Contact lens for astigmatism correction and method for designing same

Abstract

The present invention relates to a contact lens for astigmatism correction and a method of designing same and, more particularly, to a contact lens for astigmatism correction and a method of designing same, wherein: the inner surface of a lens body is formed as a first curved surface extending radially from the center thereof; at least a portion of the outer surface of the lens body is formed as a second curved surface extending radially from the center thereof; the lens body is formed such that the center of the first curved surface and the center of the second curved surface are offset from each other in a plan view of the lens body; a ballast region including the thickest portion of the lens is formed on the side opposite to the center of the first curved surface with respect to the center of the second curved surface on an imaginary line connecting the center of the first curved surface and the center of the second curved surface in the plan view of the lens body; and the thickest portion of the lens is formed such that the lower edge of an upper eyelid and the upper edge of a lower eyelid do not pass over the portion when a user blinks while wearing the contact lens.

Description

Contact lens for correcting astigmatism and design method thereof

[0001] The present invention relates to a contact lens for correcting astigmatism and a design method thereof, and more particularly, to a contact lens using prism ballast technology for use in astigmatic patients.

[0002] In particular, the present invention relates to a contact lens for correcting astigmatism and a design method thereof, which can prevent a decrease in wearing comfort due to a difference in thickness between different parts of the lens, in providing a contact lens to which prism ballast technology is applied.

[0003] Astigmatism is a condition in which objects cannot be seen clearly because the light entering the eye is not focused at one point due to the surface of the eye being uneven. Specifically, it refers to a condition in which objects appear blurry because the light entering the eye does not focus at one point due to the irregularity of the corneal surface, causing the degree of refraction to change.

[0004] Additionally, if you have astigmatism, you may experience decreased vision at both distances and near, symptoms tend to be worse when contrast sensitivity is low, and glare and halo effects may occur.

[0005] This increases the inconvenience of city life, makes daily life difficult, and becomes a factor that lowers the quality of life.

[0006] This type of astigmatism does not usually progress or change significantly unless there is a specific ophthalmic abnormality, and is corrected by using appropriate glasses or contact lenses as prescribed by an ophthalmologist after an ophthalmological examination.

[0007] Meanwhile, when using contact lenses for astigmatism correction, the most important factors are astigmatism correction power, axial stability, and wearing comfort.

[0008] First, astigmatism correction ability is the ability to correct astigmatism, which can be said to be the ability of the basic function of a contact lens for astigmatism correction.

[0009] This is the ability to correct the astigmatism of the target patient. Since most astigmatism shows an asymmetrical pattern based on the center of the eye, the thickness and shape of each part of the contact lens are determined according to the condition of the target patient's eye.

[0010] Next, axial stability is the most reliable indicator of the performance of astigmatism-correcting contact lenses. It refers to the ability of the contact lenses to maintain a set direction and position without rotating or shaking after the user puts them on.

[0011] As explained above, contact lenses are formed asymmetrically depending on the eye condition of the target patient. If these contact lenses rotate after being worn, their ability to correct astigmatism will inevitably decrease.

[0012] Accordingly, contact lenses for astigmatism correction must maintain a constant direction without rotating around an imaginary axis passing through the center of the eye after being worn, and this ability is called axial stability.

[0013] Lastly, comfort refers to the ability to minimize the foreign body sensation after wearing contact lenses for astigmatism correction, and can be improved by minimizing the foreign body sensation especially during blinking or eye movement.

[0014] As explained above, contact lenses are formed asymmetrically depending on the eye condition of the subject patient. After wearing the contact lenses, when the subject patient blinks or moves his / her gaze, a foreign body sensation may occur due to the difference in thickness of the contact lenses.

[0015] Minimizing this foreign body sensation and improving wearing comfort are important capabilities of contact lenses for astigmatism correction.

[0016] In particular, because the contact lens may rotate or move during blinking or when the eye moves due to differences in thickness, minimizing foreign body sensation plays an important role in maintaining axial stability and astigmatism correction ability.

[0017] One of the related technologies, Korean Patent Publication No. 10-1989-0013500, a prior art document entitled “Contact lens for astigmatism correction and manufacturing method thereof” (hereinafter referred to as “prior art”), is a technology regarding a contact lens for astigmatism correction in which four zones are set up, down, left and right based on the central part of the contact lens, and different thicknesses are set for each zone.

[0018] This prior art only considered the astigmatism correction power among the three capabilities of the contact lens for astigmatism correction described above, and did not consider axial stability and wearing comfort. In particular, as described above, if the contact lens rotates or moves due to blinking or gaze movement after wearing the contact lens, the problem of the astigmatism correction power being reduced may occur.

[0019] In order to solve the above problems, the present invention aims to provide a contact lens for correcting astigmatism and a design method thereof that can secure axial stability by applying prism ballast technology to a contact lens used for astigmatism patients.

[0020] In particular, the present invention aims to provide a contact lens for correcting astigmatism and a design method thereof, which can prevent a decrease in wearing comfort due to a difference in thickness between different parts of the lens, in providing a contact lens to which prism ballast technology is applied.

[0021] Specifically, the present invention aims to provide a contact lens for correcting astigmatism and a design method thereof, which can prevent a foreign body sensation occurring during blinking or moving the eye direction and improve wearing comfort by matching the edge (thickest part) of the area where the prism ballast is applied to the edge of the wearer's lower eyelid.

[0022] In order to achieve the above object, the contact lens for astigmatism according to the present invention is formed such that the inner surface of the lens body is formed as a first curved surface extending radially from the center, and at least a portion of the outer surface of the lens body is formed as a second curved surface extending radially from the center, and the lens body is formed such that, in a plan view of the lens body, the center of the first curved surface and the center of the second curved surface are misaligned, and, on an imaginary line connecting the center of the first curved surface and the center of the second curved surface in a plan view of the lens body, a ballast region including a part with the thickest lens thickness is formed on the opposite side of the center of the first curved surface based on the center of the second curved surface, and the part with the thickest lens thickness can be formed such that the lower boundary of the upper eyelid and the upper boundary of the lower eyelid do not pass the part when the user makes a squint while wearing the contact lens.

[0023] In addition, the thickest part of the lens may be formed at a position 1.2 mm to 2.6 mm away from the edge of the first curved surface toward the center of the first curved surface in a plan view of the lens body.

[0024] In addition, the lens body may be formed such that, in a plan view of the lens body, the distance between the center line of the first curved surface and the center line of the second curved surface is 0.05 mm to 0.35 mm.

[0025] In addition, the lens body includes a cutting surface extending radially from the edge of the second curved surface to the edge of the first curved surface, and the thickest part of the lens may be formed at the intersection of the widest part of the cutting surface in a plan view of the lens body, an imaginary straight line passing through the center of the first curved surface, and the edge of the second curved surface.

[0026] In addition, the design method of the contact lens for astigmatism according to the present invention may include an inner curve setting step of setting the inner side surface of the lens body as a first curved surface extending radially from the center; an outer curve setting step of setting the outer side surface of the lens body as a second curved surface extending radially from the center; an inner and outer side position setting step of setting the positions of the inner side surface and the outer side surface so that the center of the first curved surface and the center of the second curved surface are misaligned in a plan view of the lens body; and a ballast region setting step of setting a ballast region including a part with the thickest lens thickness based on the position where the lower eyelid and the upper eyelid meet during a squint movement, based on the user's optometric information or optometric statistical information on a plurality of astigmatism correctors.

[0027] In addition, the ballast region setting step can set the thickest part of the lens at a position 1.2 mm to 2.6 mm away from the edge of the first curved surface toward the center of the first curved surface in a plan view of the lens body.

[0028] In addition, at least one of the inner curve setting step and the outer curve setting step can set the corresponding curve based on optometry information including the user's ocular curvature and astigmatism status.

[0029] In addition, the ballast area setting step includes a cutting surface setting step of setting a cutting surface that extends radially from the edge of the second curved surface to the edge of the first curved surface; and the cutting surface setting step may set a cutting angle of the cutting surface based on a virtual surface that includes the edge of the first curved surface so that the part where the lens thickness is the thickest is formed in the ballast area.

[0030] By the above-described solution, the present invention has the advantage of securing axial stability by applying prism ballast technology to contact lenses used for astigmatic patients.

[0031] In particular, the present invention provides a contact lens to which prism ballast technology is applied, and thus has the advantage of preventing a decrease in wearing comfort due to differences in thickness between different parts of the lens.

[0032] Specifically, the present invention has the advantage of preventing a foreign body sensation caused by the upper eyelid, etc., when blinking (eye movement) or moving the gaze direction, and improving the wearing comfort by making the edge (thickest part) of the area where the prism ballast is applied match the edge of the wearer's lower eyelid.

[0033] As a result, the present invention has the advantage of not only providing astigmatism correction power, which is the basic function of a contact lens for correcting astigmatism, but also showing axial stability to continuously maintain the astigmatism correction power, and improving the wearing comfort by minimizing the foreign body sensation felt by the user after wearing it.

[0034] In addition, the present invention has the advantage of being able to provide an astigmatism-correcting contact lens having an optimized shape in response to the position of the user's eye, lower eyelid, and upper eyelid, and the range of movement of the lower eyelid and upper eyelid due to blinking or gaze movement, by analyzing an image of the eye of a target patient (user) with astigmatism and reflecting the image in the production of an astigmatism-correcting contact lens to be used by the target patient.

[0035] FIG. 1 is a perspective view showing one embodiment of a contact lens for correcting astigmatism according to the present invention.

[0036] Figure 2 is a front view of Figure 1.

[0037] Figure 3 is a cross-sectional view taken along line 'A-A' of Figure 1.

[0038] Fig. 4 is a cross-sectional view illustrating a state in which Fig. 1 is worn on the eye.

[0039] Figure 5 is a flowchart showing one embodiment of a method for designing a contact lens for astigmatism correction according to the present invention.

[0040] Figure 6 is a drawing specifically explaining each step of Figure 5.

[0041] Figure 7 is a flowchart explaining a specific embodiment of step 'S400' of Figure 1.

[0042] Examples of the contact lens for correcting astigmatism and the design method thereof according to the present invention can be applied in various ways, and the most preferred embodiment will be described below with reference to the attached drawings.

[0043] Fig. 1 is a perspective view showing one embodiment of a contact lens for correcting astigmatism according to the present invention, Fig. 2 is a front view of Fig. 1, Fig. 3 is a cross-sectional view taken along the line 'A-A' of Fig. 1, and Fig. 4 is a cross-sectional view explaining a state in which Fig. 1 is worn on an eye.

[0044] Referring to FIGS. 1 and 3, a lens body (100) forming a contact lens for astigmatism correction is formed with an inner surface (110), an outer surface (120), a ballast area (130), and a cutting surface (140).

[0045] The inner surface (110) is the inner side of the lens body (100), that is, the part that touches the eye of the user (target patient), and corresponds to a curved surface with a concave shape.

[0046] This inner surface (110) may be formed as a first curved surface extending radially from the center. For example, the first curved surface may be determined to correspond to the curve of the outer surface of the user's eye.

[0047] The outer surface (120) refers to a convex curved surface that is the outer surface of the lens body (100), that is, the opposite surface of the inner surface (110), and at least a part of this outer surface (120) may be formed as a second curved surface that extends radially from the center. Here, the second curved surface may be determined in response to the user's astigmatism condition. However, the second curved surface is not determined in direct response to the user's astigmatism condition, and may be determined to suit the user's astigmatism condition while satisfying the following conditions.

[0048] Referring to FIGS. 2 and 6, the inner side surface (110) and the outer side surface (120) forming the lens body (100) are formed so that the center (CP1) of the first curved surface and the center (CP2) of the second curved surface are misaligned in a plan view of the lens body (100). Here, the plan view of the lens body (100) refers to a top view (a state in which the lens body is viewed from the top of the lens body) when the lens body (100) is placed on the floor as in FIG. 2 (a state in which the convex outer side is placed so as to face upwards). The fact that the two centers are misaligned means that they are misaligned in the plane coordinates without considering the height.

[0049] In other words, when the lens body (100) is placed on a virtual surface (VP), the respective center lines (CL1, CL2; virtual lines perpendicular to the drawing in FIG. 2, expressed as points in the drawing) passing through the centers of the respective surfaces in a vertical direction are formed to be misaligned with each other at a predetermined interval (L1). Here, the virtual surface (VP) refers to a plane including a circle corresponding to the edge of the first curved surface.

[0050] For example, the center line (CL2) of the second curved surface, which is the outer surface (120), may be located at a position spaced apart by a certain distance (L1) in the downward direction (downward direction based on the state of being worn on the user's eye) from the center line (CL1) of the first curved surface, which is the inner surface (110).

[0051] And, a ballast region (130) can be formed in which the thickest lens thickness is formed at a position passing the center (CP2) of the second curved surface in the direction from the center line (CL1) of the first curved surface to the center line (CL2) of the second curved surface (box-shaped arrow in FIG. 2), that is, on the opposite side of the center (CP2) of the second curved surface based on the center (CP2) of the second curved surface.

[0052] Referring to FIG. 2, the ballast region (130) can be formed on an imaginary straight line connecting two center lines (CL1, CL2), and as shown in the enlarged portion of FIG. 3, the thickest portion (Tp; Thickest Portion) of the lens body (100) can be included in a portion of this imaginary straight line that passes through the lower cutting surface (140), and a point (Pp) corresponding to the outer surface of the thickest portion (Tp) can be a peak point (Pp; Peak point).

[0053] For example, the peak point (Pp) of the thickest part (Tp) in the lens body (100) may be formed at a position spaced apart (L2) by 1.2 mm to 2.6 mm from the edge of the first curved surface toward the center of the first curved surface in the lens body (100), preferably at a position spaced apart by 1.5 mm to 2.2 mm, as shown in FIG. 3.

[0054] Accordingly, the ballast region (130) can be formed to include a peak point (Pp) located 1.2 mm to 2.6 mm toward the center of the lens body (100) based on the lower edge of the lens body (100).

[0055] And, the lens body (100) can be formed so that the distance (L1) between the center line (CL1) of the first curved surface and the center line (CL2) of the second curved surface is 0.05 mm to 0.35 mm, preferably 0.1 mm to 0.2 mm.

[0056] In addition, as shown in FIGS. 2 and 3, a ring-shaped cutting surface (140) may be formed along the edge of the second curved surface, which is the outer surface (120) of the lens body (100). In this case, the ballast region (130) may be formed on at least a portion of the cutting surface (140), as shown in FIG. 2.

[0057] In other words, the lens body (100) may include a cutting surface (140) extending radially from the edge of the second curved surface to the edge of the first curved surface, and the peak point (Pp) of the thickest portion (Tp) of the lens may be formed at the intersection of an imaginary straight line radially passing through the portion with the widest width of the cutting surface (140) and the edge of the second curved surface.

[0058] More specifically, the lens body (100) can be formed so that the center line (CL2) of the second curved surface is misaligned downward with respect to the center line (CL1) of the first curved surface, as described above.

[0059] And, the cutting surface (140) can be formed to widen from the top to the bottom of the lens body (100), and the ballast region (130) can be formed in an area including the widest part of the cutting surface (140). Here, the widest part of the cutting surface (140) corresponds to the point where an imaginary straight line passing through the center line (CL1) of the first curved surface and the center line (CL2) of the second curved surface and the inner edge (the edge meeting the outer surface) of the cutting surface (140) meet, that is, the peak point (Pp) of the thickest part (Tp) of the lens thickness, and an adjacent area including the point can be set as the 'widest part' or the 'ballast region'.

[0060] This ballast area (130) is the area where the thickest part of the lens body (100) is located, and may be a relatively heavy area formed to ensure that the center of gravity of the contact lens is maintained in a downward direction.

[0061] When the ballast region (130), which corresponds to the heaviest part of the lens body (100), is formed at the bottom of the lens body (100), the contact lens can be maintained so that the ballast region (130) always faces downward even after the user wears the contact lens for astigmatism correction of the present invention.

[0062] In this way, the contact lens for astigmatism correction of the present invention can form a center of gravity in the lower direction of the lens by applying prism ballast technology, thereby suppressing the contact lens for astigmatism correction from rotating about the axis of the user's visual direction, thereby ensuring sufficient axial stability.

[0063] However, when prism ballast technology is applied to a contact lens for astigmatism correction, the shape of the contact lens is formed asymmetrically (asymmetrically in the vertical direction in Fig. 2), and in particular, the peak point (Pp) of the thickest part of the lens (Tp) is shaped to protrude, so when the user blinks or moves the gaze direction after wearing the lens, a foreign body sensation may occur due to the peak point (Pp).

[0064] Specifically, when the user (wearer) blinks his / her eyes in a circular motion, the upper eyelid (UE) primarily descends. If there is a relatively protruding part, i.e. a thick ballast area, on the plane of movement of the upper eyelid (UE), the user feels a foreign body sensation in the upper eyelid (UE).

[0065] Additionally, even when the ballast area is located in an area covered by the lower eyelid (LE), the user feels a foreign body sensation in the lower eyelid (LE).

[0066] Accordingly, the present invention, as shown in FIG. 4, forms the peak point (Pp) of the thickest part (Tp) of the lens at a position corresponding to the upper boundary (PL) of the lower eyelid (LE), thereby allowing the upper eyelid (UE) to pass through the thin part of the lens body (100) during the process of lowering and raising, thereby minimizing the foreign body sensation and improving the wearing comfort.

[0067] This is of course because the foreign body sensation can be minimized for the same or similar reasons even when the user moves the direction of gaze while keeping his or her eyes open.

[0068] As a result, the astigmatism correction contact lens of the present invention can prevent a decrease in wearing comfort due to differences in thickness between different parts of the lens while applying a prism ballast.

[0069] Below, we will look at a method for designing such a lens body (100).

[0070] FIG. 5 is a flowchart showing one embodiment of a method for designing a contact lens for astigmatism correction according to the present invention, and FIG. 6 is a drawing specifically explaining each step of FIG. 5.

[0071] Referring to FIG. 5, a design method of a contact lens for astigmatism correction includes an inner curve setting step (S100), an outer curve setting step (S200), an inner and outer position setting step (S300), and a ballast area setting step (S400).

[0072] The inner curve setting step (S100) sets the inner side (110) of the lens body (100), and when setting the inner side (110), it sets it as a first curved surface extending radially from the center (CP1). Here, the center (CP1) refers to a point on the first curved surface that corresponds to the highest position from the virtual horizontal plane (VHP) when the lens body (100) is placed on the virtual horizontal plane (VHP).

[0073] For example, the first curved surface can be set to correspond to the eye (particularly, the curve of the cornea) of the user (target patient), and this can be set based on the user's optometry information (e.g., ophthalmic prescription).

[0074] The outer curve setting step (S200) sets the outer surface (120) of the lens body (100) as a second curved surface, and when setting the outer surface (120), it sets it as a second curved surface extending radially from the center (CP2).

[0075] At this time, the second curved surface, which is the outer surface (120), can also be set based on the user's optometry information (e.g., ophthalmic prescription).

[0076] The inner and outer position setting step (S300) sets the positions of the inner side (110) and the outer side (120) by making the center (CP1) of the first curved surface and the center (CP2) of the second curved surface misaligned in a plan view of the lens body. More specifically, as shown in the center of FIG. 6, the positions of the inner side (110) and the outer side (120) are set by making the center line (CL1) passing vertically through the center (CP1) of the first curved surface and the center line (CL2) passing vertically through the center (CP2) of the second curved surface misaligned by a predetermined distance (L1) on a virtual horizontal plane (VHP) set in response to the state in which the lens body (100) is placed.

[0077] The ballast region setting step (S400) is a process of setting a ballast region (130), which is an region where the lens thickness is the thickest, that is, an region where the peak point (Pp) of the thickest part (Tp) of the lens thickness is included. As shown in the lower part of Fig. 6, by setting a cutting surface (140), the ballast region (130) can be set so that the peak point (Pp) of the thickest part (Tp) of the lens thickness is located within the ballast region (130).

[0078] At this time, the peak point (Pp) may be formed based on the position where the lower and upper eyelids meet when blinking on the eyeball, based on the optometric information of a specific user or optometric statistical information of multiple users. Here, the optometric statistical information may include statistics on at least some items of optometric information for astigmatism correction users (e.g., the position of the upper border of the lower eyelid, etc.).

[0079] Looking specifically at the cutting surface (140), the cutting surface (140) is formed in a ring shape along the edge of the lens body (100), and as described above, the cutting surface is set so that the ballast area (130) with the thickest lens thickness is formed in the direction from the center line (CL1) of the first curved surface to the center line (CL2) of the second curved surface.

[0080] At this time, the width (W1) of the upper part and the width (W2) of the lower part of the cutting surface (140) can be set to correspond to the user's upper eyelid (UE) and lower eyelid (LE).

[0081] For example, the width (W1) of the upper portion of the cutting surface (140) can be set so that the thickness of the lens body (100) is thin so as not to cause a foreign body sensation during movement of the upper eyelid (UE).

[0082] In addition, the width (W2) of the lower part of the cutting surface (140) can be set to correspond to the user's lower eyelid (LE).

[0083] Below, the ballast area setting step (S400) will be described in more detail.

[0084] Figure 7 is a flowchart explaining a specific embodiment of step 'S400' of Figure 1.

[0085] Referring to FIG. 7, the ballast area setting step (S400) may include a cutting surface setting step (S410).

[0086] The cutting surface setting step (S410) is a process of setting a cutting surface (140) that extends radially from the edge of the second curved surface to the edge of the first curved surface, and a ballast area (130) can be set through this process.

[0087] Specifically, in the cutting surface setting step (S410), the cutting angle (θ) of the cutting surface (140) can be set based on a virtual surface (VP) including the edge of the first curved surface so that the peak point (Pp) of the thickest part (Tp) of the lens thickness is formed in the ballast area (130).

[0088] In other words, the cutting angle (θ) of the cutting surface (140) can be set so that the peak point (Pp) of the thickest part (Tp) of the lens body (100) is located at the edge of the lower eyelid (LE).

[0089] For example, the cutting plane setting step (S410) may set the cutting plane using statistical information (e.g., a thesis, etc.) on the lower eyelid (LE), or using a measurement value directly measured by a specific user or multiple users, or an average value of the measurement values.

[0090] Accordingly, the cutting surface setting step (S410) may include a lower eyelid upper boundary measurement step (S411) for measuring the upper boundary of the lower eyelid of a specific user or multiple users, and a peak point location selection step (S412) for selecting a location for a peak point (Pp) of the thickest part (Tp) based on the measured upper boundary of the lower eyelid or multiple average values.

[0091] The contact lens for correcting astigmatism and its design method according to the present invention have been described above. Those skilled in the art will readily appreciate that the technical configuration of the present invention can be implemented in other specific forms without altering the technical spirit or essential features of the present invention.

[0092] Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting.

[0093] (Explanation of symbols)

[0094] EB: eyeball LE: lower eyelid

[0095] UE: Upper eyelid

[0096] 100: Lens body 110: Inner side

[0097] 120: Outer surface 130: Ballast area

[0098] 140: Cutting surface

[0099] The present invention can be utilized in the field of contact lenses, particularly in the field of astigmatism correction contact lenses, as well as in similar or related fields, and can improve reliability and competitiveness in the relevant fields.

Claims

1. The inner surface of the lens body is formed as a first curved surface extending radially from the center, At least a portion of the outer surface of the lens body is formed as a second curved surface extending radially from the center, The above lens body is, In the plan view of the above lens body, the center of the first curved surface and the center of the second curved surface are formed to be misaligned with each other, In the plan view of the lens body, on an imaginary line connecting the center of the first curved surface and the center of the second curved surface, a ballast area is formed that includes a part with the thickest lens thickness on the opposite side to the center of the first curved surface based on the center of the second curved surface. The thickest part of the lens is It is characterized in that the lower border of the upper eyelid and the upper border of the lower eyelid are formed so that they do not pass through the corresponding part when the user performs a squint movement while wearing contact lenses. Contact lenses for correcting astigmatism.

2. In paragraph 1, The thickest part of the lens is In the plan view of the lens body, it is characterized in that it is formed at a position 1.2 mm to 2.6 mm away from the edge of the first curved surface toward the center of the first curved surface. Contact lenses for correcting astigmatism.

3. In paragraph 1, The above lens body is, In the plan view of the lens body, the distance between the center line of the first curved surface and the center line of the second curved surface is formed to be 0.05 mm to 0.35 mm. Contact lenses for correcting astigmatism.

4. In paragraph 1, The above lens body is, It includes a cutting surface extending radially from the edge of the second curved surface to the edge of the first curved surface, The thickest part of the lens is In the plan view of the lens body, it is characterized in that it is formed at the intersection of the largest part of the cutting surface, the imaginary straight line passing through the center of the first curved surface, and the edge of the second curved surface. Contact lenses for correcting astigmatism.

5. An inner curve setting step of setting the inner surface of the lens body as a first curved surface extending radially from the center; An outer curve setting step of setting the outer surface of the lens body as a second curved surface extending radially from the center; In the plan view of the lens body, an inner and outer side position setting step for setting the positions of the inner and outer sides by making the center of the first curved surface and the center of the second curved surface misalign with each other; and A method for setting a ballast area, comprising: a ballast area setting step for setting a ballast area including the thickest part of the lens based on the position where the lower eyelid and the upper eyelid meet during a squint movement, based on the user's optometry information or optometry statistical information for multiple astigmatism correctors; characterized in that it includes; Method for designing a contact lens for correcting astigmatism.

6. In paragraph 5, The above ballast area setting step is, In a plan view of the lens body, the thickest part of the lens is set at a position 1.2 mm to 2.6 mm away from the edge of the first curved surface toward the center of the first curved surface. Method for designing a contact lens for correcting astigmatism.

7. In paragraph 5, At least one of the inner curve setting step and the outer curve setting step is Characterized in that the surface is set based on optometry information including the user's ocular curvature and astigmatism status. Method for designing a contact lens for correcting astigmatism.

8. In paragraph 5, The above ballast area setting step is, A cutting surface setting step for setting a cutting surface extending radially from the edge of the second curved surface to the edge of the first curved surface; The above cutting surface setting step is, Characterized in that the cutting angle of the cutting surface is set based on a virtual surface including the edge of the first curved surface so that the thickest part of the lens thickness is formed in the ballast area. Method for designing a contact lens for correcting astigmatism.

Images