Patent Application
20070282438
The present invention relates generally to multi-element and/or multi-surface ophthalmic lenses in which different elements and/or surfaces provide independent correction of a plurality of monochromatic, polychromatic and oblique aberrations. In the embodiments that follow, the salient features of various aspects of the invention are discussed in connection with intraocular lenses (IOLs). However, the teachings of the invention can also be applied to other ophthalmic lenses, such as contact lenses. Further the term “intraocular lens” and its abbreviation “IOL” are used herein interchangeably to describe lenses that are implanted into the interior of the eye to either replace the eye's natural lens or to otherwise augment vision regardless of whether or not the natural lens is removed. Intracorneal lenses and phakic lenses are examples of lenses that may be implanted into the eye without removal of the natural lens.
With reference to
In some embodiments, one or more surfaces of at least one optic, and/or the optic itself, can be asymmetric relative to the respective optical axis, e.g., to reduce off-axis aberrations as discussed further below. Although in this embodiment the optics 12 and 14 are axially separated from one another, in other embodiments, the optics can be in contact via two surfaces thereof. More generally, in many embodiments, the separation between the optics can range from zero to about 5 mm. The IOL 10 further includes fixation members or haptics 16 that facilitate its placement in a patient's eye.
In many embodiments, the anterior and posterior optics collectively provide an optical power in a range of about 6 Diopters (D) to about 34 D. Further, the optics are preferably formed of biocompatible materials, such as soft acrylic, silicone, hydrogel or other biocompatible polymeric materials having a requisite index of refraction for a particular application. By way of further examples, U.S. Pat. No. 6,416,550, which is herein incorporated by reference, discloses materials suitable for forming the IOL 10. The haptics 16 can also be formed of suitable polymeric materials, such as polymethylmethacrylate, polypropylene and the like.
While in some embodiments, both optics are formed of the same material, in other embodiments, they can be formed of different materials. By way of example, in this exemplary embodiment, the posterior optic can be formed of a soft acrylic material known as Acrysof® (a cross-linked copolymer of 2-phenylethyl acrylate and 2-phenylethyl methacrylate) having an index of refraction of about 1.55, while the anterior optic is formed of another material having a lower index of refraction (e.g., 1.42) so as to reduce surface reflections and glare.
With continued reference to
One or more optical surfaces of the optics 12 and 14 are configured so as to reduce, and in some cases eliminate, a number of radially symmetric and radially asymmetric aberrations. By way of example, as shown schematically in
In some embodiments, the aspherical profile of the anterior surface can be defined in accordance with the following relation:
wherein,
z denotes a sag of the surface at a radial distance r from an optical axis of the optic 12, c denotes curvature of the surface at its apex (at the intersection of the optical axis with the surface); c=1/R where R denotes the radius of the surface at its apex,
k denotes a conic constant,
a1 denotes a second order aspheric coefficient,
a2 denotes a fourth order aspheric coefficient, and
a3 denotes a sixth order aspheric coefficient.
In some embodiments, the aspheric profile of the anterior surface can be characterized by the above relation with c ranging from about 0.0152 mm−1 to about 0.0659 mm−1, k ranging from about −1162 to about −19, a1 ranging from about −0.00032 mm−1 to about −0.00020 mm−1, a2 ranging from about −0.0000003 (minus 3×10−7) mm−3 to about −0.000053 (minus 5.3×10−5) mm−3, and a3 ranging from about 0.0000082 (8.2×10−6) mm−5 to about 0.000153 (1.53×10−4) mm−5.
With continued reference to
More particularly, with reference to
z=c
coma
*f
coma(r,θ,α), Eq. (2)
wherein,
f
coma(r,θ,α)=2√{square root over (3)}(10r5−12r3+3r)cos(θ+α) Eq. (3)
wherein,
z indicates a sag of the surface along the optical axis,
ccoma is a coefficient indicating a correction magnitude (e.g., in a range of about −0.5 microns to about +0.5 microns),
r is a pupil location normalized relative to the pupil radius,
θ denotes a meridian angle, and
α represents the coma axis to be corrected.
Referring again to
By way of example, in some embodiments, the profile of a surface of the lens, which provides a correction for the trefoil aberration, can be defined in accordance with the following relation:
z=c
trefoil
*f
trefoil(r,θ,α) Eq. (4)
wherein,
f
trefoil(r,θ,α)=2√{square root over (3)}(5r5−4r3)cos(3(θ+α)) Eq. (5)
wherein,
ctrefoil is a coefficient indicating a correction magnitude (e.g., in a range of about −0.5 microns to about +0.5 microns),
r is a pupil location normalized relative to the pupil radius,
θ is a meridian angle, and
α is the trefoil axis to be corrected.
In some embodiments, the chromatic dispersions (variations of refractive index as a function of wavelength) of the materials forming the optics 12 and 14 of the IOL 10, together with the radii of curvature of their optical surfaces, are selected to reduce, or substantially eliminate, the longitudinal chromatic aberrations exhibited by the IOL 10, and/or to provide compensation for the natural chromatic aberrations of the eye. For example, one optic (e.g., 12) can be configured to have a positive optical power and be made of one type of material and the other optic (e.g., 14) can be configured to have a negative optical power and be made of a different material such that the IOL would provide chromatic aberrations correction. For example, in some embodiments, the IOL can provide a chromatic aberration correction in a range of about 1 to about 2 Diopters over a wavelength range of about 400 nm to about 700 nm. As is known in the art, a variation of the refractive index of a material as a function of radiation wavelength is referred to as the dispersion of that material. One commonly employed measure of a material's dispersion (variation of refractive index with wavelength) is known as Abbe number (also known as V-number or constringence of a material), and is defined as follows:
where nD, nF and nC represent the refractive indices of the material at wavelengths of 589.2 nm, 486.1 nm and 656.3 nm, respectively, that correspond to Fraunhofer D-, F-, and C-spectral lines. In general, materials having high values of V exhibit low dispersions. In some embodiments, the materials forming the optics 12 and 14 have sufficiently different V numbers so as to minimize, and in some cases eliminate the chromatic aberrations of the IOL.
By way of example, in one embodiment, the optic 12 can be made from polymethylmethacrylate (PMMA) (V=55) and the optic 14 can be made from polysulfone (V=30.87). Other suitable materials include, without limitation, soft acrylics (V of about 37), polystyrene (V=30.87), polycarbonate (V=29.9), or cellulose acetate hydrate (V in a range of about 80 to 84) so long as the differences between the Abbe numbers of the materials forming the two optics are sufficiently large (e.g., greater than about 10) to provide a desired chromatic compensation. A U.S. patent application entitled “Correction of Chromatic Aberrations in Intraocular Lenses,” filed concurrently herewith, and assigned to the assignee of the present application, provides further details regarding correcting chromatic aberrations in intraocular lenses, and is herein incorporated by reference in its entirety.
The teachings of the invention are not limited to multi-optic ophthalmic lenses. In other embodiments, one surface of a single-optic lens is employed to compensate for a radially symmetric aberration while the other surface of that optic is utilized to compensate for a radially asymmetric aberration. By way of example,
The use of different optics of a multi-optic IOL and/or different surfaces of a single-optic IOL for compensation of a plurality of aberrations advantageously allows independent adjustment of a number of distinct aberration modes. Further, it can facilitate customizing the IOLs to suit the visual needs of individual patients by streamlining the manufacturing processes. For example, for each optical surface of the IOL, a series of optic pins with different correction amounts associated with a given aberration mode can be set up. A permutation of such optic pins corresponding to different surfaces can be employed to provide IOLs exhibiting compensation for different aberrations and/or different amounts of aberration correction.
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.
