Method for determining progressive addition lens

Abstract

A method for specifying a progressive addition lens, the method comprising: a determination step for determining the degree of necessity for the size of a clear field of view region for a subject wearing a progressive addition lens; when it is determined that the subject needs to enlarge the clear field of view in the left-right direction, a design selection step is performed by smoothing the power distribution of the progressive multifocal lens in the left-right direction to reduce the third aberration in the left-right direction around the principal meridian of the progressive multifocal lens and to increase the clear field of view in the left-right direction. And the design of the progressive multi-focus lens enlarges the clear visual field area in the left-right direction.

Description

Technical Field

[0001] The present invention relates to a method for determining an aspheric progressive addition lens. Background Art

[0002] In Patent Documents 1 and 2, an aspheric progressive addition lens is disclosed, which adds a transmitted astigmatism to the near vision area and the intermediate vision area among the distance vision area, the near vision area, and the intermediate vision area. In the near vision area and the intermediate vision area where the transmitted astigmatism is added, there is a portion where, after subtracting the refractive power for astigmatism correction, the amount of the refractive power in the horizontal direction is greater than the amount of the refractive power in the vertical direction (or the amount of the refractive power in the vertical direction is greater than the amount of the refractive power in the horizontal direction).

[0003] In addition, in Patent Document 3, an ophthalmic prescription assisting device is disclosed, which has: an acquisition unit that acquires first distribution data and second distribution data, the first distribution data being measurement data of a subject's eye based on a wavefront sensor and related to the distribution of the refractive error of the subject's eye, and the second distribution data being the refractive power distribution of an ophthalmic lens for correcting the refractive error of the subject's eye, which is measurement data of a part of the measurement data related to the refractive power distribution of the ophthalmic lens measured by a lensometer; and an arithmetic unit that obtains third distribution data related to the distribution of the refractive error considering the correction by the ophthalmic lens based on the first distribution data and the second distribution data acquired by the acquisition unit.

[0004] In addition, in Patent Document 4, a method for determining a person's visual behavior is disclosed, which is characterized by including a step of recording the head movement of a person during the execution of a visual task, and further including a step of recording at least one eye movement of the person during the execution of the visual task, a step of determining the relative orientation of the eye with respect to the head at different time points, and a step of determining the amount of time the eye stays in each orientation.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: WO 2020 / 067522

[0008] Patent Document 2: WO 2020 / 067523

[0009] Patent Document 3: Japanese Patent No. 6708955

[0010] Patent Document 4: Japanese Patent No. 4659027 Summary of the Invention

[0011] Technical Problem to be Solved by the Invention

[0012] An object of an embodiment of the present invention is to provide a technique for determining a progressive multifocal lens that can be worn more comfortably by a subject who needs to expand a clear vision area in the left and right directions.

[0013] Technical solution for solving technical problems

[0014] A first aspect of the present invention is a method for determining a progressive multifocal lens, which includes: a determination step of determining the necessity of the size of a clear vision area for a subject wearing a progressive multifocal lens; a design selection step of, when it is determined that the subject needs to expand the clear vision area in the left and right directions, selecting a design of a progressive multifocal lens in which the power distribution of the progressive multifocal lens is smoothed in the left and right directions, the lateral coma in the left and right directions around the principal meridians of the progressive multifocal lens is reduced, and the clear vision area is expanded in the left and right directions.

[0015] A second aspect of the present invention, according to the method for determining a progressive multifocal lens of the first aspect, in the determination step, based on the amount of lateral coma of the subject's eyes in the left and right directions, the necessity of the size of the clear vision area is determined.

[0016] A third aspect of the present invention, according to the method for determining a progressive multifocal lens of the first aspect, in the determination step, based on the change in the subject's eye movement when the subject repeatedly performs near vision and far vision observations, the necessity of the size of the clear vision area is determined.

[0017] A fourth aspect of the present invention, according to the method for determining a progressive multifocal lens of the first aspect, in the determination step, based on the subject's sensitivity to aberration, the necessity of the size of the clear vision area is determined.

[0018] A fifth aspect of the present invention, according to the method for determining a progressive multifocal lens of the first aspect, the width of a smoothing filter for smoothing the power distribution in the left and right directions is greater than the narrowest width among the widths between the peaks of the lateral coma on both sides in the left and right directions located on the principal meridian of the progressive multifocal lens before smoothing.

[0019] A sixth aspect of the present invention, according to the method for determining a progressive multifocal lens of the first aspect, in the design selection step, a design of a progressive multifocal lens with an expanded clear vision area in the left and right directions is selected instead of increasing the astigmatism amount of the progressive multifocal lens on the principal meridian.

[0020] A seventh aspect of the present invention, according to the method for determining a progressive multifocal lens of the first aspect, in the design selection step, a design of a progressive multifocal lens with an expanded clear vision area in the left and right directions without changing the add power curve of the principal meridian is selected.

[0021] In the eighth aspect of the present invention, in the method for determining an aspheric progressive addition lens according to any one of the first to seventh aspects, when it is determined in the determination step that the subject does not need to expand the clear vision area in the left-right direction, in the design selection step, the basic design of the aspheric progressive addition lens is selected.

[0022] Advantages of the Invention

[0023] According to an embodiment of the present invention, it is possible to determine an aspheric progressive addition lens that can be worn more comfortably for a subject who needs to expand the clear vision area in the left-right direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1A FIG. is an example of a clear vision area when a subject wearing an aspheric progressive addition lens makes a near vision observation, and is an example of a clear vision area in a state without eye aberration.

[0025] Figure 1B FIG. is an example of a clear vision area when a subject wearing an aspheric progressive addition lens makes a near vision observation, and is an example of a clear vision area in a state where the eye has a clover aberration (Z[-3,3]) in the left-right direction.

[0026] Figure 2 FIG. is a flowchart showing an example of the method for determining an aspheric progressive addition lens according to the first embodiment of the present invention.

[0027] Figure 3 FIG. is a schematic diagram for explaining the line-of-sight movement task according to the first embodiment of the present invention.

[0028] Figure 4 FIG. is an example of an original image and a plurality of blurred images according to the first embodiment of the present invention.

[0029] Figure 5 FIG. is an example of a spot image formed by an aberration added to a blurred image according to the first embodiment of the present invention.

[0030] Figure 6A FIG. is a left-right direction power distribution diagram of the near vision area of the aspheric progressive addition lens (for left eye) according to the first embodiment of the present invention.

[0031] Figure 6B is Figure 6A gradient distribution diagram of

[0032] Figure 7 FIG. is a diagram showing the power distribution (Power), astigmatism distribution (As), and left-right direction third-order aberration distribution (HOA, Higher Order Aberration) of the basic design of the aspheric progressive addition lens according to an embodiment of the present invention.

[0033] Figure 8 These are graphs showing the power distribution (Power), astigmatism distribution (As), and higher-order aberration distribution in the left-right direction (HOA, Higher Order Aberration) of the design that smoothens the power distribution of the progressive multifocal lens only in the left-right direction in the embodiments of the present invention.

[0034] Figure 9A This is a graph showing the clear vision area when a subject wearing a progressive multifocal lens of the basic design observes closely. The left side is a graph of the state where the eye has no aberration, and the right side is a graph of the state where the eye has a trefoil aberration of 0.1 μm in the rightward direction.

[0035] Figure 9B This is a graph showing the clear vision area when a subject wearing a progressive multifocal lens with a left-right expansion design in the embodiments of the present invention observes closely. The left side is a graph of the state where the eye has no aberration, and the right side is a graph of the state where the eye has a trefoil aberration of 0.1 μm in the rightward direction.

[0036] Figure 10A This is a graph showing an example of a bimodal light spot (left in the figure) and a blurred image formed by folding the light spot (right in the figure).

[0037] Figure 10B This is a graph showing an example of a unimodal light spot (left in the figure) and a blurred image formed by folding the light spot (right in the figure). Detailed implementation mode

[0038] <Insights obtained by the inventor>

[0039] First, the insights obtained by the inventor will be described. Figure 1A And Figure 1B These are graphs showing an example of the area where a subject wearing a progressive multifocal lens can at least distinguish the direction of a Landolt ring target with a visual acuity of 0.7 or the area where the edge of a Landolt ring target with a visual acuity of 0.3 is clearly visible (hereinafter referred to as the clear vision area) when observing closely. In Figure 1A And Figure 1B Taking the left eye L of the subject as a reference, the vertical axis represents the front-back direction (the direction of the radius vector R in the polar coordinate system), and the horizontal axis represents the left-right direction. In addition, the area surrounded by the dotted line is the clear vision area of the left eye L, and the area surrounded by the solid line is the clear vision area of the right eye R. The overlapping range of the two becomes the clear vision area of both eyes. Hereinafter, in this specification, unless otherwise specified, the "clear vision area" refers to the clear vision area of both eyes. Figure 1A This is a graph showing the clear vision area in the state where the eye has no aberration, Figure 1BThis is an example of a clear vision area in a state where the eye has a clover aberration (Z[-3,3]) with third-order aberration in the left-right direction. As Figure 1B shown, it can be seen that when the eye has a clover aberration, the clear vision areas on the left and right are shifted, and the clear vision areas of both eyes become narrower. Since the aberration of the eye varies depending on individual differences or conditions, in a state where the clear vision area is narrowed, it is possible that the subject cannot comfortably wear progressive multifocal lenses.

[0040] The present inventor has conducted in-depth research on the above problems. As a result, there are subjects who are not troubled even in a state where the clear vision area is narrowed. On the other hand, there are also subjects who cannot comfortably wear progressive multifocal lenses even when the clear vision area is not narrowed. Therefore, the following method has been found: an index of how much size of the clear vision area the subject needs (that is, whether the size of the clear vision area of the basic design of the progressive multifocal lens is sufficient, or it is better to expand in the left-right direction) is determined as the necessary degree of the size of the clear vision area. For example, for a subject determined to need to expand the clear vision area in the left-right direction, a progressive multifocal lens design is selected that expands the clear vision area in the left-right direction by smoothing the power distribution of the progressive multifocal lens in the left-right direction and reducing the third-order aberration in the left-right direction around the principal meridians of the progressive multifocal lens. In addition, there are multiple methods (parameters) for determining the necessary degree of the size of the clear vision area, which will be described in detail later. According to this method, it is possible to determine a progressive multifocal lens that can be worn more comfortably for a subject who needs to expand the clear vision area in the left-right direction with a minimum risk (that is, maintaining the basic design of the progressive multifocal lens as much as possible).

[0041] In addition, in this specification, the basic design of the progressive multifocal lens refers to the design of the lens temporarily selected (or worn) by the subject, or the design temporarily recommended by the seller, etc., which becomes the basic design of the progressive multifocal lens for the subject.

[0042] In addition, the third-order aberration (including clover aberration and coma) of the progressive multifocal lens is generated in a manner surrounding the principal meridians (in the direction toward the principal meridians) near the near vision area. When it is more than 0.1 μm larger than the position where the absolute value of the third-order aberration in the left-right direction near the principal meridians is the smallest, the subject feels difficult to observe at close range (for example, the direction of the Landolt ring chart with a visual acuity of 0.7 is unclear, or the edge of the Landolt ring chart with a visual acuity of 0.3 is unclear). Therefore, in this specification, the clear vision area can also be renamed as the area that is more than 0.1 μm larger than the position where the absolute value of the third-order aberration in the left-right direction near the principal meridians is the smallest.

[0043] [Details of the Embodiment of the Present Invention]

[0044] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention is not limited to these examples, and as indicated by the claims, it is intended to include all changes within the meaning equivalent to the claims and the scope thereof.

[0045] <First Embodiment of the Present Invention>

[0046] (1) Method for Determining Eyeglass Lenses

[0047] First, a method for determining an aspheric progressive addition lens according to this embodiment will be described. Figure 2 is a flowchart showing an example of a method for determining an aspheric progressive addition lens according to this embodiment. As Figure 2 shown, the method for determining an aspheric progressive addition lens according to this embodiment, for example, has a necessary degree determination step S101 of a clear vision area and a design selection step S102. In this embodiment, a case will be described in which either a design (left - right expansion design) in which the clear vision area is expanded in the left - right direction or a basic design is selected to determine a more suitable aspheric progressive addition lens for the subject.

[0048] (Necessary Degree Judgment Step S101 of Clear Vision Area)

[0049] The necessary degree determination step S101 of the clear vision area is a step of determining the necessary degree of the size of the clear vision area for a subject wearing an aspheric progressive addition lens (applied with the basic design). There are multiple methods (parameters) for determining the necessary degree of the size of the clear vision area. One example will be described below.

[0050] In the necessary degree determination step S101 of the clear vision area, for example, the necessary degree of the size of the clear vision area can also be determined based on the amount of coma aberration in the left - right direction of the subject's eyes. As Figure 1B shown, when the eyes have coma aberration (clover aberration), the clear vision area becomes narrower. Therefore, a subject with a large amount of coma aberration in the left - right direction of the eyes (the absolute value of the difference between the left and right, for example, 0.1 μm or more) can also be determined to require an expansion of the clear vision area in the left - right direction. In addition, in the case of a subject with dry eye or the like, the clover aberration of the eyes tends to increase, so for example, the measured value of the coma aberration amount can be adjusted considering the subject's constitution. In addition, in order to measure the amount of coma aberration of the subject's eyes, a known technique such as a wavefront sensor can be used.

[0051] However, since the amount of coma aberration of the eyes varies greatly depending on the subject's state and the surrounding environment, it is preferable to also consider other parameters to determine the necessary degree of the size of the clear vision area. Below, other parameters for determining the necessary degree of the size of the clear vision area will be described.

[0052] In the necessary degree determination step S101 of the clear vision area, for example, the necessary degree of the size of the clear vision area can also be determined based on the change in the subject's eye movement when the subject repeatedly performs near vision and far vision. Figure 3 It is a schematic diagram illustrating a task (hereinafter referred to as the eye movement task) for determining the necessary degree of the size of the clear vision area based on the change in the subject's eye movement. As Figure 3 shown, in the eye movement task, the subject 10 repeatedly (for example, alternately) visually confirms the near vision target 20 arranged nearby (for example, the viewing distance dS = 40 cm) and the far vision target 30 arranged far away (for example, the viewing distance dL = 3 m). As the near vision target 20 and the far vision target 30, for example, the Landolt rings with a visual acuity of 0.7 displayed on a display terminal such as a tablet computer can be used.

[0053] When the subject can clearly visually recognize the near vision target and the subject's eye movement is small (for example, corresponding to the situation of reading a book in real life), the size of the clear vision area is not much of a problem. However, for example, when the subject's line of sight moves significantly from the state of visually recognizing the far vision target to the near vision target (for example, corresponding to the situation of moving the line of sight from the state of watching TV to a book beside in real life), if the clear vision area is narrow, there are subjects who feel it difficult to focus on the near vision target. Specifically, subjects who are not used to using progressive multifocal lenses and use various locations on the lens when visually recognizing the near vision target (that is, the deviation of the head movement amount and the convergence amount is large), subjects whose time (response time) to clearly visually recognize the near vision target becomes long, etc. meet the criteria. Therefore, it can be determined that for subjects who perform the eye movement task and have a large deviation in the head movement amount and the convergence amount (especially, a large deviation when transitioning from far vision to near vision), for example, need to expand the clear vision area in the left and right directions. In addition, it can also be determined that for subjects who perform the eye movement task and have a long (or large deviation) time (response time) to clearly visually recognize the near vision target when transitioning from far vision to near vision, for example, need to expand the clear vision area in the left and right directions. In addition, in the eye movement task, when measuring the subject's head movement amount and convergence amount, for example, a camera equipped with a display device for displaying the near vision target can be used to photograph the subject's head and eyes, and the head movement amount and convergence amount can be measured through image recognition.

[0054] In addition, in the determination step S101 of the necessity level of the clear vision area, for example, the necessity level of the size of the clear vision area may be determined based on the sensitivity of the subject to the aberration. In the design selection step S102 described later, in the case of selecting a design of a progressive multifocal lens with an expanded clear vision area in the left-right direction, the amount of astigmatism on the principal meridian increases compared to the basic design. That is, as the cost of expanding the clear vision area in the left-right direction, the quality (image quality) on the principal meridian decreases compared to the basic design. Therefore, for a subject who can sensitively feel the increase in the amount of astigmatism on the principal meridian, there is a possibility of comfortably wearing a progressive multifocal lens that maintains the basic design without expanding the clear vision area in the left-right direction. On the other hand, for a subject who does not feel the increase in the amount of astigmatism on the principal meridian, there is a possibility of comfortably wearing a progressive multifocal lens with a left-right expanded design.

[0055] An example of a method for measuring the sensitivity of a subject to aberration will be described. To measure the sensitivity to aberration, for example, a plurality of blurred images (two blurred images in this embodiment) obtained by changing the amount of aberration (preferably, only this amount) to be added to a specified original image can be used. Figure 4 An example of the original image and a plurality of blurred images is shown. In Figure 4 it shows a blurred image 40A obtained by adding a specified amount of aberration to the original image 40 and a blurred image 40B with a larger amount of added aberration than the blurred image 40A.

[0056] Figure 5 is an example of a spot image formed by the aberration added to the blurred image. In Figure 5 it shows a spot image trailing in the lower left of the paper surface. The blurred image to which the aberration forming such a spot image is added is faintly visible in the lower left. In other words, due to the added aberration, the spatial frequency characteristics in the lower left direction are significantly (characteristically) reduced. In this specification, the characteristic direction of the reduction in the spatial frequency characteristics caused by the added aberration is referred to as the direction of the aberration.

[0057] Preferably, the directions of the aberrations added to a plurality of blurred images (for example, the blurred image 40A and the blurred image 40B) are substantially the same. Thereby, it is easy for the subject to compare the appearances of the plurality of blurred images. In addition, in this specification, the so-called substantially the same direction of the aberration includes not only the case where the directions are exactly the same but also the case where there is a slight difference of ±15 degrees or less in the directions of the aberrations. In addition, the direction of the aberration means the direction of the component with the largest absolute value among all the coefficients of all the blurred images when the aberrations added to the simultaneously displayed blurred images are respectively expanded by Zernike polynomials.

[0058] In addition, when selecting the aberration to be added to the original image 40, for example, it can be arbitrarily selected from the aberrations generated by standard progressive multifocal lenses.

[0059] After preparing a plurality of blurred images, the sensitivity of the subject to the aberration can be measured by simultaneously presenting the plurality of blurred images to the subject and comparing the appearances to obtain the subjective response of the subject. Specifically, for example, the blurred image 40A and the blurred image 40B shown as Figure 4 are presented simultaneously and the appearances are compared, and a task of selecting which one of the blurred image 40A and the blurred image 40B (or "unknown") can be clearly viewed (hereinafter referred to as the aberration sensitivity task) is performed. Then, in the case where the blurred image 40A with a small amount of added aberration (i.e., correct) is selected, it can be determined that the sensitivity to blur is high, and in the case where the blurred image 40B with a large amount of added aberration (i.e., incorrect) is selected, it can be determined that the sensitivity to blur is low. It should be noted that in this specification, simultaneously presenting a plurality of blurred images means presenting a plurality of blurred images in a manner that allows visual recognition in a state where a plurality of blurred images exist in the subject's visual field, and does not limit the start or end time of the presentation of each blurred image (for example, the start or end time of the presentation can be offset between the blurred image 40A and the blurred image 40B).

[0060] However, in the case of determining the sensitivity to blur through a single subjective response, for example, there is also a possibility that it includes a case where even if the appearance difference (difference) is not actually known, the blurred image with a small amount of aberration is occasionally selected. Therefore, in the present embodiment, it is preferable to further prepare a plurality of similar blurred images similar to the plurality of blurred images, simultaneously present the plurality of similar blurred images to the subject, that is, a plurality of similar blurred images in which the amount of added aberration (preferably only the amount of this aberration) is changed, and compare the appearances to obtain the subjective response of the subject multiple times, thereby measuring the stability of the subjective response. In addition, the similar blurred images are, for example, images obtained by rotating the blurred image by an arbitrary angle, or images obtained by enlarging or reducing the blurred image at an arbitrary magnification.

[0061] For a subject who performs the above-described aberration sensitivity task and is determined to have a high sensitivity to blur, it can also be determined that there is no need to expand the clear vision area in the left-right direction (or the possibility that the disadvantages of selecting the left-right expansion design exceed the advantages is high). In addition, for a subject who is determined to have a low sensitivity to blur, it can also be determined that there is a need to expand the clear vision area in the left-right direction (or the possibility that the advantages of selecting the left-right expansion design exceed the disadvantages is high).

[0062] In addition, the aberration sensitivity task can also be performed multiple times. For stable and correct subjects, it is determined that they have a high sensitivity to blurring, and in the design selection process S102, a design with low aberration is selected. In addition, for stable and incorrect subjects, it can also be determined that they have a high sensitivity to blurring but prefer a state with a large aberration, and in the design selection process S102, a design with the aberration preferred by the subject is selected. In addition, it can also be that for subjects with few unclear responses regarding correct or incorrect answers and instability, it is determined that they have a low sensitivity to blurring but do not consciously recognize it as low sensitivity, and in the design selection process S102, a balanced design is selected between a design with low aberration and a design that improves other designs (for example, a design that expands the clear vision area in the left-right direction). In addition, for subjects with many unclear responses, it can also be determined that they have a low sensitivity to blurring, and an improved design that trades off with aberration (for example, a design that expands the clear vision area in the left-right direction) is selected.

[0063] In addition, as a result of further research by the present inventor, it was found that subjects do not determine the visibility of an image solely based on the simple magnitude of blurring (or the amount of aberration causing blurring) or MTF (Modulation Transfer Function). Specific examples are as Figure 10A and Figure 10B shown. In Figure 10A and Figure 10B , on the right side of the figure, a blurred image with blurring (also called a convolved spot) corresponding to the spot shown on the left side of the figure is shown. Figure 10A The spot shown in Figure 10B has a smaller degree of spot expansion (i.e., a smaller sum of the squares of the aberration amounts) compared to the spot shown in Figure 10B , but has bimodality. On the other hand, the spot shown in Figure 10A and Figure 10B has a slightly larger degree of spot expansion but is unimodal. When the blurred images shown in Figure 10A and Figure 10B are presented to a specific group and a question of comparing appearances is posed, the blurred image in Figure 10A has clear lines but is double, and thus, most subjects answer Figure 10BThe blurred images among them are relatively preferred. It is considered that this is because there are almost no subjects who prefer bimodal blur. Therefore, in the aberration sensitivity task, it is also possible to compare a blurred image obtained by convolving a spot with a slightly smaller aberration amount but multimodality (including bimodality equivalent to astigmatism + spherical aberration of the eye, trimodality equivalent to trefoil aberration + spherical aberration of the eye, and quadrimodality of higher-order aberration of the eye) with a blurred image obtained by convolving a spot with a slightly larger aberration amount but unimodality. A subject who prefers the blurred image obtained by convolving a unimodal spot is determined to be highly sensitive to blur. Here, "high sensitivity to blur" means being more sensitive to whether the aberration correction is correctly performed than to the magnitude of the aberration.

[0064] In the aberration sensitivity task, it is also possible to score based on whether the subjective response of the subject is consistent with the average support in the group, and determine the sensitivity of the subject to blur based on this score. The average support can use the statistical value when a certain group is questioned in advance, or can be estimated by machine learning, etc. Specifically, for example, in the problem of comparing blurred images on the left and right, when there are more subjects (higher support rate) who prefer the blurred image on the left, for a subject who answers that the image on the left is preferred, it is set as +1 point, etc., as being consistent with the average support in the group, and for a subject who answers that the image on the right is preferred, it is set as -1 point, etc., as being inconsistent with the average support in the group. Then, the total score and the subtotal of each question tendency are statistically calculated. For example, when it is above a specified score (threshold), it is determined that the sensitivity to blur is high, and when it is less than the specified score (threshold), it is determined that the sensitivity to blur is low. That is to say, it is also possible to determine the sensitivity of the subject to blur based on the size relationship between the score and a predetermined threshold. By scoring in this way, it is possible to make a determination considering not only the simple magnitudes of the aberration amount and MTF, but also the subject's preference for blur (the tendency and degree of blur that the subject can allow). In addition, since the characteristics of the subject are easy to understand, it is easy to conduct consultations when determining spectacle lenses.

[0065] In addition, it is also possible to combine the above various parameters to determine the necessity degree of the clear vision area size. For example, in the clear vision area necessity degree determination step S101, it is also possible to determine the necessity degree of the clear vision area size based on at least one (preferably two, more preferably three) of the third-order aberration amount in the left-right direction of the subject's eyes, the change in the subject's eye movement when the subject repeatedly performs near-distance observation and far-distance observation, and the subject's sensitivity to aberration.

[0066] (Design selection step S102)

[0067] In the design selection process S102, for example, when it is determined in the clear vision area necessity determination process S101 that the subject needs to expand the clear vision area in the left and right directions, a design of a progressive multifocal lens is selected in which the power distribution of the progressive multifocal lens is smoothed in the left and right directions, the lateral coma aberration in the left and right directions around the principal meridians of the progressive multifocal lens is reduced, and the clear vision area is expanded in the left and right directions. Thus, it is possible to determine a progressive multifocal lens that can be worn more comfortably for a subject who needs to expand the clear vision area in the left and right directions. In addition, in the design selection process S102, for example, a lens suitable for the subject's design may also be selected from among a plurality of pre-prepared customized lenses.

[0068] A more specific description will be given of the design of a progressive multifocal lens (left and right expansion design) in which the clear vision area is expanded in the left and right directions. Figure 6A is a lateral power distribution diagram of the near vision area of a progressive multifocal lens (for the left eye), Figure 6B and is Figure 6A the gradient distribution diagram. In addition, the sum value of the coma aberration and trefoil aberration in the 0-degree direction is in a proportional relationship with this slope distribution. As Figure 6A shown, relative to the basic design (dashed line), in the left and right expansion design (solid line), by applying a smoothing filter (such as a Gaussian filter) in the left and right directions, the power distribution around the principal meridian P is smoothed. In addition, when the power of the principal meridian is reduced due to smoothing, by shifting the reduction amount in the concave direction, the power of the principal meridian can be adjusted to be the same as (or at the same level as) the basic design. As Figure 6B shown, by smoothing the power distribution in the left and right directions, the lateral coma aberration distribution in the left and right directions also becomes gentle, so that the clear vision area (for example, the area where the amount of coma aberration around the principal meridian P is within ±0.1 μm) is expanded in the left and right directions. By selecting such a left and right expansion design, for a subject who needs to expand the clear vision area in the left and right directions, it is possible to determine a progressive multifocal lens that can be worn more comfortably with a minimum risk (that is, maintaining the basic design of the progressive multifocal lens as much as possible).

[0069] The width of the smoothing filter for smoothing the power distribution of the progressive multifocal lens in the left and right directions is preferably greater than the narrowest width among the widths between the peaks of the lateral coma aberration on both sides of the principal meridian in the progressive multifocal lens before smoothing. Thereby, the coma aberration can be effectively reduced.

[0070] As described above, by smoothing the power distribution of the progressive multifocal lens only in the left-right direction, there are advantages of reducing the third-order aberration in the left-right direction at the periphery of the principal meridians of the progressive multifocal lens and expanding the clear vision area in the left-right direction. On the other hand, compared with the basic design, there is also a disadvantage that the amount of astigmatism on the principal meridian increases. Therefore, in the design selection process S102, it is also possible to select the design of the progressive multifocal lens with an expanded clear vision area in the left-right direction instead of the increase in the amount of astigmatism on the principal meridian of the progressive multifocal lens.

[0071] In the design selection process S102, it is preferable to select the design of the progressive multifocal lens that does not change the add power curve of the principal meridian and only smooths the power distribution in the left-right direction while expanding the clear vision area in the left-right direction. Thereby, it is possible to reduce the increase in aberration in the up-down direction, maintain the basic design of the progressive multifocal lens as much as possible, and expand the clear vision area in the left-right direction.

[0072] In addition, in the clear vision area necessity determination process S101, when it is determined that the subject does not need to expand the clear vision area in the left-right direction (or the possibility that the disadvantages of selecting the left-right expansion design exceed the advantages is high), it is also possible not to select the left-right expansion design but to select the basic design of the progressive multifocal lens. Thereby, it is possible to provide a progressive multifocal lens with optimized quality (image quality) on the principal meridian to subjects who do not need to expand the clear vision area in the left-right direction.

[0073] By applying the method described above to multiple subjects, it is possible to provide a design of a progressive multifocal lens suitable for the needs of each subject.

[0074] <Other Embodiments of the Present Invention>

[0075] As described above, the embodiments of the present invention have been specifically described, but the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist thereof.

[0076] For example, in the above embodiments, a method for determining a progressive multifocal lens has been described, but the present invention can also be used as a method for determining the necessity of the size of the clear vision area. In this case, it is also possible to perform only the clear vision area necessity determination process S101 and omit the design selection process S102.

[0077] In addition, for example, in the above embodiments, the case of selecting either the left-right expansion design or the basic design has been described, but the left-right expansion design is not limited to one, and it is also possible to select from multiple variations (for example, different sizes of the clear vision area in the left-right direction).

[0078] In addition, for example, in the above-described embodiments, design choices corresponding to the third-order aberrations of the eyeball were described. However, in addition to this, design choices can also be made based on (or considering) the degree of fixation deviation and the degree of deviation between the line of sight and the visual axis of the eye. This is because the horizontal third-order aberration component is added to or subtracted from the measured ocular aberration according to the degree of the above-mentioned deviation. In addition, in addition to the degree of the above-mentioned deviation, factors eccentric in the horizontal direction from the standard model in design or measurement also become factors causing changes in the third-order aberration amount. Therefore, they are preferably used for the judgment of design choices.

[0079] [Embodiment]

[0080] Next, embodiments of the present invention will be described. These embodiments are examples of the present invention, and the present invention is not limited to these embodiments.

[0081] (Step S101 for Judging the Necessity Degree of the Clear Vision Area)

[0082] In this embodiment, the above-described line-of-sight movement task is performed, and the necessity degree of the size of the clear vision area is determined based on the progress of the subject's line-of-sight movement. Specifically, as Figure 3 shown, a near target 20 (Landolt ring with a visual acuity of 0.7 displayed on a smartphone) is arranged at a position 30 degrees below the subject 10 and at a viewing distance dS = 40 cm, and a far target 30 (Landolt ring with a visual acuity of 0.7 displayed on a tablet terminal) is arranged in front of the subject 10 at a viewing distance dL = 3 m. Then, the near target 20 and the far target 30 are alternately displayed a total of 30 times, and the subject 10 is asked to visually confirm and answer the notch of the Landolt ring.

[0083] In this embodiment, when the deviation of the subject's head movement amount and the convergence amount during the line-of-sight movement task is large, or when the response time is long (or the deviation is large), it is determined that the subject needs to expand the clear vision area in the left-right direction. Otherwise, it is determined that the subject does not need to expand the clear vision area in the left-right direction.

[0084] (Design Selection Step S102)

[0085] Figure 7 is a diagram showing the power distribution (Power), astigmatism distribution (As), and third-order aberration distribution in the left-right direction (HOA, Higher Order Aberration) of the basic design of the progressive multifocal lens. In this embodiment, when it is determined that the subject does not need to expand the clear vision area in the left-right direction, this basic design is selected. In addition, Figure 8This is a diagram showing the power distribution (Power), astigmatism distribution (As), and third-order aberration distribution in the left-right direction (HOA, Higher Order Aberration) of a progressive multifocal lens design where the power distribution is smoothed only in the left-right direction. In this embodiment, when it is determined that the subject needs to expand the clear vision area in the left-right direction, this design (left-right expansion design) is selected. Additionally, Figure 7 and Figure 8 The third-order aberration distributions shown represent the sum of the squares of the 0-degree component of coma aberration and the 0-degree component of trefoil aberration.

[0086] As Figure 7 and Figure 8 shown, it was confirmed that in the left-right expansion design, compared to the basic design, instead of a slight increase in the astigmatism amount on the principal meridian, the third-order aberration amount in the left-right direction around the principal meridian decreased.

[0087] Figure 9A This is a diagram showing the clear vision area (at least the area where the direction of the Landolt ring target with a visual acuity of 0.7 is known, or the area where the edge of the Landolt ring target with a visual acuity of 0.3 is clearly visible) when a subject wearing a progressive multifocal lens of the basic design observes at close range. The left side is a diagram of the state where the eye has no aberration, and the right side is a diagram of the state where the eye has 0.1 μm of trefoil aberration in the right direction. Figure 9B This is a diagram showing the clear vision area when a subject wearing a progressive multifocal lens of the left-right expansion design observes at close range. The left side is a diagram of the state where the eye has no aberration, and the right side is a diagram of the state where the eye has 0.1 μm of trefoil aberration in the right direction. In Figure 9A and Figure 9B the vertical axis represents the front-back direction and the horizontal axis represents the left-right direction with the subject's left eye as the reference. Additionally, the area surrounded by the dashed line is the clear vision area of the left eye, the area surrounded by the solid line is the clear vision area of the right eye, and the overlapping range of the two becomes the clear vision area of both eyes.

[0088] As Figure 9A and Figure 9B shown, it was confirmed that in the left-right expansion design, compared to the basic design, the clear vision area was expanded in the left-right direction. The same was confirmed when the subject's eye had trefoil aberration. Additionally, it was confirmed that when the subject's eye had trefoil aberration, the expansion effect of the clear vision area became more significant.

[0089] Based on the above content, for subjects wearing progressive multifocal lenses, when determining the necessity of the size of the clear vision area, in the case where it is determined that the subject needs to expand the clear vision area in the left and right directions, by selecting the left and right expansion design, a progressive multifocal lens that can be worn more comfortably can be determined.

[0090] In addition, in this specification, the clear vision area is estimated based on the add power and the astigmatism amount, but it is also possible to use values obtained by integrating, as weights, functions such as the Optical Transfer Function (OTF), the Modular Transfer Function (MTF), or multiplying them with the Contrast Sensitivity Function (CSF) of the visual system at a spatial frequency within a certain width. In the above calculations, the lens can be considered alone, or physiological factors such as the eye aberration, the eye axis, and the visual axis of the eye can be considered. In addition, the degree of blur perception can also be reflected in the threshold.

[0091] Explanation of Reference Numerals

[0092] 10: Subject

[0093] 20: Near target

[0094] 30: Far target

[0095] 40: Original image

[0096] 40A, 40B: Blurred image

[0097] S101: Process for determining the necessity of the clear vision area

[0098] S102: Process for design selection

Claims

1. A method for determining an aspheric progressive addition lens, characterized in that, comprising: a determination step of determining the necessity of the size of a clear vision area for a subject wearing an progressive multifocal lens; a design selection step of, when it is determined that the subject needs to expand the clear vision area in the left - right direction, selecting a design of an progressive multifocal lens in which the power distribution of the progressive multifocal lens is smoothed in the left - right direction, reducing the left - right coma aberration in the vicinity of the principal meridians of the progressive multifocal lens, and expanding the clear vision area in the left - right direction.

2. The method for determining an progressive multifocal lens according to claim 1, wherein, in the determination step, based on the amount of left - right coma aberration of the eyes of the subject, the necessity of the size of the clear vision area is determined.

3. The method for determining an progressive multifocal lens according to claim 1, wherein, in the determination step, based on the change in the line - of - sight movement of the subject when the subject repeatedly performs near - distance observation and far - distance observation, the necessity of the size of the clear vision area is determined.

4. The method for determining an progressive multifocal lens according to claim 1, wherein, in the determination step, based on the sensitivity of the subject to aberration, the necessity of the size of the clear vision area is determined.

5. The method for determining an progressive multifocal lens according to claim 1, wherein, the width of a smoothing filter for smoothing the power distribution in the left - right direction is greater than the narrowest width among the widths between the peaks of the left - right coma aberration on both sides of the principal meridian in the progressive multifocal lens before smoothing.

6. The method for determining an progressive multifocal lens according to claim 1, wherein, in the design selection step, instead of increasing the astigmatism amount on the principal meridian of the progressive multifocal lens, a design of an progressive multifocal lens in which the clear vision area is expanded in the left - right direction is selected.

7. The method for determining an progressive multifocal lens according to claim 1, wherein, in the design selection step, a design of an progressive multifocal lens in which the clear vision area is expanded in the left - right direction without changing the add - power curve of the principal meridian is selected.

8. The method for determining an progressive multifocal lens according to any one of claims 1 to 7, wherein, when it is determined in the determination step that the subject does not need to expand the clear vision area in the left - right direction, in the design selection step, a basic design of an progressive multifocal lens is selected.

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