Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INTRAOCULAR LENS HAVING EXTENDED DEPTH OF FOCUS
Related Application
The present application claims priority under 35 U.S.C 119(e) to provisional
application
No. 60/968,250, filed on August 27, 2007 and to patent application no.
12/120,201, filed on
May 3, 2008, and are herein incorporated in its entirety.
Background of the Invention
Field of the Invention
The present invention relates generally to intraocular lenses and more
specifically to
intraocular lenses having an extended depth of focus.
Description of the Related Art
Intraocular lenses are commonly used to replace the natural lens of the eye
when it
become cataractous. Alternatively, the natural lens may be replaced to correct
other visual
conditions, for example, to provide accommodation or pseudo-accommodation when
a
subject develops presbyopia and is not longer able to focus on both distant
objects and near
objects. In any event, accommodating and/or multifocal intraocular lenses may
be used to
restore at least some degree of accommodative and/or pseudo-accommodative
ability.
Accommodating intraocular lenses are configured to focus on objects over a
range of
distances by moving axially and/or by changing shape in response to an ocular
force
produced by the ciliary muscle, zonules, and/or capsular bag of the eye. One
problem
encountered with accommodating intraocular lenses is an inability to utilize
the available
ocular forces to produce the full accommodative range typical of a younger
eye.
Multifocal intraocular lenses provide a pseudo-accommodation by simultaneously
providing two or more foci, for example, one to provide distant vision and the
other to
provide near vision. Over time, patients with multifocal intraocular lenses
generally learn to
select the focus that provides the sharper image and to ignore any other
blurred images. One
problem with multifocal intraocular lenses is a relatively high degree of
dysphotopsia (e.g.,
halos or glare) and reduced contrast sensitivity due to the continual presence
of defocused
light.
Another approach for providing some degree of simulated accommodation is to
extend the depth of focus of a traditional monofocal lens so that objects over
a broader range
of distances are simultaneously resolve. Again, issues such as contrast
sensitivity and
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reduced contrast sensitivity are typical. Examples of this approach are
discuss in USPN's
6,126,286 (Portney), 6,923,539 (Simpson et al.), and 7,061,693 (Zalevsky).
Accommodating and multifocal intraocular lenses are needed with enhanced
performance and increased design flexibility in addressing the variety of
complex issues
involved in providing vision to subjects over a wide range of object
distances.
Summary of the Invention
The present invention is generally directed to ophthalmic devices, systems,
and
methods for extending the depth of focus of a subject's vision. The ophthalmic
device may
be an intraocular lens, a contact lens, a corneal inlay or onlay, a pair of
spectacles, or the like.
Alternatively, the ophthalmic device may be a part of the or structure of a
natural eye, for
example, the resulting structure on a corneal surface produced by a refractive
procedure such
as a LASIK or PRK procedure. Embodiments of the present invention may find
particular
use in ophthalmic devices having a multifocal element (e.g., a diffractive or
refractive lens
producing two or more foci or images) or having accommodative capabilities.
In one aspect of the present invention, a lens for ophthalmic use, such as an
intraocular lens, comprises an optic having an aperture disposed about an
optical axis. The
optic comprises a first surface having a first shape and an opposing second
surface having a
second shape. The optic further comprises an extended focus mask that is
disposed on at
least one of the shapes. The first and second surfaces provide a base power
and an add
power. The powers are selected to produce a first focus and a second focus
when the
intraocular lens is placed within an eye of a subject. At least one of the
first focus and
second focus have a depth of focus, when illuminated by a light source over
the entire
aperture, that is greater than a depth of focus of a reference optic without
the extended focus
mask. The reference optic may have an aperture equal to the aperture of the
intraocular lens
and at least one of a base power equal to the base power of the ophthalmic
lens and an add
power equal to the add power of the ophthalmic lens.
In another aspect of the present invention, an accommodating intraocular lens
comprises an optic having an aperture disposed about an optical axis. The
optic comprises a
first surface having a first shape and an opposing second surface having a
second shape. The
intraocular lens further comprises an extended focus mask that is disposed on
at least one of
the shapes. The first and second surfaces provide a base power that is
selected to produce a
focus when the intraocular lens is placed within an eye of a subject. The
intraocular lens has
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a depth of focus, when illuminated by a light source over the entire clear
aperture, that is
greater than the depth of focus of a reference optic without the extended
focus mask. The
reference optic may have a base power and a clear aperture that are
substantially equal to that
of the intraocular lens. The intraocular lens is configured, in response to an
ocular force, to
change the optical power of the base power by at least 1 Diopter.
Brief Description of the Drawings
Embodiments of the present invention may be better understood from the
following
detailed description when read in conjunction with the accompanying drawings.
Such
embodiments, which are for illustrative purposes only, depict the novel and
non-obvious
aspects of the invention. The drawings include the following figures, with
like numerals
indicating like parts:
FIG. 1 is a schematic drawing of a human eye after implantation with an
intraocular
lens.
FIG. 2 is an exploded side view of a lens according to an embodiment of the
present
invention where individual profiles of anterior and posterior lens surfaces
have been
separated from their perspective base profiles for clarity.
FIG. 3 is a side view of the lens shown in FIG. 2 showing the resultant
surface
profiles of the anterior and posterior surfaces.
FIG. 4 is a front view of the lens shown in FIG. 2 showing echelettes of the
anterior
surface according to an embodiment of the present invention.
FIG. 5 is a side view of an optic showing a low-add diffractive mask according
to an
embodiment of the present invention.
FIG. 6 is a through-focus plot of a simulated Modulation Transfer Function for
the
optic shown in FIG. 5
FIG. 7 is an exploded side view of a lens according to another embodiment of
the
present invention where individual profiles of anterior and posterior lens
surfaces have been
separated from their perspective base profiles for clarity.
FIG. 8 is a side view of the lens shown in FIG. 7 showing the resultant
surface
profiles of the anterior and posterior surfaces.
FIG. 9 is a rear view of the lens shown in FIG. 7 showing phase-affecting, non-
diffractive mask according to an embodiment of the present invention.
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FIG. 10 is a front view of a phase-affecting, non-diffractive mask according
to
another embodiment of the present invention.
FIG. 11 is a front view of a phase-affecting, non-diffractive mask according
to yet
another embodiment of the present invention.
FIG. 12 is a perspective view of an accommodating intraocular lens according
to an
embodiment of the present invention.
FIG. 13 is a perspective view of a positioning member the accommodating
intraocular lens shown in FIG. 12.
FIG. 14 is a perspective view of the accommodating intraocular lens shown in
FIG.
12 showing arms from the positioning member protruding into an optic.
Detailed Description
Embodiments of the present invention are generally directed to multifocal and
accommodating ophthalmic lenses having at least one extended depth of focus.
Embodiments of the present invention will be illustrated for intraocular
lenses; however,
other types of lenses, particularly other types of ophthalmic lenses, are
anticipated.
Embodiments of the present invention may be utilized as pseudophakic
intraocular lenses in
which an intraocular lens replaces the natural lens, supplemental intraocular
lenses in which
an intraocular lens is combined with a previously implanted intraocular lens,
or phakic
intraocular lenses in which an intraocular lens supplements the natural lens
of the eye (e.g.,
by implantation of an intraocular lens in front of the iris or in the sulcus
of a subject eye).
These include, but are not limited to, spectacles, contact lenses, corneal
implants, and the
like. Embodiments of the present invention may also be extended to ophthalmic
procedures,
for example, to corneal refractive surgical procedures such as LASIK or PRK.
Referring to FIG. 1, in certain embodiments an intraocular lens 100 is
implanted
within an eye 10 of a subject such as a human patient. The eye 10 is generally
disposed
about an optical axis OA and includes a posterior segment 11, retina 12, a
cornea 14, an
anterior chamber 15, an iris 16, and a capsular bag 17 having a posterior wall
18. Prior to
surgery, a natural lens occupies essentially the entire interior of the
capsular bag 17. The eye
10 further comprises a ciliary muscle 20 and zonules 22 that transmit ocular
forces produced
by the ciliary muscle 20 to the capsular bag 17. Such ocular forces serve to
provide
accommodation in a phakic eye still containing the natural lens, for example,
by deforming
the natural lens to change its optical power.
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After surgery, the capsular bag 17 houses the intraocular lens 100. The
intraocular
lens 100 is described in more detail below. Light enters from the left of FIG.
1 and is
focused onto the retina 12 by the cornea 14 and the intraocular lens 100.
After passing
through the intraocular lens 100, light passes through the posterior segment
11, and strikes
the retina 12, which detects the light and converts it to a signal transmitted
through the optic
nerve to the brain. The intraocular lens 100 includes an optic or optical
element 102 that has
a refractive index that is generally greater than the refractive index of the
surrounding fluid.
The optic 102 has an anterior surface 104 facing away from the retina 12 and a
posterior
surface 106 facing toward the retina 12, the surfaces 104, 106 are disposed
about an optical
axis OA. The optic 102 may be disposed adjacent to, and even pressed against,
the posterior
wall 18, for example, to reduce cellular growth on the optic 102 and the
capsular bag 18.
Alternatively, the optic 102 may be vaulted anteriorly toward the cornea 14,
for example, so
that the optic 100 moves away from the retina 12 in response to an ocular
force on the
intraocular lens 100.
The intraocular lens 100 and the optic 102 may be configured to provide
accommodative or pseudo-accommodative vision. The optic 102 may be a bifocal
or
multifocal lens providing a plurality of focal lengths or optical powers, for
example, a first
focus or optical power to provide distant vision or intermediate vision and
second focus or
optical power to provide near or intermediate vision. The plurality of powers
may be
provided by either refractive and/or diffractive means. In some embodiments, a
distribution
between near and distant vision is constant or substantially constant over a
variety of pupil
sizes or lighting conditions. In other embodiments, the distribution between
near and distant
vision varies in a predetermined manner as the pupil size or lighting
conditions vary, for
example, as disclosed by Lee et al. in USPN 5,699,142 or one of the Portney
patents
referenced herein.
Alternatively or additionally, the intraocular lens 100 and the optic 102 may
be
configured to provide accommodative power by deforming and/or moving the optic
102
along the optical axis OA in response to an ocular force. In some embodiments,
the optic
102 may be a monofocal, bifocal, or multifocal lens. The optic 102 is attached
to a
positioning member or haptics 110, thereby operably coupling the optic 102 to
the capsular
bag 17. The haptics 110 are configured to transfer an ocular force to the
optic 102 to provide
accommodative movement or deformation. As used herein, an "ocular force" is
typically a
force produced by an eye to provide accommodation, for example, a force
produce by the
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ciliary muscle, zonules, or capsular bag of an eye. An ocular force may
generally be
considered to be a force that is in a range from about 1 gram force to about
50 grams force,
about 1 gram force to about 6 grams force or about 9 grams force, or from
about 6 gram
force to about 9 grams force. The difference in optical power between the
farthest and
nearest objects that may be brought into focus by a particular lens or lens
system is known
typically as the "accommodative range". A normal accommodative range is about
3 Diopter
or about 4 Diopters at the plane of the optic 102, although this range may be
extended to as
high as 6 Diopters or more, depending on a subject's age, patient or doctor
preference, the
geometry of a patient's eye, and the like.
If the optic 102 is a bifocal or multifocal optic, then it may be
characterized by a
"base power" and at least one "add power". As used herein the term "base
power" means a
power (in Diopters) of an optic or lens required to provide distant vision at
the retina of a
subject eye. As used herein, the term "add power" means a difference in
optical power (in
Diopters) between a second power of the optic or lens and the base power. When
the add
power is positive, the sum of the add power and the base power corresponds to
a total optical
power suitable for imaging an object at some finite distance from the eye onto
the retina. A
typical maximum add power for an optic or lens is about 3 Diopter or about 4
Diopters in the
plane of the lens, although this number may be as high as 6 or more Diopters
(an intraocular
lens add power of 4.0 Diopters is approximately equal to an increase in
optical power of
about 3.2 Diopters in a spectacle lens).
FIGS. 2 and 3 are side views of the intraocular lens 100 showing only the
optic 102
and not the haptics 110. In certain embodiments the optic 102 has a clear
aperture 112 that is
disposed about the optical axis OA. As used herein, the term "clear aperture"
means the
opening of a lens or optic that restricts the extent of a bundle of light rays
from a distant
source that can be imaged or focused by the lens or optic. The clear aperture
is typically
circular and is specified by its diameter, although other shapes are
acceptable, for example,
oval, square, or rectangular. Thus, the clear aperture represents the full
extent of the lens or
optic usable for forming the conjugate image of an object or for focusing
light from a distant
point source to a single focus, or to a plurality of predetermined foci in the
case of a
multifocal optic or lens. It will be appreciated that the term clear aperture
does not limit the
transmittance of the lens or optic to be at or near 100%, but also includes
lenses or optics
having a lower transmittance at particular wavelengths or bands of wavelengths
at or near the
visible range of the electromagnetic radiation spectrum. In some embodiments,
the clear
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aperture has the same or substantially the same diameter as the optic.
Alternatively, the
diameter of the clear aperture may be smaller than the diameter of the optic,
for example, due
to the presence of a glare or PCO reducing structure disposed about a
peripheral region of the
optic.
The anterior surface 104 has an anterior shape or base curvature 114 and the
opposing posterior surface 106 has a posterior shape or base curvature 116,
the shapes 114,
116 providing a refractive power that is generally sufficient to at least
provide distant vision.
The optic 102 may further comprise a multifocal pattern 118 that is added to
the anterior
shape 114, the multifocal pattern 118 being configured to provide two or more
foci within the
visible range of the electromagnetic spectrum, for example, a focus selected
to provide
distant vision and a focus selected to provide near vision to a subject, or a
focus selected to
provide distant vision and a focus selected to provide intermediate vision to
a subject.
As used herein, the term "near vision" means vision produced by an eye that
allows a
subject to focus on objects that are within a range of about 25 cm to about 40
cm from the
subject, or at a distance at which the subject would generally place printed
material for the
purpose of reading. As used herein, the term "intermediate vision" means
vision produced
by an eye that allows a subject to focus on objects that are located from
about 40 cm to about
2 meters from the subject. As used herein, the term "distant vision" means
vision produced
by an eye that allows a subject to focus on objects that are at a distance
that is greater than 2
meters, at a distance of 5 meters or about 5 meters from the subject, or at a
distance of 6
meters or about 6 meters from the subject. The object distance may also be
expressed in
relation to an amount of add power, in Diopters, suitable for focusing an
object at that
distance onto the retina of an emmetropic eye. For example, an add power of 1
Diopter is
suitable for focusing an object onto the retina that is located at a distance
of 1 meter from an
emmetropic eye in a disaccommodative state (e.g., with a relaxed ciliary
muscle), while add
powers of 0.5 Diopter, 2 Diopters, 3 Diopters, and 4 Diopters are suitable for
focusing an
object onto the retina that is located at a distance of 2 meters, 50 cm, 33
cm, and 25 cm,
respectively, from an emmetropic eye in a disaccommodative state.
The shapes 114, 116 of the optic 102 may have a shape or profile that may be
either
spherical or aspheric. The shape of the surface may be represented by sag Z
given by the
following equation:
z
Z(r)= r /R +ADr4+AEr6+...
1+ 1-r2(CC+1)/R2
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where r is a radial distance from the center or optical axis of the lens, R is
the
curvature at the center of the lens, CC is the so-called conic constant, and
AD and AE are
polynomial coefficients additional to the conic constant CC. While the optic
102 is biconvex
in the illustrated embodiment, other lens shapes are a possible, for example,
plano-convex,
plano-concave, bi-concave, and the like.
The optic 102 further comprises an extended focus pattern or mask 120 that is
disposed on, added to, or combined with the posterior shape 116, the extended
focus pattern
120 being configured to provide an extended depth of focus. The extended focus
mask 120 is
configured to extend the depth of focus of the at least one of the foci
produced or provided by
the multifocal pattern 118. For example, the optic 102 may be a bifocal optic
providing two
foci or optical powers within the visible light band. In such embodiments, the
first and
second foci of the optic 102 each have a depth of focus that is greater than
the depth of focus
for each of the foci of a multifocal reference optic without the mask 120, the
reference optic
having a base power, an add power, and a clear aperture that are equal or
substantially equal
to that of the intraocular lens 100 or the optic 102.
As used herein, the terms "extended focus" or "extended depth of focus," mean
a
depth of focus of a test lens, optic, or optical element (generally referred
to herein as an
"optic") that exceeds the depth of focus of a reference optic comprising
biconvex or
biconcave surfaces of equal radii of curvature, the reference optic having an
optical power or
focal length that is equal to an optical power or focal length of the test
optic, wherein the
depth of focus for the test optic and the reference optic are determined under
the same
aperture conditions and under equivalent illumination conditions (e.g., the
same or an
equivalent object, such as a point light source or a test target, for each
optic that is placed the
same distance or distances from each optic). In the case of a multifocal test
optic, the
reference optic may comprise a monofocal optic having a focal length or
optical power that is
equal to one of optical power or focal length of the test optic. In the case
where the extended
focus or extended depth of focus is attributable to a particular feature,
structure, or mask
associated with the test optic, the reference optic may be one that is made of
the same
material and has the same structure as the test optic, except without the
particular feature,
structure, or mask. For example, if a test optic is a refractive or
diffractive multifocal optic
comprising a mask for extending the focus or depth of focus of at least one of
the foci formed
by the test optic, then a suitable reference optic may be one made of the same
material(s) as
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the test optic having the same structure as the test optic (e.g., surface
shapes/curvatures,
thickness, aperture, echelette geometry, and the like), except without the
mask.
As used herein, the terms "optical power" of an intraocular lens or associated
optic
means the ability of the intraocular lens or optic to focus light when
disposed within a media
having a refractive index of about 1.336 (the average refractive index of the
aqueous and
vitreous humors of the human eye; see ISO 11979-2). As used herein the terms
"focus" or
"focal length" of an intraocular lens or associated optic is the reciprocal of
the optical power
in meters when the intraocular lens is disposed within a media having a
refractive index of
1.336. As used herein the term "power" means "optical power". As used herein,
the term
"light" means incident electromagnetic radiation within the visible waveband,
for example,
electromagnetic radiation with a wavelength in a vacuum that is between 390
nanometers and
780 nanometers. Except where noted otherwise, optical power (either absolute
or add power)
of an intraocular lens or associated optic is from a reference plane through
the intraocular
lens or associated optic (e.g., a principal plane of an optic).
As used herein, the term "depth of focus" generally refers to a range of
placement of
an image plane over which an image produced by an optic or lens system (e.g.,
the cornea
and an intraocular lens) maintains a predetermined optical performance, and
generally refers
to an image-side depth or range. The depth of focus may be determined, for
example, by
moving an object (e.g., a resolution target or a point light source) along an
optical axis and
determining the range of corresponding images that maintain a predetermined
optical
performance at the image plane. It will be appreciated that the depth of focus
may be
alternatively expressed in terms of "depth of field", which generally refers
to a range object
locations over which a corresponding image produced by an optic or lens system
maintains a
predetermined optical performance at an image plane, and generally refers to
an object-side
depth or range. The predetermined optical performance for determining either
depth of focus
or depth of field may be based on various criteria, such as through-focus
performance or
variation (either absolute or percent, such as full-width-half-max (FWHM)) of
MTF, spot
size, wavefront error, Strehl Ratio, or any other suitable criterion or
performance metric.
In determining or providing a depth of focus, an extended focus, or an
extended depth
of focus, the determination may be based on through-focus MTF data at a
particular spatial
frequency. For example, the depth of focus may be defined as the region in a
through-focus
plot over which the Modulation Transfer Function (MTF) at a spatial frequency
of 50 line
pairs per mm exceeded a selected cutoff value. Typical cutoff values may
include 0.05, 0.10,
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0.15, 0.17, 0.20, 0.25, or higher. Other spatial frequencies may include 25
line pairs per mm
or 100 line pairs per mm. Another way to define the depth of focus is based on
a relative
threshold, where the threshold is defined based on a peak value of a figure of
merit. For
instance, the depth of focus may be defined as the full width at half max
(FWHM) of the
MTF at a particular spatial frequency. Other relative thresholds may be 95%,
90%, 80%,
70%, 60%, 50%, 1/e, 1/e^2 of a peak value of the MTF, or any suitable fraction
of the peak
value of MTF or another metric.
The depth of focus may be defined in terms of an axial distance, or,
equivalently, in
terms of a power. The figures of merit, or metrics, may be either purely
optical in nature, or
may incorporate some perception effects from the human eye. For instance, any
or all of the
following optical metrics may be used: MTF at a particular spatial frequency,
MTF volume
(integrated over a particular range of spatial frequencies, either in one
dimension or in two
dimensions), Strehl ratio, encircled energy, RMS spot size, peak-to-valley
spot size, RMS
wavefront error, peak-to-valley wavefront error, and edge transition width.
Alternatively, any of the following psychophysical metrics may be used:
contrast
sensitivity, visual acuity, and perceived blur. In addition, other metrics may
be found in the
literature, such as those detailed in Marsack, J.D., Thibos, L.N. and
Applegate, R.A., 2004,
"Metrics of optical quality derived from wave aberrations predict visual
performance," J Vis,
4 (4), 322-8; Villegas, E.A., Gonzalez, C., Bourdoncle, B., Bonnin, T. and
Artal, P., 2002,
"Correlation between optical and psychophysical parameters as a function of
defocus,"
Optom Vis Sci, 79 (1), 60-7; van Meeteren, A., "Calculations on the optical
transfer function
of the human eye for white light," Optica Acta, 21 (5), 395-412 (1974), all of
these
references being herein incorporated by reference in their entirety.
Any or all of the above metrics may be defined at a single wavelength, such as
550
nm or any other suitable wavelength, at a plurality of selected wavelengths,
or over a spectral
region, such as the visible spectrum from 400 nm to 700 nm. The metrics may be
weighted
over a particular spectral region, such as the weighting associated with the
spectral response
of the human eye. It will be appreciated that the above criteria may be used
in determining or
comparing the performance of any of the optic discussed herein.
In certain embodiments, a test optic with an extended depth of focus may be
evaluated in terms of its optical performance over a range of defocus
conditions, as compared
to a reference optic (e.g., as defined above herein). For example, the test
optic with an
extended depth of focus may have an MTF that is above a predetermined
threshold value
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(e.g., 0.05, 0.10, 0.15, 0.17, 0.20, 0.25, or higher) at a particular
frequency (e.g., 25, 50, or
100 line pairs per mm) over a defocus range that is greater than that of the
corresponding
reference optic. The defocus range may be expressed in terms of object space
distances,
image space distances, or Diopter power. In some embodiments, the test optic
with an
extended depth of focus may specified in terms of an increased in depth of
focus as compared
to the corresponding reference optic, either in absolute terms (e.g., an
increased defocus
range compared to the reference optic over which a predetermined MTF
performance is
maintained) or in relative terms (e.g., a percent increase in defocus range
compared to a
reference optic, such as a 10%, 20%, 50%, 100%, 200%, or greater increase in
defocus range
compared to a reference optic).
Referring to FIG. 4, which is a front view of the optic 102 only and without
the
haptics 110, the multifocal pattern 118 comprises a plurality of echelettes
including a central
echelette that is generally circular and surrounded by a plurality of annular
echelettes. The
outer diameter and surface shape of each echelette are generally selected to
provide
constructive interference between the echelettes when light is incident on the
optic 102,
wherein light in two or more diffractive orders of the multifocal pattern 118
are focused to
different points or foci along the optical axis OA. In some embodiments, the
multifocal
pattern 118 comprises a refractive multifocal element, for example, having
radial profile as
disclosed in USPN's 5,225,858 (Lang) or 6,210,005 (Portney), which are herein
incorporated
in their entirety. Typically, the multifocal pattern 118 has an add power of
at least 2
Diopters, 3 Diopters, or 4 Diopters, depending on such factors as patient or
doctor
preference, accommodative capabilities of the intraocular lens 100 and/or eye
10, and the
nature of the extended focus mask 120.
Referring to FIG 5, an exemplary extended focus mask is illustrated for an
optic 102'
comprising an anterior surface 104' and a posterior surface 106' disposed
about an optical
axis OA. The extended focus mask of the optic 102' is in the form of a low-add
diffractive
mask 120' disposed on, added to, or combined with a base curvature or shape of
the posterior
surface 106'. The low-add diffractive mask 120' may comprise a blazed profile,
for
example, as described by equations equal or similar to those in an article by
A.L. Cohen,
"Practical design of a bifocal hologram contact lens or intraocular lens,"
Applied Optics,
31(19), 3750-3754 (1992). The diffractive element provided two foci
corresponding to the
0th and +lsr diffracted orders of the low-add diffractive mask 120'. The
radius of a first
central echelette from an optical axis may be 0.95 mm, corresponding to an add
power of
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about 1.2 Diopters for a silicone lens disposed within aqueous humor of the
human eye. The
depth of the profile is 3.2 microns, which converts to a phase imparted upon
transmission of
(3.2 microns times (1.459-1.336) divided by design wavelength of 0.555
microns, where
1.336 is the refractive index of the aqueous humor), or about 0.7 wavelengths,
or about 255
degrees of phase. The parabolic profile extends across all zones, with a step
discontinuity at
the edge of each zone.
To assess the ability of the low-add diffractive mask 120' to produce an
extended
depth of focus, an eye model was used in which the optic 102' was configured
for use as an
intraocular lens. The optic 102' was modeled as a biconvex lens in which the
surfaces 104',
106' each had a base radius of curvature of 12.154 mm with a conic constant of
0 (i.e.,
spherical surfaces). In other words, the shape of the anterior and posterior
surfaces were
spherical. Alternatively, the anterior and/or posterior surfaces of the lens
may include a non-
zero conic constant or one or more aspheric terms. The lens material was a
silicone material
with a refractive index of about 1.459 at a wavelength of 555 nm. The
thickness between the
surfaces 104', 106' along the optical axis OA was selected as 1 mm.
The optic 102' was modeled as an intraocular lens and placed into an eye model
under polychromatic light conditions, as described in an article by H.L. Liou.
and N.A.
Brennan, "Anatomically accurate, finite model eye for optical modeling," J Opt
Soc Am A,
14(8), 1684-1695. The Liou-Brennan model eye uses distances and curvatures
that
correspond to those in an average-shaped, average-sized human eye.
The model used an object placed at infinite distance from the eye. The media
between the object and the eye was air with a refractive index of 1. The model
included a
model cornea with a radius of curvature of +7.77 mm and a conic constant (also
known as
"asphericity") of -0.18. The model cornea had a thickness of 0.5 mm and a
refractive index
of about 1.376 at a wavelength of 555 nm. The posterior surface of the cornea
had a radius
of curvature of +6.4 mm and a conic constant of -0.6. The eye model also
included an iris
located a distance of 3.16 mm from the cornea posterior surface along the
optical axis OA.
The optic 102' was disposed along an intraocular lens plane located 0.5 mm
from iris.
The refractive index of the material between the cornea posterior surface and
the optic 102'
was that of the aqueous humor, which is equal to 1.336 at a wavelength of 555
nm. The
separation between posterior surface 106' and the iris (image plane) was about
18.7 mm;
however, the value was set as a "solve" value, for example as used in raytrace
programs such
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as OSLO or ZEMAX. The refractive index between the optic 102' and the retina
was set to
that of the vitreous humor, 1.336 at a wavelength of 555 nm.
A reference optic was also modeled as a benchmark for comparison to the optic
102'
using the Liou-Brennan model eye as specified above. The reference optic had a
base power
and a clear aperture that are substantially equal to that of the optic 102'.
Like the optic 102',
the reference optic also was modeled as a biconvex lens with anterior and
posterior surfaces
with a radius of curvature of 12.154 mm with a conic constant of 0 (i.e.,
spherical surfaces).
Also like the optic 102', the anterior/posterior surfaces were separated by 1
mm along the
optical axis.
A simulation based on the above model eye was performed in order to evaluate
the
optical performance of the optic 102'. The eye model was also used to compare
the
performance of the optic 102' to the reference optic described in the previous
paragraph.
Additionally or alternatively, the eye model may be used to adjust the design
of the optic
102' by modifying certain parameters of the optic 102' so as to provide a
predetermined
optical performance, an optimized optical performance based on a metric,
and/or an
improved optical performance compared to a reference optic. For example, the
amount of
add power may be adjusted to provide a design of the optic 102' that provides
a desired
performance.
The simulation based on the above model eye used a primary wavelength of 555
nm
and a weighting for other wavelengths in accordance with the spectral response
of the eye.
In other embodiments, the optic 102' may be designed and/or evaluated using
other
weighting factors, for example, to account for varying lighting conditions
and/or to account
for differences between scotopic and photopic vision. Alternatively, the optic
102' may be
designed and/or evaluated at a plurality of two or three wavelengths
representative of the
visible range or a particular lighting condition, or at a single wavelength
representative of the
visible range or a particular lighting condition (e.g., at a wavelength of 550
nm).
FIG. 6 is a through-focus plot of the simulated Modulation Transfer Function
at 50
line pairs per mm (or, equivalently, cycles per mm or c/mm) for the optic 102'
containing the
low-add diffractive mask 120' and the reference optic w/o a low-add
diffractive mask. The
plots show the performance of the optic 102' and the reference optic when each
is placed in
the eye model. The extended focus optic 102' has a reduced peak MTF, but an
increased
width to the MTF curve, compared to the reference optic.
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A depth of focus for the two optics based on the results shown in FIG. 6 may
be
defined in various ways. One definition of depth of focus is the continuous
range over which
the MTF is above a threshold value of 0.17, for example. Using this
definition, the reference
optic has a depth of focus of 1.36 Diopters, and the optic 102' has a depth of
focus of 1.90
Diopters, which is about 39% larger than the reference optic. Another
definition of depth of
focus uses a threshold value of 0.20, for example. Using this definition, the
reference optic
has a depth of focus of 1.25 Diopters and the optic 102' has a depth of focus
of 1.72
Diopters, which is about 37% larger than the reference optic. It will be
appreciated that such
definitions may be used to evaluate the depth of focus and/or performance for
any lens or
optic according to embodiments of the present invention.
Returning to the illustrated embodiment of FIGS. 2-4, the extended focus mask
120
of the multifocal optic 102 comprises a diffractive pattern providing a low
add power that is
similar or equivalent to the low-add diffractive mask 120' discussed above.
The mask 120
comprises a diffractive pattern that is generally similar to the multifocal
pattern 118 in that
the mask 120 includes a plurality echelettes configured to provide
constructive interference.
However, in contrast to the multifocal pattern 118, the mask 120 is
constructed to provide a
relatively low add power, for example, less that 2 Diopters, less than 1.5
Diopter, or even less
than 1 Diopter of add power. The relatively low add power provided by the mask
120 serves
to extend the depth of focus of at least one of the two foci of the optic 102
produced by the
multifocal pattern 118 in cooperation with the refractive surfaces 114, 116.
Surprisingly, the low-add power of the extended focus mask 120 not only
extends the
depth of focus of the individual foci produced by the multifocal pattern 118,
but may be
configured to also provide enhanced visual acuity or performance over a range
of viewing
distances between the two view distances corresponding to the two foci of the
multifocal
pattern 118 (e.g., having an MTF at 50 line pairs per mm or 100 line pairs per
mm that is
above 0.05, 0.10, 0.15, 0.17, 0.20, or more). For example, the multifocal
pattern 118 may be
selected to produce a first focus corresponding to distant vision (e.g., in
which objects at
distances of at least 6 meters, or at 10 meters or farther, appear to be in
focus) and a second
focus corresponding to near vision (e.g., in which objects at 30 cm, 35 cm, or
less than 40 cm
appear to be in focus). In such embodiments, the extended focus mask 120 may
be
configured to increase visual acuity or optical performance not only at
distances near the foci
of the multifocal pattern 118 (e.g., at distances of 25 cm, 40 cm, and/or 6
meters), but also
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over a range of distances therebetween (e.g., at distances of 1 meter, 2
meters, 3 meters, 4
meters, and/or 5 meters).
In certain embodiments, one of the focal lengths of the optic 102 and/or the
multifocal pattern 118 corresponds to a predetermined viewing distance for
intermediate
vision, or to a predetermined viewing distance that is between intermediate
vision and distant
vision (e.g., a predetermined viewing distance that is from about 2 meters to
about 6 meters).
In such embodiments, the optic 102 and the extended focus mask are configured
so that the
visual acuity or performance of the optic 102 is above a threshold value both
for distant
vision, the predetermined viewing distance, and viewing distances that are
less than the
predetermined viewing distance (e.g., having an MTF at 50 line pairs per mm or
100 line
pairs per mm that is above 0.05, 0.10, 0.15, 0.17, 0.20, or more). For example
if the
predetermined viewing distance is selected to be 5 meters, the optic 102 may
be configured
to provide a predetermined visual acuity or optical performance at distances
of 4 meters, 5
meters, 6 meters, and at distances greater than 6 meters.
In certain embodiments, one of the foci of the optic 102 and/or the multifocal
pattern
118 is selected to correspond to a so-called "hyperfocal distance," and the
visual acuity or
performance of the optic 102 is above a threshold value for objects at
distances that are
greater than the hyperfocal distance and for objects at distances that are
less than the
hyperfocal distance (e.g., having an MTF at 50 line pairs per mm or 100 line
pairs per mm
that is above 0.05, 0.10, 0.15, 0.17, 0.20, or more). As used herein, the term
"hyperfocal
distance" means a distance from a healthy, emmetropic eye, at which an add
power of 0.5
Diopters in the spectacle plane provides visual acuity at least 20/20, based
on the standard
Snellen test for visual acuity. For example, in a human eye with an axial
length (AL) of 25
mm, the hyperfocal distance is approximately 2.5 meters from the eye. As used
herein, the
term "emmetropic eye" means an eye having a visual acuity for distant vision
of at least
20/20, based on the standard Snellen test for visual acuity. As used herein,
the term
"emmetropic vision" means vision which provides a visual acuity for distant
object of at least
20/20. In such embodiments, the optic 102 may be configured to provide a
predetermined
visual acuity or optical performance at distances of 1 meter or 1.5 meters, at
a distance of 2.5
meters, and at a distance greater than 2.5 meters (e.g., 3 meters, 4 meters, 6
meters, and/or
distances greater than 6 meters).
In other embodiments, a first focal length of the optic 102 and/or the
multifocal
pattern 118 is set to correspond to a first distance that is greater than that
typical for near
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vision, while a second focal length of the optic 102 and/or the multifocal
pattern 118 is set to
correspond to distant vision or a relatively large viewing distance such as a
hyperfocal
distance or some other distance between about 3 meters and 6 meters. For
example, the first
focal length may be selected to correspond to a distance of or about 40 cm, 50
cm, 1 meter,
or 1.5 meters, while the second focal length corresponds to a distance of or
about 2.5 meters,
3 meters, 4 meters, or 5 meters. In such embodiments, the optic 102 may
provide visual
acuity that is above a predetermined threshold over all distances between the
distances
corresponding to the first and second focal lengths (e.g., having an MTF at 50
line pairs per
mm or 100 line pairs per mm that is above 0.05, 0.10, 0.15, 0.17, or 0.20 at
all distances
between 50 cm and 2.5 meters or between 50 cm and 3 meters). In such
embodiments, the
extended depth of focus of the two foci produced by the combination of the
multifocal
pattern 118, the extended focus mask 120, and the refractive power of the
surfaces 104, 106
may be configured to provide functional vision and/or a contrast sensitivity
that is above a
predetermined threshold over an entire range of distances (e.g., a
predetermined vision
performance for objects disposed anywhere between 14 inches and 20 feet from a
subject).
For example, a multifocal lens having a near (or intermediate) focus point and
a distance
focus point may be configured so that the through-focus MTF of the intraocular
lens within
an eye model or subject eye is above a predetermined threshold value for all
add powers
between zero and 3 Diopters or between zero and 4 Diopter.
It will be appreciated that structural and material variations of the optic
102 as
compared to the illustrated embodiment of FIGS. 2-4 are include herein. For
example, the
extended focus mask 120 may be disposed on the anterior surface 104, while the
multifocal
pattern 118 may be disposed on the posterior surface 106. Alternatively, the
multifocal
pattern 118 and the mask 120 may be combined onto a single surface 104 or 106.
Furthermore, the multifocal pattern 118 may be replaced with or supplemented
by a
refractive multifocal pattern. Also, the extended low-add diffractive mask 120
illustrated in
FIGS. 2-4 may be replaced by or combined with another type of pattern or mask
that is
selected to provide an extended depth of focus to one or more of the foci
produced by the
multifocal pattern 118. In certain embodiments, at least one of the surfaces
104, 106
comprises a diffractive pattern that is apodized or is otherwise configured to
provide an
optical performance and/or depth of focus that varies with a subject's pupil
size or varying
light conditions, for example, as discussed by Lee et al. in USPN 5,699,142.
In addition,
structural and/or material characteristics of the optic 102 may be configured
to reduce,
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compensate for, or eliminate aberrations produced by the optic itself, the
cornea, the eye, or
the combination of the optic with the cornea or eye. For example, at least one
of the surfaces
of the optic 102 may be aspheric and configured to reduce, compensate for, or
eliminate a
spherical aberration (e.g., have an negative spherical aberration that
reduces, compensates
for, or eliminates a positive spherical aberration of a cornea or eye).
Additionally or
alternatively, the materials and/or a diffraction grating on one or both
surfaces of the optic
102 may be selected to reduce, compensate for, or eliminate chromatic
aberration (e.g.,
produced by the optic itself, the cornea, the eye, or the combination of the
optic with the
cornea or eye).
Referring to FIGS. 7-9, in certain embodiments, an intraocular lens 200
comprises an
optic 202 including an extended focus mask that is in the form of a phase-
affecting, non-
diffractive mask 220. Examples of such non-diffractive masks are disclosed by
Zalevsky in
USPN 7,061,693, which is herein incorporated by reference in its entirety. The
optic 202 has
a clear aperture 212 that is disposed about a central axis or optical axis OA.
The optic 202
includes an anterior surface 204 having an anterior shape or base curvature
214 and an
opposing posterior surface 206 having a posterior shape or base curvature 216.
The non-
diffractive mask 220 is disposed on, added to, or combined with the posterior
shape 216 so as
to increase a depth of focus of at least one focus of the optic 202. The optic
202 may include
a multifocal element or pattern 218 that is disposed on, added to, or combined
with the
posterior shape 216. The first and second surfaces 204, 206 together provide a
base power
and an add power.
The phase-affecting, non-diffractive mask is configured in accordance with the
parameters of the optic 202, i.e., its effective aperture and optionally also
the optical power
distribution and/or focal length. The mask 220 may be implemented integral
with the optic
202, for example, as a pattern on the lens surface. Alternatively, the mask
220 may be a
separate element attached to the optic 202 or located close thereto.
Generally, the mask 220
is configured as a phase-only binary mask; however, the mask 220 may be
configured as a
phase and amplitude mask.
The mask 220 may be configured to define at least one spatially low frequency
transition region, and the mask 220, together with the optic 202, define a
predetermined
pattern of spaced-apart optically or substantially optically transparent
features differently
affecting the phase of light passing therethrough. The pattern of the mask 220
is thus formed
by one or more transition regions along the posterior surface 206. The
transition regions are
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it-phase transitions for a certain wavelength for which the mask 220 is
designed. The
arrangement of these transition regions (positions within the posterior
surface 206) is
determined by the effective aperture of the given imaging optic 202 (and
possibly also optical
power of the lens) so as to increase a defocused Optical Transfer Function
(OTF) of the
intraocular lens 200. To this end, the pattern of the mask 220 may be
configured to generate
a desired phase interference relation between light portions passing through
different regions
of the optic 202.
The mask 220 may be implemented as a surface relief on the imaging lens, as
illustrated in FIG. 8. Alternately, the mask 220 may be implemented as a
pattern of regions
made of a second material than that of the optic 202 base material. The second
material is
generally transparent or substantially transparent, and may have a refractive
index that is
different from that of the optic 202. The second material may be disposed on
selective
spaced-apart regions of the surface 206. Alternatively, the pattern may be
machined or
molded into the surface 206.
In the illustrated embodiment, the non-diffractive mask 220 comprises an
annular
transition region 222. It will be appreciated that other configurations of one
or more
transition regions may be additionally or alternatively used. For example,
referring to FIGS.
10 and 11, masks 220' and 220" comprise linear transition regions 222' and
222". In the
example of FIG. 10, the mask 220 comprises a grid formed by two mutually
perpendicular
pairs of bars. In the example of FIG. 11, the mask 220 comprises a mask formed
by a two-
dimensional array of basic grid-elements. For example, the transition regions
along the bar
line may be it-phase transitions and the regions of intersection between the
bars may be zero-
phase transitions. Other patterns are anticipated, for example, combinations
of linear,
circular, and/or arcuate pattern elements. The pattern of the mask 220 may and
may not be
symmetrical relative to the center of the lens. For example, the four it-phase
bars, two
vertical (along Y-axis) and two horizontal (along X-axis) bars, that are
illustrated in FIG. 10,
may be shifted transversally along the x-y plane to be not centered around the
center of the
lens. The pattern of the mask 220 may be configured to define microstructures
inside the
phase transition region (e.g., inside the it-phase transition ring of FIG. 9),
namely, each phase
transition region may be of a variable spatially low frequency of phase
transition such as for
example it/2, it, and so forth.
In certain embodiments, an improved or optimized mask 220 contour for the
optic
202 is obtained by a solving algorithm, for example as is described by
Zalevsky in USPN
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7,061,693. In such embodiments, the mask 220 may be designed to increase or
maximize a
defocused OTF of an ocular imaging system, by generating invariance to
quadratic phase
factor (which factor is generated when the image is defocused and multiplies
the CTF of the
imaging lens).
The optic 202 and the non-diffractive mask 220 may incorporate, where
appropriate,
any of the elements discussed above with regard to the optics 102, 102' or the
masks 120,
120'.
In certain embodiments, an optic comprises an extended focus pattern or mask
comprising a surface profile like those taught in USPN's 6,126,286 (Portney),
6,923,539
(Simpson et al.), 7,287,852 (Fiala), or 7,293,873 (Dai)., or U.S. Patent
Application Number
2006/0116763 (Simpson), all of which are herein incorporated by reference.
Such devices
and means of extending depth of focus may replace or supplement those already
discussed
above herein (e.g., replacing or supplementing masks 102, 102', 202). For
example, a pattern
of surface deviations may be superimposed on at least one of the base
curvatures or shapes
114, 116 of the optic 102, so as to modulate the topography of at least one of
the surfaces
104, 106 in a range of about -0.5 microns to about +0.5, as disclosed in USPN
6,923,539.
Referring to FIGS. 12-14, an accommodating intraocular lens 300 comprises an
optic
302 having a clear aperture 312 disposed about an optical axis OA, the optic
including an
anterior surface 304 and a posterior surface 306. The intraocular lens 300
also comprises a
positioning member 308, wherein the positioning member 308 is generally
configured to
provide accommodative action by transferring an ocular force to the optic 302.
In the
illustrated embodiment, the ocular force deforms the optic 302 which is
preferably made of a
relatively soft material, for example, having a modulus of elasticity of less
than 200 kPa, 100
kPa, or 50 kPa. The optic thereby changes shape and optical power in response
to the ocular
force, for example, by changing the radius of curvature of at least one of the
surfaces 304,
306. Alternatively or additionally, the intraocular lens 300 may be configured
to provide
accommodative action by moving the optic 302 along the axis OA in response to
an ocular
force, especially in relation to one or more other stationary or moving
optics.
The optic 302 comprises an extended focus pattern or mask 320 that is disposed
on,
added to, or combined with a base curvature or shape of the anterior surface
304, the
extended focus mask 320 being configured to provide an extended depth of focus
for a focus
of the optic 300. The intraocular lens 300 has a depth of focus, when
illuminated by a light
source over the entire clear aperture, that is greater than a depth of focus
of a reference optic
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without the mask, the reference optic having a base power, an add power, and a
clear aperture
that are equal or substantially equal to that of the intraocular lens 300.
The ocular force to the intraocular lens 300 may be provided directly by the
capsular
bag into which the intraocular lens 300 is place. Alternatively, the
positioning member 308
may be configured so that the ocular force used to deform the optic 302 is
provided more
directly by the ciliary muscle and/or the zonules, for example, by removing
the capsular bag
or placing the intraocular lens 300 in front of the capsular bag. In any case,
the intraocular
lens 300 is generally configured to provide a predetermined amount of
accommodation when
the ciliary muscle contracts and/or relaxes and with an ocular force of less
than 20 grams
force , less than 10 grams force, or even less than 5 grams force.
The intraocular lens 300 is configured to have a predetermined ocular power
when in
a reference state, for example, in which no or substantially no external
forces on the
intraocular lens 300 expect for that of gravity. In some embodiments, while
there is no or
substantially no external force on the intraocular lens 300 when in the
reference state, the
intraocular lens 300 may experience internal forces, for example, produced
between the optic
302 and the positioning member 308 due to a pre-stress introduced during
fabrication. The
optical power of the intraocular lens 300 when in the reference state may be
selected to
provide near vision (an accommodative bias), distant vision (a
disaccommodative bias), or
intermediate vision.
It will be appreciated that variations of the structure illustrated in FIGS.
12-14 may be
used. For example, the extended focus mask 320 may be disposed on the
posterior surface
306. Additionally, at least one of the surfaces 304, 306 may incorporate a
multifocal profile
(diffractive or refractive) on the same or opposite surface containing the
mask 320. In
general, the optic 302 and the mask 320 may incorporate, where appropriate,
any of the
elements discussed above with regard to the optics 102, 102', 202 or the masks
120, 120',
220. For example, at least one of the surfaces of the optic 302 may comprise a
diffractive or
refractive multifocal profile or mask with a maximum add power of at least 1.5
Diopters or
2.0 Diopters, for example to enhance or compensate for a sufficient ocular
force to provide a
desired amount of accommodative axial movement and/or deformation.
The extended focus mask 320 in the illustrated embodiment comprises a
diffraction
mask similar or equivalent to the extended focus pattern or mask 120 or the
low-add
diffractive mask 120'. However, the mask 320 in the illustrated embodiment may
be
replaced or combined with any profile or mask suitable for providing an
extended depth of
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focus, for example, like the phase-affecting, non-diffractive mask 220 or of
one or more of
the designs disclosed in the prior art publication cited above herein.
Embodiments of the present invention may also be incorporated to extend or
enhance
the depth of focus of various prior art accommodating intraocular lens that
use a deformable
optic and/or axial travel, such as those disclosed in USPN 7,048,760
(Cumming), 6,846,326
(Zadno-Azizi et al.), or 6,488,708 (Sarfarazi), or U.S. Patent Application
Publication Number
2004/0111153 (Woods et al.) or 2007/0129803 (Cumming et al.), or U.S. Patent
Application
Numbers 11/618,325 (Brady et al.), or 11/618,411 (Brady et al.), all of which
are herein
incorporated by reference in their entirety. The intraocular lens 300 is
generally configured
to change the optical power of the optic 302 by at least about one Diopter,
preferably by at
least 2 Diopter, 3 Diopter, or 4 Diopters.
For example, in certain embodiments, an accommodating intraocular lens
comprises a
single flexible optic having anterior and posterior sides, similar to that
disclosed in USPN
7,048,760. In such embodiments, the intraocular lens may further comprise at
least two
portions extending from the optic, the portions having hinged inner ends
adjacent the optic
and outer ends distal to the optic, the outer ends being movable anteriorly
and posteriorly
relative to the optic, and the portions having at least one flexible fixation
finger at the outer
ends of the portions.
In certain embodiments, an accommodating intraocular lens is configured to
fill the
capsular bag, for example, as disclosed in U.S. Patent Application Publication
Number
2004/0111153, or U.S. Patent Application Numbers 11/618,325 or 11/618,411. In
such
embodiments, the accommodating intraocular lens may comprise a positioning
member
including opposing anterior and posterior arcuate segments and a plurality of
circumferentially spaced legs each having a first end joined to the optic and
a second end
joined to at least one of the arcuate segments. In other embodiments, an
accommodating
intraocular lens comprises two or more separate optical elements, for example,
as disclosed
in USPN's 6,846,326 or 6,488,708. Such a configuration may beneficially
provide a
relatively large amount of accommodation with a relatively small amount of
axial motion
between the two separate optical elements.
The description of the invention and its applications as set forth herein is
illustrative
and is not intended to limit the scope of the invention. Variations and
modifications of the
embodiments disclosed herein are possible, and practical alternatives to and
equivalents of
the various elements of the embodiments would be understood to those of
ordinary skill in
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the art upon study of this patent document. These and other variations and
modifications of
the embodiments disclosed herein may be made without departing from the scope
and spirit
of the invention.
22
