IOLs Compared: Visual Outcomes Using the AcrySof ReSTOR and ReZoom multifocal IOL

The implantation of multifocal intraocular lenses (IOLs) to aid in the recovery of accommodation and the restoration of near vision following cataract surgery is a technique that warrants closer attention and study. The technology is new, and limited data are available to most cataract patients and surgeons. Therefore, choosing an appropriate treatment plan is not straightforward. The aim of this article is to assist physicians and patients in making this choice by assessing the postoperative outcome of implanting 1 eye with an AcrySof ReSTOR IOL and the other eye with a ReZoom multifocal IOL as a means of maximizing the advantages of each.

IOL Design

Traditionally, the standard IOL implanted after cataract extraction has been a monofocal IOL with a single, fixed, focal length. This type of IOL is limited in its ability to provide good, unaided distance and near vision.^1-4 One way to address this problem is to implant a multifocal IOL such as the ReZoom multifocal IOL or a pseudoaccomodative IOL such as the ReSTOR. Such IOLs are also available using diffractive optics or with zones of differing refractive power.

The ReZoom is a second-generation, refractive, multifocal, acrylic IOL, which was approved for general use by the United States Food and Drug Administration (FDA) in March, 2005. It has a multifocal design similar to the silicone Array IOL. The 5 concentric, refractive zones provide multifocal vision: zones 1, 3, and 5 are distance dominant, while zones 2 and 4 are near dominant; an aspheric transition between zones provides balanced intermediate vision.

The second optical zone provides a sufficiently large near add, and the IOL’s Balanced View Optics technology provides expanded distance-dominant zones and light distribution for good vision under a broad range of lighting conditions. The near zones have a +3.5 add (IOL plane) resulting in about 2.8 diopters (D) at the spectacle plane. The ReZoom material is the same as the hydrophobic acrylic material used in the Sensar with OptiEdge IOL. The ReZoom IOL also has the OptiEdge design that provides 360 degrees of contact with the posterior capsule in order to decrease the incidence of posterior capsule opacification.

Meanwhile, the AcrySof ReSTOR pseudoaccommodative IOL is like 2 lenses in 1. One refractive lens is for distance, and the other lens, which is diffractive, is for near. It has an apodized, diffractive optic that is new to IOL design. Apodization refers to the gradual tapering of diffractive steps from the center to the outside edge of a lens for the purpose of creating a smooth transition of light between the distance, intermediate, and near focal points. Diffraction involves the bending or spreading of light to multiple focal points as it passes through the lens. This series of tiny steps in the center area work together to focus light for near through distance vision. The ReSTOR’s new optical design distributes light between near vision and distant vision to accommodate vision at a range of distances.

Methodology

The comparison study between the ReZoom and ReSTOR IOLs involved 44 eyes of 22 patients at a small, single site who had had a ReSTOR pseudoaccomodative IOL implanted in one eye and a ReZoom multifocal IOL implanted in the other. This prospective study included patients between the ages of 50 and 85 years with bilateral age-related cataract, no indication of existing ocular pathology, unsatisfactory correction with glasses, and less than 1.50 D of topography cylinder. Fourteen patients (63.6%) were women, and 8 (36.4%) were men.

To protect patient safety, patients were asked after the first eye surgery whether they wished to have the same lens type implanted in the second eye without being told what type it was. Exclusion criteria were previous ocular surgery, central endothelial cell count less than 1800 cells/mm 2, glaucoma or intraocular pressure (IOP) greater than 21 mm Hg, amblyopic eyes, retinal abnormalities, diabetes mellitus, steroid or immunosuppressive treatment, and connective tissue diseases.

Preoperative and postoperative evaluation included uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), spherical equivalent (SE), slitlamp biomicroscopy, applanation tonometry, fundus examination, B-scan biometry, specular microscope, and corneal topography. Clinical data were collected preoperatively and at 1 and 3 months postoperatively for each eye.

All patients were operated on in the same fashion. A 2.75 mm, self-sealing, clear corneal incision was made on the temporal side. A viscoelastic solution (Viscoat) containing sodium hyaluronate 3% and chondroitin sulfate 4% was used to reform and stabilize the surgical planes and to protect the endothelium. A 5.00 to 5.25 mm continuous curvilinear capsulorrhexis was initially performed with a 26-gauge needle and completed with forceps. The nucleus was removed without intraoperative complications such as posterior capsule rupture. Phacoemulsification was performed using the Infinite and/or Sovereign machine. All IOLs were inserted in the capsular bag with the injector system. The viscoelastic material was completely removed at the end of the procedure. No sutures were used in any case. Postoperative medication and follow-up periods were consistent for all patients.

Results

Table 1 displays a summary of preoperative patient measurements as well as visual outcomes that were taken during the 3-month follow-up. The group with the ReSTOR IOL had the same average uncorrected distance visual acuity (UCDVA) as the ReZoom group with no statistical difference between the 2 groups. The proportion of multifocal eyes achieving 20/40 or better UCDVA was 100% in both groups. However, the number of eyes achieving 20/25 or better was higher in the ReSTOR group (81.8%) when compared to the ReZoom group (68.1%). The mean near UCVA was Jaeger 1 (J1) and J2 in the ReSTOR and ReZoom groups respectively, and the average intermediate UCVA was J3 and J4 in the ReZoom and ReSTOR groups respectively. This difference demonstrates that the ReSTOR provides less improved intermediate function but better near vision. The ReZoom IOL may, therefore, be better suited for patients who must regularly engage in intermediate activities like viewing a computer.

UCDVA = uncorrected distance visual acuity. UCNVA = uncorrected near visual acuity. UCIVA = uncorrected intermediate visual acuity. BCVA = best corrected visual acuity. SE = spherical equivalent.

After a follow-up of 3 months, 7 patients (31.8%) described mild halos and starbursts at night. No other complaints were recorded. Overall, no significant difference between the eyes was observed, and no patient expressed a preference for one or the other lens. All patients were spectacle-independent for near and distance vision and very satisfied with their quality of vision without glasses.

Although studies have shown that relative spectacle independence for all of these multifocal lenses is quite similar,^1,7 there may be some difference in terms of quality of vision. Some patients are more sensitive to glare and halos and decreased contrast sensitivity.⁸ Slightly lower contrast sensitivity and increased halo perception by patients with multifocal IOLs compared to monofocal IOLs appear to be an acceptable compromise for enhanced near and distance vision.⁹

Summary

The results of the comparative study outlined above have shown that visual improvement can be achieved after implantation of multifocal and pseudoaccommodative lenses after cataract surgery. The majority of the postoperative results in both groups were similar, and the only statistically significant difference was observed in 2 conditions: the ReSTOR IOL achieved a better result than the ReZoom in near UCVA, and the ReZoom group achieved a better result than ReSTOR in the area of intermediate visual acuity.

Therefore, IOL selection should be based on patient preference and daily activity. If a patient with a ReZoom IOL in one eye is disappointed with its near function, it may be feasible to implant a ReSTOR IOL in the fellow eye, since it has a closer near vision add point. The opposite is also true. Overall, implantation of a pseudoaccomodative IOL such as ReSTOR or a multifocal IOL like ReZoom appears to be a safe and efficient procedure that results in a good refractive solution. Attention to detail in regard to proper patient selection, preoperative measurements, intraoperative technique, and postoperative management is the key to achieving excellent outcomes and improved patient acceptance of this effective technique. As with all refractive procedures, realistic expectations should be established prior to surgical intervention.

References

Author Disclosure

None of the authors has a financial or proprietary interest in any material or method mentioned.