JP3691876B2 - Lens for correcting presbyopia - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lens for correcting presbyopia, and in particular, it is most suitable for a wide range of objects at close range when a person with presbyopia who has little adjusting power performs indoor desk work, reading, reading a newspaper, etc. The present invention relates to a lens for correcting presbyopia.
[0002]
[Prior art]
Conventionally, mainly in the near work, making up for the decrease in the adjustment function when looking at objects at close distances due to the weakness of the eye lens in the elderly (for example, those in their late 40s or older) Suitable lenses for work include lenses such as single focus lenses and progressive multifocal lenses.
[0003]
A single focus lens is a lens that compensates for the lack of patient's accommodation and focuses on the position of an object at a short distance to be viewed. Since this lens has a small aberration (particularly astigmatism) unless it is an extremely strong power, a clear visual field can be obtained by using almost the entire surface thereof. Further, since the convex surface and the concave surface are spherical lenses, there is no non-rotationally symmetric prism effect, so there is no unnatural fluctuation, but there is distortion, so the object looks distorted. However, the distortion is the same as the distortion caused by the rotationally symmetric prism effect that is felt not only by presbyopia but also by general myopia and hyperopia when wearing glasses. There is no.
[0004]
The basic structure of a progressive multifocal lens is as follows.
In general, the convex surface of a progressive multifocal lens is formed in an aspherical shape having partially different surface refractive powers, and functions to give the refractive power of a lens suitable for viewing from a distant object to the hand. The concave surface is formed in a spherical or toric surface shape and functions to correct myopia, hyperopia, astigmatism, etc. according to the prescription of each eye of the spectacle user.
[0005]
The convex surface structure, which is a feature of the progressive multifocal lens, will be described in more detail. As shown in FIG. 18 (a), on the surface (refractive surface), a distance area F, an intermediate area M, and a near area. N is provided. The distance portion region F is a region having a refractive power suitable for viewing an object at a distance farther than about 1 m to 2 m (hereinafter referred to as far vision). When the intermediate region M sees an object at a medium distance from 50 cm to 1 m to 2 m (hereinafter referred to as intermediate vision), the near vision region N sees an object at a near distance of about 50 cm (hereinafter referred to as near vision). A region having a suitable refractive power.
[0006]
Near the center of the lens surface, a central reference line S is provided so as to extend in the vertical direction, and the lens refractive surface is divided into left and right. The central reference line S is a line in which astigmatism is almost equal to zero from the upper side to the lower side and the refractive power changes progressively, and provides the basic function of the progressive multifocal lens. As shown in FIG. 18A, the center reference line S may be called a “main meridian” when it is divided symmetrically, and may be called a “main gaze line” otherwise.
[0007]
The point A existing on the central reference line S is generally called a distance center and is located in the vicinity of the geometric center of the lens. The point B existing on the central reference line S below the point A is called a near center. Therefore, it can be considered that the distance area F is above the point A, the near area N is below the point B, and the middle area M is the part between them. These areas F, M, and N are effective in considering the lens structure, and are generally used. The refractive power continuously changes on the refractive surface of the lens. Therefore, the areas F, M, and N cannot be clearly divided.
[0008]
FIG. 18B shows the refractive power change on the center reference line S. As shown in this figure, the refractive power (unit: diopter: D) increases progressively from point A to point B. The refractive power D1 in the distance portion region F above the point A and the point B The refractive power D2 in the near-use region N below is substantially constant. The difference between the refractive powers D2 and D1 is called addition, and this addition is usually added within the range of 0.5 diopters (hereinafter referred to as D) to 3.5D.
[0009]
Here, the refractive power of the convex surface of the lens, that is, the surface refractive power will be described.
The surface refractive power has the following relationship with the curvature of the convex surface.
S = (n−1) × C (Diopter)
S: surface power (unit: D), n: refractive index of lens material, C: curvature (unit: m)^-1). In this equation, since the refractive index n is constant, the curvature and the surface refractive power are in a proportional relationship. Accordingly, FIG. 18B can be regarded as a change in the curvature of the center reference line S. Since the curvature changes at the center reference line S provided substantially at the center of the lens in this way, the convex surface of the progressive multifocal lens has an aspheric shape from the distance area F to the near area N. Yes. In an aspherical shape, the value of the curvature at one point on the convex surface varies depending on the direction. Depending on the difference between the maximum value C1 and the minimum value C2 of the curvature at that point (these are called main curvatures), A difference in surface refracting power as shown by the following equation occurs at a point on the lens surface.
[0010]
(N-1) × | C1−C2 | (Diopter)
This appears as astigmatism in the optical performance of the lens. Hereinafter, diopter (D) is used in units of astigmatism, which means a difference in surface refractive power. In this way, the progressive multifocal lens must have an aspherical shape in order to make the portion having different refractive powers one smooth curved surface, and astigmatism is generated in the lens.
[0011]
FIG. 19 shows the distribution of astigmatism in the conventional progressive multifocal lens corresponding to FIG. In this figure, astigmatism is expressed every 0.50D astigmatism lines from 0.50D to 1.00D from the center side of the lens in the same manner as the contour lines of the map. In general, it is said that a person perceives astigmatism and feels blur of an image is 0.5D or more. Therefore, astigmatism increases in the area with the smallest hatching pitch in the figure, that is, the side part of the lens, particularly the side part of the intermediate part and the near part part, and the object cannot be visually perceived because of blurring of the image. It will be. Further, since the image is distorted by this astigmatism, it is perceived as an image shift when the head is moved, and uncomfortable feeling is given during use. On the contrary, a part (white part in the figure) having astigmatism of 0.5D or less is called a clear vision area because it can be seen empirically without feeling blurred. The clear vision area of the intermediate area is generally called a progressive area. If this clear viewing area is accurately expressed as the shape of the lens refracting surface, the following expression is obtained.
[0012]
(N-1) × | C1−C2 | ≦ 0.5 (Diopter)
N: refractive index of the lens material, C1, C2: principal curvatures in different directions at arbitrary points on the lens refracting surface in the clear vision region (unit: m^-1).
[0013]
Thus, it is preferable that there is no astigmatism, but it is impossible to eliminate astigmatism because of the basic configuration of the progressive multifocal lens. That is, for example, even if it is attempted to eliminate the astigmatism of the portion by making the distance portion region and the near portion region completely spherical, the intermediate portion smoothly connecting the distance portion region and the near portion region having different curvatures. The area is forced to undergo a sudden shape change. As a result, large astigmatism occurs in the intermediate region. Conversely, if the clear vision area of the distance area and the near area is narrowed and astigmatism is diffused laterally, the astigmatism in the intermediate area is reduced, and the field of view is reduced in that area. Wide and less image swaying, but distance and near vision are impaired. Therefore, in designing a progressive multifocal lens, it is necessary to minimize the adverse effects of astigmatism on the intended use of the wearer.
[0014]
[Problems to be solved by the invention]
In the above-mentioned single focus lens, the shortage of the adjustment power of the patient is merely compensated, so that the distance that can be seen is limited, for example, a short distance object of 50 cm and a short distance of 25 cm. There is a problem that you cannot see things at once. Therefore, in order to see, for example, an object closer than a predetermined short distance with this lens, a certain amount of adjustment force is required. For example, when trying to see an object at a short distance of 25 cm with a lens that can see a distance of 50 cm, the necessary adjustment force is 2D. That is, 2D (1 / 0.5 m) is required to see an object at a distance of 50 cm, and 4D (1 / 0.25 m) is required to see an object at a distance of 25 cm. Therefore, an adjustment force of 4D-2D = 2D is required. For this reason, when using a single-focus lens, people with little adjustment power adjusted the distance by moving their heads and looked over the desk or read a widened newspaper.
[0015]
For those who have a slight decline in their ability to adjust in their 40s to early 50s, they can see a certain distance range even when using a single focus presbyopia. . However, for example, all the adjustment power that can be held is used to look around the desk, and there is a problem that eye strain is felt due to long-term visual work.
[0016]
It is inevitable to look closer than you can see. For example, when reading a vertical Japanese sentence written in a book of normal size, the distance from the eye will change by about 10 cm at the top and bottom of the sentence. Therefore, it is actually not appropriate for reading glasses to produce near-degree glasses suitable for natural reading, especially when looking at the entire surface of large objects such as newspapers, It is also unsuitable for looking over the entire desk that extends close to the chest.
[0017]
In general single-focus presbyopia, the power is prescribed so that an object located 30 cm to 50 cm away can be clearly seen. People who have little adjustment power have a limited range of visible distances, so they are wearing lenses that prescribe powers that allow individuals to see good distances suitable for reading, such as 30cm or 40cm. .
[0018]
When looking at a book or desk with a single focus lens, the visible range becomes an ellipse that is long horizontally when viewed from the wearer. This is because the width of the clear vision range in the vertical direction (front-rear direction) is narrow because the range of visible distance is narrow, and the width of the clear vision range in the horizontal direction (left-right direction) is a change in distance compared to the vertical direction. This is because it is small and widens. This narrow vertical visibility range is not only inconvenient for reading and writing vertically written text, but also to cover the narrow vertical field of view during desk work. There is inconvenience that you have to move back and forth. Moving the head back and forth to move the line of sight is more painful and unnatural than rotating the neck and shaking the head from side to side.
[0019]
In the progressive multifocal lens described above, even a person with little adjustment power can see a certain range of distance. However, since the clear vision area is extremely narrow compared with a single focus lens, the range where clear vision is possible is limited. In a general progressive multifocal lens, the clear vision region width W1 of the distance portion region F is wide, but the clear vision region width W3 of the near portion region N is narrow. Further, the width W2 of the clear vision area (progressive area) of the intermediate area M is extremely narrow compared to the widths W1 and W3. Therefore, there is a problem that a wide and clear field of view cannot be obtained when an object at a short distance is viewed in the near portion area N.
[0020]
In the middle region M, objects farther away than close objects can be seen. However, since the width W2 of the clear vision area is narrow, particularly when the addition exceeds 2.50D, the gap between the doors can be seen. It was difficult to see intermediate vision as if I was watching. In order to see an object at a nearer distance than an object at a near distance in the near vision area N, an area having an intensity number higher than the near vision power may be provided at the lower part of the area N. Difficult to use. In addition, a person who still has adjustment power tends to cause eye strain because he / she can see the object in the region of the intensity number by using the adjustment power to the maximum.
[0021]
Furthermore, research has revealed that progressive multifocal lenses have characteristics that should be explained by the concept of quasi-clear vision in addition to clear vision.
When this semi-bright viewing area is accurately expressed as the shape of the lens refracting surface, the following expression is obtained.
[0022]
(N-1) × | C1−C2 | ≦ 0.75 (Diopter)
N: refractive index of the lens material, C1, C2: principal curvatures in different directions at arbitrary points on the lens refracting surface in the clear vision region (unit: m^-1).
[0023]
When viewing an object with a progressive multifocal lens, not only the clear vision area but also the area that is unconsciously beyond the clear vision area is used. Therefore, it is desirable that astigmatism is as small as possible even in a region other than the clear vision region. That is, it is desirable to secure a wide area around the clear vision area where the value exceeding astigmatism 0.5D is as small as possible.
[0024]
If the lens has a wide quasi-clear vision area, it will not unintentionally see objects in areas with greater astigmatism outside the quasi-clear vision area, and there will be less distortion in the clear vision area and quasi-clear vision area. A wide field of view is obtained.
[0025]
This semi-bright viewing area can be defined as (n-1) × | C 1 −C 2 | ≦ 1.00 (diopter), but in order to obtain a clear field of view with less distortion, quasi-brightness of 0.75 D or less. A viewing zone is desirable.
[0026]
In the conventional progressive multifocal lens, in the semi-clear vision area, the distance area F and the near area N are wide, and the intermediate area M is narrow, like the clear vision area. This is because intermediate vision is sacrificed as much as far vision and near vision are emphasized. Therefore, when an eye point (not shown) provided in the vicinity of the distance center A is set to a normal line-of-sight position, a region with large astigmatism is arranged in the vicinity of the eye point, and a field of view with less distortion is obtained. It is narrower.
[0027]
The present invention has been made to solve the above-mentioned problems, and the purpose thereof is extremely low use frequency when looking at objects at long and medium distances, and visual work mainly involving short distances such as desk work and reading It is ideal for a person who does not have the ability to adjust not only to see an object at a predetermined short distance, but also to easily see an object at a distance slightly closer than the short distance and an object at a short distance. It is an object of the present invention to provide a lens for correcting presbyopia capable of obtaining a wide and clear visual field when viewing the object.
[0028]
[Means for Solving the Problems]
  In order to achieve the above-mentioned object, the invention according to claim 1 includes two lenses constituting the lens.lensAt least one lens refracting surface among the refracting surfaces extends in the vertical direction of the lens refracting surface so that the astigmatism is minimized.lensA central reference line that divides the refractive surface into left and right, a near center provided on the central reference line, provided on the central reference line and above the near center, and from the refractive power of the near center. A weakness center that gives a weak refractive power, an intensity center that is provided on the central reference line and below the near center, and that gives a stronger refractive power than the near center, and the weakness Provided between the center and the intensity center, and a predetermined refractive power progressively increases from the weakness center to the intensity center through the near center.increaseA difference in refractive power between the weakness center and the intensity center is in the range of 0.50D to 4.00D. In the increased region, n: refractive index of the lens material, C1, C2: principal curvature in a different direction at a point on the lens refractive surface (unit: m^-1)
        (N-1) × | C1−C2 | ≦ 0.5 (m^-1)
The clear vision area defined by the conditions of
        (N-1) × | C1−C2 | ≦ 0.75 (m^-1)
And the horizontal width of the clear vision region in the increase region is maximized at a position near the geometric center of the lens or near the weakness center. The horizontal width of the semi-clear vision region in the increased region is the maximum at a position near the geometric center.In the region above the geometric center, assuming a plane passing through the geometric center and perpendicular to the central reference line, a first intersection line between the plane parallel to the plane and the lens refracting surface is A non-circular curve whose curvature increases as it moves away from the intersection of the central reference lines in the horizontal direction, assuming a plane that passes through the geometric center and is perpendicular to the central reference line in a region below the geometric center, A second intersection line between the plane parallel to the plane and the lens refracting surface is a non-circular curve whose curvature decreases as the distance from the intersection of the central reference line in the horizontal direction, and a horizontal line passing near the geometric center. Assuming that the distances in the upper region and the lower region from the horizontal line are equal, and the distances in the upper region and the lower region from the central reference line are equal, any two points And increasing rate of curvature of said first intersection line through each is approximately equal to the rate of decrease in the curvature of the second line of intersectionThis is the gist.
[0029]
The invention according to claim 2 is characterized in that, in the lens according to claim 1, the near center is disposed within 2 mm to 15 mm below the geometric center of the lens.
[0030]
The gist of the invention according to claim 3 is that the lens according to claim 1 or 2 has a wearing point arranged within 15 mm above the near center.
According to a fourth aspect of the present invention, in the lens according to any one of the first to third aspects, a vertical length in the increased region is 20 mm or more, and the weakness center and the strength center The difference is that the difference in refractive power is between 1.00D and 2.00D.
[0031]
According to a fifth aspect of the present invention, in the lens according to any one of the first to third aspects, a length in the vertical direction in the increased region is 14 mm or more and less than 25 mm, and the weakness center and the strength. The gist of the difference in refractive power from the center is in the range of 0.50D to 1.50D.
[0033]
According to the first aspect of the present invention, in the increased region above the near center, the refractive power gradually decreases from the near center toward the weak center. Thus, it is possible to easily see objects from a predetermined short distance to a distance slightly longer than the short distance. In addition, in the increasing region below the near center, the refractive power gradually increases from the near center toward the intensity center, so that the distance from the predetermined near distance to a distance slightly closer than the near distance. It becomes possible to see easily without adjusting things. Therefore, in an increasing area above and below the near center, a person with little adjustment power looks, for example, over the entire desk or reads the entire newspaper without moving his head back and forth. Such visual work can be performed.
[0034]
The reason why the difference in refractive power between the weakness center and the intensity center is set to 0.50D to 4.00D is as follows. When the refractive power becomes smaller than 0.50D, not only a predetermined short distance but also a distance or a distance that can be looked over is almost the same as the predetermined short distance, and a single focus lens is used. It will be almost the same thing. If the refractive power is greater than 4.00D, the difference in refractive power from the center of weakness to the center of intensity becomes too large, making it difficult for the user to use.
[0035]
For example, when the refractive power of the near vision center is 2.50 D (diopter), even a person who has normal adjustment and little adjustment power has 40 cm (1 / 2.50 = 0.4 m at the near vision center, and so on. You can see objects that are close to each other. Here, when the difference in refractive power is set to 0.50D, an object having a distance of about 44 cm can be seen in the weakness center and the vicinity thereof, and an object having a distance of about 36 cm can be seen in the intensity center and the vicinity thereof. Can see. If the difference in refractive power is 4.00D, an object with a distance of about 2 m can be seen in the weakness center and the vicinity thereof, and an object with a distance of about 22 cm can be seen in the intensity center and the vicinity thereof. be able to.
[0036]
  Furthermore, astigmatism is diffused to the left and right of the upper part of the lens and to the left and right of the lower part of the lens by maximizing the horizontal width of the semi-clear vision region in the vicinity of the geometric center of the lens. As a result, lateral astigmatism in the vicinity of the geometric center is reduced, so that a wide and clear visual field can be obtained in the central portion of the lens in the vicinity of the geometric center that is relatively frequently used as a presbyopia correcting lens.
Also, in the area above the geometric center, the refractive power of the horizontal section increases as the distance from the central reference line increases in the horizontal direction, and in the area below the geometric center, the refractive power of the horizontal section increases as it moves away from the central reference line in the horizontal direction. Decrease. This increase and decrease in refractive power reduces the frequency difference between the upper and lower regions. As a result, the surface connection from the upper region to the lower region is smooth, and astigmatism and distortion are less concentrated on the side of the geometric center, and the side view in the vicinity of the geometric center is improved.
In addition, in the upper region and the lower region, assuming a horizontal line passing through the geometric center, the increase rate of the first curvature passing through any two points vertically symmetrical with respect to the horizontal line and the decrease rate of the second curvature are substantially equal. As a result, the curvature in the horizontal direction of the lens changes symmetrically with respect to a horizontal line passing through the geometric center. As a result, astigmatism is suppressed to be small in the region near the center of the lens that is used most frequently, and astigmatism is dispersed in the left and right regions of the upper and lower portions of the lens that are used less frequently.
Furthermore, in the lower region, the refracting power of the horizontal section decreases as the distance from the central reference line in the horizontal direction decreases. Therefore, it is convenient to view, for example, a desk or a front side surface of a newspaper in a region near the center of intensity. This is because the distance when viewing the front side surface on a desk or the like is larger than the distance when viewing the front side. According to the present invention, the distance that can be viewed from the side increases due to the decrease in refractive power described above, and the side surface located at a distance slightly longer than the distance when viewing the front from the vicinity of the intensity center can be viewed relatively clearly. It becomes possible.
[0037]
According to the second aspect of the present invention, the near center is disposed within 2 mm to 15 mm below the geometric center of the lens, so that it is between an arbitrary point near the near center and the near center. In this case, the wearer can move the eyes in the vertical direction without burden, and can see an object at a distance slightly closer than the short distance.
[0038]
In the invention according to claim 3, by arranging the wearing point within 15 mm above the near center, the wearer can move the eyes vertically between the wearing point and the near center without burden. It becomes possible.
[0039]
According to the fourth aspect of the present invention, since the vertical length in the increasing region is set to 20 mm or more, the refractive power gradient between the weakness center and the intensity center on the central reference line of the increasing region is compared. And the generated aberration is reduced. In particular, when the difference in refractive power in the increased region is set to 1.00D to 2.00D, the gradient of refractive power is not stiff and the generated aberration (astigmatism and distortion) is reduced. Therefore, the clear vision area and the semi-clear vision area are widened, and the fluctuation and distortion of the image are reduced when the line of sight is shifted between the weakness center and the intensity center.
[0040]
For example, the refractive power of the near vision center is 2.50 D, and the short distance that can be viewed at the near vision center is about 40 cm. When the difference in refractive power is set to 1.00D, an object with a distance of about 50 cm can be seen in the weakness center and the vicinity thereof, and an object with a distance of about 33 cm can be seen in the intensity center and the vicinity thereof. it can. When the difference in refractive power is set to 2.00 D, an object with a distance of about 67 cm can be seen in the weakness center and the vicinity thereof, and an object with a distance of about 29 cm can be seen in the intensity center and the vicinity thereof. be able to.
[0041]
According to the invention described in claim 5, even if the length in the vertical direction in the increased region is 14 mm or more and less than 25 mm, the difference in refractive power is set to 0.50D to 1.50D. It is possible to obtain a lens with less image fluctuation and distortion.
[0042]
For example, when the refractive power of the near vision center is 2.50D and the short distance that can be seen at the near vision center is 40 cm, the difference in refractive power is 0.50D. Similarly, objects with a distance of about 36 to 44 cm can be seen. When the difference in refractive power is set to 1.50 D, an object with a distance of about 57 cm can be seen in the weakness center and the vicinity thereof, and an object with a distance of about 31 cm can be seen in the intensity center and the vicinity thereof. it can.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
[0047]
As shown in FIG. 1A, a central reference line S is provided on the convex side of the lens refractive surface 2 of a presbyopia correcting lens (hereinafter simply referred to as a lens) 1 so as to extend in the vertical direction. A near center A is provided 2 mm below the geometric center O of the lens 1 on the central reference line S. The geometric center O may not be on the central reference line S. A weakness center B is provided 13 mm above the geometric center O on the central reference line S. An intensity center C is provided 17 mm below the geometric center O on the central reference line S.
[0048]
As shown in FIG. 2, a weakness region 3 is provided above the weakness center B of the lens refracting surface 2. An intensity region 4 is provided below the intensity center C of the lens refracting surface 2. Between the weakness area 3 and the intensity area 4 of the lens refracting surface 2, an intermediate area 5 is provided. The diameter of the lens 1 is 50 mm.
[0049]
The center reference line S is a line (so-called navel curve) having the smallest astigmatism and almost zero. Even if it says a line, it is a virtual thing and the line cannot be confirmed visually.
[0050]
The near vision center A is a refractive power suitable for correcting a presbyopia when a person with normal vision that is neither hyperopia or myopia is presbyopia and sees an object at a short distance (in this case, 2.50D: Diopter). In this embodiment, since the refractive power is 2.50 D, the short distance (near point) suitable for viewing is 40 cm. Here, the distance of 40 cm is based on the calculation of 1 / 2.50D = 0.40 (m). The weakness center B has a refractive power (in this case, 1.75D) that is weaker than the refractive power of the near vision center A, and the weakness region 3 has almost the same refractive power as the weak refractive power. . Therefore, in the weakness center B and the weakness area 3, it is possible to see an object at a distance slightly longer than the near point. In this embodiment, since the refractive power is 1.75D, the distant distance that can be seen is 57 cm. Here, 57 cm is based on the calculation of 1 / 1.75D = 0.57 (m).
[0051]
The intensity center C has a refractive power (in this case, 3.25D) stronger than the refractive power of the near center A, and the intensity region 4 has almost the same refractive power as the strong refractive power. Therefore, in the intensity center C and the intensity region 4, it is possible for a person without adjustment power to see an object at a distance slightly closer than the near point. In the present embodiment, since the refractive power is 3.25D, the nearby distance that can be seen is 31 cm. Here, 31 cm is based on the calculation of 1 / 3.25D = 0.31 (m).
[0052]
The intermediate region 5 is a region in which a predetermined refractive power gradually increases from the weakness center B through the near center A to the intensity center C. As shown in FIG. 1B, the intermediate region 5 has a refractive power difference of 1.50 D between the weakness center B and the intensity center C in the present embodiment. The refractive power of 1.50D (in-lens change frequency) is progressively increased. Accordingly, in the intermediate region 5, the frequency changes from a weak frequency of 1.75D to an intensity number of 3.25D. Here, the power means a refractive power (lens power) obtained by combining the refractive power of the refractive surface on the convex surface side of the lens 1 and the refractive power of the refractive surface on the concave surface side. The intermediate region 5 has a progressive portion 6 that is a clear vision region having astigmatism of 0.50 D or less in a region including the central reference line S. The gradient of refractive power in the progressive portion 6 can be expressed by the changing frequency and the length of the progressive portion 6. In the present embodiment, the gradient = 1.50 D / 30 mm = 0.05 (D / mm). Yes.
[0053]
Next, the frequency distribution of the lens 1 will be described.
As shown in FIG. 3, the frequency distribution is represented by an iso-frequency curve connecting points having the same frequency magnitude. In the horizontal direction of the intermediate area 5, the power of 2.50 D is represented by a substantially straight iso-power curve 101 passing through the near center A. A frequency of 2.25D is represented by an iso frequency curve 102 in the intermediate region 5 above the iso power curve 101, and a frequency of 2.00D is represented by an iso power curve 103 further upward. In the weakness area 3, the power of 1.75D is represented by an isopower curve 104 that passes through the weakness center B.
[0054]
In the intermediate region 5 below the isofrequency curve 101, a frequency of 2.75D is represented by an isopower curve 105, and further below, a frequency of 3.00D is represented by an isofrequency curve 106. In the intensity region 4, a frequency of 3.25D is represented by an isopower curve 107 passing through the intensity center C. Each isopower curve 101-107 is not actually visible.
[0055]
In the intermediate region 5 and the weak region 3 above the iso frequency curve 101, the iso power curves 102 to 104 are curved upward as they are about 15 mm away from the central reference line S in both the left and right directions, and then curved downward. It has become. That is, the frequency increases as the distance from the central reference line S increases, and then decreases.
[0056]
In the intermediate region 5 below the iso power curve 101, the iso power curves 105 to 107 are curved downward as they are about 15 mm away from the central reference line S in both the left and right directions, and then curved upward. That is, the frequency decreases and then increases as the distance from the central reference line S increases. The iso power curves 102 to 104 and the iso power curves 105 to 107 are substantially vertically symmetric, and the change from increasing to decreasing in the regions 5 and 3 above the iso power curve 101 is changed. The state and the state of change from decreasing to increasing in the lower regions 5 and 4 are vertically symmetrical.
[0057]
Further, in the progressive portion 6, the curves of the equal power curves 102 to 106 from the central reference line S to about 10 mm in both the left and right directions are gentle, and the change in the power is small compared to the area of 10 mm or more. It is a relatively stable area. Therefore, in the intermediate region 5, particularly in the region of the progressive portion 6, it is possible to see well an object having a distance between a viewing distance of 57 cm at the weakness center B and a viewing distance of 31 cm at the intensity center C. It has become.
[0058]
As shown in FIGS. 1A and 2, the wearing point P is located at a position 2 mm above the geometric center O and shifted by 2 mm from the geometric center O to the ear side of the lens 1 (the right side of the lens in FIG. 1). Is set. This wearing point P may be arranged at the same height as the geometric center O. When viewed from the wearing point P, the near center A is disposed 4 mm below the wearing point P and 2 mm on the nose side. The wearing point P is a point through which a line of sight passes when looking far away when wearing the lens 1 with the lens 1 framed in a spectacle frame. In the present embodiment, by arranging the wearing point P on the ear side, the entire lens moves to the nose side during wearing, and this corresponds to the convergence of the eye when looking at an object at a short distance from the near-use center A. It can be done.
[0059]
Next, the clear vision area and the semi-clear vision area in the weakness area 3, the intensity area 4, and the intermediate area 5 will be described. The clear vision area and the semi-clear vision area are defined according to the following equations (1) and (2), respectively.
[0060]
Clear viewing area (n-1) × | C1-C2 | ≦ 0.50 (m^-1) ... (1)
Semi-clear vision area (n-1) × | C1−C2 | ≦ 0.75 (m^-1) ... (2)
n: refractive index of the lens material, C1, C2: principal curvatures in different directions at points on the lens refractive surface (unit: m^-1)
The region with astigmatism 0.5D or less becomes a clear vision region by the above equation (1), and the region with astigmatism 0.75D or less by the above equation (2) becomes a semi-clear vision region.
[0061]
As shown in FIG. 1 (a), the astigmatism curves AS1 to AS3 on the lens refracting surface 2 have astigmatism magnitudes of 0.25D, 0.50D, and 0.75D in diopter units. Respectively. The region surrounded by the astigmatism curve AS2 is the clear vision region, and the region surrounded by the isoastigmatism curve AS3 is the quasi-clear vision region. These isoastigmatism curves AS1 to AS3 are actually not visible to the eye.
[0062]
The horizontal width of the progressive portion 6 is approximately 12 mm and is substantially constant. Strictly speaking, the progressive portion 6 has a maximum width of 12 mm at a position 2 mm below the geometric center O, and a minimum width of 11 mm at the positions of the weakness center A and the intensity center C. Therefore, the maximum width is 1.1 times the minimum width.
[0063]
The semi-clear vision area of the intermediate area 5 has a maximum horizontal width W of 40 mm at the position of the geometric center O (in this case, 2 mm above the near center A)._maxThe minimum width W in the horizontal direction of 20 mm at the position of the weakness center A and the strength center C_minhave. Therefore, the maximum width W_maxIs the minimum width W_minIt is 2.0 times longer than that.
[0064]
Next, the refractive power distribution of the lens refracting surface 2 that provides the above-described power, clear vision region, and semi-clear vision region will be described.
As shown in FIG. 4, although not shown, a plane passing through the geometric center O and perpendicular to the central reference line S is assumed, and a plurality of planes parallel to the plane (hereinafter referred to as a horizontal cross section) and the lens refracting surface are shown. Assume lines of intersection L1 to L8 with 2. In this embodiment, refracting power ((n-1) / R (D: diopter), n: refractive index of lens material, R: radius of curvature) is used to represent the intersection line.
[0065]
The intersection line L1 passes through the weakness center A 15 mm above the near center A. The intersection line L2 passes through the intersection point E1 of the central reference line S 10 mm above the near center A. The intersection line L3 passes through the intersection point E2 of the central reference line S 5 mm above the near center A. The intersection line L4 passes through the near center A.
[0066]
The intersection line L5 passes through the intersection point E3 of the central reference line S 5 mm below the near center A. The intersection line L6 passes through the intersection point E4 of the central reference line S 10 mm below the near center A. The intersection line L7 passes through the intensity center C 15 mm below the near center A. The intersection line L8 passes through the intersection point E5 of the center reference line S 20 mm below the near center A.
[0067]
As shown in FIG. 5 (a), the intersection lines L1 to L4 have a refractive power, that is, a refractive power of a horizontal section as the distance from the near center A, the intersections E1 and E2 and the weakness center B increases by about 15 mm in the horizontal direction. Hereinafter, it becomes a non-circular curve that increases and decreases again.
[0068]
The intersection lines L5 to L8 are noncircular curves in which the horizontal refractive power decreases and increases again as the distance from the intersections E3 to E5 and the intensity center C increases by about 15 mm in the horizontal direction. Note that the increase and decrease in refractive power are symmetrical, so only the right side is shown.
[0069]
Next, although not shown, a plane passing through the geometric center O and perpendicular to the central reference line S is assumed, and an intersection line between the plane and a refracting surface (hereinafter referred to as a progressive surface) in the intermediate region 5 is defined as a horizontal reference. A line is assumed, and an intersection line (not shown) between a surface perpendicular to the horizontal reference line (hereinafter referred to as a vertical cross section) and the refracting surface 2 is assumed. This intersecting line is a line that intersects each of the intersecting lines L1 to L8.
[0070]
As shown in FIG. 5B, at the intersections between the intersection lines L1 to L8 and the intersection line (not shown), the refractive power of the vertical section (hereinafter referred to as the vertical refractive power) is the near center A and the intersection points E1 to E4. As the distance from the weakness center B and the intensity center C increases, the values hardly change and become substantially constant. Therefore, the vertical refractive power on the progressive surface has a smaller rate of change in the horizontal direction than the horizontal refractive power.
In the lens 1 configured as described above, the intermediate region in which a predetermined refractive power (1.50 D) progressively increases from the weakness center B through the near center A to the intensity center C. 5 was provided. Accordingly, in the intermediate region 5 above the near center A, the refractive power gradually decreases from the near center A toward the weakness center B. Objects from a short distance (40 cm) to a distance (57 cm) slightly longer than the short distance can be easily seen. In the intermediate region 5 below the near center A, the refractive power gradually increases from the near center A toward the intensity center C. Objects up to a distance (31 cm) slightly closer than the distance can be easily seen without adjustment.
[0071]
Further, by providing the weakness region 3 having substantially the same refractive power as the weakness center B above the weakness center B, an object at a slightly far distance (57 cm) can be seen in a wide range. By providing the intensity region 4 having substantially the same refractive power as the intensity center C below the intensity center C, an object at a slightly close distance (31 cm) can be seen in a wide range. Therefore, in a region above and below the near center A, for example, a person who has little adjustment power looks over the entire desk or reads the spread newspaper without moving his head back and forth. Such visual work can be performed. Also, there are extremely few opportunities to see objects at long and medium distances, and visual work mainly based on short distances, for example, desk work in the room, reading, newspaper reading, surgery such as surgery, machine tool work such as a lathe, etc. It is most suitable when doing. Furthermore, since adjustment power is not required when looking at objects far away or close to a short distance, eye fatigue does not easily occur even when the lens 1 is worn for a long time, and a comfortable wearing feeling is obtained. be able to.
[0072]
In the lens 1 configured as described above, the horizontal refractive power increases in the region above the near center A until it is about 15 mm away from the central reference line S, and conversely decreases in the region below. are doing. For this reason, the rate of increase and decrease in the horizontal refractive power of the intersection line L4 passing through the near center A is smaller than that of the other intersection lines L1 to L3. Further, the rate of change in the horizontal direction of the vertical refractive power is small. Therefore, at the position of the near center A, the undulation of the curved surface is suppressed, the horizontal cross section becomes a shape close to a circle, and the horizontal image magnification is substantially constant. As a result, the astigmatism in the horizontal direction is reduced at the position of the near center A, the width of the progressive portion 6 is made substantially constant, the width at the position of the near center A is maximized in the horizontal direction, and Can maximize the width of the semi-clear vision region at a position near the near center A.
[0073]
By making the horizontal width of the semi-bright viewing area maximum at the position of the geometric center O, astigmatism is diffused to the left and right above the lens 1 and to the left and right below the lens 1. As a result, the lateral astigmatism at the position of the near vision center A is reduced, so that the most frequently used region as a presbyopia correcting lens, that is, the center of the lens 1 in the vicinity of the near vision center A or the geometric center O. A wide and clear field of view can be obtained.
[0074]
The width of the progressive portion 6 is about 12 mm, and the minimum width of the progressive portion 6 between the distance center and the near center of a conventional general progressive multifocal lens is 3 to 7 mm. In the progressive part 6 of the present embodiment, it is possible to see an object that is a little farther or closer than the short distance, and in the conventional progressive part, it is possible to see a medium distance object between the long distance and the short distance. However, from the numerical point of view, it can be seen that the progressive portion of the present embodiment is sufficiently wide.
[0075]
Further, since the width (12 mm) of the progressive portion 6 is equal to or larger than the maximum width value 6 to 15 mm of the near portion region of the conventional progressive multifocal lens, it is clear for near vision. Sufficient area is secured. Therefore, a clear visual field can be obtained during near vision. Since the progressive portion 6 is an area having astigmatism of 0.50 D or less, image distortion is suppressed as much as possible in the area. FIG. 6 shows a distortion diagram when the square lattice is viewed through the lens 1. As shown in this figure, in a region where astigmatism (shown by a broken line) is 0.50 D or less, the grating viewed through the lens 1 is slightly enlarged in the intensity region 4, but is almost equal to the original square. It has become. Therefore, in the region where the astigmatism is 0.50 D or less, image distortion can be suppressed as much as possible, and fluctuations when moving the line of sight can be reduced.
[0076]
Further, since the astigmatism is an area having astigmatism of 0.75 D or less in the quasi-clear vision area, image distortion is relatively suppressed in the area. This semi-bright viewing area is wider than that of a general progressive multifocal lens as shown in FIG. 19 in comparison with the lower half of the lens. Therefore, the lower half of the lens is significantly less distorted than the conventional progressive multifocal lens.
[0077]
In addition, since the rate of change in the horizontal direction of the vertical refractive power is small, the rate at which prisms are generated in the vertical direction is reduced, and it is possible to reduce the sensation that an object moves up and down when the face is swung left and right. . Furthermore, since the rate of change of the vertical refractive power in the horizontal direction is small, the difference between the vertical refractive power and the horizontal refractive index is not enlarged, and astigmatism can be further reduced.
[0078]
Further, in the lens 1 of the present embodiment, the progressive power 6 increases the refractive power for obtaining a slightly weaker power and a stronger power with respect to the near power. Therefore, unlike the case where the power for obtaining the near power is added to the distance power of the general progressive multifocal lens, the refractive power to be increased by the progressive portion 6 of the lens 1 can be small. Therefore, for example, even if the length of the progressive portion of the conventional progressive multifocal lens is the same as the length of the progressive portion 6 provided between the weakness center B and the intensity center C, in the progressive portion 6 The increasing refractive power is smaller than the addition power of the conventional progressive multifocal lens. As a result, the gradient of refractive power on the central reference line S of the progressive portion 6 (gradient = 0.05 in this embodiment) becomes gentle, and the aberration (astigmatism and distortion) generated in the progressive portion 6 is small. Become. Then, the clear vision area and the semi-clear vision area are widened, and the image shake is reduced when the line of sight is shifted between the weakness center B and the intensity center C in the progressive portion 6.
[0079]
Next, spectacles using the presbyopia correcting lens 1 of the first embodiment will be described.
As shown in FIG. 7, the glasses 7 are composed of a glasses frame 8 and two lenses for correcting presbyopia 1. The eyeglass frame 8 is processed into a lens shape so that the wearing point P of the lens 1 coincides with an eye point (distance eye point) (not shown) set on the left and right eyeglasses 9 according to the wearer. Each is framed. The eye point is a point through which the line of sight passes when viewed from a distance, and is also called a fitting point. Each lens 1 is framed in a state of being rotated by a predetermined angle θ (in this case, 2 degrees) to the nose side with respect to the vertical direction around the geometric center O. Therefore, the intensity center C is displaced (so-called inward) from the wearing point P to the nose side by 2.5 mm in consideration of near-field vision.
[0080]
In the glasses 7 configured as described above, near vision can be performed in a state where a wide clear vision area is secured in the intermediate region 5 including the wearing point P and the near center A. Further, when performing near vision by moving the line of sight between the weakness center B and the intensity center C in the region of the progressive portion 6, the image shake is reduced.
[0081]
(Second Embodiment)
Next, a second embodiment will be described. In addition, the same code | symbol is attached | subjected about the structure similar to the said 1st Embodiment.
[0082]
As shown in FIG. 8A, a weakness center B is provided 7 mm above the geometric center O on the central reference line S. An intensity center C is provided 11 mm below the geometric center O on the central reference line S.
[0083]
The weakness center B has a refractive power (in this case, 2.00 D) that is weaker than the refractive power of the near center A (2.50 D), and the weakness area 3 has almost the same refractive power as the weak refractive power. have. In this embodiment, since the refractive power is 2.00 D, the distant distance that can be seen is 50 cm.
[0084]
The intensity center C has a refractive power (3.00D in this case) that is stronger than the refractive power of the near center A, and the intensity region 4 has almost the same refractive power as the strong refractive power. In the present embodiment, since the refractive power is 3.00D, the distance that can be seen is 33 cm.
[0085]
As shown in FIG. 8B, in this embodiment, the difference in refractive power between the weakness center B and the intensity center C is 1.00D, and the intermediate region 5 has a 1.00D refraction. The force (frequency of change in the lens) increases progressively. Therefore, in the intermediate area 5, the frequency changes from a weak power of 2.00D to an intensity power of 3.00D, and in the progressive part 6, a person without adjustment power performs near vision from 50 cm to 33 cm. Are suitable.
[0086]
The length of the progressive portion 6 is 18 mm, and the gradient of refractive power in the progressive portion 6 is 1.00 D / 18 mm = 0.06 (D / mm).
The horizontal width of the progressive portion 6 is approximately 10 mm and is substantially constant. Strictly speaking, the progressive portion 6 has a maximum width of 11 mm at the position of the geometric center A 2 mm below the geometric center O, and has a minimum width of 10 mm at the positions of the weakness center A and the intensity center C. are doing. Therefore, the maximum width is 1.1 times the minimum width.
[0087]
The semi-bright viewing area is the maximum horizontal width W of 34 mm at the position of the geometric center O (in this case, 2 mm above the near vision center A)._maxThe minimum width W of 17 mm at the position of the weakness center A and the strength center C_minhave. Therefore, its maximum width W_maxIs the minimum width W_minIt is 2.0 times longer than that.
[0088]
Although not shown, the iso-frequency curves E1 to E7 are substantially the same as the changes in the frequency increase and decrease in the first embodiment.
As shown in FIG. 9A, the refractive powers at the intersections E3 to E5 and the intensity center C excluding the near center A are slightly smaller than the refractive powers in the first embodiment, and the intersections E1, E2 and the weaknesses. The refractive power at the center B is slightly larger than the refractive power in the first embodiment. The intersecting lines L1 to L8 are non-circular curves in which the horizontal refractive power increases or decreases in the same manner as in the first embodiment, according to the slightly smaller or larger refractive power.
[0089]
In the lens 1 configured as described above, since the difference in refractive power between the weakness center B and the intensity center C is 1.00D, even if the length of the progressive portion 6 is reduced to 18 mm, the refractive power Can be maintained at substantially the same value (0.06) as that of the first embodiment (0.05). As a result, an effect similar to that of the first embodiment can be obtained, and a lens with less image fluctuation and distortion can be obtained.
[0090]
(Third embodiment)
Next, a third embodiment will be described. In addition, the same code | symbol is attached | subjected about the structure similar to the said 1st Embodiment.
[0091]
As shown in FIG. 10, a meridian T extending in the vertical direction through the geometric center O is defined. The central reference line S1 in the region above the geometric center O (the region including the upper portion of the intermediate region 5 and the weak region 3) is displaced to the nose side by about 1.0 to 2.0 mm parallel to the meridian T. are doing. Further, the central reference line S2 in the region below the geometric center O (the region including the lower portion of the intermediate region 5 and the strength region 4) is displaced so as to move away from the meridian T toward the nose side. are doing.
[0092]
A near center A is provided 2 mm below the geometric center O and on the 2 mm nose side center reference line S2. On the center reference line S1 7 mm above the geometric center O, the weakness center B is provided. On the center reference line S2 11 mm below the geometric center O, the intensity center C is provided. A wearing point P is provided on a central reference line S1 2 mm above the geometric center O. And in this embodiment, the length of the progressive part 6 is 18 mm, and is the same length as 2nd Embodiment. The refractive power at the near center A, the weakness center B, and the intensity center C is the same as in the second embodiment, and the refractive power gradient on the central reference line S of the progressive portion 6 is 1.00 D / 18 mm. ≈0.06. The diameter of the lens 1 is 70 mm.
[0093]
The refracting surface 2a in the region above the geometric center O has an asymmetry distribution of astigmatism in a region within 15 mm from the nose side to the ear side with respect to the horizontal direction when worn with the central reference line S1 as a boundary. It has become. Further, the refractive surface 2a of the astigmatism on the ear side in the horizontal direction has a slower change than the distribution of astigmatism on the nose side.
[0094]
The refractive surface 2b in the region below the geometric center O has an asymmetry distribution of astigmatism in a region within 15 mm from the nose side to the ear side with respect to the horizontal direction at the time of wearing with the central reference line S2 as a boundary. It has become. Further, the refractive surface 2b of the astigmatism on the ear side in the horizontal direction has a slower change than the distribution of astigmatism on the nose side.
[0095]
The refractive power distribution of the lens refractive surface 2 is shown in the horizontal refractive power graph of FIG. 12 and the vertical refractive power graph of FIG. In FIG. 12, the intersection lines L1 to L4 show that the horizontal refractive power increases and decreases again as the distance from the near center A, the intersections E1 and E2 and the weakness center B is about 14 mm away from the nose side and about 16 mm away from the ear side. It is a circular curve.
[0096]
The intersection lines L5 to L8 are noncircular curves in which the horizontal refractive power decreases as the distance from the intersections E3 to E5 and the intensity center C to the nasal side is about 12 mm and the ear side is about 18 mm, and increases again.
[0097]
In FIG. 13, at the intersections between the intersection lines L1 to L8 and the intersection line (not shown), the refractive power of the vertical section (hereinafter referred to as vertical refractive power) is the near center A, the intersection points E1 to E4, the weakness center B, and the intensity. As the distance from the center C to the nose side and the ear side increases, the value hardly changes and becomes a substantially constant value.
[0098]
In the lens 1 configured as described above, not only the same effects as in the first embodiment but also the center reference lines S1 and S2 are displaced to the nose side, and the astigmatism on the ear side in the horizontal direction of each refractive surface 2a. By making the aberration distribution change more slowly than the distribution of astigmatism on the nasal side, the following effects can be obtained.
[0099]
As shown in FIG. 14, when a short distance object is viewed laterally with both eyes, the amount of movement α1 of the right eyeball ER toward the ear is larger than the amount of movement of the left eyeball EL toward the nasal side α2. Is known to grow. According to the present embodiment, since the distribution of astigmatism on the ear side is slow, it is possible to perform good binocular side-viewing with little image fluctuation in the slow region.
[0100]
Further, the central reference line S2 is displaced away from the meridian T toward the nose side, and the intensity center C is provided on the central reference line S2, so that the intensity center C is always the nose. It is displaced to the side. Therefore, when the lens 1 is put into the spectacle frame, it is possible to save the trouble of rotating the lens 1 by a predetermined angle so that the intensity center C is located on the nose side as in the second embodiment.
[0101]
(Fourth embodiment)
Next, a fourth embodiment will be described. In addition, the same code | symbol is attached | subjected about the structure similar to the said 1st Embodiment.
[0102]
As shown in FIG. 15A, a weakness center B is provided 13 mm above the geometric center O on the central reference line S. An intensity center C is provided 17 mm below the geometric center O on the central reference line S. The near center A is disposed on a central reference line S that is 7 mm downward from the geometric center and has a refractive power of 2.50 D.
[0103]
The weakness center B has a refractive power (in this case, 1.50 D) that is weaker than the refractive power (2.50 D) of the near center A, and the weakness region 3 has almost the same refractive power as the weak refractive power. have. Therefore, an object separated by 0.67 m (= 1 / 1.50 D) can be seen through the weakness center B and the weakness area 3.
[0104]
The intensity center C has a refractive power (3.00D in this case) that is stronger than the refractive power of the near center A, and the intensity region 4 has almost the same refractive power as the strong refractive power. Accordingly, an object separated by 0.33 m (1 / 3.00 D) can be seen through the intensity center C and the intensity region 4.
[0105]
As shown in FIG. 15B, in the present embodiment, the difference in refractive power between the weakness center B and the intensity center C is 1.50D, and the intermediate region 5 has a 1.50D refraction. The force (frequency of change in the lens) increases progressively. Accordingly, in the intermediate region 5, the frequency changes from a weak power of 1.50D to an intensity number of 3.00D, and in the progressive part 6, a person without adjusting power can be seen from 57 cm to 33 cm away. The length of the progressive part 6 in the intermediate region 5 in the vertical direction is 30 mm, and the refractive power gradient in the progressive part 6 is 1.50 D / 30 mm = 0.05 (D / mm). .
[0106]
The horizontal width of the progressive portion 6 is approximately 12 mm and is substantially constant. Strictly speaking, the progressive portion 6 has a maximum width of 12 mm at a position 2 mm below the geometric center O, and a minimum width of 11 mm at the positions of the weakness center A and the intensity center C. Therefore, the maximum width is 1.1 times the minimum width.
[0107]
The quasi-clear viewing area is the maximum horizontal width W of 40 mm at a position 2 mm below the geometric center O._maxAnd a minimum width W of 20 mm at the position of the weakness center A and the strength center C_minhave. Therefore, its maximum width W_maxIs the minimum width W_min2.0 times.
[0108]
In the fourth embodiment, the near center A is disposed 9 mm downward from the wearing point P and 2 mm away from the nose side. By arranging the near center A in this way, when the wearer looks at a nearby object, the line of sight passes through the near center A even if the upper body is bent forward and the line of sight faces downward. Therefore, the wearer can obtain the optimum near vision through the near center A. That is, when the wearer sits on a chair and looks on the desk, the person performs a natural motion of tilting his face forward about 40 degrees and turning his eyes downward about 20 degrees. The line of sight that is about 60 degrees downward by this operation passes through the near center A.
[0109]
The change in frequency increase and decrease in the fourth embodiment is almost the same as the iso frequency curves 101 to 107 shown in FIG. 3 of the first embodiment, and a description thereof will be omitted.
[0110]
As shown in FIG. 16, in the fourth embodiment, the intersection line L4 is arranged 2 mm below the geometric center O and 5 mm above the near center A, and has an intersection point E3 that overlaps the central reference line S. . The intersection line L5 has a near center A on the central reference line S. The other intersection lines L1 to L3 and L6 to L8 have the same intersection as in the first embodiment.
[0111]
As shown in FIG. 17 (a), in the fourth embodiment, the horizontal refractive powers of the intersecting lines L1 to L8 are generally smaller than the horizontal refractive power in the first embodiment shown in FIG. 5 (a). ing. In the lens region above the geometric center O, the horizontal refractive powers of the intersecting lines L1 to L3 increase as the distance from the central reference line S increases in the horizontal direction, as in the first embodiment. Further, in the lens region below the geometric center O, the horizontal refractive power of the intersecting lines L5 to L7 decreases as the distance from the central reference line S increases in the horizontal direction. Further, the increase rate of the horizontal refractive power of the intersection lines L1 to L3 and the decrease rate of the horizontal refractive power of the intersection lines L5 to L7 are substantially the same as in the first embodiment. Accordingly, the horizontal refractive power of the convex surface 2 changes symmetrically above and below the intersection line L4. As a result, astigmatism is prevented from concentrating at the center of the lens that is frequently used, and astigmatism is dispersed in the left and right regions of the upper and lower parts of the lens that are less frequently used, thereby widening the progressive portion 6.
[0112]
As shown in FIG. 17 (b), in the fourth embodiment, the refractive power in the vertical direction at the intersecting lines (not shown) orthogonal to the intersecting lines L1 to L8 is the first embodiment shown in FIG. 5 (b). It is generally smaller than the horizontal refractive power in the form. This perpendicular refractive power shows a substantially constant value in the direction away from the center reference line S, as in the first embodiment. Accordingly, the number of prisms generated in the vertical direction of the lens is reduced, and the feeling of shaking that occurs when the face is swung left and right is reduced.
[0113]
As described in detail above, the lens of the present invention is not only suitable for a person who has little or no adjustment power and is mainly working at a short distance such as a desk work, but is also worn by the following people Useful to do.
[0114]
A person who uses a progressive multifocal lens of the perspective type, but uses a single-focus presbyscope in near work because near vision is difficult.
People who use a single focus presbyopia but have a narrow range of visible distances, so their faces are close to newspapers, etc. when viewing newspapers.
[0115]
It should be noted that the present invention can be embodied as follows, and in that case, the same effect as that of the above embodiment can be obtained.
(1) In the first embodiment, the range of refractive power that can be increased from the weakness center B to the intensity center C is 0.50D to 4.00D, and the preferred range is 1.00 to 2.00D. The optimum range is 1.25D to 1.75D.
[0116]
The increased refractive power (addition power in the lens) is preferably determined in consideration of the fact that even a person who has lost the adjustment power can look over the entire surface of the desk, for example. Further, when the refractive power increasing in the intermediate region 5 is reduced, the astigmatism of the convex surface is reduced, and a wide clear vision region and a semi-clear vision region can be secured, and the distortion aberration is reduced, so that distortion and fluctuation are reduced. Can be small. Further, as the refractive power increases, the range from a far distance to a close distance that can be seen becomes wider. For example, if the near center A is 2.50D and the refractive power is 4.00D, a person with no adjusting power can see an object in the range of 2 to 22 cm.
[0117]
(2) The gradient of the progressive refractive power from the weakness center B to the intensity center C is preferably smaller than that of a conventional progressive multifocal lens, that is, 0.10 (D / mm) or less. The gradient value in a general progressive multifocal lens is in the range of approximately 0.15 to 0.25 (D / mm). This value corresponds to a case where a person who has almost lost adjustment power wears a lens having an addition power of 3.00 D and a length of the progressive portion of 12 to 20 mm. The smaller this gradient is, the more presbyopia correction lens with less astigmatism, distortion and vibration can be obtained. Therefore, for example, when the progressive power is 4.00D, the length of the progressive portion 6 is preferably 40 mm or more.
[0118]
(3) You may change the length of the progressive part 6 to 20 mm or more. At this time, the progressive power is preferably in the range of 1.00D to 2.00D or 1.25D to 1.75D from the viewpoint of reducing the gradient of the progressive power. For example, when the length of the progressive portion 6 is 25 mm and the progressive power is in the range of 1.25D to 1.75D, the gradient of the progressive power is 0.05 to 0.07 (D / mm). Become. Furthermore, the length of the progressive portion 6 may be arbitrarily changed within a range of 14 mm or more and less than 25 mm. In this case, the progressive power is preferably in the range of 0.50D to 1.50D or 0.75 to 1.25D from the viewpoint of reducing the gradient. For example, when the length of the progressive portion 6 is 16 mm and the progressive refractive power is in the range of 0.75D to 1.25D, the gradient is 0.05 to 0.08 (D / mm).
[0119]
(4) In the above embodiment, the maximum width of the semi-clear vision area is set to twice the minimum width, but may be changed to 1.5 times to 3 times. The reason why it is 1.5 times to 3 times is that the balance between the minimum width and the maximum width is taken into consideration. The minimum width of the semi-clear vision region in the intermediate region 5 is required to be at least 12 mm. This is because if the minimum width is narrower than this, the field of view becomes narrow as in the conventional progressive multifocal lens. Therefore, the upper limit of the ratio between the maximum width and the minimum width should be about 3 times. If the magnification is within this range, the semi-clear vision region can be arranged so that the width in the horizontal direction is maximized at the center of the lens 1, that is, in the vicinity of the near center A. Also, the width of the semi-clear vision region may not be a magnification of 1.5 to 3 times, but the maximum width may simply be 10 mm or more larger than the minimum width. Furthermore, the ratio of the maximum width to the minimum width may be 1.3 or less in a range within ± 10 mm in the vertical direction from the geometric center O.
[0120]
(5) The position where the semi-clear vision region shows the maximum width may be set within a range of 5 to 10 mm above and below the geometric center O, preferably 5 to 7 mm above and below, and 5 mm above and below if optimal. This is because the maximum width W_maxThis is because the semi-clear vision region deviates from the frequently used region (intermediate portion 6) when the image is outside the range of 10 mm above and below the geometric center O. At this time, a wide and clear field of view cannot be obtained in that region.
[0121]
(6) In the first embodiment, the wearing point P is set to the 2 mm ear side 4 mm above the near center A, but the displacement of the near center A toward the ear side may be 2.5 to 3 mm. In this way, when the lens 1 is put into the frame, the intensity center C is located on the nose side even if the rotation angle of the lens 1 is made smaller than 2 degrees, for example, 0 degrees (not rotated). Therefore, it can cope with convergence. Further, the wearing point P may be arranged within 2 mm above the geometric center, and is arranged within 15 mm, preferably 13 mm, preferably within 10 mm above the near center A. May be. Thus, by arranging the wearing point P within 15 mm above the near center A, the wearer can move the eyes in the vertical direction between the wearing point P and the near center A without burden. On the contrary, when the wearing point P is arranged at a position exceeding 15 mm above the near center A, a burden is imposed on the movement of the wearer's eyes.
[0122]
(7) The position of the near center A may be arranged between 2 mm and 15 mm below the geometric center O, preferably between 2 mm and 12 mm. If it is within this range, the wearer moves the eyes in the vertical direction without any burden between the arbitrary point near the near center and the near center, and a distance slightly longer than the near distance from the near distance. It becomes possible to see things. On the contrary, if the near center A is disposed beyond 15 mm below the geometric center O, the angle of the eyes when the wearer sees a nearby object becomes large, and it becomes a burden and difficult to use.
[0123]
(8) The weakness center B and the intensity center C may be arbitrarily changed.
(9) In the first embodiment, the lens 1 is framed so that the near center A is positioned 2 mm below the wearing point P and 2 mm on the nose side. You may frame so that the near center A may be located between 4 mm-6 mm.
[0124]
(10) In the third embodiment, the amount of line-of-sight movement when viewing an object at a distance farther from the near point in the upper half of the lens 1 is the same as when viewing an object at a distance closer to the near point in the lower half of the lens 1. It is smaller than the amount of eye movement. Therefore, the distribution of nasal astigmatism in the region above the geometric center O may not be slower than the distribution of nasal astigmatism in the region below. As a result, the amount by which the central reference line S1 is displaced with respect to the meridian T can be reduced. In addition, the region in which the astigmatism distribution is asymmetrical is defined as a region within 15 mm from the central reference line S to the nose side and the ear side, but may be a region within 20.0 mm.
[0125]
(11) In the above embodiments, the lens refracting surface 2 on the convex surface side of the presbyopia correcting lens 1 is embodied, but it may be embodied by a refracting surface on the concave surface side. In this case, the increase / decrease in the refractive power of the intersecting lines L1 to L8 in the first to fourth embodiments is completely opposite.
[0126]
The progressive part in the present invention is defined as follows.
Progressive portion: In the middle region between the weakness region and the strength region, the refractive power gradually increases from the weakness center to the strength center through the near vision center, including the central reference line, and non- This is the portion of the clear vision area where the point aberration is 0.50 D or less.
[0127]
  Can be grasped from the above embodimentTechniqueThe technical idea is described below along with its effects.
  (1)eyeA pair of eyeglasses that have been framed so that the center of near vision is located between 4 mm below and 6 mm above the distance eye point set in the lens shape of the mirror frame. In this way, the performance of the lens can be exhibited sufficiently when worn as spectacles.
[0128]
  (2)The use point was provided at a position displaced by 2.5 mm to 3.0 mm in the direction of the ear when the lens was worn with respect to the near vision center. In this way, it is possible to reduce the rotation angle of the lens or to frame the lens without rotating.
[0129]
【The invention's effect】
  As described above in detail, according to the first aspect of the present invention, when the object is viewed at a long / intermediate distance, the frequency of use is extremely low, and the visual work mainly involving short distance such as desk work or reading is performed. In addition to being able to see an object at a predetermined short distance as well as a person with no adjustment ability, it is possible to easily see an object at a distance slightly closer than the short distance and an object at a short distance. A wide and clear field of view can be obtained when viewing.
Further, the concentration of astigmatism and distortion on the side of the geometric center is reduced, and the side view can be favorably performed at the center of the lens including the geometric center. Further, in the side view in the vicinity of the intensity center, the side face located at a distance slightly longer than the distance when viewing the front from the vicinity of the intensity center can be seen relatively clearly.
[0130]
According to the second aspect of the present invention, the near center is disposed within 2 mm to 15 mm below the geometric center of the lens, so that it is between an arbitrary point near the near center and the near center. In this case, the wearer can move the eyes in the vertical direction without burden, and can see an object at a distance slightly longer than the short distance.
[0131]
In the invention according to claim 3, by arranging the wearing point within 15 mm above the near center, the wearer can move the eyes vertically between the wearing point and the near center without burden. It becomes possible.
[0132]
According to the invention described in claim 4, in addition to the above effect, the gradient of refractive power between the center of weakness and the center of intensity on the center reference line of the intermediate region is relatively small, so that a wide clear vision region. In addition, it is possible to reduce the image shake and distortion when the line of sight is shifted between the weakness center and the intensity center by obtaining a semi-clear vision area.
[0133]
  According to the fifth aspect of the present invention, it is possible to obtain a lens in which the gradient of refractive power does not increase and the image is less shaken or distorted..
[Brief description of the drawings]
FIG. 1 shows a lens for correcting presbyopia in the first embodiment, (a) is an explanatory diagram showing the distribution of astigmatism, and (b) is a graph showing a change in refractive power.
FIG. 2 is an explanatory diagram showing each region of a lens.
FIG. 3 is an explanatory diagram showing a power distribution of a lens.
FIG. 4 is an explanatory diagram showing a plane passing through a geometric center and perpendicular to a central reference line, and a line of intersection between a plane group parallel to the plane and a refracting surface.
5A and 5B show a refractive power distribution of a lens refracting surface, where FIG. 5A is a graph showing the relationship between the horizontal refractive power of each intersection line and the distance from the central reference line, and FIG. 5B is a vertical refractive power and the central reference line; The graph which shows the relationship with the distance from.
FIG. 6 is a distortion diagram of a square lattice viewed through a lens.
FIG. 7 is a front view showing eyeglasses in which the lens of the first embodiment is framed.
8A and 8B show a lens according to a second embodiment, in which FIG. 8A is an explanatory diagram showing the distribution of astigmatism, and FIG. 8B is a graph showing a change in refractive power.
9A and 9B show a refractive power distribution of a lens refracting surface, in which FIG. 9A is a graph showing a relationship between a horizontal refractive power of each intersection line and a distance from a central reference line, and FIG. 9B is a vertical refractive power and a central reference line; The graph which shows the relationship with the distance from.
FIG. 10 is an explanatory diagram showing the distribution of astigmatism of the lens of the third embodiment.
FIG. 11 is an explanatory diagram showing a plane passing through the geometric center and perpendicular to the central reference line, and a line of intersection between a plane group parallel to the plane and the refractive surface.
FIG. 12 is a graph showing the relationship between the horizontal refractive power and the distance from the center reference line.
FIG. 13 is a graph showing the relationship between the vertical refractive power and the distance from the center reference line.
FIG. 14 is a schematic diagram showing the amount of movement of the eyeball when moving the line of sight to the side.
15A and 15B show a lens for correcting presbyopia in the fourth embodiment, wherein FIG. 15A is an explanatory diagram showing the distribution of astigmatism, and FIG. 15B is a graph showing a change in refractive power.
FIG. 16 is an explanatory diagram showing a plane passing through the geometric center and perpendicular to the central reference line, and a line of intersection between a plane group parallel to the plane and the refractive surface.
FIG. 17 shows the refractive power distribution of the lens refracting surface, (a) is a graph showing the relationship between the horizontal refractive power of each intersection line and the distance from the central reference line, and (b) is the vertical refractive power and the central reference line. The graph which shows the relationship with the distance from.
18A and 18B show a progressive multifocal lens in a conventional example, where FIG. 18A is an explanatory diagram showing each region, and FIG. 18B is a graph showing a change in refractive power.
FIG. 19 is an explanatory diagram showing a distribution of astigmatism of a progressive multifocal lens of a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lens for presbyopia correction, 2 ... Lens refracting surface, 3 ... Weak area, 4 ... Intensity area, 5 ... Middle area, S ... Center reference line, A ... Near center, B ... Center of weakness, C ... center of intensity, O ... geometric center, P ... wearing point, L1 to L4 ... intersection line (first intersection line), L5 to L8 ... intersection line (second intersection line), E1 to E5 ... intersection point.

Claims (5)

In at least one lens refracting surface of the two lens refracting surface of the lens, a center reference line dividing the lens refractive surface in the left-right extending as astigmatism is minimized in the vertical direction of the lens refractive surface ,
A near center provided on the central reference line;
A weakness center which is provided on the central reference line and above the near center, and gives a refractive power weaker than the refractive power of the near center;
An intensity center which is provided on the central reference line and below the near center and gives a refractive power stronger than the refractive power of the near center;
Provided between the weakness center and the intensity center, and an increasing region in which a predetermined refractive power gradually increases from the weakness center to the intensity center through the near center,
A difference in refractive power between the weakness center and the intensity center is in the range of 0.50D to 4.00D;
In the increasing region, n is the refractive index of the lens material, C1, C2 is a principal curvature in a different direction at a point on the lens refractive surface (unit is m ⁻¹ ),
(N-1) × | C1−C2 | ≦ 0.5 (m ⁻¹ )
The clear vision area defined by the conditions of
(N-1) × | C1−C2 | ≦ 0.75 (m ⁻¹ )
Having a semi-clear viewing area defined by the conditions of
The horizontal width of the clear vision region in the increased region is maximized at a position near the geometric center of the lens, or substantially constant from the weakness center to the intensity center through the near vision center. , and the horizontal width of the quasi-clear vision area in the increase area, Ri up der in vicinity of the geometric center,
In the region above the geometric center, a plane passing through the geometric center and perpendicular to the central reference line is assumed, and a first intersection line between a plane parallel to the plane and the lens refracting surface is the center. It is a non-circular curve whose curvature increases with increasing distance from the intersection of the reference lines,
In the region below the geometric center, a plane passing through the geometric center and perpendicular to the central reference line is assumed, and a second intersection line between the plane parallel to the plane and the lens refractive surface is the center. It is a non-circular curve whose curvature decreases with increasing distance from the intersection of the reference lines,
Assuming a horizontal line passing through the vicinity of the geometric center, the distance in the upper region and the lower region from the horizontal line is equal, and the distance in the upper region and the lower region from the central reference line is equal A presbyopia correcting lens , wherein an increasing rate of curvature of the first intersection line passing through each of the two points is substantially equal to a decreasing rate of curvature of the second intersection line .   The presbyopia correcting lens according to claim 1, wherein the near vision center is disposed within 2 mm to 15 mm below the geometric center of the lens.   The lens for correcting presbyopia according to claim 1 or 2, further comprising a wearing point disposed within 15 mm above the near center.   The lens for presbyopia correction according to any one of claims 1 to 3, wherein a length in the vertical direction in the increased region is 20 mm or more, and between the weakness center and the strength center. A lens for correcting presbyopia, wherein the difference in refractive power is in the range of 1.00D to 2.00D. The lens for correcting presbyopia according to any one of claims 1 to 3, wherein a vertical length of the increased region is not less than 14 mm and less than 25 mm, and is between the weakness center and the strength center. The lens for correcting presbyopia is characterized in that the difference in refractive power is in the range of 0.50D to 1.50D .

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