Managing Non-candidates for Multifocal IOLs With Premium Monofocal Technology

BY MARK PACKER, M.D.

Surgeons who have been involved in refractive cataract surgery over the past decade have witnessed many great developments — one of these being the multifocal IOL. Available for more than a decade, multifocal IOLs have provided patients with a full range of vision and allowed spectacle-independence for many.

It is evident that not every patient is a candidate for presbyopia-correcting IOL. Furthermore, not every customer will jump at the offer of spectacle independence. So, what can we offer these patients in terms of premium technology that will be of value to them?

When my patients are told that we can offer them an implant that would not only allow them to drive without glasses but also read without glasses, I have found that about half of them find value in this opportunity. The other half do not mind wearing their glasses for various reasons. Some even prefer glasses, such as a patient who politely informed me that she does not like the way her nose looks without glasses.

Review of Aspheric IOL Options

One option available for patients who do not mind wearing readers is implantation of aspheric IOLs. Aspheric IOLs have demonstrated advantages in terms of functional vision, which is measured clinically by contrast sensitivity testing.¹ The first aspheric lens on the market was the Tecnis (AMO, Santa Ana, Calif.), which was designed to be more like the youthful eye in terms of spherical aberration, thus giving better functional vision and better contrast sensitivity. By taking the average corneal spherical aberration in the population and matching it with an IOL that has the same amount of negative spherical aberration, the Tecnis design essentially provides zero mean residual spherical aberration.

The initial development of the Tecnis was followed by the creation of two other lenses in the United States — the SofPort Advanced Optic Lens (Bausch & Lomb, Rochester, N.Y.) and the AcrySof IQ lens (Alcon, Fort Worth, Texas). The SofPort Advanced Optic Lens is an aspheric IOL designed to have zero intrinsic spherical aberration. The lens alone forms a perfect system with all the peripheral and central rays of light coming to a single focus.

The AcrySof IQ lens has a smaller amount of negative spherical aberration compared to the Tecnis and falls between the pure aspheric SofPort and the mean inverse aspheric Tecnis from AMO, with about -0.2 μm. Examples of other aspheric IOL designs can be found in use outside the United States.

Evaluating Monofocal IOL Technology

In order to learn about aspheric lenses and their added value to vision, my colleagues and I conducted a study comparing the contrast sensitivity of subjects implanted with the Tecnis IOL vs. subjects implanted with a standard spherical lens and to a group of healthy normal control subjects aged from about 20 to 50 years of age.² Results showed that the group implanted with the Tecnis lens had the highest peak contrast sensitivity of any of the groups. These subjects proved to outperform the youthful eyes from the control group.

The elimination of spherical aberration allows patients to have better functional vision that correlates more with contrast sensitivity than with visual acuity. In a tightly controlled study, monitored and reviewed by the FDA, a nighttime driving simulation proved that the Tecnis IOL enhanced mesopic or nighttime vision.³ In this study, ocular dominance was randomized and participants, as well as the technicians administering the test, were masked, not knowing which lens was placed in which eye. All testing conditions — city glare, city normal, rural glare, rural normal — were incorporated into the test, as well as three different targets. The study also proved that the lens worked just as well independent of age and pupil size. Essentially, the data from this FDA-monitored study shows that the Tecnis lens, which was designed to eliminate spherical aberration, does just that.

After the FDA reviewed all of the data in relation to the Tecnis IOL, it approved labeling stating that the Tecnis does eliminate spherical aberration, performs functionally better in the 20 of 24 driving conditions tested and provides a meaningful safety benefit for elderly drivers and other drivers sharing the road.

Patient Selection

Obviously, the Tecnis lens should not be implanted for every patient. Proper patient selection is always important. For example, patients who want independence from reading glasses should not be implanted with this lens because they will continue to need their glasses. Also, keep in mind that the Tecnis IOL is designed to compensate for the average spherical aberration and not everyone fits this profile, and some patients may be good candidates for another aspheric IOL technology. Preoperatively, we can measure corneal spherical aberration with any corneal topographer and determine which aspheric IOL fits best.

When I initially had only the Tecnis IOL and a spherical IOL available, I found that essentially 96% of the population benefited from the Tecnis as opposed to the spherical IOL. Now, of course, there are additional choices. There is the pure aspheric IOL from B&L and the AcrySof IQ. If we bring these into the equation we find on a theoretical basis that about 5% of the population would actually benefit most based on spherical aberration alone from the B&L product. If we do the math involving the AcrySof IQ, we will find that about 30% of the population would find this to be the most beneficial.

There is growing evidence proving that aspheric technology and the correction of spherical aberration is an important option for our patients. In fact, CMS ruled that aspheric IOLs represent a significant benefit for patients and announced new technology IOL (NTIOL) status for these IOLs, meaning a $50 incentive is offered to ambulatory surgery centers to implant these lenses.

Proper IOL selection comes with many considerations, spectacle independence being one of the most important. Other issues may be of importance such as focus, placement, material and IOL design. Every aspect should be considered when choosing the best IOL for each case. OM

References

1. Mester U, Dillinger P, Anterist N. Impact of a modified optic design on visual function: clinical comparative study. J Cataract Refract Surg. 2003; 652-660.

2. Packer M, Fine IH, Hoffman RS. "Wavefront Technology in Cataract Surgery." Curr Opin Ophthalmol. 2004;15:56-60.

3. Tecnis Foldable Ultraviolet Light-Absorbing Posterior Chamber IOL [package insert]. Santa Ana, Calif. Advanced Medical Optics, Inc.; 2005.

Mark Packer, M.D., is clinical associate professor of ophthalmology at the University of Oregon Health & Science University and clinical study investigator for several Tecnis IOL studies. He serves as principal investigator for the Carl Zeiss Meditec MEL-80 Excimer Laser and was coordinating investigator for the FDA-monitored study of the Pharmacia aspheric Z9000 IOL. He is medical monitor for the investigation of the AMO Tecnis Multifocal IOL and also serves as principal investigator for the Visiogen Synchrony Dual Optic Accommodative Lens.