U.S. patent application number 12/634026 was filed with the patent office on 2010-06-24 for intraocular lens with extended depth of focus.
Invention is credited to Xin Hong.
Application Number | 20100161051 12/634026 |
Document ID | / |
Family ID | 42267230 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100161051 |
Kind Code |
A1 |
Hong; Xin |
June 24, 2010 |
Intraocular lens with extended depth of focus
Abstract
An ophthalmic lens is disclosed, one embodiment comprising an
optic having an anterior surface and a posterior surface disposed
about an optical axis, wherein at least one of the surfaces has a
profile characterized by superposition of a base profile and an
auxiliary profile, the auxiliary profile comprising a continuous
pattern of surface deviations from the base profile. The auxiliary
profile is a sinusoidal profile and can be amplitude modulated,
frequency modulated or both amplitude and frequency modulated. The
ophthalmic lens can be an IOL.
Inventors: |
Hong; Xin; (Fort Worth,
TX) |
Correspondence
Address: |
ALCON
IP LEGAL, TB4-8, 6201 SOUTH FREEWAY
FORT WORTH
TX
76134
US
|
Family ID: |
42267230 |
Appl. No.: |
12/634026 |
Filed: |
December 9, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61138816 |
Dec 18, 2008 |
|
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|
Current U.S.
Class: |
623/6.27 ;
351/159.01 |
Current CPC
Class: |
G02C 7/041 20130101;
G02C 7/04 20130101; A61F 2/1613 20130101; A61F 2/1637 20130101;
A61F 2/1624 20130101; A61F 2/164 20150401; A61F 2/16 20130101; G02C
2202/20 20130101; A61F 2/1616 20130101; A61F 2/1618 20130101 |
Class at
Publication: |
623/6.27 ;
351/159 |
International
Class: |
A61F 2/16 20060101
A61F002/16; G02C 7/02 20060101 G02C007/02 |
Claims
1. An ophthalmic lens, comprising an optic having an anterior
surface and a posterior surface disposed about an optical axis,
wherein: at least one of the surfaces has a profile characterized
by superposition of a base profile and an auxiliary profile, the
auxiliary profile comprising a continuous pattern of surface
deviations from the base profile.
2. The ophthalmic lens of claim 1, wherein the anterior surface and
the posterior surface are convex.
3. The ophthalmic lens of claim 1, where in the anterior surface
and the posterior surface are concave.
4. The ophthalmic lens of claim 1, wherein the base profile is
generally spherical.
5. The ophthalmic lens of claim 1, wherein the base profile is
symmetric about an optical axis of the ophthalmic lens.
6. The ophthalmic lens of claim 1, wherein the base profile is
generally aspherical.
7. The ophthalmic lens of claim 1, wherein the auxiliary profile is
symmetric about an optical axis of the ophthalmic lens.
8. The ophthalmic lens of claim 1, wherein the auxiliary profile is
a sinusoidal profile.
9. The ophthalmic lens of claim 8, wherein the profile of the
surface having said auxiliary profile is defined by the following
relation: y = a cos ( 2 .pi. r 2 b ) , ##EQU00005## wherein, a
denotes the amplitude of the sinusoidal curve and the diffraction
efficiency at different foci; and b denotes the periodicity and add
power.
10. The ophthalmic lens of claim 8, wherein the sinusoidal profile
is amplitude modulated with a cosine function operable to shift
light to a selected diffraction order, wherein the amplitude
modulated profile of the surface having said auxiliary profile is
defined by the following relation: y = a cos ( .pi. r 2 r 0 ) cos (
2 .pi. r 2 b ) ##EQU00006## wherein, a denotes the amplitude of the
sinusoidal curve and the diffraction efficiency at different foci;
b denotes the periodicity and add power; r denotes a radial
distance from an optical axis of the lens; and r.sub.0 is the
termination pupil radius of the cosine modulation.
11. The ophthalmic lens of claim 8, wherein the sinusoidal profile
is frequency modulated with a cosine function operable to vary the
effective add power of the optic as a function of pupil radius,
wherein the frequency modulated profile of the surface having said
auxiliary profile is defined by the following relation: y = a cos (
2 .pi. r 2 bf ( r ) ) ##EQU00007## wherein, a denotes the amplitude
of the sinusoidal curve and the diffraction efficiency at different
foci; b denotes the periodicity and add power; r denotes a radial
distance from an optical axis of the lens; and f(r) is the square
root of the pupil radius.
12. The ophthalmic lens of claim 8, wherein the sinusoidal profile
is amplitude and frequency modulated with a cosine function
operable to shift light to a selected focal plane, wherein the
amplitude and frequency modulated profile of the surface having
said auxiliary profile is defined by the following relation: y = a
cos ( .pi. r 2 r 0 ) cos ( 2 .pi. r 2 bf ( r ) ) ##EQU00008##
wherein, a denotes the amplitude of the sinusoidal curve and the
diffraction efficiency at different foci; b denotes the periodicity
and add power; r denotes a radial distance from an optical axis of
the lens; r.sub.0 is the termination pupil radius of the cosine
modulation; and f(r) is the square root of the pupil radius.
13. The ophthalmic lens of claim 1, wherein the ophthalmic lens
comprises an IOL.
14. The ophthalmic lens of claim 13, wherein the IOL is a monofocal
IOL.
15. The ophthalmic lens of claim 13, wherein the IOL is an
accommodative IOL.
16. The ophthalmic lens of claim 13, wherein the IOL is a
multifocal IOL.
17. The ophthalmic lens of claim 1, wherein the anterior surface
and the posterior surface are refractive surfaces.
Description
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 61/138,816 filed Dec. 18, 2008.
FIELD OF THE INVENTION
[0002] The present invention relates generally to ophthalmic
lenses, and more particularly to ophthalmic lenses that provide an
enhanced depth of focus.
BACKGROUND OF THE INVENTION
[0003] Intraocular lenses are routinely implanted in patients' eyes
during cataract surgery to replace the natural crystalline lens. A
variety of ophthalmic lenses are employed for correcting visual
disorders, such as, cataract, myopia, hyperopia or astigmatism. For
example, an intraocular lens (IOL) can be implanted in a patient's
eye during cataract surgery to compensate for the lost optical
power of the removed lens. In many cases, however, the implanted
lens may not provide the best focus at the targeted object
distance.
[0004] The design of modern conventional IOL optics is mainly
focused on two outcomes: an optic that provides aberration
correction to provide clear distance vision, or a multifocal optic
that can provide far vision while also providing for near vision
needs. These designs do not typically address another important
patient need, namely: for most elderly patients, the majority of
visual needs are focused around certain intermediate distances.
These elderly patients, who form a large percentage of patients
receiving IOLs to replace a natural lens, require an extended
functional vision, from distance to intermediate, to perform daily
chores. This extended functional vision is not sufficiently
provided for by current IOL designs.
[0005] Accordingly, there is a need for an improved ophthalmic
lens, and, more particularly, for an improved IOL, that can provide
an enhanced depth of focus compared to prior art IOLs.
SUMMARY OF THE INVENTION
[0006] The present invention provides ophthalmic lenses that
exhibit extended depth of field while providing sufficient contrast
for resolution of an image over a selected range of defocus
distances. Embodiments of the present invention incorporate
sinusoidal optic designs in an IOL to provide an extended
depth-of-focus in a human eye. Based on a classical sinusoidal
technique, embodiments of the present invention incorporate
amplitude modulation and frequency modulation techniques to provide
enhanced depth of focus. One embodiment can provide for attenuation
of the sinusoidal amplitude from pupil center to lens periphery,
concentrating more light energy to a single focal plane. Another
embodiment can provide for modulating the sinusoidal periodicity of
the IOL optic to change the effective lens add-power as a function
of pupil radius. An embodiment combining amplitude modulation and
frequency modulation on a sinusoidal curve can further enhance the
IOL through-focus performance and generate a desirable
depth-of-focus profile free of certain photic phenomena experienced
with conventional designs. Embodiments of the optic design of the
present invention can be applied to single focus, multifocal and/or
accommodative IOL optics.
[0007] Methods of correcting refractive errors or otherwise
enhancing vision over a range of distances are disclosed, as well
as methods of manufacturing the lenses of the present invention.
The ophthalmic lenses of the present invention can be used in
various vision correction applications including, but not limited
to, IOLs that can be used for both pseudophakic and phakic
applications. The invention can also be useful in connection with
contact lenses, intrastromal implants and other refractive
devices.
[0008] The terms "depth of field" and "depth of focus" in the
context of a lens/IOL are well known and readily understood by
those skilled in the art as referring to the distances in the
object and image spaces over which an acceptable image can be
resolved. To the extent that a quantitative measurement is
necessary to describe the present invention, the term "depth of
field" or "depth of focus" as used herein, more specifically can be
measured by an amount of defocus associated with the lens at which
a through-focus modulation transfer function (MTF) of the lens
measured with a 3 mm aperture and green light, e.g., light having a
wavelength of about 550 nm, exhibits a contrast of at least about
15% at a spatial frequency equal to about one-third of the
diffraction limited spatial frequency associated with that lens.
Other definitions can also be applied and it should be clear that
depth of field is influenced by many factors including, for
example, aperture size, chromatic content of the light from the
image, and base power of the lens itself.
[0009] An IOL according to the teachings of the invention can have
any nominal power suited for a particular application. In one
embodiment, particularly suited for IOL applications for cataract
patients, an ophthalmic lens of the invention can exhibit a nominal
power in a range of about 17 to about 25 Diopters. In other
applications, phakic lenses having negative nominal power can be
formed according to the teachings of the invention.
[0010] The lens body of a lens according to the teachings of the
invention can be formed of any suitable biocompatible material. For
example, the lens body can be formed of a soft acrylic, such as the
AcrySoft material manufactured by Alcon Laboratories, Inc., of Fort
Worth, Tex., hydrogel, or silicone material. For example, the lens
body can be formed of polymethyl methacrylate (PMMA). In some
embodiments, especially when a foldable IOL lens is desired, the
lens can be formed of a copolymer of acrylate and methacrylate. For
illustrative examples of such copolymer compositions, see for
example, U.S. Pat. No. 5,922,821 entitled "Ophthalmic Lens
Polymers" issued to Lebouef et al. on Jul. 13, 1999 and U.S. Pat.
No. 6,353,069 entitled "High Refractive Index Ophthalmic Device
Materials" issued to Freeman et al. on Mar. 5, 2002, the teachings
of both of which are hereby incorporated by reference.
[0011] Further understanding of the invention can be obtained by
reference to the following detailed description and the associated
drawings, which are described briefly below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 schematically depicts a lens according to the
teachings of this invention;
[0013] FIGS. 1A and 1B show surface profile plots of a sinusoidal
optic design;
[0014] FIGS. 2A-2D illustrate the through-focus performance of a
sinusoidal lens design for different pupil sizes;
[0015] FIGS. 3A-3I illustrate the through-focus performance inside
a human eye for a sinusoidal optic design (FIGS. 3A-3C), a
spherical lens design (FIGS. 3D-3F), and an aspheric lens design
(FIGS. 3G-3I);
[0016] FIGS. 4A and 4B show surface profile plots of an
amplitude-modulated sinusoidal optic design;
[0017] FIGS. 5A and 5B show surface profile plots of a
frequency-modulated sinusoidal optic design;
[0018] FIGS. 6A and 6B show surface profile plots of an embodiment
of the amplitude-modulated and frequency-modulated sinusoidal optic
design of the present invention; and
[0019] FIGS. 7A-7I illustrate the through-focus performance inside
a human eye for a sinusoidal optic design (FIGS. 7A-7C), for an
amplitude-modulated sinusoidal optic design (FIGS. 7D-7F) and for
an embodiment of the amplitude-modulated and frequency-modulated
sinusoidal optic design of the present invention (FIGS. 7G-7I).
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention provides an ophthalmic lens that
exhibits an extended depth of field by combining amplitude
modulation and frequency modulation on a sinusoidal curve. A lens
of the invention can thus correct refractive errors or otherwise
enhance vision by providing sufficient contrast for resolution of
an image over a selected range of defocus distances that are
commensurate with an enhanced depth of field exhibited by the
lens.
[0021] FIG. 1 illustrates schematically an exemplary lens 10
according to the teachings of this invention that includes a lens
optic 12 having two refractive surfaces 14 and 16. Although the
refractive surfaces are depicted as being generally convex, either
surface can have a generally concave shape. Alternatively, the
surfaces 14 and 16 can be selected to generate a plano-concave or a
plano-convex lens. Hence, a lens according to the teachings of the
invention can have positive or negative nominal power.
[0022] The lens optic 12 can be formed from a variety of
biocompatible soft materials. For example, the lens optic 12 can be
formed of a soft acrylic material, e.g., a copolymer of acrylate
and methacrylate, or of hydrogel or silicone. Those having ordinary
skill in the art will appreciate that in fact any soft
biocompatible material that exhibits a requisite index of
refraction for a particular application of the lens can be employed
for generating a lens of the invention, such as the above exemplary
lens 10.
[0023] The refractive surface 16 exhibits an undulating topography.
For purposes of illustration, the surface modulations have been
exaggerated. More specifically, the refractive surface 16 can be
characterized by a base curvature or profile 18, depicted by the
dashed lines, on which a continuous pattern 20 of surface
deviations are superimposed. The exemplary base profile 18 is
generally spherical and is radially symmetric about an optical axis
22 of the lens body/optic 12. Similarly, in this exemplary
embodiment, the continuous pattern of surface deviations is also
radially symmetric about the optical axis 22. Although the base
profile 18 in this embodiment is spherical, in other embodiments,
aspherical base profiles can be utilized in the practice of the
invention.
[0024] Embodiments of the amplitude and/or frequency modulated
sinusoidal optic design of the present invention can provide a
desired enhanced depth-of-focus optic design. Based on a classical
sinusoidal technique, two designs are disclosed, based on amplitude
modulation and frequency modulation. A first design attenuates the
sinusoidal amplitude of an optic from pupil center to optic
periphery to concentrate more light energy to a single focal plane.
A second design modulates the sinusoidal periodicity of an optic to
vary the effective add-power as a function of pupil radius.
Embodiments of the present invention combine the two design types
to enhance further the through-focus optic performance and generate
a desired depth-of-focus profile. Embodiments of the present
invention can be implemented as monofocal, accommodative and/or
multifocal intraocular lenses.
[0025] The numerical computation used to model the embodiments of
the present invention wad performed using the Matlab program. A
wave optics approach was selected to model the sinusoidal optic
structure and the performance evaluation mainly focuses on the
through-focus modulation transfer function at 50 (20/40 VA) and 100
Ip/mm (20/20 VA).
[0026] The classic sinusoidal design was proposed as an alternative
way to generate trifocal behavior without adverse photic effects of
sharp diffractive steps in an optic, such as an IOL optic. The
sinusoidal curve can be described by Equation 1.
y = a cos ( 2 .pi. r 2 b ) ( 1 ) ##EQU00001##
where a is a parameter determining the amplitude of the sinusoidal
curve and the diffraction efficiency at different foci, and b is a
parameter specifying the periodicity and the add power.
[0027] In a study, the parameter values a=0.5877 and b=2.2 were
used, which produced .+-.0.5 D add power. The parameter a can be
adjusted to account for the design environment change from air to
aqueous humor, as will be discussed herein. An optic surface
profile of a sinusoidal optic design is illustrated in FIGS. 1A and
1B. FIG. 1A is a 1-D surface profile plot and FIG. 1B is a surface
height map. The sinusoidal curve becomes increasingly dense from
the optic/pupil center to the optic periphery, in a manner similar
to that of a typical multifocal lens. The through-focus performance
of a lens having this design, under the assumption of no high-order
aberrations, was computed for a 3.0 mm, 4.5 mm and 5.0 mm pupil
inside a conventional wet-cell. FIGS. 2A, 2C and 2D, respectively,
illustrate these results.
[0028] The computational results reflect faithfully the unique
characteristics of a sinusoidal optic design. For small pupils
(e.g., about 3 mm), the exposed central portion is dominated by the
refractive effect (+0.5 D add) before the interference between
periodic structures occurs. The through-focus MTFs peaked at -0.57
D defocus (corresponding to +0.57 D add power), manifesting this
effect. The MTF, as shown in FIG. 2B, confirms the good optical
quality at this defocus level. At large pupils (4.5 mm and 5.0 mm),
the diffractive effects were increasingly obvious, as indicated by
three distinctive through-focus peaks at 100 Ip/mm. The evaluated
wavelength is 550 nm.
[0029] The through-focus performance of the sinusoidal design
described above was compared to existing spherical and aspheric IOL
optic designs. The results are shown in FIGS. 3A-3I. The
through-focus performance inside a human eye (a cornea with 0.28
.mu.m spherical aberration) was computed for the sinusoidal design
(FIGS. 3A-3C), a spherical lens design (FIGS. 3D-3F), and an
aspheric lens design (FIGS. 3G-3I). The performance at three
different pupil sizes was evaluated: 3.5 mm pupil (FIGS. 3A, 3D,
3G); 4.5 mm pupil (FIGS. 3B, 3E, 3H); and 6.0 mm pupil (FIGS. 3C,
3F, 31). Four typical spatial frequencies were used for evaluation:
25, 50, 75 and 100 Ip/mm.
[0030] Overall, the sinusoidal design extends the depth-of-focus as
compared to the prior art spherical and aspheric IOL optic designs.
The large amount of spherical aberration in the spherical optic
design reduces the modulation rapidly for large pupils. The
aspheric IOL optic design maintains good peak optical performance
for all pupils. However, the aspheric lens design has a limited
depth-of-focus.
[0031] For large pupils, the diffractive effect of the classical
sinusoidal design results in the modulation transfer functions
being quite low because of light-splitting into three different
foci. The reduced modulation transfers typically result in reduced
contrast sensitivity and deteriorate night driving performance. In
the past, the effect of low modulation transfers in multifocal IOL
designs was addressed with an apodization scheme. Similarly, the
sinusoidal amplitude of a sinusoidal optic can be modulated with a
cosine function which can shift more light to a selected
diffraction order, e.g., the 0-diffraction order, as pupil size
increases (e.g., in dark conditions).
[0032] An amplitude-modulated (AM) sinusoidal optic design is
illustrated in FIGS. 4A and 4B. FIG. 4A shows a 1-D surface profile
plot and
[0033] FIG. 4B shows a 2-D surface height map. The cosine
modulation function starts from 1.0 at the pupil (optic) center and
gradually reduces down to 0 at 5.0 mm pupil diameter. The
analytical description of the amplitude modulation is provided by
Equation 2.
y = a cos ( .pi. r 2 r 0 ) cos ( 2 .pi. r 2 b ) ( 2 )
##EQU00002##
where r.sub.0 is the termination pupil radius of the cosine
modulation.
[0034] FIGS. 7D-7F illustrate the through-focus performance of the
amplitude modulated sinusoidal design, as will be discussed further
below. As shown in FIG. 7F, the peak performance of 100 Ip/mm for a
6.0 mm entrance pupil has been improved from 0.28 of the sinusoidal
design to 0.40 (.about.40% increase).
[0035] An enhanced depth-of-focus may have less benefit for a large
pupil (night driving condition) and therefore a reduced
depth-of-focus for a large pupil may help to concentrate more
energy to a distance focus. A novel technique,
frequency-modulation, helped to reduce the add power of the
sinusoidal design as pupil size increased. The surface profile of a
frequency-modulated sinusoidal optic design is shown in FIGS. 5A
and 5B. FIG. 5A shows a 1-D surface profile plot and FIG. 5B shows
a 2-D surface height map. FIG. 5A also shows an unmodulated
sinusoidal optic design for comparison. Due to the nature of add
power reduction, the spacing between peaks becomes sparser from
lens/pupil center to lens periphery, which is expressed
analytically by Equation 3, below.
y = a cos ( 2 .pi. r 2 bf ( r ) ) ( 3 ) ##EQU00003##
where f(r) is the square root of the pupil radius.
[0036] To further enhance the optical performance at large pupil
size, the embodiments of the present invention combine amplitude
modulation and frequency modulation on a sinusoidal optic design,
concentrating light energy to a single focal plane. The surface
profile of an embodiment of the amplitude and frequency modulated
sinusoidal optic design of the present invention can be described
by equation (4) and a surface profile is shown in FIGS. 6A and
6B.
y = a cos ( .pi. r 2 r 0 ) cos ( 2 .pi. r 2 bf ( r ) ) ( 4 )
##EQU00004##
[0037] FIG. 6A shows a 1-D surface profile plot and FIG. 6B shows a
2-D surface height map of an embodiment of the amplitude-modulated
and frequency-modulated sinusoidal optic design of the present
invention. The combination of amplitude-modulation and
frequency-modulation improves through-focus performance of an optic
significantly. The peak modulation transfers are re-centered to the
emmetropic condition for small (3.5 mm) and medium (4.5 mm) pupils,
largely due to frequency modulation's effect. The peak MTF
performance reached roughly 0.30, 0.40 and 0.50 for 3.5 mm, 4.5 mm
and 6.0 mm respectively.
[0038] FIGS. 7A-7I illustrate the through-focus performance inside
a human eye (a cornea with 0.28 m spherical aberration) for a
sinusoidal optic design (FIGS. 7A-7C), for an amplitude-modulated
sinusoidal optic design (FIGS. 7D-7F) and for an embodiment of the
amplitude-modulated and frequency-modulated sinusoidal optic design
of the present invention (FIGS. 7G-7I). The performance at three
different pupil sizes was evaluated: 3.5 mm pupil (FIGS. 7A, 7D,
7G); 4.5 mm pupil (FIGS. 7b, 7E, 7H); and 6.0 mm pupil (FIGS. 7C,
7F, 7I). Four typical spatial frequencies were used for evaluation:
25, 50, 75 and 100 Ip/mm.
[0039] An ophthalmic lens according to the teachings of the
invention can be employed in a variety of vision correction
applications. Such applications include, but are not limited to,
intraocular lenses (IOLs), contact lenses, intrastromal implants
and other refractive devices. For example, a lens of the invention
can be employed as an improved IOL that ameliorates residual
refractive errors that are typically present after cataract
surgery. It is well known in the practice of cataract surgery that
factors, such as surgical instrument precision, IOL product
precision, preoperative biometry data, surgeon's skill level and
capsular bag differences among individuals, can cause variations in
a desired refractive error after surgery. One standard deviation of
such variations of the refractive error can be as large as 0.5
Diopters. Such residual refractive error, which can persist for a
long time, can degrade the patient's visual acuity. Consequently,
many patients require spectacles to achieve enhanced post-operative
visual acuity.
[0040] An IOL formed in accordance with the teachings of the
invention can be utilized to render outcomes of cataract surgery
more predictable, thus reducing dependence on spectacles after
cataract surgery. In particular, an IOL of the invention can
include a refractive surface having surface deviations that cause
an enhancement of the IOUs depth of field, and hence lower the
IOL's sensitivity to errors described above. In other words, an eye
of a patient in which an IOL of the invention is implanted exhibits
an increased depth of focus, and hence provides improved visual
performance within a wider range of defocus. Accordingly,
post-operative variations in refractive error have a reduced impact
on the patient's visual performance.
[0041] Those having ordinary skill in the art will appreciate that
various modifications can be made to the above embodiments without
departing from the scope of the invention.
* * * * *