Soft contact lenses with reduced volume change

Abstract

An ophthalmic lens is described herein. An exemplary ophthalmic lens may include a first surface. The exemplary ophthalmic lens may include a second surface disposed opposite the first surface and defining a volume of lens material between the first surface and the second surface. The ophthalmic lens may exhibit a first cylindrical power. The difference between the volume of lens material of the ophthalmic lens and the volume of lens material of the comparative lens may be minimized. The comparative lens may be substantially composed of the same lens material as the ophthalmic lens and exhibit a second cylindrical power different from the first cylindrical power.

Description

Technical Field

[0001] The present disclosure relates to ophthalmic devices and, more particularly, to ophthalmic lenses that are worn on the eyes of a patient. Background Art

[0002] Soft contact lenses, whether designed to provide simple vision correction (such as myopia or hyperopia) or more complex vision correction (such as presbyopia, astigmatism or higher-order aberration correction), are based on the law of refraction (Snell's law of refraction). The amount of correction can be determined based on a combination of the posterior optical zone geometry, the anterior optical zone geometry, the center thickness, and the material refractive index. Generally speaking, unless the lens is customized, the geometry of the posterior surface of the lens remains the same across a range of stock keeping units (SKUs) of the lens. The posterior surface (also called the base curve) can determine the fit performance. Typically, more than one base curve is available for single vision lenses due to the limited number of SKUs to be managed. Therefore, the practitioner can select the base curve that provides the best fit on a particular eye.

[0003] Lenses can be designed so that their mechanical properties remain independent of the prescribed vision correction to provide performance consistency across a range of SKUs. Provided that the desired power is obtained by changing the geometry of the front surface, this geometry change can introduce lens volume changes across the range of SKUs. For rotationally symmetric soft contact lenses, the volume change can range from 25% to 50% for SKUs ranging from -12.00D to +8.00D, or within 20% to 45% for SKUs ranging from -9.00D to +6.00D (SKU ranges are typically provided for most toric products). Typically, the spherical power range provided for toric products is smaller than that provided for single vision lenses due to the large number of SKUs to be managed according to multiple cylindrical power and cylindrical axis combinations. The maximum volume can be observed for extreme SKUs such as high negative lenses (lenses with spherical power below -6.0D) and high positive lenses (lenses with spherical power above +6.0D). For low power lenses, such as lenses of approximately plano-spherical power, the minimum volume occurs.

[0004] Lens volume may be initially driven by lens material properties and more specifically material stiffness. A lens made with a stiffer material may exhibit the same stiffness properties as a lens with a softer material using a thinner thickness profile. Thus, for the same SKU, base curve, and diameter combination, a lens made with a stiff material may exhibit a smaller lens volume than a lens made with a soft material. However, within the same SKU range, a lens made with a stiff material may exhibit a greater volume variation than a lens made with a soft material. Lens volume may also be driven by a base curve and diameter combination. A lens with a larger diameter and a stepped base curve may have a larger volume.

[0005] Soft toric contact lenses may present less volume variation across the associated SKU range within a given cylindrical correction. Whether the stabilization zone is a ballasted type or a bi-stable zone, the thick zone used to angle stabilize the lens on the eye can add material to the lens. For a given cylindrical correction, the geometric changes in the optical zone represent a smaller volume change than the total lens volume, thereby reducing the total volume change. However, if different levels of cylindrical correction are considered and the cylinder can be provided in 0.50D steps from -0.50D to -2.50D or in 0.50D steps from -0.75D to -2.75D, the lens volume variation can increase significantly, similar to what is seen in rotationally symmetric lenses.

[0006] For many years, soft contact lenses have been used for the sole purpose of vision correction, such as correction of myopia, hyperopia, presbyopia, astigmatism correction, or correction required for disease-related vision loss (like keratoconus). Recently, the use of soft contact lenses has expanded for purposes other than vision correction, such as cosmetic lenses (e.g., tinted lenses), filter lenses (e.g., photochromic lenses, blue blocking lenses, etc.), or to provide health benefits (e.g., allergies, dry eyes, etc.).

[0007] Such diversity in soft contact lens uses can introduce new constraints in the design, and more specifically constraints related to lens volume, which can affect lens performance. Soft toric contact lenses, which typically have a larger volume than rotational soft spherical contact lenses, may not be able to maintain lens performance for such new uses.

[0008] Therefore, improvements are needed. Summary of the invention

[0009] Ophthalmic lenses are described herein. An exemplary ophthalmic lens may include a first surface. An exemplary ophthalmic lens may include a second surface disposed opposite the first surface and defining a volume of lens material between the first surface and the second surface. The ophthalmic lens may exhibit a first cylindrical power. A difference between a volume of lens material of the ophthalmic lens and a volume of lens material of a comparative lens may be minimized. The comparative lens may be substantially composed of the same lens material as the ophthalmic lens and exhibit a second cylindrical power different from the first cylindrical power.

[0010] Methods are described herein. An exemplary method may include forming a first ophthalmic lens having a first front surface and a first back surface, the first back surface being disposed opposite the first front surface and defining a first volume of lens material between the first front surface and the first back surface. The first ophthalmic lens may exhibit a first cylindrical power. An exemplary method may include forming a second ophthalmic lens having a second front surface and a second back surface, the second back surface being disposed opposite the second front surface and defining a second volume of lens material between the second front surface and the second back surface. The second ophthalmic lens may exhibit a second cylindrical power different from the first cylindrical power. The difference between the first volume of lens material and the second volume of lens material may be independent of the difference between the first cylindrical power and the second cylindrical power.

[0011] Methods are described herein. Another exemplary method may include forming a first ophthalmic lens having a first front surface and a first back surface, the first back surface being disposed opposite the first front surface and defining a first volume of lens material between the first front surface and the first back surface. The first ophthalmic lens may exhibit a first cylindrical power. Another exemplary method may include forming a second ophthalmic lens having a second front surface and a second back surface, the second back surface being disposed opposite the second front surface and defining a second volume of lens material between the second front surface and the second back surface. The second ophthalmic lens may exhibit a second cylindrical power different from the first cylindrical power. The difference between the first volume of lens material and the second volume of lens material may be minimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The following drawings illustrate various examples discussed in the present disclosure generally by way of example and not by way of limitation. In the drawings:

[0013] Figure 1 An exemplary graph showing lens volume using a standard toric lens covering an ASD-type stabilization zone ranging from -9.00D to +6.00D Rx, with cylindrical correction varying from -0.75D to -2.75D, is shown.

[0014] FIG. 2A to FIG. 2C An exemplary contour plot of a soft toric contact lens using bi-stable zones as a means of maintaining angular orientation on the eye is shown.

[0015] Figure 3 An exemplary graph showing the lens volume for a standard single vision lens covering the -12.00D to +8.00D Rx range is shown.

[0016] Figure 4An exemplary toric contact lens is shown in which the thickness profile along the vertical meridian decreases as the prescribed cylinder increases. The thickness profile along the horizontal meridian remains constant.

[0017] Figure 5 An exemplary graph showing the volume of a toric lens designed such that the volume is independent of the amount of cylinder specified is shown.

[0018] Figure 6 An exemplary toric contact lens is shown in which the geometry of the posterior surface is adjusted according to a prescribed amount of cylinder. The anterior surface geometry remains unchanged.

[0019] Figure 7 Exemplary box plot representations of lens volume changes for the provided examples are shown for single vision and toric soft contact lenses.

[0020] Figure 8 An example of a single vision lens is shown in which the volume variation has been reduced across the -12.0D to +8.0D SKU range. DETAILED DESCRIPTION

[0021] Systems and methods for manufacturing contact lenses are described herein. Using the systems and / or methods described herein, a volume range of contact lenses can be maintained regardless of the prescription strength of each contact lens. Each contact lens can include a front surface and a back surface. A first contact lens can include a first prescription strength, a first geometry associated with the first front surface, a first geometry associated with the first back surface, and a first volume. The first volume can be associated with a first material. The first contact lens can include a first material.

[0022] The second contact lens may include a second prescription strength, a second geometry associated with the second anterior surface, a second geometry associated with the second posterior surface, and a second volume. The second volume may be associated with a second material. The second contact lens may include a second material. The first prescription strength may be different from the second prescription strength. The second geometry associated with the second anterior surface may be altered from and based on a first geometry associated with the first anterior surface. The second geometry associated with the second posterior surface may be altered from and based on a first geometry associated with the first posterior surface. Altering the second geometry associated with the second anterior surface and / or the second geometry associated with the second posterior surface may include ensuring that the second volume is within a predetermined threshold range of the first volume.

[0023] The ophthalmic lens may include a first surface. The ophthalmic lens may include a soft contact lens. The ophthalmic lens may include a toric contact lens. The ophthalmic lens may include one or more silicone hydrogels. The ophthalmic lens may include one or more conventional hydrogels.

[0024] The ophthalmic lens may include a second surface disposed opposite the first surface and defining a volume of lens material between the first surface and the second surface.

[0025] The ophthalmic lens may exhibit a first cylindrical power. A difference in a volume of lens material of the ophthalmic lens and a volume of lens material of the comparative lens may be minimized. The comparative lens may consist essentially of the same lens material as the ophthalmic lens and exhibit a second cylindrical power different from the first cylindrical power.

[0026] The difference in volume of lens material of the ophthalmic lens and the volume of lens material of the comparative lens can be minimized by configuring the geometry of one or more of the first surface and the second surface based at least on the first cylindrical power. The difference in volume of lens material of the ophthalmic lens and the volume of lens material of the comparative lens can be minimized by configuring the geometry of the first surface based on the cylindrical power associated with the optical zone of the second surface. The difference in volume of lens material of the ophthalmic lens and the volume of lens material of the comparative lens can be minimized by configuring one or more of a lens diameter or a base curve of the ophthalmic lens based at least on the first cylindrical power.

[0027] The difference in volume of lens material of the ophthalmic lens and the volume of lens material of the comparative lens can be minimized by configuring one or more surface features. The one or more surface features can include one or more indentations. The difference in volume of lens material of the ophthalmic lens and the volume of lens material of the comparative lens can be minimized by configuring one or more internal features. The one or more internal features can include one or more internal cavities.

[0028] The first cylindrical power may include a diffractive cylindrical power.The first cylindrical power may include a refractive cylindrical power.

[0029] A manufacturer may manufacture a first contact lens. The first contact lens may include a first cylindrical power. The first contact lens may include a first front surface. The first front surface may include a first front surface geometry. The first contact lens may include a first back surface. The first back surface may include a first back surface geometry. The first contact lens may include a first material. The first material may include a first volume.

[0030] The manufacturer may manufacture a second contact lens. The second contact lens may include a second cylindrical power. The second contact lens may include a second front surface. The second front surface may include a second front surface geometry. The second contact lens may include a second back surface. The second back surface may include a second back surface geometry. The second contact lens may include a second material. The second material may include a second volume. The first cylindrical power may be different from the second cylindrical power. The second front surface geometry and / or the second back surface geometry may be configured such that the second volume is within a predetermined threshold range of the first volume.

[0031] A first ophthalmic lens may be formed, the first ophthalmic lens having a first front surface and a first back surface, the first back surface being disposed opposite the first front surface and defining a first volume of lens material between the first front surface and the first back surface. A manufacturer may form a first ophthalmic lens, the first ophthalmic lens having a first front surface and a first back surface, the first back surface being disposed opposite the first front surface and defining a first volume of lens material between the first front surface and the first back surface. The first ophthalmic lens may exhibit a first cylindrical power. The first cylindrical power may be achieved by configuring the geometry of one or more of the first front surface and the first back surface. The first cylindrical power may be achieved by configuring the geometry of the first front surface based on the cylindrical power associated with the optical zone of the first back surface. The first cylindrical power may be achieved by configuring one or more of a lens diameter or a base curve of the ophthalmic lens. The ophthalmic lens may include one or more silicone hydrogels. The ophthalmic lens may include one or more conventional hydrogels.

[0032] A second ophthalmic lens may be formed having a second front surface and a second back surface disposed opposite the second front surface and defining a second volume of lens material between the second front surface and the second back surface. The manufacturer may form a second ophthalmic lens having a second front surface and a second back surface disposed opposite the second front surface and defining a second volume of lens material between the second front surface and the second back surface. The second ophthalmic lens may exhibit a second cylindrical power different from the first cylindrical power.

[0033] One or more of the first cylindrical power or the second cylindrical power may include a diffractive cylindrical power. One or more of the first cylindrical power or the second cylindrical power may include a refractive cylindrical power. One or more of the first ophthalmic lens or the second ophthalmic lens may include a soft contact lens. One or more of the first ophthalmic lens or the second ophthalmic lens may include a toric contact lens.

[0034] The first ophthalmic lens and / or the second ophthalmic lens may include one or more surface features. The one or more surface features may include one or more indentations. The first ophthalmic lens and / or the second ophthalmic lens may include one or more internal features. The one or more internal features may include one or more internal cavities.

[0035] The difference between the first volume of lens material and the second volume of lens material may be independent of the difference between the first cylindrical power and the second cylindrical power.

[0036] A manufacturer may manufacture a first contact lens. The first contact lens may include a first cylindrical power. The first contact lens may include a first front surface. The first front surface may include a first front surface geometry. The first contact lens may include a first back surface. The first back surface may include a first back surface geometry. The first contact lens may include a first material. The first material may include a first volume.

[0037] The manufacturer may manufacture a second contact lens. The second contact lens may include a second cylindrical power. The second contact lens may include a second front surface. The second front surface may include a second front surface geometry. The second contact lens may include a second back surface. The second back surface may include a second back surface geometry. The second contact lens may include a second material. The second material may include a second volume. The first cylindrical power may be different from the second cylindrical power. The second front surface geometry and / or the second back surface geometry may be configured such that the second volume is within a predetermined threshold range of the first volume.

[0038] A first ophthalmic lens may be formed having a first front surface and a first back surface disposed opposite the first front surface and defining a first volume of lens material between the first front surface and the first back surface. A manufacturer may form a first ophthalmic lens having a first front surface and a first back surface disposed opposite the first front surface and defining a first volume of lens material between the first front surface and the first back surface. The first ophthalmic lens may exhibit a first cylindrical power.

[0039] A second ophthalmic lens may be formed having a second front surface and a second back surface disposed opposite the second front surface and defining a second volume of lens material between the second front surface and the second back surface. The manufacturer may form a second ophthalmic lens having a second front surface and a second back surface disposed opposite the second front surface and defining a second volume of lens material between the second front surface and the second back surface. The second ophthalmic lens may exhibit a second cylindrical power different from the first cylindrical power.

[0040] One or more of the first cylindrical power or the second cylindrical power may include a diffractive cylindrical power. One or more of the first cylindrical power or the second cylindrical power may include a refractive cylindrical power. One or more of the first ophthalmic lens or the second ophthalmic lens may include a soft contact lens. One or more of the first ophthalmic lens or the second ophthalmic lens may include a toric contact lens. One or more of the first ophthalmic lens or the second ophthalmic lens may include one or more silicone hydrogels. One or more of the first ophthalmic lens or the second ophthalmic lens may include one or more traditional hydrogels.

[0041] A difference between a first volume of lens material and a second volume of lens material may be minimized. The difference between the first volume of lens material and the second volume of lens material may be minimized by configuring a geometry of one or more of the first anterior surface or the first posterior surface based at least on a first cylindrical power; and configuring a geometry of one or more of the second anterior surface or the second posterior surface based at least on a second cylindrical power. The difference between the first volume of lens material and the second volume of lens material may be minimized by configuring a geometry of the first anterior surface based on a cylindrical power associated with an optical zone of the first posterior surface; and configuring a geometry of the second anterior surface based on a cylindrical power associated with an optical zone of the second posterior surface.

[0042] The difference between the first volume of lens material and the second volume of lens material can be minimized by configuring one or more of the lens diameter or base curve of the first ophthalmic lens based at least on the first cylindrical power; and configuring one or more of the lens diameter or base curve of the second ophthalmic lens based at least on the second cylindrical power. The difference between the first volume of lens material and the second volume of lens material can be minimized by configuring one or more surface features associated with one or more of the first ophthalmic lens or the second ophthalmic lens. The one or more surface features may include one or more indentations. The difference between the first volume of lens material and the second volume of lens material can be minimized by configuring one or more internal features associated with one or more of the first ophthalmic lens or the second ophthalmic lens. The one or more internal features may include one or more internal cavities.

[0043] A manufacturer may manufacture a first contact lens. The first contact lens may include a first cylindrical power. The first contact lens may include a first front surface. The first front surface may include a first front surface geometry. The first contact lens may include a first back surface. The first back surface may include a first back surface geometry. The first contact lens may include a first material. The first material may include a first volume.

[0044] The manufacturer may manufacture a second contact lens. The second contact lens may include a second cylindrical power. The second contact lens may include a second front surface. The second front surface may include a second front surface geometry. The second contact lens may include a second back surface. The second back surface may include a second back surface geometry. The second contact lens may include a second material. The second material may include a second volume. The first cylindrical power may be different from the second cylindrical power. The second front surface geometry and / or the second back surface geometry may be configured such that the second volume is within a predetermined threshold range of the first volume.

[0045] Disclosed herein are systems and methods for designing soft contact lenses, such as toric lenses, in which the lens volume material remains constant independent of the amount of prescribed cylinder built into the lens. Disclosed herein are systems and methods for providing novel soft contact lenses having reduced volume variation compared to standard soft contact lenses.

[0046] For example, a soft toric contact lens design is described as having reduced volume variation compared to a standard soft toric contact lens design. The reduction in volume variation is achieved by adjusting the geometry of the anterior surface across the cylinder range of the present invention, adjusting the geometry of the posterior surface according to a specified amount of cylinder, or a combination of both.

[0047] A contact lens can be defined by a front surface or surface power, a back surface or base curve, and an edge. The front and back surfaces of the lens are described by at least three zones, namely, an inner zone where the vision correction can be obtained, an outer periphery of the lens that provides the mechanical properties of the lens, and an intermediate zone between the inner and outer zones that serves to blend the two aforementioned zones in a smooth manner so that no discontinuities occur.

[0048] The "optical zone" is defined as the generally central portion of the lens which includes vision correction for the wearer's ametropia and / or presbyopia. "Ametropia" is defined as the optical power typically required to provide good visual acuity at a distance. It is recognized that this will include myopia or hyperopia. Presbyopia is corrected by adding algebraic positive power to a portion of the optical zone to correct the wearer's near visual acuity requirements. It is recognized that these optical powers may be produced by refractive means, or diffractive means, or both. Power correction may also include astigmatism correction in conjunction with the previously mentioned vision correction.

[0049] The peripheral zone provides stability of the lens on the eye, including centering and orientation. This area of ​​the lens also provides mechanical properties, such as handling performance, comfort and fit related to ease of insertion and ease of removal. The tightness of the lens on the eye drives a loose fit that can result in too much movement or a tight fit that can result in insufficient movement. When the optical zone includes non-rotationally symmetric features (such as astigmatism correction and / or higher-order aberration correction), orientation stability is a basic requirement. The intermediate zone ensures that the optical zone and the peripheral zone are blended using tangent curves. It is important to note that both the optical zone and the peripheral zone can be designed independently, but sometimes their designs are closely related when specific needs are necessary. For example, the design of a toric lens with an astigmatic optical zone may require a peripheral zone for holding the lens on the eye in a predetermined orientation.

[0050] Generally speaking, astigmatism correction is built into the posterior surface side of a soft contact lens. The basic geometry of the posterior optical zone consists of a toric surface, where the flattest radius combined with the radius of the anterior surface provides spherical power correction (spherical meridian), and the steepest radius of the posterior optical zone, oriented at 90 degrees to the flattest radius, provides astigmatism correction (cylindrical meridian). The amount of astigmatism correction depends on the difference in curvature between the flattest meridian and the steepest meridian. Therefore, for the same geometry of the anterior surface, a higher level of astigmatism correction will require a steeper radius of curvature along the cylindrical meridian. For the same spherical power, an increase in curvature will result in an increase in volume. The cylindrical axis, obtained by setting the axis of the toric surface to the desired orientation according to the target prescription, does not affect the lens volume. Figure 1 An example of the lens volume of a soft toric contact lens using dual stability zones as a means of maintaining the angular orientation of the lens on the eye is shown. The lens has a 14.30 mm diameter and an equivalent base curve of 8.50 mm. The maximum peripheral thickness in the stability zone area is about 0.375 mm. For sphere power, the range of vision correction provided is from -9.00D to +6.00D in units of 0.25D, and for cylinder, the range of vision correction provided is from -0.75D to -2.75D in increments of 0.50D. FIG. 2A to FIG. 2C is a contour plot of a soft toric contact lens (-3.00D / -0.75D at 180 degrees) using dual stability zones as a means of maintaining angular orientation on the eye. In the example provided, even if the lens volume variation across the astigmatism correction provided for a given SKU does not exceed 4.5%, the total volume variation across the full SKU range is about 44%.

[0051] In contrast, for the same SKU range, Figure 3The volume of single vision soft contact lenses at two different base curves of 8.50 mm and 9.00 mm is presented for spherical power. The maximum peripheral thickness is about 0.215 mm. The total volume variation across the SKU range is about 45% and about 46% for the 8.50 mm base curve and the 9.00 mm base curve, respectively.

[0052] In the examples provided, the volume changes between toric lenses and single vision lenses are of approximately the same magnitude. Lens volume is the result of a combination of factors such as choice of material, base curve, diameter, center thickness, peripheral thickness geometry, etc. Therefore, the volume itself, as well as the variation in volume across a target SKU range, may be different than what is presented in the examples of the present invention. Those volume changes may be detrimental to the product performance intent and / or the manufacturing process of the product, and more specifically for toric lenses where the addition of astigmatism correction introduces an additional level of volume change across the entire SKU range. Therefore, reducing the volume variation will provide multiple benefits, and more specifically provide multiple benefits for some lenses where lens performance across SKUs is highly correlated to lens volume.

[0053] For example, if lens manufacturing is based on molding, spin casting or other types of processes that are sensitive to lens volume and / or volume changes, there is a benefit of reducing lens volume changes.Another benefit would be for lenses that include active or inactive ingredients added to the monomer mix or encapsulation solution.

[0054] Designs that present less volume variation may also make manufacturing such lenses less complex if the amount of active / inactive ingredients dispensed is related to the lens volume. Other benefits for such lenses include soft contact lenses where physical appearance is a key criterion for the lens. Tinted lenses and photochromic lenses are examples of such lenses. Additionally, lenses where material properties such as absorbance are critical to performance will benefit from the solutions of the present invention.

[0055] In a first exemplary embodiment, the reduction in volume change is achieved by adjusting the front surface geometry according to the amount of cylinder specified on the rear surface optical zone. Since toric lenses require angular stability, changes on the front surface of the lens must be made without affecting such aspects of the lens. A toric lens with a higher astigmatism correction also requires better angular stability and angular repeatability than a toric lens with a lower astigmatism correction. For the same angular misalignment, a subject with a large amount of astigmatism is more sensitive to lens angular misalignment than a subject with less astigmatism. Therefore, it is preferred to make design changes on the front surface so that if angular stability and angular repeatability are improved, the specified cylinder is larger.

[0056] Angular stability relates to how much angular variation a lens has while being worn by a subject once the lens reaches its final angular resting position. The less angular variation, the better the angular stability of the lens.

[0057] Angular repeatability relates to how much angular variation a lens has for its angular resting position. The more consistent the angular resting position is between subjects or within the same subject, the better the angular repeatability of the lens.

[0058] In a first example, the toric lens is a dual stable zone type design. The volume change associated with the prescribed cylinder is eliminated by changing the peripheral thickness along the 90 degree meridian to offset the volume change caused by the change in geometry of the back surface adjusted according to the prescribed amount of cylindrical power. In an example of the present invention, the thickness distribution along the 0 degree meridian in the peripheral zone remains unchanged across SKUs. Therefore, the maximum thickness along this meridian remains constant across SKUs. The thickness distribution along the 90 degree meridian in the peripheral zone is adjusted according to the prescribed amount of cylindrical power so that the induced volume change from the back surface is compensated by changing the distribution of the front surface along the 90 degree meridian. Adjusting the geometry of this meridian drives the total angular thickness change along these two meridians.

[0059] If we define the thickness difference as the difference in thickness between the maximum thickness in the peripheral region along the 0 degree meridian and the thickness at the same radial position along the 90 degree meridian, then in the examples of the present invention, the thickness difference will increase with increasing prescribed cylindrical power. It is known that for a dual stable zone type design, a large thickness difference provides better rotational performance and stability than a small thickness difference. Thus, improved angular stability and angular repeatability for a larger prescribed cylinder is achieved. Figure 4 The thickness profile of such lenses is depicted, where the thickness decreases along the vertical meridian while the specified cylinder increases. The cylinder axis is along the 90 degree meridian.

[0060] Figure 5 The resulting lens volume achieved using the method of the present invention is depicted. The volume change is independent of the amount of cylinder specified. The volume change is driven solely by the change in spherical power correction. The volume change percentage is about 11%. Further reductions in volume change can be obtained by adjusting other parameters that drive the geometry of the front surface, such as the center thickness, the anterior optical zone diameter, or the thickness at the edge of the anterior optical zone.

[0061] A similar result can be obtained by varying the maximum thickness while keeping the thickness distribution along the vertical meridian constant. This solution also provides a greater thickness difference for larger prescribed cylinders. Another option is to vary both the maximum thickness along the horizontal meridian and the thickness distribution along the vertical meridian so that the thickness distribution increases as the prescribed cylinder increases.

[0062] The same principles can be applied to toric soft contact lenses, for which angular stability and angular repeatability are achieved using different approaches.

[0063] Other criteria may also be considered during the lens design process, such as lens inversion, lens fold, lens wrap, which are typically evaluated through FEA modeling. Such criteria related to lens mechanical properties may also be included during the process of optimizing the geometry of the front surface according to the desired lens performance.

[0064] In a second exemplary embodiment, the reduction in volume change is achieved by adjusting the rear surface geometry according to the amount of cylinder specified on the rear surface. The front surface geometry remains unchanged.

[0065] The increase in volume that would result from changes in geometry along the cylindrical meridian within the posterior optic zone is balanced by adjusting the posterior optic zone diameter and / or adjusting the blended zone and / or the posterior peripheral zone. The blended zone and the posterior peripheral zone can be adjusted by changing the total curvature of the zone, the width of the zone, the sagittal depth of the zone, or a combination of all three. Preferably, the total sagittal depth of the posterior surface should not be changed.

[0066] For example, one method of the present invention to reduce the volume change due to the change in geometry of the posterior optical surface is to reduce the diameter of the posterior optical zone with the maximum specified cylindrical power so that the sagittal depth along the cylindrical meridian matches the sagittal depth along the spherical meridian. The remaining volume change can be eliminated by adjusting the blending zone and / or the posterior peripheral zone.

[0067] Such geometric variations in the posterior surface across the cylindrical range are too small to have an impact on lens wrapping and lens fit because these geometric variations are much smaller than the geometric variations we see in eye geometry in the general population.

[0068] Figure 6 The thickness profile of such a lens is depicted, where the posterior surface geometry is adjusted according to the amount of cylindrical power prescribed on the posterior optical zone, with the cylindrical axis set along the 90 degree meridian. The anterior surface remains unchanged and matches the anterior surface geometry of the previous example. The resulting lens volume is the same as the cylindrical prescribed at -0.75D. Therefore, the lens volume is Figure 5 The lenses presented are of the same volume.

[0069] In the example of the present invention, the outer geometry of the back surface is adjusted for each level of prescribed cylinder. Because this region is rotationally symmetric and the front surface does not change, the resulting radial thickness varies for each individual cylinder power level, as Figure 6 As shown, however, the resulting thickness difference remains constant, providing angular stability and angular repeatability across the entire SKU range.

[0070] Figure 7 is a box plot summarizing the volume change of different types of contact lenses across the same SKU range (-9.00D to +6.00D). The volume data labeled SV1 and SV2 refer to the previously mentioned single vision lenses with respective base curve radii of 8.50mm (SV1) and 9.00mm (SV2). The lenses labeled SV3 (8.50mm BC) and SV4 (9.00mm BC) are single vision lenses with reduced volume change of the previously mentioned examples. T1 corresponds to the use of Figure 1 and T2 corresponds to a soft toric contact lens designed based on the first method for reducing volume change of the present invention.

[0071] This principle can be applied to toric soft contact lenses for which angular stability and angular repeatability are achieved using different approaches.

[0072] Other criteria may also be considered during the lens design process, such as lens inversion, lens fold, lens wrap, which are typically evaluated through FEA modeling. Such criteria related to lens mechanical properties may also be included during the process of optimizing the geometry of the posterior surface according to the desired lens performance.

[0073] Figure 8 The volume of single vision soft contact lenses with two different base curves of 8.50 mm and 9.00 mm is presented. Figure 3 Single vision lenses share the same basic geometric characteristics (base curve geometry, optical zone diameter, lens diameter). The center thickness and peripheral thickness are adjusted to reduce volume variation. For the 8.50mm base curve and 9.00mm base curve, the volume variation over the full SKU range (-12.0D to +8.00D) is approximately 26% and approximately 24%, respectively. This corresponds to Figure 3 Compared with the original volume data provided in , this is a reduction of 43% and 48% respectively.

[0074] Other driving parameters besides central thickness and peripheral thickness may be adjusted to reduce volume variation, such as optical zone diameter. The choice of parameters will depend on the target performance and use of the contact lens.

[0075] While the first embodiment example provides the flexibility to adjust angular stability and angular repeatability across the range of cylinders, this example increases the number of front surfaces to be designed and results in greater manufacturing complexity. The number of tools / parts associated with the front surface side to be managed is greater. The advantage of the second approach is that this approach does not require a different leading edge for each cylinder power level and results in the same level of complexity as a standard toric lens. However, this solution does not provide the ability to adjust the desired performance of angular stability and angular repeatability by cylinder level.

[0076] In a third exemplary embodiment, a compromise can be made by combining the two solutions of the present invention. This embodiment reduces the manufacturing complexity of the first embodiment by limiting the number of front surfaces to be designed and adjusting the geometry of the rear surface to remove the volume changes caused by the geometric differences between the front surfaces. For example, a set of two front surfaces can be designed to accommodate the desired lens performance within a given specified cylindrical range. A minimum of two specific groups of leading edges can be designed across the cylindrical range, as shown in Tables 1A and 1B below. If a specific set of leading and trailing edges is ultimately designed for each single level of specified cylindrical power (Table 1C below), the solution thus corresponds to the first exemplary embodiment of the present invention.

[0077] Table 1A

[0078]

[0079]

[0080] Table 1B

[0081]

[0082] Table 1C

[0083]

[0084] While it may be desirable to have the same base curve / diameter combination across a range of SKUs, variations in one or both of those parameters may be applied to remove volume variations caused by the specified cylinder. For example, the lens diameter may decrease as the specified cylinder increases, or if the nominal diameter is set in the middle of the cylinder range, the diameter may increase for low cylinder powers and decrease for large cylinder powers. A similar strategy may be used with the base curve. For example, the base curve may flatten as the specified cylinder power increases, or if the nominal base curve is set in the middle of the cylinder range, the base curve may steepen for low cylinder powers and flatten for large cylinder powers.

[0085] In another exemplary embodiment, volume changes may be counteracted by adding surface features (e.g., as described in U.S. Pat. No. 9,389,434, hereby incorporated by reference in its entirety). The size and frequency of those features may be adjusted depending on the amount of volume to be managed. The type of feature is not limited to that presented in the referenced patent. It may be any type of surface feature that allows volume control by material removal. It may also be an internal feature, such that, for example, an internal cavity within the lens body also allows volume control by material removal.

[0086] In another exemplary embodiment, a diffractive optical device can be used to offset the volume change to provide a desired amount of prescribed cylinder. There are benefits to using a diffractive approach because the diffractive optical zone can form a power at the surface of the lens that is independent of the surface shape. The volume change caused by the diffraction pattern across the range of the cylinder will be significantly smaller than the volume change obtained when using refractive power to achieve a prescribed cylinder.

[0087] While what is shown and described is believed to be the most practical and preferred embodiment, it is apparent that changes may be made to the specific designs and methods described and illustrated by one skilled in the art, and that these changes may be used without departing from the spirit and scope of the invention. The invention is not limited to the specific constructions described and illustrated, but should be constructed to conform to all modifications that may fall within the scope of the appended claims.

Claims

1. An ophthalmic lens comprising: a first surface; and a second surface, the second surface being arranged opposite to the first surface and defining a volume of lens material between the first surface and the second surface, wherein the ophthalmic lens exhibits a first cylindrical power, and wherein a difference between the volume of the lens material of the ophthalmic lens and the volume of the lens material of the comparison lens is minimized, wherein the comparison lens comprises a comparison first surface and a comparison second surface opposite to the comparison first surface, a volume of comparison lens material being defined between the comparison first surface and the comparison second surface, the comparison lens material being composed of the same lens material as the ophthalmic lens, wherein the comparison lens exhibits a second cylindrical power different from the first cylindrical power, and wherein a geometry of one or more of the first surface and the second surface is configured based at least on the difference between the second cylindrical power and the first cylindrical power to minimize a difference between the volume of the lens material of the ophthalmic lens and the volume of the lens material of the comparison lens due to the difference between the second cylindrical power and the first cylindrical power.

2. The ophthalmic lens according to claim 1, wherein: The geometries of the first surface and the comparison first surface are the same and wherein the difference between the volume of the lens material of the ophthalmic lens and the volume of the lens material of the comparison lens is minimized by configuring the geometry of the second surface based at least on the first cylindrical power.

3. The ophthalmic lens according to claim 1, wherein: The difference in volume of the lens material of the ophthalmic lens and the volume of the lens material of the comparative lens is minimized by configuring the geometry of the first surface based on a cylindrical power associated with an optical zone of the second surface.

4. The ophthalmic lens according to claim 1, wherein: The difference in volume of the lens material of the ophthalmic lens and the volume of the lens material of the comparison lens is minimized by configuring one or more of a lens diameter or a base curve of the ophthalmic lens based at least on the first cylindrical power.

5. The ophthalmic lens according to claim 1, wherein: The difference in volume of the lens material of the ophthalmic lens and the volume of the lens material of the comparative lens is minimized by configuring one or more surface features.

6. The ophthalmic lens according to claim 1, wherein: The difference in volume of the lens material of the ophthalmic lens and the volume of the lens material of the comparative lens is minimized by configuring one or more internal features.

7. The ophthalmic lens according to claim 1, wherein: The first cylindrical power comprises a diffractive cylindrical power.

8. The ophthalmic lens according to claim 1, wherein: The first cylindrical power includes refractive cylindrical power.

9. The ophthalmic lens according to claim 1, wherein: The ophthalmic lenses include soft contact lenses.

10. The ophthalmic lens according to claim 1, wherein: The ophthalmic lens comprises a toric contact lens.

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