eyeglass lenses

Abstract

To provide a spectacle lens that can assist both accommodation and convergence in near vision and reduce fatigue and stress of a wearer. [Solution] The eyeglass lens 1 is formed with a distance portion 10 located at the top of the lens for distance vision and a near portion 11 located at the bottom of the lens for near vision. The near portion 11 is provided with a depth of field extension component δ1 whose power changes to the positive side as it moves outward in the direction perpendicular to the optical axis of the lens, and a constant prismatic refractive power with a base direction on the nose side is provided to the entire surface of the lens.

Description

[Technical Field]

[0001] The present invention relates to a spectacle lens having a distance portion located at the top of the lens and corresponding to far vision, and a near portion located at the bottom of the lens and corresponding to near vision. [Background technology]

[0002] Conventionally, progressive power lenses, bifocal lenses, etc. have been known as spectacle lenses intended to compensate for the decrease in the eye's ability to accommodate due to aging or fatigue. For example, a progressive power lens as shown in Patent Document 1 below has a distance portion for far vision, a near portion for near vision, and a progressive portion for intermediate vision provided between the distance portion and the near portion, and allows for continuous clear vision from far distances to near distances. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-102346 Summary of the Invention [Problem to be solved by the invention]

[0004] When the line of sight is moved to the near portion for near vision, a movement called convergence occurs in which the eyeballs adduct toward the nose. This convergence movement is generally realized by accommodative convergence that occurs in conjunction with accommodation, but when accommodation in near vision is assisted by the add power added to the near portion, accommodative convergence does not function sufficiently, which is one of the causes of visual fatigue.

[0005] SUMMARY OF THE INVENTION In light of the above circumstances, an object of the present invention is to provide a spectacle lens that can assist both accommodation and convergence in near vision, thereby reducing fatigue and stress in the wearer. [Means for solving the problem]

[0006] A spectacle lens according to a first aspect of the present invention is a spectacle lens having a distance portion located in the upper part of the lens and corresponding to far vision, and a near portion located in the lower part of the lens and corresponding to near vision, A depth of field extension component is added to the near portion, the power of which changes to the positive side as it moves outward in the direction perpendicular to the optical axis of the lens, In addition, a certain amount of prismatic power is added to the entire surface of the lens in the base direction on the nose side.

[0007] According to the first aspect defined in this way, even for those whose eye accommodation ability has decreased due to aging or fatigue, accommodation during near vision is assisted by the depth of field component set in the near portion (positive addition power added to the near portion). In addition, the accommodative convergence that decreases due to the assistance of accommodation is assisted by the prism refractive power with a base direction on the nose side that is added to the entire surface of the lens. Thus, the spectacle lens defined in the first aspect assisted both accommodation and convergence during near vision, thereby reducing the wearer's fatigue and stress.

[0008] Here, when lenses with strong prismatic power are worn, there are cases where the wearer feels uncomfortable when viewing distant objects, or where the wearer's eyes are displaced from their natural eye position after wearing the lenses for a certain period of time, resulting in a problem of prism adaptation. In order to avoid these problems, it is preferable that the prismatic power is 1.0 prism diopter or less per eye (second aspect).

[0009] In addition, in this invention, a depth-of-field extending component whose power changes to the negative side toward the outer side in the direction perpendicular to the optical axis of the lens can be added to the distance portion (third aspect). In this way, the depth of field in distance vision is extended to the far side, making it easy to focus on objects that are farther away than the original focus point. [Brief explanation of the drawings]

[0010] [Figure 1]1A and 1B are diagrams showing a typical example of a spectacle lens according to an embodiment of the present invention, in which (A) is a rear view and (B) is a cross-sectional view of a distance portion and a near portion. [Figure 2] 2 is a cross-sectional view of the eyeglass lens of FIG. 1 in the left-right direction. [Figure 3] 4A to 4C are diagrams for explaining the effects of the eyeglass lens of the embodiment. [Figure 4] 10A and 10B are explanatory diagrams of a spectacle lens according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Next, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the front, back, left, right, and top and bottom of a wearer wearing eyeglasses using eyeglass lenses will be referred to as the front, back, left, right, and top and bottom of the lenses, respectively.

[0012] 1 is a diagram showing a spectacle lens 1 (hereinafter, sometimes simply referred to as lens 1) according to one embodiment of the present invention. This lens 1 has a shape before its outer shape is processed to fit the shape of a spectacle frame, and has a circular shape when viewed from the front. Lens 1 has a rear surface 2 that is a concave surface defined by formula (i) and a front surface 3 that is a convex surface defined by formula (ii). The z-axis is the axis in the front-to-back direction that passes through the optical center of lens 1 (base point O1 on rear surface 2, base point O2 on front surface 3), and the direction toward the rear of lens 1 is the positive direction of the z-axis. The z-axis coincides with the optical axis of lens 1.

[0013] z=r 2 / (R1+(R1 2 -Kr 2 ) 1 / 2 ) + δ1...Equation (i) z=r 2 / (R2+(R2 2 -Kr 2 ) 1 / 2 ) …Formula (ii)

[0014] In equations (i) and (ii), r is the distance from the z-axis. In other words, when considering an orthogonal coordinate system with the base point O1 at the rear surface 2 and the base point O2 at the front surface 3 as the center, and the axes in the left-right direction and the up-down direction perpendicular to the z-axis as the x-axis and y-axis, respectively, r=(x 2 +y 2 ) 1 / 2 R1 and R2 are the radii of curvature at the vertices of the surfaces, and K is 1. As shown in equation (i), the term δ1 is added to the z coordinate value of the refracting surface of the rear surface 2. This δ1 is 3 (where r is the distance from the z-axis, and A is a constant) is the depth of field extension component (aspheric component). Therefore, the front surface 3 of the lens 1 is spherical, and the rear surface 2 is aspherical. R1 and R2 are determined by the prescription power (for example, S power). If the lens 1 is a minus lens for correcting myopia, R1 <R2である。

[0015] As shown in FIG. 1(A), the lens 1 has a distance portion 10 located at the top of the lens and corresponding to far vision, a near portion 11 located at the bottom of the lens and corresponding to near vision, and intermediate portions 12A and 12B located between the distance portion 10 and the near portion 11.

[0016] The distance portion 10 is an area defined by boundary lines E1 and E2 passing through the base point O1, and a depth-of-field extension component δ1 with a positive constant A is added to the rear surface 2 corresponding to this distance portion 10. As shown in Fig. 1(B), the distance portion 10 is thicker by the depth-of-field extension component δ1 than the refractive surface of the lens rear surface 2 determined based on the prescribed power (a spherical surface with a radius of curvature R1 in this example; hereinafter, this is also referred to as the original spherical surface and is indicated by the symbol S). By adding a depth of field extension component δ1 with a positive constant A to the rear surface 2, the power of the distance portion 10 changes to the negative side as it moves outward in the direction perpendicular to the optical axis of the lens. For example, when calculating a lens with a refractive index of 1.60 and an S power of 0.0 diopter (hereinafter sometimes referred to as "D"), the constant A is 9.92 × 10 -6 In this case, when the eyeball is rotated 30 degrees, the power changes by approximately 0.4D to the negative side from the lens central vision (equivalent to the prescribed power).

[0017] By doing so, the depth of field in far vision is extended to the far side, making it easier to focus on objects that are farther away than the original focus. The effects of adding a depth of field extension component are described in, for example, JP 2016-206338 A. In this example, the value of constant A is set to 3.20 × 10 so that the power changes from the lens central vision to the minus side by approximately 0.1 to 0.75 D when the eyeball is rotated 30 degrees. -6 ~1.92×10 -5 It is desirable to set it in the range of

[0045] , because in this range, the effect of extending the depth of field in far vision can be adequately obtained and the occurrence of aberrations can be suppressed.

[0018] Next, the near zone 11 will be described. The near zone 11 is a linear region provided closer to the nose (left side in the drawing) than the central axis (Y axis) of the lens 1 in consideration of convergence, and extends diagonally downward through the base point O1 and the near reference point K0 toward the edge of the lens. The near reference point K0 is a point for measuring the add power added to the near zone 11, and in this example, it is located 12 mm below and 2.5 mm to the left (nasal side) of the base point O1. A depth of field extension component δ1, where the constant A has a negative value, is added to the rear surface 2 corresponding to this near zone 11. The thickness of the near zone 11 is thinner than the original spherical surface S by the depth of field extension component δ1, as shown in FIG. 1(B). By adding a depth of field extension component δ1 with a negative constant A to the rear surface 2, the power in the near zone 11 changes to the positive side as it moves outward in the direction perpendicular to the optical axis of the lens. For example, when calculating a lens with a refractive index of 1.60 and an S power of 0.0D, the constant A is -2.18×10 -5 In this case, when the eyeball is rotated to the near reference point K0, the power changes by about 0.75D to the positive side from the lens central vision (corresponding to the prescribed power).

[0019] In this way, in this embodiment, the wearer's accommodation power during near vision can be assisted by the positive addition power set in the near portion 11. However, in consideration of the fact that a large addition power leads to a large decrease in accommodative convergence that occurs with accommodation, the value of the constant A is set to -7.68 x 10 so that the addition power at the near reference point K0 is in the range of approximately 0.25 to 1.25D. -6 ~-3.84×10 -5 It is desirable to set it within the range.

[0020] The intermediate portions 12A and 12B are regions whose power is changed so that the power at the boundary with the distance portion 10 is the same as that of the distance portion 10, and so that the power at the boundary with the near portion 11 is the same as that of the near portion 11.

[0021] In this embodiment, a certain prismatic power with a base direction on the nose side is applied to the entire surface of the lens 1. In the lens 1, the entire rear surface 2 is rotated around the Y axis so that a predetermined prismatic power is obtained at the optical center, and the lens is formed so that the nose side (left side in FIG. 2) is thicker and the ear side (right side in FIG. 2) is thinner.

[0022] According to the lens 1 of this embodiment, when an object 20 is viewed through the near portion 11 to which a predetermined add power is added, accommodation is assisted by the add power, while the convergence (accommodative convergence) that occurs with accommodation is reduced. The degree of reduced accommodative convergence can be expressed as accommodative assist power × (AC / A ratio). Here, the AC / A ratio (ratio of accommodative convergence to accommodation) indicates accommodative convergence per unit of accommodation, and the average for Japanese people is 2.0 per eye. For example, when 0.5D of accommodation assistance is provided, the reduced accommodative convergence is 0.5 × 2.0 = 1.0Δ. To compensate for this reduced accommodative convergence, the lens 1 of this embodiment is provided with the above-mentioned prismatic refractive power.

[0023] In this embodiment, since prismatic power with a base direction on the nasal side is applied to the entire lens surface, the line of sight during near vision is bent inward by accommodative convergence and the prismatic power that assists this, as shown in Figure 3. This allows the wearer to move their line of sight toward a near object 20 without forcibly adducting both eyes 21L and 21R inward.

[0024] The above effect (the effect of assisting accommodative convergence) can be obtained even if prismatic refractive power is added only to the lower part of the lens 1 where the near vision portion 11 is formed. However, if prismatic refractive power is added only to the lower part of the lens 1, aberration will occur between the upper part of the lens 1 to which no prismatic refractive power is added. Therefore, in this embodiment, a constant prismatic refractive power is added to the entire surface of the lens 1.

[0025] The prismatic refractive power added to lens 1 is 1.0 prismatic diopter or less. Here, the prismatic refractive power is defined as 1 prismatic diopter (hereinafter sometimes referred to as "△") when a ray of light deviates by 1 cm on a plane perpendicular to its initial direction over a distance of 1 m. Problems that arise when adding a certain prism power with a base direction on the nose side to the lens 1 include (1) discomfort during distance vision, and (2) the wearer's eyes adapt to the condition after wearing the lens for a certain period of time, resulting in a phenomenon (prism adaptation) in which the eyes deviate from their natural eye position when the lens is removed. In this embodiment, the upper limit of the prism power to be added to the lens is specified at a level that does not cause these problems.

[0026] [Example 1] Subjects in the prime-age to early presbyopic stage (37.3±4.1 years old) were given a near-vision lens with a full correction and an add power of +2.5D (no prism lens) and a near-vision lens with an additional 2.5Δ prism power (prism-added lens). They wore each lens (distance PD -8mm) and played a handheld game for 30 minutes at a viewing distance of 200mm. The difference in fusional duration (BFM) between before (Pre) and after (Post) visual load was measured to evaluate eye fatigue with each lens. The results are shown in Table 1 below. Fusional persistence (BFM) was measured using an ophthalmic device (binocular wavefront sensor). A visual target was viewed with both eyes, and the field of view of one of the test eyes (non-dominant eye) was gradually darkened (the transmittance of the non-dominant eye was reduced from 23% to 0.07%). The timing at which fusion was destroyed, the line of sight of the test eye shifted, and eye misalignment (gaze deviation) occurred was determined, and calculated using the following formula. BFM = 1 - (transmittance of the non-dominant eye at the time of fusional destruction / transmittance of the dominant eye)

[0027] [Table 1]

[0028] As shown in Table 1, the difference in fusional sustain ability before and after visual stress was -0.078±0.077 for lenses without prism and -0.022±0.038 for lenses with prism, meaning that there was less decline in fusional sustain ability with lenses with prism added (i.e., less eye fatigue). These results show that when Japanese people, the majority of whom have near exophoria, use lenses with a specified add power for near vision, using lenses that have prism power to assist convergence in addition to the add power can reduce eye fatigue in the wearer.

[0029] [Example 2] The test lenses, which had an add power of +0.5D added under full correction and a prism refractive power of 0.5△ added to the entire lens, were worn for 15 minutes to check whether or not any discomfort occurred when looking at something far away, and the amount of exophoria of the subjects before and after wearing the lenses was measured with the lenses on and with the lenses removed. The results are shown in Table 2 below.

[0030] [Table 2]

[0031] As shown in Table 2, no subjects experienced a significant increase in exophoria due to wearing the test lenses, and no problems with prism adaptation arose. Furthermore, no subjects complained of discomfort when viewing distances.

[0032] As described above, with the spectacle lens 1 of this embodiment, even for those whose eye accommodation ability has decreased due to aging or fatigue, accommodation during near vision is assisted by the depth of field component δ1 (positive addition power added to the near vision portion) set in the near vision portion 11. Furthermore, accommodative convergence that has decreased due to the assistance of accommodation is assisted by the prismatic refractive power added to the entire surface of the lens. In this way, with the spectacle lens 1 of this embodiment, both accommodation and convergence during near vision are assisted, thereby reducing the fatigue and stress of the wearer.

[0033] Furthermore, in the spectacle lens 1 of this embodiment, the prism refractive power added to the lens is set to 1.0 prism diopter or less, which makes it possible to avoid discomfort when viewing at a distance and problems with prism adaptation.

[0034] Furthermore, in the eyeglass lens 1 of this embodiment, a depth of field extension component δ1 is added to the distance portion 10, whose power changes to the negative side as it moves outward in the direction perpendicular to the optical axis of the lens. This means that the depth of field in distance vision is extended to the far side, making it easy to focus on objects that are farther away than the original focus point.

[0035] FIG. 4 is an explanatory diagram of a spectacle lens 1B according to another embodiment of the present invention. The lens 1B of this example differs from the above-described eyeglass lens 1 in that a power stabilization component δ0 is added to the original spherical surface S of the lens rear surface 2 (a spherical surface with a radius of curvature R1 in this example) determined based on the prescribed power, in addition to a depth-of-field extension component δ1.

[0036] In the spectacle lens 1B, the concave shape of the rear surface 2 is defined by the following formula (iv). z=r 2 / (R1+(R1 2 -Kr 2 ) 1 / 2 ) + δ0 + δ1 ... formula (iv) In the formula (iv) defining the rear surface 2, δ0 is Br 4 +Cr 6 +Dr 8 +Er 10 (where r is the distance from the z-axis, and B, C, D, and E are constants), and is added for the purpose of temporarily correcting the power distribution within the lens surface to a substantially constant value. Note that δ1 in formula (iv) is the same as in the case of the above-mentioned eyeglass lens 1, and is expressed by Ar 3 The depth of field extension component is expressed as:

[0037] The power stabilizing component δ0 can be calculated as follows: For the refractive surface shape of the rear surface 2 expressed using the aspherical formula (v) below, a simulation is performed by ray tracing to determine the aspherical coefficients B, C, D, and E that are optimal for suppressing changes in power (more specifically, the average power, which is the average of the refractive power in the meridional direction and the refractive power in the sagittal direction), and the power stabilizing component δ0 can be obtained from the values ​​of these aspherical coefficients. z=r 2 / (R1+(R1 2 -Kr 2 ) 1 / 2 )+Br 4 +Cr 6 +Dr 8 +Er 10 ...Formula (v) Here, z is the sag value at the rear surface 2, r is the distance from the z axis, R1 is the vertex curvature radius, and B, C, D, and E are constants (aspheric coefficients).

[0038] In the spectacle lens 1 of the above embodiment, a depth-of-field extending component δ1, which is an aspherical component, is added to a spherical surface S determined based on the prescribed power, but in cases where the absolute value of the prescribed power is large, a difference in power occurs between the center and periphery of the lens at the stage of the spherical lens consisting of the spherical surface S before the aspherical component is added. In such cases, part of the effect of the depth-of-field extending component is canceled out, and the desired depth-of-field extending effect may not be obtained.

[0039] In contrast, the spectacle lens 1B of this embodiment first has Br 4 +Cr 6 +Dr 8 +Er 10 By adding the power stabilization component δ0 expressed as 3 In this way, it is possible to effectively avoid the problem that the effect of the depth of field extension component is partially canceled out, making it impossible to obtain the desired depth of field extension effect.

[0040] Although the embodiments of the present invention have been described in detail above, this is merely an example. For example, in the above embodiment, each aspherical component is added to the refractive surface of the lens rear surface determined based on the S power, but the refractive surface of the lens rear surface determined based on the prescribed power can be determined based on the C power, the astigmatic axis AX, etc. in addition to the S power. In the above embodiment, aspherical coefficients for third-order terms are used as the depth-of-field extension component, and aspherical coefficients for fourth-order, sixth-order, eighth-order, and tenth-order terms are used as the power stabilization component, but in some cases it is also possible to use aspherical coefficients of orders different from these. Furthermore, the shape, position, range, etc. of the refractive surfaces that make up the distance and near portions can be changed as appropriate according to the target optical characteristics, etc. For example, the central region of the lens, which includes the optical center and parts of the distance and near portions, can be configured with a spherical surface that does not contain an aspherical component. In addition, in the above embodiment, an aspherical component is added to the rear surface of the lens, but it is also possible to add part or all of the aspherical component to the front surface of the lens. For example, the present invention can be implemented in various modified forms within the scope of its spirit. [Explanation of symbols]

[0041] 1,1B eyeglass lenses 10 Distance part 11 Near vision area O1,O2 base point δ1 depth of field extension component

Claims

1. A spectacle lens having a distance portion located at the top of the lens and corresponding to far vision, and a near portion located at the bottom of the lens and corresponding to near vision, A depth of field extension component is added to the near portion, the power of which changes to the positive side as it moves outward in the direction perpendicular to the optical axis of the lens, This is a spectacle lens in which a certain prismatic refractive power is added to the entire surface of the lens, with the base direction toward the nose.

2. 2. The spectacle lens of claim 1, wherein the prismatic power is equal to or less than 1.0 prismatic diopters.

3. 3. The eyeglass lens according to claim 1, wherein a depth-of-field extending component whose power changes to the negative side as it moves outward in the direction perpendicular to the optical axis of the lens is added to the distance portion.

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