. Further, if the visual quality of the correction area is relatively blurred after the application population wears it, that is, If is greater than 1, the area ratio of the correction area can be increased accordingly. It tends to 1 again, and quantitative analysis is achieved through the above formula.

[0074] Example 1

[0075] The human eye system in the present invention adds myopia lenses, taking the design of 3D contact lenses as an example, considering the imaging focus of the defocus area, the human eye model in Table 1 is converted into an eye model corresponding to the corresponding defocus degree, and the overall structure is as follows: Figure 1, as shown in 2, the refractive index is 1.43, the first defocus ring is set to defocus +2.5D, the second defocus ring is set to defocus +3.5D, the lens is composed of central core correction area-defocus area 1-correction area-defocus area 2-correction area, the radius of the central core correction area is set to 1.7mm to ensure the imaging of the central core correction area, the overall radius of the contact lens is 4mm, which can accommodate the full coverage of vision when the pupil size is different. Next, add operands in Zemax, add aspheric coefficients to the front surface of the contact lens to optimize the imaging quality, and control the edge thickness. Finally, the optimized myopia lens base design is obtained. The initial structural imaging quality of the first and second defocus areas is shown in Figure 3-5 shown.

[0076] In order to achieve uniform imaging quality in each area outside the central area, the area ratio of each area except the central area is calculated according to the method proposed above. The limit of the modulation transfer function that needs to be evaluated for human eye imaging is about 80lp / mm. Then we solve the optimal result at 80lp / mm. At 80lp / mm, the modulation transfer functions optimized by Zemax software are 0.58343, 0.65317, and 0.6662. We use the maximum value as the ideal modulation transfer function, that is, the transfer function of the second defocus area. According to the provided method, the area of ​​the correction area should be the area of ​​the second defocus area. times, the area of ​​the first defocus zone should be the area of ​​the second defocus zone times, the optimized modulation transfer function at 80lp / mm has the same value of 0.6662. Through the design method, a balanced imaging effect is provided in each area, such as Figure 6 shown.

[0077] After converting the area into radius, the specific parameters of the optimized contact lens are shown in Table 2.

[0078] Table 2:- Specific parameters of contact lenses after 3D contact lens optimization.

[0079]

[0080] Example 2

[0081] The human eye system in the present invention adds myopia lenses, taking the design of -5D contact lenses as an example, considering the imaging focus of the defocus area, at this time, the human eye model in Table 1 is converted into an eye model corresponding to the corresponding defocus degree, and the overall structure is also as follows Figure 1, as shown in Figure 2, the refractive index is 1.43. Contact lenses with high myopia usually need to be equipped with a higher defocus amount to achieve a good prevention and control effect. The first defocus ring is set to defocus +3.5D, and the second defocus ring is set to defocus +5D. Zemax software is used for optimization. At 80lp / mm, the initial structural modulation transfer functions of the first defocus area, the second defocus area, and the correction area obtained by Zemax software optimization are 0.41864, 0.61326, and 0.64733, as shown in Figure 2. Figure 7-9 As shown, taking the maximum value as the ideal modulation transfer function, that is, the transfer function of the second defocus zone, the area of ​​the correction zone should be 1 / 2 of the area of ​​the second defocus zone. times, the area of ​​the first defocus zone should be the area of ​​the second defocus zone times, the optimized modulation transfer function at 80lp / mm has the same value of 0.64733, such as Fig.10 As shown, a balanced imaging effect is provided in various areas through the design method.

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

[0083] Table 3.—Specific parameters of contact lenses after 5D contact lens optimization.

[0084]

[0085] From the design perspective, the non-optical area is designed for smoothness and wearing comfort, and the curvature of the contact lens edge is optimized to ensure the balance of intraocular pressure inside and outside the contact lens, so that tears can be discharged from the edge, achieving a highly comfortable defocused soft corneal contact lens design.

[0086] Through the surface shape transformation between molds, that is, the surface shape equation transformation of the lens of the defocused soft corneal contact lens - plastic mold - metal mold, the design scheme provided by this patent can realize the processing of metal molds by a single-point diamond lathe, the processing of plastic molds by an injection molding machine, and the processing of finished contact lenses by ultraviolet light curing. The design method is feasible and practical.

[0087] To summarize, the present invention divides the visible part of the contact lens into a correction area and a defocus area, and after controlling the imaging quality of each area to be equal, the myopia prevention and control contact lens based on the modulation transfer function area allocation method is used to divide the defocus area and the correction area ratio of the myopia prevention and control area by combining the area allocation method of the modulation transfer function to balance the myopia prevention and control effect and the imaging quality. The defocus soft corneal contact lens focuses part of the light in front of the retina by designing different refractive correction degrees in different areas, thereby guiding the visual axis to change towards a healthy state, thereby playing a role in preventing and controlling myopia.

Claims

1. A myopia prevention and control contact lens based on the modulation transfer function area allocation method, characterized in that: The following steps are involved: SI: confirm the setting of basic parameters of contact lenses; S2: Add asphericity coefficients to optimize the imaging quality of each area; S3: Substitute the area allocation method based on the modulation transfer function to obtain the area of ​​each ring zone; S4: confirm whether the imaging quality of each area is equal. If not, repeat the previous step; S5: Obtaining myopia prevention and control contact lenses with equal imaging quality in each area based on the modulation transfer function area allocation method.

2. The myopia prevention and control contact lens based on the modulation transfer function area allocation method according to claim 1, characterized in that: In step S1, the diopter of myopic eyes is higher than that of normal eyes. 近视 , the additional focal power value is: φ=-φ 近视 formula 1 Among them, φ 近视 is the myopia diopter, then the overall optical power value of the designed contact lens is: Among them, φ 前 is the diopter of the front surface of the contact lens, φ 后 is the diopter of the back surface of the contact lens, t is the thickness, and n is the refractive index. The initial structure of the myopic contact lens is calculated.

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

4. The myopia prevention and control contact lens based on the modulation transfer function area allocation method according to claim 3, characterized in that: In step S2, the substrate adopts an aspherical design, and the initial structural aspherical equation is calculated as: Among them, k is the cone coefficient, A1, A2, etc. are aspheric coefficients, a is the radial diameter, and x is the axial coordinate of the contact lens.

5. The myopia prevention and control contact lens based on the modulation transfer function area allocation method according to claim 4, characterized in that: The lens with added aspheric parameters is brought into the myopic human eye for optimization. The Atchison myopic human eye model is used to obtain the imaging quality of each area of ​​the initial structure.

6. The myopia prevention and control contact lens based on the modulation transfer function area allocation method according to claim 5, characterized in that: In step S3, the actual MTF ratio of the defocused area to the correction area can be expressed as: Among them, FFT is the Fourier transform operation, PSF1 and PSF2 are the initial structure imaging point spread functions when passing through each area, and then MTF1 and MTF2 can be obtained according to the Fourier transform of the point spread function to obtain the MTF of the initial structure of each area, S j is the area of ​​the jth ring; The ratio of the actual MTF of adjacent areas is proportional to the area of ​​each ring zone. The area of ​​the central core correction area is determined according to the size of the human pupil. The MTF in formula 3 is 校正 The central core correction area is not included.

7. The myopia prevention and control contact lens based on the modulation transfer function area allocation method according to claim 6, characterized in that: In step S3, the ratio of the MTF of the imaging quality in different regions is obtained according to formula 4, which should be 1 to obtain a balanced defocus and correction effect: MTF1(S j -S j-1 ) = MTF2(S j-1 -S j-2 ) Equation 5 In step S5, after confirming that the imaging quality of each area is equal, Determine the radius of each ring.

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

9. The myopia prevention and control contact lens based on the modulation transfer function area allocation method according to claim 8, characterized in that: The smoothness and wearing comfort of the non-optical area of ​​the contact lens are designed, and the curvature of the edge of the contact lens is optimized to ensure that the internal and external intraocular pressures are balanced after the contact lens is inserted into the eye.

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