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Intraocular Lenses (IOLs):
New Advances Including
AcrySof ReStor, ReZoom &
Crystalens
Intraocular lenses, or IOLs,
are the artificial lenses
that replace the eye's
natural lens that is removed
during cataract surgery.
IOLs have been around since
the mid-1960s, though the
first FDA approval for one
occurred in 1981. Before
that, if you had cataracts
removed, you had to wear
very thick eyeglasses or
special contact lenses in
order to see afterward,
since the natural lens that
had been removed wasn't
replaced with anything.
Until recently, only
cataract surgeons - not
their patients - weighed the
risks and benefits of
various IOLs. The surgeons'
discussions focused on the
surgical technique (clear
cornea, small incision,
etc.) and the physical
design of the lenses
(one-piece vs. multipiece,
acrylic vs. silicone) and
how that design affected
insertion, positioning and
healing.
Good vision after cataract
surgery was another
important consideration, but
now that new IOLs have been
introduced that solve more
vision problems than ever,
cataract surgeons have more
to consider before choosing
IOLs for their patients'
visual needs. Cataract
patients are becoming more
involved in the choice as
well.
If you or someone you know
will be undergoing cataract
surgery, read the following
summary of the most recently
developed IOLs.
Multifocal IOLs and
Accommodating IOLs:
AcrySof ReStor, ReZoom and
Crystalens
Traditional IOLs are
monofocal, meaning they
offer vision at one distance
only (far, intermediate or
near). They are definitely
an improvement over the
cataractous lens that is
replaced during surgery,
which provides only cloudy,
blurred vision at any
distance. But traditional
IOLs mean that you must wear
eyeglasses or contact lenses
in order to read, use a
computer or view objects in
the middle distance,
especially if you are
already experiencing
presbyopia before cataract
surgery.
The new multifocal and
accommodating IOLs offer the
possibility of seeing well
at more than one distance,
without glasses or contacts.
Here are a few examples
(note: this is not a
complete list):
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ReStor |
ReZoom |
AcrySof ReStor (Alcon)
uses apodized diffractive
technology - a design that
responds to how wide or
small the eye's pupil might
be - to provide near,
intermediate and distance
vision. In early 2007, an
aspheric version of the
AcrySof Restor received FDA
approval. Aspheric lenses,
because they are somewhat
flat near the edges, are
thought to improve contrast
sensitivity and provide
better night vision than
other types of multifocal
IOLs.
Clinical studies used to
support the March 2005 FDA
approval showed that 80
percent of people who
received the lens didn't use
glasses for any activities
after their cataract
surgery; 84 percent who
received the lens in both
eyes had distance vision of
20/25 or better, with near
vision of 20/32 or better.
ReZoom (Advanced Medical
Optics) is a multifocal
refractive IOL that
distributes light over five
optical zones to provide
near, intermediate and
distance vision. The first
version of this multifocal
IOL was brought to the U.S.
market in the late 1990s;
the ReZoom is the
second-generation version
and was FDA-approved in
March 2005
In a European study of 215
patients, 93 percent of
ReZoom recipients reported
never or only occasionally
needing glasses.
Crystalens (Bausch &
Lomb) gained FDA
approval in late 2003, when
the IOL was marketed by
eyeonics. Bausch & Lomb
acquired Crystalens in early
2008, and a newer version of
the IOL, known as Crystalens
HD, was FDA-approved in late
June 2008. Crystalens was
designed to restore the
eye's accommodation ability,
which is gradually reduced
as presbyopia progresses. In
FDA studies, about 80
percent of people who
received the Crystalens HD
could see at J2 or better
(near vision equivalent of
20/20) after four months -
superior to standard IOLs.
As with multifocal IOLs,
distance vision with the
Crystalens tends to be very
good.
Crystalens is designed to
move within the eye, to
provide focusing at all
distances.
"Accommodation" is the
ability of the eyes to
change focus from near to
far, far to near and all
distances in between. With
presbyopia, which usually
begins at around age 40, the
eye muscle that accomplishes
this accommodation - the
ciliary muscle - has more
difficulty in doing its job,
because the eye's lens is
becoming less flexible. The
ciliary muscle contracts in
its effort to move the lens
forward, bending it slightly
for closeup focusing; but
the lens resists because it
is not as flexible as it was
when the eye was younger.
Since Crystalens has hinges
on both sides of the IOL, it
can be moved more easily by
the ciliary muscle, allowing
the eye to focus more
naturally at a greater range
of distances than
traditional IOLs. So far,
Crystalens is the only
accommodating IOL that has
been approved by the FDA,
though others are in
development.
Synchrony (Visiogen Inc.)
is another accommodating IOL
that was not FDA-approved as
of mid-2008, although
company officials have
commented that they expect
approval possibly in 2009.
The lens has regulatory
approval in Europe and other
locations. This dual-optic
IOL has shown promising
early results. The Journal
of Cataract and Refractive
Surgery in January 2007
reported results of a small
study showing that the IOL
demonstrated ability to
restore focus at a range of
1.00 to 5.00 diopters, about
twice that of a control
group.
It's important to note that
you can't be 100 percent
certain of seeing well
without eyeglasses or
contact lenses after
cataract surgery, even if
your eyes have received
multifocal or accommodating
IOLs. Some of the factors
that can decrease
satisfaction with these IOLs
include pre-existing
astigmatism, incorrect
positioning of the IOLs in
the eye and nighttime halos
that some patients have
experienced.
But even with these risks,
these new IOLs do provide
the probability of good
vision without total
dependence on eyeglasses or
contacts. You may even
achieve good vision without
using these aids at all.
Monovision
If your cataract surgery
involves both eyes, you
might consider monovision.
This involves implanting an
IOL in one eye that provides
near vision and an IOL in
the other eye that provides
distance vision. Usually
people can adjust to this,
but if you can't, your
vision may be blurred at
both near and far. Another
problem is that depth
perception may decrease
because there is less
binocular vision - your eyes
aren't working together as
they once did.
The people who do best with
this method are those who
are already used to
monovision with contact
lenses, which is a common
way of correcting
presbyopia. If you can't
adjust to monovision after
your cataract surgery, you
may wish you had tried a
multifocal or accommodating
IOL instead. Some surgeons
will trial-fit a cataract
patient in monovision
contact lenses prior to
inserting monovision IOLs.
Toric IOLs for Astigmatism
Toric IOLs are designed to
correct astigmatism. The
Staar Surgical Intraocular
Lens was the first toric IOL
available in the United
States; it was FDA-approved
in 1998. The Staar toric IOL
comes in a full range of
distance vision powers, in
two versions: one corrects
up to 2.00 diopters and the
other corrects up to 3.50
diopters of astigmatism.
The FDA approved the AcrySof
Toric IOL by Alcon in
September 2005.
Most surgeons who treat
astigmatism in their
cataract patients tend to
use astigmatic keratotomy
(AK) or limbal relaxing
incisions, which involve
making incisions in the
cornea. But in addition to
or even instead of corneal
astigmatism, some people may
have lenticular astigmatism,
caused by irregularity in
the shape of the natural
lens capsule. This can be
corrected with a toric IOL.
Risks include poor vision
due to the lens rotating out
of position, with the
possibility of further
surgery to reposition or
replace the IOL.
Aspheric IOLs
Traditional IOLs are
spherical, meaning the front
surface is curved. Aspheric
IOLs, first launched by
Bausch & Lomb in 2004, are
slightly flatter in the
periphery and are designed
to provide better contrast
sensitivity. The Bausch &
Lomb offering is called the
SofPort Advanced Optics IOL.
Aspheric IOLs are available
also from Alcon, including
the AcrySof SN60WF that
includes the blue
light-blocking feature
discussed below and the
aspheric version of AcrySof
ReStor. Advanced Medical
Optics offers the Tecnis
Z9000.
There is some debate as to
how long this contrast
sensitivity benefit can last
in older patients. After the
period of cloudy, blurred
vision that most cataract
patients must endure before
their surgery, improved
contrast sensitivity is
indeed a blessing. But since
the ganglion cells of the
retina are a major
determinant of contrast
sensitivity and we gradually
lose these cells as we age,
over time the contrast
sensitivity will decrease as
well. However, younger
people are undergoing
cataract surgery now, and
this group is likely to have
more and healthier ganglion
cells. So they would be able
to enjoy the better contrast
sensitivity for a longer
time.
In May 2004, the Tecnis
Z9000 aspheric IOL received
FDA approval for new
labeling that says it can
reduce postoperative
spherical aberrations and
therefore improve the
ability to see in varying
light conditions such as
rain, snow, fog, twilight
and nighttime darkness. The
approval was based on a
clinical study that measured
night driving simulator
performance in cataract
surgery patients. According
to manufacturer Advanced
Medical Optics, the Tecnis
IOL was designed using
wavefront analysis of human
corneas. Wavefront is the
same tool that is used to
plan personalized custom
LASIK procedures to reduce
higher-order aberrations in
the visual system.
In March 2007, Bausch &
Lomb's SofPort Advanced
Optics IOL received a "new
technology" designation from
the Centers for Medicare and
Medicaid Services, enabling
extra reimbursement of $50
per lens because of
demonstrated ability to
reduce spherical
aberrations. AMO's Tecnis
IOL received a similar
designation allowing extra
Medicare reimbursement in
February 2006.
Blue Light-Filtering IOLs
AcrySof Natural filters both
ultraviolet (UV) and
high-energy blue light, both
of which are present in
natural and artificially
produced light. UV rays have
long been suspected to cause
cataracts and other vision
problems, and many IOLs
filter them out just as your
natural crystalline lens
does before its removal in
cataract surgery. Blue
light, which ranges from 400
nm to 500 nm in the visible
light spectrum, may cause
retinal damage and play a
role in the onset of age
related macular
degeneration.
The AcrySof Natural is
colored a transparent yellow
in order to filter the blue
light; actually, the color
is similar to that of the
natural crystalline lens, so
the idea behind the AcrySof
Natural is to re-add the
protection against blue
light that is lost when the
natural lens is removed.
According to Alcon, the
manufacturer, the yellow
tint doesn't alter the color
of your environment or your
vision quality.
"Piggyback" IOLs
If you have a less than
optimal result from the
original intraocular lens
used in your cataract
surgery, your eye surgeon
might discuss with you the
option of inserting an
additional lens over the top
of the one you have
currently.
This approach, known as a
"piggyback lens," likely can
improve vision and may be
considered safer than
removing and replacing the
existing lens.
If you require extremely
high degrees of vision
correction, such as for
severe myopia or
astigmatism, your eye
surgeon might advise
combining the strengths of
two intraocular lenses in
one eye by using the
"piggyback" approach.
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