Innovative Technology Improves IOL Outcomes

Here's how you can use the 3-D Wave to select the best IOL for each patient.

By Farrell C. Tyson II, MD, FACS

As a refractive cataract surgeon, I've been using the Marco 3-D Wave* in two of my clinics for more than 4 years. The Marco 3-D Wave is a multifunctional diagnostic device with a very small footprint. At first glance, one might mistake it for a basic autorefractor or small topographer. In reality, it's an autorefractor, keratometer, corneal topographer, wavefront aberrometer and light and dark pupillometer. With the ever-decreasing amount of real estate in an ophthalmology office, it's convenient that the functions of several different machines have been combined into one. This allows for increased productivity in a busy office, since patients don't have to be moved from room to room to be evaluated using various machines. In our clinic, we eliminated 30 minutes from every LASIK workup by implementing the Marco 3-D Wave. Here's what I've experienced with this innovative technology.

*The 3-D Wave (OPD Scan II) is manufactured for Marco by Nidek.

Fast, Comprehensive Data

Many practices have specialized equipment, such as topographers or wavefront analyzers, that are only used in special cases. The Marco 3-D Wave is the gatekeeper to the exam rooms in my practice. Almost all patients undergo a 60-second exam with the 3-D Wave. In this amount of time, I receive the patient's autorefraction, wavefront refraction, corneal topography, pupillometry, keratometry and corneal or total wavefront analysis. This supplies me with a vast amount of knowledge before I even enter the exam room. This knowledge, along with a thorough slit lamp exam and patient discussion, helps me make a more accurate diagnosis and better educate patients on the different IOL options for their particular situation, whether they need standard monofocals, wavefront enhanced IOLs, toric IOLs or multifocal IOLs.

Customize to Suit Your Needs

The 3-D Wave is fully customizable from corneal refractive indices to match your manual keratometer to the layout of maps on your screen and on printouts. I prefer a layout that includes six maps. Two maps are for left- and right-eye axial topographic maps. The next two maps are the internal optical path difference (OPD) maps for the right and left eyes. The last two maps are the total OPD maps for the right and left eyes. At the bottom of the page, the autorefraction, simulated keratometry, light and dark pupillometry, and the corneal spherical aberration values are displayed. All maps and values can be changed and printed on the fly as the need arises. Over time, users can develop and save formats for different patients such as cataract evaluation, pre-LASIK and postsurgical.

Wavefront-enhanced Lenses

The use of wavefront-enhanced lenses has become almost the standard of care. Currently, there are four different manufacturers with NTIOL-status-approved lenses. Most surgeons assume they're all the same except for the platform they're on or the injector system they use. This is an over-simplification of the technology, since in most cases, a wavefront-enhanced lens provides a benefit when compared to a standard monofocal implant. But there are times when a wavefront-enhanced lens is contraindicated.

The basic premise is this: most patients who have cataracts are of a certain age and, as such, most have about 0.27 microns of positive corneal spherical aberration. If this can be corrected with a spherical aberration-correcting lens, then contrast sensitivity will be increased. The problem arising is that not all corneas have the same amount of spherical aberration (SA). Luckily, different manufacturers employ different amounts of correction. Alcon's SN60WF corrects 0.17 microns SA; the Tecnis family (Abbott Medical Optics [AMO]) corrects 0.27 microns SA; Bausch & Lomb's AO/AOV corrects 0.0 microns SA, and STAAR's AQ2010 corrects 0.08 microns SA.

To utilize these lenses to their fullest potential, we need to ascertain the corneal spherical aberration present in a patient's eyes. I use my Marco 3-D Wave to help select which lenses would have the best chance of success in a particular patient's eyes.

I start by obtaining an axial topographic map, internal OPD map, total OPD map, autorefraction, light/dark pupillometry and corneal spherical aberration. The axial topographic map and internal OPD map reveal patients that might be better served with toric IOLs. If a large amount of residual astigmatism is present after surgery, their vision is going to be poor no matter how good a job we do when minimizing spherical aberration. The light and dark pupillometry is important, because spherical aberration correction is only a benefit to patients whose pupils dilate normally. If no difference is seen between the light and dark pupillometry and the pupils are miotic, the benefit of a wavefront-enhanced lens is negated. In this scenario, the wavefront-enhanced lens will have no benefit or harm, but will bring added cost to the surgery center, since most insurers, except Medicare, don't honor the NTIOL status of the lenses.

The Marco 3-D Wave is able to provide the corneal spherical aberration. The appropriate settings must be programmed in the setup menu, so that it's evaluating corneal spherical aberration for 6-mm with an 8th-order Zernike. The Marco 3-D Wave displays the ocular and corneal spherical aberration in both microns and diopters. You also can choose to display the total spherical aberration of the entire eye, which is great for analysis of a potential LASIK candidate. When considering cataract surgery, only the corneal component is needed, since the natural lens is going to be removed.

Once you determine the corneal spherical aberration, you can select the appropriate lens. The ideal intraocular lens will minimize spherical aberration without going negative. This can be accomplished effectively with four different available choices. Sometimes we encounter extremes in spherical aberration. This is most commonly seen in postrefractive patients. Post myopic RK, PRK or LASIK procedures tend to induce excessive amounts of positive spherical aberration. In these patients, Tecnis monofocal IOLs would reduce the greatest amount of spherical aberration and would be the best option. Even after utilizing a Tecnis lens in a post-myopic refractive patient, there probably will be residual spherical aberration.

On the other end of the spectrum is the posthyperopic PRK or LASIK patient. These patients have an excessive amount of negative spherical aberration. If a wavefront-enhanced IOL is used in one of these patients, the spherical aberration will be exacerbated. It would be better to use a standard monofocal IOL, which induces positive spherical aberration. One of the challenges I've found with postrefractive surgery patients who are considering cataract surgery is that most of these patients don't remember what type of surgery they had. Was it myopic or hyperopic surgery? Most patients don't save information on their treatment plans. This is where the axial topographic map helps elucidate the enigma. The axial map should show a central flattening in postmyopic refractive surgery patients, and a central steepening with peripheral flattening in post-hyperopic refractive surgery patients.

Multifocal Intraocular Lenses

Over the last couple of years, the bar has been raised in cataract surgery with the addition of multifocal lenses. It used to be that if you could come close on the patient's distance vision, it was considered a great job. Now, with multifocal IOLs, you're not trying to hit one focal point but two. This, along with greatly increased patient expectations, has pushed surgeons to achieve perfection. To do this, we need more than just accurate axial length measurements and reproducible keratometry. We need a multifunctional device, such as the Marco 3-D Wave, to help guide the lens selection for our patients.

I begin by evaluating my patients with an axial topographic map. This allows me to determine if there are any corneal irregularities or astigmatism. If more than 1.5 diopters of astigmatism are present in the cornea, I tend to lean toward a toric IOL. If the patient has 1.5 diopters or less of astigmatism, I know I can successfully treat with limbal relaxing incisions. Some highly motivated patients with moderate amounts of astigmatism may be appropriate candidates for bioptics procedures. If there's asymmetric astigmatism present, these patients are eliminated from consideration for a multifocal lens.

The next step when considering a multifocal lens candidate is evaluating the internal OPD map. Usually this is a symmetric map, but often, lenticular astigmatism will be present. These are the patients you may have excluded initially, based on the astigmatism in their prescription. Instead, you find little corneal astigmatism but significant lenticular astigmatism. These patients are some of the easiest to satisfy, because they've lived with the astigmatism for a long time so their expectations are lower.

The eye image map can be very helpful with multifocal lens candidates. When viewing this image, the surgeon can see the quality of the corneal tear film by observing the placido ring reflections. If the rings are sharp and round without distortion, the ocular surface is usually in good condition. If the rings have distortion or are missing in sections, ocular surface disease is present. Ocular surface disease is a detriment to any cataract surgery but especially multifocal lenses. Multifocal lenses have decreased contrast sensitivity and increased glare and halos compared to monofocal implants. If you combine ocular surface disease with multifocal lenses, the results can be disastrous, with poor reading vision and excessive night vision dysphotopsias.

The light and dark pupillometry readings help guide the selection of multifocal lenses. If the light (photopic) pupillometry readings are 2.5 mm or less, then I'd shy away from using a ReZoom (AMO) implant, since the near portion of the lens would be effectively hidden. This would result in a distance-only implant. For small-pupil patients, the ReSTOR (Alcon) or Tecnis Multifocal (AMO) implants would be a better option. With small-pupil patients, the benefit of spherical aberration correction that's built into some lenses will be minimized.

Patients with large light pupillometry readings pose a different challenge. These patients may do well with the ReZoom implant, since their near vision will improve, but they may have increased halos at night. The ReSTOR implant becomes distant-dominant as pupil size increases. This may lead to good distance vision during the day and night, but reading vision may suffer in patients with larger photopic pupils. The Tecnis multifocal implant with its full diffractive optic would allow for good distance and near vision in this patient population.

Dark (mesopic) pupillometry is just as important in selecting multifocal implants. If the mesopic pupillometry readings are very large, then the chance for nighttime glare and halos increases. These patients might be best served with the partially diffractive optic of the ReSTOR Aspheric implant. The ReZoom lens would be the most problematic with increased halos present around lights. If nighttime reading vision were most important to the patient, then the Tecnis Multifocal would be the better option.

Recently, we've been given a choice in the amount of spherical aberration correction with multifocal lenses. To help reduce the loss of contrast inherent in a multifocal design, the manufacturers added spherical aberration correction. The ReSTOR Aspheric implant corrects for 0.10 microns of positive spherical aberration, and the Tecnis Multifocal implant corrects for 0.27 microns. If the choice has been made to implant a diffractive multifocal implant, then the next step is to determine the corneal spherical aberration of the patient. The process for using the Marco 3-D Wave for this evaluation is the same as that used for selecting aspheric monofocals.

The use of multifocals in postrefractive patients comes with many pitfalls. We must realize that we're mixing two contrast-reducing technologies together. In addition, it's highly likely that a multistage procedure will be required to obtain a successful outcome. This is due to the reduced accuracy of IOL calculations after postrefractive surgery, which results in residual refractive error. Postmyopic refractive surgery patients usually have high amounts of positive spherical aberration. In these individuals, you should reduce as much spherical aberration as possible. That would be best accomplished with the Tecnis multifocal. I personally won't implant a multifocal in a posthyperopic refractive surgery patient.

Following successful implantation of a multifocal lens, I prefer to see my patients the next day. On the 1-day follow-up, I have my technician obtain a 3-D Wave scan. Most autorefractors have difficulty with day 1 eyes — not to mention difficulty with multifocal lenses. The Marco 3-D Wave has no problem producing an accurate autorefraction with diffractive multifocal lenses just 1 day after surgery. ReZoom implants tend to over-minus on all autorefractors, because they're averaging the distance and near zones. When working with ReZoom implants, it's best to obtain a Total OPD map. This map allows you to determine if the central vision is at the desired level.

At the 1-month visit, I prefer to obtain an autorefraction, an axial topographic map, internal OPD and a total OPD. These evaluations provide me with information on induced or residual astigmatism, implant placement, pupillary effects in relation to the implant and how the total optical system is performing for the patient. If the vision isn't as sharp as I'd like, I can use an Eye Image in conjunction with the internal OPD to ascertain whether the implant is centered on the optical axis. To do this, place the cursor on the corneal reflex of the eye image. The cursor on the internal OPD map is then the center of the optical axis. Hopefully, the implant is centered on the cursor. The ReZoom implant has a relatively large central zone, which allows for some decentration without loss of optical performance. The Tecnis multifocal has a smaller central zone, which requires better centration. The ReSTOR has the smallest central zone, thus requiring the best centration for optimal performance.

Toric Intraocular Lenses

The popularity of toric IOLs has increased dramatically over the last several years. This is due, in large part, to the CMS ruling that allowed for patient-shared billing of the increased costs of the lenses and the extra testing needed to properly use the new lenses and technology. In my practice, the Marco 3-D Wave plays an integral part in our astigmatism-correcting cataract practice.

We begin the initial evaluation of our patients with an axial corneal topography map, an internal OPD map and a total OPD map. This allows for a very quick overview of the different parts of the patient's visual system. The axial topography map allows for a quantitative analysis of corneal curvature. I use the keratometry from the Marco 3-D Wave for all of my toric IOL calculations, since they're reproducible and I can visually verify if they make sense by examining the topographic map.

Manual K's or IOL Master K's are based on the maximum and minimum readings on a central ring and not an area. This can be fooled by asymmetric astigmatism. An axial corneal topographic map, on the other hand, quickly displays asymmetric astigmatism cases, which may not be best treated with toric IOLs. In addition, since the Marco 3-D Wave has a placido ring-based corneal topography system, some diseases, such as pellucid marginal degeneration and keratoconus, are more easily identified than with elevation-based corneal topographers on the market. The visual representation of symmetric astigmatism as a "bow tie" makes it very easy for patients to understand that their eye is shaped more like a football than a soccer ball. This visual understanding makes it easier to explain the need to upgrade to a toric implant.

The internal OPD map is just as valuable in dealing with potential toric IOL candidates. This map displays the refractive aspects of the natural lens preoperatively. Usually, this map is very symmetric with little to no lenticular astigmatism. When this occurs, the astigmatism of the patients' refraction should be very similar to the astigmatism from the axial topographic map and the autorefraction. If these values don't match, then the use of a toric lens needs to be questioned. Many times, patients present preoperatively with little astigmatism in their prescription, but a significant amount on their axial topographic map. In this scenario, it's important to evaluate the internal OPD to verify that lenticular astigmatism is counteracting the corneal astigmatism. When confronted with such cases, it's always best to verify the corneal astigmatism with manual keratometry.

The total OPD scan is a good overview of the total visual system of the patient. This map helps you quickly understand what your patient is experiencing. It's best to have the pupillary border overlay on. Sometimes patients with small photopic pupils are able to mask significant astigmatic error by using the pinhole effect. These patients need more counseling, since they may not understand the benefit of a toric implant.

After successful cataract surgery and implantation of a toric IOL, you must perform an analysis. In the past, IOL rotation has plagued toric IOLs. With new designs and materials, and smaller capsulorrhexis size, rotation isn't as common. Post-operatively, I prefer an axial topographic map, an internal OPD and a total OPD. The axial map allows me to see if any change has occurred in the corneal shape as a result of my corneal incision. I also can check for any corneal edema.

Postoperatively with toric IOL cases, I find the internal OPD scan the most useful (Figure 1). All toric implants have axis markers, which you can see easily in a well-dilated patient, but they can be almost impossible to find in a undilated patient. This is especially true in patients using tamsulosin (Flomax) or pilocarpine, who, in many cases, never dilated well for the surgery. This is where the 3-D Wave really makes postoperative analysis of toric IOL patients easy. There's no need to dilate. By using the internal OPD map, it's easy to visualize the optical axis of the toric implant. To analyze centration of the implant, use the Eye Image map and place the cursor on the corneal reflex. The cursor on the internal OPD scan will then correspond with the placement of the cursor on the corneal reflex. If the IOL is properly centered on the optical axis, the cursor on the internal OPD map should be centered in the middle of the astigmatic "bow tie."

Figure 1. Postoperatively with toric IOL cases, the internal OPD scan is very useful, since all toric implants have axis markers, which you can see in a well-dilated patient, but they can be almost impossible to find in an undilated patient.

When evaluating internal OPD astigmatism, one needs to understand that this is being measured at the lenticular plane and isn't being converted to a corneal plane equivalent. Therefore, you should expect the measured internal OPD astigmatism readings to match the toric IOL labeling on the box where manufacturers list lenticular astigmatism values for their lenses. If the internal OPD astigmatism doesn't initially match the toric IOL astigmatism, then you know more healing needs to occur. The patient may have corneal edema. As the patient heals from surgery, you'll find that the internal OPD scan will become sharper and more precise. At the 1-month postoperative exam, I determine how much residual astigmatism is present. If it's over 0.75 diopters and visually significant, I'll enhance the patient with an LRI. This treatment is based on the refraction, not the corneal topography. I'll resist the urge to rotate the lens unless it's grossly off axis, since there are too many vectors to take into consideration.

Unusual Cases

The Marco 3-D Wave is very beneficial in helping us understand the unusual cases we encounter in a comprehensive ophthalmology office. Most physicians are familiar with the patient who always makes the autorefractor over cyl and over minus. This is because the autorefractors get confused when patients have high amounts of higher-order aberrations. The 3-D Wave does a very good job of producing a wavefront refraction in these patients, who may only need sphere refinement, and you may obtain a Zernike graph to verify their higher-order aberrations.

Accommodating IOLs can present a new set of challenges. The "Z" syndrome may not be easily visible at the slit lamp, but the internal OPD map can highlight and quantitate lens tilt. Also, you can analyze IOL dislocation on the internal OPD map. Even small dislocations can be problematic to patients. In Figure 2, a Crystalens HD50 (Bausch & Lomb) lens is slightly dislocated inferiorly and an almost 20-diopter difference in refractive power is visible to the patient as seen on the internal OPD map.

Figure 2. Internal OPD maps reveal an almost 20-diopter difference in refractive power and an accommodating IOL that's slightly dislocated inferiorly.

When encountering patients with unusually difficult refractions or unusual keratometery, the 3-D Wave axial maps can help explain the issue. Irregular astigmatism is easily displayed on the axial map. This makes identification of pellucid marginal degeneration as a "lobster claw" (Figure 3) or keratoconus easy compared to using an elevation-based topographer. You can even identify corneal deformation by an applanation tonometer by using the 3-D Wave (Figure 4).

Figure 3. Axial maps clearly display irregular astigmatism, making identification of pellucid marginal degeneration easier with the 3-D Wave than with an elevation-based topographer.

Figure 4. Corneal deformation by an applanation tonometer is easily identified with the axial maps and the Eye Images from the 3-D Wave.

The Marco 3-D Wave truly is a multifunctional diagnostic device. It's an autorefractor, corneal topographer, wavefront analyzer, pupillometer and wavefront aberrometer. This technology combination allows for increased practice productivity. Plus, the 3-D Wave essentially measures 100% of each patient's visual system, which can help you achieve better outcomes for your IOL patients.

Dr. Tyson is a refractive cataract/glaucoma surgeon at the Cape Coral Eye Center in Florida.