JP2023110750A - Powerful short-sighted lens and method of designing powerful short-sighted lens - Google Patents

Abstract

To provide a novel powerful short-sighted lens capable of reducing deterioration in visual appearance in a wearing state.SOLUTION: A powerful short-sighted lens 1 of -4.5 diopter in average power as prescription power comprises: a first region 12 which is set at the center part of the lens and has short-sightness correction power based upon the prescription power and a second region 14 which is a region set outside the first region 12, and has more plus-side powder than the prescription power by adding a spherical surface component to at least one refractive surface of a pair of front rear refractive surfaces. The powerful short-sighted lens 1 is less in thickness in the second region 14 than a spherical lens 1B which has the same prescription power with the powerful short-sighted lens 1 and has the same base curve and the same lens center thickness, and increases in difference in thickness from the spherical lens 1B radially outward.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a lens for high myopia and a method for designing a lens for high myopia, and more particularly to a lens for high myopia and a method for designing a lens for high myopia that are effective in reducing appearance deterioration when worn.

One of the reasons why people with high myopia avoid using spectacle lenses for high myopia with a high power is the deterioration of the appearance when worn. Specifically, the deformation of the face line when viewed from another person, the total reflection around the lens, the thickness of the lens edge protruding from the frame, and the like. Such a problem becomes conspicuous as the power of the lens increases.

As a means to reduce the deterioration of the appearance due to the use of such lenses for high myopia, the use of eyeglass frames with small lens frames, the use of lenses with key points, and the reduction of the distance between vertices when worn. etc.
However, when spectacle frames with small lens frames are used, the types of frames that can be selected are limited. Lenses that have undergone keyhole processing have a strange appearance on the outside. If the distance between vertices is reduced, new problems arise, such as deterioration in wearing comfort and failure to obtain the prescribed dioptric power.

In addition, as described in the following patent document, there is a lens in which at least one of the two refractive surfaces is given an aspherical component to suppress the thickness of the lens peripheral portion. Since it is intended to reduce the thickness while ensuring the above, the effect of suppressing the deterioration of the appearance during wearing is small.

JP-A-8-5966

SUMMARY OF THE INVENTION It is an object of the present invention to solve such problems and to provide a novel lens for high myopia that can reduce the deterioration of the appearance when worn.

Thus, the lens for strong myopia of the present invention is a lens for strong myopia having an average prescription power of −4.5 diopters or less,
a first region set in the central portion of the lens and having a myopia correction power based on the prescribed power;
A second region set outside the first region, in which an aspherical component is added to at least one of the pair of front and rear refractive surfaces, and the power is on the positive side of the prescribed power. and,
with
When compared with a spherical lens having the same prescription power as the lens for strong myopia, the same base curve, and the same lens center thickness, the thickness in the second region is thinner than the spherical lens and the difference in thickness from the spherical lens. increases radially outward.

The present invention relates to a strong myopia lens having an average prescription power of -4.5 diopters or less. Here, the average power as the prescription power can be obtained by S power+(C power/2) based on the spherical power (S power) and the cylindrical power (C power) as the prescription power.
The aforementioned problem of deterioration in appearance when such a lens for high myopia is worn is caused by a sharp increase in lens thickness in the peripheral portion of the lens due to a strong negative dioptric power. The lens for strong myopia of the present invention secures the optical characteristics based on the prescription power in the central portion (first region) of the lens, and adds an aspherical component to the peripheral portion (second region) of the lens to increase the power. By changing the prescription power to the positive side and suppressing the thickness of the lens peripheral portion, it is possible to reduce the deterioration of the appearance when worn.

Here, the first area includes an area with a size of 6.72 mm in the horizontal direction, 3.53 mm upward, and 5.33 mm downward from the optical center, and inside the virtual circle with a radius of 25 mm from the optical center. can be
The area defined here is 6.72 mm in the horizontal direction, 3.53 mm in the upper direction, and 5.33 mm in the lower direction from the optical center. . If the first area is set so as to include such an area, the object viewed from the front through the lens can be visually recognized clearly and instantly.
However, if the first area is set too large, the second area for thinning the lens periphery becomes relatively narrow. It is preferable to set it inside the circle. More preferably, it is inside a virtual circle with a radius of 10 mm.

Further, in the present invention, the thickness of the addition start point of the aspheric component is t₀, the thickness at any point radially outside the addition start point is t₁, the thickness t of the point corresponding to the arbitrary point on the spherical lens_S., the value of the thickness reduction coefficient Q calculated based on the following formula (1) can be set to 0.6 or less at any point in the second region.
t₁= t₀+ (t_S.-t₀) x Q … formula (1)

In the present invention, thickness reduction is prioritized over optical properties in the second region. For example, the average power at a point in the second region 5 mm away from the boundary between the first region and the second region in the radial direction is set to the positive side of 1.0 diopters or more than the average power at the optical center, and at the point Astigmatism can be made positive by 1.0 diopter or more from astigmatism at the optical center.

The method of designing a lens for strong myopia according to the present invention is a method for designing a lens for strong myopia in which the average prescription power is −4.5 diopters or less,
(a) A first region, which is set in the central portion of the lens and is provided with a myopia correction power based on the prescription power, and an aspherical component, which is a region outside the first region and serves to reduce the deterioration of the appearance. partitioning the lens into a second region to which is added;
(b) the thickness of the aspheric component addition start point is t₀, the target thickness at an arbitrary point radially outside the addition start point is t₂, the thickness t of the point corresponding to the arbitrary point in the spherical lens determined based on the prescription power_S., where the thickness reduction coefficient is Q, the target thickness t at an arbitrary point in the second region₂a step of calculating based on the following formula (2);
t₂= t₀+ (t_S.-t₀) x Q … formula (2)
(c) the target thickness t at an arbitrary point in the second region;₂and the corresponding thickness t of the spherical lens_S.obtaining an aspherical component corresponding to the difference between and adding the aspherical component to the coordinate values of the refracting surface determined based on the prescription power;
characterized by comprising
According to the method of designing a lens for high myopia defined in this way, it is possible to suitably design the above lens for high myopia that can reduce the deterioration of the appearance when worn.

(A) is a front view of a spherical lens for high myopia, and (B) is a cross-sectional view of the lens including the optical axis. 1A is a front view of a lens for strong myopia according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view of the lens including the optical axis; FIG. FIG. 3 is an explanatory diagram of a first region of the lens for high myopia in FIG. 2; It is the figure which expanded and showed the upper half part of the lens cross section of FIG.2(B). It is explanatory drawing about the design method of the lens for strong myopia of the embodiment. (A) is an average power contour map of the example lens, and (B) is an astigmatism contour map of the example lens. (A) is a front view of a state in which the spherical lens of the comparative example is worn, and (B) is a front view of a state in which the example lens is worn.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In the following description, front, back, left, right, and top and bottom for the wearer of spectacles using lenses are defined as front, back, left, right, and top and bottom of the lens, respectively.

First, a spherical lens for high myopia (reference example) will be described.
The lens 1B in FIG. 1 is a spherical lens for strong myopia with a spherical power of -4.5 diopters or less, the rear surface 2 is a concave surface defined by the following formula (3), and the front surface 3 is the following formula (4 ) is defined as a convex surface. Note that the longitudinal axis passing through the optical center O of the lens 1B (base point O ₁ on the rear surface 2 and base point O ₂ on the front surface 3) is the z-axis, and the rearward direction of the lens 1B is the positive direction of the z-axis. The z-axis coincides with the optical axis of lens 1B.

z=r ² /(R ₁ +(R ₁ ² -Kr ² ) ^1/2 ) Equation (3)
z=r ² /(R ₂ +(R ₂ ² -Kr ² ) ^1/2 ) Equation (4)

r in equations (3) and (4) is the distance from the z-axis. That is, when considering an orthogonal coordinate system with the reference point O ₁ on the rear surface 2 and the reference point O ₂ on the front surface 3 as the center, with the horizontal and vertical axes orthogonal to the z-axis being the x-axis and the y-axis, respectively, r= (x ² +y ² ) ^1/2 . R ₁ and R ₂ are the radii of curvature at the vertex of the surface, and the coefficient K is 1. The radii of curvature R ₁ and R ₂ are determined by prescription power (specifically, S power, C power, and astigmatism axis AX). Since the lens 1B is a lens for high myopia for myopia, R ₁ <R ₂ .
In such a lens 1B, the larger the absolute value of the spherical power (S power), the more the deformation of the face line when viewed by others, the total reflection around the lens, the thickness of the lens edge protruding from the frame, etc. The problem of exacerbation becomes apparent.

In the above explanation, the lens in which the front surface 3 and the rear surface 2 are both spherical is assumed to be a spherical lens. There is also In the following description, in addition to the case where both the front surface 3 and the rear surface 2 are spherical, a lens in which one surface is spherical and the other surface is toric is also called a spherical lens.

FIG. 2 shows a lens 1 according to one embodiment of the invention. Such a lens 1 is obtained by adding an aspherical component to the peripheral portion of the spherical lens 1B, excluding the lens center portion. While ensuring optical characteristics based on the prescription power in the lens center portion, the thickness in the lens peripheral portion is reduced. This greatly reduces the problem of deterioration of the appearance of lenses for high myopia.

As shown in FIG. 2A, the lens 1 has a first region 12 formed in the center of the lens and a second region 14 formed outside the first region 12 .

The first region 12 is a region having a myopia correcting power based on the prescription power, and the wearer can clearly see an object through the first region 12 . The refractive surface shape of the front surface 3 of the first region 12 is defined by the above formula (4), and the refractive surface shape of the rear surface 2 is defined by the above formula (3).

By the way, in general, in the human visual field, the central visual field area which is excellent in visual acuity and color discrimination and capable of receiving information with high precision is considered to be within 5 degrees, and this area is called the discriminative visual field. In addition, the area where information can be received instantaneously by eye movement alone is about 30 degrees horizontally (± 15 degrees left and right) and about 20 degrees vertically (8 degrees up and 12 degrees down), and this area is called the effective field of view. is
When the distance between vertices is 12 mm, the lens area corresponding to the effective field of view is 6.72 mm in the horizontal direction, 3.53 mm upward, and 5.33 mm downward from the optical center, as shown in FIG. In this example, the first area 12 is set so as to include the lens area corresponding to this effective field of view. However, if the first region 12 is excessively large, the second region 14 becomes relatively narrow. there is More desirably, it is inside a virtual circle with a radius of 10 mm.

The second area 14 is an area set outside the first area 12 . In this example, an aspherical component is added to the rear surface 2b of the lens belonging to the second region 14, and the power in the second region 14 is set to be on the plus side of the prescribed power.

In FIG. 2B, a two-dot chain line indicates the lens shape of a spherical lens 1B having the same prescription power as the lens for strong myopia 1, the same base curve, and the same lens center thickness. As shown in the figure, the thickness of the second region 14 of the lens 1 is thinner than the spherical lens 1B indicated by the chain double-dashed line, and the difference in thickness from the spherical lens 1B increases radially outward. there is

FIG. 4 is an enlarged view of the upper half of the cross section of the lens in FIG. 2(B).
In the figure, P is the distance from the optical center at the addition start point of the aspherical component (boundary between the first region 12 and the second region 14), _t0 is the thickness of the addition start point, and Let r be the distance from the optical center at an arbitrary point on the outside in the radial direction, t ₁ be the thickness at the arbitrary point, and t _s be the thickness of the spherical lens 1B at the point corresponding to the arbitrary point. In this lens 1, when the relationship among these thicknesses t ₁ , t ₀ , and t _s is expressed by the above formula (1), the value of the thickness reduction coefficient Q in formula (1) is 0.6 or less. The smaller the value of this thickness reduction coefficient Q, the thinner the thickness at the lens peripheral portion, which can enhance the effect of reducing the deterioration of the appearance when worn. A value of the thickness reduction factor Q is preferably 0.4 or less, more preferably 0.3 or less.

Next, a method of designing the lens 1 will be described.
First, the refractive surface of the front surface 3 (see formula (4)) and the refractive surface of the rear surface 2 (see formula (3)) of the spherical lens 1B based on the prescription power are determined. Since this determination method is well known, it will not be described in detail here.
Next, as shown in FIG. 2, a first area 12 having a circular shape with a radius P from the optical center O, a second area 14 located radially outside the first area 12 and extending to the end of the lens, sectioning the lens into. In this example, this specifies the shape of the first region 12 having a myopia-correcting power based on the prescription power.

Next, the target thickness t along the radial direction in the second region 14₂Perform the step of calculating Specifically, as shown in FIG. 5, the thickness of the addition start point of the aspherical component (the boundary between the first region 12 and the second region 14) is t₀, the target thickness at any point radially outside the addition start point is t₂, the thickness of the point corresponding to the arbitrary point in the spherical lens determined based on the prescription power is t_S., where the thickness reduction coefficient is Q, the target thickness t₂is calculated based on the following formula (2).
t₂= t₀+ (t_S.-t₀) x Q … formula (2)
The thickness reduction coefficient Q can be appropriately determined in the range of 0 to 1, and the smaller the value of the thickness reduction coefficient Q, the thinner the thickness at the end of the lens. For example, it is preferable to set the value of the thickness reduction coefficient Q to 0.4 or less.

Then, the aspheric component corresponding to the difference between the target thickness t ₂ at an arbitrary point in the second region 14 and the thickness t _S at the point corresponding to the arbitrary point of the spherical lens 1B determined based on the prescription power A step of obtaining δ and adding the aspheric component δ to the coordinate values of the refractive surface S ₀ of the rear surface 2 of the spherical lens 1B determined based on the prescription power is executed.
The aspheric component δ can be expressed, for example, using the following formula (5). The optimum aspherical coefficients B, C, D, and E for obtaining the target thickness t _S (or a thickness approximate thereto) on the refracting surface of the rear surface 2 can be obtained by ray-tracing simulation.
δ=B(r−P) ⁴ +C(r−P) ⁶ +D(r−P) ⁸ +E(r−P) ¹⁰ Equation (5)
Here, r is the distance from the z-axis, P is the distance from the z-axis to the addition start point of the aspherical component, and B, C, D, and E are constants (aspherical coefficients).

The shape of the second region 14 is specified by adding the aspheric component δ obtained in this manner to the coordinate values of the refractive surface S ₀ of the rear surface 2 of the spherical lens 1B determined based on the prescription power. It is possible to design a lens 1 for strong myopia that is highly effective in reducing appearance deterioration.

[Example]
Based on the following lens data, lenses for high myopia were produced, and the average power distribution, astigmatism distribution and appearance of the lenses were evaluated.
The lens data are as follows.
refractive index n 1.738
front curve K 0.69
Spherical power S -8.50D (diopter)
Astigmatic power C -2.00D
Astigmatic axis direction Ax 175°
Outer diameter Φ75mm
Center thickness CT 1.1mm
Radius P of the first region 6 mm
Design thickness reduction factor Q 0.4
Aspheric coefficient B C D E
Rear -1.98E-05 4.423E-08 -4.223E-11 1.449E-14
In the aspherical coefficients B, C, D, and E, the numbers on the right side of E and E represent powers with 10 as the base and the numbers on the right side of E as exponents.

FIG. 6(A) is an average power contour map for the lens of the example. It is represented by a contour map in width. In addition, what is indicated by the dotted line in the figure is a grid with a pitch of 5 mm. According to FIG. 6(A), in this example lens, the average power within the first region including the optical center O (within 6 mm from the optical center O) is in the range of -10.0D to -9.0D. there is Then, the average power changes positively as it goes radially outward, and the point r1 (optical center O to 11 mm) ranged from -8.0D to -7.0D. That is, the average power at a point 5 mm away from the boundary between the first region 12 and the second region 14 in the radial direction changes from the average power at the optical center O to the positive side by 1.0 diopter or more.

FIG. 6(B) is an astigmatism contour diagram for the lens of the example. It is represented by a contour map with a step width. In addition, what is indicated by the dotted line in the figure is a grid with a pitch of 5 mm. According to FIG. 6B, in this example lens, the astigmatism within the first region including the optical center O is in the range of 1.1D to 2.1D. The astigmatism at a point r1 (11 mm from the optical center O), which is 5 mm further radially outward from the boundary between the first region and the second region, varies in the circumferential direction, but is approximately 4.1D to 5.1D. Range. That is, the astigmatism at a point 5 mm away from the boundary between the first region 12 and the second region 14 in the radial direction is changed to the positive side by 1.0 diopter or more from the astigmatism at the optical center O. there is
As described above, the lens of the embodiment secures the optical characteristics based on the prescription power in the central portion (first region 12) of the lens, while allowing deterioration of the optical characteristics in the peripheral portion (second region 14) of the lens. This is because suppression of the thickness is given priority over optical characteristics in the peripheral portion of the lens.

Table 1 below is a table showing the thickness along the radial direction of the lens of the example together with the thickness of a spherical lens (spherical lens having the same prescription power, the same base curve, and the same lens center thickness) as a comparative example. According to Table 1, it can be seen that the Example lens has a smaller peripheral thickness than the spherical lens as the comparative example, and the difference in thickness from the spherical lens increases radially outward. .

Next, FIG. 7A is a front view of a state in which the spherical lens of the comparative example is worn, and FIG. 7B is a front view of a state in which the example lens is worn. In addition, in FIGS. 7A and 7B, the lens is fitted in the frame only on the left eye side.
In both FIGS. 7A and 7B, deformation of the face line is recognized on the left eye side. However, in the example lenses in which the increase in thickness at the lens peripheral portion was greatly reduced as shown in Table 1 above, spherical lenses having the same prescription power, the same base curve, and the same lens center thickness (see FIG. 7A) ), as shown in FIG. 7B, the deformation of the face line seen from the other person is significantly improved. This is because the prism effect that causes deformation of the face line is well suppressed in the example lens.

As described above, the lens for strong myopia of the present embodiment secures the optical characteristics based on the prescription power in the central portion (first region 12) of the lens, while adding an aspherical component to the peripheral portion (second region 14) of the lens. By doing so, the average power is changed to the positive side from the prescription power, and the thickness of the lens peripheral part is suppressed, and according to the lens for strong myopia of this embodiment, the deterioration of the appearance during wearing can be reduced. can be done.

Although the embodiment of the present invention has been described in detail above, this is merely an example.
For example, in the above embodiment, an aspherical component that suppresses an increase in lens thickness at the lens periphery is added to the refractive surface on the rear side of the lens. It is also possible to add to both sides.
In the above-described embodiment, the aspherical surface components are specified using the aspherical surface coefficients of the 4th, 6th, 8th, and 10th orders. can also be used to define the aspheric component.
Further, although the first region is defined as circular in the above embodiment, it is also possible to define the first region as non-circular.
Further, in the above embodiment, the second region is provided all around in the circumferential direction. It can be implemented in a form with various changes added within a range that does not deviate from.

1 lens (lens for high myopia)
1B spherical lens 2 rear surface 3 front surface 12 first region 14 second region δ aspheric component

Claims (5)

A high myopia lens having an average prescription power of −4.5 diopters or less,
a first region set in the central portion of the lens and having a myopia correction power based on the prescribed power;
A second region set outside the first region, in which an aspherical component is added to at least one of the pair of front and rear refractive surfaces, and the power is on the positive side of the prescribed power. and,
with
When compared with a spherical lens having the same prescription power as the lens for strong myopia, the same base curve, and the same lens center thickness, the thickness in the second region is thinner than the spherical lens and the difference in thickness from the spherical lens. A lens for strong myopia, characterized in that the angle increases radially outward. The first region includes regions each having a size of 6.72 mm in the horizontal direction, 3.53 mm upward, and 5.33 mm downward from the optical center, and the outer edge of the first region has a radius of 25 mm from the optical center. 2. The lens for high myopia according to claim 1, which is inside the virtual circle. Let t be the thickness of the addition start point of the aspherical component₀, the thickness at any point radially outside the addition start point is t₁, the thickness of the point corresponding to the arbitrary point on the spherical lens is t_S., the value of the thickness reduction coefficient Q calculated based on the following formula (1) at an arbitrary point in the second region is 0.6 or less, A lens for high myopia according to any one of the above.
t₁= t₀+ (t_S.-t₀) x Q … formula (1) The average power at a point 5 mm away from the boundary between the first region and the second region in the radial direction is changed to the positive side by 1.0 diopter or more from the average power at the optical center, and the point is non- 4. The lens for high myopia according to claim 1, wherein the astigmatism at the optical center is shifted to the plus side by 1.0 diopter or more from the astigmatism at the optical center. A method for designing a strong myopia lens having an average prescription power of −4.5 diopters or less,
(a) A first region, which is set in the central portion of the lens and is provided with a myopia correction power based on the prescription power, and an aspherical component, which is a region outside the first region and serves to reduce the deterioration of the appearance. partitioning the lens into a second region to which is added;
(b) the thickness of the aspheric component addition start point is t₀, the target thickness at an arbitrary point radially outside the addition start point is t₂, the thickness of the point corresponding to the arbitrary point in the spherical lens determined based on the prescription power is t_S., where the thickness reduction coefficient is Q, the target thickness t at an arbitrary point in the second region₂a step of calculating based on the following formula (2);
t₂= t₀+ (t_S.-t₀) x Q … formula (2)
(c) the target thickness t at an arbitrary point in the second region;₂and the corresponding thickness t of the spherical lens_S.obtaining an aspherical component corresponding to the difference between and adding the aspherical component to the coordinate values of the refractive surface determined based on the prescription power;
A method of designing a lens for high myopia, comprising:

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