INTRAOCULAR LENSES

Improving the Overall Quality of Vision for Presbyopes

A new study reveals the benefits of offering patients apodized diffractive optics.

By Stephen S. Lane, MD

The increasing popularity of presbyopia-correcting IOLs leaves little doubt to just how appealing the possibility of life without spectacles is to today's cataract patients. They want a full range of vision, and as surgeons, we shouldn't underestimate the importance of quality postoperative near vision in helping them achieve that goal.

Effects of Different Lens Designs

There are two types of presbyopia-correcting IOL technology: accommodative and multifocal. In the multifocal category, the diffractive design dominates the U.S. marketplace. However, the diffractive category breaks down further into lenses with full diffractive optics (Tecnis Multifocal IOL, Abbott Medical Optics) and those with apodized diffractive optics (AcrySof IQ ReSTOR IOL, Alcon Laboratories). The differences between the two designs can affect overall quality of vision.

The apodized diffractive optic distributes light energy to the retina differently than the full diffractive optic. With apodization, the diffractive step heights are gradually reduced and the rings are placed closer together from the center of the lens to the periphery. This improves quality of vision and provides for an energy distribution that favors distance vision. Furthermore, the apodized optic is refractive in the periphery (beyond 3.6 mm), and the refractive area of the optic is dedicated exclusively to distance vision. As a result, when the pupil enlarges, more light energy is directed to a distance focal point. This tends to produce fewer visual disturbances than an optic that is fully diffractive and helps to preserve contrast sensitivity as well.

The diffractive lens options available today also differ in the amount of near add power they provide. The Tecnis Multifocal IOL, for example, provides +4.0D add power, as does the AcrySof IQ ReSTOR IOL +4.0D. By looking at the binocular defocus curves generated from patient data for these two lenses, we see they perform similarly at near and intermediate distances^1,2 (Figures 1 and 2).

Figures 1 and 2. As indicated by binocular defocus curves generated from patient data in FDA clinical trials, diffractive presbyopia-correcting IOLs with the same +4.0D add power perform similarly at near.

In an effort to provide patients with an even wider range of clear near vision, the AcrySof IQ ReSTOR IOL with a +3.0D add was developed. Results of a randomized multicenter clinical trial showed that the +3.0D add power achieved this goal without compromising overall quality of vision.³ The lens moves the best distance for near vision 6-7 cm farther out and provides better depth of focus compared with the +4.0D add power lens (Figure 3). Based on its apodized design and available data, we might expect the AcrySof IQ ReSTOR +3.0D IOL to be the diffractive-style lens capable of providing the greatest number of patients with the widest range of spectacle-free vision.

Figure 3. The AcrySof IQ ReSTOR IOL with +3.0D add power provides a wider range of clear near vision and moves the best distance for near vision 6-7 cm farther out than the same lens with a +4.0D add power.

In the clinical trial comparing the +3.0D and +4.0D lens models, patient satisfaction was high. Six months after surgery, more than 93% of patients who were implanted with the +3.0D model reported that would have the same implant again.²

Apodized Diffractive vs. Accommodating IOL

I have presented the results of a prospective, multicenter, subject-masked study comparing the AcrySof IQ ReSTOR +3.0D IOL with the Crystalens HD accommodating IOL (Bausch + Lomb).⁴ In the study, patients with bilateral cataracts and less than 1.0D of pre-operative corneal astigmatism were randomized to receive either the ReSTOR (33 patients) or Crystalens IOL (27 patients).

At 3 months, the apodized diffractive AcrySof IQ ReSTOR +3.0D IOL provided a better near-vision result than the Crystalens IOL. With best distance correction, mean binocular near visual acuity at 40 cm — the average distance at which most patients feel comfortable reading — was significantly better in the ReSTOR IOL group (p<0.0001) (Figure 4). This represented an advantage of approximately three Snellen lines of visual acuity. Patients who received ReSTOR IOLs achieved mean binocular near visual acuity with distance correction in place between 20/20 and 20/25 at 40 cm, while patients who received Crystalens IOLs achieved near acuity between 20/40 and 20/50.

Figure 4. In a recent study comparing the AcrySof IQ ReSTOR +3.0D IOL with the Crystalens HD accommodating IOL, mean binocular near visual acuity at 40 cm was approximately 3 Snellen lines better with the ReSTOR lens (p<0.0001).

Because not all patients feel comfortable reading and performing other near tasks at 40 cm, visual acuity at patients' preferred near distance was also evaluated. On this parameter, too, patients in the ReSTOR IOL group fared better (Figure 5). The preferred near distance was significantly farther from the eye with Crystalens than with the ReSTOR IOL, 51 cm +/− 10 cm vs. 38 +/− 7 cm (P<0.0001), and mean distance-corrected binocular visual acuity at the preferred near distance was about 1.5 Snellen lines better among patients who received the ReSTOR IOL (p=0.003). At the preferred near distance, visual acuity was between 20/20 and 20/25 with the ReSTOR IOL and around 20/32 with the Crystalens.

Figure 5. In a recent study comparing the AcrySof IQ ReSTOR +3.0D IOL with the Crystalens HD accommodating IOL, mean binocular near visual acuity at 40 cm was approximately three Snellen lines better with the ReSTOR lens (p<0.0001).

The quality of the near distance vision achieved by patients in the AcrySof IQ ReSTOR IOL group was reflected in their rate of spectacle independence (Figure 6).When asked about spectacle independence on a questionnaire, 83% reported never needing eyeglasses. The rate was significantly higher (p=0.0025) than the 38% of patients in the Crystalens group who reported no need for eyeglasses.

Figure 6. Following bilateral implantation with AcrySof IQ ReSTOR +3.0D IOLs in a recent study, 83% of patients reported that they never wear spectacles.

In addition to near vision and spectacle independence, this study evaluated the predictability of refractive outcomes, which is another aspect of presbyopia-correcting IOLs important to surgeons and patients. Manifest refraction spherical equivalent (MRSE) was significantly more predictable (p<0.001) with the AcrySof IQ ReSTOR +3.0D IOL than with the Crystalens (Figure 7). At 3 months, approximately 87% of patients in the ReSTOR IOL group were within 0.5D of the intended refractive target and 100% were within 1.0D. In the Crystalens group, 64% were within 0.5D of the intended refractive target and 79% were within 1.0D.

Figure 7. In a recent study, postoperative manifest refraction spherical equivalent was more predictable with the AcrySof IQ ReSTOR +3.0D IOL than with the Crystalens HD IOL (p<0.001).

Leveraging Technology to Maximize Outcomes

Achieving good results is a multifaceted endeavor that requires an understanding of the current technologies and how they can be expected to perform in clinical practice, detailed doctor-patient communication to determine which patients are good candidates and which are not, and an ability to match lens technologies with the individual vision needs of patients.

Obtaining positive results also requires a commitment to precise preoperative measurements for surgical planning and a realization that patients are paying out-of-pocket and therefore have little or no tolerance for unsatisfactory outcomes. Ensuring that we choose the IOLs that allow us to deliver the best possible range of vision for the largest number of patients — and hitting the refractive target — are the best ways to attain early and continued success. nMD

REFERENCES

1. Tecnis Multifocal Package Insert.
2. AcrySof IQ^® ReSTOR^® Package Insert.
3. 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.
4. Lane SS. Visual acuity and spectacle wear with presbyopia-correcting intraocular lenses. Poster presentation at ISRS Annual Meeting, October 2010, Chicago, IL.