Intraocular lenses having zone-by-zone step height control

Abstract

To provide intraocular lenses having a zone by zone step height control.SOLUTION: A method and a system provide an ophthalmic device. The ophthalmic device includes an ophthalmic lens having anterior surface, a posterior surface and at least one diffractive structure including a plurality of zones. The at least one diffractive structure is for at least one of the anterior surface and the posterior surface. Each zone includes at least one echelette having one or more step heights. The step heights are individually optimized for each zone. To compensate chromatic aberration of an eye from a distance to a range of vision, a phase step height greater than the 2π phase step height may be employed and folded by a phase which is an integer multiple of 2π. Hence, the chromatic aberration of an eye may be compensated to improve vision from the distance vision to the near vision.SELECTED DRAWING: Figure 1A-1B

Description

Technical Field

[0001] The present disclosure generally relates to intraocular lenses, and more specifically to intraocular lenses having zones with zone step height control.

[0002] An intraocular lens (IOL) is implanted into a patient's eye either to replace the patient's natural lens or to supplement the patient's natural lens. The IOL can be implanted during cataract surgery to replace the patient's natural lens. Alternatively, the IOL can be implanted into the patient's eye to enhance the refractive power of the patient's own natural lens.

[0003] Some conventional IOLs are single focal length IOLs, while others are multifocal IOLs. Single focal length IOLs have a single focal length, i.e., a single power. An object at the focal length from the eye / IOL is in focus, while a nearer or farther object may not be in focus. The object is in perfect focus only at the focal length, but objects within the depth of focus (within a specific distance of the focal length) are still in focus to the extent that the patient can consider the object to be in focus. Multifocal IOLs have at least two focal lengths. For example, a bifocal IOL has two focal lengths (i.e., a far focus corresponding to the long focal length and a near focus corresponding to the short focal length) to improve the focus in two regions. In this way, the patient's distance vision and near vision can be improved. Conventional diffractive bifocal IOLs typically use a 0th diffraction order for far focus / distance vision and a 1st diffraction order for near focus / near vision. Trifocal IOLs have three foci (i.e., a far focus for distance vision, a near focus for near vision, and an intermediate focus for intermediate vision with an intermediate focal length between the focal length of the near focus and the focal length of the far focus). Conventional diffractive trifocal IOLs typically use a 0th diffraction order for distance vision, a 1st diffraction order for intermediate vision, and a 2nd diffraction order for near vision. Multifocal IOLs can improve the patient's ability to focus on distant objects and objects very close by. In other words, the patient's depth of focus can be enhanced. Trifocal IOLs have three foci (i.e., a far focus for distance vision, a near focus for near vision, and an intermediate focus for intermediate vision). The intermediate focus has an intermediate focal length between the focal length of the near focus and the focal length of the far focus. Multifocal IOLs can improve the patient's ability to focus on distant objects and objects very close by.

[0004] To fabricate conventional IOLs, optical design software is typically employed. The desired focal lengths and positions of zones on the lens surface are provided. Given these inputs, the entire lens is analytically optimized using the optical software. In other words, the diffractive structures of multiple zones are simultaneously optimized using analytical tools. As a result, an IOL can be provided.

[0005] While useful for addressing optical conditions, IOLs can suffer from various drawbacks such as longitudinal chromatic aberration and / or limited depth of focus. The various colors of light have various frequencies corresponding to various wavelengths. As a result, an IOL focuses light of various colors at various distances from the lens. There is a possibility that the IOL cannot focus light of various colors onto the patient's retina. The polychromatic image contrast of the IOL can be adversely affected. In addition, the depth of focus of the IOL may not be as large as desired. The vision of patients in a range further from the focal length can be adversely affected. Ultimately, an extended depth of focus (EDOF) may be desirable.

[0006] Accordingly, what is needed are systems and methods for improving IOLs. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0007] The method and system provide an ophthalmic device. The ophthalmic device includes an ophthalmic lens having at least one diffractive structure including a front surface, a rear surface, and a plurality of zones. The at least one diffractive structure is for at least one of the front and rear surfaces. Each zone includes at least one echelette having at least one step height. The step height is provided individually for each zone. The at least one step height is also folded back by a phase that is an integer multiple of 2π.

[0008] The lens can have the diffractive structure described above and have reduced chromatic aberration and a larger EDOF. As a result, performance can be improved.

[0009] To more fully understand the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings. Like reference numerals indicate like features. BRIEF DESCRIPTION OF THE DRAWINGS

[0010]

FIG. 1A-1B

FIG. 2

FIG. 3A-3B

FIG. 4

FIG. 5A-5B

FIG. 6

FIG. 7

FIG. 8

FIG. 9

DETAILED DESCRIPTION OF THE INVENTION

[0011] The exemplary embodiments relate to ophthalmic devices such as IOLs and contact lenses. The following description is presented to enable one skilled in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the exemplary embodiments and the general principles and features described herein will be readily apparent. The exemplary embodiments are mainly described from the perspective of the specific methods and systems provided in the specific embodiments. However, the method and system will operate effectively in other embodiments. For example, the method and system are mainly described from the perspective of IOLs. However, the method and system can be used with contact lenses. Phrases such as "exemplary embodiment", "one embodiment", and "another embodiment" can refer to not only multiple embodiments but also the same or different embodiments. The present embodiment will be described with respect to a system and / or device having several components. However, the system and / or device can include more or fewer components than those shown, and variations in the arrangement and type of components can be made without departing from the scope of the invention. The exemplary embodiments will also be described in relation to a specific method having several steps. However, the method and system will operate effectively with respect to different and / or additional steps and other methods having different sequences of steps that do not conflict with the exemplary embodiments. Accordingly, the invention is not intended to be limited to the embodiments shown, but rather to be accorded the widest scope consistent with the principles and features described herein.

[0012] The method and system provide an ophthalmic device. The ophthalmic device includes an ophthalmic lens having a front surface, a rear surface, and at least one diffractive structure including a plurality of zones. The diffractive structure is for at least one of the front and rear surfaces. Each zone includes at least one echelette having at least one step height. The step height is individually determined for each zone. The step height is also folded back by a phase that is an integer multiple of 2π.

[0013] Figures 1A-1B depict an exemplary embodiment of an ophthalmic device 100 that can be used as an IOL. FIG. 1A depicts a plan view of the ophthalmic device 100, while FIG. 1B depicts a side view of the ophthalmic lens 110. For clarity, FIGS. 1A, 1B are not drawn to scale and are for illustrative purposes only, showing only some features. The ophthalmic device 100 includes an ophthalmic lens 110 (hereinafter "lens") and haptics 102, 104. The lens 110 can be made of a variety of optical materials including, but not limited to, one or more silicones, hydrogels, acrylic resins, AcrySof®. The haptics 102, 104 are used to hold the ophthalmic device 100 in place within a patient's eye (not shown). In other embodiments, other mechanisms may be used to hold the ophthalmic device in the appropriate position within the eye. Accordingly, the haptics 102 and / or 104 may be omitted. For clarity, the haptics are not depicted in the remaining attached drawings. The lens 110 is depicted as having a circular cross-section in the plan view of FIG. 1A, although other shapes may be used in other embodiments. Although described in the context of an IOL, the lens 110 can be a contact lens. In such a case, the haptic 102 is omitted and the lens 110 is sized to otherwise remain on the surface of the eye.

[0014] The lens 110 may be a multifocal lens, but it does not have to be. The lens 110 has a front surface 112, a rear surface 114, and an optical axis 116. The lens is also characterized by a diffractive structure 120 and a base surface 121. The lens 110 may provide a base power, aberration correction, and / or other vision correction. The lens 110 is aspherical and / or annular and has the same or different base surfaces on the surfaces 112, 114, and / or other features not shown or discussed in detail for simplicity. One diffractive structure 120 is shown on the front surface 112, but the diffractive structure 120 may be disposed on the rear surface 114. In still other embodiments, the diffractive structures may be disposed on the front surface 112 and the rear surface 114. Such diffractive structures may be the same or different. The diffractive structure 120 may be a partial-aperture diffractive structure, but it does not have to be. Further, although shown as a physical diffractive structure, in other embodiments, the diffractive structure 120 may be formed by a change in the refractive index of the lens 110.

[0015] The diffractive structure 120 may provide a single focal length or multiple focal lengths. In some embodiments, the diffractive structure 120 is used to provide a bifocal (two focal lengths for near and far vision) lens 110. In other embodiments, the diffractive structure 120 may provide a trifocal (three focal lengths for near, intermediate, and far vision) lens 110. Quadrifocal or other multifocal lenses may also be provided. The diffractive structure 120 may be configured for a specific wavelength. For example, different zones 111 of the diffractive structure 120 may be configured for different wavelengths of light. Alternatively, the diffractive structure 120 may be designed for a single wavelength of light.

[0016] The diffractive structure 120 includes a plurality of zones 122A, 122B, 122C (collectively zones 122) corresponding to various ranges (i.e., various radii) at a distance perpendicular to the optical axis 116. Although three zones 122 are shown, the lens 110 may have a different number of zones. Zones 122A, 122B, and / or 122C are circles or annular rings along the surface from the minimum radius to the maximum radius from the optical axis 116. For example, in some embodiments, the diffractive structure 120 may have a ring diameter of the zones 122 set by Fresnel diffraction lens criteria. Alternatively, other criteria may be used to determine the size and position of each of the zones 122.

[0017] Each of the zones 122 includes a step or an echelette 124. The echelette 124 has a step height corresponding to a phase difference. The step height of the echelette 124 is the physical step height (h) multiplied by the refractive index difference (Δn) between the lens 110 and the surrounding medium. In other words, the step height = h·Δn. The phase difference φ of the echelette 124 is proportional to the step height divided by the wavelength λ. More specifically, φ = (2·π·h·Δn) / λ. Thus, a phase difference of 2π corresponds to one wavelength in the step height. Thus, the terms step height and phase are considered to be effectively synonyms herein.

[0018] One or more of the eshellets 124 in zone 122 are individually optimized. In other words, one or more features of the eshellets 124 in zones 122A, 122B, and / or 122C are determined for each of the zones 122A, 122B, and / or 122C independently of the features of the eshellets 124 in other zones. In some embodiments, the step height (phase) of the eshellets 124 within zone 122 is determined separately on a per-zone basis. Thus, the step height of each zone 122A, 122B, and / or 122C is determined independently of the step height of other zones. In other embodiments, additional or other features of the eshellets 124 may be configured separately on a per-zone basis. For example, the spacing between the eshellets 124 may also be independently controlled for each zone 122.

[0019] The features of the eshellets 124 of each of the zones 122A, 122B, 122C can be optimized independently based on selected criteria. For example, a particular focal length of the lens 110, a target focal position, the location and amount of constructive interference, a target phase, and / or other criteria can be used to separately determine the step height for each zone 122. These criteria can vary between zones 122. In other embodiments, these criteria can be the same for each zone 122. Since the positions of the zones 122 are different from each other, different step heights can be determined for different zones 122 even if the criteria remain the same.

[0020] In some embodiments, the phase (i.e., step height) of the eshellets 124 within each zone can be individually optimized such that each of the zones 122 actively interferes at various target positions. As a result, the depth of focus of the lens 110 can be improved. In some examples, a relatively uniform through-focus can be achieved. Each of the zones 122 can be optimized separately with respect to one or more of the focal lengths of the multifocal lens 110. For example, each of the zones 122 can be optimized to provide various intermediate focal lengths. Thus, the depth of focus can be improved.

[0021] Although it has been discussed in connection with configuring the eschelons 124 independently for each zone 122, one of ordinary skill in the art will recognize that not all of the zones 122 have to be configured that way. For example, in some embodiments, only the eschelons 124 of zones 122A and 122B can be separately determined. In other embodiments, only the eschelons 124 of zones 122A and 122C can be separately configured. In still other embodiments, the characteristics of only the eschelons 124 of zones 122B and 122C can be independently determined. In other embodiments, all of the zones 122 of the lens 110 can be separately operated. Thus, the particular zones 122 having eschelons 124 that are independently operated can vary between embodiments.

[0022] In addition to separate zone-by-zone optimization of the step height, the zones 122 can receive a phase wrap. The individually determined step height of one or more of the zones 122 can be large. The corresponding phase can exceed 2·π. In some cases, the optimized step height can correspond to a phase of at least 3·π, 4·π, or more. Thus, if the step height is large enough, the step height is wrapped by a phase of 2·π·n, where n is a positive integer. In some embodiments, the step height of the eschelons 124 can be reduced to provide a maximum phase of 2·π. Thus, in addition to being separately controlled, the step height of the eschelons 124 of each zone 122A, 122B, and / or 122C is wrapped. This reduction in the step height can reduce optical interference from light far from the optical axis 116. The phase wrap can also provide a negative dispersion that can partially or fully compensate for the positive dispersion of the material from which the lens 110 is formed.

[0023] The ophthalmic lens 110 can have improved performance. The ophthalmic lens 110 can be a multifocal lens. The ophthalmic device 100 can be used to treat conditions such as presbyopia. Other conditions such as astigmatism can be treated. The performance of the lens 110 can be improved by using the base surface 121, the asphericity of the lens 110, the annulus of the lens 110, the apodization of the eschellon 122, and other features of the lens. In addition, the lens 110 can have not only reduced chromatic aberration but also improved EDOF. By separately controlling the step height of the eschellons 124 within each zone 122, the image can be made to be in focus over a larger range of distances. Thus, the depth of focus can be improved. Since the eschellons are also in a folded phase, the chromatic aberration introduced by the lens 110 can be compensated. This use of superzones and phase wrapping can compensate for the eye's chromatic aberration due to the strong negative dispersion of the diffractive lens and correct the chromatic aberration up to a certain field of view from afar. Thus, the depth of focus can be increased while a more achromatic lens 110 can be provided. Ultimately, the performance can be improved.

[0024] The advantages of the ophthalmic lens 110 can be better understood with respect to several embodiments. FIG. 2 depicts a sag profile 130 of another exemplary embodiment of a diffractive structure including individually controlled zones and phase folding. Thus, the sag profile 130 and the diffractive structure 130 are interchangeably referred to. The diffractive structure 130 can replace the diffractive structure 120 within the lens 110. The sag profile 130 shows that there are zones 134, 136, 138 each including one or more eschellons 132. FIGS. 3A, 3B are graphs 140, 150 respectively depicting exemplary embodiments of the monochromatic and clear vision intensity versus focus shift of a trifocal lens 110 made by the diffractive structure 130. Curves 142, 152 are of one set of line pairs, while curves 144, 154 are of another set of line pairs having a double frequency. FIGS. 2 - 3B are not to scale and are for illustrative purposes only.

[0025] As can be seen from graphs 140 and 150, the through-focus modulation transfer function (MTF) curves 142 / 152 and 144 / 154 are shifted due to the per-zone control of the step height of the eschelons 132 within the sag profile 130. This shift compensates for the valleys within the MTF curve. Thus, the depth of focus of the lens incorporating the sag profile 130 is improved. Due to the phase folding of the diffractive structure 130, chromatic aberration can also be compensated for. As a result, the MTF is shown to decrease only slightly over the entire extended distance in graphs 140 and 150. Thus, the depth of focus and chromatic aberration correction of the lens 110 having the sag profile 130 can be improved. The performance of the lens 110 employing the diffractive structure having the sag profile 130 can be enhanced.

[0026] FIG. 4 depicts a sag profile 130' of another exemplary embodiment of a diffraction including individually controlled zones and phase folding. Thus, the sag profile 130' and the diffractive structure 130' are interchangeably referenced. The diffractive structure 130' can replace the diffractive structure 120 within the lens 110. The sag profile 130' indicates that there are zones 134', 136', 138' each including one or more eschelons 132'. FIGS. 5A and 5B are graphs 140' and 150' respectively depicting exemplary embodiments of the MTF versus focus shift of a trifocal lens 110 created by the diffractive structure 130'. Curve 142' depicts the monochromatic MTF, while curve 152' is that of the light-adapted MTF. FIGS. 4-5B are not to scale and are for illustrative purposes only. In the illustrated embodiment, the near power can be set by adding power to the lens 110, while the intermediate power can be provided by the per-zone optimization of the step height of the sag profile 130'. In addition, the step height of the eschelons 132' can be folded back by an integer multiple of 2·π. For example, the maximum phase corresponding to the eschelons 132' can be 2·π.

[0027] As can be seen from graphs 140’ and 150’, curves 142’ and 152’ provide an intermediate focus. This is due to separate control of the echelle step heights in zones 134’, 136’, and 138’ as shown in the sag profile 130’. Thus, the depth of focus is improved. Due to the phase folding of the diffraction structure 130’, chromatic aberration can also be compensated, and the depth of focus and chromatic aberration correction of the lens 110 with the sag profile 130’ can be improved. Thus, the performance of the lens 110 employing the diffraction structure with the sag profile 130 can be enhanced.

[0028] FIG. 6 is an exemplary embodiment of a method 200 for providing a multifocal diffractive lens with reduced chromatic aberration. For simplicity, some steps may be omitted, may be arranged alternately, and / or may be combined. FIGS. 7 and 8 depict sag profiles 170, 170’ of lenses designed using method 200. Sag profiles 170, 170’ are for illustrative purposes only and are not intended to represent a particular device. Referring to FIGS. 6 - 8, method 200 may be used to provide an ophthalmic device 100, a lens 110, and a diffraction structure 120. However, method 200 may be used with one or more other diffraction structures 130 and / or 130’’ and / or similar ophthalmic devices.

[0029] Method 200 can be executed using a system that includes one or more processors and memory. The one or more processors can be configured to execute instructions stored in the memory to generate and control some or all of the processes described in the accompanying drawings and below. As used herein, a processor can include one or more microprocessors, a field-programmable gate array (FPGA), a controller, or any other suitable computer device or resource, and the memory can take the form of volatile or non-volatile memory including, but not limited to, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), removable media, or any other suitable memory component. The memory can store instructions for programs and algorithms that, when executed by the processor, implement the functions described herein with respect to any such processor, memory, or component that includes a step of processing functions. Further, aspects of the method and system can take the form of a full hardware embodiment, a full software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software aspects and hardware aspects. Further, aspects of the method and system can take the form of software components executed on at least one processor and embodied in one or more computer-readable media having computer-readable program code embodied thereon.

[0030] The diffractive structure of the lens 110 is designed using steps 202 and 204. The step height of the echelette is determined by individually configuring each of the zones via step 202. Step 202 can be performed analytically by using a processor that executes instructions. For example, a desired target focal position, focal length, zone position, and / or other criteria can be provided as input to the optical grating and software for designing the optimization to be performed. As a result, an optimized step height corresponding to the optimized phase is determined independently for some or all of the zones of the diffractive structure to be formed. Although referred to as an optimization process, one of ordinary skill in the art will recognize that the determined step height may not be optimal for all possible sets of criteria used. Instead, the optimization process may use an analysis tool that determines the step height based on criteria provided by the user. FIG. 7 is a graph 170 depicting a simplified superzone sag profile 172 resulting from step 202. Profile 172 is simplified as a linear profile but will generally be curved. Thus, sag profile 172 has three zones. The optimization process resulted in an echelette of sag profile 172 having a large optimized step height. Sag profile 172 includes first and second orders as primary orders. For comparison, the sag profile 174 of a single-focus Fresnel lens and the sag profile 176 of a dual-focus diffractive lens are shown. Sag profile 174 utilizes the first order, while sag profile 176 utilizes the zero and first orders. The phase corresponding to the echelette of sag profile 172 has an optimized phase greater than 2·π.

[0031] The optimized step height is folded back via process 204 if the optimized phase exceeds 2·π. The phase used for folding back is a positive integer multiplied by 2·π. In the illustrated embodiment, all zones have a large optimized step height. Eventually, the optimized step heights of all zones are folded back. In another embodiment, the optimized step heights of only some zones may be folded back. FIG. 8 is a graph 170' depicting the resulting simplified sag profile 172' after folding back. Profile 172' is simplified as a linear profile but will generally be curved. Thus, all the asperities of sag profile 172' have a reduced phase. Also shown by the dashed line are the original curve 172 and the direction in which sag profile 172 is moved to form the final curve 172'.

[0032] The lens 110 is fabricated via process 206. Thus, a desired diffractive structure 120 having the sag profile 170' can be formed. Diffractive structures 120, 130, 130' and / or similar diffractive structures can be provided and their advantages realized.

[0033] FIG. 9 is an exemplary embodiment of a method 210 for treating a patient's eye condition. For simplicity, some steps may be omitted, arranged alternately, and / or combined. Method 210 is also described in connection with using the ophthalmic device 100 and the ophthalmic lens 110. However, method 210 can be used with one or more diffractive structures 130, 130', 170' and / or similar diffractive structures.

[0034] An ophthalmic device 100 for implantation into the patient's eye is selected via process 212. The ophthalmic device 100 includes an ophthalmic lens 110 having a diffractive structure 120 that is individually optimized and has a folded-back zone 122. Thus, a lens having diffractive structures 120, 130, 130', 170' and / or similar diffractive structures can be selected for use.

[0035] The ophthalmic device 100 is implanted into the patient's eye via step 204. Step 204 may include a step of replacing the patient's own lens with the ophthalmic device 100 or a step of enhancing the patient's lens with the ophthalmic device. Next, the treatment of the patient can be completed. In some embodiments, implantation of another similar ophthalmic device into the other eye of the patient can be performed.

[0036] By using method 200, diffraction structures 120, 130, 130', 170' and / or similar diffraction structures can be used. Thus, the advantages of one or more ophthalmic lenses 110 can be realized.

[0037] A method and system for providing an ophthalmic device have been described. The method and system have been described according to the illustrated exemplary embodiments. Those skilled in the art will readily recognize that there may be variations to the embodiments and that any variations will fall within the spirit and scope of the method and system. Thus, many modifications can be made by those skilled in the art without departing from the spirit and scope of the appended claims. According to aspect (1), an ophthalmic lens having at least one focal length, a front surface; a rear surface; at least one diffraction structure including a plurality of zones, each of the plurality of zones including at least one echelette having at least one step height, the at least one diffraction structure being on at least one of the front surface and the rear surface, the at least one step height being individually determined for each zone of the plurality of zones, and at least one diffraction structure, a particular echelette in a particular one of the plurality of zones has an optimized step height greater than 2π, the diffraction structure including a first echelette and a second echelette for representing the particular echelette, the first echelette having a step height of 2π, and the second echelette having a step height of the difference between the optimized step height and 2π, the ophthalmic lens. According to aspect (2), the at least one focal length includes a plurality of focal lengths such that the ophthalmic lens is a multifocal lens. According to aspect (3), each zone is individually optimized with respect to a part of the plurality of focal lengths. According to aspect (4), each zone is individually optimized with respect to the plurality of focal lengths. According to aspect (5), the at least one step height includes a plurality of step heights. According to aspect (6), the at least one step height is 2π or less. According to aspect (7), the at least one diffractive structure is incorporated into the front surface. According to aspect (8), each zone is individually optimized with respect to a plurality of target positions. According to aspect (9), a method for fabricating an ophthalmic lens having at least one focal length, which is executed using one or more systems each including one or more processors and a memory, the method comprising: designing at least one diffractive structure including a plurality of zones, each zone of the plurality of zones individually including at least one echelette having at least one step height, the designing of the at least one diffractive structure further comprising: individually optimizing each zone of the plurality of zones to provide at least one optimized step height having at least one optimized phase; and when the optimized phase exceeds 2π, at least one of the optimized step heights is folded back by a phase that is an integer multiple of 2π to provide at least one step height; and fabricating an ophthalmic lens using at least one step height of the at least one diffractive structure. The method includes the above. According to aspect (10), the at least one focal length is a plurality of focal lengths, and individually optimizing each zone further includes individually optimizing each zone with respect to at least a part of the plurality of focal lengths. According to aspect (11), the at least one step height does not exceed 2π. According to aspect (12), the at least one diffraction structure is incorporated into the front surface of the ophthalmic lens. According to aspect (13), the at least one diffraction structure is incorporated into the rear surface of the ophthalmic lens. According to aspect (14), individually optimizing each zone further includes individually optimizing each zone for a plurality of target positions.

Claims

1. 1. An ophthalmic lens having at least one focal length, Front and; Rear and; at least one diffractive structure including a plurality of zones, each of the plurality of zones including at least one echelette having at least one step height, the at least one diffractive structure being on at least one of the anterior surface and the posterior surface, the at least one step height being determined individually for each of the plurality of zones; An ophthalmic lens, wherein a particular echelette in a particular one of the plurality of zones has an optimized step height that exceeds 2π, and the diffractive structure includes first and second echelettes obtained after folding back the optimized step height that exceeds 2π by a phase that is an integer multiple of 2π, the first and second echelettes representing the particular echelette, the first echelette having a step height of 2π, and the second echelette having a step height that is the difference between the optimized step height and 2π.

2. The ophthalmic lens of claim 1 , wherein the at least one focal length comprises a plurality of focal lengths such that the ophthalmic lens is a multifocal lens.

3. The ophthalmic lens of claim 2 , wherein each of said zones is individually optimized for a portion of said plurality of focal lengths.

4. The ophthalmic lens of claim 2 , wherein each of said zones is individually optimized for said plurality of focal lengths.

5. The ophthalmic lens of claim 1 , wherein the at least one step height comprises a plurality of step heights.

6. The ophthalmic lens of claim 1 , wherein the at least one step height is less than or equal to 2π.

7. The ophthalmic lens of claim 1 , wherein the at least one diffractive structure is incorporated within the anterior surface of the ophthalmic lens.

8. The ophthalmic lens of claim 1 , wherein each of the zones is individually optimized for multiple target locations.

9. 1. A method for fabricating an ophthalmic lens having at least one focal length, executed using software by one or more systems, each including one or more processors and memory, the method comprising: and designing at least one diffractive structure comprising a plurality of zones, each zone of the plurality of zones comprising at least one echelette having at least one step height, the designing of the at least one diffractive structure further comprising: optimizing each zone of the plurality of zones individually to provide at least one optimized step height having at least one optimized phase, performed by one or more of the processors; and if the optimized phase exceeds 2π, at least one of the optimized step heights is folded back by a phase that is an integer multiple of 2π to provide at least one step height, the optimized step height being executed by one or more of the processors. designing an ophthalmic lens using the at least one step height of the at least one diffractive structure implemented by the one or more software; A method comprising:

10. the at least one focal length is a plurality of focal lengths; 10. The method of claim 9, wherein optimizing each zone individually further comprises optimizing each zone individually for at least a portion of the plurality of focal lengths, performed by one or more of the processors.

11. The method of claim 9 , wherein the at least one step height does not exceed 2π.

12. The method of claim 9 , wherein the at least one diffractive structure is incorporated on an anterior surface of the ophthalmic lens.

13. The method of claim 9 , wherein the at least one diffractive structure is incorporated into a posterior surface of the ophthalmic lens.

14. The method of claim 9 , wherein optimizing each zone individually further comprises optimizing each zone individually for a plurality of target locations, performed by one or more of the processors.

15. 1. An ophthalmic lens having at least one focal length, at least one diffractive structure including a plurality of zones, each of the plurality of zones including at least one echelette having at least one step height, the at least one step height being determined individually for each of the plurality of zones; An ophthalmic lens, wherein a particular echelette in a particular one of the plurality of zones has an optimized step height that exceeds 2π, and the diffractive structure includes first and second echelettes obtained after folding back the optimized step height that exceeds 2π by a phase that is an integer multiple of 2π, the first and second echelettes representing the particular echelette, the first echelette having a step height of 2π, and the second echelette having a step height that is the difference between the optimized step height and 2π.

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