Method for determining progressive power lenses

Abstract

This method for determining a progressive refractive power lens includes: an assessment step for assessing the degree of necessity of the width of a clear vision region for a subject that is to wear a progressive refractive power lens; and a design selection step for, when it is assessed that the subject requires an enlargement of the clear vision region in the depth direction, reducing the add power of an intermediate part of the progressive band of the progressive refractive power lens, thereby selecting a design for the progressive refractive power lens in which the clear vision region is enlarged in the depth direction.

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 transmitted 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 transmitted astigmatism is added, after subtracting the refractive power for correcting astigmatism, 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 an acquisition means for acquiring, as measurement data of an eye to be examined by a wavefront sensor, first distribution data regarding a distribution of refractive errors in the eye to be examined and second distribution data which is measurement data regarding a refractive power distribution in an ophthalmic lens for correcting the refractive error in the eye to be examined and which is measurement data regarding a part of regions among the measurement data regarding the refractive power distribution of the ophthalmic lens measured by a lensmeter, and a calculation means for obtaining third distribution data regarding a 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 further 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 time points, and a step of determining the amount of time during which the eyes were held in each orientation.

[0005] Furthermore, Non-Patent Document 1 suggests that optimizing vision within a standard arm length range increases comfort for the wearer. As means to achieve this, Patent Document 5 discloses a method for evaluating the clear vision area in a Cartesian coordinate system, and Patent Document 6 discloses a method for adjusting the add curve to suit the individual. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2020 / 067522 [Patent Document 2] International Publication No. 2020 / 067523 [Patent Document 3] Patent No. 6708955 [Patent Document 4] Patent No. 4659027 [Patent Document 5] Patent No. 6920287 [Patent Document 6] Patent No. 6991135 [Non-patent literature]

[0007] [Non-Patent Document 1] Varilux X series, searched on March 9, 2023, Internet<URL:https: / / www.essilor.sa / en / products / varilux-x-series> [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] 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 depth direction. [Means for solving the problem]

[0009] 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, A method for determining a progressive power lens, comprising: a design selection step of selecting a design for a progressive power lens in which the field of clear vision is expanded in the depth direction by reducing the add power in the intermediate part of the progressive zone of the progressive power lens, if the subject determines that an expansion of the field of clear vision in the depth direction is necessary.

[0010] A second 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.

[0011] A third 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.

[0012] A fourth aspect of the present invention is: The determination step involves determining the degree to which a wide field of vision is required based on the movement of an object when the subject performs a task that includes actions such as holding, viewing, and moving an object from which positional information can be acquired. This is a method for determining a progressive refractive power lens according to the first embodiment described above.

[0013] A fifth aspect of the present invention is: In the design selection step, the method for determining a progressive refractive power lens described in the first embodiment above is to select a design in which the add power is reduced so that the position Y = -210 mm and Z = 850 mm is the clear vision area, with the subject's eye as the origin, the vertical direction as the Y axis, and the depth direction as the Z axis.

[0014] A sixth aspect of the present invention is: In the design selection step, instead of increasing the amount of astigmatism on the principal meridians of the progressive power lens, a design of a progressive power lens with an expanded clear vision area in the depth direction is selected. This is the method for determining a progressive power lens according to the first aspect described above.

[0015] A seventh aspect of the present invention is In the design selection step, by reducing the added power, a design of a progressive power lens with an expanded clear vision area in the depth direction and the left - right direction is selected. This is the method for determining a progressive power lens according to the first aspect described above.

[0016] An eighth aspect of the present invention is In the determination step, when it is determined that the subject requires an expansion of the clear vision area in the left - right direction, in the design selection step, by smoothing the power distribution of the progressive power lens in the left - right direction, the tertiary aberration in the left - right direction around the principal meridians of the progressive power lens is reduced, and a design of a progressive power lens with an expanded clear vision area in the left - right direction is selected. This is the method for determining a progressive power lens according to the first aspect described above.

[0017] A ninth aspect of the present invention is In the determination step, based on the amount of tertiary aberration in the left - right direction of the subject's eye, the degree of necessity for the width of the clear vision area is determined. This is the method for determining a progressive power lens according to the eighth aspect described above.

[0018] A tenth aspect of the present invention is The width of the smoothing filter for smoothing the power distribution in the left - right direction is larger than the narrowest width among the widths between the peaks of the tertiary aberrations on both sides in the left - right direction on the principal meridian in the progressive power lens before smoothing. This is the method for determining a progressive power lens according to the eighth aspect described above.

[0019] An eleventh aspect of the present invention is In the design selection step, instead of increasing the amount of astigmatism on the principal meridians of the progressive power lens, a design of a progressive power lens with an expanded clear vision area in the left - right direction is selected. This is the method for determining a progressive power lens according to the eighth aspect described above.

[0020] A twelfth aspect of the present invention is: In the design selection step, if it is determined that the subject requires an expansion of the field of clear vision in the left-right direction, the design of a progressive lens that expands the field of clear vision in the left-right direction is selected without changing the addition curve of the principal meridian, which is the method for determining a progressive lens according to the eighth embodiment described above.

[0021] A thirteenth 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, the design selection step selects a basic design for a progressive power lens, thus this is a method for determining eyeglass lenses according to any one of the first to twelfth embodiments described above. [Effects of the Invention]

[0022] 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 depth direction. [Brief explanation of the drawing]

[0023] [Figure 1A] Figure 1A shows an example of the clear vision range when a subject wearing progressive lenses is looking at near objects, and is a diagram showing an example of the clear vision range when there are no aberrations in the eye. [Figure 1B] Figure 1B shows an example of the field of vision when a subject wearing progressive lenses is looking at near objects, and is a diagram showing an example of the field of vision when the eye has a trefoil shape (Z[-3,3]) in the left-right direction. [Figure 2] Figure 2 shows an example of the field of clear vision when a subject wearing a progressive refractive power lens (addition power +2D) with a basic design and depth expansion design according to the first embodiment of the present invention views an object on the principal meridian. [Figure 3] Figure 3 is a flowchart showing an example of a method for determining the progressive refractive power lens according to the first embodiment of the present invention. [Figure 4]Figure 4 is a schematic diagram illustrating the eye-tracking task according to the first embodiment of the present invention. [Figure 5] Figure 5 shows an example of the original image and multiple blurred images according to the first embodiment of the present invention. [Figure 6] Figure 6 shows an example of a spot image created by aberrations added to a blurred image according to the first embodiment of the present invention. [Figure 7] Figure 7 shows an example of the add curve for a progressive power lens (addition power +2D) with a basic design and depth expansion design according to the first embodiment of the present invention. [Figure 8A] Figure 8A is a diagram showing the left-right power distribution of the near-vision portion of a progressive power lens (for the left eye) with a basic design and left-right magnification design according to the first embodiment of the present invention. [Figure 8B] Figure 8B is the gradient distribution diagram of Figure 8A. [Figure 9A] Figure 9A is a diagram showing the left-right power distribution of the near-vision portion of a progressive power lens (for the left eye) with a basic design and depth-expanded design according to the first embodiment of the present invention. [Figure 9B] Figure 9B is the gradient distribution diagram of Figure 9A. [Figure 10] Figure 10 shows the power distribution, astigmatism distribution (As), and tertiary tertiary aberration distribution (HOA, Higher Order Aberration) of the basic design of a progressive power lens according to an embodiment of the present invention. [Figure 11] Figure 11 shows the power distribution, astigmatism distribution (As), and tertiary aberration distribution (HOA, Higher Order Aberration) in the left-right direction for a progressive power lens with a design in which the power distribution is smoothed only in the left-right direction, according to an embodiment of the present invention. [Figure 12] Figure 12 shows the power distribution, astigmatism distribution, and tertiary tertiary aberration distribution (HOA, Higher Order Aberration) in the left-right direction for a design in which the add power in the intermediate part of the progressive zone of a progressive power lens according to an embodiment of the present invention is reduced. [Figure 13A]Figure 13A shows the range of clear vision when a subject wearing a progressive power lens of the basic 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 13B] Figure 13B shows the range of clear 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 13C] Figure 13C shows the field of clear vision when a subject wearing a progressive power lens with a depth-expanding design according to an embodiment of the present invention is viewing objects at close range. 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 14A] Figure 14A 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 14B] Figure 14B 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]

[0024] <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 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 in this specification, unless otherwise specified, "clear vision area" means 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.

[0025] Figure 2 shows an example of the clear vision range when a subject wearing progressive power lenses (addition power +2D) views an object on the principal meridian. In Figure 2, the subject's left eye is set as the origin (0,0), the vertical direction is the Y-axis, and the depth direction is the Z-axis. The area enclosed by the dashed line in Figure 2 shows the clear vision range when wearing the basic design progressive power lenses. In terms of the optical design of progressive power lenses, the upper, middle, and lower sections of a polar coordinate system with the rotational center of the eyeball as the origin are assigned to the far, intermediate, and near vision sections, respectively, and the definition of object distance is also defined in the polar coordinate system. On the other hand, in terms of human spatial perception, height and depth are often perceived in a Cartesian coordinate system based on the front of the face. Furthermore, skeletally, vertical rotation around the shoulders and movement in the depth direction by flexion and extension of the arms are movements in the polar coordinate system, but switching between facing directly and half-facing is a movement in the depth direction in the Cartesian coordinate system, resulting in a complex movement that mixes both. Subjects accustomed to or well-adapted to progressive multifocal lenses tend to perceive in a polar coordinate system with the classical center of eye rotation as the origin, and rotate around a fixed shoulder. On the other hand, subjects unfamiliar with or poorly adapted to progressive multifocal lenses tend to perceive in a Cartesian coordinate system, and move their shoulders back and forth. The former range of motion corresponds to the arm length, or sleeve length, in body measurements, which is the range from the shoulder to the little finger of the arm, and is known to average around 740 mm. The latter range of motion corresponds to the half arm span, or half arm span, in body measurements, which is the range from the spine to the middle finger of the arm extended horizontally, and is known to average around 850 mm. Even when we say "arm range," depending on the subject, it may refer only to the length of the arm in the narrow sense, or it may be necessary to take into account the range of motion of the shoulder forward and backward, and the range of motion of the fingers. Therefore, it is preferable to determine which coordinate system the subject perceives and acts in and to design and select accordingly. Furthermore, it has been found that many subjects who are not accustomed to progressive multifocal lenses or who have low adaptability quickly understand and adapt to the characteristics of the region where all distances beyond a certain distance are visible, but they are significantly slower to understand and adapt to the characteristics of the intermediate to near region where the visible range is limited to both near and far distances. Specifically, for example, when a subject grasps an object at shoulder height and views it, there is a possibility that the subject may not be able to comfortably wear progressive lenses in situations where the object falls outside the range of clear vision if it is too close or too far away, such as before and after grasping the object at a height of Y = -210 mm, which corresponds to the subject's shoulder height. In fact, many of the complaints raised by subjects concern difficulty seeing during activities that straddle medium to close distances and involve unstable posture, such as picking up an object at a slight distance, rather than during close-range work in a stable posture within the natural range of arm movement while seated (for example, in real life, it becomes difficult to see as soon as you pick up a newspaper).

[0026] 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, whether it should be expanded horizontally, or whether it should be expanded in the depth direction) as an indicator of the required field of vision width. For example, for subjects who were determined to require expansion of the field of vision in the depth direction, they found a method to select a progressive lens design that expands the field of vision in the depth direction by reducing the add power in the middle of the progressive zone of the progressive lens. Furthermore, for subjects who are determined to require an expansion of the field of clear vision in the left-right direction, we have found a method to select a progressive lens design that expands the field of clear vision 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. Note that there are multiple methods (parameters) for determining the degree to which the field of clear vision needs to be expanded, which will be described in detail later. This method makes it 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 field of clear vision in the depth direction or left-right direction.

[0027] 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.

[0028] 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.

[0029] Furthermore, in this specification, "front-to-back direction" refers to the direction of the radial movement R in the polar coordinate system, and "depth direction" refers to the Z direction in the XYZ Cartesian coordinate system (X is the left-to-right direction, and Y is the up-to-down direction).

[0030] [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.

[0031] <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 3 is a flowchart showing an example of the method for determining the progressive power lens in this embodiment. As shown in Figure 3, 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 one of the following is selected to determine the progressive power lens more suitable for the subject: a design in which the clear vision area is expanded in the depth direction (depth expansion design), a design in which the clear vision area is expanded in the left-right direction (left-right expansion design), or a basic design.

[0032] (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.

[0033] 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.

[0034] 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.

[0035] 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 4 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 4, 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.

[0036] 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 have a long (or large) response time to clearly see a near target when shifting from far to near vision may be judged to need an expansion of their field of vision in the left-right (or depth) direction. Similarly, subjects who have a large difference in response time between shifting from far to near vision and shifting from near to far vision may be judged to need an expansion of their field of vision in the depth 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.

[0037] 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 or depth 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 or depth 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, without expanding the clear vision area in the left-right or depth 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 or depth-widening design may be more comfortable to wear.

[0038] 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 the amount) is varied from a predetermined original image. Figure 5 shows an example of an original image and multiple blurred images. In Figure 5, 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.

[0039] Figure 6 shows an example of a spot image created by an aberration added to a blurred image. In Figure 6, 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 added 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.

[0040] 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.

[0041] 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.

[0042] Once multiple blurred images are prepared, the subject's sensitivity to aberrations can be measured by presenting them simultaneously to the subject and having them compare how they appear, thereby obtaining the subject's subjective response. 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 5, simultaneously and asked to compare how they appear 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 they select 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 within 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).

[0043] 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.

[0044] 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 an expansion of the clear vision area in the left-right and depth directions (or that the disadvantages of choosing a left-right or depth-expanded 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 an expansion of the clear vision area in the left-right or depth direction (or that the advantages of choosing a left-right or depth-expanded design are likely to outweigh the disadvantages).

[0045] 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.

[0046] Furthermore, as a result of further investigation by the inventors, it was found 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 14A and 14B. In Figures 14A and 14B, the blurred image on the right is shown with blur added to the spot shown on the left (also called convolution of the spot). The spot shown in Figure 14A has a smaller spread (i.e., a smaller sum of squares of aberrations) than the spot shown in Figure 14B, but exhibits bimodality. On the other hand, the spot shown in Figure 14B has a slightly larger spread, but exhibits unimodality. When a group was presented with the blurred images shown in Figures 14A and 14B and asked to compare their perceptions, most subjects answered that the blurred image in Figure 14B was relatively preferable because the lines in Figure 14A 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.

[0047] 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.

[0048] Furthermore, in the clear vision area requirement determination step S101, a task (hereinafter referred to as the object movement task) may be performed in which the subject holds, views, and moves an object (e.g., a smartphone) equipped with a gyro sensor (angular velocity sensor) or the like, from which positional information can be acquired. Based on the movement progression of the object during the object movement task, the degree to which the clear vision area needs to be wide may be determined. Specifically, if the subject can move the object while clearly viewing it and maintaining a constant viewing distance, or move it in a way that changes the viewing distance, and can move the object smoothly, it may be determined that an expansion of the clear vision area in the depth direction is not necessary. On the other hand, if the subject cannot move the object smoothly, it may be determined that an expansion of the clear vision area in the depth direction is necessary. Furthermore, it may be determined that the movement of the object is caused by rotation or radial motion centered on the arms or eyes, or by vertical and horizontal motion in a Cartesian coordinate system, including forward and backward movement of the shoulders or face. If the former is the case, it may be determined that an expansion of the field of vision in the depth direction is not necessary, and if the latter is the case, it may be determined that it is necessary. Furthermore, in determining the smoothness of the object's movement, the object movement task may be started from a state where the object is not held in the hand, and the determination may be based on the time from when the object is grasped in the hand until it is first seen, as well as on the movement of the gaze, head, and shoulders. In particular, subjects whose posture changes significantly before and after reaching out towards the object and then returning their hand tend to have difficulty with depth perception because their gaze position on the lens is also likely to fluctuate, and it is preferable to determine that they need an expansion of the clear vision area in the depth direction. Furthermore, movement transitions may be measured using methods other than gyro sensors. For example, an object with an embedded IC chip may be moved, and the movement may be measured externally using electromagnetic waves. Alternatively, an object without a built-in measurement mechanism may be used, and the movement may be measured externally using optical distance measurement.

[0049] In addition, in the S101 process 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 by taking into account the subject's lifestyle, such as their occupation and hobbies. For example, for a subject whose occupation involves performing actions within arm's reach or slightly beyond while maintaining a fixed posture, it may be determined that an expansion of the field of clear vision in the depth direction is necessary.

[0050] 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, and even more preferably four) of the following: the amount of third-order aberration in the left-right direction of the subject's eye, the progression of the subject's gaze movement when the subject repeatedly performs near and far vision, the subject's sensitivity to aberrations, and the progression of object movement when an object movement task is performed.

[0051] Among the methods (parameters) for determining the degree of need for a wide field of vision described above, the method based on the amount of third-order aberration in the left-right direction of the subject's eye, the method based on the changes in the subject's gaze movement when the subject repeatedly performs near and far vision, and the method based on the subject's sensitivity to aberration are suitable for determining whether or not an expansion of the field of vision in the left-right direction is necessary. Furthermore, the method based on the changes in the subject's gaze movement when the subject repeatedly performs near and far vision, and the method based on the changes in the movement of an object when performing an object movement task, are suitable for determining whether or not an expansion of the field of vision in the depth direction is necessary. Therefore, in the field of vision need determination step S101, for example, the determination of whether or not the subject is likely to need an expansion of the field of vision in the left-right direction or the depth direction may be determined based on the determination result of one method or the results of a prior interview with the subject, and a decision may be made on whether or not to adopt another method.

[0052] (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 depth direction, this step selects a design for a progressive power lens in which the clear vision area in the depth direction is expanded by reducing the add power in the middle part of the progressive zone of the progressive power lens. This makes it possible to determine a progressive power lens that can be worn more comfortably by the subject who needs an expansion of the clear vision area in the depth direction. In addition, 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.

[0053] This section provides a more detailed explanation of the design of progressive lenses with an expanded field of vision in the depth direction (depth expansion design). For a subject with an average build, the shoulder is 210 mm below the eye, and when the shoulder is extended and the arm is extended horizontally, the tip of the middle finger can reach 850 mm away. Therefore, it is preferable that this position be within the field of vision. This assumes that when a subject with an average build picks up an object, the moment of visually inspecting and touching the object occurs within the field of vision. In other words, in the depth expansion design, it is preferable that the position Y = -210 mm, Z = 850 mm be within the field of vision, as shown by the area enclosed by the solid line in Figure 2. In this state, when defining the field of vision in a Cartesian coordinate system along the body axis or a polar coordinate system based on the shoulder, the field of vision extends to a distance roughly equivalent to the fully extended arm in the depth or front-to-back direction of that coordinate system. As a result, the subject can perceive their own field of vision more easily and wear progressive lenses more comfortably. In this specification, expanding the field of vision in the depth direction means widening the vertical range (especially the downward direction) so that the field of vision extends to the distance of an outstretched arm (Z=850mm) or to infinity. In other words, it does not mean that a physical quantity of the lens design is expanded, but rather that the length along the depth vector (whether based on the eye or the horizontal) for the subject is expanded. Furthermore, for subjects with an average build, when facing forward and extending their arms horizontally, the tip of their little finger should be 740 mm away, and it is preferable that this position also falls within the range of clear vision. This assumes that when a subject with an average build picks up an object, the entire process from firmly grasping the object to holding it in place takes place within the range of clear vision.

[0054] Let's explain the conditions for making the position Y=-210mm, Z=850mm the clear vision area. The position on the lens corresponding to the visual angle tanθ=-210 / 850 is 27mm × tanθ = -6.67mm, assuming the distance from the lens to the center of eye rotation is 27mm, which means it is -6.67mm from the fitting point. Therefore, the add power at this position, taking astigmatism into account (addition power - absolute value of astigmatism / 2), is the diopter equivalent of the distance to the position Y=-210mm, Z=850mm, which is 1000 / √(210 2 +8502 It is sufficient if the value is less than 1.14D.

[0055] Figure 7 shows an example of the add curve for a progressive power lens (addition power +2D) in both the basic design and the depth-extended design. In Figure 7, the horizontal axis represents the vertical position with the lens fitting point set to 0, and the vertical axis represents the add power considering astigmatism (addition power - absolute value of astigmatism / 2). As shown in Figure 7, in the depth-extended design, the add power in the middle of the progressive zone (for example, around Y=-6.67mm) is reduced compared to the basic design. This makes it possible to set the add power considering astigmatism (addition power - absolute value of astigmatism / 2) at the Y=-6.67mm position to less than 1.14D, and as shown in Figure 2, it becomes possible to make the position Y=-210mm, Z=850mm a clear vision area. Furthermore, in the case of progressive lenses with an add power of less than +2D, it is preferable to reduce the add power in the middle of the progressive zone so that the add power (add power - absolute value of astigmatism / 2) at the Y=-6.67mm position, taking astigmatism into account, becomes 1.14 × (add power / 2). This allows the lower boundary of the clear vision area shown in Figure 2 to become closer to a downward slope to the right, thereby widening the range in which one can see up to infinity.

[0056] As mentioned above, reducing the add power in the middle of the progressive zone of a progressive power lens has the advantage of expanding the field of clear vision in the depth direction, but it also has the disadvantage of increasing the amount of astigmatism along 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 depth direction, at the expense of increased astigmatism along the principal meridian.

[0057] Furthermore, as mentioned above, by reducing the add power in the middle of the progressive zone of the progressive power lens, it is possible to slightly reduce the tertiary aberration in the left-right direction around the principal meridian of the progressive power lens, thereby expanding the field of clear vision not only in the depth direction but also in the left-right direction. Therefore, in the design selection step S102, it is also possible to select a design for a progressive power lens in which the field of clear vision is expanded in both the depth and left-right directions by reducing the add power in the middle of the progressive zone of the progressive power lens. If it is determined that the subject needs an expansion of the field of clear vision more in the left-right direction than in the depth direction, it is preferable to select a left-right expansion design that has a greater effect on expanding the field of clear vision in the left-right direction.

[0058] In the design selection process S102, for example, if the degree of clear vision requirement determination process S101 determines that the subject needs an expansion of the clear vision area in the left-right direction, the power distribution of the progressive lens may be smoothed in the left-right direction to reduce the tertiary aberration in the left-right direction around the principal meridian of the progressive lens, thereby selecting a design for a progressive lens that expands the clear vision area in the left-right direction. This makes it possible to determine a progressive lens that can be worn more comfortably by a subject who needs an expansion of the clear vision area in the left-right direction.

[0059] 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 8A is a left-right power distribution diagram of the near vision portion of a progressive lens (for the left eye), and Figure 8B is a gradient distribution diagram of Figure 8A. 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 8A, 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 8B, 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.

[0060] Furthermore, as mentioned above, the depth-extended design also has the effect of expanding the field of vision in the left-right direction. Figure 9A is a left-right power distribution diagram of the near-vision portion of a progressive power lens (for the left eye), and Figure 9B is a gradient distribution diagram of Figure 9A. Note that the sum of the coma aberration and Trefoil in the 0-degree direction and this gradient distribution are proportionally related. As shown in Figure 9A, the power distribution around the principal meridian P is smoothed in the depth-extended design (solid line) compared to the basic design (dashed line). 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 about the same as) the basic design by offsetting the reduction in the sag direction. As shown in Figure 9B, in the depth-extended design as well, the power distribution is smoothed in the left-right direction, and the cubic aberration distribution in the left-right direction also becomes gentler, so the field of vision (for example, the area where the cubic aberration around the principal meridian P is within ±0.1 μm) is expanded in the left-right direction.

[0061] 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.

[0062] 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.

[0063] If it is determined that the subject requires an expansion of the field of clear vision in the left-right direction, in the design selection step S102, it is preferable to select a design for a progressive power lens that expands the field of clear vision 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 expand the field of clear vision in the left-right direction while reducing the increase in aberration in the vertical direction and maintaining the basic design of the progressive power lens as much as possible.

[0064] 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 and depth directions (or that the disadvantages of selecting a left-right or depth expansion design are likely to outweigh the advantages), then the left-right or depth 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 and depth directions.

[0065] 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.

[0066] <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.

[0067] 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.

[0068] Furthermore, while the above-described embodiment explained the case where one of the following is selected: left-right expansion design, depth expansion design, or basic design, the left-right expansion design and depth expansion design are not limited to one, and multiple variations (for example, those with different widths of the clear viewing area in the left-right direction) may be selected.

[0069] 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]

[0070] 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.

[0071] (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 4, 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.

[0072] In this embodiment, if there was a large variation in the amount of head movement and convergence of the subject during the eye-shift task, or if the response time was long (or varied greatly), it was determined that the subject needed to expand their field of vision in the left-right direction. Furthermore, even if the variation in the amount of head movement and convergence was small, if there was a large difference in the response time when shifting from far-away to near-eye gaze and when shifting from near-eye to far-away gaze, it was determined that the subject needed to expand their field of vision in the depth direction. If none of the above conditions were met, it was determined that the subject did not need to expand their field of vision in the left-right or depth direction. The above assessment is based on a correlation with the ability to see through the clearly visible point on the lens. However, some subjects may move their heads back and forth due to habits or tendencies, regardless of whether they are wearing progressive lenses. To address such cases, it may be advisable to conduct a pre-assessment interview and incorporate this into the assessment. For subjects who have a habit of moving their heads back and forth, a depth-expanding design is often preferable to mitigate the effects of distance changes and eye movement blur due to head movement. It should be noted that the optimal design cannot often be determined by head movement alone; therefore, it is preferable to make a judgment based on multiple pieces of information and multiple tasks.

[0073] (Design selection process S102) Figure 10 shows the power distribution (Power), astigmatism distribution (As), and tertiary 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 field of clear vision in the left-right and depth directions. Figure 11 shows the power distribution (Power), astigmatism distribution (As), and tertiary 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 field of clear vision in the left-right direction. Figure 12 shows the power distribution (Power), astigmatism distribution (As), and tertiary cubic aberration distribution (HOA, Higher Order Aberration) in the left-right direction for a design in which the add power in the middle part of the progressive zone of the progressive power lens is reduced. In this embodiment, this design (depth expansion design) was selected when it was determined that the subject needed an expansion of the clear vision area in the depth direction. The third-order aberration distributions shown in Figures 10 to 12 represent the sum of the squares of the 0-degree component of coma aberration and the 0-degree component of Trefoil.

[0074] As shown in Figures 10 and 11, 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 cubic aberration in the left-right direction around the principal meridian was reduced. Furthermore, as shown in Figures 10 and 12, in the depth enlarged design, we confirmed that, compared to the basic design, the amount of astigmatism along the principal meridian increased slightly, while the amount of cubic aberration in the left-right direction around the principal meridian was slightly reduced.

[0075] Figure 13A shows the range of clear vision (the area in which at least the direction of the Landolt ring image with visual acuity 0.7 can be determined, or the area in which the edge of the Landolt ring image with visual acuity 0.3 can be clearly seen) when a subject wearing a progressive power 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 in which the eye has a 0.1 μm Trefoil in the rightward direction. Figure 13B shows the range of clear vision when a subject wearing a progressive power 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 in which the eye has a 0.1 μm Trefoil in the rightward direction. Figure 13C shows the range of clear vision when a subject wearing a progressive power lens with a depth 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 in which the eye has a 0.1 μm Trefoil in the rightward direction. In Figures 13A to 13C, the vertical axis represents the anterior-posterior direction and the horizontal axis represents the lateral direction, with the subject's left eye as the reference point. The area enclosed by the dashed line represents the clear vision area of ​​the left eye, the area enclosed by the solid line represents the clear vision area of ​​the right eye, and the overlapping area represents the clear vision area of ​​both eyes.

[0076] As shown in Figures 13A and 13B, the left-right enlargement design confirmed an expansion of the field of clear vision in the left-right direction compared to the basic design. Similarly, when the subjects had Trefoil eyes, an expansion of the field of clear vision in the left-right direction was confirmed. Furthermore, it was confirmed that the effect of expanding the field of clear vision by the left-right enlargement design was more pronounced when the subjects had Trefoil eyes. In addition, as shown in Figures 13A and 13C, the depth enlargement design also confirmed an expansion of the field of clear vision in the left-right direction compared to the basic design.

[0077] As explained in the first embodiment, for the position of the tip of the middle finger when the subject extends their arm horizontally with their shoulder outstretched (Y=-210mm, Z=850mm in Figure 2) to be in the clear vision zone, the add power (addition power - absolute value of astigmatism / 2) considering astigmatism at a position on the lens -6.67mm from the fitting point should be less than 1.14D. In the basic design of this embodiment, the add power considering astigmatism was 1.211D, which did not satisfy the above condition. On the other hand, in the depth-extended design of this embodiment, the add power considering astigmatism was 1.135D, which was confirmed to satisfy the above condition. In other words, in the depth-extended design, it was confirmed that the position Y=-210mm, Z=850mm is in the clear vision zone.

[0078] 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 depth-expanding design when it is determined that the subject needs an expansion of the field of clear vision in the depth direction, a progressive lens that can be worn more comfortably can be determined. Furthermore, we confirmed that by 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, a progressive lens that can be worn more comfortably can be determined.

[0079] 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]

[0080] 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 of selecting a design for a progressive power lens in which the field of clear vision is expanded in the depth direction by reducing the add power of the intermediate part of the progressive zone of the progressive power lens when it is determined that the subject needs an expansion of the field of clear vision in the depth direction.

2. 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.

3. 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.

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 vision based on the movement of an object when the subject performs a task that includes actions such as holding, viewing, and moving an object from which positional information can be acquired.

5. The method for determining a progressive refractive power lens according to claim 1, wherein in the design selection step, when the subject's eye is set as the origin, the vertical direction is the Y-axis, and the depth direction is the Z-axis, a design is selected in which the add power is reduced so that the position Y = -210 mm and Z = 850 mm is the area of ​​clear vision.

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 clear vision area is expanded in the depth direction, instead of the amount of astigmatism on the principal meridian of the progressive refractive power lens increasing.

7. The method for determining a progressive power lens according to claim 1, wherein in the design selection step, a design of a progressive power lens is selected in which the field of clear vision is expanded in the depth direction and left-right direction by reducing the add power.

8. The method for determining a progressive power lens according to claim 1, wherein in the determination step, if it is determined that the subject requires an expansion of the field of clear vision in the left-right direction, in the design selection step, the design of the progressive power lens is selected in which the power distribution of the progressive power lens is smoothed in the left-right direction to reduce the third-order aberration in the left-right direction around the principal meridian of the progressive power lens, thereby expanding the field of clear vision in the left-right direction.

9. The method for determining a progressive refractive power lens according to claim 8, 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.

10. The method for determining a progressive refractive power lens according to claim 8, 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.

11. The method for determining a progressive refractive power lens according to claim 8, 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.

12. The method for determining a progressive power lens according to claim 8, wherein, in the design selection step, if it is determined that the subject requires an expansion of the field of clear vision in the left-right direction, a design of a progressive power lens that expands the field of clear vision in the left-right direction is selected without changing the addition curve of the principal meridian.

13. A method for determining a progressive power lens according to any one of claims 1 to 12, wherein in the determination step, if it is determined that the subject does not require an expansion of the field of clear vision, the design selection step selects a basic design for a progressive power lens.

Images