Multifocal hard corneal contact lens and design method thereof

Abstract

The present invention discloses a multifocal hard corneal contact lens and a design method thereof. The corneal contact lens comprises a lens body, wherein the lens body continuously forms M distance light zones and N near light zones which are alternately arranged from the center outward; when the human eye looks at far distance, it can see the distance light zone of the lens to meet the demand for far vision; when the human eye looks at near distance, it can see the near light zone of the lens; compared with the distance light zone, the near light zone has additional positive light, which can relieve ciliary muscle spasm, help relax the ciliary muscle, and delay or prevent myopia.

Description

Technical Field

[0001] The invention relates to the field of corneal contact lenses, and in particular to a multifocal hard corneal contact lens and a design method thereof. Background Art

[0002] The human eye's adjustment for looking far and near is mainly achieved by changing the lens's brightness through the contraction and relaxation of the ciliary muscle. When a normal person looks far away, the ciliary muscle is in a relaxed state, at which time the lens's refractive power is small and the eyes are not easily fatigued. When looking close, the ciliary muscle contracts, the closer the distance, the greater the amount of contraction, and the greater the refractive power of the lens, and the eyes are easily fatigued. If the eye is in this tense state of contraction for a long time, it will lead to muscle tension, paralysis or loss of accommodation function.

[0003] In common situations, when people lower their heads to read for a long time and then suddenly look into the distance, they will find that things in the distance are blurry. This is because the refractive system is still in a tense state and does not relax immediately. This will cause a temporary decrease in distance vision and cause excessive accommodation. If this continues for a long time, it will lead to an irreversible decrease in distance vision and form myopia.

[0004] The prior art lacks a corneal contact lens that can quickly switch between a near light path and a far light path. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a multifocal hard corneal contact lens and a design method thereof.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A multifocal hard corneal contact lens comprises a lens body, wherein the lens body continuously forms M distance light zones and N near light zones arranged alternately from the center outward; the distance light zones and the near light zones have different photometric powers PW, and the photometric power of the distance light zone is PW far , the luminosity of the near light zone is PW near , then PW near =PW far +PW of ; Among them, PW of It is the additional brightness for near use, and it satisfies: 0D<PW of ≤6D.

[0008] Furthermore, the near additional light intensity PW of Satisfy: 0D<PW of ≤4D.

[0009] Furthermore, 3≤M≤20, 3≤N≤20, and |MN|≤1.

[0010] A method for designing a multifocal hard corneal contact lens comprises the following steps:

[0011] Step 1: Obtain the curvature radius at each position of the anterior surface of the cornea from the corneal topography. The curvature radius of the concave surface of the far light area or near light area is r LB =r corner , where r corner It is the average value of the radius of curvature of the anterior surface of the cornea covered by the distance light zone or the near light zone;

[0012] Step 2: The convex curvature radius of the high beam area or the low beam area

[0013]

[0014] where n L is the refractive index of the lens, ct L is the center thickness of the lens; and according to the actual situation of the wearer of the corneal contact lens, the diameter FOZ of each far light zone is selected i Or the diameter of the near light zone NOZ i .

[0015] Specifically, in step 2, the luminosity PW of the far light area or the near light area is used to calculate the respective convex curvature radius r LF0 Before, it is necessary to correct the spherical aberration of PW, then the spherical aberration correction luminosity of the far light area or the near light area where δ sp is the primary spherical aberration corresponding to the far light area or the near light area, f is the focal length corresponding to the far light area or the near light area; the convex curvature radius of the far light area or the near light area

[0016]

[0017] Compared with the prior art, the beneficial technical effects of the present invention are:

[0018] 1. Provide a multifocal contact lens. When the human eye looks far, it can see the far light zone of the lens to meet the need of far vision. When the human eye looks near, it can see the near light zone of the lens. Compared with the far light zone, the near light zone has additional positive light, which can relieve ciliary muscle spasm, help relax the ciliary muscle, and delay or prevent myopia. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the corneal contact lens of the present invention;

[0020] Figure 2 It is a schematic diagram of the distribution of the far light area and the near light area of ​​the present invention;

[0021] Figure 3The optical path diagram of the light of the present invention entering the human eye through the far-field light zone;

[0022] Figure 4 This is a light path diagram of the light of the present invention entering the human eye through the near light zone. DETAILED DESCRIPTION

[0023] A preferred embodiment of the present invention is described in detail below with reference to the accompanying drawings.

[0024] like Figure 1 and 2 As shown, a multifocal hard corneal contact lens comprises a lens body, wherein the lens body continuously forms M distance light zones and N near light zones arranged alternately from the center outward; the distance light zones and the near light zones have different photometric powers PW, and the photometric power of the distance light zone is PW far , the luminosity of the near light zone is PW near , then PW near =PW far +PW of ; Among them, PW of It is the additional brightness for near use, and it satisfies: 0D<PW of ≤6D.

[0025] like Figure 3 and 4 As shown, when the human eye looks far away, it can use the far light zone of the lens to meet the needs of far vision. When the human eye looks close, it can use the near light zone of the lens. Compared with the far light zone, the near light zone has additional positive light, which can relieve ciliary muscle spasm, help relax the ciliary muscle, and delay or prevent myopia.

[0026] When the human eye looks at close objects, the lens is in a relaxed state. The light entering the eye through the near light zone falls on the retina and is processed normally by the optic nerve. At this time, the light entering the eye through the far light zone must fall behind the retina and cannot be processed by the optic nerve. Therefore, the light passing through the far light zone will not have a substantial impact on the imaging of the light passing through the near light zone; and vice versa.

[0027] The range of near additional light is 0D<PW of ≤6D, the preferred value range is: 0D<PW of ≤4D; within 6D is the current mainstream near-vision additional diopter. If it exceeds this value, the diopter of the near and far vision zones will change too quickly, making it difficult for the wearer to adapt in a short period of time. Rapid changes can easily lead to blind spots at the junction of the light zones. In addition, children are in the developmental stage, and excessive near-vision additional diopter may weaken the original accommodation ability of the lens. 4D is a safer value in clinical practice.

[0028] In this embodiment, refer to Figure 2From the front view of the corneal contact lens, except for the light zone located in the center, each distance light zone and near light zone is arc-shaped and spreads outward alternately.

[0029] When selecting the number M of high beam zones and the number N of low beam zones, 3≤M≤20, 3≤N≤20, and |MN|≤1 are required; wherein |MN|≤1 is to ensure the need for alternating setting of high beam zones and low beam zones.

[0030] The above value range is intended to take into account both imaging quality and process stability.

[0031] If M and N are less than 3, each light zone on the lens will occupy a large area, and "image jumps" will occur between adjacent light zones, that is, the image of the object will be lost, resulting in poor imaging quality.

[0032] M and N take values ​​in the range of 3 to 20, so that each light zone has a narrower width, and the distance light zones and the near light zones are arranged alternately, and each distance light zone has the same light intensity, and each near light zone has the same light intensity, so that the corneal contact lens essentially has only two focal points, and two light intensities are integrated on one lens. When switching the visual distance, even if a blind spot appears at the junction of the two ends of the near light zone, the adjacent distance light zone is compensated accordingly.

[0033] Generally, the diameter of the lens is about 5mm to 10mm. When M and N are greater than 20, there will be more than 40 light zones in total, and the width of each light zone is only 0.125mm to 0.25mm. The width of the light zone is too narrow, and it is difficult to ensure accurate light intensity for each light zone with existing technology.

[0034] A method for designing the multifocal hard corneal contact lens comprises the following steps:

[0035] Step 1: Obtain the curvature radius at each position of the anterior surface of the cornea from the corneal topography. The curvature radius of the concave surface of the far light area or near light area is r LB =r corner , where r corner It is the average value of the radius of curvature of the anterior surface of the cornea covered by the distance light zone or the near light zone.

[0036] The high beam area and the low beam area are collectively referred to as light areas.

[0037] The concave curvature radius of the optical zone depends on the curvature radius of the anterior corneal surface. The corneal measurement equipment can measure and give a corneal topography map, and the average curvature radius of the anterior corneal surface covered by each optical zone can be obtained from the corneal topography map.

[0038] Step 2: The convex curvature radius of the high beam area or the low beam area

[0039]

[0040] where n L is the refractive index of the lens, ct L is the center thickness of the lens; and according to the actual situation of the wearer of the corneal contact lens, the diameter FOZ of each far light zone is selected i Or the diameter of the near light zone NOZ i .

[0041] Lens refractive index n L , lens center thickness ct L is a known quantity.

[0042] FOZ i is the diameter of the end of the ith high beam zone, NOZ i is the diameter of the end of the ith near light zone, and the above diameters can be determined by the diameter of the cornea and the size of the pupil; the diameters of the ends of the far light zones are FOZ1, FOZ2, ... FOZ m The diameters of the ends of the near beam zones are NOZ1, NOZ2, ... NOZ n .

[0043] When calculating the convex curvature radius of the far vision zone, the concave curvature radius, the lens refractive index, the lens center thickness and the luminosity corresponding to the far vision zone are selected.

[0044] When calculating the convex curvature radius of the near light zone, the concave curvature radius, the lens refractive index, the lens center thickness and the luminosity corresponding to the near light zone are selected.

[0045] The convex surface of each light zone is composed of a plurality of arc surfaces with different curvatures but coaxially arranged spherical centers.

[0046] However, the above calculation method does not take into account the influence of spherical aberration in each optical zone; spherical aberration is caused by the different convergence capabilities of the central area and the edge area of ​​the electromagnetic lens for electromagnetic waves; far-axis electromagnetic waves are refracted much more strongly than near-axis electromagnetic waves when passing through the lens, so the electromagnetic waves scattered by the same object point do not intersect at one point after passing through the lens, but become a diffuse circular spot on the lens phase plane; in order to eliminate the influence of spherical aberration, a corrective design is required.

[0047] Specifically, in step 2, the luminosity PW of the far light area or the near light area is used to calculate the respective convex curvature radius r LF0 Before, it is necessary to correct the spherical aberration of PW, then the spherical aberration correction luminosity of the far light area or the near light area where δ spis the primary spherical aberration corresponding to the far light area or the near light area, f is the focal length corresponding to the far light area or the near light area; the convex curvature radius of the far light area or the near light area

[0048]

[0049] Primary Spherical Aberration Where h is the incident height, which is half of the diameter of the end of the corresponding light zone; ρ is the convex curvature of the original design of the corresponding light zone, and the curvature is the reciprocal of the curvature radius; f is the focal length of the corresponding light zone, and the focal length is the negative reciprocal of the original design luminosity.

[0050] According to the optical principle,

[0051]

[0052] Among them, PW sp f-δ SP The corresponding lens power, PW is the original design power.

[0053] Then the spherical aberration corrected luminosity PW1=PW+(PW-PW sp ). (2)

[0054] Combining (1) and (2), we can get:

[0055] When calculating the spherical aberration corrected luminosity of the far light zone, the original designed luminosity, primary spherical aberration and focal length corresponding to the far light zone are used for calculation.

[0056] When calculating the spherical aberration corrected photometry of the near light zone, the original designed photometry, primary spherical aberration and focal length corresponding to the near light zone are used for calculation.

[0057] The corneal contact lens has a rotationally symmetrical structure.

[0058] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0059] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for designing a multifocal hard corneal contact lens, characterized in that: The multifocal hard corneal contact lens comprises a lens body, wherein the lens body continuously forms M distance light zones and N near light zones arranged alternately from the center outward; the distance light zones and the near light zones have different photometric powers PW, and the photometric power of the distance light zone is PW far , the luminosity of the near light zone is PW near , then PW near =PW far +PW of ; Among them, PW of It is the additional brightness for near use, and it satisfies: 0D<PW of ≤6D; The design method includes the following steps: Step 1: Obtain the curvature radius at each position of the anterior surface of the cornea from the corneal topography. The curvature radius of the concave surface of the far light area or near light area is r LB =r corner , where r corner It is the average value of the radius of curvature of the anterior surface of the cornea covered by the distance light zone or the near light zone; Step 2: The convex curvature radius of the high beam area or the low beam area where n L is the refractive index of the lens, ct L is the center thickness of the lens; and according to the actual situation of the wearer of the corneal contact lens, the diameter FOZ of each far light zone is selected i Or the diameter of the near light zone NOZ i ; In step 2, the luminosity PW of the far light area or the near light area is used to calculate the respective convex curvature radius r LF0 Before, it is necessary to perform spherical aberration correction on PW, then the spherical aberration correction luminosity of the far light area or the near light area where δ sp is the primary spherical aberration corresponding to the far light area or the near light area, f is the focal length corresponding to the far light area or the near light area; the convex curvature radius of the far light area or the near light area 2. The method for designing a multifocal hard corneal contact lens according to claim 1, characterized in that: The near light addition PW of Satisfy: 0D<PW of ≤4D.

3. The method for designing a multifocal hard corneal contact lens according to claim 1, characterized in that: 3≤M≤20, 3≤N≤20, and |MN|≤1.

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