JPH10123468A - Progressive multi-focus lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a user to comfortably continue near sight for a long time by separating the center of a near sight correcting area downward from a near sight eye point at a specific interval along a main meridian curve and specifying refractive power on the center or the like of a specific sight distance correcting area. SOLUTION: A near sigh part N having face refractive power corresponding to a near sight, a specific sight part F having face refractive power corresponding to a specific distance and an intermediate part P arranged between the near signt part N and the specific sight part F to continuously connect the face refractive power of both the areas are arranged along the main meridian curve MM'. A near sight eye point E is set up on a distance of 2 to 8mm upward from a near sight center B along the curve MM'. A conditional inequality 0.6<(KE-KA)/(KB-KA)<0.9 is satisfied in accordance with the setting of a distance range from the eye point E up to the center B. Provided that KE is refractive power on the near signal eye point E, KA is refractive power on a specific center and K6 is refractive point on the near sight center B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a progressive multifocal lens used for assisting the accommodation power of an eye.

[0002]

2. Description of the Related Art A single focus lens, a bifocal lens, a progressive multifocal lens, and the like are used for correcting presbyopia. Among these lenses, the progressive multifocal lens in particular does not require changing or removing the glasses for far vision and near vision. In addition, the progressive multifocal lens does not have a boundary in appearance, unlike a bifocal lens. Accordingly, the demand for progressive multifocal lenses has increased considerably.

[0003] A progressive multifocal lens is an auxiliary spectacle lens for accommodation power when the accommodation power of the eye is reduced and near vision becomes difficult. Generally, in a progressive multifocal lens, a far vision correction area (hereinafter, referred to as a "distant vision portion") located above when worn.
) And the lower near vision correction area (hereinafter, “near vision section”)
), And a progressive region (hereinafter, referred to as an “intermediate portion”) in which the refractive power changes continuously between both regions. In the present invention, "upper", "lower",
"Horizontal", "vertical" and the like indicate the positional relationship of the lens when worn. The difference between the near power and the far power is referred to as an additional power.

In general, in a progressive multifocal lens, a wide clear vision zone (a range in which the astigmatic difference is 0.5 diopter or less) is ensured widely in a distance portion and a near portion, and these portions are connected by a progressive zone (a progressive zone). Then, the lens aberration concentrates on the side region of the progressive zone. As a result, poor image formation (blurring of the image) and distortion of the image occur particularly in the lateral region of the progressive zone, and when the eyes are shaken (moved) in such a region, the distortion of the image appears to the wearer. It is perceived as shaking, and gives an unpleasant feeling of poor wearing.

[0005] In order to solve such a problem of visual characteristics, known progressive multifocal lenses have been designed and evaluated from various viewpoints. Regarding the shape of the lens surface, the intersection (principal meridian curve) of the section along the meridian that runs vertically from almost the center of the lens surface to the bottom and the object-side lens surface represents the specifications such as the addition of the lens. This is also used as an important reference line in lens design.

Also, in consideration of the fact that the near portion is slightly closer to the nose side from the center in the wearing state of the lens, a progressive multifocal lens in which the near portion is asymmetrically arranged (hereinafter referred to as an "asymmetric progressive multifocal lens"). ") Has been proposed. Also in such an asymmetric progressive multifocal lens, a center line formed by an intersection of a section passing through the distance center and the near center and the object side lens surface is used as a reference line. In the present invention,
These reference lines are collectively called "main meridian curve".

Under the above technical background, Japanese Patent Application Laid-Open
Attention has been paid to a progressive multifocal lens for both middle and near distances disclosed in Japanese Patent Publication No. -10617. This progressive multifocal lens is a progressive multifocal lens based on a design that emphasizes near vision to near vision. It is said that the spectacle lens has a relatively wide field of view up to a distance, and is relatively easy to use especially indoors.

[0008]

By the way, as the degree of deterioration of the accommodation power of the eyes increases, it becomes necessary to wear a lens having a large addition. In general, as the addition increases, the above-mentioned drawbacks of the progressive multifocal lens become more pronounced. That is, the clear viewing area in the distance portion and the near portion becomes narrower as the addition degree increases. As a result, it is not possible to perform comfortable side viewing by shaking the line of sight in the distance portion and the near portion, and it is necessary to shake the entire face to perform side viewing. Further, the lens aberration increases in the lateral region of the progressive zone connecting the distance portion and the near portion as the addition increases. As a result, when the eyes are shaken in the lateral region of the progressive zone, the swaying and distortion of the image are increased, and the wearing feeling is further deteriorated, so that wearing may be difficult.

Further, in the conventional progressive multifocal lens, the corridor is relatively long because it is set so that it can be seen from far to near regardless of the degree of deterioration of the accommodation power of the eyes. Therefore, in a state where the lens is framed in the spectacle frame, the near vision region is located at the bottom of the frame, and the line of sight must be greatly lowered for near vision. As a result, not only is it difficult to see, but also eye strain is caused by greatly lowering the line of sight. Therefore, with the conventional progressive multifocal lens, it has been difficult to continue near work such as desk work for a relatively long time.

Incidentally, in the conventional progressive multifocal lens of the conventional type disclosed in Japanese Patent Application Laid-Open No. 62-10617, since the progressive zone is relatively long, image shaking and distortion seen in a general progressive multifocal lens are known. Such disadvantages have been solved to some extent. However, as described above, since the corridor is long, the user's line of sight must be greatly lowered for near vision, which causes inconvenience as well as eye strain.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a progressive multifocal lens capable of comfortably continuing near vision for a long period of time even for a person who has a large decline in the accommodation power of the eyes. The purpose is to provide.

[0012]

In order to solve the above-mentioned problems, according to the present invention, a surface refraction corresponding to a foreground is taken along a principal meridian curve dividing a lens refraction surface into a nose side region and an ear side region. Near vision correction area having power, a specific viewing distance correction area having a surface refractive power corresponding to a specific distance substantially apart from the foreground, and the near vision correction area and the specific viewing distance correction area And a progressive region that continuously connects the surface refractive powers of both regions between the centers. The center of the near vision correction region is spaced apart from the near eye point by 2 mm to 8 mm along the main meridian curve from the near eye point. separated, the refractive power in the near eye point and K _E, the refractive power at the center of the specific viewing distance correction area and K _a, the refractive power at the center of the near vision correction region and a K _{B when, 0.6 <(K E -K A} ) / (K B -K A) < A progressive multifocal lens which satisfies the condition of 0.9 (1) is provided.

According to a preferred embodiment of the present invention, the maximum width of the clear vision area in the specific viewing distance corrective region W _F (mm)
And the maximum width of the clear vision area in the near vision correction area is W
When the _N (mm), the refractive power at the center of the specific viewing distance correction area and K _A (diopter), the refractive power at the center of the near vision correction region and the K _B (diopter), W _{F ≧ 50 / (K B -K a} ) (2) W N ≧ 50 / (K B -K a) (3) satisfies the conditions of.

[0014]

FIG. 3 is a diagram schematically showing a refractive power distribution on a principal meridian curve of a conventional progressive multifocal lens focusing on distance. First, with reference to FIG. 3, a description will be given of the drawbacks of a conventional progressive multifocal lens that emphasizes perspective. As shown in FIG. 3, in the conventional progressive multifocal lens focusing on distance, the distance along the main meridian curve from the distance eye point E, which is a wearing reference as a spectacle lens, to the lower part A of the distance portion F is small. . That is, in the conventional progressive multifocal lens design method focusing on distance, the amount of increase in refractive power at the distance eye point E with respect to the lower portion A of the distance portion F is about 5% of the addition.
For this reason, the generated aberration is relatively small, good visual characteristics can be obtained, and it is possible to widen the clear vision area of the distance portion F to some extent. Note that the distance eye point is a passing point on the lens of the line of sight when the spectacle wearer is looking at a distance in a natural posture, and is sometimes referred to as a distance fitting point.

In the conventional progressive multifocal lens emphasizing distance, the refractive power on the principal meridian curve is increased by about 95% of the addition from the distance eye point E to the upper part B of the near part N. . For this reason, the clear vision zone of the near portion N is
Much smaller than the clear visual field of Therefore, FIG.
The progressive multifocal lens with the refractive power distribution shown in the above can withstand practical use as a lens focusing on distance and near and far, but as a lens focusing on medium and near, not only the field of view is narrow but also the image fluctuation and The distortion is still large and cannot be put to practical use. Further, in the conventional progressive multifocal lens focusing on distance, since the distance from the distance eye point E, which is a wearing reference as a spectacle lens, to the near portion N is large,
You need to lower your gaze significantly to move to near vision,
Causes eye strain.

Therefore, in the progressive multifocal lens of the present invention,
Slightly sacrifice the clear vision area of the distance vision, and correct the range up to a specific distance that is substantially farther than the near view (the range up to the distant place with mild presbyopia) according to the degree of presbyopia of the wearer. doing. That is, in the present invention, the feeling of wearing at the time of near work is regarded as the highest priority, and the length of the corridor which ensures little rotational fatigue of the eyeball is secured. In addition, we secure wide near vision part of clear vision zone,
In addition, the maximum astigmatism difference is reduced, a clear viewing area in the middle part is secured to some extent, and the specific viewing distance area is sufficiently widened. In the present invention, the specific viewing distance correction area having a surface refractive power corresponding to a specific distance substantially apart from the foreground is referred to as a “specific viewing section”, and the center of the specific viewing section, that is, the specific center and the near vision section Is referred to as the “length of the progressive zone”, and the amount of increase in refractive power added between the specific center and the near center is referred to as “addition”.

In the present invention, the near eye point is moved from 2 mm to 8 m upward from the near center along the principal meridian curve.
m. In the present invention, the following conditional expression (1) is satisfied in accordance with the setting of the distance range from the near eye point to the near center. _{0.6 <(K E -K A)} / (K B -K A) <0.9 (1) where, K _E: refractive power at the near eye point (dioptres) K _A: in particular the center power (diopter) K _B: refractive power of the near viewing center (diopter) Incidentally, means the refractive power increment in (K _E -K _a) is near eye point relative to the specific center, (K _B− K _A ) means addition.

As described above, in the present invention, since the distance from the near eye point, which is a reference for wearing as a spectacle lens, to the near center is reduced, aberrations generated from the near eye point to the near portion are reduced. Relatively small, good visual characteristics are obtained. In addition, it is possible to shift from intermediate vision to near vision without greatly lowering the line of sight, and it is possible to secure a wide clear vision area in the near vision portion. Also,
As in the present invention, additional power the power increment in the near eye point relative to the specific center _{(K E -K A) (K} B -K
_{When A} ) is set to 60% to 90%, the concentration of astigmatism in the side region from the near eye point to the near portion is reduced, image shake and distortion are suppressed, and the near portion is reduced. In addition, a wide clear vision area can be realized in the middle part.

Further, in the present invention, the refractive power is reduced by 60% to 90% of the addition from the near eye point to the specific visual portion. With this configuration, the visual characteristics are improved from the near eye point to the specific visual portion, and the concentration of aberration in the side region of the main meridian curve is reduced. As a result, image shaking and distortion can be reduced, and a wide clear viewing area can be secured. Further, since the degree of change in the refractive power from the near eye point to the specific viewing portion is relatively small, the connection between the near eye point and the specific viewing portion can be configured to be continuous and smooth. Therefore, it is possible to obtain an intermediate vision state in which image shaking and distortion are relatively small, and it is possible to secure a large clear viewing area of the specific visual section.

If the distance from the near eye point to the near center is shorter than 2 mm, the refractive power on the main meridian curve from the near eye point to the specific center is greatly reduced. As a result, the degree of change in the refractive power increases from the near eye point to the specific visual portion, and it becomes impossible to obtain a favorable intermediate vision state with less image fluctuation and distortion. Further, it is not possible to secure a sufficiently wide clear vision area in the specific visual section.

Further, if the distance from the near eye point to the near center is shorter than 2 mm, the distance from the near eye point to the specific visual portion becomes too long, and the user tends to look upward in the specific visual distance state. I will. On the other hand, if the distance from the near eye point to the near center is longer than 8 mm, it is not possible to shift to the near vision region unless the line of sight is greatly reduced. As a result, eyestrain is caused, and it is not possible to secure a somewhat wide clear vision area in the near portion.

In the present invention, it is desirable to satisfy the following conditional expressions (2) and (3). _{W F ≧ 50 / (K B} -K A) (2) W N ≧ 50 / (K B -K A) (3) where, W _F: maximum width of clear vision area in the specific vision portion (mm) W _N : the maximum width of the clear visual zone in the near portion (mm) When conditional expressions (2) and (3) are not satisfied, a sufficiently wide clear visual zone cannot be secured in the specific visual portion and the near portion. Not preferred.

In the design of the lens surface of such a progressive multifocal lens, design evaluation is performed only within the range of the circular shape of the lens, but a square including the circular shape of the lens surface as shown in FIG. Assuming that the surface shape is designed and evaluated within this square. By optimizing the curved surface on a larger surface that encompasses the circular shape of the lens, it becomes possible to make the practical lens surface smoother and better. In FIG. 6, OG
Is the geometric center of the lens, and W is the radius of the lens.
Curves Φ3 to Φ-3 and Σ0 to Σ3 indicate a cross-section and a vertical cross-section along the z-axis and the y-axis, respectively, which serve as design criteria.

In general, since a progressive multifocal lens is processed in accordance with a spectacle frame, areas of a distance portion, an intermediate portion, and a near portion, particularly, a region of a distance portion and a near portion including a peripheral portion are included. Depends on the shape of the frame. The progressive multifocal lens before processing is generally a circular lens having a diameter of about 60 m or more, and is supplied to an eyeglass retailer as it is in this circular shape, and is processed at the retailer according to a desired eyeglass frame shape. Therefore, in defining the surface shape of the progressive multifocal lens according to the present invention, the circular shape before processing is used as a reference. In designing the optimal surface shape of the progressive multifocal lens, the aberration should be balanced by considering not only the central region that is frequently used but also the surface shape in a wider region including the effective region to be used. Is essential.

An embodiment of the present invention will be described with reference to the accompanying drawings. Before describing a specific embodiment, a design method of a progressive multifocal lens according to the present invention and each point serving as a reference of the progressive multifocal lens will be described first. FIG.
FIG. 3 is a diagram for explaining the state of the eye when the progressive multifocal lens is worn, and shows a cross section along a principal meridian curve, that is, a vertical cross section of the lens. As shown, the eyeball O rotates around the eyeball rotation point CR, so that the line of sight p passes through various points on the lens L. When looking at a nearby object, the face turns downward and the line of sight also drops by the angle α. At this time, if the progressive multifocal lens is worn, the line of sight of both eyes moves on the main meridian curve of the lens L from the intermediate portion to the near portion while converging. The most visible part of the retina where you can see is the macular fovea.If you want to look at the object, turn your eyes to the object so that your gaze matches the position of the fovea. Must be formed at the fossa position. When no adjustment is made, the object-side conjugate position of the fovea position is referred to as an adjustment far point, and the trajectory T of the adjustment far point when the eyeball is rotated is referred to as an aposphere.

FIG. 4 shows the state of the hyperopic eye. Since the accommodation far point of the hyperopic eye is located behind the eye, a far-point sphere T about the rotation point CR can be drawn. Therefore, this is equivalent to the presence of the macular central fovea at the position of the far point spherical surface T. Therefore, a light ray p traveling from the far spherical surface T to the progressive multifocal lens L through the rotation point CR is considered, and the position where the light ray p is refracted by the lens L and converges is the object position.
At this time, if the position of the m image (meridional image) in the direction along the main meridian curve coincides with the position of the s image (sagittal image) in the direction orthogonal to the main meridian curve, a good imaging state is obtained. . However, in general, the m image and the s image do not coincide with each other as shown in the figure, and an astigmatic difference occurs. If the degree of the astigmatic difference is remarkable, the object appears to flow and causes uncomfortable vision such as image distortion.

The curve shown in FIG. 4 shows a change in a point conjugate with the far point spherical surface T, and is a line connecting the average positions of the m image and the s image. This curve corresponds to a so-called addition curve of the progressive multifocal lens L. In the case of FIG. 4, the refractive power of the distance portion is 0 diopter (D), the refractive power of the near portion is 2 diopters, and the addition Ad is 2 diopters. The distance Δ between the m image and the s image corresponds to the astigmatic difference as aberration in the state of wearing the lens. In this way, by performing the performance evaluation of the lens in a state where the progressive multifocal lens is actually worn, the lens design of the progressive multifocal lens that can finally exhibit the best performance in the use state is performed. Becomes possible.

By the way, the center of the specific visual portion, that is, the specific center is a position on the main meridian curve having a predetermined average surface refractive power at the specific visual portion, and is practically a measurement reference point of the specific visual portion. It is a point. Further, the center of the near portion, that is, the near center, is a position on the main meridian curve having a predetermined average surface refraction power at the near portion, and is a point which is practically used as a measurement reference point of the near portion. It is. The near eye point is a position used as a reference when the lens is framed in the spectacle frame, and is a near reference point that matches the near line of sight passage position when the spectacle frame is worn. In the embodiment of the present invention, the position of the near eye point and the geometric center of the lens are matched, but it is not always necessary to match.

FIG. 1 is a diagram showing an outline of area division of a progressive multifocal lens according to an embodiment of the present invention. As shown in FIG. 1, the progressive multifocal lens of the present embodiment has a refractive power that is continuously higher between the specific viewing portion F located above and the near portion N located below during wear. And a changing intermediate portion P. Regarding the shape of the lens surface, the intersection of the cross section along the meridian that runs vertically from the upper part to the lower part at the approximate center of the lens surface in the worn state and the object side lens surface, that is, the principal meridian curve MM ′ indicates the addition of the lens. It is used as a reference line to indicate specifications. In the progressive multifocal lens thus designed symmetrically, the specific center A, the near eye point E, and the near center B are on the principal meridian curve MM '.

As described above, the progressive multifocal lens of FIG.
Along with the principal meridian curve MM ', a near vision portion N having a surface refractive power corresponding to a near view, a specific viewing portion F having a surface refractive power corresponding to a specific distance substantially apart from the near view, Part N
And an intermediate portion P which continuously connects the surface refractive powers of both regions between the specific visual portion F and the specific visual portion F. The specific visual portion F above the specific center A, the near portion N below the near center B, and the intermediate portion P between the specific center A and the near center B can be considered. On the refracting surface of the progressive multifocal lens, the refractive power changes continuously and it is not possible to clearly divide each region. However, as an effective means for considering the structure of the lens, the region division as shown in FIG. Generally adopted.

FIG. 2 is a diagram schematically showing the refractive power distribution on the principal meridian curve of the progressive multifocal lens of this embodiment. In FIG. 2, the vertical axis represents the main meridian curve of the progressive multifocal lens, and the horizontal axis represents the refractive power (unit D: diopter) on the main meridian curve. As shown in FIG. 2, the average power of the surface refractive power on the principal meridian curve is configured to continuously and smoothly connect from the specific center A to the near center B via the near eye point E. ing.

In the progressive multifocal lens of this embodiment, the distance along the main meridian curve from the near eye point E to the near center B is 5 mm. The distance along the main meridian curve from the near eye point E to the specific center A is 14 mm.
It is. Accordingly, the distance from the specific center A to the near center B along the main meridian curve, that is, the length of the corridor is 19
mm. Referring to FIG. 2, in the progressive multifocal lens according to the present embodiment, the average refractive power (base curve) of the specific viewing portion F is 3.5 diopters, and the addition power Ad is 1.5.
Diopter. Therefore, as shown in the figure, the refractive power at the specific center A is 3.5 diopters,
The refractive power at the near center B is 5.0 diopters.

FIG. 5 is an equi-astigmatic curve diagram of the progressive multifocal lens of this embodiment, and shows the result of performance evaluation of the lens in the worn state according to the design method shown in FIG. In FIG. 5, the equi-astigmatic difference curve is shown by a value for each 0.5 diopter. Referring to FIG.
In the progressive multifocal lens of this embodiment, the maximum value of the astigmatic difference is about 1.0 D (diopter), and it can be seen that good intermediate vision and near vision with little image fluctuation and distortion are possible. Further, due to the gentle power gradient from the specific center A to the near eye point E, both the density and the gradient of the line representing the equi-astigmatic difference in the lateral region from below the specific visual portion F to the intermediate portion P decrease. I have.

In this embodiment, in order to facilitate the intermediate vision and near vision, the distance along the principal meridian curve from the near eye point E, which is a reference for wearing as a spectacle lens, to the near center B is 5 mm. Is set small. For this reason, when looking at the front of the face, the dioptric power of the lens matches the intermediate vision and the intermediate vision slightly to the near vision, and the intermediate vision and the intermediate vision slightly facilitate the near vision. Further, as shown in FIG. 5, the aberration generated from the near eye point E to the near portion N is relatively small, and good visual characteristics can be obtained.
The clear vision area of the near portion N can be widened to some extent.

In this embodiment, the increase in refractive power at the near eye point E with respect to the specific center A is determined by the addition Ad
(1.5 diopters) is set to about 75%. That is, the difference between the refractive power at the near center B and the refractive power at the near eye point E is about 0.35 diopter. As a result, the concentration of astigmatism in the side region of the region from the near center B to the center of the intermediate portion P is reduced,
Swaying and distortion of the image are suppressed, and a wide clear vision area is realized in the near portion N and the intermediate portion P as shown in FIG.

Further, in this embodiment, the distance from the near eye point E, which is a reference for wearing as a spectacle lens, to the near center B is set as small as 5 mm. To the near vision region. Further, as shown in FIG.
The maximum width W _N of the clear vision region at is approximately 40 mm, and a sufficiently wide clear vision region can be secured in the near portion N as compared with the conventional progressive multifocal lens. Incidentally, since the addition power Ad is 1.5 diopters, the maximum width W _N of the clear vision zone in the near portion N satisfies the conditional expression (3).

In this embodiment, the near eye point E
To the specific center A, the refractive power on the principal meridian curve is reduced by about 75% of the addition Ad. That is, the difference between the refractive power at the near eye point E and the refractive power at the specific center A is about 1.15 diopters. With this configuration, the visual characteristics are improved from the near eye point E to the specific visual portion F, and the concentration of aberration in the side region of the main meridian curve is reduced. As a result, image shaking and distortion can be reduced, and a wide clear viewing area can be secured.

Further, a specific center A from the near eye point E
Is relatively small (1.15 diopter / 14 mm = 0.082), the connection between the near eye point E and the specific visual portion F is configured to be continuous and smooth. be able to. Therefore, it is possible to obtain an intermediate vision state in which the image has relatively little shaking or distortion. Further, as shown in FIG. 5, the maximum width WF of the clear visual field in the specific visual field _F is about 60 mm, and a sufficiently wide clear visual field is secured in the specific visual field F as compared with the conventional progressive multifocal lens. be able to. Incidentally, the addition degree Ad is 1.5.
Since a diopter, the maximum width W _F of the clear vision area in the specific vision portion F satisfies the conditional expression (2).

In this embodiment, the near eye point E
The distance from to the near center B is set to 5 mm,
The same effect can be obtained even if this distance is set to 2 mm to 8 mm. However, if the distance from the near eye point E to the near center B is shorter than 2 mm, the refractive power on the principal meridian curve decreases from the near eye point E to the specific center A by about 95% of the addition Ad. Will do. As a result, the degree of change in the refractive power increases from the near eye point E to the specific visual portion F, and it is not possible to obtain a favorable intermediate vision state with less image shaking and distortion. Further, it is not possible to secure a sufficiently wide clear vision area in the specific visual section F.

Also, from the near eye point E to the near center B
If the distance to is shorter than 2 mm, the distance from the near eye point E to the specific visual portion F becomes too long, and the user tends to look upward in the specific distance viewing state. On the other hand, the distance from the near eye point E to the near center B is 8
If it is longer than mm, it will not be possible to shift to the near vision region unless the line of sight is lowered significantly. As a result, asthenopia is caused, and it is not possible to secure a certain clear visual area in the near portion N.

It is difficult to completely explain the tendency of the surface refractive power up to the peripheral portion only by the tendency of the surface refractive power on the main meridian curve. However, by the refractive power distribution on the main meridian curve as described above, it is possible to maintain a good aberration balance over the entire lens surface, and to realize a progressive multifocal lens with an excellent visual characteristic, which is focused on near and near. Become. In the present embodiment, the present invention is applied to a progressive multifocal lens that is symmetrical with respect to the principal meridian curve.
The present invention can be applied to an asymmetric progressive multifocal lens in which the near portion is deviated to the nose side.

[0042]

As described above, according to the present invention, it is possible to realize a progressive multifocal lens that can continue near vision comfortably for a long time even for a person who has a large decline in the accommodation power of the eyes. .

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of area division of a progressive multifocal lens according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a refractive power distribution on a principal meridian curve of the progressive multifocal lens of the present embodiment.

FIG. 3 is a diagram schematically showing a refractive power distribution on a principal meridian curve of a conventional progressive power multifocal lens focusing on perspective.

FIG. 4 is a diagram for explaining the state of the eye when the progressive multifocal lens is worn, and shows a cross section along a principal meridian curve, that is, a vertical cross section of the lens.

FIG. 5 is an equi-astigmatic difference curve diagram of the progressive multifocal lens of the present embodiment.

FIG. 6 is a view for explaining a horizontal section and a vertical section which are references for designing the progressive multifocal lens of the present invention.

[Explanation of symbols]

 F Specific vision section N Near section P Intermediate section A Specific center B Near center E Near eye point MM 'Main meridian curve Ad Addition T Far point spherical O Eyeball CR Eyeball turning point L Lens OG Geometric center

Claims (2)

[Claims] 1. A near vision correction area having a surface refractive power corresponding to a foreground substantially apart from a near view along a principal meridian curve dividing a lens refractive surface into a nose side area and an ear side area. A specific viewing distance correction region having a surface refractive power corresponding to the specific distance, and a progressive region that continuously connects the surface refractive power of both regions between the near vision correction region and the specific viewing distance correction region. The center of the near vision correction area is spaced apart from the near eye point by 2 mm to 8 mm along the main meridian curve, and the refractive power at the near eye point is K _E , the refractive power at the center of a particular viewing distance correction area and K _a, when the refractive power at the center of the near vision correction region and a _{K B, 0.6 <(K E} -K a) / (K B -K _a) <progressive multifocal Les characterized by satisfying the condition of 0.9 (1) 'S. Wherein the maximum width of the clear vision area in the specific viewing distance correction area and W _F (mm), the maximum width of the clear vision area in the near vision correction region and W _N (mm), the specific viewing the refractive power at the center of the distance correction area and K _a (diopter), and the refractive power at the center of the near vision correction region and the K _{B (diopter), W F ≧ 50 / (} K B -K a _{) (2) W N ≧ 50} / (K B -K a) (3) progressive multifocal lens according to claim 1, characterized by satisfying the condition.