Apodized iol with frustrated diffractive region

ES 2 392 869 T3

DESCRIPTION

Apodized intraocular lens with frustrated diffractive region.

Background

The present invention relates generally to ophthalmic lenses and more particularly to intraocular lenses (IOLs) that provide improved intermediate vision.

Intraocular lenses are routinely implanted in the patient's eyes during cataract surgery to replace the natural crystalline lens. Some IOLs employ diffractive structures to provide a patient with not only a far focus power, but also a near focus power, as described, for example, in WO 2006/060480 (Alcon, Inc.) . IOLs of this type can also provide a limited degree of intermediate vision due to the defocusing properties of the two primary lens powers (ie, the far and near powers).

Other ophthalmic lenses are known from WO 2006/047698 and US 5 117 306.

However, there is still a need for diffractive IOLs that can provide improved intermediate vision and, more particularly, there is a need for IOLs of this type that provide improved intermediate image quality without any significant degradation of distance and near vision. .

Summary

The present invention relates generally to diffractive ophthalmic lenses (eg, diffractive IOLs) that provide near and far focuses while directing a portion of the incident light to an intermediate location between the near and far sources. More particularly, such a diffractive lens may include a diffractive structure that is adapted to direct a portion of the incident light to the intermediate location. In many embodiments, the deflection of a part of the incident light to the intermediate location is achieved by providing a sufficient difference between the phase delays generated by two or more zone boundaries of the diffractive structure.

The invention is defined by claim 1.

In one aspect, the invention provides a diffractive ophthalmic lens (eg, a diffractive IOL) that includes an optic having an anterior surface and a posterior surface, wherein the optic provides a distance focus. A diffractive structure comprising a plurality of diffractive zones is disposed on at least one of those surfaces to provide a near focus. Each zone is separated from an adjacent zone by a zone boundary that imparts an optical phase delay to incident light. Furthermore, at least two consecutive zone boundaries (two zone boundaries separating a common diffraction zone from two different zones) are configured such that a difference between their associated phase delays for at least one wavelength of incident light is greater than about 1/20 wavelength (A g), and preferably greater than about ¹Λ wavelength (2g), for example in a range between 4 approximately 1/20 wavelength (Ag) and approximately 1 wavelength (11), to direct a part of the incident light to a location between the near and far spotlights.

In a related aspect, the zone boundaries comprise a plurality of steps, wherein at least two consecutive steps have a differential height adapted to provide a difference greater than about 1/20 wavelength, and preferably greater than about ¼ wavelength, for example in a range from about 1/20 wavelength to about 1 wavelength, in their associated phase delays.

In another aspect, the diffractive structure of the ophthalmic lens comprises a truncated diffractive structure that covers a part, rather than the whole, of a lens surface on which the structure is disposed.

In another aspect, in the above IOL the two consecutive zone boundaries exhibit the aforementioned differential phase delays for at least one wavelength in a range from about 400 nm to about 700 nm (eg, 550 nm).

In another aspect, the optics provide a distance focusing optical power in a range from about 6 diopters (D) to about 34 D. In addition, the diffractive structure provides a near focusing addition power in a range from about 2 D to about 4 D, for example in a range from about 2.5 D to about 4

ES 2 392 869 T3

D or in a range from about 3 D to about 4 D. The effective addition power of an IOL when implanted in the eye may be different from its nominal (actual) addition power. For example, the combination of corneal power and the separation between the cornea and the IOL can weaken the effective addition power of the IOL; for example, a nominal 4 D addition power can result in an effective 3 D addition power for the entire eye. In the following sections, unless otherwise stated, the addition power values ​​mentioned refer to the nominal (actual) lens addition power, which may be different from the effective addition power when the IOL is implanted in the eye.

In a related aspect, the optic is formed of a biocompatible material. Some examples of such materials include, without limitation, soft acrylic, silicone, hydrogel, or other biocompatible polymeric materials that have a required refractive index for a particular application. For example, in some embodiments the optics are formed of a cross-linked copolymer of 2-phenylethyl acrylate and 2-phenylethyl methacrylate, commonly known as Acrysof.

In another aspect, in the anterior ophthalmic lens at least one of the anterior or posterior surfaces includes a base profile that exhibits a selected degree of asphericity (e.g., one characterized by a conical constant in a range between about -10 and about -1000, for example in a range of about -10 to about -100) or of twist to provide improved image quality.

In another aspect, a diffractive ophthalmic lens is described that includes an optic that has an anterior surface, a posterior surface, and a diffractive structure comprising a plurality of diffractive zones arranged on at least one of those surfaces, wherein each zone is spaced apart. from an adjacent zone by a zone boundary. The optics provide a distance focus corresponding to the zero diffraction order of the diffractive structure and a near focus corresponding to the first diffraction order of the structure. In addition, the zone boundaries are characterized by a plurality of non-uniform step heights that provide non-uniform phase delays adapted to direct a portion of the incident light to a location between the near and far foci to improve intermediate vision. .

In a related aspect, the non-uniform step heights comprise the heights of at least two consecutive steps, each imparting a phase delay to incident light such that a difference between those phase delays, for at least one The wavelength of the incident light is greater than about 1/20 wavelength (Ai) (for example, in a range from about 1/20 wavelength to about 1 wavelength).

In a related aspect, in the anterior diffractive lens the optics provide a distance focusing optical power in a range from about 6 D to about 34 D (for example, in a range from about 16 D to about 28 D) and a near focus addition power in a range from about 2D to about 4K.

In another aspect, the diffractive zones are surrounded by a portion of the respective surface that is devoid of diffractive elements.

In other aspects, a diffractive ophthalmic lens (eg, an IOL) is disclosed comprising an optic having an anterior surface and a posterior surface, each of which is characterized by a base profile. The optics provide a far-focusing optical power (for example, in a range from about 6 D to about 34 D) and include a diffractive structure arranged on one of its surfaces that provides a near-focusing optical power (for example , in a range between about 2 D and about 4 D). The diffractive structure comprises a plurality of diffractive zones, at least two of which exhibit sufficiently different surface curvatures (for example, a difference in a range from about 10% to about 50%) to make a portion of the incident light on the optics aim at an intermediate location between near and far focuses to improve intermediate vision. For example, in some embodiments, the surface curvatures of at least two adjacent areas are sufficiently different to cause a portion of the incident light to be directed to the intermediate location.

In a related aspect, in the anterior ophthalmic lens the surface curvature of at least one of the zones differs by more than about 20% (eg, in a range between about 10% and about 50%) from the curvature. or surface curvatures of one or more adjacent zones.

In another aspect, the invention provides a diffractive ophthalmic lens (eg, an IOL) having an optic having an anterior surface and a posterior surface, wherein the optic provides a distance focus (eg, in a range comprised between about 6 D and about 34 D). A diffractive structure comprising a plurality of diffractive zones is arranged on at least one of those surfaces

ES 2 392 869 T3 to provide a near focus (eg, one associated with an addition power in a range from about 2 D to about 4 D). A surface of at least one of the diffractive zones exhibits an asphericity such that the diffractive structure directs at least a part of the incident light to an intermediate location between the near and far foci. Asphericity can be characterized, for example, by a conic constant in a range of about -10 to about -1000, for example in a range of about -10 to about -100.

In another aspect, in prior ophthalmic lenses one or more optical surfaces may include a base profile that exhibits a selected degree of asphericity or toricity to provide an improved quality of vision.

A further understanding of the invention may be obtained by reference to the following detailed description in conjunction with the drawings, which are briefly described below.

Brief description of the drawings

Figure 1A is a schematic cross-sectional view of an IOL according to an exemplary embodiment of the invention.

Figure 1B is another cross-sectional view of an IOL according to an embodiment of the invention, illustrating a diffractive structure characterized by non-uniform step heights for directing a portion of incident light to an intermediate focus,

Figure 2 is a schematic front view of the IOL of Figure 1B, illustrating a plurality of annular diffraction zones that form the diffractive structure,

Figure 3A is a schematic side view of a diffractive IOL according to another example that is not part of the invention, having an apodized diffractive structure,

Figure 3B is a schematic front view of the IOL of Figure 3A,

Figure 4A is a theoretical linear propagation function (LSF) calculated at an intermediate focus for a conventional diffractive lens having an apodized diffractive structure,

Figure 4B is a theoretical linear propagation function (LSF) calculated at an intermediate focus for an example lens according to the teachings of the invention, having an apodized diffractive structure,

Figure 5A shows the theoretical optical phase in the pupil of an apodized diffractive IOL lacking a frustrated diffractive structure according to the teachings of the invention, where the abscissa represents the square of the distance to the lens center and the ordinate represents the phase optics,

Figure 5B shows the theoretical optical phase in the pupil of an apodized diffractive IOL, where the abscissa represents the square of the distance to the lens center and the ordinate represents the optical phase,

Figure 6 is a schematic side view of a diffractive IOL according to an embodiment of the invention, comprising a diffractive structure having a central diffractive region with a surface curvature that is different from that of an adjacent zone, so that the structure diffractive would direct a part of the incident light to an intermediate focus,

Figure 7 is a schematic side view of a diffractive IOL according to another embodiment of the invention, comprising a diffractive structure having a central zone exhibiting an aspheric surface profile, and

Figure 8 is a schematic side view of a diffractive IOL according to another embodiment of the invention, having an anterior surface, on which is arranged a diffractive structure in accordance with the teachings of the invention, and a posterior surface that can exhibit a aspherical or, in some cases, toric base profile.

Detailed description

Referring to Figures 1A and 1B, an IOL 10 according to one embodiment of the invention includes an optic 12 having an anterior optical surface 14 and a posterior optical surface 16 disposed about an optical axis 18. Although in this embodiment Optical surfaces 14 and 16 are generally convex to provide the IOL with a biconvex shape, in other embodiments the IOL may have other shapes, such as plano-convex, plano-concave, or convex-concave. The curvatures of the anterior and posterior surfaces, together with the refractive index of the material that forms the lens, are selected such that the optic 10 provides an optical power of far focus, for example, in a range between about 6 diopters (D) and about 34 D (for example, in a range from about 16 D to about 28 D). In some cases, the far focus optical power of the lens may be within a

ES 2 392 869 T3 range from about -5 D to about 5.5 D.

A diffractive structure 20, which is disposed on a portion of the anterior surface 14, provides a near focus with an addition power, for example in a range of about 2 D to about 4 D (for example, in a range of between about 2.5 D and about 4 D or in a range between about 3 D and about 4 D). The effective addition power of the IOL when implanted in the eye may be different from its nominal (actual) addition power. For example, the combination of corneal power and the separation between the cornea and the IOL can weaken the effective addition power of the IOL; for example, a nominal addition power of 4 D can result in an effective addition power of 3 D for the entire eye. In the following sections, unless otherwise stated, the cited power addition values ​​refer to the nominal (actual) addition power of the lens, which may be different from the effective addition power when the IOL is implanted. in the eye.

The IOL 10 may further include a plurality of fixation members or haptics 22 that facilitate placement of the IOL in the eye of a patient. The optics are preferably formed of a biocompatible material, such as soft acrylic, silicone, hydrogel, or other biocompatible polymeric materials that have a required refractive index for a particular application. Haptics 22 can also be formed of suitable polymeric materials, such as polymethacrylate, polypropylene, and the like. In some embodiments, the haptics 22 may be formed integrally with the optic 12, while, in other embodiments, they may be formed separately and then coupled to the optic. In one embodiment, the optic 12 is formed from a cross-linked copolymer of 2-phenylethyl acrylate and 2-phenylethyl methacrylate, which is commonly known as Acrysof.

Referring to Figures 1A, 1B and 2, the diffractive structure 20 is composed of a plurality of diffractive zones 24 separated from each other by a plurality of steps 26 (the step heights are exaggerated for clarity). More particularly, each zone is separated from an adjacent zone by a step (eg, a step 26a separating the first zone 24a from the second zone 24b) that imparts a phase delay to incident light. As discussed below, in this exemplary embodiment a phase delay generated by stage 26a that separates the central zone (the first zone) from the second zone is different from a phase delay caused by the other stages, in such a way that a part of the incident light on the lens is directed to an intermediate location between the near and far foci.

In this exemplary embodiment, the diffractive zones comprise a plurality of annular zones whose limits are located radially in relation to the optical axis 18 according to the following relationship:

r¡ = r² + 2lf Eq. (1) in which:

i denotes the zone number (i = 0 denotes the central zone), l denotes the design wavelength, f denotes a focal length of the near focus, and r0 denotes the radius of the central zone.

In some embodiments, the design wavelength I is chosen to be 550 nm green light at the center of the visual response. Also, in some cases the radius of the center zone (r0) can be set to be 4Ϊ.

As discussed in more detail below, in some other embodiments the location of the boundary of one or more zones may deviate from that defined by the above relationship to further facilitate the action of directing a portion of the incident radiation to an intermediate location. between the near and far spotlights.

As noted above, in this exemplary embodiment the height of the step separating the first and second diffraction zones is different from the heights of the other steps (which, in this embodiment, are substantially uniform), such that the diffractive structure directs a part of the incident light to an intermediate location between the near and far foci. For example, the difference between the phase delay generated by step 26a and that generated by each of the other steps (i.e., steps 26b-26d) may be greater than about 1/20 wavelength (A q) and preferably greater than about 1/4 wavelength (Áq) for at least one wavelength of incident light, for example for at least 4 wavelengths in a range between about 400 nm and about 700 nm. By way of example, in one embodiment the step heights can be defined according to the following relationship:

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Step height = ^bl Eq. (2) ⁽«2 ^- «1⁾ in which:

b denotes the phase height l denotes the design wavelength, for example 550 nm, n2 denotes the refractive index of the optics, and n-ι denotes the refractive index of the medium surrounding the optics, where:

for step 26a, b is in a range of about -0.2 to about 0.2, and for the other steps, b is in a range of about 0.45 to about 0.55 and is preferably about 0.5.

Eq. (2) above indicates that the step height separating the central zone from its neighboring zone is different from the remaining step heights. More specifically, step heights other than that which separates the central zone from its neighboring zone are substantially uniform and produce an optical phase delay that results in the diffractive structure dividing the incident light approximately equally between the near focus. , which corresponds to the first order of the diffractive structure, and the distance focus, which corresponds to the zero diffraction order. On the contrary, the step height that separates the central zone from its neighboring zone generates a different phase delay that causes part of the incident light to be directed to an intermediate location between the near and far foci. In other words, the different phase delay generated by the step height between the central zone and its neighboring zone alters the contribution of the central zone to the light diffracted by the diffractive structure in such a way that, while the central zone continues to provide light to near and far foci, it directs part of the light to an intermediate location between these foci - the central zone is not a perfect contributor to the regular diffractive structure. This diffractive structure is also referred to here as "frustrated diffractive structure" and the diffraction it produces is here called "frustrated diffraction" to indicate that it modifies a regular diffraction pattern in order to deflect part of the incident light to an intermediate location between the foci of near and far. Furthermore, the intermediate location is here also referred to as the intermediate focus, although in many embodiments the convergence of light at the intermediate location does not result in as sharp a focus as those present in near and far focuses.

In some embodiments, the step separating the central zone from its neighboring zone is eliminated (i.e. the step height between the first and second diffraction zones is set to zero) to direct a portion of the incident light to the intermediate location. In other words, the first and second diffraction zones become a single central zone to generate an intermediate focus.

In some embodiments, in addition to having at least two consecutive step heights that generate phase delays that differ from one another by a value greater than a threshold (eg, greater than about 1/20 wavelength) , A plurality of step heights separating the diffractive zones of the diffractive structure of the IOL are apodized to shift the distribution of light energy between near and far foci as the size of the pupil changes, for example to produce glare. By way of example, Figures 3A and 3B schematically depict an example of IOL 28 according to an alternate example not forming part of the invention, which includes an optic 30 having an anterior optical surface 32 and a posterior optical surface 34 disposed around of an optical axis OA, and a diffractive structure 36 arranged on the anterior optical surface. Similar to the previous embodiment, the optic 30 provides a distance focusing power, for example in a range from about 6 D to about 34 D (for example, in a range from about 16 D to about 28 D) . In addition, the optic 30 includes haptics 38 that facilitate implantation in a patient's eye.

The diffractive structure 36 is formed by a plurality of diffractive zones 40 separated from one another by a plurality of steps 42a-42e. Similar to the previous embodiment, the diffractive structure generates a near focus corresponding to its first diffraction order and a far focus corresponding to the zero order of the diffractive structure. Furthermore, a difference between the phase delays generated by the consecutive steps 42a and 42b is configured, for example in a manner discussed above in connection with the previous embodiment, such that the diffractive structure directs a part of the incident light to a intermediate location between near and far foci. Furthermore, in this embodiment the heights of the steps 42b, 42c, 42d and 42e are apodized, that is to say that they vary as a function of their radial distance from the optical axis OA. For example, in this exemplary embodiment, the heights of these steps decrease as their distances from the optical axis increase. This apodization causes a shift in the distribution of light energy between near and far sources as the size of the pupil changes, that is, as the number of areas that contribute to the diffraction of light changes.

With continued reference to Figures 3A and 3B, the step heights of the zone boundaries of the structure

ES 2 392 869 T3 diffractive 36 can be defined according to the following relationships:

for the rung separating the central zone from the second zone (i.e. rung 42a): Rung height = ^bl Eq. (4a) ⁽«2 ^- «1⁾ in which:

b is the phase height with a value in the range of about -0.2 to about

0.2 and the other parameters are defined below, and for the other steps:

<td>Step height = ^bl F_z x J apodize⁽«2 _ ”1)</td><td>Eq. (4b)</td>

where b denotes the phase height with a value between about 0.45 and about 0.55 (preferably about 0.5), l denotes the design wavelength, for example 550 nm, n2 denotes the index of refraction of the optics, n-ι denotes the refractive index of the medium surrounding the optics, and fapodize denotes an apodization function.

A variety of apodization functions can be employed. For example, in some embodiments the apodization (fapodize) function can be defined according to the following relationship:

f - 1 _ {--Χ^η*°⁾ }^exp_r £ _r £ _r

J apodize t, \&gt; '^! inside i outside '' 'r outside ^ inside⁾ in which r, denotes the distance of each radial zone limit to the intersection of the optical axis with the surface, rin denotes the inner limit of the apodization zone which, in the previous embodiment, corresponds to the inner limit of the second diffraction zone, rout denotes the outer limit of the apodization zone, and exp denotes an exponent to obtain a desired reduction in step heights. Other details regarding the apodization of the step heights can be found, for example, in US Patent No. 5,600,142. Other apodization functions can also be employed. By way of example, alternative apodization functions described in a co-pending patent application entitled "Truncated Diffractive Intraocular Lenses", which has been assigned to the assignee of the present application, may be used.

By way of example, Figure 4A represents a profile of the calculated linear propagation function (LSF), corresponding to the intensity through the image of a linear object, for an apodized diffractive lens having a conventional apodized diffractive structure in where all the step heights are defined according to Equation (4b) above with a single value b (without a significant difference between the phase delays caused by the first two steps). Figure 5A shows the theoretically calculated phase for such a lens through the pupil of the lens as a function of the square distance to the center of the lens. By way of comparison, Figure 4B depicts the LSF profile of an apodized diffractive lens having a diffractive structure whose step heights are defined according to Equations (4a) and (4b) (that is, a lens exhibiting a " frustrated diffraction ”) and which has a larger central zone diameter and a lower phase delay in the first step than those of the conventional lens. And Figure 5B shows the theoretically calculated optical phase for such a lens through the pupil of the lens as a function of the square of the distance to the center of the lens. Referring back to Figures 4A and 4B, both LSF profiles were calculated for a pupil diameter size of 3mm. The LSF profile corresponding to the frustrated diffractive lens exhibits a very different center line focus that is not present in the LSF corresponds to the conventional apodized diffractive lens, indicating that the frustrated diffractive lens directs a part of the light energy to an intermediate location. between near and far spotlights and thus improves intermediate vision.

In some embodiments, the locations of one or more zone boundaries are altered relative to those defined by Eq. (1) above in order to provide missed diffraction, thus directing a portion of the incident light to an intermediate location. between the spotlights from near to far. For example, the location of one or more zone boundaries may differ from those dictated by Eq. (1) above by a factor within a range of about 20% to about 50%. In some embodiments, such a configuration of the zone boundary locations is used instead of adjusting the phase delays caused by the zone boundaries in order to achieve missed diffraction - although in other embodiments the boundary locations Zone and its associated phase delays can be configured to obtain frustrated diffraction. By way of example, the diameter of the central zone may be different, for example greater than that defined by Eq. (1) above, in such a way that the diffractive structure would direct part of the incident light to a location between the foci

ES 2 392 869 T3 near and far. For example, the radius of the central zone may be greater than, for example, a factor within a range of about 20 to about 50 percent.

In some embodiments, the step heights associated with more than one zone boundary can be adjusted, for example in a manner discussed above, to cause the diffractive structure to direct a portion of the incident light to an intermediate location between the spotlights. near and far.

Furthermore, in some other embodiments, instead of adjusting the height of the step that separates the central zone from its neighboring zone, one or more step heights associated with other zone boundaries are configured, for example in a manner discussed above, in such a way that the diffractive structure would direct a part of the incident light to an intermediate location between the near and far foci. For example, diffraction can be "thwarted" in one or more peripheral areas.

In some other embodiments, the surface curvature of at least one diffraction zone is different from that of at least one adjacent diffraction zone such that the diffractive structure would direct a portion of the incident light to an intermediate location. between the near and far spotlights. By way of example, Figure 6 schematically depicts an example of IOL 44 in accordance with an embodiment that includes an optic 46 having an anterior optical surface 48 and a posterior optical surface 50. The IOL further includes a diffractive structure 52 arranged in a part of the anterior surface. The optics 46 provides a far focus optical power, for example in a range of about 6 D to about 34 D, and a near focus add power, for example in a range of about 2 D to about 4 D. The diffractive structure 52 includes a plurality of diffraction zones 54 which are separated from each other by a plurality of steps, which may be uniform, apodized (in a conventional manner or in a manner according to the teachings of the invention). In this exemplary embodiment, the diffractive structure is characterized by a plurality of substantially uniform step heights.

In this embodiment, the surface curvature of the central diffraction zone (that is, zone 54a) is different (this is steeper in this case) from that of its adjacent zone (that is, zone 54b) in such a way that the diffractive structure directs a part of the incident radiation to an intermediate location between the near and far foci. By way of example, the difference between the surface curvatures of the two diffractive zones may be, for example, in a range from about 10% to about 50%, for example about 10%. Although in this embodiment the surface curvatures of the central diffraction zone and that of its adjacent zone are configured to direct a portion of the incident light energy to the intermediate location, in alternative embodiments other diffraction zones may be configured in this way. to provide an intermediate focus. Furthermore, in some embodiments the surface curvatures of more than two diffraction zones can be adapted, for example in a manner discussed above, to direct light to the intermediate location.

In some embodiments, the surface of at least one diffraction zone exhibits an asphericity designed to cause the diffractive structure to send a portion of the incident light energy to the intermediate location. By way of example, Figure 7 schematically depicts an IOL 56 comprising an optic 58 having a posterior optic surface 60 and an anterior optic surface 62 on which a diffractive structure 64 is disposed. Similar to previous embodiments, diffractive structure 64 is formed by a plurality of diffraction zones separated from one another by a plurality of approaches. Although in some cases (for example, in this exemplary embodiment) the steps are configured to cause missed diffraction, in other examples the steps may be substantially uniform or may be apodized in a conventional manner. Front surface 62 is characterized by a substantially spherical base profile. However, the surface profile of the central diffraction zone (zone A) exhibits an asphericity characterized, for example, by a conical constant in a range from about -10 to about 1000 (for example, in a range from about -10 and about -100) to make the diffractive structure deflect a part of the incident light energy to the intermediate location.

In some embodiments, the surface profiles of a plurality of diffraction zones (the surface profiles between the zone boundaries) exhibit selected asphericities, for example similar to those discussed above, to direct light to the intermediate location. This corresponds to creating deviations from straight lines for the sawtooth-like profiles shown in Figure 5B.

In some embodiments, the base profile of at least one of the optical surfaces of the IOL exhibits a selected degree of asphericity or toricity to provide improved quality of vision. For example, Figure 8 schematically depicts an IOL 66 according to another embodiment of the invention, including an optic 68 having an anterior optical surface 70 and a posterior optical surface 72 disposed about an optical axis 74. A frustrated diffractive structure 76 according to the teachings of the invention is disposed on the anterior surface. Furthermore, the posterior surface includes a profile that is substantially coincident with a spherical profile (shown by dashed lines) at small distances from the optical axis and exhibits an increasing deviation from that spherical profile as a function of increasing radial distance from the optical axis. In some embodiments, this

ES 2 392 869 T3 deflection can impart a selected degree of asphericity to the back surface, for example one characterized by a conical constant in a range from about -10 to about -1000 (for example, in a range from about -10 to about -1000 approximately -100), to provide improved quality of vision. In some other embodiments, the base profile of the surface on which the frustrated diffractive structure is disposed (eg, the anterior optical surface 20 in this case) may exhibit a selected degree of asphericity to improve the quality of vision. In addition, in other embodiments one or more surfaces of an IOL that has a frustrated diffractive structure, such as the IOL 66 above, may exhibit a selected degree of toricity to achieve improved quality of vision. For example, the anterior and / or posterior surfaces 70 or 72 of the IOL 66 may have a toric base profile.

In some embodiments, the frustrated diffractive IOL can be formed from a material that can provide some filtering of blue light. By way of example, the IOL can be formed from Acrysof Natural material. By way of further example, US Patent No. 5,470,932 describes polymerizable yellow dyes that can be used to block or reduce the intensity of blue light transmitted through the IOL.

Various ways of providing a frustrated diffractive lens are discussed in the above embodiments. It should be understood that each of the structural features used in the above embodiments to generate an intermediate focus can be employed individually or in combination with one or more other features. For example, in some embodiments, in addition to setting the step height that separates the central area from its adjacent area to generate an intermediate focus, the curvature of the central area can also be adjusted in a manner discussed above to direct a portion of incident light to the intermediate focus.

The various lenses discussed above can be manufactured using manufacturing techniques known in the art.

Those of ordinary skill in the art will appreciate that various changes can be made to the above embodiments without departing from the scope of the invention as defined by the claims.