HEADLINE: Developing Your Premium IOL Skill Set
DECK: The need for careful patient selection and communication makes
success an art as well as a science.
By W. Andrew Maxwell, MD, PhD
Since about the time you began medical school, those of us who were already
established in practice have been undergoing an education of our own. We watched
with interest the development of accommodating and multifocal IOLs designed to
provide a range of vision to our cataract surgery patients. We followed the relevant
studies and FDA clinical trials, or participated in them as I did, and began offering
the lenses to our patients.
As we gained experience, we learned how the various lens designs, including
subsequent upgrades, perform in the general population. We learned that each lens
has its own set of advantages and disadvantages when it comes to the range of
quality vision that can be achieved and the potential for postoperative visual
disturbances. Most importantly, our collective experience confirmed that careful
patient selection and communication remain absolutely necessary for using the
lenses successfully.
Now that the presbyopia-correcting category of IOLs has become a
permanent part of cataract surgical care, it’s your turn to navigate the learning
curve. You’ll need to familiarize yourself with the individual lenses’ optical
characteristics, understand what those characteristics mean for patients’ vision in
the real world, and select candidates appropriately. You’ll also need to bear in
mind that a patient can’t be deemed a good candidate unless you’ve thoroughly and
honestly explained the potential drawbacks of the lenses along with the benefits.
Bench Testing Provides Guidance
Reviewing published results from optical bench testing is a good place to start.
Evaluations utilizing model eyes, such as modulation transfer function (MTF) and
U.S. Air Force Resolution Target (AFT) testing, provide valuable information
about the optical performance of IOLs. MTF is an objective assessment of the
image contrast degradation of IOLs at different spatial frequencies. Results have
been shown to relate closely to patients’ subjective quality of contrast sensitivity,
including in mesopic conditions. In AFT testing, paired, three-bar target sets are
photographed through IOLs, simulating the vergence in the human eye and
providing a qualitative assessment of the IOLs’ resolution efficiency.
For example, a study I recently participated in compared six IOLs using MTF
and AFT testing.[1] Three spherical designs (Crystalens AT-50SE, ReZoom NXG1
and AcrySof ReSTOR SA60D3) and three aspheric designs (AcrySof IQ ReSTOR
SN6AD3, Acri.Lisa 366D and Tecnis ZM900) were included in the study. The
AcrySof IQ ReSTOR aspheric IOL had the highest MTF values of all the lenses at
all spatial frequencies. At the dominant frequency that approximately corresponds
to 20/20 vision (100 line pairs per millimeter), its performance was double that of
the ReZoom and Tecnis lenses. The AcrySof IQ ReSTOR aspheric IOL also
produced the image with the highest resolution on the AFT test.
These results indicate that compared to the other lenses studied, the AcrySof
IQ ReSTOR IOL is of superior optical quality for distance vision. In addition, the
results suggest that the correction of spherical aberration with aspheric lens design
is an important aspect of good optical quality. The poorer performance of other
IOLs in the study may be due to their spherical design. The fact that the AcrySof
IQ ReSTOR IOL outperformed other aspheric lenses may be attributed to its
unique apodized diffractive design.
Apodization manages the distribution of light to the retina by gradually
reducing and blending the diffractive step heights from the center of the IOL
toward the periphery. This reduces light scatter, aberrations and visual disturbances,
which means vision is crisper compared with other lens designs. Apodization is
particularly helpful in low light. Also, in contrast to lenses with fully diffractive
optics, the AcrySof IQ ReSTOR IOL is refractive in the periphery. The refractive
region of the optic is dedicated to distance vision, directing light to a distance focal
point for larger pupil diameter, such as the 5.0-mm aperture that was used in the
optical bench study. This serves to preserve contrast sensitivity and produce fewer
visual disturbances than lenses with fully diffractive optics.
A favorable performance in optical bench tests doesn’t necessarily guarantee
an IOL will provide excellent real-world vision, but the tests provide us with solid
guidance on what our patients can expect. My personal experience has mirrored the
findings of this particular study. The addition of asphericity to the first-generation
AcrySof ReSTOR (SA60D3), which resulted in the 2007 release of the AcrySof IQ
ReSTOR (SN6AD3), improved clinical outcomes for my patients.
Review Clinical Trial Results
Before beginning to implant presbyopia-correcting IOLs, you should also
review the results of the clinical trials that led to each lens’ FDA approval. I
participated in the randomized multicenter clinical trial that evaluated the most
recently introduced lens in the ReSTOR line, the AcrySof IQ ReSTOR IOL with
+3.0D add power.[2] This lens, model SN6AD1, is the same as the SN6AD3
except the add power is +3.0D rather than +4.0D (Figures 1 and 2). The new lens
was designed to offer an additional choice of add power that would move the best
distance for near vision 6-7 cm farther out and provide patients with better depth of
focus and intermediate vision compared with the +4.0D add power lens. The
clinical trial was designed to determine whether the +3.0D add power achieved
these goals without compromising overall quality of vision.
In the trial, cataract surgery patients were randomly assigned to bilateral
implantation of either the +3.0D or the +4.0D IOL. Of the 279 patients enrolled,
272 completed the 6-month follow-up examination. According to the results, the
two IOLs provided equivalent near and distance visual acuity, but the mean best
distance for uncorrected near visual acuity was 31 cm in the +4.0D group and 37
cm in the +3.0D group (an increase of approximately 2.5 in.). Also, mean
uncorrected intermediate visual acuity at 50 cm and 60 cm was approximately 1
Snellen line better in the +3.0 group than in the +4.0 group, a clinically significant
difference. Mean distance-corrected intermediate visual acuity in the +3.0D group
was clinically and statistically significantly better than in the +4.0 D group at 50
cm, 60 cm and 70 cm.
Binocular defocus curves derived from the trial (Figure 3) also illustrate the
differences in how the two lenses function. The curve for the +3.0D group showed
a mean binocular intermediate visual acuity of 20/32 or better, which was 1-2
Snellen lines better than in the +4.0D group. Also, patients in the +3.0D group had
intermediate visual acuity of 20/25 or better from 40-70 cm as opposed to 25-40
cm in the +4.0D group.
Based on the results of this trial, I expected the AcrySof IQ ReSTOR IOL
+3.0D would be the lens that would allow me to meet the needs of the largest
number of patients who are interested in a presbyopia-correcting option. Once I
began using the lens in my own practice, that expectation was confirmed.
Currently, it is the IOL I recommend most in this category, and patient satisfaction
is high, just as it was in the trial. (Figure 4)
Learn from the Experiences of Other Surgeons
Understanding the technical characteristics of each of the presbyopia-
correcting IOLs and how they performed in clinical trials will help you to choose
the best option for meeting each of your patients’ vision goals. It will also help you
to determine whether or not each patient is a good candidate for one of the lenses
based on those goals. (See “When a Presbyopia-Correcting IOL May Not Be the
Best Option” below.)
Here are some pointers for choosing the right candidates and communicating
with them effectively so their expectations are met and they’re satisfied with the
care you’ve provided:
• Carefully evaluate overall ocular health. Patients should have minimal
astigmatism and be free of any macular problems or ocular surface problems such
as dry eye. Otherwise, their eyes aren’t capable of achieving the full visual
potential the lenses can provide. For example, even subtle changes in the RPE that
could indicate early AMD should be evaluated further with OCT before you
proceed. In my practice, I also measure patients’ visual potential with a retinal
acuity meter.
Each lens manufacturers’ “Directions for Use” provides detailed guidelines
about preexisting ocular conditions that are cause for concern. They also list
potential intra-operative complications that could make implantation risky.
• Talk with patients about their lifestyles. Know their visual priorities and
match those with the right lens. For example, while the AcrySof IQ ReSTOR IOL
+3.0D is the best option for most patients, especially those who use a computer, the
AcrySof IQ ReSTOR IOL +4.0D may be better for those whose near vision is top
priority. This would include patients who prefer to hold reading material close, do
a lot of paperwork or spend a great deal of time knitting.
• Discuss astigmatism early. Patients receiving multifocal presbyopia-
correction IOLs should have .75D or less of astigmatism postoperatively. Higher
levels need to be reduced with LASIK, PRK or limbal-relaxing incisions. Inform
patients about this well in advance so a required additional procedure isn’t a
surprise.
• Beware of the Type A personality. Patients seeking perfection or insisting
on a guarantee of 100% spectacle independence may be impossible to satisfy, even
if their results are excellent.
• Spend time with patients. Be prepared to spend time with patients before
surgery to discuss vision goals and expectations. Also be prepared to spend time
with them after surgery. This category of lenses is complex, and patients need
education and reassurance post-op to help them understand and adapt to their new
vision. Well-trained assistants can help with these responsibilities, but you must
remain involved.
• Inform all patients about the lenses. Even patients who aren’t candidates
should be told about presbyopia-correcting IOLs and why they wouldn’t benefit
from them personally. If they receive this information from someone else, it will
reflect poorly on you.
• Get comfortable discussing financial aspects. Just as refractive surgeons
have had to do all along, refractive-cataract surgeons must be able to explain to
patients the additional out-of-pocket costs involved with choosing the latest IOLs.
A Strong Start Will Serve You Well
Educating yourself about presbyopia-correcting IOLs and choosing your first
cases conservatively, as I have described here, will allow you to achieve good
results from the start and thus build confidence. From there, you’ll be able to
expand the types of patients for which you recommend the lenses. You should find,
as I did, that putting the proper effort into patient selection and communication is
the best way to ensure ongoing success.
Figures 1 and 2. The AcrySof IQ ReSTOR IOL with +3.0D add power is built on
the same platform as the AcrySof IQ ReSTOR IOL with +4.0D add power. The
add power was modified by slightly widening the diffractive steps and decreasing
their number from 12 to 9.
Figure 3. In the clinical trial comparing the AcrySof IQ ReSTOR +3.0D IOL with
the AcrySof IQ ReSTOR +4.0D IOL, patients who received the +3.0D lens had
twice the near-to-intermediate range of vision at 20/25 or better.
Figure 4. A high percentage of patients who participated in the clinical trial
comparing the AcrySof IQ ReSTOR IOL +3.0D with the AcrySof IQ ReSTOR
IOL +4.0D were satisfied with their results.
Dr. Maxwell is a partner at Fogg, Maxwell, Lanier & Remington EyeCare, based
in Fresno, Calif. He’s a leading investigator of intraocular lens implants for
cataract surgery. Dr. Maxwell is a consultant to Alcon. He can be reached at (559)
449-5010 or amaxwell@eyecarefresno.com.
REFERENCES
1. Maxwell WA, Lane SS, Zhou F. Performance of presbyopia-correcting
intraocular lenses in distance optical bench tests. J Cataract Refract Surg
2009;35:166-171.
2. Maxwell WA, Cionni RJ, Lehmann RP, Modi SS. Functional outcomes after
bilateral implantation of apodized diffractive aspheric acrylic intraocular lenses
with a +3.0 or +4.0 diopter addition power: randomized multicenter clinical study.
J Cataract Refract Surg 2009;35:2054-2061.
SIDEBAR HEADLNE: When a Presbyopia-Correcting IOL May Not Be the
Best Option
Recognizing which patients may not be good candidates for presbyopia-
correcting IOLs is an important part of patient selection. Here are some examples
of my cases in which I recommended a different type of IOL. A multifocal IOL is
not necessarily absolutely contraindicated in these particular cases. However, they
illustrate situations in which you should exercise caution, especially early in your
experience.
Case One
A 63-year-old truck driver came to the office complaining of difficulty
driving at night. He had early posterior subcapsular cataract in both eyes and best-
corrected visual acuity of 20/25 and 20/30. With glare testing at a medium setting,
his acuity was 20/60. Because he drives for a living, distance vision is his primary
concern, and he indicated he wouldn’t be able to tolerate any interference with his
night vision.
The aspheric optics of the AcrySof IQ ReSTOR IOLs have nearly eliminated
any problems with night driving for my patients, but any multifocal IOL has the
potential to reduce contrast sensitivity and cause halos around lights, either of
which could pose a problem for this patient given his specific concern. Therefore, I
chose not to implant a ReSTOR lens. Instead, we chose a monofocal AcrySof IQ
IOL, and the patient has been extremely satisfied.
Case Two
A 72-year-old female with bilateral nuclear sclerotic cataract and best-
corrected visual acuity of 20/50 OD and 20/70 OS was also found to have early
anterior basement membrane dystrophy and a history of dry eye. Schrimer testing
showed 5 mm of tear production. She also had 1.25D of astigmatism in each eye.
The astigmatism was with the rule, but would have been increased to more than
1.50D with the temporal cataract surgery incision.
She expressed a desire to have clear uncorrected vision at both near and
distance. However, when she was informed that she may have decreased acuity
because of her corneal issues and residual astigmatism, she decided against a
presbyopia-correcting IOL. We discussed monovision as an option, but she
ultimately decided that the clearest possible distance vision was what she preferred.
We implanted an AcrySof IQ Toric IOL, which significantly reduced her
astigmatism without the need for limbal-relaxing incisions, provided her with
optimal uncorrected distance vision, and avoided the concern that she wouldn’t
benefit fully from a presbyopia-correcting option.
Case Three
During discussion about cataract surgery, a 70-year-old male patient
mentioned that his neighbor received an IOL that allowed him to see at near and
distance without eyeglasses and that he was interested in that option as well. The
patient had nuclear sclerotic cataract in both eyes with best-corrected acuity of
20/70 in one eye and 20/100 in the other. Upon examination, we noted he also had
early dry macular degeneration. Testing with the retinal acuity meter indicated
vision could be improved only to 20/40 in both eyes. OCT didn’t reveal any other
retinal issues.
With experience, you’ll be able to make a good determination of the extent to
which early AMD would degrade a patient’s post-cataract surgery vision. In this
case, I explained to the patient that in my opinion, his early AMD could
compromise his near and distance vision and could prevent him from achieving the
level of visual acuity that his neighbor had achieved.
Instead of a multifocal IOL, we chose the AcrySof IQ monofocal IOL for him.
After surgery, he reported that he was seeing colors vividly and things appeared
brighter to him compared with before surgery. His current best-corrected distance
acuity is 20/30 in one eye and 20/40 in the other and he’s pleased with his quality
of vision and the improvement in his quality of life.
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