INTRAOCULAR LENSES

Comparing Diffractive Multifocal IOLs

An ongoing study reveals promising results about apodized +3.0 D lenses.

By Kerry D. Solomon, MD

When establishing yourself in practice, you must get up to speed quickly on surgical solutions for presbyopes who have cataracts in order to meet the demands of the aging Baby Boomer population. I've found that the apodized diffractive optics of the AcrySof IQ ReSTOR IOL (Alcon) significantly improve patient satisfaction, so I believe the lenses are worthy of consideration and recommendation to patients.

To help demonstrate the benefits of this lens, I'm participating in a study comparing the +3.0 D AcrySof IQ ReSTOR IOL to the Tecnis +4.0 D Multifocal IOL (Abbott Medical Optics). So far, the results look promising for the ReSTOR IOL.

Here, I'll share the 1-month results of this ongoing trial and comment on the implications of our findings in practice.

Benefits of the +3.0 D Lens

Unlike full optic diffractive optics, the optics created by apodization improve the distribution of light energy directed toward the retina. The diffractive step heights are gradually reduced and blended as they progress from the center of the lens to the periphery. This improves the crispness of vision and reduces light scatter, aberrations and visual disturbances, compared to the effects created by other lens designs, especially in low light.

The slightly changing concentric apodized steps of the AcrySof IQ ReSTOR IOL extend from the center of the IOL to an outer ring that is 3.6 mm in diameter. Beyond these rings, the lens provides a refractive region dedicated to vision distance. In this region, light is directed to a distance focal point for a larger pupil diameter, minimizing visual disturbances.

In the past, I've offered patients the +4.0 D AcrySof IQ ReSTOR IOL, along with other IOLs, depending on objective examination findings and the patient's expressed needs. The recent introduction of the +3.0 D AcrySof IQ ReSTOR IOL has expanded my offerings. The +3.0 D lens provides clear vision at more distances and allows many patients to be spectacle-free while working at their computers, performing daily tasks and participating in activities that require visual acuity at varying intermediate distances.

In essence, the +3.0 D AcrySof IQ ReSTOR IOL helps my patients avoid a difficult choice. They no longer need to choose between optimal distance vision and reading glasses on the one hand and monovision, which sacrifices depth perception, on the other hand. AcrySof IQ ReSTOR +3.0 D IOL provides excellent distance vision and also comfortable near and intermediate vision.

Baseline Data

Before beginning our study, I considered the differences between the +3.0 D AcrySof IQ IOL and the +4.0 D AcrySof IQ IOL. I knew the AcrySof IQ ReSTOR IOL with a +3.0 D add had been released in 2009 to provide patients with a wider range of clear near vision. Results of a randomized multicenter clinical trial showed that the +3.0 D add power achieved this goal without compromising overall quality of vision.¹

The lens was found to move the best distance for near vision 6-7 cm farther out and to provide better depth of focus compared to the +4.0 D AcrySof IQ IOL. In the clinical trial comparing the +3.0 D and +4.0 D lens models, patient satisfaction was high for the +3.0 D lens, as expected. Six months after surgery, more than 93% of patients who were implanted with the +3.0 D model reported they would choose the same implant again.

The AcrySof IQ ReSTOR IOL +3.0 D was designed to provide doctors and patients with an additional choice of add power. The +3.0 D add power (~ +2.5 D at the spectacle plane) was achieved by reducing the number of diffractive steps from 12 to 9 and slightly widening the step spacing. As a result, intermediate vision improves and the focal point for the clearest near vision is 2.4-2.8 inches (~ 6-7 cm) farther out than with the AcrySof IQ ReSTOR IOL +4.0 D.

From about 13-28 inches, patients have high-quality vision. They can work on the computer and accomplish other tasks in that range without spectacles.

Figure 1. The AcrySof IQ ReSTOR IOL +3.0 D IOL demonstrated favorable results over the Tecnis +4.0 D Multifocal IOL when near and intermediate vision were measured 1 month after surgery.

Figure 2. One month after surgery, patients who received the AcrySof IQ ReSTOR IOL +3.0 D implantations were consistently more satisfied than those who received the Tecnis +4.0 D Multifocal IOL implantations.

Like the +4.0 D add model, the +3.0 D lens is aspheric, so it compensates for positive corneal spherical aberration, which enhances image quality compared with spherical lenses. The combination of the asphericity, +3.0 D add power and apodization means there's very little trade-off when striving to achieve a wider range of useful vision. Although patients can experience glare and halo with any IOL, the AcrySof IQ ReSTOR IOL +3.0 D minimizes visual disturbances.

Unlike the ReSTOR IOL, the Tecnis offers full diffractive optics out to the rim of the IOL, which can cause nighttime glare and halos per their DFU information provided on the Tecnis Multifocal website.

ReSTOR IOL vs. Tecnis

With these factors in mind, we've begun the first, prospective, randomized comparison between the AcrySof IQ ReSTOR IOL +3.0 D and the Tecnis +4.0 D Multifocal IOL. In the trial, 62 cataract surgery patients were randomly assigned to bilateral implantation with one of these lenses. A 1-month post-operative follow up has been recorded and a 3-month follow-up is planned.

For distance, postop acuity for both lenses was found to be acceptable. The AcrySof IQ ReSTOR IOL +3.0 D decreased logMAR values by a mean of 0.11 to 0.05, with a standard deviation of 0.17 (preop) to 0.14 (postop). The Tecnis +4.0 D Multifocal IOL decreased logMAR values from a mean of 0.11 to 0.07. The standard deviation went from 0.17 (preop) to 0.12 (postop). The differences between the two lenses at distance were determined to be statistically insignificant.

At intermediate distance, the P values (<0.001 preop to <0.05 postop) statistically favored AcrySof IQ ReSTOR IOL +3.0 D, which reduced the mean logMAR score from 0.31 to 0.24. Standard deviation was 0.14 both before and after surgery for this lens. The Tecnis +4.0 D Multifocal IOL actually increased the mean logMar reading from 0.19 to 0.34 postop. Standard deviation was 0.14 preop and 0.20 postop.

Near vision results also favored AcrySof IQ ReSTOR IOL +3.0 D postoperatively. Mean LogMAR scores dropped from 0.16 to 0.08. Standard deviation was 0.12 preop and 0.11 postop. The mean logMAR scores for Tecnis +4.0 D Multifocal IOL increased from 0.15 preoperatively to 0.17 postop, with standard deviations of 0.12 and 0.09, respectively (Figure 1).

Subjective Findings

Following study protocol, we interviewed all patients 1 month after surgery to gather patient-reported outcomes. Using a scoring system called VISTAS rating, patients rated their ability to perform a variety of visual tasks without spectacles. They rated the tasks on a scale of 1 (no difficulty) to 5 (extremely difficult). The patients who received AcrySof IQ ReSTOR IOL +3.0 D implantations were consistently more satisfied (Figure 2). Higher ratings were found in the following areas:

■ Effectively and safely perform near tasks at less than 2 feet
■ Effectively and safely perform intermediate tasks (2 to 3 feet)
■ Drive confidently and safely at night (less than 2 feet distance).

It is important to note that the results of this study are preliminary, based on findings after 1 month. We look forward to seeing and presenting the 3-month data.

Differences in Lens Design

Both of these lenses would appear to have distinct advantages and disadvantages. The design of the ReSTOR lens suggests it might not allow young patients with larger pupils to tolerate reading in low light. Theoretically, the challenge would arise when their vision strayed into the monocular part of the lens, beyond the 3.5-mm area that contains the lens's diffractive steps. However, as I mentioned, the concentric rings and monofocular part of the AcrySof IQ RESTOR IOL combine to provide better quality distance vision, minimizing halos and glare, even in low illumination.

Meanwhile, because its diffractive design extends out to the periphery, the Tecnis presents a separate challenge, degrading sharpness of distance vision. In theory, then, most patients should notice more prominent night vision symptoms when they receive Tecnis implantations.

We've always relied on presbyopic patients' preferences when determining the best IOL solutions. If patients don't mind using readers in low light, as is the case with most of the patients in my practice, then the ReSTOR lens meets their needs. Other patients may not want to use spectacles and may not be bothered by halo and glare at night, so these patients may have been best suited for the Tecnis.

As we've found in this study on a preliminary basis, however, these notions about ideal lenses for patient types may be changing. We found what we expected in multifocal patients. Patients noticed night vision symptoms more prominently in the Tecnis +4.0 D Multifocal IOL than in the AcrySof IQ ReSTOR IOL +3.0 D lens. What was a surprise, however, was that all patients in both lens groups noted decreased reading ability in low illumination. The incremental improvement in low illumination didn't make an impression.

+3.0 D Optic vs. +4.0 D Optic

One would expect quality near vision with +3.0 D lens and also expect a +4.0 D add to provide more magnification, permitting patients to see finer print at nearer distances. As the objective results show, we've found what we expected for near distance. Patients were able to read fine print. However, the AcrySof IQ ReSTOR IOL +3.0 D provided excellent distance out to 16 to 18 inches, about 2 inches further than the effect achieved with the Tecnis +4.0 D Multifocal IOL.

Near is often too close with a +4.0 D optic. The defocus curves of the Tecnis +4.0 D Multifocal IOL and the AcrySof IQ ReSTOR IOL +3.0 D are nearly identical because of their optics. But the AcrySof IQ ReSTOR IOL +3.0 D lens provides a more functional reading distance.

It's becoming increasingly clear that we haven't seen a trade-off in the AcrySof IQ ReSTOR IOL +3.0 D. There's no need to forego a patient's ability to read fine print in exchange for improved intermediate and distance vision. Besides offering quality near vision for reading, the AcrySof IQ ReSTOR IOL +3.0 D provides more natural and functional vision at intermediate distances than we've found in the AcrySof IQ ReSTOR IOL +4.0 D and the Tecnis +4.0 D Multifocal IOL.

This is the case when we measure objectively and also when we asked patients about their postop experiences. They report more ease with daily tasks at 2 to 3 feet away.

Promising Preliminary Results

Presbyopic patients in our practice have expressed a preference for optimal vision at near, intermediate and distance. I believe this trend will grow in the years ahead, as technology advances and patient expectations increase. nMD

REFERENCE

1. 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.