Optimized back surface for toric contact lenses

Abstract

The invention provides a method for improving a reference group of a soft toric contact lens, an improved toric contact lens group and an improved toric lens. The method involves identifying geometric characteristics of the reference lens including at least a target spherical power, a radius of curvature of a rear surface of the peripheral region, a lens center thickness, a lens material refractive index, an optical region diameter, and an outer diameter of the transition region; identifying a reference meridian of a reference group of toric lenses; reducing the slope deviation along the reference meridian by adjusting the sag and radius of curvature of the peripheral region, and / or increasing the outer diameter of the transition region; the improved lens set is produced by applying the adjusted sag and radius of curvature and / or the increased outer diameter of the transition region to all lenses within the improved lens set.

Description

Field of the Invention

[0001] This application relates to the field of ophthalmic lenses for use by astigmatic patients. More specifically, this application relates to an optimized posterior surface design for a class of toric contact lenses. Background Art

[0002] Myopia or nearsightedness is an optical or refractive defect of the eye in which light from an image focuses into a point before it reaches the retina. Myopia is typically caused by an eyeball or globe that is too long or a cornea that is too steep. Myopia can be corrected using spherical lenses with a negative or minus optical power. Hyperopia or farsightedness is an optical or refractive defect of the eye in which light from an image focuses into a point after or behind the retina. Hyperopia is typically caused by an eyeball or globe that is too short or a cornea that is too flat. Hyperopia can be corrected using spherical lenses with a positive or plus optical power.

[0003] Astigmatism is an optical or refractive defect in which an individual's vision is blurred because the eye is unable to focus a point target into a focused image on the retina. Corneal astigmatism is caused by a non-rotationally symmetric curvature of the cornea. A normal cornea is spherical, while in an individual with corneal astigmatism, the cornea is not spherical. In other words, the cornea is more curved or steeper in one direction than in the other, such that the image is stretched out into two focal lines rather than being focused into a single point. Astigmatism can be corrected using cylindrical lenses rather than spherical lenses.

[0004] Corneal astigmatism can be corrected using rigid or rigid gas-permeable contact lenses. In this case, a fluid or tear lens can exist between the posterior surface of the rigid contact lens and the cornea. This fluid or tear lens conforms to or takes on the shape of the back surface of the contact lens. Since the refractive index of the fluid or tear lens nearly matches that of the cornea, the corneal scatter rate can be optically cancelled or reduced. In this case, a toric lens would not be needed. However, rigid gas-permeable contact lenses and hard contact lenses are generally less comfortable than soft or hydrogel contact lenses. Since soft or hydrogel contact lenses wrap around the cornea, generally no fluid lens exists and the tear film is more closely analogous to a thin film. In this case, a toric lens design is needed.

[0005] A toric lens is an optical element that has two different optical powers in two mutually perpendicular orientations. In essence, a toric lens has a sphere for correcting myopia or hyperopia with one optical power built into a single lens and a cylinder for correcting astigmatism with another optical power. These optical powers are produced using curvatures oriented at different angles, and the orientations must be maintained relative to the eye. Accordingly, a toric contact lens also includes a mechanism for relatively stably holding the contact lens on the eye when the wearer blinks or looks around.

[0006] The maintenance of the rotational, on-eye orientation of a toric contact lens can be achieved by well-known mechanical means, such as ballasting, circum-ballasting, or dual stabilizing zones, the latter of which is described in U.S. Patent No. 11,281,024, which is incorporated herein by reference.

[0007] The front surface of the toric lens typically bears stabilizing features that provide rotational stability of the lens on the eye. The back surface of the lens is typically torically corrected. This is a common approach among soft contact lens manufacturers as it provides manufacturability benefits and allows for the generation of multiple SKUs with a minimum number of tools, especially when the manufacturing process relies on injection molding.

[0008] The back surface geometry of the contact lens is a critical aspect of the lens as it directly contacts the corneoscleral surface of the eye. Thus, it is desirable to optimize the back surface design relative to the shape of the cornea to minimize contact pressure and thereby avoid corneal staining, abrasion, wear, etc. In addition to being optimized for a particular level of cylindrical power correction, what is needed is a back surface design for a set of toric contact lenses in which the contact pressure in the corneal region is minimized across the entire range of standard commercially available cylindrical power lenses and / or in which the difference in contact pressure between the lowest and highest cylindrical power lenses is reduced. SUMMARY OF THE INVENTION

[0009] Provided herein is a method for improving a reference set of soft toric contact lenses. Each lens in the reference set of lenses includes a front surface and a back surface that is disposed opposite the front surface and adapted to be placed against a user's eye. The front surface and the back surface meet at a lens edge and define a lens diameter. Each lens also includes an optical zone in a central region of the lens that surrounds the lens center and has an optical zone diameter. At least within the optical zone, the back surface includes a spherical meridian that defines the spherical power of the lens and a cylindrical meridian that defines the cylindrical power of the lens within a predetermined range of cylindrical powers. The lens also includes a peripheral zone that extends to the lens edge in a peripheral region of the lens and a transition zone that extends between the optical zone and the outer zone. The method for improvement can include the steps of

[0010] identifying geometric characteristics of a target lens within the reference set of lenses, the geometric characteristics including at least a target spherical power, a radius of curvature of the back surface of the peripheral zone, a lens center thickness, a lens material refractive index, an optical zone diameter, and an outer diameter of the transition zone; identifying a reference meridian of the reference set of toric lenses, reducing a slope deviation along the reference meridian by adjusting the sag and radius of curvature of the peripheral zone and / or increasing the outer diameter of the transition zone, and creating an improved set of lenses by applying the adjusted sag and radius of curvature and / or the increased outer diameter of the transition zone to all lenses within the improved set of lenses.

[0011] The reference meridian can be selected from the group consisting of: a meridian having an intermediate cylindrical power corresponding to the predetermined range of cylindrical power, a meridian having half of the maximum cylindrical power within the predetermined range of cylindrical power, or a meridian having a median radius of curvature between the radius of curvature of the spherical meridian and the radius of curvature of the cylindrical meridian for the maximum cylindrical power within the range of cylindrical power.

[0012] In one embodiment, the total slope deviation range along the posterior surface of the improved lens group is reduced compared to the total slope deviation range along the posterior surface of the reference lens group. In the improved lens group compared to the reference lens group, the difference between the magnitude of the negative slope deviation range and the magnitude of the positive slope deviation range within the total slope deviation range can be reduced.

[0013] Furthermore, the maximum corneal pressure of the improved lens group can be less than the maximum corneal pressure of the reference lens group.

[0014] According to various embodiments, the maximum corneal pressure difference of the lenses within the improved lens group can be 0.2 kPa, the lens diameter can be from 14.0 mm to 14.6 mm, and / or the optical zone diameter can be approximately 9 mm.

[0015] According to other various embodiments, the radius of curvature of the spherical meridian and the target spherical power of the reference lens can be 8.35 mm to 8.45 mm and -3.0 D, respectively.

[0016] The refractive index of the reference lens can be 1.42, and the central thickness of the reference lens can be 80 microns.

[0017] This document also provides a toric contact lens group for a predetermined range of cylindrical power. Each lens in the group includes a front surface, a rear surface disposed opposite the front surface and adapted to be placed against the user's eye, wherein the front surface and the rear surface meet at the lens edge and define the lens diameter. Each lens further includes an optical zone in the central region of the lens surrounding the lens center, a peripheral zone in the peripheral region of the lens extending to the lens edge, and a transition zone extending between the optical zone and the peripheral zone. The rear surface includes a spherical meridian defining the power of the lens and a cylindrical meridian defining the cylindrical power of the lens within the optical zone, as well as the radius of curvature of the spherical meridian. Each lens in the lens group has an outer diameter of 14.0 mm to 14.6 mm, an outer diameter of the transition zone greater than 13.3 mm, and a sag of the peripheral region less than 0.70 mm.

[0018] The toric lens group may have a maximum corneal pressure difference of less than 0.2 kPa for all lenses within the lens group. Each lens in the group may also have an outer diameter of the optical zone of approximately 9 mm, and / or each lens in the group may have a posterior surface radius of from 8.35 mm to 8.45 mm.

[0019] Also provided herein is a toric contact lens group for a predetermined range of cylindrical powers, wherein each lens in the group includes a front surface, a rear surface disposed opposite the front surface and adapted to be placed against a user's eye, and wherein the front surface and the rear surface meet at a lens edge defining a lens diameter. Each lens further includes an optical zone in a central region of the lens surrounding the lens center, a peripheral zone in a peripheral region of the lens extending to the lens edge, and a transition zone extending between the optical zone and the peripheral zone. The rear surface includes a spherical meridian defining the power of the lens and a cylindrical meridian defining the cylindrical power of the lens within the optical zone, and a radius of curvature of the spherical meridian. The area of the transition zone of the toric contact lens is greater than 46% of the total area of the toric contact lens.

[0020] According to various embodiments, the maximum corneal pressure difference of all lenses within the lens group can be less than 0.2 kPa, the outer diameter of the optical zone of each lens can be approximately 9 mm, the posterior surface radius of each lens can be from 8.35 mm to 8.45 mm, and / or for each lens, the area of the transition zone of the toric contact lens can be from about 46% to 55% of the total area of the toric contact lens.

[0021] Also provided is a toric contact lens, which includes a front surface, a rear surface disposed opposite the front surface and adapted to be placed against a user's eye, and wherein the front surface and the rear surface meet at a lens edge defining a lens diameter. The toric contact lens further includes an optical zone in a central region of the lens surrounding the lens center, a peripheral zone in a peripheral region of the lens extending to the lens edge, and a transition zone extending between the optical zone and the peripheral zone. The rear surface includes a spherical meridian defining the power of the lens and a cylindrical meridian defining the cylindrical power of the lens within the optical zone, and a radius of curvature of the spherical meridian. The toric contact lens has an outer diameter of from 14.0 mm to 14.6 mm, an outer diameter of the transition zone greater than 13.3 mm, and a sag of the peripheral region less than 0.70 mm.

[0022] The range of the cylindrical power of the lens can be from -0.75 D to -2.75 D. The maximum corneal pressure difference of the lens can be less than 0.2 kPa. Additionally, the outer diameter of the optical zone can be approximately 9 mm, and / or the posterior surface radius of the lens can be from 8.35 mm to 8.45 mm.

[0023] In addition, a toric contact lens is provided, which includes a front surface, a rear surface disposed opposite to the front surface and adapted to be placed against the user's eye, wherein the front surface and the rear surface meet at a lens edge defining the lens diameter. The toric contact lens further includes an optical zone in a central region of the lens surrounding the lens center, a peripheral zone in a peripheral region of the lens extending to the lens edge, and a transition zone extending between the optical zone and the peripheral zone. The rear surface includes a spherical meridian defining the refractive power of the lens and a cylindrical meridian defining the cylindrical refractive power of the lens in the optical zone, as well as the radius of curvature of the spherical meridian. The area of the transition zone of the toric contact lens is greater than 46% of the total area of the contact lens.

[0024] According to an alternative embodiment, the cylindrical refractive power of the lens can be in the range of -0.75D to -2.75D, and the maximum corneal pressure difference of the lens can be less than 0.2 kPa. In addition, the outer diameter of the optical zone can be approximately 9 mm, the back surface radius of the lens can be 8.35 mm to 8.45 mm, and / or the area of the transition zone of the toric contact lens can be about 46% to 55% of the total area of the toric contact lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other features and advantages of the present invention will become apparent from the following more particular description of the preferred embodiments of the invention as illustrated in the accompanying drawings.

[0026] Figure 1 An exemplary toric soft contact lens is illustrated, which has a dual stabilization zone for providing rotational stability of the lens on the eye;

[0027] Figure 2 is a flow chart illustrating an exemplary process for designing an optimized lens as described herein;

[0028] Figure 3 shows the back surface slope deviation of a reference 14.30 mm soft toric contact lens to be improved as described herein;

[0029] Figure 4 Illustrate Figure 3 the linear relationship between the cylindrical correction of the lens and the radius of curvature along the cylindrical meridian;

[0030] Figure 5 shows the back surface slope deviation of an exemplary embodiment of an improved 14.30 mm lens according to the present invention;

[0031] Figures 6 to 7 Illustrates the pressure map of the lens of Table 1 herein;

[0032] Figures 8 to 9 Illustrates the pressure map of the lens of Table 2 herein;

[0033] Figure 10 Illustrates an exemplary toric soft contact lens having a ballast type stabilization zone design for providing rotational stability of the lens on the eye;

[0034] Figure 11 Shows the back surface slope deviation of another 14.00 mm reference soft toric contact lens to be improved as described herein;

[0035] Figure 12 Shows the back surface slope deviation of another embodiment of an improved 14.00 mm lens according to the present invention;

[0036] Figure 13 Shows the back surface slope deviation of another reference 14.60 mm soft contact lens to be improved as described herein; and

[0037] Figure 14 Shows the back surface slope deviation of another embodiment of an improved 14.60 mm lens according to the present invention. DETAILED DESCRIPTION

[0038] As described above, the back surface geometry of a contact lens is a critical aspect of the lens as it directly contacts the surface of the eye. For toric lenses, due to the large number of SKUs, these lenses typically have only one base curve, as opposed to the two or more base curves typically provided for spherical lenses, and allows the practitioner to better optimize the fit of the lens on a given patient's eye. For toric lenses, since only one base curve is provided, the radius along the spherical meridian is selected to provide a good fit across the population, for example 8.45 mm.

[0039] For any contact lens, vision correction is driven by the refractive index of the lens material, the center thickness of the lens, and the geometry of the front and back surfaces in the central viewing area of the lens. Typically, the radial geometry of the lens is defined by three different regions or zones. The inner region or zone is the optical zone that provides vision correction, the outer or peripheral region or zone is the lens area that provides mechanical stability of the lens on the eye, and the intermediate or transition region or zone between the optical zone and the peripheral zone blends the two regions together. Discontinuities between these regions can affect comfort or otherwise cause unwanted optical effects such as scattering.

[0040] There are multiple ways to produce the optical zone of the back surface that provides cylindrical correction. The two most common are toric and aspheric (also described as non-spherical toric). The general mathematical descriptions of such surfaces are defined below, where Equation 1 describes a toric surface and Equation 2 describes an aspheric surface:

[0041]

[0042] where Z (the sagittal value), x, and y are the coordinates of the surface in a Cartesian coordinate system, and C X = 1 / R x 、C y = 1 / R y ,R x and R y are the apical radii along the X and Y axes, and k X and k y are the conic constants with respect to the X and Y axes. For clarity, spherical power correction is conventionally established along the X axis, while cylindrical correction is established along the Y axis. This convention will be applied herein.

[0043] The peripheral region of the posterior surface of a toric lens is typically spherical and is typically rotationally symmetric about the optical axis. In some cases, the posterior surface of the peripheral region can be more complex, such as aspherical.

[0044] The present invention provides an optimized posterior surface design that, compared to existing designs, achieves reduced contact pressure on lenses across a predetermined range of cylindrical powers. The present invention also provides a system and method for designing such lenses to achieve such improvements compared to a reference group of known lenses.

[0045] Now referring to Figure 1 , as described above, an exemplary lens 100 that can be optimized according to the present invention has an inner optical zone 101 and a peripheral zone 102 that includes stabilizing features 104. In the illustrated embodiment, the stabilizing design includes a dual stabilizing zone 104, although any stabilizing zone design can be used. Although its boundaries are not explicitly illustrated in Figure 1 , there is a transition zone 103 between the optical zone and the peripheral zone that is designed to blend the two together. The transition zone is defined as a spline that provides surface continuity in terms of sag and slope.

[0046] Figure 1 The posterior surface of a lens or lens group of the illustrated type can be optimized according to the present disclosure to reduce corneal pressure across a predetermined range of cylindrical powers. As a first step 201( Figure 2 ), identify the geometric characteristics of the lens to be optimized. Table 1 below describes Figure 1 the posterior surface geometric characteristics of a known toric contact lens of the illustrated type that has a dual stabilizing zone and that serves as a starting point in the optimization method described herein.

[0047] Posterior surface

[0048] Description Radius Diameter Shape (K) Sag X-Ctr Z-Ctr X-End Radius of spherical meridian 8.450 9.00 0.000 1.298 0.000 8.525 4.500 Radius of cylindrical meridian (-0.75D) 8.325 9.00 0.000 1.321 0.000 8.400 4.500 Radius of cylindrical meridian (-2.75D) 8.009 9.00 0.000 1.384 0.000 8.084 4.500 Blend region Spline 11.80 ------ Vary with cylinder ----- ----- 5.900 Peripheral region 8.500 14.30 0.000 1.504 0.038 8.634 7.152

[0049] Table 1

[0050] The radius of curvature along the spherical meridian is 8.45 mm, the target spherical power correction is -3.0 D, the lens center thickness is 80 microns, and the refractive index of the lens material is 1.42. The diameter of the optical zone is 9.0 mm, the outer diameter of the lens is 14.3 mm, and the initial diameter of the outer edge of the transition zone is 11.80 mm. Then identify the predetermined range of cylindrical power to be provided at 202, which in this embodiment is from -0.75 D to -2.75 D. Those skilled in the art will readily recognize that once the refractive index of the material, the center thickness, the target spherical power (-3.0 D), and the radius of curvature along the spherical meridian (8.45 mm) are established, any ray-tracing method can be used to determine 203 the back radius along the cylindrical meridian of the lens to be optimized. In this embodiment, the front surface geometry includes a dual-stable zone with a maximum radial thickness of 375 microns that remains constant, although other variations can be incorporated, including designs with thickness differences that vary according to the cylindrical power, such as, for example, as described in U.S. Patent No. 10,739,617, which is hereby incorporated by reference in its entirety.

[0051] Starting from these geometric properties of the reference lens within the group to be optimized, the next step in the optimization method is to select a reference meridian 204 on the back surface. The reference slope is defined as the surface slope calculated along this reference meridian for which the back surface will be optimized. The reference meridian can be selected as the meridian that carries the intermediate cylindrical power corresponding to the cylindrical range for which the surface is being optimized. For example, if the cylindrical range to be optimized is from -0.75 D to -2.75 D, the reference meridian can be the meridian that carries a -1.75 D cylindrical power. Alternatively, the reference meridian can be selected as the meridian that carries half of the maximum target cylindrical power (i.e., -1.375 D if the maximum target cylindrical power is -2.75 D). The reference meridian can alternatively be selected as the meridian that carries the average radius between the radius of curvature along the spherical power meridian and the radius of curvature along the maximum target cylindrical power.

[0052] If the posterior optical zone is defined by a more complex aspheric surface, the radius of curvature along a given meridian can be replaced by an equivalent radius defined by a circle of radius R fitted through three points of the lens diameter cross-section. These three points are the sagittal vertex at the lens center and the two endpoints of the chord on which the sagittal measurement (Z) is made.

[0053] Once a reference meridian is selected, it is optimized to minimize or balance the slope discontinuities between the optical zone and the transition zone and between the transition zone and the peripheral zone (step 205). Minimization or balancing is achieved by (1) adjusting the sag and radius of curvature in the outer peripheral zone, and / or (2) increasing the width of the transition zone. The wider the transition zone, the smoother the transition between the optical zone and the peripheral zone.

[0054] For a lens group within a predetermined range of cylindrical powers, the discontinuity will increase with increasing cylindrical correction because the curvature becomes steeper along the cylindrical meridian. The slope deviations calculated for lenses having the geometric properties listed in Table 1 are shown in Figure 3 Slope deviation is defined as the difference in surface slope between the spherical meridian and the cylindrical meridian calculated from the geometric center of the lens to the lens edge. As shown in Figure 3 The slope deviation increases linearly from the lens center towards the edge of the optical zone, reaching a maximum value of 2.0 degrees for -2.75 D of cylindrical correction. The slope deviation is opposite in the middle or blending region, reaching a maximum value of approximately -4.0 degrees for -2.75 D of cylindrical correction, and then dropping to zero in the outer region of the periphery because the geometry of this region together with the circumference of the lens remains the same over the entire cylindrical range. For the purposes of this application, a positive slope deviation refers to a slope deviation with a positive value, and the maximum positive slope deviation is the maximum positive slope deviation value (i.e., 2.0 in this case). Similarly, a negative slope deviation refers to a deviation with a negative value, and the maximum negative deviation is the maximum negative slope deviation value (i.e., -4.0 in this case).

[0055] As noted, these discontinuities and / or slope deviations can be minimized by adjusting the sag and radius of curvature of the peripheral zone along the selected reference meridian, increasing the width of the transition region, or a combination thereof, where the selected reference meridian has been chosen in this embodiment to be the meridian at the middle (-1.75 D) of the cylindrical range. In this exemplary embodiment, the sag and radius of curvature of the peripheral zone are adjusted to 0.67 mm and 8.65 mm, respectively, and the outer diameter of the transition zone is increased to 13.30, as shown in Table 2 below.

[0056] Back surface

[0057] Description Radius Diameter Shape (K) Sag X-Ctr Z-Ctr X-End Radius of spherical meridian 8.450 9.00 0.000 1.298 0.000 8.525 4.500 Radius of cylindrical meridian (-0.75D) 8.325 9.00 -0.036 1.317 0.000 8.707 4.500 Radius of cylindrical meridian (-2.75D) 8.009 9.00 -0.124 1.366 0.000 9.213 4.500 Blend region Spline 13.30 ------ Vary with cylinder ----- ----- 6.650 Peripheral region 8.6560 14.30 0.000 0.667 0.000 8.847 7.152

[0058] Table 2

[0059] Since as Figure 4The strong linear relationship between the radius of curvature along the cylinder meridian and the corresponding built-in astigmatism correction shown in the embodiment, the optimized reference meridian will be nearly the same regardless of whether the reference meridian is chosen as the reference meridian that bears half of the maximum target cylinder or the reference meridian that is chosen as the median radius between the radius of curvature along the spherical power meridian and the radius of curvature along the maximum target cylinder power. The former results in a radius of curvature of 8.224 mm, and the latter results in a radius of curvature of 8.229 mm. If the back surface geometry across the target cylinder range does not have a linear relationship with the radius of curvature (i.e., a more complex geometry, such as a freeform surface designed to correct higher-order aberrations), then the results from these two methods can show a greater difference. In this case, the radius of curvature can be replaced by the equivalent radius of curvature along the cylinder meridian.

[0060] The slope deviations of the geometries listed in Table 2 are shown in Figure 5 In it. As shown, the slope deviation increases linearly from the lens center to the edge of the optical zone, reaching a maximum value of approximately 1.25 degrees for

[0061] -2.75 D cylinder correction. For -2.75 D cylinder correction, the slope deviation reverses to reach a maximum value of approximately -2.0 degrees in the transition zone and then eases to zero in the peripheral zone of the lens because the geometry in this region along the lens circumference remains the same across the entire cylinder range. Due to the aspherization of the posterior optical zone, the increase in the transition zone width, and the selection of the -1.75 D cylinder meridian as the optimized reference meridian, the back surface geometry of the lens defined in Table 2 significantly reduces the slope deviation. In the provided embodiment, the back surface geometry balances the range of slope deviations in the transition zone such that the maximum negative deviation and the maximum positive deviation do not differ much. Preferably, the maximum negative deviation will be less in magnitude than the maximum positive deviation, but this may not always be possible for all lens geometries (i.e., optical zone diameter and maximum target cylinder power).

[0062] As shown in Table 2, the introduction of aspherization along the cylinder meridian (non-zero K value along the cylinder meridian) reduces the surface curvature, resulting in a smaller slope deviation at the optical zone-transition zone boundary.

[0063] Another benefit of the aspherization of the cylinder meridian in the posterior optical zone is that it can reduce secondary astigmatism, which is the result of the difference in spherical aberration along the spherical and cylinder meridians. As detailed in U.S. Patent Application No. 2019 / 0064543, reducing secondary astigmatism can improve vision, and this document is incorporated herein by reference in its entirety.

[0064] As part of the optimization method, the new design is then evaluated to determine the contact pressure in the corneal region of the lens when wrapped around the eye using a finite element analysis (FEA) model (step 206). The FEA model simulates the wrapping of the soft contact lens on the eye and provides a contact pressure map as the output for any given lens cylinder power. FEA models of the wrapping of soft contact lenses with reference (Table 1) and optimized (Table 2) designs on rigid surfaces of two average eye geometries at low (-0.75 D) and high (-2.75 D) cylinder levels were developed, and the lens-eye contact pressures were calculated. A wrapping pressure of 0.2 kPa, an elastic modulus of 660 kPa, a Poisson's ratio of 0.244, and quarter-symmetry or half-symmetry fixed boundary conditions were respectively assumed for the models used for the dual-stabilization zone or ballast-type stabilization zone designs. Appropriate boundary conditions at the symmetry plane prevent the lens from being eccentric on the eye surface such that the center of the lens is aligned with the apex of the cornea during the entire wrapping deformation. Table 3 below summarizes the eye geometries defined for the rigid eye model:

[0065]

[0066]

[0067] Table 3

[0068] Figure 6 、 Figure 7 、 Figure 8 and Figure 9 respectively show the pressure map outputs of the lenses defined in Table 1 with -0.75 D cylinder power and -2.75 D cylinder power, and the pressure map outputs of the lenses defined in Table 2 with the same cylinder powers.

[0069] Table 4 below shows the maximum corneal pressure and maximum corneoscleral pressure determined by FEA for the reference lens defined in Table 1 above and the improved design defined in Table 2 above at the low end (-0.75 D) and high end (-2.75 D) of the cylinder range. As shown, for the highest cylinder correction, the maximum corneal pressure (CP) is reduced from 1.51 kPa to 0.70 kPa, and for the highest cylinder correction, the maximum corneoscleral pressure (CSP) range remains below 1.40 kPa. In addition to reducing the maximum pressure across the cylinder range, the improved lens also reduces the contact pressure difference between the lowest cylinder power lens and the highest cylinder power lens. For example, as shown below, the corneal pressure difference of the lens in Table 2 has been reduced from 0.95 kPa (1.51 - 0.56) to 0.1 kPa (0.80 - 0.70), and the corneoscleral pressure difference has been reduced from 0.17 kPa to 0.04 kPa.

[0070] It is noted that in the improved lens, the outer diameter of the transition zone has increased from 11.8 to 13.3, and since the outer diameter of the lens and the outer diameter of the optical zone remain the same, this represents an increase in the area of the transition zone relative to the area of the entire lens from 28.5% to 46.9%.

[0071]

[0072] Table 4

[0073] Table 4 also shows similar results for a known ballasted toric lens of the type shown in Table 1 above compared to the same lens having the geometric properties shown in Table 2. The maximum thickness of the ballast region is set to the same value as that used for the double-stabilization zone example. As shown in Table 4, when optimized according to the present disclosure, for high-cylinder lenses, the maximum corneal contact pressure is significantly reduced (from 2.0 kPa to 1.4 kPa), while the maximum corneoscleral pressure remains at 1.80 kPa across the range of cylinder powers. Figure 10 In step 207, the output of the FEA analysis is examined. If the desired level of reduction in corneal pressure across the range of cylinder powers has not been achieved, step 205 can be repeated to further minimize the discontinuities as described above.

[0074] The following Table 5 reflects the geometric properties of another exemplary lens that can be further improved according to the present invention. Except for the geometric differences shown in Table 5, the physical properties of the lens to be optimized are the same as those described above, including a smaller diameter lens of 14.0 mm compared to 14.3 mm in the previous embodiment.

[0075] Back surface

[0076] Back surface

[0077] Description Radius Diameter Shape (K) Sag X-Ctr Z-Ctr X-End Radius of spherical meridian 8.350 9.00 0.000 1.316 0.000 8.425 4.500 Radius of cylindrical meridian (-0.75D) 8.228 9.00 0.000 1.340 0.000 8.303 4.500 Radius of cylindrical meridian (-2.75D) 7.919 9.00 0.000 1.403 0.000 7.994 4.500 Blend region Spline 11.80 ------ Vary with cylinder ----- ----- 5.900 Peripheral region 8.250 14.00 0.000 1.353 0.090 8.339 7.002

[0078] Table 5

[0079] Using the above principles and the same selected reference meridian, the sag and radius of curvature of the peripheral zone are adjusted from 1.353 mm and 8.25 mm to 0.329 mm and 11 mm respectively to minimize the slope deviation along this reference meridian. The outer diameter of the transition zone increases from 11.8 mm to 13.5 mm. The new geometry of this improved lens is shown in Table 6 below.

[0080] Back surface

[0081] Description Radius Diameter Shape (K) Sag X-Ctr Z-Ctr X-End Radius of spherical meridian 8.350 9.00 0.000 1.316 0.000 8.425 4.500 Radius of cylindrical meridian (-0.75D) 8.228 9.00 -0.035 1.335 0.000 8.603 4.500 Radius of cylindrical meridian (-2.75D) 7.919 9.00 -0.122 1.385 0.000 9.094 4.500 Blend region Spline 13.50 ------ Vary with cylinder ----- ----- 6.650 Peripheral region 11.000 14.01 0.000 0.329 -1.842 10.375 7.152

[0082] Table 6

[0083] The slope deviations of the geometries listed in Tables 5 and 6 above are shown respectively inFigure 11 and Figure 12 For the lenses of Table 5, it can be seen that the slope deviation increases linearly from the lens center to the edge of the optical zone, reaching a maximum of approximately 2 degrees for a -2.75D cylinder correction. For a -2.75D cylinder correction, the slope deviation reaches a maximum of approximately -4.0 degrees in the reverse direction in the transition zone and then decays to zero in the peripheral zone of the lens because the geometry in this region along the circumference of the lens remains the same over the entire cylinder range. Thus, for a 14.0 mm diameter lens, due to the aspherization of the posterior optical zone and the increase in the width of the transition zone, the discontinuity along the reference meridian is reduced / minimized, similarly reducing the slope deviation compared to the initial or reference lens. Additionally, as in the previous embodiment, the maximum negative slope deviation is closer to the maximum positive slope deviation.

[0084] The FEA results for the lenses of Tables 5 and 6 are shown in Table 7 below.

[0085]

[0086] Table 7

[0087] The maximum corneal pressure across the cylinder range is reduced from 1.59 kPa to 0.80 kPa, and the maximum corneoscleral pressure is reduced from 1.59 kPa to 1.36 kPa. Additionally, the difference in maximum corneal pressure between the low cylinder and high cylinder lenses is reduced from 0.74 kPa to 0.08 kPa, and the difference in maximum corneoscleral pressure is reduced from 0.11 kPa to 0.04 kPa.

[0088] Furthermore, it is noted that in the improved lenses, the outer diameter of the transition zone has increased from 11.8 to 13.5, and since the outer diameter of the lens and the outer diameter of the optical zone remain the same, this represents an increase in the area of the transition zone relative to the area of the entire lens from 29.7% to 51.7%.

[0089] The following Table 8 reflects the geometric characteristics of another embodiment of a lens that can be further improved according to the present invention. Except for the geometric differences shown in Table 8, the physical characteristics of the lens to be optimized are the same as above, including a larger diameter lens of 14.6 mm compared to 14.0 and 14.3 in the above embodiments.

[0090] Rear surface

[0091]

[0092]

[0093] Table 8

[0094] Using the above principle and the same selected reference meridian, the slope deviation along this meridian is reduced by adjusting the sag and radius of curvature of the peripheral zone from 1.753 and 8.5 to 0.373 and 12.0, respectively. The outer diameter of the transition zone is increased from 11.8 mm to 14.10 mm. The new geometry of this improved lens is shown in Table 9 below.

[0095] Rear surface

[0096] Description Radius Diameter Shape (K) Sag X-Ctr Z-Ctr X-End Radius of spherical meridian 8.450 9.00 0.000 1.298 0.000 8.525 4.500 Radius of cylindrical meridian (-0.75D) 8.325 9.00 -0.036 1.317 0.000 8.707 4.500 Radius of cylindrical meridian (-2.75D) 8.009 9.00 -0.124 1.366 0.000 9.213 4.500 Blend region Spline 14.10 ------ Vary with cylinder ----- ----- 7.050 Peripheral region 12.000 14.60 0.000 0.373 -2.766 10.753 7.302

[0097] Table 9

[0098] The slope deviations of the geometries listed in Tables 8 and 9 above are shown in Figure 13 and Figure 14 respectively. For the lens of Table 9, it can be seen that the slope deviation increases linearly from the lens center to the edge of the optical zone, reaching a maximum of approximately 1.25 degrees for -2.75 D cylinder correction. For -2.75 D cylinder correction, the slope deviation reaches a maximum of approximately -1.50 degrees in the transition zone in the reverse direction and then eases to zero in the peripheral zone of the lens because the geometry in this region along the lens circumference remains the same over the entire cylinder range. Thus, for a 14.6 mm diameter lens, due to the aspherization of the posterior optical zone and the increase in the width of the transition zone, the discontinuity along the reference meridian is reduced / minimized, similar to the initial or reference lens, which similarly reduces the slope deviation. Additionally, as in the previous embodiments, the maximum negative slope deviation is closer to the maximum positive slope deviation.

[0099] The FEA results of the lenses of Tables 8 and 9 are shown in Table 10 below.

[0100]

[0101]

[0102] Table 10

[0103] The maximum corneal pressure over the entire cylinder range is reduced from 1.36 kPa to 0.64 kPa, and the maximum corneoscleral pressure is only slightly changed at 1.83 kPa compared to 1.81 kPa. The maximum corneal pressure difference between the low cylinder lens and the high cylinder lens is reduced from 0.72 kPa to 0.08 kPa, and the maximum corneoscleral pressure difference is reduced from 0.45 kPa to 0.13 kPa.

[0104] In addition, it is noted that in the improved lens, the outer diameter of the transition zone has increased from 11.8 mm to 14.1 mm, and since the outer diameter of the lens and the outer diameter of the optical zone remain the same, this represents an increase in the area of the transition zone relative to the area of the entire lens from 27.3% to 55.2%.

[0105] Although the foregoing describes embodiments of the present invention, other and further embodiments of the present invention may be devised without departing from the basic scope thereof, which is limited only by the scope of the claims below. For example, the present invention contemplates that any feature shown in any embodiment described herein may be combined with any feature shown in any other embodiment described herein or incorporated herein by reference, and still fall within the scope of the present invention.

Claims

1. A method for improving a reference set of soft toric contact lenses, wherein each lens in the reference lens set comprises: a front surface and a back surface, the back surface being disposed opposite the front surface and adapted to be placed against an eye of a user, the front surface and the back surface meeting at a lens edge and defining a lens diameter; an optical zone in a central region of the lens about a center of the lens and having an optical zone diameter, wherein at least within the optical zone, the posterior surface includes a spherical meridian defining a spherical power of the lens and a cylindrical meridian defining a cylindrical power of the lens within a predetermined cylindrical power range; a peripheral zone in a peripheral region of the lens extending to an edge of the lens, and a transition zone extending between the optical zone and the outer zone, The method for improvement comprises the following steps: Identifying geometrical properties of a target lens within the reference lens set, the geometrical properties comprising at least a target spherical power, a radius of curvature of the back surface of the peripheral zone, a lens center thickness, a lens material refractive index, a diameter of the optical zone, and an outer diameter of the transition zone; identifying a reference meridian of the reference set of toric lenses; reducing the slope deviation along the reference meridian by adjusting the sag and the radius of curvature of the peripheral zone and / or increasing the outer diameter of the transition zone; and The improved set of lenses is produced by applying the adjusted sag and radius of curvature and / or increased outer diameter of the transition zone to all lenses within the improved set of lenses.

2. The method of claim 1, wherein the reference meridian is selected from the group consisting of: a meridian having a cylindrical power corresponding to the middle of said predetermined cylindrical power range, a meridian having half of the maximum cylindrical power within said predetermined cylindrical power range, or A meridian having a radius of curvature that is intermediate between the radius of curvature of the spherical meridian and the radius of curvature of the cylindrical meridian for the maximum cylindrical power within the range of cylindrical powers.

3. The method of claim 2, wherein the total slope deviation range along the back surface of the modified lens set is reduced compared to the total slope deviation range along the back surface of the reference lens set.

4. The method according to claim 3, wherein, compared with the reference lens group, in the improved lens group, the difference between the magnitude of the negative slope deviation range in the total slope deviation range and the magnitude of the positive slope deviation range in the total slope deviation range is reduced.

5. The method of claim 1, wherein the maximum corneal pressure of the improved lens set is less than the maximum corneal pressure of the reference lens set.

6. The method according to claim 1, wherein the maximum corneal pressure difference between the low cylindrical lens and the high cylindrical lens in the improved lens set is 0.2 kPa.

7. The method of claim 1, wherein the lens diameter is 14.0 mm to 14.6 mm.

8. The method of claim 7, wherein the optic zone diameter is approximately 9 mm.

9. The method of claim 8, wherein the radius of curvature of the spherical meridian and the target spherical power of the reference lens are 8.35 mm to 8.45 mm and -3.0D, respectively.

10. The method of claim 9, wherein the reference lens has a refractive index of 1.

42.

11. The method of claim 10, wherein the reference lens has a center thickness of 80 microns.

12. A set of toric contact lenses for a predetermined range of cylindrical powers, wherein each lens in the set comprises: a front surface, a back surface disposed opposite the front surface and adapted to be placed against an eye of a user, the front surface and the back surface meeting at a lens edge defining a lens diameter; an optical zone in a central region of the lens surrounding a center of the lens; a peripheral zone in a peripheral region of the lens extending to an edge of the lens; and a transition zone extending between the optical zone and the peripheral zone, the back surface including within the optical zone a spherical meridian defining a spherical power of the lens and a cylindrical meridian defining a cylindrical power of the lens, and a radius of curvature of the spherical meridian, Each lens in the set has an outer diameter of 14.0 mm to 14.6 mm, an outer diameter of the transition zone greater than 13.3 mm, and a sag of the peripheral region less than 0.70 mm.

13. The toric lens set according to claim 12, wherein the maximum corneal pressure difference of all lenses in the lens set is less than 0.2 kPa.

14. The set of toric lenses of claim 12, wherein each lens in the set has an optical zone outer diameter of approximately 9 mm.

15. The set of toric lenses of claim 12, wherein each lens in the set has a back curve radius of 8.35 mm to 8.45 mm.

16. A set of toric contact lenses for a predetermined range of cylindrical powers, wherein each lens in the set comprises: a front surface, a back surface disposed opposite the front surface and adapted to be placed against an eye of a user, the front surface and the back surface meeting at a lens edge defining a lens diameter; an optical zone in a central region of the lens surrounding a center of the lens; a peripheral zone in a peripheral region of the lens extending to an edge of the lens; and a transition zone extending between the optical zone and the peripheral zone, the back surface including within the optical zone a spherical meridian defining a spherical power of the lens and a cylindrical meridian defining a cylindrical power of the lens, and a radius of curvature of the spherical meridian, Wherein the area of ​​the transition zone of the toric contact lens is greater than 46% of the total area of ​​the toric contact lens.

17. The toric lens set according to claim 16, wherein the maximum corneal pressure difference of all lenses in the lens set is less than 0.2 kPa.

18. The toric lens set of claim 16, wherein each lens in the lens set has an optical zone outer diameter of approximately 9 mm.

19. The toric lens set of claim 16, wherein each lens in the lens set has a back curve radius of 8.35 mm to 8.45 mm.

20. The set of toric lenses of claim 16, wherein the area of ​​the transition zone of the toric contact lens is between about 46% and 55% of the total area of ​​the toric contact lens.

21. A toric contact lens comprising: a front surface, a back surface disposed opposite the front surface and adapted to be placed against an eye of a user, the front surface and the back surface meeting at a lens edge defining a lens diameter; an optical zone in a central region of the lens surrounding a center of the lens; a peripheral zone in a peripheral region of the lens extending to an edge of the lens; and a transition zone extending between the optical zone and the peripheral zone, the back surface including within the optical zone a spherical meridian defining a spherical power of the lens and a cylindrical meridian defining a cylindrical power of the lens, and a radius of curvature of the spherical meridian, wherein the toric contact lens has an outer diameter of 14.0 mm to 14.6 mm, an outer diameter of the transition zone greater than 13.3 mm, and a sag of the peripheral region less than 0.70 mm.

22. The toric contact lens of claim 21 wherein the cylindrical power of the lens ranges from -0.75D to -2.75D.

23. The toric contact lens of claim 21, wherein the maximum corneal pressure difference between the low cylinder lens and the high cylinder lens is less than 0.2 kPa.

24. The toric contact lens of claim 21 wherein the optic zone outer diameter is approximately 9 mm.

25. The toric contact lens of claim 21 wherein the back curve radius of the lens is between 8.35 mm and 8.45 mm.

26. A toric contact lens comprising: a front surface, a back surface disposed opposite the front surface and adapted to be placed against an eye of a user, the front surface and the back surface meeting at a lens edge defining a lens diameter; an optical zone in a central region of the lens surrounding a center of the lens; a peripheral zone in a peripheral region of the lens extending to an edge of the lens; and a transition zone extending between the optical zone and the peripheral zone, the back surface including within the optical zone a spherical meridian defining a spherical power of the lens and a cylindrical meridian defining a cylindrical power of the lens, and a radius of curvature of the spherical meridian, Wherein the area of ​​the transition zone of the toric contact lens is greater than 46% of the total area of ​​the contact lens.

27. The toric contact lens of claim 26, wherein the cylindrical power of the lens ranges from -0.75D to -2.75D.

28. The toric contact lens of claim 26, wherein the maximum corneal pressure difference between the low cylinder lens and the high cylinder lens is less than 0.2 kPa.

29. The toric contact lens of claim 26, wherein the optic zone outer diameter is approximately 9 mm.

30. The toric contact lens of claim 26, wherein the back curve radius of the lens is between 8.35 mm and 8.45 mm.

31. The toric contact lens of claim 26, wherein the transition zone of the toric contact lens has an area of ​​about 46% to 55% of the total area of ​​the toric contact lens.

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