Make an Educated IOL Decision
The good news is there are numerous IOL models from which to choose. The bad news is there are numerous IOL models from which to choose. Here's how to sort out your options in patients undergoing cataract surgery.
By Parag A. Majmudar, M.D.

Years of IOL development have resulted in countless options for patients and complex choices for surgeons, starting with the decision to go with either a monofocal or a multifocal lens. Knowing the relative advantages and disadvantages of both types of IOLs might seem like the key to making the best choice, but that's only half the equation. Patients' needs and expectations, as well as an understanding of the IOLs' capabilities and limitations, represent the remaining crucial factors.

What Are My Choices?

The process of 'natural selection' has designated acrylic as the de-facto IOL material, virtually eliminating that variable from our decision-making process. Silicone IOLs have all but disappeared for several reasons. First, due to its biomechanical properties, a silicone lens unfolds rapidly once introduced into the anterior chamber. While not a major issue in and of itself, this can lead to a greater learning curve for a beginning surgeon. Another issue is that if a patient with a silicone IOL would require a silicone oil injection during retinal reattachment surgery, the interaction between the oil and the IOL could lead to difficulties visualizing the fundus. Therefore, surgeons historically avoided implanting these lenses in diabetic patients, some of whom could conceivably require silicone oil as a consequence of diabetic retinopathy.

Another choice that surgeons face is selecting a single-piece IOL versus a three-piece IOL, and this is really a matter of surgeon preference. Although some surgeons say a single-piece lens offers better centration, the drawback is that this type of lens is not designed to reside in the sulcus, as the haptics can chafe the iris and cause pigment dispersion syndrome. This is clinically relevant only when the one-piece lens has been implanted and the capsule is com

Some elderly patients sit for hours and read, so they'll likely want good near vision [after cataract surgery] and probably aren't as
concerned about computer vision.

We have a choice of material and design only to a point. Certain types of IOLs are available only in specific configurations as far as lens material and design, and we're constrained by these elements, especially when considering the more advanced presbyopia-correcting IOLs.

Check Out Everything

Early in your career, you'll find that your affiliation with a specific hospital or ambulatory surgery center (ASC), as well as your relationships with IOL suppliers, will dictate the lenses you use. In the meantime, familiarizing yourself with the nuances of the most frequently used IOLs is a must. These include standard monofocal lenses and wavefront-optimized monofocal lenses, as well as presbyopia-correcting lenses, which include multifocal lenses and accommodating or pseudo-accommodating lenses.

A subcategory of monofocal IOLs, wavefront-optimized lenses are designed to minimize spherical aberrations. Even though they don't yet facilitate multiple levels of vision like multifocal lenses, wavefront-optimized lenses are an advance over standard monofocal IOLs and will, within the next several years, be available in the United States in a multifocal design as well.

The other major category — presbyopia-correcting lenses — is the newest trend in IOLs. Having a clear understanding of the optics of these lenses is crucial because they will become a major part of your armamentarium as you go forward.

Monofocal IOLs

Although several monofocal lenses are available, for the most part, I don't think it matters from patient to patient whether they get a lens from manufacturer "A" or manufacturer "B." The lenses do, however, have different features, and it's important to be familiar with them.

For instance, Alcon AcrySof IOLs have a "double" square edge, in which both the anterior and the posterior edges are "squared." This means the outer edges of the lens will be in close apposition to the capsular fornix and may decrease the chance of epithelial cells migrating behind the lens and causing a secondary cataract or posterior capsular opacification (PCO). One drawback to the squared anterior edge, however, is that there may be a higher incidence of unwanted glare symptoms, called "dysphotopsias."

On the other hand, AMO makes an IOL that has a square edge on the back surface and a rounded edge on the front. The advantage of this design, called "OptiEdge," is that the square posterior edge decreases the likelihood of PCO, whereas its rounded anterior edge limits light reflection and works to reduce glare symptoms. If a patient complains of nighttime glare problems, this information is essential in terms of patient/IOL compatibility.

One lens that's new to the wavefront-optimized monofocal category and getting a lot of attention is the Tecnis IOL. This lens has asphericity built into it to compensate for the cornea's negative asphericity, and, theoretically, this reduces spherical aberration. This lens may be one to consider for patients who are concerned about night driving.

AMO recently switched the Tecnis IOL from a silicone platform to an acrylic platform and received a new technology IOL (NTIOL) designation. This designation was in response to labeling claims approved by the FDA that the Tecnis IOL reduces postoperative spherical aberrations compared to lenses with spherical optics, and that it also improves night-driving simulator performance.

The NTIOL designation means that the Center for Medicare Services (CMS) reimburses the ASC or hospital that buys an NTIOL $50 more per lens than for a traditional IOL to help defray the cost of these new technology lenses. The surgeon receives the same Medicare reimbursement whether heimplants a traditional IOL or an NTIOL, but the extra reimbursement makes it more likely that facilities will make these innovative lenses available to surgeons who, in turn, can offer them to their patients.

Presbyopia-correcting IOLs

There are 3 presbyopia-correcting IOLs available today, but many more are in the pipeline. The products that have a head start in this arena are the AMO ReZoom, the Alcon ReSTOR and the Eyeonics crystalens. These IOLs are revolutionizing cataract surgery for several reasons. Unlike monofocal lenses, which provide good distance vision or good distance and near vision through monovision, the presbyopia-correcting IOLs afford patients a tremendous opportunity for spectacle independence for both distance and near vision in the same eye. However, they also demand that cataract surgeons become "refractive-cataract" surgeons, taking as much care with preoperative measurements and patient selection in a cataract case as they would in
a LASIK case.

Surgeons just starting out need to know that with these multi-focal IOLs, if the preoperative measurements aren't meticulous, preoperative astigmatism is not addressed and surgically induced astigmatism isn't controlled. As a result, patients won't get the results that these excellent lenses are capable of providing. In addition to having a dissatisfied patient, you'll end up having to correct the residual error, which means either performing a laser procedure yourself or referring the patient to someone else.

I train residents and often see that many of them are so focused on learning how to remove a cataract that they don't pay much attention to what happens after that. They do themselves a
disservice with this mindset because the IOL technology available today demands more.

You have to deliver outstanding outcomes. These patients are opting to pay out-of-pocket for the additional benefits that presbyopia-correcting IOLs can provide, and it's up to the surgeon to deliver.

Match Patient to Implant

In addition to precise measurements and surgical technique, careful patient selection is another critical component in ensuring excellent outcomes with multifocal IOLs. In the early days of laser refractive surgery, we paid very close attention to patient selection in an effort to achieve the best possible outcomes. Over the years, we're hearing less and less about patient selection with respect to laser surgery, but we need to return to this basic tenet of refractive surgery and incorporate it into our cataract surgery.

Remember, these are cash-paying customers, and they'll be very demanding and intolerant of a less-than-perfect outcome. For instance, if a prospective patient is an exceedingly demanding, type-A personality with obviously unrealistic expectations, you should avoid offering a multifocal IOL. Patients who are intolerant of anything but "perfection" are not good candidates, and neither are those who would be reluctant to undergo a second procedure to exchange the lens if they remained unsatisfied.

Other patients who are not the best candidates for multi-focal IOLs are myopes, because myopes tend to have good near vision even with a moderate cataract. The near vision that a multifocal IOL can achieve usually is not as good as the near vision of a myope with a natural lens. So don't use these lenses, at least at first, in myopes, unless they have a dense cataract and they realize they'll probably lose near vision.

With the exception of the crystalens and other future "accommodating" lenses, all multifocal lenses achieve their success by providing multiple, simultaneous retinal images to which the brain must adapt over time.

This is the source of night-time halos or glare that are present to varying degrees in every multifocal lens. Patients who do a lot of work in mesopic conditions (radiologists, truck drivers who drive at night and people with similar occupations) should be counseled about these potential unwanted side effects.

Presbyopia-correcting lenses are very appealing to most patients, so you must judge which patient will be best served by them, and who will be least critical of real or perceived imperfections in quality of vision.

Keep in mind that monovision with monofocal lenses is still an excellent option, and patients make the transition easily, especially if they were accustomed to monovision with their contact lenses. Converting a monovision patient to multifocal IOLs might not produce the happiest patient.

Choose Your IOL Wisely

Once you have a patient you believe is a good candidate for a presbyopia-correcting IOL, how do you choose the most appropriate among the three? Start by having a discussion with the patient about his work and hobbies.

Some elderly patients sit for hours and read, so they'll likely want good near vision and probably aren't as concerned about computer vision. A ReSTOR lens, which is essentially a bifocal lens, might be a good choice for them.

The crystalens remains a good choice for patients unwilling to tolerate the potential glare of the multifocal lenses. However, most patients will achieve better distance and intermediate vision without correction and will require a small correction for reading.

Each lens also has some drawbacks. Since the ReSTOR lens is a distance-oriented lens, in large pupil (low light) conditions, near vision may be compromised unless additional ambient light is used to constrict the pupil and let the light pass through the central diffractive zone of the IOL. The ReZoom lens achieves very good intermediate vision in low light conditions, but may result in glare or halos for distance vision in the same conditions.

In addition to advising your patients about the relative merits and disadvantages of presbyopia-correcting IOLs, advise them to evaluate their own needs. Do they want to be able to see the computer screen and won't mind too much if they have to put on eyeglasses to read really small print or vice versa? They need to decide ahead of time what their goals are.

It's important to stress to patients that these IOLs are not perfect and will not turn back the clock 30 years. They do provide some increased flexibility over what a standard IOL can offer.

We can't promise patients that they'll never have to wear eyeglasses with presbyopia-correcting IOLs, but a very large percentage of my patients report they can do most of their activities without eyeglasses.

Underpromise, Overdeliver

Contrary to what some may say, this is an exciting time to be an ophthalmologist, especially a refractive cataract surgeon, since nearly all cataract patients today are essentially refractive surgery patients, as well. With that in mind, the best policy is to underpromise and overdeliver.

Parag A. Majmudar, M.D., is associate professor of ophthalmology at Rush University Medical Center. He is a partner at Chicago Cornea Consultants.