RU2806085C2 - Contact lens with rotary angle stabilization, increased comfort and improved stabilization using optimized stiffness profiles - Google Patents

Abstract

FIELD: ophthalmology.

SUBSTANCE: non-truncated contact lens with rotation angle stabilization contains an optical zone configured to correct vision, and a peripheral zone surrounding the optical zone and configured to ensure rotation angle stability by optimizing the non-roundness component, the thickness difference component, and the rigidity profile component. The out-of-roundness component includes a first effective dimension formed by the diameter of an inscribed circle within a peripheral zone of the contact lens having a first center, and a second effective dimension defined by the diameter of an inscribed circle around a peripheral zone of the contact lens having a second center. The thickness component of the differences is determined by the difference between the maximum thickness and the minimum thickness. The stiffness profile component is defined as the effective area under the thickness profile curve obtained by multiplying the square of the lens thickness taken along the lens meridian at various radial positions by the modulus of elasticity of the lens material.

EFFECT: technical result is to improve the stability of the rotation angle and remove or prevent the appearance of bubbles trapped behind the lenses.

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Description

PREREQUISITES FOR CREATION OF THE INVENTION

1. Scope of the invention

The present invention relates to ophthalmic lenses and, in particular, to contact lenses with rotation stabilization. More specifically, the present invention relates to designs and methods that optimize lens geometry and utilize rotational recovery and comfort modeling to provide acceptable lens rotation angle stabilization while providing improved ocular comfort.

2. Description of the prior art

Contact lenses are medical devices and may be used for vision correction and/or for cosmetic or other therapeutic reasons. Contact lenses have been marketed to improve vision since the 1950s. Early contact lenses were made or manufactured from hard materials and were relatively expensive and fragile. Although such contact lenses are still used today, they are not suitable for all patients due to the low level of initial comfort. Further developments in this area led to the creation of soft contact lenses based on hydrogels, which are extremely popular and widely used today. The introduction of soft contact lenses has significantly improved user comfort. One type of contact lens is a spherical contact lens, which provides substantially uniform optical power, and because such lenses are essentially spherical, they feature rotation symmetry such that the rotation angle of placement or position on the surface of the eye does not cause serious problems . For those patients who require astigmatic correction, cylindrical power correction can be used to correct vision in addition to spherical power correction. These lenses, sometimes called toric lenses, require the optical design to stabilize the rotation angle in the correct orientation when worn on the surface of the eye. In a patient with astigmatism, relative rotational orientation of the lens is important for vision correction.

Astigmatism is caused by non-axisymmetric curvature of the cornea and/or lens. The normal cornea is essentially axisymmetric, whereas in a patient with astigmatism the situation is different. In other words, the eye's cornea is more curved or bulging in one direction than in another, causing the image to be stretched across the line of focus rather than focusing on a single point. To overcome this problem, you can use toric rather than spherical/monofocal lenses. A toric lens is an optical element that has two different optical powers in two mutually perpendicular orientations. Essentially, a toric lens has two powers, both of which are combined in one lens, one of them (spherical power) on a specific axis for the correction of myopia or hypermetropia, and the other (cylindrical power) for the correction of astigmatism. These magnifications are created by curved surfaces oriented at different angles that are preferentially supported relative to the eye. Therefore, proper rotational orientation of the toric lens is necessary to properly correct astigmatism. However, toric contact lenses tend to rotate on the surface of the eye when applied, resulting in temporary suboptimal vision correction. Accordingly, currently used toric contact lenses also include a mechanism to maintain the relative stability of the contact lens and its correct orientation on the surface of the eye when the wearer blinks or looks around to maintain proper vision correction. A similar mechanism also serves to return to a stable and correct orientation on the surface of the eye after insertion or when the lens deviates from the correct position and orientation. Various stabilization techniques, such as ballast or preferential thick and thin zones, are used to ensure proper lens orientation in a given area. There are different ways to achieve stabilization, and ultimately all of these methods will be affected to varying degrees by the interaction of the back surface of the contact lens with the front surface of the eye, as well as with the eyelids, in particular in the peripheral areas, which can adversely affect vision and subjective user comfort.

The challenge with stabilization zones being developed or currently in use is the trade-off between contact lens stability and comfort, as well as the physical limitations associated with increasing lens thickness in the stabilization zone areas. Configuration changes required to improve rotation speed, such as increasing the slope of the stabilization zone surface, also increase the thickness of the contact lens and may have a negative impact on the comfort of the product. In addition, the configuration of the contact lens must comply with two principles; namely, to rotate to the appropriate orientation upon insertion and maintain that orientation during the wearing period. Traditional designs require performance compromises under several of these assumptions. Although the majority of today's standard lenses are round in shape, the use of non-round geometric shapes in some cases can provide additional flexibility to provide the optimal balance between stabilization and comfort for further improvement.

US Patent No. 6,406,145 provides information on contact lenses with minimal thickness changes with stabilization of rotation angle. US Patent No. 6,491,392 design of the stabilizing elements uses spline or polynomial functions to improve comfort, while US Patent Nos. 6,939,005 and 7,159,979 focus on the slope of changes in thickness differences to reduce lens stabilization time. US Patent Nos. 7,201,480 and 7,682,019 discuss the use of thin zones for stabilization purposes.

Newer efforts to provide a solution for patients with astigmatism, see, for example, US Pat. No. 8,827,448, propose the use of anti-astigmatic specialty refractive correction lenses with a first cylindrical power on the anterior surface and a second cylindrical power on the back surface of the contact lens. Although this design is expected to achieve increased visual acuity, these elements are limited by the optical zone of the lens and how it interacts with the asymmetric cornea. Design changes to other areas, particularly the peripheral area of the lens, may still contribute and may not adversely affect the visual acuity elements of the optical zone, and thus may coexist with them and further improve lens performance. .

Previous attempts to use non-circular lenses for stabilization purposes are described in US Pat. No. 5,760,870, primarily to avoid thickening the lens for stabilization purposes. The authors of Patent No. 5,760,870 noted that thickening the lens creates discomfort for the patient, leads to undesirable changes in optical power and reduces oxygen permeability in the thickened areas, and instead preferred the use of a non-circular lens, in which case stabilization would be provided due to the resulting difference in aspect ratio. relation to the lens, not differences in thickness. Recently, US Patent No. 8,668,331 describes the use of a non-circular lens to maximize lens-lid interaction for centering, rotation and stabilization and may be of interest. US Patent Application Published No. US 20140063444, the copyright of which belongs to the owner of the present invention, describes the use of round and non-round shapes along with stabilization zones; however, it does not describe the simultaneous use of a combination of shape and thickness optimization. Interaction of the lens with the corneal surface, particularly at the limbus, can result in trapped bubbles behind the lens, this situation may be more common when using larger diameter lenses as the diameter of the lenses tends to extend beyond the limbus location. US Patent No. 9,778,487, which is owned by the owner of the present invention, is particularly relevant and describes a methodology that uses and combines non-circularity and thickness differences to optimize lens design.

Thus, most prior art authors have attempted to solve the stabilization problem at hand through selective lens thickening, lens thinning, prismatic ballast, and other techniques that can essentially be characterized as variable thickness designs. A limited number of authors have sought solutions using non-circular lenses, which can essentially be characterized as round/non-circular designs, with some attempting to mask astigmatism altogether. Moreover, despite significant improvements in both lens design and materials, many contact lens wearers continue to experience discomfort concerns. The applicant believes that very few have approached the issue of lens design comprehensively using a range of modeling tools, and even fewer have been successful. The applicant believes that the use of such tools can provide insight into how the lens design interacts with the corneal surface on which it is located and how lens geometry can be optimized to achieve angular stabilization with increased comfort.

Accordingly, there is a need for contact lenses to further improve rotational stability, which is achieved by simultaneously optimizing out-of-roundness and thickness variations as a system to achieve higher visual performance while maintaining a high level of comfort and vision correction. The second purpose is to remove or prevent bubbles trapped behind larger diameter lenses. In particular, lenses with stabilizing elements and diameters that cause the lens to extend beyond the limbal region are more prone to trapping bubbles behind the lens.

US 2017059882 A1 discloses a contact lens and a lens design method using aspects of non-circularity and thickness differences to design the lens.

SUMMARY OF THE INVENTION

The contact lens in accordance with the present invention overcomes the disadvantages associated with the prior art, as briefly described above, by providing a non-circular lens configuration with an optimized design that prevents central flexion of the lens, minimizes its rise above the limbus (the area where the cornea meets the sclera). ) to prevent the formation of bubbles, ensures uniform distribution of contact stress, and is easy and correct to orientate, while providing satisfactory or improved comfort. In particular, by utilizing the entire lens shape and optimizing the reshaping of stabilization zones based on feedback from predicted eye patterns, results can be achieved that are not achievable using more traditional approaches.

Applicant has further improved the invention after it was discovered that there is a preferred relationship between the shape of the lens edge (non-roundness or diametric aspect ratio) and the extent of the thickness differences applied. See US Patent No. 9,778,487 by the same applicant, which is incorporated herein by reference. Although the approach described in the '487 patent resulted in a lens optimized for stabilized orientation, comfort and handling, thereby providing superior performance not achievable by either non-circular lens approach or thickness differences individually, the present authors The inventions add an additional stiffness profile aspect to realize additional improvements in the comfort of the lens on the ocular surface while providing equivalent rotational recovery of the lens and reducing the appearance and size of bubbles under the lens.

As described in US Pat. No. 9,778,487, both out-of-roundness and thickness differences can be used to optimize lens design. In the present invention, applicants have further improved this technique and the resulting lens design by incorporating an additional aspect, namely a stiffness profile, compared to the methodology used in US Patent No. US 9,778,487. In accordance with the present invention, this is achieved by intelligent placement of the material both diametrically and and circumferentially, which provides similar rotational recovery to typical prior art stabilized lens designs, but with the added benefit of significantly reduced thickness variations. We call this the stiffness profile. If out-of-roundness and thickness differences represent the first two dimensions of design freedom for which an optimal second-order design can be achieved by analyzing the choice of out-of-roundness in combination with given thickness differences, applicants have found that adding a third design dimension in accordance with the present invention, which represents is a stiffness profile, can provide additional design flexibility and design options to achieve an optimal design within each of the three dimensions of the design space, which further serves to improve the optimal design existing in a two-dimensional design space in accordance with US patent No. US 9778487 of the same applicant.

Stiffness depends on both the modulus of elasticity and the thickness of the material. Stiffness can be calculated as E times t cubed, where E is the modulus of elasticity and t is the normal thickness at a given point (flexural stiffness). Others have defined stiffness as E times t (tensile stiffness). In the present invention, applicants have chosen to use a stiffness profile defined as E times t squared, which, although not stiffness in the strictest sense, is indeed proportional to stiffness.

Accordingly, the present invention provides a non-truncated rotation-stabilized contact lens comprising:

an optical zone configured to correct vision;

a peripheral zone surrounding the optical zone and configured to provide rotation angle stability, such rotation angle stability being achieved by providing and optimizing an out-of-roundness component, a thickness difference component, and a stiffness profile component,

wherein the out-of-roundness component includes a first effective dimension formed by the diameter of an inscribed circle that lies within a peripheral zone of the contact lens having a first center, and a second effective dimension formed by the diameter of an inscribed circle around a peripheral zone of a contact lens having a second center, wherein the ratio of the first effective size to second effective size is in the range of from about 0.6 to about 0.95,

the thickness difference component has a maximum thickness and a minimum thickness and is determined by the difference between the maximum thickness and the minimum thickness, and the thickness differences range from about 0.1 mm to about 0.4 mm, and

the stiffness profile component is defined as the effective area under the thickness profile curve obtained by multiplying the square of the lens thickness taken along the lens meridian at various radial positions by the elastic modulus of the lens material,

wherein said effective area ranges from about 0.021 MPa x mm ³ to about 0.109 MPa x mm ³ .

In particular embodiments, the diameter of the inscribed circle ranges from about 13.5 mm to about 14.5 mm. The circumscribed circle diameter ranges from about 14.0 mm to about 20.0 mm.

The ratio of the first effective size to the second effective size ranges from about 0.8 to about 0.95. In this case, the shape of the peripheral zone is asymmetrical. The first center and the second center coincide or do not coincide. Non-coinciding centers are located on the same horizontal meridian or on the same vertical meridian.

The present invention may provide a method for optimizing the stabilization of a contact lens on the ocular surface while providing maximum comfort. This method contains several steps, the first of which is to define a matrix set of peripheral geometries having a non-circular component and thickness differences, where the non-circular component is from 95% to 60% of the full circle, and the thickness differences are in the range of 0.1 mm up to 0.4 mm, while the matrix set includes at least two values of out-of-roundness and at least two values of differences in thickness. This is followed by the step of calculating the stabilization time for each element in the matrix set for a given non-circular component and given thickness differences; and then an isoparametric image is created reflecting the stabilization time of each element in the matrix set. The isoparametric image is then evaluated and a preferred region is determined based on at least one of the three variables of maximizing comfort, minimizing stabilization time, or manufacturing complexity, and then finally selecting a peripheral geometry that has both a non-circular component and differences in thickness, which provide optimal stabilization time within the preferred area. If the desired peripheral geometry shape with its non-circular component (i.e. diametric aspect ratio) and thickness differences needs further optimization, the process can be repeated until the resulting combinations achieve the desired conditions.

Also disclosed is a contact lens having an inner optical zone for vision correction, as well as an outer zone configured to provide rotation angle stability, such rotation angle stability being achieved through a combination of out-of-roundness, or what is referred to as diametrical aspect ratio reduction, and a component of differences in thickness. Non-circularity, or a reduction in diametrical aspect ratio, can be described by a pair of effective dimensions that are proportionally related to each other and determined by inscribed and circumscribed circles, as well as the position of the centers of such circles to form a set of non-circular shapes. The diametric aspect ratio or degree of out-of-roundness is preferably in the range of 0.6 to 0.95. The thickness difference component may be determined by differences between the maximum and minimum thickness of the lens, and such difference is preferably between 0.1 mm and 0.4 mm. Peripheral zones can be symmetrical or asymmetrical. The centers of the circumscribed and inscribed circles, which define the effective dimensions of the lens shape, may or may not coincide and may be on the same or different vertical or horizontal meridians.

Also disclosed is a contact lens further comprising a third order design principle that utilizes a contact lens stiffness profile. In addition to non-roundness and thickness variations, the stiffness profile (or, alternatively, judicious placement of the lens material) is used to achieve an optimal balance between the propensity of the geometric shape to create rotational angle stability and the resulting comfort of the lens on the ocular surface. This allows both to achieve maximum efficiency and to further increase the comfort of the lens on the surface of the eye. In particular, and in accordance with the present invention, applicants have found that for a given out-of-roundness and thickness differences, thickness differences can be further reduced to approximately 50% with a preferred range of 30 to 50% by judicious material placement while still providing adequate rotational recovery . This reduction results in increased lens comfort on the ocular surface and reduced bubble formation. Applicants have found that reductions below 30% do not have a significant effect on reducing bubble formation, while values greater than 50% are not sufficient to achieve rotational recovery.

In addition, a method is disclosed that further increases the degree of maximum comfort while maintaining optimization of stabilization of the contact lens on the surface of the eye. This method contains several steps, the first of which is to define a matrix set of peripheral geometries having a non-circular component and thickness differences, where the non-circular component is from 95% to 60% of the full circle, and the thickness differences are in the range of 0.1 mm up to 0.4 mm, while the matrix set includes at least two values of out-of-roundness and at least two values of differences in thickness. The use of multiple analytical tools to determine the optimal stiffness profile, combined with out-of-roundness and optimal and further reduced thickness differences, results in optimized design in each of the three dimensions of the design space, allowing for further improvements in comfort. This is followed by the step of calculating the stabilization time for each element in the matrix set for a given non-circular component, given thickness differences and an optimized stiffness profile; and then an isoparametric image is created reflecting the stabilization time of each element in the matrix set. The isoparametric image is then evaluated and a preferred area is determined based on at least one of the three variables of maximizing comfort, minimizing stabilization time, or manufacturing complexity, and then finally selecting a peripheral geometry that has a non-circular component, thickness differences, and stiffness profile. , which provide optimal stabilization time within the preferred design space. If the desired shape of the peripheral geometry with its non-circular component (i.e. diametric aspect ratio), thickness differences and stiffness profile needs further optimization, the process can be repeated by changing the initial lens design parameters until the resulting combinations achieve the desired conditions.

Stabilization optimization can be determined by assessing how quickly the lens stabilizes at its desired angular position. On the other hand, lens comfort is more subjective, but can nevertheless be predicted using analytical methods and confirmed in clinical studies. Although both out-of-roundness and thickness differences individually can provide a reduction in stabilization time in different ways, the combination of these two factors in accordance with the present invention can not only improve the stabilization time more effectively than either of them alone, but also do so more comfortably. way. The use of a stiffness profile further increases the level of comfort that can be obtained without sacrificing stabilization time. Although reducing thickness differences can improve comfort, it also has a negative impact on stabilization effectiveness. Increasing out-of-roundness can improve stabilization effectiveness, but at the expense of reduced comfort, increased manufacturing complexity and increased costs, as well as increased lens handling problems. The optimal stiffness profile allows the lens thickness to be optimally distributed both radially and circumferentially to provide only the minimum level of thickness required to achieve stabilization, thus further enhancing comfort.

The present invention allows multiple such approaches to be used to obtain an optimized design that performs better than any other design that uses only one of these approaches. Another goal is the desired lens design that can be achieved using this approach. Yet another object is to improve existing designs using the methodology described in accordance with the present invention. The contact lenses of the present invention can be used with any type of contact lens optic without increasing cost and can be optimized to improve clinical comfort and/or physiology. In addition, combination products such as contact lenses in combination with therapeutic agents and cosmetic lenses having cosmetic structures can also take advantage of the present invention.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

The above and other features and advantages of the present invention will become apparent from the following more detailed description of the preferred embodiments of the invention shown in the accompanying drawings.

In FIG. 1A is a basic image of a lens and its regions when viewed through a non-circular lens itself in accordance with the present invention.

In FIG. 1B is a cross-sectional view of the non-circular lens shown in FIG. 1A, in accordance with the present invention.

In FIG. 2A-2E are schematic illustrations of various round (conventional) and non-round shaped lenses, as well as the principle of determining the degree of non-roundness or diametric aspect ratio in accordance with the present invention.

In FIG. Figure 3 provides an isoparametric plot of clinical comfort scores for various characteristics of both circle lens diameter and lens thickness variations, with higher clinical comfort scores corresponding to more comfortable conditions.

In FIG. 4A-4D show experimental isoparametric images of the limiting settling time for various diametric aspect ratios (out-of-roundness) and a set of thickness differences, and indicate how such information is used to achieve the desired lens performance characteristics for a given out-of-roundness or diametric aspect ratio and thickness differences. in accordance with the present invention.

In FIG. 5 is a basic flow diagram of the methodology used for the second order optimization process in accordance with the present invention.

In FIG. 6 is a basic flowchart of the methodology used for the optimized design in each of the three design space dimensions in accordance with the present invention.

In FIG. 7 shows an example of adding effective area/stiffness profile as an additional design dimension for an optimized design in each of three design space dimensions and the resulting design space defined by three design dimensions with different diametric aspect ratios (out-of-roundness), different thickness differences, and stiffness profiles.

In FIG. 8A-8C show some typical output from a rotation/centering model, showing what a representative design would look like.

In FIG. 9A-9F present and compare typical outputs of applicants' eyelid comfort model, showing the results of three different design configurations and the effect of each on the stress state of the eyelid itself, which in this case serves as a measure of comfort. More specifically, in FIG. 9B is a detail view of FIG. 9A, in FIG. 9D is a detail view of FIG. 9C, and in FIG. 9F is a detail view of FIG. 9E.

In FIG. 10 presents typical output from Applicants' virtual wrap model, showing the results of three different design configurations and the effect of each on the uniform or uneven distribution of contact stress in the lens as it interacts with the corneal/ocular surface.

In FIG. 11A-11C illustrate typical prior art toric lens designs, prior art nontoric lens designs, and an optimized design in accordance with the present invention, as well as how each interacts with a typical ocular surface topology.

In FIG. 12A depicts the stiffness profiles of a representative structure in accordance with the present invention compared to many reference design conditions in the art.

In FIG. 12B and 12C show how the effective area (a measure of the stiffness profile and thus comfort) is determined.

In FIG. 13A and 13B show the time required for rotational recovery of two representative lens designs (ie: time required to rotate the lens from a 45 degree position to stabilize) calculated using a virtual analytical rotation and alignment model.

In FIG. 14A and 14B show the angular distribution of lens position over time for two representative designs and their significant difference in terms of rotational recovery.

DETAILED DESCRIPTION OF PREFERRED IMPLEMENTATION OPTIONS

For purposes of the present invention, the contact lens 10 shown in FIG. 1A is formed with at least two dissimilar regions. They form an inner region 11, which provides vision correction, and an outer peripheral region 13 of the contact lens 10, which provides mechanical stability of the contact lens 10 on the surface of the eye. A third optional intermediate zone 12 located between the inner region 11 and the outer region 13 can be used to merge the above two regions in a smooth manner so that there is no sharp boundary between them. In some embodiments, the intermediate zone 12 may not be required.

The inner region 11, or optical zone, provides vision correction and is designed to perform specific functions, for example, monofocal vision correction, astigmatic vision correction, bifocal vision correction, multifocal vision correction, specialized correction, or may have any other design that provides vision correction . The outer periphery or peripheral zone 13 provides basic fit and stabilization of the contact lens on the surface of the eye, including its centering and orientation.

Stabilization of the rotation angle is of fundamental importance when the optical zone includes elements with rotational asymmetry, for example, elements for correcting astigmatism and/or other higher order aberrations. An optional intermediate zone or zone 12 provides a smooth transition from the optical zone to the peripheral zone. It should be noted that both the optical zone 11 and the peripheral zone 13 can be configured separately, although sometimes the designs of each are closely related to each other when there are interactions. For example, a toric lens design with an astigmatic optical zone may require a specific peripheral zone to hold the contact lens in a predetermined orientation on the ocular surface.

For purposes of the present invention, the contact lens is also formed with a front surface 14, a back surface or base curve 15, and an edge 16, as shown in FIG. 1B, which shows a cross section of the lens of FIG. 1A. The front and back surfaces of the contact lens are defined by at least two regions - an inner region 11 that corrects vision, and an outer region 13 or the periphery of the contact lens that provides mechanical stability to the contact lens on the surface of the eye. As noted above, an optional intermediate zone 12 located between the inner region 11 and the outer region 13 can be used to align and/or interface the two above regions in a continuous and/or smooth manner so that there is no sharp boundary between them, as described higher. In certain cases of non-circular designs, the intermediate zone 12 provides a smooth transition from the circular optical zone to the non-circular periphery, while avoiding the formation of sharp boundaries and smoothing changes in thickness along the radial dimension of the lens 10.

Lens thickness is an important variable that can be optimized and can be determined in any of the three regions, but preferably in the outer or peripheral region 13, by simply measuring the relative distance along a direction perpendicular to the main curve between the front surface 14 and the rear surface 15. Differences in thickness can be determined by the difference between the nominally thick areas of the lens and the nominally thin areas of the lens. The nominally thick area represents the maximum peripheral thickness of the lens. The nominally thin area of a lens is located along the minimum peripheral thickness meridian, but is defined as the thickness at a proportionately equal radial distance to the maximum lens thickness meridian. This is an important variable for both stabilization effectiveness and comfort purposes. In general, the greater the difference in thickness, the more pronounced the stabilizing effect will be; unfortunately, larger differences in thickness are usually also more noticeable to the user and can create more discomfort, especially for sensitive lens wearers. In accordance with the present invention, it is possible to calculate the effect of using a reduction or percentage of given thickness differences, and also calculate what effect such reduction or percentage has on the time required to stabilize a given lens design, as well as the effect on comfort. You can also directly set the desired thickness differences. The inventors' research and experience to date have shown that thickness differences in the range of 0.1 mm to 0.4 mm are preferable for improving comfort while achieving effective stabilization in accordance with the present invention.

Edge 16 represents the edge of contact lens 10 and is also a variable that can be taken into account in the optimization scheme. For the present invention, the shape of the edge 16 is preferably non-circular and may also be asymmetrical. For present purposes, roundness/out-of-roundness is defined as the ratio of the largest inscribed circle diameter that may lie within the lens's peripheral shape to the smallest inscribed circle diameter that lies around the lens's peripheral shape. Thus, in a conventional round contact lens, these two diameters will not only be equal to each other, but also the centers of both diameters of the inscribed and circumscribed circles will coincide. In accordance with the present invention, the result of such non-roundness may be an oval lens. This occurs when the center of the largest diameter of the incircle and the center of the smallest diameter of the circumcircle coincide, but the diameters in each circle are not equal to each other, as shown in Fig. 2B. Non-circularity, or what we call diametric aspect ratio, can also extend to asymmetrical lenses with asymmetry about either the horizontal meridian or the vertical meridian. This kind of asymmetrical lens can be obtained if the centers of the diameters of the inscribed and circumscribed circles are located along the vertical or horizontal meridians, respectively, but do not coincide. Finally, another example of non-circularity in accordance with the present invention would be an asymmetrical profile in which the non-coinciding centers are not located along the horizontal or vertical.

If we analyze the reduction in thickness differences separately for a circular lens (a lens with an aspect ratio of 100% is considered round), the effect of this factor is that as the percentage of initial thickness differences decreases, the stabilization time increases. If an increase in out-of-roundness, or alternatively a decrease in diametrical aspect ratio, is assessed for given initial thickness differences, one may observe a slight decrease in stabilization time, then no change, and then an increase in stabilization time. Thus, for thickness differences of 95%, starting with a round lens (diametric aspect ratio is 100%), as the diametric aspect ratio decreases from 100%, the stabilization time decreases, reaching its minimum at a diametric aspect ratio of approximately 85%, further reductions in diametric aspect ratio Aspect ratios below the 85% level lead to the opposite effect, and the stabilization times increase as the diametrical aspect ratios subsequently decrease. However, such a trend and the steepness of the changes vary depending on the varying differences in thickness. By studying the combination of increasing out-of-roundness or decreasing diametrical aspect ratio in combination with simultaneously decreasing thickness differences, as provided by the present invention, so that local areas with minimal stabilization time can be identified, a superior product can be offered compared to those that can be obtained when using non-roundness or thickness differences separately.

In FIG. 2A-2E show approximately five typical situations. The first example (see FIG. 2A) shows a standard circular contact lens 20 in which the inscribed and circumscribed circles (not shown) have equal diameters, which are also equal to the diameter of the lens. In addition, the centers of all three circles (inscribed, circumscribed and the lens itself) coincide and are located at the intersection of the superior-inferior axis 26 and the nasal-temporal axis 28. Thus, both circles and the location of the centers do not differ from the parameters of the peripheral field of the lens 20. B In the first non-circular example (see FIG. 2B), which is an oval in shape, the incircle 22 and the circumcircle 24 have unequal diameters, but their centers coincide. The consequence of this is a non-circular geometry of the lens 20 that is symmetrical about both the supero-inferior axis (vertical meridian) 26 and the nasal-temporal axis (horizontal meridian) 28. In FIG. 2C, the center of the inscribed circle 22 is shifted along the nasal-temporal axis (horizontal meridian) 28 by a distance 27 relative to the center of the inscribed circle 24. As a result, temporo-nasal asymmetry occurs while maintaining superior-inferior symmetry. Similarly in FIG. The 2D center of the inscribed circle 22 is shifted along the superior-inferior axis (vertical meridian) 26 by a distance 29 relative to the center of the inscribed circle 24. As a result, superior-inferior asymmetry occurs while maintaining nasal-temporal symmetry. The last representative example in this series is shown in Fig. 2E, in which the incircle 22 is offset along both the superoinferior axis 26 and the nasal-temporal axis 28 relative to the incircle 24. As a result, an asymmetrical shape of the lens 20 is formed. As shown in FIG. 2C-2E, the degree of horizontal displacement 27 and vertical displacement 29 of the central position, as well as the diameters of the incircle 22 and circumcircle 24 are not only related to each other, but may vary and may be different to create a variety of non-circular lens shapes in addition to the presented shapes in typical five examples.

In FIG. Figure 3 provides isoparametric comfort characteristics when considering the relationship between differences in thickness and a set of vertical dimensions/diameters of a circular lens. In this image, comfort scores of 48 represent a lower level of comfort than comfort scores above 48. As can be seen, the overall trend of decreasing thickness differences still increases comfort levels as thickness differences smooth out, but comfort improvement rates are also dependent on diameter/dimensions . It can also be seen that for larger thickness differences (>75%), as the circular diameter increases from 14.0 to 14.5, there is an increase in comfort level for given thickness differences that are greater than 75%. This situation is in contrast to smaller thickness differences (<55%), where for a given thickness difference, as the circular diameter increases from 14.0 to 14.5, there is a decrease in comfort level for a given thickness difference that does not exceed 55%. . In this example, the 14mm size/diameter combined with the smallest percentage of thickness variation provides the greatest comfort level with a score of 66 or higher. Although it is possible to select vertical diameters that are both larger and smaller than 14.00 mm, the examples below focus on the 14.00 mm vertical diameter case.

Although the ratio and synergistic effect achieved by simultaneously exploiting differences in thickness and out-of-roundness are important, the influence of diameter must also be taken into account. The examples below will describe lenses with vertical diameters of 14.00 mm with corresponding horizontal diameters based on different percentages of diametric aspect ratio. In FIG. 4A-4D show the ratio of differences in thickness and out-of-roundness that produces the preferred region 49 in accordance with the present invention. Such an area provides maximum comfort and also meets other requirements, such as stabilization time or ease of manufacture. Isoparametric images in Fig. 4A-4D are built around a lens having a constant vertical dimension/diameter of 14.0 mm and the isoparametric lines or regions indicating the stabilization time limit are scaled/normalized from greater than 90 seconds to less than -50 seconds. The cutoff time is defined as the time required for the lens to stabilize within 10 degrees of its final resting state as predicted by the model's theoretical predictions. Normalization of the predicted time values is carried out relative to the time spent on stabilizing the original structure.

In FIG. 4A shows a representative isoparametric image 40 of the time limit for stabilization of a lens with a vertical diameter of 14.0 mm. The corresponding horizontal diameters are obtained by dividing the vertical diameter of 14.0 mm by the diametric aspect ratio. Thus, a diametric aspect ratio group of 94% would correspond to a horizontal diameter of 14.89 mm, and a diametric aspect ratio group of 88% would correspond to a horizontal diameter of 15.91 mm, and so on for the remaining diametric aspect ratios. For each group of diametric aspect ratios with a constant horizontal diameter, the corresponding thickness differences were calculated. This image was constructed of a set of data points (shown as black dots in isoparametric image 40) for each combination of diametric aspect ratio and thickness differences. Each data point represents the average of the cutoff time values for stabilization across three eyes for a particular combination of diametric aspect ratio and thickness differences. Time limits are normalized relative to the time limit obtained for a given initial structure (values less than 0 indicate faster settling times than the initial structure). This image shows the effect of changes in both thickness differences (horizontal axis) 42 and the effect of changes in diametric aspect ratio or changes in out-of-roundness of the lens periphery (vertical axis) 44. As shown, such an isoparametric image 40 is not monotonic, and therefore due to this Combinations of out-of-roundness and thickness differences arise that are more desirable than others when both variables are considered simultaneously.

As shown in FIG. 4B, depending on which thickness difference reduction is used in a given case, while simultaneously increasing the degree of out-of-roundness or reducing the diametrical aspect ratio, the response of the desired stabilization time will differ depending on the selected combination. As an example, three portions of a given path (isoparametric line 46) in isoparametric image 40 are identified, a path portion 41 corresponding to approximately 97% of the thickness differences, a path portion 43 corresponding to approximately 75% of the thickness differences, and a path portion 45 corresponding to approximately 59% of the differences are in thickness. As can be seen, the required degree of non-circularity to achieve the same level of stabilization time, determined by the isoparametric line 46, is different for each trajectory segment. This isoparametric line (labeled 46 in Figure 4B) corresponds to the maximum desired stabilization time, which is based on clinical studies and is the dividing line between time limits that are greater and less than the stabilization time of the original design. Although values below such an isoparametric line will be more acceptable for settling time values, there are other considerations or trade-offs that must be taken into account, such as comfort and ease of manufacture.

As noted above, although increasing thickness differences inherently reduces stabilization time, comfort may also be compromised. Clinical studies conducted by the applicant indicate that acceptable levels of comfort are related to differences in thickness. Consistent with the results of such internal clinical studies, it can be noted that a reduction in thickness differences below 70% of the original thickness differences appears to provide a more acceptable level of comfort compared to a value above 70%, therefore, applicants have determined that, as shown in Fig. 4B, in the present example, the preferred values are to the left of the vertical border 47 with a thickness difference of 70%.

Regarding FIG. 4C, although the degree of out-of-roundness also contributes to the reduction in stabilization time, there are also trade-offs here. As the design deviates from a circular design with increasing out-of-roundness or decreasing diametric aspect ratios beyond a certain level of out-of-roundness, manufacturing complexity increases and problems associated with ease of handling become more severe. Thus, it has been found that it is preferable to keep the degree of out-of-roundness or diametric aspect ratio above 80%, as defined in FIG. 4C in the isoparametric image 40 by the horizontal boundary 48. Thus, in accordance with the present invention, by remaining to the left of the vertical boundary 47, above the horizontal level 48 and below the corresponding portion of the upper contour line strip 46, a preferred region 49 (shown shaded) can be determined. where stabilization time considerations are taken into account as much as possible; wearing comfort: easy insertion/handling; as well as manufacturing complexity to provide optimal stabilization performance using differences in lens thickness and lens out-of-roundness, which in this case are given for a vertical lens diameter of 14.00 mm in accordance with the present invention.

In a preferred aspect of the present invention, one may choose to further improve lens performance by placing greater emphasis on one consideration over another, while still remaining within the previously described preference region 49. For example, if reducing stabilization time is considered more important than other considerations, designs can be prepared that have non-roundness and thickness differences that define the position in the lower right corner of the preferred area 49. If greater emphasis is placed on improving comfort as the most important consideration, thickness differences can be reduced, thereby increasing comfort through the choice of non-roundness and thickness differences thickness, which determine the position on the left side of the preferred area. Finally, regarding design considerations, if ease of insertion and/or manufacturing considerations are more important, the top of the preferred region will be selected and lens designs will be created that have a minimum degree of out-of-roundness and associated thickness differences that are within the preferred region .

As noted above, the vertical diameter selected for a set of combinations of out-of-roundness and thickness differences will provide a unique response surface. Increasing or decreasing the vertical diameter (ie, a new set of combinations of out-of-roundness and thickness differences) will result in changes to such response surface and a shift in the preferred region 49 primarily in the form of a vertical shift in the preferred region 49, as shown in FIG. 4D.

According to an exemplary embodiment, it is expected that increasing the vertical diameter will result in faster settling times, resulting in a corresponding upward shift 50 of the preferred region. Accordingly, as the vertical diameter decreases, there will be an increase in the stabilization time values and a downward shift of the preferred region 51 will occur.

Although any initial starting design can be used and further improved upon according to the methodology described in the present invention, it is preferable to start with a known design as a starting point and improve its functionality by modifying its out-of-roundness and introducing reductions in thickness differences to achieve a more comfortable, comfortable feel. but at the same time an effectively stabilized structure. Known designs may include designs in development, previously commercialized designs, or past designs.

As shown in FIG. 5, flowchart 500 begins at step 501, which first determines initial parameters for an initial lens design or uses predefined lens design parameters for an existing design. For a given design, the initial thickness differences are first calculated at step 502. This will be the starting point as well as the maximum value of the thickness differences and is accordingly referred to as 100% thickness differences. For a given initial lens design (circular or non-circular), the edge profile can be modified by changing aspect ratios to achieve increasingly non-circular variations of the original lens geometry. Starting with a given vertical diameter parameter, the diametric aspect ratio can be used to determine the horizontal diameter parameter for each set of values from 50 to 95% of the circular structure, and preferably from 60 to 95% of the circular structure, and more preferably from 80 to 95% of the circular structure at the stage 503. This procedure is repeated for each thickness variation from 50% to 100% of the original value using suitable thickness variation steps or increments and for each diametric aspect ratio variation up to no more than 50% out-of-roundness with appropriate out-of-roundness increments at step 504. After determining all combinations of diametric aspect ratios and thickness differences, step 505 calculates the stabilization time for each combination; At step 506 and at step 507, the matrix of values can then be populated and the corresponding isoparametric image created. Although the original design will produce different results for the isoparametric image of the settling time, similar or even identical results and trends can be expected for designs of the same set. The next step involves identifying the preferred area on the desired isoparametric image by determining the vertical boundary of the thickness differences between 50 and 100% depending on the maximum achievable level of comfort; determining the lower limit of non-circularity as the horizontal level for the preferred area depending on ease of handling and ease of manufacture; and finally determining the maximum desired isoparametric line for stabilization time that is equal to or less than the value of the isoparametric line for stabilization time of the normalized original structure to provide the same or, if necessary, more effective stabilization to ultimately select the optimal geometry, in the steps 508 and 509. If at step 508 it turns out that the area does not meet the requirements, you can then repeat the procedure for diameters that are larger or smaller than the original diameters to return to step 502 to ensure that such alternative diameters further improve comfort , handling and ease of manufacture. The procedure can be repeated in iterations to achieve the desired results.

By adding a stiffness profile as an additional design dimension, a design optimization methodology can be used in each of the three dimensions of the design space, contributing to the improvement that can be achieved by optimizing only the non-circularity and thickness differences in the combination. As shown in FIG. 6, the steps are similar to those shown in the flowchart in FIG. 5, but the addition of step 605 now increases the level of design complexity by adding the stiffness profile parameter as a third input parameter, thereby making the resulting lens of the methodology an optimized design for each of the three dimensions of the design space.

As shown in FIG. 6, flowchart 600 begins at step 601, which first determines initial parameters for an initial lens design or uses predefined lens design parameters for an existing design. Although the order of design parameter/component/size to be optimized can be varied, it is preferable to start with out-of-roundness/aspect ratio, followed by thickness differences, and then stiffness profile. Thus, an initial non-circular aspect ratio is first selected. For a given initial lens design (circular or non-circular), the edge profile can be modified by changing aspect ratios to achieve increasingly non-circular variations of the original lens geometry. Starting with a given vertical diameter parameter, the diametric aspect ratio can be used to determine the horizontal diameter parameter for each set of values from 50 to 95% of the circular structure, and preferably from 60 to 95% of the circular structure, and more preferably from 80 to 95% of the circular structure at the stage 602. The initial thickness difference can then be calculated at step 603. This will be the starting point as well as the maximum value of the thickness differences and is accordingly referred to as 100% thickness differences. This procedure is repeated for each thickness variation variation from 50% to 100% of the original value using suitable thickness variation steps or increments for each desired diametric aspect ratio variation up to no more than 50% out-of-roundness, typically with suitable out-of-roundness increments (preferably from 1 to 5%) at step 604. Once all combinations of diametric aspect ratios and thickness differences have been determined, the design can be further optimized by evaluating the effect of the stiffness profile on the design at step 605. In particular, applicants have discovered that additional benefits can be achieved for lens comfort , while achieving satisfactory rotational recovery to stabilize the lens through judicious material placement, especially when designing large diameter non-circular lenses with thickness variations present.

By continuing in this manner, it is possible to create an optimized stiffness profile that is reduced compared to typical toric lens stiffness profiles and thus improves comfort. These optimized stiffness profiles match the stiffness profiles of a non-toric lens while still providing sufficient stabilization. Because of the non-roundness and large diameter of these lenses, they are more likely to interact with the limbal region of the ocular surface topography. Due to changes in ocular surface geometry in this area, the interaction of the lens with the ocular surface will depend on the stiffness of the lens. This may result in bubbles forming under the lens or other situations such as lens discomfort, staining, or indentation in the conjunctival area. Thus, it also provides an opportunity to design lenses with improved performance by positively interacting with the limbal region. Bubbles formed when air is trapped (i.e., creating air pockets) under a contact lens while the lens is on the eye can occur with large diameter lenses with less than optimal stiffness profiles. While bubbles will dissipate over time due to the bubble passing through the permeable lens material, or simply due to the bubble escaping from under the lens as it moves, it is possible to minimize and/or reduce the occurrence of these bubbles by creating corresponding lens stiffness profile. Applicants have found that further reducing the stiffness profile to 50% of a previously optimized non-circular lens having a non-circularity of 50 to 95% and existing thickness differences of 0.1 to 0.4 mm can result in additional improvements in comfort, removal or significant reduction in the number of bubbles under the lens, while achieving satisfactory stabilization/recovery times. Applicants' testing has shown that this additional reduction in the stiffness profile is preferably between 30 and 50%, since values above 50% begin to negatively affect lens stabilization/restoration.

After initially defining the matrix set of variables, stabilization time for each combination is calculated at step 606 along with predicted comfort and degree of eye wrap at step 607; at step 608, the matrix can then be populated with values and a corresponding isoparametric image can be created. Although the original design will produce different results for the isoparametric image of the settling time, similar or even identical results and trends can be expected for designs of the same set. The next step involves identifying the preferred area on the desired isoparametric image by determining the vertical boundary of the thickness differences between 50 and 100% depending on the maximum achievable level of comfort; determining the lower limit of non-circularity as the horizontal level for the preferred area depending on ease of handling and ease of manufacture; and determining an ideal stiffness profile, measured by the area under the stiffness profile curve, wherein the upper limit is limited to geometric shapes whose effective areas are somewhat smaller than the standard toric effective area of the prior art, thereby achieving a measurable increase in comfort. On the other hand, the lower limit is limited by geometric shapes whose effective areas are minimized in the direction of the extremely comfortable nontoric lenses of the prior art, but minimized only to a level that still achieves proper stabilization as measured by rotational recovery time. Finally, in accordance with the present invention, determining the maximum desired isoparametric line for stabilization time, which is equal to or less than the value of the isoparametric line for stabilization time of the normalized initial structure, is carried out with the aim of providing the same or, if necessary, more effective stabilization to ultimately select optimal geometry, at steps 609 and 610. If at step 609 the area is found to be unsuitable, the procedure can then be repeated for diameters that are larger or smaller than the original diameters, using different thickness differences or stiffness profiles individually or in combination to , returning to step 601, verify that such alternative input values further improve comfort, handling, stabilization and recovery time, and ease of manufacture. The procedure can be repeated in iterations to achieve the desired and optimal results.

By adding a stiffness profile as an additional design dimension, design optimization can be achieved in each of the three design space dimensions, contributing to the improvement that can be achieved by optimizing only the non-circularity and thickness differences in the combination. Optimization of the design in the first two dimensions of the design space uses the design parameters obtained using the two input parameters of non-circularity and thickness differences, visualized and displayed graphically as the preferred region 49 shown in FIG. 4D. In accordance with the present invention, the optimized design in each of the three dimensions of the design space provides an additional stiffness profile parameter as an additional degree of freedom of the structure, resulting in a transformation of the preferred region 49 shown in FIG. 4D, from a two-dimensional structure space to a three-dimensional structure volume, for which many solutions can exist. This typical design volume 700 is shown graphically in FIG. 7. The three-dimensional structure volume 700 is defined in the same manner as the two-dimensional preferred region 49 shown in FIG. 4D. Returning again to Fig. 7, a preferred region 701 on the diametric aspect ratio-thickness difference plane has been determined which is equivalent to the preferred region 49 shown in FIG. 4D. The only difference between the preferred region 49 shown in FIG. 4D, and the preferred volume 700 shown in FIG. 7 is that we are currently defining the minimum 702 and maximum 703 acceptable conditions for the influence of the stiffness profile in addition to the optimal values for out-of-roundness and thickness differences. These upper and lower stiffness profile conditions are related to differences in thickness, since thickness is a component of both elements. Where the stiffness profile differs from the thickness differences, applicants have found that for a given non-circular lens with thickness differences, the location of the material is as important as the amount of material placed. In this way, additional reductions in the stiffness profile can be realized without negatively impacting stabilization/recovery time. In accordance with the present invention, applicants have found that the preferred minimum stiffness profile (702) is 0.021 MPa⋅mm ³ and that the preferred maximum stiffness profile (703) is 0.109 MPa⋅mm ³ .

It will be useful to provide a brief overview of some of the models used by the applicant in assessing the impact and optimizing geometric/mechanical configurations of the lens.

Rotational recovery model

As stated above, both rotation and stabilization are fundamental to astigmatic lens design. To better understand the impact of the stabilization function of a particular lens, applicant has developed and uses a numerical rotation and alignment model (denoted RCM) that simulates the rotation and alignment of contact lenses on the eye as a result of the interaction of the contact lens with the eye. Specifically, this model predicts lens displacement (rotation/translation) as a function of lens geometry interacting with the model's eye geometry. The model eye may represent an individually well-characterized eye or a composite eye geometry representing population averages. The model includes eyelid dynamics that impart force to the lens, and the material and geometric properties of both the lens and the eye are used to calculate the resulting displacement (rotation/translation) of the contact lens on the ocular surface. This model is effective in calculating the time required to stabilize the lens structure on the eye. The virtual lens can be tilted or shifted, and after a simulated blink, the time required to stabilize can be determined. Thus, changing the lens geometry will affect and change the resulting movement of the lens on the ocular surface, and the resulting measurements for different designs can then be compared and evaluated. Representative output of this model is shown in Fig. 8.

Eyelid comfort model

While stabilizing the contact lens on the cornea (i.e., the surface of the eye) is vital, comfort is equally important. The conjunctiva is the mucous membrane of the eye covering both the cornea and the inner surface of the eyelids and is highly vascularized and innervated, making it very sensitive to the presence of a contact lens. Because of this, the interaction of the contact lens with the eye, and in particular with the eyelid and cornea, can be a major factor in comfort. As shown in FIG. 9A-9F, an eyelid comfort model was used to evaluate various lens designs and the effect of each on comfort based on the interaction of the contact lens with the eyelid. This eyelid comfort model can predict both contact pressure and shear stress acting on the eyelid due to aspects of the mechanical design of the contact lens and their interaction with the ocular surface and the eyelid. Output using representative designs for the prior art nontoric lens 901 shown in FIG. 9A, and the prior art toric lens 903 shown in FIG. 9E are shown together with an optimized toric lens design 902 in accordance with the present invention as shown in FIG. 9C. Representative isoparametric lines shown in FIG. 9A, 9C and 9D correspond to increased contact pressure levels in the upper eyelid as a result of contact lens wear. The corresponding enlarged detail views (see FIGS. 9B, 9D and 9F) show the region of maximum peak eyelid stress for each design, and as can be seen, the lens of the present invention 902 can exert a contact pressure substantially lower than the existing toric lens 903 the prior art, and in accordance with the nontoric lens 901 of the existing art. As shown in FIG. 9C and 9D, the peak voltage state 922 for a lens in accordance with the present invention results in an equivalent peak eyelid voltage level to that of a nontoric lens 901 with a peak voltage state 921, as shown in FIG. 9A and 9B. The comparison of these two eyelid peak voltage states with the peak voltage state 923 as shown in FIG. 9E and 9F, in the century when it interacts with the prior art toric lens 903, shows significantly lower stress levels. In particular, by comparing peak tension regions 921 and 922 with that of 923, applicants have analytically shown that the peak tension state in the eyelid interacting with the lens of the present invention reduces the peak tension state by approximately 35% compared to the peak tension state in the eyelid. , interacting with a conventional prior art toric lens, and further found that the reduced peak stress state is very similar to that of a best-in-class non-toric lens in terms of comfort. In particular, even with different assumptions in the boundary conditions of the model, all differences between the present invention and the nontoric lens of the prior art were less than 10%. Applicants have thus been able to optimize a lens design in accordance with the present invention that stabilizes similarly to a prior art toric lens while achieving the comfort level (as measured by peak eyelid load) of a best-in-class non-toric lens. Virtual definition of lens wrap

Contact lens materials are extremely pliable, which can encourage the contact lens itself to wrap around the cornea, resulting in varying tension and thus the tension state of the lens itself. These varying states of tension can lead to discomfort for the lens wearer. By using the stress state within the lens and applying finite element methodology, lens design can be optimized to achieve a more uniform stress distribution within the lens across the ocular surface. Lens edge design can also have a large impact on comfort, and considering this in conjunction with other design variables is important to obtain a design that satisfies these often conflicting design requirements. The way the lens fits or wraps around the surface of the eye's cornea is an important determinant of successful lens design. As shown in FIG. 10, Evaluation and virtual evaluation of contact lens wraps can provide important results that will allow design optimization. Such optimization may address issues such as preventing central flexion of the lens design, or minimizing lens lift above the limbus to prevent bubble formation, or simply to further optimize and achieve a more uniform distribution of contact stress transferred by the lens to the corneal or ocular surface. This model uses finite element analysis to compare competing designs with known designs to better understand the stress state of the lens when placed on the corneal surface, as shown in FIG. 10. A typical non-toric lens (1001) has a fairly uniform contact stress state compared to a typical toric lens (1003) which has higher stress states in the region of the stabilizing zones. In accordance with the present invention, the contact stress state of the lens (1002) is more uniform like the nontoric lens (1001) even in the presence of stabilization zones.

The stiffness profile depends on both the thickness of the material and the elastic modulus of the material, so for a given material (e.g. elastic modulus), where the material is placed, both radially and circumferentially, can influence the stiffness profile. Likewise, different stiffness profiles can be achieved by simply changing the elastic modulus of the material. Since different material arrangements or configurations also affect thickness, the stiffness profile size is also associated with differences in thickness. Thickness profiles along multiple meridians taken together and combined with the elastic modulus of the material can be used to determine the stiffness profile. Thus, both the elastic modulus and the material arrangement can be varied individually or in combination to obtain different stiffness profiles. To approximate lens stiffness for an axisymmetric lens, the stiffness profile can be determined by multiplying the elastic modulus of the lens material by the square of the thickness taken along one meridian at individual radial positions. (see equation 1 below)

Stiffness profile = E × t ² Equation 1

Where E is the elastic modulus of the material

and t is the thickness.

The area under the curve of the various stiffness profiles for each meridian can be used as an indicator for the stiffness profile, and since lens comfort is related to stiffness, such area measurements can also be indicators for comfort. To approximate the area under a given curve, the thickness profile is divided into a fixed number of individual segments of width w along the radial dimension, with the stiffness of each segment calculated using Equation 1 and multiplied by the width w. The total area is then summed for each segment.

The modulus of elasticity of silicone hydrogel and non-silicone hydrogel contact lenses can range from 0.4 to 1.6 MPa depending on the composition and the presence or absence of silicone, with silicone hydrogel contact lenses typically having a higher modulus of elasticity than non-silicone hydrogel contact lenses lenses.

The series of three graphs shown in FIG. 11 shows various lens designs represented as separate finite element models showing various lens designs mounted on the surface of the cornea or eye (1104). In FIG. 11A is a cross-sectional view of a typical toric shaped lens (1103) mounted on the surface of the eye (1104), clearly showing the thickened area of the lens stabilization zone in the limbal region. In FIG. 11B shows a similar model with a nontoric lens shape (1101), clearly demonstrating the reduced lens thickness in the limbal region. In FIG. 11C shows a lens in accordance with the present invention (1102) with an optimized stabilization zone and larger diameter, as well as optimized out-of-roundness, thickness variations, and a reduced stiffness profile.

In FIG. 12A shows various stiffness profiles for both typical toric (1203) and non-toric (1201) lenses, along with the stiffness profile of two representative lenses in accordance with lenses of the present invention (1202a and 1202b). In this graph, the horizontal axis represents the radial profile of the lens, and the vertical axis represents the stiffness profile.

In both round and non-round lenses, as the larger and smaller lens diameters increase, changes in ocular surface geometry around the limbus become a factor to consider. In human eyes, this area of the limbus is typically located radially from the center of the eye at a distance of approximately 6 to 6.8 mm. The stiffness of the lens at this location is also important because it affects how the lens interacts with the ocular surface geometry. In this region, toric lenses are relatively stiffer due to the presence of stabilization zones. Applicants have determined that this interaction of the lens with limbal geometry is important, especially in connection with improving and optimizing stabilization or recovery time. An important consideration is determining how completely or definitively the lens will wrap and therefore follow the surface profile or, alternatively, be rigid enough to form a bulge over the limbal area. To provide a fair comparison and to note that all toric lenses are relatively stiffer in this area, we have excluded from the effective area the radial zone from 6.0 to 6.8 mm, where the ocular surface is most concave. This allows for more intelligent comparisons of the effective area under the stiffness profile curve when comparing one lens design to another, as well as when comparing different types of lens design, (i.e., nontoric versus toric). Other interactions with large lenses and the limbal area include problems such as blistering under the lens and lens discomfort, staining, and/or indentation in the conjunctival area. Applicants have found that this is another area in which optimization of the stiffness profile can be used to reduce and/or prevent bubble formation and improve the situation associated with discomfort caused by the lens, staining and/or indentation in the conjunctival region.

The methodology for calculating and optimizing the stiffness profile can be better understood with the help of an example, as shown in FIG. 12V and 12C. In FIG. 12B shows a typical lens stiffness profile based on its radial position from the center of the lens to its outer edge. In FIG. 12C shows the same graph, in which the area under the curve of the stiffness profile in the limb region is excluded (denoted as the missing area). The remaining area under the curve (denoted as normalized effective area) is the area used to compare the relative stiffness profiles of one lens configuration/type to another. It is the optimization (and reduction) of this effective area under the stiffness profile curve that realizes the third dimension of this design space. Applicants have calculated the effective area (ie, the effective stiffness index (E x t ² x w)) of a conventional nontoric lens without stabilization zones, as well as the effective area of a conventional toric lens with stabilization zones. These effective areas, which do not include the missing area under the curve at the limbal region (6.0 to 6.8 mm), range from approximately 0.04 to 0.05 ^MPamm3 for a conventional nontoric lens design and from approximately 0.10 to 0.11 MPamm ³ for traditional toric lens design. The large effective area of traditional toric lenses is due to the presence of stabilization zones, which tend to increase in thickness. Applicants have developed and optimized several lens shapes that provide equivalent stabilization performance but with reduced stiffness profiles, essentially resulting in approximately 35-50% reduction in the typical stiffness profiles of a traditional toric lens and thus increased comfort. In accordance with a further embodiment of the present invention, the applicants have discovered that by maximizing the ratio of the dropped area to the effective area, the performance of the lens can be further improved both in terms of comfort and in terms of reducing bubble formation. In accordance with the present invention, Table 1 below summarizes the interaction with both variable modulus and effective area reduction proposed by the applicants.

Depending on whether a lens material is used with a low or high modulus of elasticity, the optimized stiffness profile can range from 0.021 to 0.109 MPa × mm ³ , and when used in combination with optimized out-of-roundness and optimized thickness differences, it can provide both increased comfort and satisfactory stabilization.

In FIG. 13A and 13B show various tests of the time required for a typical lens (FIG. 13A) and a lens in accordance with the present invention (FIG. 13B) to reorient when artificially repositioned 45 degrees from the optimal stabilized position. As can be seen, there is a significant improvement when using a combination and optimizing the out-of-roundness, thickness differences and stiffness profile. In FIG. 14A and 14B show the lens angular position distribution for each of these trials 30, 60, and 90 seconds after the initial artificial 45 degree phase change. It should be noted that there is a significant reduction in the volume of distribution shown in FIG. 14B, which is for lenses in accordance with the present invention compared to FIG. 14A, which is typical for a standard toric lens on the commercial market.

By optimizing all three dimensions of the design in accordance with the invention of the applicants, the applicants have found that the stress state of the lens is more favorable as it relates to comfort, which has been confirmed by clinical trials, the reduction in bubble formation has also been confirmed by clinical trials, and the stabilization and recovery time of the lens is more than satisfactory.

Although the embodiments shown and described are considered to be the most practical and preferred, those skilled in the art will recognize that there are possibilities for departures from the described and illustrated established configurations of methods that can be used without departing from the spirit and scope of the present invention. The present invention is not limited to the specific structures described and illustrated, but is to be considered in accordance with all modifications within the scope of the appended claims.

Claims (15)

1. A non-truncated contact lens with rotation angle stabilization, containing: an optical zone configured to correct vision; a peripheral zone surrounding the optical zone and configured to provide rotation angle stability, such rotation angle stability being achieved by providing and optimizing an out-of-roundness component, a thickness difference component, and a stiffness profile component, wherein the out-of-roundness component includes a first effective dimension formed by the diameter of an inscribed circle that lies within a peripheral zone of the contact lens having a first center, and a second effective dimension formed by the diameter of an inscribed circle around a peripheral zone of a contact lens having a second center, wherein the ratio of the first effective size to second effective size is in the range of from about 0.6 to about 0.95, the thickness difference component has a maximum thickness and a minimum thickness and is determined by the difference between the maximum thickness and the minimum thickness, and the thickness differences range from about 0.1 mm to about 0.4 mm, and the stiffness profile component is defined as the effective area under the thickness profile curve obtained by multiplying the square of the lens thickness taken along the lens meridian at various radial positions by the elastic modulus of the lens material, wherein said effective area ranges from about 0.021 MPa x mm ³ to about 0.109 MPa x mm ³ . 2. The contact lens of claim 1, wherein the diameter of the inscribed circle is in the range of about 13.5 mm to about 14.5 mm. 3. The contact lens of claim 1, wherein the diameter of the circumscribed circle is in the range of about 14.0 mm to about 20.0 mm. 4. The contact lens of claim 1, wherein the ratio of the first effective size to the second effective size is in the range of about 0.8 to about 0.95. 5. Contact lens according to claim 4, in which the shape of the peripheral zone is asymmetrical. 6. The contact lens according to claim 4 or 5, wherein the first center and the second center coincide. 7. The contact lens according to claim 4 or 5, wherein the first center and the second center do not coincide. 8. Contact lens according to claim 7, in which the divergent centers are located on the same horizontal meridian. 9. Contact lens according to claim 7, in which the divergent centers are located on the same vertical meridian.

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