How patients and your practice win with presbyopic
JUSTIN HOLT, O.D. AND DANE DANSIE, O.D.
more and more Baby Boomers approaching cataract age, annual cataract surgery volumes
are expected to increase dramatically within the coming years. This is relevant
for optometrists as well as surgeons, of course, as we will comanage many of these
cases. What's good news for these patients is the development of new multifocal
or "presbyopia-correcting" IOLs that give patients both near and distance vision.
Our patients now have three very different IOLs to choose from, depending on their
visual needs and lifestyle. Presently, the FDA has approved these for use in the
United States: the ReZoom (Advanced Medical Optics), the ReSTOR (Alcon) and the
crystalens (eyeonics). Here's what you should know about them.
crystalens provides accommodation up to 3.33D.
Because a phakic lens is about 5mm thick and an IOL is about 1mm
thick, early researchers hypothesized that there may be space within which an IOL
could move, thus providing a level of accommodation. The crystalens is designed
to provide accommodation up to 3.33D by dynamic retinoscopy. The FDA approved the
IOL in November 2003, and it's currently the only truly accommodating (rather than
pseudo-accommodating) IOL available on the market.
The lens features a hinged plate-haptic with a relatively small
4.5mm silicone optic. When the patient attempts to accommodate, the ciliary body
contracts and the tension on the capsular bag diminishes. The increased pressure
within the vitreous body then allows the lens to vault forward at the hinges, resulting
in near focus.
One of the advantages of the crystalens is that the optic is monofocal.
Research measuring contrast sensitivity indicates that multifocal design intraocular
implants can slightly decrease the level of contrast sensitivity that a patient
experiences after cataract surgery. With the monofocal single optic design of the
crystalens, patients can maintain levels of contrast sensitivity and gain a slightly
better quality of vision. The limited excursion of the lens optic during accommodation
provides an average amplitude of 1.00D to 1.50D.
Concurrent with recent
FDA approvals of these new multifocal IOLs, the Centers for Medicare and Medicaid
Services (CMS) issued a landmark ruling on May 3, 2005. It permits cataract patients
to pay the difference for these IOLs, beyond what Medicare and insurance companies
pay for standard monofocal lenses, and upgrade to new "premium" lenses.
Prior to this ruling, Medicare
required cataract patients who wanted these new implants to pay out-of-pocket expenses
for the surgeon fee, facility fee and lens fee; or just receive a monofocal lens
that Medicare would pay for. Now, Medicare will continue to pay the standard fee
for cataract surgery with a monofocal IOL and the patient will then pay for the
presbyopia-correcting lens, in effect sharing the cost.
The ReZoom IOL is a second-generation, acrylic, three-piece lens
with a 6mm optic. The FDA approved it in March 2005. The lens is built on the platform
of the company's first-generation multifocal IOL, the Array. Due to a high volume
of patient complaints of dysphotopsia, the Array never gained wide popularity. The
ReZoom addresses the Array's shortcomings with the incorporation of the company's
"balanced view optics" technology.
It utilizes five optical zones proportioned to provide good visual
function across a range of distances in varying light conditions. The center of
the optic is distance-dominant; the second zone provides near-dominant vision.
The other four concentric refractive zones of the lens create
true multifocal vision. Zones 1, 3, and 5 are distance-dominant, while zones 2 and
4 are near dominant.
AMO created an aspheric transition between each zone, which it
says is designed to provide the balanced intermediate vision critical for many patients'
everyday activities. This is particularly useful to patients spending a great deal
of time at the computer. In addition to this, AMO has altered the size of the rings
in proportion to those used in the design of the Array lens.
These modifications have greatly decreased the degree of dysphotopsia,
though they have not eliminated it completely. The ReZoom typically provides very
good distance and intermediate vision, but patients will have to use reading glasses
occasionally for very small print. Typical near vision tends to be around 20/30.
Though the add measures 3.50D, the effective add at the corneal plane ends up at
The AcrySof ReSTOR received FDA approval in March 2005. The lens
is an apodized diffractive optic IOL that uses a mathematically derived image enhancement
algorithm called apodization. Apodization gradually blends the diffractive step
heights, effectively managing the light that's delivered to the retina. Thus it
improves vision quality while minimizing visual disturbances. The factors that afford
enhanced contrast and image quality improvement are balanced use of optical power,
number of diffractive rings, step height and ring width.
The ReSTOR features 12 zones and gradually
blends diffractive step heights.
IOL has 12 diffractive steps, with the first step height equaling 1.3microns. It
tapers to a 0.2micron 12th step, effectively delivering slightly over 3.00D at the
spectacle plane. In fact, clinical studies indicate that 80% of the individuals
in FDA trials did not need to wear eyeglasses at all after they received the ReSTOR
While this lens clearly provides better near vision than other
presbyopia-correcting lenses, there may be some trade-offs. Because the effective
add is about 3.00D, patients may need to hold things closer, approximately 31cm,
to read them than they were accustomed to with their bifocals prior to the surgery.
Also, patients may find that their intermediate vision is not as clear due to the
closer working distance.
The ReZoom and the ReSTOR are very different from the crystalens.
While they do not move axially within the eye, they provide pseudo-accommodative
vision. These lenses are based on refractive and apodized diffractive optics, respectively.
Light from multiple focal planes is simultaneously focused on the retina. These
multiple planes will cause light scatter and often create halos at night.
This will require some neuroadaptation on the patient's part.
Similar to the way patients adapt to monovision, this can take anywhere from a few
minutes to six months. The glare and halos can alarm patients if you don't educate
them about the possibility before surgery.
ReZoom utilizes five zones to provide good visual function across a range of distances.
Even if you do educate them, patients can occasionally be so concerned
with glare and halos at night that they may wonder if they should have elected to
receive a monofocal implant. In these cases, I use a -2.50D loose lens over each
eye to show them what their vision would be at near if they had chosen a monofocal
lens. This often reassures them that they made the right choice and that the small
amount of glare at night isn't as bothersome as their near vision would be with
a monofocal lens. Again, I tell these patients that any glare they see initially
will get better with time. I explain that it's analogous to putting on a new watch:
Initially you will feel it all the time; then, eventually, you don't notice it at
What to expect post-op
Postoperatively, the management of these patients remains largely
unchanged from that of a traditional monofocal implant patient. However, there are
a few exceptions. Despite preoperative discussion of the likelihood of initial halos
and glare, some patients are very conscious of them during the neuroadaptation period.
Some doctors have found Alphagan P (brimonidine tartrate ophthalmic solution 0.15%,
Allergan) helpful in decreasing patient symptoms of dysphotopsia, due to its mild
miotic effect. Antireflective plano glasses for night driving have also proven beneficial.
These patients can also be very symptomatic to small degrees of
dry eye and associated superficial punctate keratopathy (SPK). You should treat
even minor degrees of surface disease aggressively prior to surgery. In these cases,
preoperative Restasis (cyclosporine, Allergan) has been used successfully and the
surgeon and comanaging O.D. should consider it for any patient with even minuscule
amounts of SPK.
Mild posterior capsule opacification also has a much greater impact
on vision for these patients vs. a traditional monofocal IOL patient. Surgeons subsequently
may have a much lower threshold for performing a capsulotomy. Residual cylinder
beyond 0.50D is also very poorly tolerated. Often one or more limbal relaxing incisions
(LRI), subsequent LASIK, mini-radial keratotomy or a couple of conductive keratoplasty
spots can alleviate what seems to be very little correction.
Get the best result
There are subtle trade-offs for each design and no single lens
can guarantee perfect vision at distance, intermediate and near. Many surgeons have
developed a process of IOL "staging" to find the best results for their patients.
The surgeon will implant one eye, and then based on the outcome, decide what changes
need to be made, if any, for the fellow eye.
There is now a trend among cataract surgeons to use these three
multifocal IOLs in a complementary fashion. For instance, a patient may have a ReZoom
implanted in the first eye and be happy with his or her vision at near, far and
intermediate. The surgeon may then implant another ReZoom lens in the second eye.
if that patient complains a few weeks postoperatively that his or her near vision
isn't as good as necessary, but distance is great, the surgeon may consider a ReSTOR
for the second eye. If the patient does a lot of night driving, the surgeon might
consider bilateral crystalens implants, knowing that the patient may still require
reading glasses after surgery. (Editor's note: Alcon has cautioned against mixing
and matching IOLs because the ReSTOR lens received FDA approval as a binocular implant.)
Accommodation on the Horizon
The 1CU Accommodative IOL
(HumanOptics), the Kellan Tetraflex (Lenstec), the SmartIOL (Medennium) and the
BioComFold 43E lens (Morcher) are all investigational lenses that function with
a similar accommodative movement to that of the crystalens. The Synchrony IOL (Visiogen)
and the Sarfarazi Elliptical accommodating IOL (Bausch & Lomb) also are dynamic
IOLs, but incorporate a dual-optic design to increase accommodative amplitude, while
requiring very little lens movement. They all are currently undergoing clinical
trials in Europe and the United States.
They'll only get better
The best candidates for multifocal IOLs are well motivated with
a realistic understanding of expectations. Preoperative discussion of possible postoperative
glare and halos is imperative. Fortunately, these symptoms usually fade with time.
Although some patients may still need to wear a weak near correction for tasks such
as reading the phone book, etc., the vast majority of their needs at near can be
addressed through the lens designs we've discussed.
With the next generation of presbyopia-correction IOLs on the
horizon, we can minimize side effects even further, while improving patients' visual
quality at all distances.
References available upon request.
Holt is in group practice at the Mount Ogden Eye Center and Bountiful
Hills Eye Center in Utah. He completed a residency at the University of Utah Moran
Eye Center and Veterans Hospital.
Dr. Dansie practices at the Mount Ogden Eye Center. He is also on staff
at the Salt Lake Veterans Hospital and is clinical adjunct faculty for several optometry
Optometric Management, Issue: July 2006