Title of Invention

OPTIMAL IOL SHAPE FACTORS FOR HUMAN EYES

Abstract

The present invention provides an ophthalmic lens (e.g., an intraocular lens) having an optic with an anterior surface and a posterior surface, which exhibits a shape factor (defined as a ratio of the sum of the anterior and posterior curvatures to the difference of such curvatures) in a range of about -0.5 to about 4. In a related aspect, the shape factor of the optic lies in a range of about 0 to about 2. The above shape factors give rise to a plurality of different lens shapes, such as concave-convex, plano-convex and plano-concave.

Full Text

OPTIMAL IOL SHAPE FACTORS FOR HUMAN EYES Related Application The present application claims priority to U.S. Provisional Patent Application Serial No. 60/668,520 entitled "Intraocular Lens," filed on April 5, 2005, which is herein incorporated by reference. A U.S. patent application entitled, 'Intraocular Lens," assigned to the assignee of the present application, and filed concurrently herewith, is herein also incorporated hy reference. Background The present invention relates generally to ophthalmic lenses, and more particularly, to intraocular lenses (lOLs) having optimal shape factors. Intraocular lenses are routinely implanted in patients' eyes during cataract surgery to replace the clouded natural lens, The post-operative performance of siwh I OLs, however, can be degraded due to a variety of factors. For example, aberrations introduced as aresult of misalignment of the implanted IOL relative to the cornea, and/or the inherent aberrations of the eye, can adversely affect the lens's optical performance. Accordingly, there is a need for improved lOLs that can provide E more robust optical performance, fenmmarv In one aspect, the present invention provides an ophthalmic lens (e,g., an intraocular lens) having an optic with an anterior surface and a posterior surface. The optic exhibits a shape factor in a range of about -0,5 to about 4. In a related aspect, the shape factor of the optic lies in a range of about 0 to about 2. The above shape factors give rise to a plurality of different lens shapes, such as, bi-convex, plano-convex, planoconcave and convex-concave. In another aspect, the optic is formed of a biocompatible polymeric material. By way of example, the optic can be formed of a soft acrylic polymeric material Other examples of suitable materials include, without limitation, hydrogel and silicone materials. In another aspect, at least one surface of the optic can be characterized by an aspheric base profile (i.e., a base profile that exhibits deviations from sphericity). By way of example, the base profile can be characterized by a conic constant in a range of about -73 to about -27. In E related aspect, the aspheric profile of the lens surface can be defined in accordance with the following relation: wherein, c denotes the curvature of the surface at its apex (at its intersection with the optical axis), r denotes the radial distance from the optical axis, and k denotes the conic constant, wherein c can be, e.g.: in a range of about 0.0152 mm"1 to about 0.0659 mrn"r can be, e.g., in a range of about 0 to about S, .and fccanbe, e.g., in a range of about-1162 to about-19 (e,g., in a range of about- 73 to about -27). In a related aspect, the optic of the above lens can have a shape factor in a range of about Oto about 2. In some embodiments in which one or more surEaces of the ophthalmic lens exhibit asphsricity. the shape factor of the lens (e.g., an IOL) can be selected as a function of that asphericity so as to optimize the lens's optical performance. By way of example, in one aspect, the invention .provides an ophthalmic lens having an optic with an anterior surface and a posterior surface, where at least one of the surfaces exhibits an ashpsrica] profile characterized by a conic constant in a range of about -73 to about -27. The optic exhibits a shape factor in a range of about -0.5 to about 4. In a related aspect, an ophthalmic leas having an optic with a shape factor in a range of about 0 to about 2 includes at least one aspherical surface characterized "by a conic constant in a range of about -73 to about -27, In other aspects, an intraocular lens adapted for implantation in an eye having a comeal radius equal to or less than about 7.1 mm is disclosed, which includes an optic having an anterior surface and a posterior surface, The optic exhibits a shape factor in a range of about -0.5 to about 4. In a related aspect, the optic exhibits a shape factor in a range of about +0.5 to about 4, or in a range of about 1 to about 3. In another aspect, the invention provides an intraocular lens adapted for implantation in an eye having a comeal radius in a range of about 7.1 mm to about B.6 mm, which includes an optic having an anterior surface and a posterior surface. The optic exhibits a shape factor in a range of about 0 to about 3. In a related aspect, the optic exhibits a shape factor in a range of about +-0.5 to about 3, or in a range of about 1 to about 2. In another aspect, an intraocular lens adapted for implantation in an eye having a comeal radius equal to or greaterthan about 8.6 is disclosed, which includes an optic having an anterior surface and a posterior surface. The optic exhibits a shape factor in a range of about 0.5 to about 2, In a related aspect, fee optic exhibits a shape factor in a range of about 1 to about 2. In another aspect, the invention provides an intraocular lens adapted for implantation in an eye having an axial length equal to or less than about 22 mm, which includes an optic having an anterior surface and a posterior surface. The optic can have a shape factor in a range of about 0 to about 2, or in a range of about 0.5 to about 2. In other aspects, the invention discloses methods for selecting an ophthalmic lens for implantation in a patient's eye based on one or more ocular biometric parameters of the patient. For example, a method of correcting vision is disclosed that includes selecting an 10L, which comprises an optic exhibiting a shape factor in a range of about - 0.5 to about 4 (or in a range of about 40,5 to about 4), for implantation in an eye having a comaal radius that is equal to or less than about 7.1 mm In another aspect, a method of correcting vision is disclosed that includes selecting an IOL, which comprises an optic exhibiting a shape factor in a range of about 0 to about 3 (or in a range of about 0,5 to about 3), for implantation in an eye having a comeal radius in a range of about 7.1 mm to about 8.6 mm In yet another aspect, a method of correcting vision is disclosed that includes selecting an IOL, which comprises an optic exhibiting a shape factor in a range of about 0.5 to about 1, for implantation in an eye having a comeal radius that is equal to or greater than about 8.6 mm, In another aspect, a method of corrected vision is disclosed that includes selecting an IOL, which .comprises an optic exhibiting a shape factor in a range of about 0 to about 2 (or in a range of about 0.5 to about 2), for implantation in an eye having an axial length equal to or less than about 22 mm. In another aspect, a method of designing an ophthalmic lens is disclosed that includes defining an error function, which is indicative of variability in performance of .a lens in a patient population, based on estimated variability in one or more Diametric parameters associated with that population, and selecting a shape factor for the lens that reduces the error function relative to a reference value. In a related aspect, the error function can further include an estimated error in optical power correction provided by the lens and/or an estimated aberration error. In a related aspect, the error function (RtError) can be defined in accordance with the following relation: RxError - \j hBiametric1 + klOLPawer2 4- ^Aberration2 wherein, kBiametric denotes variability due to biometric data errors, •bJOLPawer denotes variability due to optical power correction errors, and Aberration denotes variability due to aberration contributions. In another aspect, the kBtametric can be defined in accordance with the following relation: ABio/netric =wherein, At denotes error in keratometric measurements, AAL denotes error in axial length measurements, and AACD denotes error in anterior chamber depth measurements, In another aspect, the ^Aberration can be defined in accordance with the following relation: Mberration - Mstig+ A&42 + AOtherwherein, AAstig represents variability due to astigmatic aberration, ASA represents variability due to spherical aberration, and LOther represents variability due to other aberrations. In a further aspect, the A/QLPwer can be defined in accordance with me following relation: tJOLPower = MOLStep1 + MOLTo? + A£LP! wherein, AIOLStep represents variability caused "by difference between a power correction provided by the lens and B power correction needed by a patient., LlOLTol represents manufacturing power tolerance, and AELP represents variability in a shift of the lens effective position within the eye. Further understanding of the invention can be obtained by reference to the following detailed description, in conjunction with the associated drawings, which are discussed briefly below. Brief Description of the Drawings FIGURE 1 is a schematic side view of an IOL in accordance with one embodiment of the invention, FIGURE 2 presents simulated magnitude of different aberration types (spherical defocus, coma and astigmatic aberrations) exhibited by an IOL as a function of its shape factor for a 1.5 mm decentration, FIGURE 3 presents simulation results for aberrations exhibited by an IOL due to tilt as a function of the IOL's shape factor, FIGURE 4A presents graphically calculated spherical aberration exhibited by a model eye characterized by an average anterior chamber depth hi which an IOL is incorporated, as a function of the IOL' s shape factor, FIGURE 4B presents graphically calculated MTFs at 50 Ip/rnm and 100 Ip/mm for a model eye characterized by an average anterior chamber depth in which an IOL is incorporated BE a function of the lOL's shape factor, FIGURE 5A depicts simulated MTFs at 50 Ip/mm and 100 Ip/mm for a model eye characterized by a small anterior chamber depth in which an IOL is incorporated, as a function of the IOL's shape fector, FIGURE 5B depicts simulated spherical aberration exhibited by a model eye characterized by a small anterior chamber depth in which an IOL is incorporated, as a function of the IOL's shape factor, FIGURE 6A depicts simulated spherical aberration exhibited by a model eye characterized by a large anterior chamber depth in which an IOL is incorporated, as a function of the lOL's shape factor, FIGURE 6B depicts simulated MTFs at 50 Ip/mm and 100 Ip/mm for a mode! eye characterized by a large anterior chamber depth in which an IOL is incorporated, as a function of the lOL's shape factor, FIGURE 7A depicts graphically simulated spherical aberrations exhibited by a plurality of model eyes having different cornea! asphericities in which an IOL is incorporated, as a function of the lOL's shape factor, FIGURE 7B depicts graphically simulated MTF as 50 Ip/mm obtained for model eyes having different cornea! asphericities in which an IOL is incorporated, as a function of the lOL's shape factor, FIGURE 7C depicts graphically simulated MTF at 100 Ip/mm obtained for model eyes having different cornea! asphericities in which an IOL is incorporated, as a function of thelOL's shape factor, FIGURE 8A depicts simulated spherical .aberration exhibited by two model eyes characterized by different cornea! radii as a function of the shape factor of an IOL incorporated in the models, FIGURE 8B depicts simulated MTF at 50 Ip/mm exhibited by two model eyes characterized by different comeal radii as a function of the shape iactor of an IOL incorporated in the models, FIGURE 8C depicts simulated MTF at 100 Ip/mm exhibited by two model eyes characterized by different comeal radii as a function of the shape factor of an IOL incorporated in the models, FIGURE 9A depicts simulated spherical aberration exhibited by a plurality of model eyes having different axial lengths'as a function of the shape factor of an IOL incorp orated in the models, FIGURE 9B depicts simulated MTFs at 50 Ip/mm exhibited by a plurality of model eyes having different axial lengths as a function of the shape factor of an IOL incorporatad in the models, FIGURE 9C depicts simulated MTFs at 100 Ip/mm exhibited by a plurality of model eyes having different axial lengths as a function of the shape factor of an IOL incorporated in the models, FIGURE 10 is a schematic side view of a lens according to one embodiment of the invention having an asphsric anterior surface, FIGURE 11 presents a plurality of graphs depicting the sag of an aspheric surface of two lenses in accordance with the teachings of the invention having different shape factors, and FIGURE 12 graphically presents Monte Carlo simulation results for optical performance of a plurality oflOLs as a function of manufacturing tolerances, Detailed Description of fee Preferred Embodiments FIGURE 1 schematically depicts an IOL 10 in accordance with one embodiment of the invention having an optic 12 that includes an anterior surface 14 and a posterior surface 16. hi this embodiment, the anterior and posterior surfaces 14 and 16 are symmetrically disposed about an optical axis IB, though in other embodiments one or both of those surfaces can exhibit a degree of asymmetry relative to the optical axis. The exemplary IOL 10 further includes radially extending fixation members or implies 20 that facilitate its placement in the eye. In this embodiment, the optic is formed of a soft acrylic polymer, commonly known as Acrysof, though in other embodiments, it can be formed of other biocompatible materials, such as silicons or hydrogel, The lens 10 provides a refractive optical power in a range of about 6 to about 34 Diopters (D), and preferably in a range of about 16 D to about 25 D. In this exemplary embodiment, the lens 10 has a shape factor in a range of about 0 to about 2, More generally, in many embodiments, the shape factor of the lens 10 can range from about -0.5 to about A. As known in the art, the shape factor of the lens 10 can be defined in accordance with the following relation: Shape Factor (X) = L- Eq. (1) wherein Cj and Cj denote, respectively, "the curvatures of the anterior and posterior surfaces, The, shape factor of the IOL 10 can affect the aberrations (e.g., spherical and/or astigmatic aberrations) that the lens can introduce as a result of its tilt and decentration, e,g,, when implanted in the subject's eye or in a modal eye. As discussed in more detail below, aberrations caused by a plurality of lOLs with different shape factors were theoretically studied as a function of tilt and decentration by utilizing & model eye. Those studies indicate that lOLs having a shape factor in a range of about 0 to about 2 introduce much reduced aberrations as a result of tilt and decentration. More particularly, to study the effects of an IOL's shape factor on aberrations induced by its tilt and decentration, a hypothetical eye model having optical properties (e.g.. cornea! shape) similar to those of an average human eye was employed. The radii of optical surfaces and the separations between optical components were chosen to correspond to mean values of those parameters for the human population. The refractive indices of the optical components were chosen to provide selected retractive power and chromatic aberrations, Further, the anterior comeal surface of the model was selected to have an ashperical shape. An IOL under study replaced the natural lens in the model, An optical design software marketed as Zomax® (version March 4, 2003, Zemax Development Corporation, San Diego, CA) was utilized for the simulations of the optical properties of the model eye. A merit function was defined based on "the rootmean- square (RMS) wavefront aberration, that is, the RMS wavefront deviation of an optical system from a plane wsve, In general, the larger the RMS wavefroat error, the poorer is the performance of the optical system. An optical system with an RMS wavefront error that is less than about 0.071 waves is typically considered as exhibiting a diffraction-limited optical performance. The effects of misalignment (tilt and/or decentration) of an IOL on its optical performance for a number of different shape factors was simulated by placing the lOLs in the above model eye and utilizing the Zemax* software. For these simulations, the IOL was assumed to have spherical surfaces so as to investigate the effects of the shape factor alone (as opposed to that of the combined shape factor and asphericity), To simulate the scotopic viewing conditions for old patients, a 5 mm entrance pupil was chosen. The following misalignment conditions were considered: 1.5 mm IOL decentration and a 10-degree IOL tilt. These two conditions represent the extreme cases of IOL misalignments. FIGURE 2 presents the simulated magnitude of different aberration types (spherical aberration, defocus, coma and astigmatism) as a function of the shape factor for 1.5 mm decenlration of the IOL. These simulations indicate that lOLs with a shape factor in a range of about 0 to about 2 exhibit much lower aberrations as a result of the deceleration For example, an IOL with a shape factor of about 1 introduces a defbcus aberration of 0,07 D compared to a defocus aberration of 0.32 D introduced by an IOL having a shape factor of -1. FIGURE 3 presents the simulation results for aberrations introduced as a result of the lOL's tilt. These results indicate that the defocus and astigmatic aberrations are not significantly influenced by the lOL's shape factor while the coma and spherical aberrations exhibit even stronger dependence on the shape factor than their dependence in case of the lOL's decentration, Again, the lOLs with shape factors in a range of ahout 0 to 2 exhibit a stable performance. In other aspects, it has been discovered that certain bio-metric parameters of the eye (e.g., cornea! radius and axial length) can be considered while selecting the shape factor of an IOL for implantation in the eye to provide enhanced performance of the lens, As discussed in more detail below, in some embodiments, optimal IOL shape factors are provided for different eye populations, e.g., average human eye (eyes with average values for certain biometric parameters), and other populations characterized by extreme values for those parameters. The biometric parameters of the above eye model were varied to simulate the performance of a plurality of IOLs having different shape factors for different eyes. For an average human eye, a comeal radius (r) of 7,72 mm, a corneal asphericity (Q) of- 0.26: an anterior chamber depth (ACD) of 4.9 mm, and an axial length (AL) of 24,4 mm were assumed, To investigate human eyes with extreme large or small biometric values, the anterior chamber depth was varied from 4.3 mm to 5.5 mm, the comeal asphericity was varied from -0.50 to 0, the corneal radius was varied from 7.10 mm to 8,60 mm, and me axial length was varied from 22.0 mm to 26.0 mm. These ranges are sufficiently broad to cover the values exhibited by the majority of the population, The optical performance of the IOLs was evaluated based on two criteria: calculated wave aberration and modulation transfer function (MTF). As known to those having ordinary skill in the art, the MTF provides a quantitative measure of image contrast exhibited by an optical system, e.g., a system formed of an IOL and the cornea. More specifically, the MTF of an imaging system can be defined as a ratio of a contrast associated with an image of an object formed by the optical system relative to a contrast associated with the object. Table 2 below presents the simulation results of the optical performance of lOLs having shape factors in a range of about -2 to about 4 for an eye having an average anterior chamber depth (ACD) of 4.9 mm, B comeal radius of 1.72 mm, a cornea! asphericity of-0.26, and an axial length (AL) of 24.4 mm, at a pupil size of 5 mm The above simulations indicate that while for a long axial length (e.g., an axial length of about 26 mm), lOLs having shape fiactors over a wide range (e.g., in a range of about -1 to about 8) provide substantially similar performance, for a short axial length (e.g., an axial length of about 22 mm), an optimal IOL shape factor lies in a range of about 0 to about 2 (preferably in a range of about 0.5 to about 2), Further, the peak of optical performance exhibits a shift as a function of axial length variation. In some embodiments, an anterior or a posterior surface of the IOL includes an aspherical base profile selected to compensate for fhe comeal spherical aberration, Alternatively, both anterior and posterior surfaces can be aspherical so as to collectively provide a selected degree of compensation for the comeal spherical aberration, By way (Table Removed) of example, FIGURE 10 shows an IOL 22 according to one embodiment of the invention that includes an optic having a spherical posterior surface 24 and an aspherical .anterior surface 26. More specifically, .the anterior surface 26 is characterized by a base profile that is substantially coincident -with a putative spherical profile 26a (shown by dashed lines) for small radial distances from an optical axis 28 but deviates from that spherical profile as the radial distance from the optical axis increases. In this embodiment, the aspherical anterior surface can be characterized by the following relation: In some embodiments, the conic constant k can range from about -1 162 to about (e.g., from about -73 to about -27) and the shape factor of the lens can range from about -0.5 to about A, and more preferably, from about 0 to about 2, To showthe efficacy of such aspherical IOLs in. reducing the cornea! spherical aberrations, two aspherical IOLs were theoretically designed. The IOLs were assumed to be formed of an acrylic polymer commonly known as Acrysof, One of the IOLs was selected to have a shape factor of zero (X = D) while the other was chosen to have a shape factor of 1 (X = 1), The edge thickness for each IOL was fixed at 0.21 mm. For the IOL with X = 0, the anterior and posterior radii were set, respectively, at 22.934 mm and -22.934 mm, the central thickness was set at 0.577 mm and the anterior surface asphericity (i.e., the conic constant) was selected to be -43,656. For the IOL withX = 1, the posterior surface was selected to be flat while the radius of the anterior surface was set at 11.785 mm. The central thickness of this lens was 0.577 mm and the anterior surface was assumed to have an asphericity characterized by a conic constant of -3.594. FIGURE 11 shows the sag of the anterior surfaces of these exemplary IOLs as a function of radial distance from the optical axis The simulations of the optical performances of these two IOL designs in the aforementioned eye model show a reduction of the tota] RMS wavefront errors to about 0.000841 waves in case of the IOL having a shape factor that approaches zero and to about 0.000046 in case of the IOL having a shape factor of unity. Another factor that cm affect the optical performance of an IOL IE its effective position. The effective lens position (e.g., defined here as the location of the principal plane relative to the posterior surface) can vary as a function of the lens's shape, The location of the second principal plane (PPa) relative to the apex of the posterior surface can be defined by the following relation: Eq,(3) wherein »/ and HI denote, respectively, the refractive indices of the IOL and the surrounding medium, Fi represents the optical power of the anterior surface and F3 represents the optical power of the lens, and d is the lens's central thickness. The haptics plane (the anchor plane for the implanted IOL) located at the central-Jine of the lens edge can have a distance from the apex of the posterior surface specified as: ~ Bq.(4) wherein ET denotes the lens's edge thickness and Sag.2 denotes the sag height of the posterior surface at the lens's edge, Utilizing the above Equations (3) and (4), the location of the second principal point relative to the haptics plane can be defined as follows: Eq.(5) wherein APPs denotes an offset shift of the principal plane, and the other parameters are defined above. By way of example, the 2d principal plane shift for the aforementioned IOL having a shape factor of zero (X «= 0) was calculated (by utilizing the above equations) across a power range of 0 to about 35 D as /- 0.03 mm, while the corresponding shift for the IOL having a shape factor of unity (X «= 1) was calculated as +/- 0.15 mm To better appreciate the enhanced optical performance provided by the lOLs of the invention, some of the major factors contributing to the variability of post-operative refractive errors can be considered. These fectors are generally classified into three categories: biometric data errors (ABiomezric), IOL power errors (ATOLPower) and high-order aberration contributions (Mberration}. An overall variability (Rx) can be calculated based on these factors by utiliang, e.g., the following relation; RxError = VABiomeMc2 + ATQLPower2 -f Mberration3 Eq, (6) The ABiometrtc can, in turn, be defined in accordance with the following relation; hBiometric = VAF+A4I2 + MCD2 Eq. (7) wherein AJk denotes the error in karatometric measurement, A/4L denotes the error in axial length measurement, and M.CD denotes the error in the anterior chamber depth maasurement. The AZOLPovcer can be defined in accordance with the following relation; MOLPower - ^LIOLStep1 + hlOLTo? -f AELP2 Eq. (8) wherein MOLStep denotes the variability caused by the use of lOLs whose optical powers differ by finite steps for correcting patients' refractive errors that vary over a continuous range, AJOLTol denotes manufacturing power tolerance, and AfiLP denotes the variability in the shift of the IOL effective position across the power range. Further, (Aberration can be denned in accordance with the following relation; wherein AAslig, ASA, hOther denote, respectively, astigmatic, spherical and other higher order aberrations. The optical performance of the aforementioned exemplary IOL designs having shape factors (X) of zero and unity were evaluated based on estimated Rx variability for three conditions; (1) uncorrected visual acuity (i.e., in the absence of corrective spectacles) with IOL power step of 0.5 D (UCVA), (2) uncorrected visual acuity with a refined IOL power step of 0.25 D (UCVA+) and (3) best corrected visual acuity.(i.e., utilizing optimal corrective spectacles) (BCV A). The variability due to biometric measurements was estimated from information available in the literature, The focus of the analysis relates to estimating contributions of the spherical aberration, errors due to IOL rmsalignmsnts, and fee 2ni! principal plane (PPL) shifts. For comparison purposes, a baseline value of 0.65 D was assumed for UCVA and UCVA+ and a baseline value of 0.33 D was assumed for BCV A, for eyes with spherical lOLs, Table £ below lists absolute and percentage reductions in Rx relative to the baseline values for the two ation presented in Table 8 shows that reductions inRx variability are achieved for both lOLs (X = 0, and X =1), thus indicating improved optical performance of those lenses. For the IOL with a vanishing shape factor (X = 0), the visual benefits are almost evenly distributed among UCVA, UCVA+ and BCVA while for the other IOL (X=l), the visual benefit associated with BCV A is more pronounced. A variety of known manufacturing techniques can be employed to fabricate the lenses of the invention. The manufacturing tolerances can also affect the optical performance of an IOL. By way of example, such tolerances can correspond to variations of, e.g., surface radii, conic constant, surface decentration, surface tilt, and surface irregularity, with tolerances associated with surface asphericity (conic constant) general!}' playing a more important role that others in affecting optical performance, Simulations, however, indicate that the lOL's misalignments upon implantation in the eye are typically more significant factors in degrading optical performance than manufacturing tolerances (e.g., manufacturing errors can be nearly 10 times less than misalignment errors), By way of further illustration, the optical performance of the aforementioned aspherical lenses withX = 0 and X =1, implanted in the aforementioned eye model, was theoretically investigated by employing Monte Carlo simulations. More specifically, 500 hypothetical lenses were generated under constraints of typical manufacturing tolerances and were randomly oriented relative to the cornea For example, the tolerances associated with the surface radii, surface irregularities, and surface decentration and tilt were assumed to he, respectively, within +/- 0.1 mm, 2 fringes, 0,05 mm and 0.5 degrees. The results of the Monte Carlo simulations are summarized in FIGURE 12. Morethan 50% of the simulated eyes exhibit an RMS wavefront errorthat is less than about 0.2 waves (about 0.08 D equivalent defocus), For the lens having X = 1, about 98% of the simulated eyes show a wavefront error less than about 0.3 waves (about 0.12 D), Those having 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. WE CLAIM: 1. An ophthalmic lens (10, 22) comprising an optic (12) having an anterior surface (14, 26) and a posterior surface (16, 24), said optic exhibiting a shape factor, defined as a ratio of the sum of the anterior and posterior curvatures to the difference of such curvatures, and said optic being formed from a polymeric biocompatible material, characterized in that; at least one of the anterior surface and the posterior surface has an aspherical base profile (26), wherein said aspherical base profile is characterized by a conic constant (Q) in a range of -73 to -27, and wherein the shape factor is in a range of - 0.5 to 4. 2. The ophthalmic lens as claimed in claim 1, wherein said optic (12) exhibits a shape factor in a range of 0 to 2. 3. The ophthalmic lens as claimed in claim 1, wherein both of said surfaces (14, 16; 24, 26) have a generally convex profile. 4. The ophthalmic lens as claimed in claim 1, wherein one of said surfaces (14, 16; 24, 26) has a generally convex profile and the other surface has a substantially flat profile. 5. The ophthalmic lens as claimed in claim 1, wherein one of said surfaces (14, 16; 24, 26) has a generally concave profile and the other surface has a substantially flat profile. 6. The ophthalmic lens as claimed in claim 1, wherein one of said surfaces (14, 16; 24, 26) has a generally concave profile and the other surface has generally convex profile. 7. The ophthalmic lens as claimed in claim 1, wherein said aspherical base profile (26) is defined by the following relation: (Figure Removed) wherein, c denotes the curvature of the surface at its apex (at its intersection with the optical axis (18, 28) of the lens), r denotes the radial distance from the optical axis, and k denotes the conic constant, wherein c is in the range of 0.0152 mm-1 to 0.0659 mm-1, r is in a range of 0 to 5 mm,and k is in a range of - 73 to - 27. 8. The ophthalmic lens as claimed in claim 1, wherein said surfaces (24, 26) cooperatively provide a refractive optical power in a range of 16D to 25D. 9. The ophthalmic lens as claimed in claim 1, wherein said polymeric material is selected from the group consisting of acrylic, silicone and hydrogel materials. 10. The ophthalmic lens as claimed in any of claims 1 to 9, wherein said lens (10, 22) comprises an intraocular lens. 11. The intraocular lens as claimed in claim 10, having haptics (20) sized to fit within an eye having a corneal radius equal to or less than about 7.1 mm, and said optic exhibiting a shape factor in a range of - 0.5 to 4, preferably in a range of + 0.5 to 4, most preferably in a range of 1 to 3, or having haptics (20) sized to fit within an eye having a corneal radius in a range of 7.1 mm to 8.6 mm, and said optic exhibiting a shape factor in a range of 0 to 3, preferably in a range of + 0.5 to 3, most preferably in a range of 1 to 2, or having haptics (20) sized to fit within an eye having a corneal radius equal to or greater than about 8.6 mm, and said optic exhibiting a shape factor in a range of + 0.5 to 2, preferably in a range of 1 to 2. 12. The intraocular lens as claimed in claim 10, having an axial length equal to or less than about 22 mm, and said optic (12) exhibiting a shape factor in a range of 0 to 2, preferably in a range of 0.5 to 2.

Documents:

1361-delnp-2007-abstract.pdf

1361-delnp-2007-assignment.pdf

1361-delnp-2007-Claims-(23-05-2012).pdf

1361-delnp-2007-claims.pdf

1361-DELNP-2007-Correspondence Others-(12-12-2011)..pdf

1361-DELNP-2007-Correspondence Others-(12-12-2011).pdf

1361-delnp-2007-Correspondence Others-(23-05-2012).pdf

1361-delnp-2007-correspondence-others 1.pdf

1361-delnp-2007-Correspondence-Others-(07-04-2011).pdf

1361-DELNP-2007-Correspondence-Others.pdf

1361-delnp-2007-description (complete).pdf

1361-delnp-2007-drawings.pdf

1361-delnp-2007-form-1.pdf

1361-delnp-2007-form-18.pdf

1361-delnp-2007-form-2.pdf

1361-DELNP-2007-Form-3-(12-12-2011).pdf

1361-DELNP-2007-Form-3.pdf

1361-delnp-2007-form-5.pdf

1361-delnp-2007-gpa.pdf