Refractive + Diffractive = Success With Multifocal IOLs

Next-generation custom matching.

BY ANGEL LÓPEZ CASTRO, M.D.

With the recent availability of multifocal and accommodating IOLs, surgeons now have the ability to potentially provide spectacle-free vision at all distances for our cataract and refractive lens exchange patients. It’s a very exciting time, but also confusing, given the various properties of the IOLs in the marketplace and the varied needs and expectations of patients. And so far, all of the new presbyopia-correcting IOLs involve tradeoffs. Some are more suited for distance vision, others for near. None of them are perfect.

I have been drawn to the concept of combining two IOLs with different optical properties to maximize the patient’s range of vision. One might consider a variety of lens combinations, including monofocal-multifocal combinations. To me, mixing one diffractive and one refractive multifocal IOL makes the most sense intuitively, given the synergistic strengths of these technologies. In this article, I will review what I’ve learned about custom matching IOLs.

Improving Intermediate Vision

To date, my experience with custom matching has been primarily with the combination of a ReZoom (Advanced Medical Optics [AMO], Santa Ana, Calif.) refractive multifocal IOL in the dominant eye and a Tecnis (AMO) aspheric diffractive multifocal IOL in the other eye. My original goal in combining these lenses was to improve intermediate vision, which was weak in patients with bilateral diffractive IOLs. However, I also found that this combination provides other advantages, primarily by extending the range of vision under different lighting conditions.

The refractive ReZoom lens provides the intermediate vision that is missing in bilateral implantation of diffractive IOLs. In bright light, it provides superior distance visual acuity (VA) with no loss of light transmission, while the diffractive multifocal Tecnis provides excellent near with the aspheric Tecnis platform.

In dim light, ReZoom provides reading capability in the middle range of the pupil. Meanwhile, the outer portion of the Tecnis multifocal lens becomes dominant, providing better distance vision and decreasing nighttime photic phenomena. Thus, combining the optical properties of these two lenses provides patients with a full range of vision under most lighting conditions.

Previously, I would have recommended refractive lenses for light-to-moderate readers, computer users, people who primarily drive during the day, and those who enjoy sports, cards or other indoor activities. I would have chosen diffractive lenses for patients who are heavy readers, drive or work at night, or who enjoy going to the movies. But the night driver who also uses a computer was problematic because neither option would fully meet his lifestyle needs. The great thing about custom IOL matching is that a diffractive-refractive IOL combination suits most activities of any given patient, so it allows you to increase the number of candidates for multifocal IOLs in your practice.

"Mixed" Vision and the Brain

Beyond just the technical properties of the IOLs, we must also consider the ability of the brain to accept input from two different visual systems. Some people have opposed any mixing and matching of presbyopia IOLs for this very reason. In my experience, however, healthy eyes have no trouble integrating the vision from two lenses. I have not heard any complaints from my patients related to image processing, and I have not had to explant any lenses. As with any multifocal lens, there is a process of neural adaptation that can take up to 2 or 3 months. During this period, contrast sensitivity and near vision continue to improve.

Comparing Bilateral to Mix-and-Match

We performed some retrospective analyses of cataract and refractive lens exchange patients to see how the custommatching approach compares with bilateral multifocal IOL implantation. The first group includes 36 patients with bilateral implantation of multifocal diffractive IOLs. These patients have been followed for 1 year; LASIK touch-ups for residual sphere or cylinder have been performed, if needed, during that postoperative period.

The second group consists of 31 patients with a ReZoom refractive IOL in the dominant eye and a diffractive Tecnis multifocal IOL in the non-dominant eye. So far, we have just 3 months follow-up on these patients, and we have not performed any LASIK enhancements yet.

In both groups, we measured binocular VA with the best distance correction under two different illumination conditions and at three different distances. Photopic vision was assessed at 85 candelas/m² and mesopic vision at 2.5 candelas/m². Distance vision was assessed at 6 meters using an ETDRS chart; intermediate was assessed at 70 cm and near at 40 cm, both with a Jaeger test.

Even though the comparison is a little biased against the mix-and-match group (which had shorter follow-up and no enhancements), these patients definitely fared better than the first group. In bright light, distance and near acuity were comparable in both groups. But three times as many mix-and-match patients (60% vs. 20%) could see J3 at intermediate distances in bright light.

Under mesopic conditions, 85% of mix-and-match patients achieved J3 or better reading vision, vs. 70% in the bilateral diffractive group. The average near acuity for the mix-and-match group is J2.4, compared with J4.1 for the bilateral group (Figure 1). The difference is statistically significant. Twice as many patients in the mix-and-match group (60% vs. 30%) have intermediate acuity of at least J5 in dim light. Distance VA is very good in both groups.

With any multifocal IOL, we would anticipate performing laser refractive surgery enhancements on a significant portion of cases for correction of astigmatism at least, and sometimes for sphere enhancement, as well. Looking at the two groups in this study, we can see that the mix-and-match approach significantly reduces the need for enhancements. Nearly half (46%) of the bilateral diffractive group has needed a laser enhancement, compared to only 33% of the mix-and-match patients that we expect to enhance.

Overall, the mixed IOL group is more satisfied with their vision after surgery, with 88.5% saying they would choose these lenses again, compared to 82.4% of the bilateral diffractive group. In the mixed IOL group, about 85% say they never wear glasses, even prior to LASIK enhancement. Those who wear glasses occasionally do so for either near or intermediate tasks. In the bilateral group, nearly 20% said they needed glasses for intermediate tasks.

When we ask about photic disturbances, 92% of mix-and-match patients say they experience no or moderate glare, vs. 64% in the bilateral diffractive group. Halos are the most common complaint in both groups. However, none of the mix-and-match patients, vs. 36% of the bilateral diffractive group, reported severe night vision problems.

Figure 1. The average near acuity for the mix-and-match group is J2.4, compared to J4.1 for the bilateral group, a statistically significant difference between the two cohorts. Distance VA was good in both groups.

This study shows that patients gain near mesopic vision, distant photopic vision and intermediate acuity at all light levels from a mix-and-match approach. Patients with a combination of refractive and diffractive IOLs report high visual quality, with most (85%) achieving total freedom from spectacles even before LASIK enhancement. We observed significantly lower night vision complaints in the mix-and-match patients, with fewer requests for LASIK enhancements. Patient satisfaction reports show that complementary IOLs offer these patients the opportunity to maximize their vision to meet all their lifestyle needs (Figure 2).

Pearls for Success with Custom Matching

■ Careful selection of candidates for multifocal IOLs, whether for bilateral or mixed implantation, is always crucial. Some extra chair time is required preoperatively to establish the patient’s visual needs and tolerance for photic phenomena. In addition, appropriate candidates must have good ocular health. They should have no corneal or macular pathology, no glaucoma, amblyopia, or uncontrolled dry eye. Patients with such conditions are not likely to achieve optimal visual outcomes with advanced presbyopia lenses.

■ When considering implantation of a diffractive-refractive mix, be sure to test for eye dominance. The ReZoom or other refractive multifocal IOL should be implanted in the dominant eye.

Figure 2. The subjects with a combination of refractive and diffractive IOLs reported high visual quality, with 85% achieving total freedom from spectacles even prior to LASIK enhancements. The mix-and-match subjects also reported lower night vision complaints and had fewer requests for LASIK enhancements compared to the bilateral group.

■ Biometry and lens power calculations should be precise, and laser vision correction or another method of enhancement must be anticipated, especially for correction of cylinder. To achieve good performance with these lenses, it is mandatory to have an emmetropic or slightly hyperopic (0.5 D maximum) result.

■ Counsel patients to expect some halo or other visual symptoms. They should also anticipate continued improvement in vision over the initial 2 to 3 postoperative months.

For surgeons who have not been fully satisfied with their results with bilateral diffractive IOL, I would urge that they consider a diffractive-refractive mix. Such a combination offers patients the advantages of both technologies and an extended range of vision in most lighting conditions. OM

Angel López Castro, M.D., is in private practice in Madrid, Spain. He receives travel reimbursements from AMO on an occasional basis. Contact him at +34-91-444-8230 or alopez@laservision.es.