AU2011232777A1 - Multi-zonal monofocal intraocular lens for correcting optical aberrations - Google Patents

Abstract

C -RPorbl\DCC\KMH\3915726.1 DOC-5110/2011 A multi-zonal monofocal ophthalmic lens including: an optic disposed about an optical axis including a first lens surface and a second lens surface disposed opposite the 5 first lens surface; the first lens surface including a plurality of zones, including: a first zone having a finite radial width and a sag surface characterized by a first base radius of curvature value and a first asphericity constant; and a second zone surrounding the first zone and having a finite radial width and a sag surface characterized by a second base radius of curvature value and a second asphericity constant; the radius of curvature values 10 are unequal, the asphericity constants are unequal, or the radius of curvature values are unequal and the asphericity constants are unequal; the zones configured to focus light entering the entire optic from a distant point source to substantially a single point, the lens having a maximum Diopter power difference between any two zones of the lens that is less than 0.75 Diopters. Figure 1

Description

Australian Patents Act 1990- Regulation 3.2 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Multi-zonal monofocal intraocular lens for correcting optical aberrations The following statement is a full description of this invention, including the best method of performing it known to me: P/00/0 11 5951 MULTI-ZONAL MONOFOCAL INTRAOCULAR LENS FOR CORRECTING OPTICAL ABERRATIONS Related Application [0001] The present application claims priority under 35 U.S.C §119(e) to provisional pplication No. 60/424,851, filed on November 8, 2002 under the same title. Full Paris :onvention priority is hereby expressly reserved. Field of the Invention [0002] This invention relates to intraocular lenses (IOLs) and, more particularly, to iulti-zonal monofocal IOLs that conect optical aben-ations for a variety of human eyes with ifferent corneas under a wide range of lighting conditions and that are effective even when ecentered or tilted. Background of the Invention [0003] In the perfect eye, an incoming beam of light is focused through the cornea and rongh the crystalixe lens in a way that causes all of the light from a point source to converge at e same-spot on the retina of th eye, ide y on the fovea area of the retina. This convergence cours because all of the optical -path lengths, for all light in the beam, are eqnal to each'other. Stated differently, in the perfect eye the time for all light to transit through the eye will be the same regardless of the particular path that is taken by the light. [0004] Not all eyes, however, are perfect. The consequences of this are that light path .engths through the eye become distorted and are not all equal to each other..Thus, light from a point source that transits an imperfect eye will not necessarily come to the same spot on the retina and be focused. [0005] As light enters and passes through an eye it is refracted at the anterior surface of the cornea, at the posterior surface of the cornea, and at the anterior and posterior surfaces of the :rystalline lens, finally reaching the retina. Any deviations that result in unequal changes in these optical path lengths are indicative of imperfections in the eye that may need to be erectedd. For example, many people are near-sighted because the axial length of their eyes are .oo long" (myopia). As a result, the sharp image of an object is generated not on the retina, but front of or before the retina. Hyperopia is a condition where the error of refraction causes rays f light to be brought to a focus behind the retina. This happens because the axial length is "too ort". This condition is commonly referred to as far-sightedness. Another refractive malady is ;tigmatism resulting from a refractive surface with unequal curvatures in two meridians. The fferent curvatures cause different refractive powers, spreading light in front and in back of the tina. [0006] Other "higher order" maladies of interest for vision correction include coma and iherical aberration. Coma exists when an asymmetry in the optical system causes unequal tical path lengths in a preferred direction. For example, the image.of an off-axis point object kes on a comet-like shape. For symmetrical systems, spherical aberration exists when rays at fferent radial heights from the optical axis focus at different axial locations near the retina. hereas coma exists only in asymmetric systems, spherical aberration can exist in both metric and asymmetric systems. Other, even higher order, aberrations exist. However, dies have show that spherical aberration is one of the strongest higher order aberrations in the iman visual system. Thus the retinal image may be improved if the spherical aberration is irrected according to known techniques. [0007] Studies have'also shown that there is a balance between the positive spherical erratioin ofthe cornea and the bgative spherical aberration of the crystalline lens in younger 'e. As ongrows older, the spherical'abeiiiti6n if the cri-ysalline lens becomesnmore positive, ,reasing the overall spherical aberration and reducing the image quality at the retina. [0008] An intraocular lens (IOL) is commonly used to replace the natural lens of a uman eye when warranted by medical conditions such as cataracts. In cataract surgery, the irgeon removes the natural crystalline lens from the capsular bag or posterior capsule and places it with an IOL IOLs may also be implanted in an eye (e.g., in the anterior chamber) ith no cataract to supplement the refractive power of the natural crystalline lens, correcting rge refractive errors. [0009] The majority of ophthalmic lenses including IOLs are monofocal, or fixed focal ngth, lenses that primarily correct refractive error. Most monofocal IOLs are designed with 2 ,pherical anterior and posterior surfaces. The spherical surfaces of the typically positive power OLs cause positive spherical aberration, inter aba. Thus, replacement of the crystalline lens with a typical monofocal IOL leaves the eye with positive spherical aberration. In real eyes with :omplex corneal aberrations, the eye following cataract surgery is left a with finite number of complexx lower and higher order abeirations, limiting the image quality on the retina. [0010] Some examples of attempts to measure higher order aberrations of the eye as an )ptical system in order to design an optical lens include U.S. Pat. No. 5,062,702 to Bille, et al., J.S. patent No. 5,050,981 to Roffman, U.S. Pat No. 5,777,719 to Williams, et al., and U.S. >atent No. 6,224,211 to Gordon. [0011] A typical approach for improving the vision of a patient has been to first obtain neasurements of the eye that relate to the topography of the anterior surface of the cornea. specifically, the topography measurements yield a mathematical description of the anterior |urface of the cornea. This comeal surface is placed in a theoretical model of the patient's eye vith an IOL replacing the crystalline lens. Ray-tracing techniques are employed to fimd the IOL design which corrects for the spherical aberration of the cornea. Ideally, if implanted with this :ustom IOL, the patient's vision will improve. [0012] Recently, Pharmacia Corp. (Groningen, Netherlands) introduced a posterior :apsule intraocular lens having the trade name TECNIS (Z9000) brand of Silicone IOL. The [ECNIS lens has a prolate anterior surface, which is intended to reduce spherical aberrations of be cornea.. This lens may be designed .using methods' described in U.. S.. Patent Number i,609,73 and PCT publication WO-01/89424, both to Norrby, et al. -Themethods in these mblications involve characterizing:aberrant cbrheal suffatbs as linear combination of Zeinike polynomials, and then modeling or selecting an intraocular lens which, in combination with a characteristic corneal surface, reduces the optical aberrations ocular system. The lenses resulting from these methods may be continuous aspherical surfaces across the entire optical zone and may be. used to reduce spherical aberrations .of the eye by introducing negative spherical aberration to counter the typically positive spherical aberration of the cornea. In these lenses, there may be a single base curve on which the aspheric surface is superimposed. As reported by J. T. Holliday, et al., "A New Intraocular Lens Designed to Reduce Spherical Aberration of Pseudophakic Eyes," Journal of Refractive Surgery 2002, 18:683-691, the Technics IOL has been found to be to improve visual contrast sensitivity at a frequency up to 18 cycles/degree. 3 [0013] The TECNIS brand of lens generally requires precise positioning in the capsular >ag to provide improved optical quality over a spherical IOL (c.f., "Prospective Randomized rrial of an Anterior Surface Modified Prolate Intraocular Lens," Journal of Refractive sugery, Vo. 18, Nov/Dec 2002). Slight errors in decentration (radial translation) or tilt (axial rotation) neatly reduces the effectiveness of the lens, especially in low-light conditions, thus making the ask of the surgeon more difficult. Furthermore, shrinkage of the capsular bag or other post mplantation anatomical changes can affect the alignment or tilt of the lens along the eye's )ptical axis. It is believed that the "typical" magnitude of decentration resulting from the mplantation of an intraocular lens in an average case, and factoring in post-implantation novement, is less than about 1.0 mm, and usually less than about 0.5 mm. Most doctors agree hat decentration of an IOL greater than about 0.15 to approximately 0.4 mm is clinically elevant (i.e., noticeably affects the performance of the optical system,.according to those skilled n the art). Similarly, the "typical" magnitude of tilt resulting from the implantation of an ntraocular lens in an average case, and factoring in post-implantation movement, is less than bout 10 degrees, and usually less than about 5 degrees. Therefore, in practice, the benefits of he TECNIS brand of lens may be offset by its apparent drawbacks in the real world. [0014] In view of the above, there remains a need for an intraocular lens that corrects for pherical aberrations in a variety of lighting conditions and is less sensitive to non-optimal states uch as decentration and tilt of the IOL. * Suinmarv of the InVeniidn -[0015] The present inveritidit provides a multi-zonal inonofocial ophthalmic lenst-thatis less sensitive to its disposition in the eye by reducing aberrations, including the spherical aberration, over a range of decentration. The monofocal ophthalmic lenses of the present invention may also be configured to perform well across eyes with different corneal aberrations (e.g., different asphericities). [0016] In one aspect of the invention, a multi-zonal monofocal opthalmic lens comprises an inner zone, an intermediate zone, and an outer zone. The inner zone has a first optical power. The intermediate zone surrounds the inner zone and has a second optical power that is different from the first power by a magnitude that is less than at least about 0.75 Diopter. The outer zone surrounds the intermediate zone and has a third optical power different from the second optical 4 power. In certain embodiments, the third optical power is equal to the first optical power. The phthalmic lens may comprise between 3 and 7 total zones, but favorably comprises between 3 id 5 total zones. However, ophthalmic lenses with more than seven total zones are consistent 'ith embodiments of the invention. [0017] In another aspect of the invention, a multi-zonal monofocal intraocular lens has an ptic with a plurality of concentric optical zones centered on the optical axis. The zones are adapted to focus incoming light rays to form the image from one object. The intraocular lens ptic includes an inner zone overlapping the optical axis of the lens that provides an image when ie intraocular lens is centered on the optical axis of the human eye. A first surrounding zone ancentric about the inner zone is adapted to compensate for optical aberrations resulting from planted intraocular lens decentration of greater than at least about 0.1 mm. [0018] The first surrounding zone may be configured to compensate for optical aberrations resulting from implanted intraocular lens decentration of greater than at least about .1 mm. The first surrounding zone may also compensate for optical aberrations resu ting from nplanted intraocular lens tilt of greater than at least about I degree. The power of th6 first arrounding zone preferably differs from the power of the inner zone by a magnitude that is less ian or equal to at least about 0.75 Diopter. In an exemplary embodiment, the inner zone omprises a spherical surface and the first surrounding zone comprises an aspherical surface. [0019] Another aspect of the invention includes a method of designing multi-zonal ionofocal opthalmic lens. The mhethbd comprises providing an optical model ofthe human eye. he . method further comnprise on ~6ptical iodel of a lens comprising an itnet- zone, an intermediate zone, an- outer- zone; and -zonal .design parameters: The method also- comprises adjusting the zonal design parameters based on an image output parameter for one or more non optimal states of the lens. [0020] The method may further include testing the intraocular lens over a wide range of clinically relevant corneal surface variations and dispositions. of optical elements in the eye's optical system using ray-trace analysis techniques. Furthermore, the method may be repeated to modify zonal parameters and achieve a better average optical performance. Examples of conditions of asymmetry that the lens will correct include decentration, tilt, and comeal aberrations. [0021] The invention, together with additional features and advantages thereof, may best 5 be understood by reference to the following description taken in connection with the accompanying illustrative drawings in which like parts bear like reference numerals. Brief Description of the Drawings [0022] Figure 1 is a schematic vertical cross-section of the human eye in a bright light environment and showing a pair of light rays passing through the optical system of the cornea md an implanted intraocular lens of the prior art to focus on the retina. [0023] Figure 2 is a schematic vertical cross-section of the human eye in a low light environment and showing a pair of light rays passing through the optical system of the cornea md the peripheral regions of an implanted intraocular lens of the prior art to focus in front of the etina. [0024] Figure 3 is a schematic vertical cross-section of the human eye in a bright light nvirodinent and showing a pair of light rays passing through the optical system of the cornea ind a decentered implanted intraocular lens of the prior art to focus on the retina. [0025] Figure 4 is a schematic vertical cross-section of the human eye in a medium light environment and showing a pair of light rays passing through the optical system of the cornea md a decentered implanted intraocular lens of the prior art to focus in front of the retina. [0026] Figures 5A and 5B are schematic plan and side views of a monofocal intraocular lens of the present invention illustrating concentric zones about an optical axis. 10027] Figur esA and 6B show .simulated modulatioi transfer functions for an aspheric, spherical ahd mbrlti-zoni monofocal IOLs'at a 5-mm pupil diameter with no decentration and 0.5 mm decentration, tespectively:- - [0028] Figure 7 show simulated aspheric, spherical, and multi-zonal monofocal IOL MTF curves at a 5 mm pupil diameter representing the respective average MTFs over 100 eyes varying in cornea] aberrations, IOL decentration and tilt, and small pupil size changes. Detailed Description [0029] The present invention encompasses an intraocular lens (IOL) design that reduces sensitivity to decentration within the eye while maintaining superior Module Transfer Function (MTF) performance for large pupils. The MTF is a measure of visual performance that can be plotted on a non-dimensional scale from a minimum of 0.0 to a maximum of 1.0 6 -ross a range of spatial frequencies in units of cycles per mm. The MTF is a measure of the 5ciency of "transferring" the contrast of an object into an image. The spatial frequency is versely proportional to the size of the object. Thus, small objects -at the limit of visual solution have high spatial frequencies than larger objects. The IOL described herein rmprises a multi-zonal monofocal lens in which the anterior lens surface, posterior lens face, or both comprises a plurality of zones that operate together on an incident wavefront produce a corrected ocular image. The different zones of the IOL of the present invention, described in greater detail below herein, generally have different mean spherical curvatures id/or Diopter powers, but the Diopter power differences between zones are far less than the pical 2 Diopter to 4 Diopter. design differences associated with multi-focal IOLs. In certain nbodiments, the maximum Diopter power difference between any two zones is less than at ast about 0.75 D, advantageously less than about 0.65 D. [0030] As used herein, the term "monofocal lens" is considered to be a lens in which ,ht entering the lens from a distant point source is focused to substantially a single Foint. In e case of a multi-zonal monofocal lens, light from a distant point source entering the lens nes substantially fall within the range of the depth-of-focus of a spherical lens having an luivalent focal length. [0031] As used herein in reference to the zones of a multi-zonal monofocal lens, the rms "optical power" and 'Diopter power" refer to the effective optical or Diopter power of a me ihen-.the lens is par 'ofi -ocular lens sysfei such as for example,'a cornea, a multi inal inonofocal IOL,. a -retina, .and the tnaterial surroundings -the'se components. 'This 9finiisd inay'include the effects f. the -vergence. or angle of light rays intersecting the IOL urface caused by the power of the cornea. This may include the total vergence from all >ptical surfaces in front of the multi-zonal monofocal IOL. In certain instances, an algorithm or calculating the Diopter power may begin with a ray-tracing a model of the human eye ncorporating a multi-zonal monofocal IOL. At a particular radial location on the IOL surface, Sell's law may be applied to calculate the angle of the light ray following the refraction. The optical path length of the distance between a point on the surface and the optical axis (axis of symmetry) may be used to define the local radius of curvature of the local wavefront. Using such an approach, the Diopter power is equal to the difference in indicies of refraction divided by this local radius of curvature. 7 [0032] IOLs of the present invention are designed to outperform certain IOLs of the prior art in low or moderate light situations over a larger range of implant positions. In practice, clinicians recognize that in the average case intraocular lenses implanted in the posterior capsule end up decentered from the optical axis of the host eye by between about 0.15-0.4 mm. Sometimes the decentration is greater as a result of poor implant technique or non-axisymmetric forces imparted by the host eye. Indeed, decentration of more than 0.5 mm, and sometimes up to 1.0 mm is experienced. IOLs of the present invention are specifically designed to exhibit superior performance in comparison to the prior art IOLs when decented by at least about 0.15 mm and in particular in low or moderate light conditions. In 'certain embodiments, IOLs of the present invention are designed to exhibit superior performance in comparison to prior art IOLs when decentered by greater than about 0.5 mm or greater than about 1.0 mm. The amount of decentering to be accommodated depends upon design constraints such as, for example, the accuracy of the surgical method to be used for implanting the IOL. Since the multi-zonal monofocal IOLs provide improved performance for decentered conditions, it is anticipated that patients will generally experience greater satisfaction with a multi-zonal monofocal IOL than with other prior art IOLs. [0033] Figure 1 is a schematic vertical cross-section through a human eye 20 having an IOL 22 of the prior art implanted therein. The optical system of the eye 20 includes an outer cornea 24, a pupil 26 defined by an orifice of an iris 28, the IOL 22, and a retina 30 forned on the'posterior inner surface of.the ocular globe 32.' In the. present application, the ,.terms anterior and posterior ate used in theit cbhveitionel sense;' anterior refets todtheifront -side of the eye -cioser to the cornea, while.posterior refers to the rear side closer to the retina. The eye defines a natural optical axis OA. The drawing shows the eye 20 in a bright light environment with the iris 28 constricted resulting in a relatively small pupil 26. [0034] The exemplary IOL 22 is adapted to be centered along the optical axis OA and within a capsular bag (not shown) just posterior to the iris 28. For this purpose, the IOL 22 may be provided with haptics or fixation members 34. An optic of the IOL 22 is defined by an anterior face 36 and posterior face 38. The optic may take a variety of configurations known in the art, such as the convex-convex configuration illustrated in Figure 5B. It should be understood that the present invention is not limited to posterior capsule-implanted IOLs. [0035] A pair of light rays 40 pass through cornea 24, pupil 26, the IOL 22. The rays 8 I40"ihan focus on the retina 30 along the optical axis OA. In the bright light environment shown, the light rays 40 pass through the mid-portion of the lens optic. The intraocular lenses of the prior art are relatively effective in focusing such light-rays at a point on the retina 30 along the optical axis OA. [0036] Figure 2 shows the eye 20 having the~ IOL 22 therein in a low light environment. In such situations, the iris 28 opens up creating a relatively large pupil 26 and permitting more light-to strike the IOL 22. A pair of light rays 42 passing through the peripheral regions of the.pupil 26 may be incorrectly refracted by the peripheral regions of the optic of the IOL 22 in the manner shown. That is, the light rays 42 focus on a spot 44 along the optical axis OA that is in front of the retina 30 by a distance 46. Such refraction is termed positive spherical aberration because the light rays 42 focus in front of the retina 30. A negative spherical aberration focuses light rays at the imaginary point along the optical axis OA behind the retina 30. Such aberrations can also occur in an eye with the natural lens still in place. For example, the crystalline lens in the aging eye may not refract ligh properly under low light environments. The practical result of such a condition may be a loss in image quality. [0037) Figure 3 illustrates the human eye 20 in a bright light environment such as shown in Figure 1. The IOL 22 centered along the optical axis OA is again shown in solid line, but is also shown in dashed line 22' representing a condition of decentration. As mentioned above, decentration involves a radial translation of tbe intraocular lens from a centered configuration on the natural optical axis OA. Th6 light rays 40 -pass dirough the cornea.- 24 and relatively -small pupil 26;.and are refracted through- the central region of tbe decentered intraocular lens optic 22'. That is, despite the undesirable decentration, the optic 22' performs well in bright light environments because light does not strike and refract through its peripheral regions. [0038] Figure 4 illustrates the eye 20 in a medium light environment, in which the iris 28 is somewhat larger compared to the condition shown in Figure 3, but is not fully expanded as seen in the low light environment of Figure 2. Under such conditions, a centered IOL 22 would likely perform adequately, but the decentered lens 22' will not. More particularly, a light ray 48 passing close to the iris 28 will strike and be incorrectly refracted through a peripheral region of the decentered optic 22' as shown. Intraocular lenses of the prior art have 9 varying degrees of sensitivity to decentration, and the situation shown in Figure 4 is for Illustration purposes only and does not represent any particular lens. [0039] However, it is believed that certain lenses designed to correct for spherical aberration, such as the TECNIS brand of lens, are relatively sensitive to small magnitudes of lecentration. Such lenses have a complex refractive surface that changes relatively :ontinuously across whichever face it is formed (i.e., anterior or posterior). This continuous efractive surface provides a negative correction for the positive spherical aberration on the :ornea, but when the lens is decentered the closely calculated balance between the two optical devices may be lost. Indeed, other optical aberrations such as coma and astigmatism inay be reated by the resulting mismatch. [0040] Figures 5A and 5B schematically illustrate in plan and side views a monofocal OL 60 of the present invention having an optic 62 and a pair of haptics or fixation members 4a, 64b extending outward therefrom. The optic 62 has a generally circular peripheral edge 6 and a plurality of concentric annular refractive bands or zones formed thereon. The eripheral edge 66 is desirably an axially oriented edge with thickness, as seen in Figure 5B, Though curved or angled edge surfaces, or combinations thereof, are possible. The optic 62 as an anterior face 68a and an opposite posterior face 68b separated by the peripheral edge 6. It should be understood that the refractive zones can be formed on either the anterior or osterior face, or in some cases as a combination of both faces. A central and inner zone 70 entered on the optical axis GA extends-outward to a:radius of ri,.at least one intermediate one 72 surrounds the inner zone 70 atii.extends outward to a radius of r2, and an outer zone 4 surrouiids the intorniddiate ~zone 72 incf exteiids therefr'om to the oter periphery 6 of tie optic 62 and a radius of r 3 . Desirably, r, is between about 1-1.5 mm, r2 is between about 1.5 2.2 mm, and r 3 is about 3 nun. More desirably, r2 is about 1.4 mm and r2 is about 2.0 mm. In certain instances, it may be desirable that r 3 is greater than 3 mm, for instance in order to preclude undesired edge effects. . [0041] The inner zone 70, intermediate zone 72, and outer zone 74 may have surfaces hat are either spherical or aspherical in shape. The intermediate zone 72 may comprise a combination of annular zones, although a single annular zone is generally desirable. In certain -mbodiments, the inner zone 70 is spherical, the intermediate zone 72 is aspherical, and the :>uter zone 74 is also aspherical. 10 [0042) The power of the inner zone 70 dominates the visual performance of the eye ihen the pupil is small, such as in bright daylight situations. The intermediate zone 72 is at :ast designed to help correct aberrations of the IOL when it is decentered, tilted, or otherwise n a non-optimal state. The power of- intermediate zore 72 is extremely close to that of the' nner zone 70. The outer zone 74 may be aspherical and designed to minimize the spherical berrations natural to spherical monofocal IOLs. [0043] Preferably, the intermediate zone 72 has a correction power that is less than the orrection power of the inner zone 70. When a prior art IOL is decentered (Fig 4), peripheral ight is too strongly refracted and focuses in front of the retina. However, the intermediate one 72 of the multi-zonal monofocal IOL 60 is used to reduce surface power, redirecting the ight ray 48 to the focal point on the retina. The intermediate zone 72 may also provide correction in cases of tilting of the lens within the typical range of at least about 1 to 10 legrees, depending upon design constraints such as, for example, the accuracy of the surgical nethod to be used for implanting the IOL. [0044] The IOL 60 is considered to be a monofocal lens because the relative refractive >owers of the zones 70, 72, and 74 are close to one another and within the range of the depth )f-focus of typical spherical monofocal IOLs. In this context, a "monofocal" lens is one in which discrete adjacent regions or zones have a maximum difference in refractive power of ess than at least about 0.75 Diopter. The refractive power of any one zone may be interpreted. 3s the mhean power within that z6ne. It should also be understood that discrete adjacent zones loes.'not neessarily mean that there. is a sharp physical transition therebetwe'en rather the rnanufactuiing process iay be designed to eneraliy provide a iooth transition bewee adjacent zones. [0045] The IOL 60 may be fabricated from materials used in the art, such as silicon, acrylic, or Polymethylmethacrylate (PMMA), or any other material that is suitable for use in or on a human eye. Materials may also be selected so as to provide a desired optical performance. For instance, the refractive index is known to vary with different materials and may, therefore, be used as a design parameter for attaining a desired optical performance or affect from the IOL 60. [0046] The IOL 60 may also be used in conjunction with other optical devices such as diffractive optical elements (DOE). For example, the anterior lens surface of the IOL 60 may 11 comprise a multi-zonal surface and the posterior lens surface may contain a DOE such as a liffractive grating, or visa versa. Alternatively, the multi-zonal surface itself may comprise a DOE such as a diffractive grating. The DOE may also be used, for example, to correct for :hromatic aberrations or to improve the performance of the IOL 60 when displaced from the optimal position (e.g., centered and normal to the optical axis). In certain embodiments, the DOE is disposed over only a portion of the one of the IOL surfaces. For example, the DOE nay be disposed over the intermediate zone 72 and used as an additional parameter for mproving the performance of the IOL 60. [0047] The IOL 60 may be designed to have a nominal optical power suited'for the >articular environment in which it is to be used. It is anticipated that the nominal optical yower of the IOL 60 will generally be within a range of about -20 Diopters to at least about 35 Diopters. Desirably, the optical power of the IOL 60 is between about 10 Diopters to at east about 30 Diopter. In certain applications, the optical power of the IOL 60 is approximately 20 Diopters, which is a typical optical power for the natural crystalline lens in a muman eye. [0048] Under low light environments, such as night-time, the human eye has a larger >upil (about 4.5-6 mm in diameter) and hence has a large spherical aberration (SA) that blurs the mage. Clinically, the large-pupil eye is reported to have a lower contrast sensitivity and ometimes lower visual acuity. The TECNIS brand of lens has been reported to perform better lan spheical IOLs.in low Jigit environments as judged by visual contrast sensitivity and visual cuity.. According to simulations, however,'this spherical design is sensitive to decentration. A action of a millimeter decentration of sudh IOLs -from the optical axis may draiatically break' he balance of SA between IOL and cornea, and thus seriously degrade the eye's vision. [0049] The inventors have discovered that spherical aberration can be reduced for both )n-design and off-design conditions by forming a lens surface to have a multi-zonal structure, with each zone having different surface parameters, for example, the base radius of curvature. In contrastt with the prior art single continuous aspheric surface, such as the TECNIS brand of lens described above, the surface sag of the IOL 60 (i.e. multi-zonal surface contour) may be determined using an equation that changes across the lens. In accordance with an exemplary embodiment of the present invention, the surface sag at any radius from the optical axis for an ith sone is given by the following equation: 12 C r2 rM Sag= *r +( y*(r-,)21+FT *(r-r,..,)2; 1 ( 1(1+ K,)* C,2* r 2 where C, Ki, and r 1 are the base radius of curvature, the asphericity constant, and the eight of the ith zonal surface. Further, the Bjs and Tjs are optional boundary parameters that :an be used to connect the zonal surfaces smoothly. The variable M is an integer that determines iow smoothly one zone transitions to another. This work makes use of a published finite eye nodel to represent the "nominal" eye for IOL design (see, Liou H.L. and Brennan N.A.,. 'Anatomically Accurate, Finite Model Eye for Optical Modeling, J Opt Soc Am A, 1997; [4:1684-1695). [0050] For posterior chamber IOL design, the asphericity constant K, in the inner zone T0 (Figure 5A) is preferably zero (i.e., the inner zone 70 comprises a spherical surface). The >ase radius of curvature C, in the inner zone 70 is considered to be the base surface power of the ens. There are preferably at least three zones (i 3) to achieve enhanced perform nce for a 6 nm diameter pupil size. A preferred range of the number of zones is between at least about 3-7, nore preferably between 3-5; however, larger numbers of zones may be used of particular design :onditions. The parameters in the outlying zones can be optimally determined such that each .onal surface refracts more of the light rays in that particular zone to the focus set by the inner one. This process canA be achieved -by the .aid of a commercial optical ray tracing design software, such.as ZEMAX optical design program fron ZEMAX. Development -Corporation 4991 Merenaialvd. Suite.207, San Diego, CA,.921177320). [0051] i general, the base curves in at least two zones are different (preferably the inner and intermediate zones), though all zones may have different base curves. Desirably, the anterior surface has three zones, each having a different base radius of curvature. The posterior surface is a one zone spherical surface. [0052] Table 1 provides an example of a multi-zonal monofocal IOL consistent with the. present invention. The values of the parameters given below are for an IOL with an overall Diopter power of 20 having 3 zones (i = 3) on the anterior surface and one zone on the posterior (i= 1). 13 Table I: Surface parameters of a 20D multi-zonal structured IOL interior surface Symbol i= 1 i=2 i=3 >aamter onal outer radial r; (rum) 1.414 2.000 3.000 oundary, mm onal curvature of C; 0.08614900000 0.0751110000000 0.05055500000000 adius, I/mm (1/mm) onal asphericity Ki 0.00000000000000 -1.5931120000000 8.90504900000000 4=3 Bio 0.00163052185449 0.01542174622418 0.11151991935001 B, -0.0024465216312 -0.0241315485668 -0.0611825408097 B V 0.00122363035200 0.08421200000000 0.00963200000000 B1 -0.0002040000000 -0.1293190000000 0.00399800000000 TI 0.00000000000000 .02774300000000 -0.0571790000000 T- -0.0004750000000 -0.1375720000000 0.13027200000000 To3 0.00007700000000 0.23032800000000 -0.0800460000000 'osterior surface = - -- rampter. - . . . - -.

56nal outer radial ri(mm) 3.000 - -- *-. Oundary *u., -M" . Zonal curvature of 0.0636027120000 radius, i/mm (1/mrm) Zonal asphericity Ki 0.00000000000000 M=0 N/A Notes: 1. IOL refractive index at 35* is 1.47; 2. 1OL central thickness is 0.977 mm. 3. IOL nominal base power = 20D 14 [0053] Figures 6A and 6B illustrate the IOL performance the multi-zonal monofocal lens own in Table 1 in terms of the simulated modulation transfer functions as compared to both a berical lens and an aspheric lens (the TECNIS brand of lens). These simulated results are sed on a 5 mm pupil diameter with no decentration (Figure 6A) and 0.5 mm decentration igure 6B). Figure 6A illustrates'the performance for each type of lens when the lenses are ecisely centered within the eye. In Figure 6B, the performance of each type of lens is ustrated when the lens is decentered from the optical axis of the eye by 0.5 mm, a condition at is not uncommon under realistic conditions. [0054] In comparing Figure 6B to Figure 6A, it can be seen that with decentration, both e aspheric and multi-zonal monofocal designs suffer a large loss in image quality (e.g., MTF). however, the multi-zonal loss is less compared to the aspheric design. Observe in Figure 6A at the aspheric and multi-zonal MTFs are significantly higher compared to the standard oherical surface design. The price paid for the significant enhancement of image quality is the ,nsitivity to non-nominal conditions (e.g., decentration) shown in Figure 6B. However, some improvement in the non-nominal condition can be achieved by this novel use of zones in the -sign of an improved monofocal IOL. The price paid for the reduction in non-nominal ,nsitivity is the slightly lower multi-zonal design MT compared to the aspheric MT shown in igure 6A. Never-the-less, the multi-zonal MTF remains significantly improved compared to te spherical design MTF. -[00551 Figure~7 illustrates the results of a'Monte Carlo simulation in the form of plots of Ie average MV performance for sherical, aspheric,.and multi-zonal.nonofocal IOLs based on . ver 100 different eyes and'under varying coiditions of cornea. aberrations, IOL decentration, Lnd IOL tilt. The simulation was conducted using a 5 mm nominal pupil diameter. The results ::ompare the average performance of the various types of lenses under simulated, real-world conditions. [0056] In clinical practice, many non-nominal conditions exist. These include corneas with different aberrations, different amounts of IOL tilt and decentration, and different pupil sizes for a nominal lighting condition. Other conditions may apply in more unique circumstances. Randomly selected values of the above "conditions" were selected, individual MTFs calculated, and the average MTF tabulated. In effect, this procedure simulates the general clinical population and assesses the complex interaction of the IOL surface design and 15 aberrations induced by the non-nominal conditions. [0057] Figure 7 shows the results of such a "clinical simulation", comparing the aspheric, berical, and multi-zonal designs. Figure 7 suggests that the aspheric design will improve the TF at lower spatial frequencies compared to the spherical design. From the patient's ,rspective, objects will have a higher contrast and color will appear richer. Figure 7 predicts at the multi-zonal design will provide even more improvement over a wide range of spatial quencies. The patient should experience both improved contrast and visual acuity. The latter related to changes in MTF at about 100 cycles/mm. As expected, when averaged over an tire clinical population; the multi-zonal design provides more improvement compai-ed to an pheric design, even though the multi-zonal design is slightly lower in performance in the nominal condition (Figure 6a). [0058] In certain embodiments, a method of designing a multi-zonal monofocal IOL mprises providing an optical model of the human eye. The model may include a corona, an s, the IOL 60, a retina, and any liquids, substances, or additional devices between the these mponents. The model may also include various system design parameters such as the spacing tween components and refractive index values. [0059] The method further comprises providing an optical model of a lens comprising an ner zone, an intermediate zone, an outer zone, and zonal design parameters (e.g., the IOL 60). ie zonal design parameters for each of the zones may include, but are not limited to, i radius of rveture, surface polynomial coefficients,.inner radius,.outer radius, refractive index, and DOB aracteristics., In certain embodineits, the model mayinclude additional zones along with their irresponding paianisters. One of the zonal desigri'parameter may also include the number of ones in the lens. The model may comprise the zones and zonal design parameters for an interior surface of the lens, the posterior surface of the lens, or both surfaces of the lens. [0060] The method further comprises adjusting the zonal design parameters based on an nage output parameter for one or more non-optimal states of the lens. Examples of non-optimal states include, but are not limited to, IOL decentration and tilt, and different corneal aberrations !.g., different corneal asphericities). Examples of image output parameter include, but are not mited to, the Modulation Transfer Function, spot radius, and/or wavefront error. Alternatively, plurality of output parameters may be used for evaluation while adjusting the zonal design arameters. 16 [0061] With the IOL in a non-optimal state, zonal design parameters such as the number zones and zone radii may be adjusted to correct any aberrant light rays entering the system trance pupil. For example, in the case of IOL decentration and a three-zone lens, the first zone dius and second zone radius are chosen such that the second zone falls within the entrance tpil. The zonal design parameters for the zones exposed by light entering the system entrance ipil may be adjusted to compensate for the aberrations produced by the non-optimal state. eferably, the zonal design parameters are adjusted until the image output parameter obtains an >timized or threshold value. [0062] The method may also include adjusting the zonal design parameters and/or the her system design parameters of the optical model based on the image output parameter for an >timal state of the lens. Such an optimal state would preferably represent a condition in which e IOL is centered along the optic axis of the eye and normal thereto. [0063] The method may be realized using optical design software that is resides on a >mputer or other processing device. The optical design software may be used to pumedcally y-traces various sets of light rays through optical model and that evaluates the image formed i the retina. Recognizing that the modeled cornea has finite aberrations, the design parameters the multi-zonal monofocal IOL may be adjusted to improve the quality of the image formed i the retina in terms of the image output parameter or in terms of a plurality of image output irameters. - (0064] The resulting lens froin this design. niay produce slightly lower retinal image Liality when'placed in-the opti ma state as compared tothe optimal design in the optimal-stat. .owever,. such a-on optimal state -design will still-allow a lensto be produced that provides ignificantly better performance than that possible using spherical optics. Thus, the non-optimal tate design provides superior performance over a greater range of non-optimal conditions as ompared to the initial optimal-design. [0065] In certain embodiments, additional non-optimal states are used to further adjust he design parameters in order to provide a design that is suitable of a particular condition or set )f conditions. The results using various non-optimal states may be used to provide a lens suited For a plurality of anticipated non-optimal states of an IOL within an eye or certain population of syes having certain aberrations. For instance, the method may be used for testing the lens over a )lurality of corneal surface variations and dispositions of optical elements in the eye's optical 17 C NRPWI CCKMHI29)7547.1 DOC-27A4/2010 - 18 system using tolerance analyzing techniques. Additionally, all or part of the method may be repeated one or more times to modify zonal parameters and achieve a better average optical performance. Known algorithms, such as assigning weighting functions to the various non- optimal states, may be used to provide a lens with desired characteristics. 5 [0066] While embodiments of the invention have been disclosed for an IOL suitable providing enhanced performance under non-optimal conditions, such as when the IOL is decentered from the optical axis of the eye, those skilled in the art will appreciate that embodiments of the invention are suitable for other ocular devices such as contact lenses 10 and corneal implants. For instance, the method of designing a multi-zonal monofocal IOL may be adapted for improving the performance of contact lenses, which are known to move to different positions during use relative to the optical axis of the eye. [0067] While this invention has been described with respect to various specific examples 15 and embodiments, it is to be understood that these are merely exemplary and that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims. [0068] The reference in this specification to any prior publication (or information derived 20 from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. 25 [0069] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (19)

1. A multi-zonal monofocal ophthalmic lens including: an optic disposed about an optical axis including a first lens surface and a second 5 lens surface disposed opposite the first lens surface; the first lens surface including a plurality of zones, including: a first zone having a finite radial width and a sag surface characterized by a first base radius of curvature value and a first asphericity constant; and a second zone surrounding the first zone and having a finite radial width 10 and a sag surface characterized by a second base radius of curvature value and a second asphericity constant; the radius of curvature values are unequal, the asphericity constants are unequal, or the radius of curvature values are unequal and the asphericity constants are unequal; the zones configured to focus light entering the entire optic from a distant point 15 source to substantially a single point, the lens having a maximum Diopter power difference between any two zones of the lens that is less than 0.75 Diopters.

2. The multi-zonal monofocal ophthalmic lens of claim 1, further including a third zone surrounding the second zone and having sag surface characterized by a third base 20 radius of curvature and a third asphericity constant.

3. The multi-zonal monofocal ophthalmic lens of claim 2, wherein: the first zone has a first optical power, the second zone has a second optical power, and the third zone has a third optical power; 25 the second optical power differs from both the first and third optical powers by a magnitude that is less than or equal to about 0.65 Diopter.

4. The multi-zonal monofocal ophthalmic lens of claim 1, further including a diffractive grating disposed on the first surface. 30

5. The multi-zonal monofocal ophthalmic lens of claim 1, further including a C:\NRPorbl\DCC\KMH\915683_1.DOC-5/10/2011 - 20 diffractive grating disposed on the second surface.

6. The multi-zonal monofocal ophthalmic lens of claim 1, wherein the first base radius of curvature is equal to the second base radius of curvature. 5

7. The multi-zonal monofocal ophthalmic lens of claim 1, wherein the zones are adapted to focus incoming light rays to form an image from an object and the second zone is adapted to compensate for optical aberrations in the image resulting from implanted intraocular lens decentration of greater than at least about 0.1 mm. 10

8. The multi-zonal monofocal ophthalmic lens of claim 1, wherein the zones are adapted to focus incoming light rays to form an image from an object and the second zone is adapted to compensates for optical aberrations in the image resulting from implanted intraocular lens tilt of greater than at least about 1 degree. 15

9. The multi-zonal monofocal ophthalmic lens of claim 1, wherein the first lens surface is further characterized by at least one boundary parameter that is selected to smoothly connect the first zone with the second zone. 20

10. The multi-zonal monofocal ophthalmic lens of claim 1, wherein the zones are configured to reduce spherical aberrations.

11. The multi-zonal monofocal ophthalmic lens of claim 1, wherein the ophthalmic lens has a nominal optical power that is positive and the second zone has a negative 25 spherical aberration that is selected to reduce spherical aberrations.

12. The multi-zonal monofocal ophthalmic lens of claim 1, wherein the second base radius of curvature is greater than first base radius of curvature. 30

13. The multi-zonal monofocal ophthalmic lens of claim 1, wherein an average MTF efficiency of the lens is higher than an average MTF efficiency of a spherical lens. C -NRPortbl\DCC\XMH\39156 _I .DOC-5/10/2011 -21

14. The multi-zonal monofocal ophthalmic lens of claim 1, wherein an MTF efficiency at a spatial frequency of 50 cycles/mm of the lens is higher than an MTF efficiency at a spatial frequency of 50 cycles/mm of a spherical lens. 5

15. The multi-zonal monofocal ophthalmic lens of claim 1, wherein the first zone and the second zone are disposed adjacent to one another.

16. The multi-zonal monofocal ophthalmic lens of claim 1, further including a smooth 10 transition between the first zone and the second zone.

17. The multi-zonal monofocal ophthalmic lens of claim 1, wherein the zones are configured such that light entering the entire optic from a distant point source falls within the range of the depth-of-focus of a spherical lens having a focal length equivalent to a 15 focal length of the multi-zonal monofocal ophthalmic lens.

18. A multi-zonal monofocal ophthalmic lens including: an optic disposed about an optical axis including a first lens surface and a second lens surface disposed opposite the first lens surface; 20 the first lens surface including a plurality of zones, including: a first zone having a finite radial width and a sag surface characterized by a first base radius of curvature value and a first asphericity constant; and a second zone surrounding the first zone and having a finite radial width and a sag surface characterized by a second base radius of curvature value and a 25 second asphericity constant; the radius of curvature values are unequal, the asphericity constants are unequal, or the radius of curvature values are unequal and the asphericity constants are unequal; the lens having a maximum Diopter power difference between any two zones of the lens being less than 0.75 Diopters. 30

19. A method of designing a multi-zonal monofocal ophthalmic lens, substantially as C XNRPontbI'fCC\KMiN~95683-1 DOC.5tlfl0 - 22 herein described.