Method for determining progressive power lenses

Abstract

Provided is a method for determining a progressive refractive power lens, comprising: a determination step for determining the need for broadness of a clear vision region for a subject wearing a progressive refractive power lens; and a design selection step for selecting a design of the progressive refractive power lens in which tertiary aberration in a left-right direction around the main meridian of the progressive refractive power lens is reduced and the clear vision region is expanded in the left-right direction, by smoothing the frequency distribution of the progressive refractive power lens in the left-right direction when it is determined that enlargement of the clear vision region in the left-right direction is required for the subject.

Description

Technical Field

[0001] The present invention relates to a method for determining a progressive refractive power lens.

Background Art

[0002] Patent Documents 1 and 2 disclose a progressive refractive power lens in which a transmission astigmatism is added to the near vision portion and the intermediate vision portion among the distance vision portion, the near vision portion, and the intermediate vision portion, and in the near vision portion and the intermediate vision portion to which the transmission astigmatism is added, after subtracting the refractive power for astigmatism correction, a portion where the amount of refractive power in the horizontal direction is larger than the amount of refractive power in the vertical direction (or the amount of refractive power in the vertical direction is larger than the amount of refractive power in the horizontal direction) is included.

[0003] Further, Patent Document 3 discloses an ophthalmic prescription assisting device including acquisition means for acquiring measurement data of an eye to be examined by a wavefront sensor, which is first distribution data regarding the distribution of refractive errors in the eye to be examined, and second distribution data which is measurement data regarding the refractive power distribution in an ophthalmic lens for correcting the refractive errors in the eye to be examined, and which is measurement data for some regions among the measurement data regarding the refractive power distribution of the ophthalmic lens measured by a lensmeter, and calculation means for obtaining third distribution data regarding the distribution of refractive errors considering correction by the ophthalmic lens based on the first distribution data and the second distribution data acquired by the acquisition means.

[0004] Further, Patent Document 4 discloses a method for determining human visual behavior, which includes a step of recording the movement of a person's head while performing a visual task, a step of recording at least one eye movement of the person while performing the visual task, a step of determining the relative orientation of the eyes with respect to the head at different times, and a step of determining the amount of time during which the eyes were held in each orientation.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] One embodiment of the present invention aims to provide a technology that can determine a progressive power lens that can be worn more comfortably by a subject who requires an expansion of the field of clear vision in the left-right direction. [Means for solving the problem]

[0007] A first aspect of the present invention is: A determination process for determining the degree of need for a wide field of clear vision in subjects wearing progressive power lenses, The method for determining a progressive power lens includes a design selection step, in which, if the subject determines that an expansion of the field of clear vision in the left-right direction is necessary, the power distribution of the progressive power lens is smoothed in the left-right direction to reduce the tertiary aberration in the left-right direction around the principal meridian of the progressive power lens, thereby selecting a design for a progressive power lens that expands the field of clear vision in the left-right direction.

[0008] A second aspect of the present invention is: The determination step involves determining the degree to which the width of the field of clear vision needs to be based on the amount of third-order aberration in the left-right direction of the subject's eye, which is the method for determining the progressive refractive power lens described in the first embodiment above.

[0009] A third aspect of the present invention is: The determination step involves determining the degree to which a wide field of clear vision is required, based on the changes in the subject's gaze movement when the subject repeatedly performs near and far vision, which is the method for determining the progressive refractive power lens described in the first embodiment.

[0010] A fourth aspect of the present invention is: The determination step involves determining the degree to which the width of the field of clear vision needs to be based on the subject's sensitivity to aberrations, which is the method for determining the progressive refractive power lens according to the first embodiment described above.

[0011] A fifth aspect of the present invention is: The method for determining a progressive refractive power lens according to claim 1, wherein the width of the smoothing filter for smoothing the frequency distribution in the left-right direction is greater than the narrowest width among the widths between the peaks of third-order aberrations on both sides of the principal meridian in the progressive refractive power lens before smoothing.

[0012] A sixth aspect of the present invention is: The method for determining a progressive refractive power lens according to the first embodiment is as follows: in the design selection step, instead of increasing the amount of astigmatism on the principal meridian of the progressive refractive power lens, a design of a progressive refractive power lens is selected in which the field of clear vision is expanded in the left-right direction.

[0013] A seventh aspect of the present invention is: The method for determining a progressive refractive power lens according to the first embodiment above is to select a design for a progressive refractive power lens in which the field of clear vision is expanded in the left-right direction without changing the addition curve of the principal meridian, in the design selection step described above.

[0014] An eighth aspect of the present invention is: In the determination step, if it is determined that the subject does not require an expansion of the field of clear vision in the left-right direction, the design selection step selects a basic design for a progressive power lens, thus providing a method for determining eyeglass lenses according to any one of the first to seventh embodiments described above. [Effects of the Invention]

[0015] According to one embodiment of the present invention, it is possible to determine a progressive power lens that can be worn more comfortably by a subject who requires an expansion of the field of clear vision in the left-right direction. [Brief explanation of the drawing]

[0016] [Figure 1A] FIG. 1A is a diagram showing an example of a clear vision area when a subject wearing a progressive refractive power lens has myopic vision, and is a diagram showing an example of a clear vision area in a state where there is no aberration in the eye. [Figure 1B] FIG. 1B is a diagram showing an example of a clear vision area when a subject wearing a progressive refractive power lens has myopic vision, and is a diagram showing an example of a clear vision area in a state where the eye has a trefoil (Z[-3,3]) in the left-right direction. [Figure 2] FIG. 2 is a flowchart showing an example of a method for determining a progressive refractive power lens according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram for explaining a line-of-sight movement task according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing an example of an original image and a plurality of blurred images according to the first embodiment of the present invention. [Figure 5] FIG. 5 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. [Figure 6A] FIG. 6A is a diagram showing the left-right direction power distribution of the near vision portion of a progressive refractive power lens (for left eye) according to the first embodiment of the present invention. [Figure 6B] FIG. 6B is a gradient distribution diagram of FIG. 6A. [Figure 7] FIG. 7 is a diagram showing the power distribution (Power), astigmatism distribution (As), and left-right direction higher order aberration distribution (HOA, Higher Order Aberration) of the basic design of a progressive refractive power lens according to an example of the present invention. [Figure 8] FIG. 8 is a diagram showing the power distribution (Power), astigmatism distribution (As), and left-right direction higher order aberration distribution (HOA, Higher Order Aberration) of a design in which the power distribution of a progressive refractive power lens according to an example of the present invention is smoothed only in the left-right direction. [Figure 9A] FIG. 9A is a diagram showing the clear vision area when a subject wearing a progressive refractive power lens of a basic design according to an example of the present invention has myopic vision. The left side shows a state where there is no aberration in the eye, and the right side shows a state where the eye has a trefoil of 0.1 μm in the right direction. [Figure 9B] Figure 9B shows the field of vision when a subject wearing a progressive refractive power lens with a left-right magnification design according to an embodiment of the present invention is viewing objects at near distance. The left side shows the state where there is no aberration in the eye, and the right side shows the state where the eye has a 0.1 μm trefoil in the rightward direction. [Figure 10A] Figure 10A shows an example of a bimodal spot (left in the figure) and a blurred image obtained by convolving the spot (right in the figure). [Figure 10B] Figure 10B shows an example of a unimodal spot (left in the figure) and a blurred image obtained by convolving the spot (right in the figure). [Modes for carrying out the invention]

[0017] <Insights gained by the inventor> First, the inventors' findings will be explained. Figures 1A and 1B show examples of the area in which at least the direction of a Landolt ring image with visual acuity of 0.7 can be determined, or the area in which the edge of a Landolt ring image with visual acuity of 0.3 can be clearly seen (hereinafter referred to as the "clear vision area") when a subject wearing progressive lenses is viewing objects at near distance. In Figures 1A and 1B, the vertical axis represents the anterior-posterior direction (direction of the radial movement R in polar coordinates), and the horizontal axis represents the lateral direction, with the subject's left eye L as the reference point. The area enclosed by the dashed line is the clear vision area of ​​the left eye L, the area enclosed by the solid line is the clear vision area of ​​the right eye R, and the overlapping area of ​​the two is the clear vision area of ​​both eyes. Hereafter, unless otherwise specified, "clear vision area" refers to the clear vision area of ​​both eyes. Figure 1A shows the field of clear vision when there are no ocular aberrations, and Figure 1B shows an example of the field of clear vision when the eye has a third-order aberration, Trefoil (Z[-3,3]), in the left-right direction. As shown in Figure 1B, it was found that when the eye has Trefoil, the fields of clear vision shift between the left and right eyes, and the field of clear vision for both eyes narrows. Since ocular aberrations vary depending on individual differences and conditions, when the field of clear vision is narrowed, subjects may not be able to comfortably wear progressive lenses.

[0018] The inventors diligently investigated the problems described above. As a result, they found that some subjects were not bothered even with a narrowed field of vision, while others could not comfortably wear progressive lenses even without a narrowed field of vision. Therefore, they determined the degree of field of vision width required by each subject (i.e., whether the field of vision width of the basic design of the progressive lens is sufficient, or whether it should be expanded laterally) as an indicator of the degree of field of vision width required. For example, for subjects who were determined to require an expansion of the field of vision width laterally, they found a method to select a progressive lens design that expands the field of vision laterally by smoothing the power distribution of the progressive lens in the left-right direction, thereby reducing the tertiary aberration around the principal meridian of the progressive lens. Note that there are multiple methods (parameters) for determining the degree of field of vision width required, which will be described in detail later. This method makes it possible to determine a progressive lens that is more comfortable to wear for subjects who require an expansion of the field of clear vision in the left-right direction, with minimal risk (i.e., while maintaining the basic design of the progressive lens as much as possible).

[0019] In this specification, the basic design of a progressive power lens refers to the design of a lens temporarily selected (or worn) by the subject, or the design of a lens temporarily recommended by the seller, etc., which is the basic design of the progressive power lens for that subject.

[0020] Furthermore, it was found that third-order aberrations (including Trefoil and coma aberrations) in progressive lenses occur in the near-vision area in a manner surrounding the principal meridian (in the direction toward the principal meridian), and when the absolute value of the third-order aberration in the left-right direction near the principal meridian increases by 0.1 μm or more compared to the position where the absolute value is minimum, subjects perceive difficulty in near vision (for example, being unable to determine the direction of a Landolt ring image with a visual acuity of 0.7, or being unable to clearly see the edges of a Landolt ring image with a visual acuity of 0.3). Therefore, in this specification, the clear vision area may be rephrased as the region where the absolute value of the third-order aberration in the left-right direction near the principal meridian increases by 0.1 μm or more compared to the position where the absolute value is minimum.

[0021] [Details of the Embodiments of the Invention] Next, one embodiment of the present invention will be described below with reference to the drawings. However, the present invention is not limited to these examples and is intended to include all modifications within the meaning and scope equivalent to the claims as shown in the claims.

[0022] <First Embodiment of the Invention> (1) How to determine eyeglass lenses First, the method for determining the progressive power lens in this embodiment will be described. Figure 2 is a flowchart showing an example of the method for determining the progressive power lens in this embodiment. As shown in Figure 2, the method for determining the progressive power lens in this embodiment includes, for example, a clear vision area requirement determination step S101 and a design selection step S102. In this embodiment, we will describe the case in which either a design in which the clear vision area is expanded in the left-right direction (left-right expansion design) or a basic design is selected to determine a progressive power lens more suitable for the subject.

[0023] (Step S101 of determining the degree of necessity of clear vision area) Step S101, which determines the degree of need for a clear field of vision, is a process for determining the degree of need for a wide clear field of vision in a subject wearing progressive lenses (to which the basic design has been applied). There are multiple methods (parameters) for determining the degree of need for a wide clear field of vision. One example is explained below.

[0024] In the step S101 for determining the degree of need for the field of clear vision, the degree of need for a wide field of clear vision may be determined, for example, based on the amount of tertiary aberration in the left-right direction of the subject's eye. As shown in Figure 1B, if the eye has tertiary aberration (trefoil), the field of clear vision becomes narrower. Therefore, subjects with a large amount of tertiary aberration in the left-right direction of their eyes (absolute value of the difference between the left and right eyes) (for example, 0.1 μm or more) may be determined to need an expansion of the field of clear vision in the left-right direction. Also, if the subject has dry eyes, etc., the trefoil in the eye tends to increase, so the measured value of the tertiary aberration may be adjusted, for example, taking into account the subject's constitution. To measure the amount of tertiary aberration in the subject's eye, known techniques such as wavefront sensors may be used.

[0025] However, since the amount of tertiary aberration in the eye varies greatly depending on the subject's condition and the surrounding environment, it is preferable to consider other parameters when determining the degree to which a wide field of clear vision is necessary. The following describes other parameters for determining the degree to which a wide field of clear vision is necessary.

[0026] In the step S101 for determining the degree of need for the clear vision area, the degree of need for the width of the clear vision area may be determined, for example, based on the changes in the subject's gaze movement when the subject repeatedly performs near and far vision. Figure 3 is a schematic diagram illustrating a task (hereinafter referred to as the gaze movement task) for determining the degree of need for the width of the clear vision area based on the changes in the subject's gaze movement. As shown in Figure 3, in the gaze movement task, the subject 10 repeatedly (for example, alternately) looks at a near target 20 placed at a near distance (for example, viewing distance dS = 40 cm) and a far target 30 placed at a far distance (for example, viewing distance dL = 3 m). As the near target 20 and the far target 30, for example, a Landolt ring image with a visual acuity of 0.7 displayed on a display terminal such as a tablet can be used.

[0027] When a subject is able to clearly see a near target and their eye movement is small (for example, when reading in real life), the size of the field of clear vision is not much of a problem. However, if a subject shifts their gaze significantly from a distant target to a near target (for example, when shifting their gaze from watching television to a book in their hand), a narrow field of clear vision may make it difficult for some subjects to focus on the near target. Specifically, this includes subjects who are not accustomed to using progressive lenses and use various points on the lens when viewing a near target (i.e., there is a large variation in head movement and convergence), or subjects whose response time to clearly see a near target is long. Therefore, when performing an eye movement task, subjects who show large variations in head movement and convergence (especially when shifting from distant to near vision) may be judged to need an expansion of the field of clear vision in the left-right direction. Furthermore, in eye-shifting tasks, subjects who take a long time (or show large variability) to clearly see a near target when shifting from far to near vision may be judged to need an expansion of the field of clear vision in the left-right direction. When measuring the amount of head movement and convergence of subjects in eye-shifting tasks, for example, the subject's head and eyeballs can be imaged using a camera attached to a display device that shows the near target, and the amount of head movement and convergence can be measured using image recognition.

[0028] Furthermore, in the clear vision area necessity determination step S101, the degree to which the clear vision area needs to be wide may be determined, for example, based on the subject's sensitivity to aberrations. In the design selection step S102 described later, if a design of a progressive power lens with an expanded clear vision area in the left-right direction is selected, the amount of astigmatism on the principal meridian will increase compared to the basic design. In other words, as compensation for expanding the clear vision area in the left-right direction, the quality (image quality) on the principal meridian will decrease compared to the basic design. Therefore, for subjects who are sensitive to the increase in astigmatism on the principal meridian, a progressive power lens with the basic design and no expansion of the clear vision area in the left-right direction may be more comfortable to wear. On the other hand, for subjects who are not sensitive to the increase in astigmatism on the principal meridian, a progressive power lens with a left-right expansion design may be more comfortable to wear.

[0029] An example of a method for measuring a subject's sensitivity to aberrations is described. To measure sensitivity to aberrations, for example, multiple blurred images (in this embodiment, two blurred images) can be used, in which the amount of aberration added (preferably only this amount) is varied from a predetermined original image. Figure 4 shows an example of an original image and multiple blurred images. In Figure 4, a blurred image 40A is shown in which a predetermined amount of aberration is added to the original image 40, and a blurred image 40B is shown in which the amount of aberration added is larger than that of blurred image 40A.

[0030] Figure 5 shows an example of a spot image created by an aberration added to a blurred image. In Figure 5, a spot image with a tail extending to the lower left of the page is shown. A blurred image with an aberration that creates such a spot image appears blurred in the lower left direction. In other words, the added aberration causes a significant (characteristic) decrease in the spatial frequency characteristics in the lower left direction. In this specification, this characteristic direction of the decrease in spatial frequency characteristics due to the added aberration will be referred to as the direction of the aberration.

[0031] It is preferable that the directions of the aberrations added to multiple blurred images (for example, blurred image 40A and blurred image 40B) are approximately the same. This makes it easier for subjects to compare how the multiple blurred images appear. In this specification, "approximately the same direction of aberration" includes not only cases where the directions are perfectly the same, but also cases where there is a slight difference of ±15 degrees or less in the direction of the aberrations. The direction of the aberration refers to the direction of the component with the largest absolute value among all the coefficients of all the blurred images when the aberrations added to each of the simultaneously displayed blurred images are each expanded using the Zernike polynomial.

[0032] When selecting aberrations to add to the original image 40, you may, for example, arbitrarily select from aberrations produced by a standard progressive power lens.

[0033] Once multiple blurred images are prepared, the subject can be presented with the multiple blurred images simultaneously and asked to compare how they appear to the subject, and their subjective response can be obtained to measure the subject's sensitivity to aberrations. Specifically, for example, a task (hereinafter referred to as the aberration sensitivity task) is performed in which the subject is presented with blurred image 40A and blurred image 40B, as shown in Figure 4, simultaneously and asked to compare how they appear to the subject and select which one appears clearer (or "unclear"). If the subject selects blurred image 40A, which has a smaller amount of added aberration (i.e., the correct answer), it can be determined that the subject has high sensitivity to blur, and if the subject selects blurred image 40B, which has a larger amount of added aberration (i.e., the incorrect answer), it can be determined that the subject has low sensitivity to blur. In this specification, presenting multiple blurred images simultaneously means presenting multiple blurred images so that they are visible to the subject while multiple blurred images are present in the subject's field of view, and the timing of the start or end of presentation of each blurred image is not limited (for example, the start or end of presentation timings for blurred image 40A and blurred image 40B may be staggered).

[0034] However, if sensitivity to blur is determined by a single subjective response, it may include cases where, for example, a subject happened to select a blurred image with a small amount of aberration, even though they did not actually perceive any difference in appearance. Therefore, in this embodiment, it is preferable to further prepare a plurality of similar blurred images that are similar to the plurality of blurred images, and to simultaneously present the subject with a plurality of similar blurred images in which the amount of added aberration (preferably only that amount) is changed, have them compare how they appear, and measure the stability of the subjective response by obtaining the subject's subjective response multiple times. A similar blurred image means, for example, an image in which a blurred image has been rotated by an arbitrary angle, or an image in which a blurred image has been enlarged or reduced by an arbitrary magnification.

[0035] For subjects who perform the aberration sensitivity task described above and are determined to have high sensitivity to blur, it may be determined that they do not need to expand the field of clear vision in the left-right direction (or that the disadvantages of choosing a left-right expansion design are likely to outweigh the advantages). Conversely, for subjects who are determined to have low sensitivity to blur, it may be determined that they need to expand the field of clear vision in the left-right direction (or that the advantages of choosing a left-right expansion design are likely to outweigh the disadvantages).

[0036] Furthermore, for subjects who consistently answered correctly after performing the aberration sensitivity task multiple times, it may be determined that they have high sensitivity to blur, and in design selection step S102, a low-aberration design may be selected. Also, for subjects who consistently answered incorrectly, it may be determined that they have high sensitivity to blur but prefer a state with large aberrations, and in design selection step S102, a design with the aberrations preferred by the subject may be selected. Also, for subjects whose correct and incorrect answers are inconsistent and who answer "I don't know" infrequently, it may be determined that they have low sensitivity to blur but do not perceive themselves as having low sensitivity, and in design selection step S102, a balanced design between a low-aberration design and a design that improves other aspects (for example, a design that expands the clear vision area in the left-right direction) may be selected. Also, for subjects who answer "I don't know" frequently, it may be determined that they have low sensitivity to blur, and an improved design that involves a trade-off with aberrations (for example, a design that expands the clear vision area in the left-right direction) may be selected.

[0037] Furthermore, the inventors' further investigations revealed that subjects do not judge the clarity of an image solely based on the simple magnitude of blur (or the amount of aberration that causes it) or MTF (Modulation Transfer Function). Specific examples are shown in Figures 10A and 10B. In Figures 10A and 10B, the blurred image on the right is created by adding blur corresponding to the spot shown on the left (also known as convolving the spot). The spot shown in Figure 10A has a smaller spread (i.e., a smaller sum of squared aberrations) than the spot shown in Figure 10B, but exhibits bimodality. On the other hand, the spot shown in Figure 10B has a slightly larger spread, but exhibits unimodality. When a group was presented with the blurred images shown in Figures 10A and 10B and asked to compare their perceptions, most subjects answered that the blurred image in Figure 10B was relatively preferable because the lines in Figure 10A were clearer but doubled. This is likely because very few subjects preferred bimodal blur. Therefore, in an aberration sensitivity task, subjects may be asked to compare a blur image convolved with spots that have slightly smaller aberrations but are multimodal (including bimodal, which corresponds to astigmatism + spherical aberration of the eye; trimodal, which corresponds to Trefoil + spherical aberration of the eye; and tetramodal, which corresponds to higher-order aberrations of the eye) with a blur image convolved with spots that have slightly larger aberrations but are unimodal. Subjects who prefer the blur image convolved with unimodal spots may be judged to have high sensitivity to blur. Here, "high sensitivity to blur" refers not so much to sensitivity to the magnitude of aberrations, but rather to sensitivity to whether or not aberration correction is performed correctly.

[0038] In the aberration sensitivity task, subjects may be scored based on whether their subjective responses are consistent with the average support within the group, and their sensitivity to blur may be determined based on these scores. The average support may be determined using statistical values ​​obtained when the problem was previously given to a certain group, or it may be estimated using machine learning, etc. Specifically, for example, in a problem where subjects compare blurred images on the left and right, if many subjects prefer the blurred image on the left (higher support rate), subjects who answered that the left image is preferred may be given +1 point, etc., as it is consistent with the average support within the group, while subjects who answered that the right image is preferred may be given -1 point, etc., as it is not consistent with the average support within the group. The total score and subtotals for each problem type may then be tallied, and for example, if the score is above a predetermined score (threshold), it may be determined that the subject has high sensitivity to blur, and if the score is below the predetermined score (threshold), it may be determined that the subject has low sensitivity to blur. In other words, the subject's sensitivity to blur may be determined based on the relationship between the score and a predetermined threshold. By assigning scores in this way, it becomes possible to make judgments not only based on the simple magnitude of aberrations and MTF, but also by considering the subject's preference for blur (the degree and tendency of blur that is acceptable to the subject). Furthermore, it makes it easier to understand the characteristics of the subject, facilitating counseling when deciding on eyeglass lenses.

[0039] Furthermore, the degree to which the field of clear vision needs to be wide may be determined by combining the various parameters described above. For example, in the field of clear vision need determination step S101, the degree to which the field of clear vision needs to be wide may be determined based on at least one (preferably two, more preferably three) of the amount of third-order aberration in the left-right direction of the subject's eye, the changes in the subject's gaze movement when the subject repeatedly performs near and far vision, and the subject's sensitivity to aberrations.

[0040] (Design selection process S102) In the design selection step S102, for example, if the clear vision area requirement determination step S101 determines that the subject needs an expansion of the clear vision area in the left-right direction, this step selects a design for a progressive lens that expands the clear vision area in the left-right direction by smoothing the power distribution of the progressive lens in the left-right direction, thereby reducing the tertiary aberration in the left-right direction around the principal meridian of the progressive lens. This makes it possible to determine a progressive lens that can be worn more comfortably by the subject who needs an expansion of the clear vision area in the left-right direction. In the design selection step S102, for example, a lens with a design suitable for the subject may be selected from several pre-prepared customized lenses.

[0041] This section provides a more detailed explanation of the design of progressive lenses with an expanded field of vision in the left-right direction (left-right expansion design). Figure 6A is a left-right power distribution diagram of the near vision portion of a progressive lens (for the left eye), and Figure 6B is a gradient distribution diagram of Figure 6A. Note that the sum of the coma aberration and Trefoil in the 0-degree direction is proportional to this gradient distribution. As shown in Figure 6A, in the left-right expansion design (solid line) compared to the basic design (dashed line), the power distribution around the principal meridian P is smoothed by applying a smoothing filter (e.g., a Gaussian filter) in the left-right direction. If the power of the principal meridian is reduced due to smoothing, the power of the principal meridian can be adjusted to be the same as (or to the same extent as) the basic design by offsetting the reduction in the sag direction. As shown in Figure 6B, smoothing the frequency distribution in the left-right direction also smooths the cubic aberration distribution in the left-right direction, thereby expanding the area of ​​clear vision (for example, the area where the cubic aberration around the principal meridian P is within ±0.1 μm) in the left-right direction. By selecting such a left-right expansion design, it becomes possible to determine a progressive lens that can be worn more comfortably with minimal risk (i.e., while maintaining the basic design of the progressive lens as much as possible) for subjects who require an expansion of the area of ​​clear vision in the left-right direction.

[0042] The width of the smoothing filter used to smooth the power distribution of a progressive lens in the left-right direction is preferably greater than the narrowest width between the peaks of third-order aberrations on both sides of the principal meridian in the progressive lens before smoothing. This effectively reduces third-order aberrations.

[0043] As described above, smoothing the power distribution of a progressive power lens only in the left-right direction reduces third-order aberrations in the left-right direction around the principal meridian of the progressive power lens, which has the advantage of expanding the field of clear vision in the left-right direction. However, it also has the disadvantage of increasing the amount of astigmatism on the principal meridian compared to the basic design. Therefore, in the design selection process S102, it is also possible to select a design for a progressive power lens that expands the field of clear vision in the left-right direction, at the expense of increased astigmatism on the principal meridian.

[0044] In the design selection step S102, it is preferable to select a design for a progressive power lens in which the field of clear vision is expanded in the left-right direction by smoothing the frequency distribution only in the left-right direction without changing the addition curve of the principal meridian. This makes it possible to reduce the increase in aberration in the vertical direction and expand the field of clear vision in the left-right direction while maintaining the basic design of the progressive power lens as much as possible.

[0045] Furthermore, in the clear vision area need determination step S101, if it is determined that the subject does not need an expansion of the clear vision area in the left-right direction (or that the disadvantages of selecting a left-right expansion design are likely to outweigh the advantages), the left-right expansion design may not be selected, and the basic design of the progressive power lens may be chosen instead. This makes it possible to provide a progressive power lens with optimized quality (image quality) along the principal meridian to subjects who do not need an expansion of the clear vision area in the left-right direction.

[0046] By applying the methods described above to multiple subjects, it is possible to design progressive lenses that are suitable for the individual needs of each subject.

[0047] <Other embodiments of the present invention> Although embodiments of the present invention have been specifically described above, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0048] For example, although the above embodiment described a method for determining the progressive power lens, the present invention can also be applied as a method for determining the degree of need for a clear vision area. In this case, only the clear vision area need determination step S101 may be performed, and the design selection step S102 may be omitted.

[0049] Furthermore, while the above-described embodiment explained the case where either a left-right enlarged design or a basic design is selected, the left-right enlarged design is not limited to one, and multiple variations (for example, those with different widths of the clear vision area in the left-right direction) may be selected.

[0050] Furthermore, while the above embodiment described design selection based on the third-order aberration of the eyeball, design selection may also be made based on (or in consideration of) the degree of fixation misalignment and the degree of misalignment between the eye's aiming line and the visual axis. This is because the amount of the horizontal third-order aberration component is added to or subtracted from the measured eyeball aberration according to the degree of the above-mentioned misalignment. In addition to the degree of the above-mentioned misalignment, elements that deviate horizontally from the standard model in the design or measurement are factors that cause fluctuations in the amount of third-order aberration, and therefore it is preferable to use them in the decision-making process for design selection. [Examples]

[0051] 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.

[0052] (Step S101 of determining the degree of necessity of clear vision area) In this embodiment, the eye-tracking task described above was performed, and the degree to which the range of clear vision needed was determined based on the progression of the subject's eye movements. Specifically, as shown in Figure 3, a near target 20 (a Landolt ring image with visual acuity of 0.7 displayed on a smartphone) was placed 30 degrees below subject 10 at a viewing distance dS = 40 cm, and a far target 30 (a Landolt ring image with visual acuity of 0.7 displayed on a tablet device) was placed directly in front of subject 10 at a viewing distance dL = 3 m. The near target 20 and the far target 30 were then displayed alternately a total of 30 times, and subject 10 was asked to view them and identify the break in the Landolt ring image.

[0053] In this embodiment, when the subject performed the eye-tracking task, if there was a large variation in the amount of head movement and convergence, or if the response time was long (or varied greatly), it was determined that the subject needed to expand the field of clear vision in the left-right direction. If not, it was determined that the subject did not need to expand the field of clear vision in the left-right direction.

[0054] (Design selection process S102) Figure 7 shows the power distribution (Power), astigmatism distribution (As), and cubic aberration distribution (HOA, Higher Order Aberration) in the left-right direction for the basic design of a progressive power lens. In this embodiment, this basic design was selected when it was determined that the subject did not require an expansion of the clear vision area in the left-right direction. Figure 8 shows the power distribution (Power), astigmatism distribution (As), and cubic aberration distribution (HOA, Higher Order Aberration) in the left-right direction for a design in which the power distribution of the progressive power lens is smoothed only in the left-right direction. In this embodiment, this design (left-right expansion design) was selected when it was determined that the subject required an expansion of the clear vision area in the left-right direction. Note that the cubic aberration distributions shown in Figures 7 and 8 represent the sum of the squares of the 0-degree component of coma aberration and the 0-degree component of trefoil aberration.

[0055] As shown in Figures 7 and 8, in the left-right enlarged design, we confirmed that the amount of astigmatism along the principal meridian increased slightly compared to the basic design, while the amount of third-order aberration in the left-right direction around the principal meridian was reduced.

[0056] Figure 9A shows the range of clear vision (the area where at least the direction of the Landolt ring image with visual acuity 0.7 can be determined, or the area where the edge of the Landolt ring image with visual acuity 0.3 can be clearly seen) when a subject wearing a progressive lens of the basic design is viewing objects at near distance. The left side shows the state with no ocular aberrations, and the right side shows the state where the eye has a 0.1 μm Trefoil in the rightward direction. Figure 9B shows the range of clear vision when a subject wearing a progressive lens with a left-right magnification design is viewing objects at near distance. The left side shows the state with no ocular aberrations, and the right side shows the state where the eye has a 0.1 μm Trefoil in the rightward direction. In Figures 9A and 9B, the vertical axis represents the anterior-posterior direction and the horizontal axis represents the left-right direction, with the subject's left eye as the reference point. The area enclosed by the dashed line is the range of clear vision of the left eye, the area enclosed by the solid line is the range of clear vision of the right eye, and the overlapping area is the range of clear vision of both eyes.

[0057] As shown in Figures 9A and 9B, the left-right enlargement design confirmed that the field of clear vision was expanded in the left-right direction compared to the basic design. Similarly, when the subjects' eyes had Trefoil lenses, the field of clear vision was confirmed to be expanded in the left-right direction. Furthermore, it was confirmed that the effect of expanding the field of clear vision was more pronounced when the subjects' eyes had Trefoil lenses.

[0058] Based on the above, we confirmed that by determining the degree of need for a wide field of clear vision in subjects wearing progressive lenses, and selecting a left-right expansion design when it is determined that the subject needs an expansion of the field of clear vision in the left-right direction, it is possible to determine a progressive lens that can be worn more comfortably.

[0059] In this specification, the clear vision range is estimated from the add power and astigmatism, but the optical transfer function (OTF) or modular transfer function (MTF), or the value obtained by multiplying these by the contrast sensitivity function (CSF) of the visual system as a weight and integrating over a certain range of spatial frequencies, may also be used. The above calculation may take into account not only the lens alone, but also physiological elements such as ocular aberrations and axial and visual axes. Furthermore, the degree of blur perception may be reflected in the threshold. [Explanation of Symbols]

[0060] 10 subjects 20 Near visual target 30 Distance target 40 original images 40A, 40B blurred images S101 Clear vision area necessity level determination process S102 Design Selection Process

Claims

1. A determination process for determining the degree of need for a wide field of clear vision in subjects wearing progressive power lenses, A method for determining a progressive power lens, comprising: a design selection step, in which, if the subject determines that an expansion of the field of clear vision in the left-right direction is necessary, the power distribution of the progressive power lens is smoothed in the left-right direction to reduce third-order aberrations in the left-right direction around the principal meridian of the progressive power lens, thereby selecting a design for a progressive power lens in which the field of clear vision in the left-right direction is expanded.

2. The method for determining a progressive refractive power lens according to claim 1, wherein the determination step determines the degree of need for a wide field of clear vision based on the amount of third-order aberration in the left-right direction of the subject's eye.

3. The method for determining a progressive refractive power lens according to claim 1, wherein the determination step involves determining the degree to which a wide field of vision is necessary based on the changes in the subject's gaze movement when the subject repeatedly performs near and far vision.

4. The method for determining a progressive refractive power lens according to claim 1, wherein the determination step determines the degree of need for a wide field of clear vision based on the subject's sensitivity to aberrations.

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

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

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

8. A method for determining a progressive power lens according to any one of claims 1 to 7, wherein, in the determination step, it is determined that the subject does not require an expansion of the field of clear vision in the left-right direction, and in the design selection step, a basic design of a progressive power lens is selected.

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