Multifocal Versus Monofocal IOLs: No Clear Winner in Small Study
Despite the excellent restoration of visual acuity and good biocompatibility available with current monofocal foldable IOLs, accommodation is still insufficient in monofocal pseudophakic eyes. Therefore, patients remain presbyopic after surgery. The introduction of multifocal IOLs has partly solved this problem.1-4
Current studies addressing the combined surgical treatment of cataract and presbyopia focus on the comparison of multifocal IOL models; however, these studies usually lack comparison to the gold standard of monofocal IOLs. We conducted a clinical trial to address this issue. We compared a standard monofocal IOL (CeeOn Edge; Advanced Medical Optics, Inc., Santa Ana, California; no longer available), an aspheric monofocal IOL (Tecnis Z9000; Advanced Medical Optics, Inc.), a refractive multifocal IOL (AA50 Array 2; Advanced Medical Optics, Inc.; no longer available), and a diffractive multifocal IOL (Tecnis ZM001; Advanced Medical Optics, Inc.). The optimized aspheric design of the Tecnis ZM001 promises to compensate for the loss of contrast sensitivity that is typical of other spherical multifocal IOLs.
The primary goal of the study was to answer three questions: (1) to what extent does the use of multifocal IOLs enable patients to manage everyday life without spectacles, (2) do lenses with an optimized aspheric design offer a significant advantage in contrast sensitivity, and (3) is the use of standard monofocal IOLs still warranted?
This randomized, standardized, controlled, observer-blinded clinical trial included 101 patients with bilateral cataract and without other clinically significant ocular pathologies. Patients scheduled for routine phacoemulsification in both eyes were recruited prospectively from the outpatient center at the University Eye Clinic, Paracelsus Medical University of Salzburg, Austria.
All patients underwent clinical examination by two independent ophthalmologists and gave written informed consent. Inclusion criteria were bilateral cataract, minimum preoperative BCVA of at least 0.1 on the Early Treatment of Diabetic Retinopathy Study (ETDRS) scale, sufficient preoperative retinal examination, and a minimal retinal visual acuity of 0.63 indicating a good postoperative visual potential.
Further inclusion criteria were patients aged 60 years or older, axial length between 22 and 26 mm, preoperative corneal astigmatism less than 1.00 D as measured with corneal topography (Keratron Scout; Optikon 2000 Industrie, Rome), target refraction of emmetropia, biometry done with the IOLMaster (Carl Zeiss Meditec AG, Jena, Germany), and IOL calculation done with the SRK-T formula.
Exclusion criteria were diabetic retinopathy, maculopathy, suspect amblyopia, corneal scars larger than 1 mm, corneal astigmatism greater than 1.00 D, pseudoexfoliation syndrome, glaucoma, preoperative myopia or hyperopia greater than 6.00 D, optical atrophy, ocular trauma, or previous ocular surgery.
G¸nther Grabner, MD, performed phacoemulsification and posterior chamber IOL implantation in both eyes of each patient within 4 weeks (range, 3–6 weeks) for all patients. At 3 and 12 months postoperatively, we used the VSCR-CST-1800 view-in tester (Ginsburg Box; Vision Science Research Corp., San Ramon, California) to evaluate binocular contrast sensitivity and distance BCVA under mesopic (3 cd/m²) and photopic (85 cd/m²) conditions.
Binocular reading acuity and reading speed were measured using the standardized Radner Reading Charts with and without best distance correction to test everyday life performance. The results were evaluated as per protocol analysis.
LENS CHARACTERISTICS
All of the IOLs that we tested have different characteristics. The CeeOn Edge 911A was a standard foldable monofocal silicone lens for in-the-bag implantation. The Tecnis Z9000 is an advancement of the previously available CeeOn Edge. It is a three-piece lens with a 6-mm equiconvex square-edged silicone optic and 6° angulated-C polyvinylidene fluoride haptics. The innovative aspect of the Tecnis Z9000 is its anterior prolate surface that results in a spherical aberration of -0.27 µm; this wavefront aberration is for a 6-mm pupil.5 The Tecnis ZM001 is a diffractive, foldable, silicone, multifocal IOL with an optic diameter of 6 mm. The diffractive pattern creates two focal points that are 4.00 D apart. The main advantage of this lens is its additional aspheric modified prolate anterior surface that reduces spherical aberration. This aspheric design is postulated to compensate for the loss in contrast sensitivity found in a standard diffractive multifocal IOL. The AA50 Array 2 was a foldable silicone multifocal lens with a 6-mm optic. It had a refractive design with five concentric zones. Zones one, three, and five were distant-dominant and two and four were near-dominant with 3.50 D add.
Lens types for implantation were randomly chosen by chance permutation. Because of ethical considerations, patients were informed about the scheduled lens types (ie, monofocal or multifocal IOL), but they did not know which one of the IOLs (ie, CeeOn Edge [no longer available], Tecnis Z9000, AA50 Array 2 [no longer available], ZM001) would be implanted.
RESULTS
All four groups reached emmetropia (±0.50 D). Distance BCVA (after 3 and 12 months under photopic and mesopic conditions) was measured with the ETDRS chart and reached a median of 20/20 in every group.
There was a trend for both of the multifocal IOL models to show a wider range of visual acuity under mesopic conditions compared with the monofocal IOLs, but in this sample size statistical significance was not reached.
To our surprise, the aspheric IOLs did not show any clear advantage in contrast sensitivity. Results with the Tecnis Z9000 equalled those with the CeeOn Edge (no longer available). It is possible that the advantage of an aspheric IOL may be noticed in a bigger sample size (ie, more than 25 patients in each group). In this study, however, the benefit can be assumed to be minor.
The multifocal IOLs tended to show slightly reduced contrast sensitivity with a wider distribution in mesopic conditions, but again, the differences were too small in our surgical series to be statistically significant. In short: There was no big winner and no big loser.
Concerning reading acuity with best distance correction, our results showed a clear benefit with the diffractive Tecnis ZM001. Patients reached a distance-corrected near visual acuity of medium logRAD 0.15, which ably demonstrates the functioning of the diffractive design.
When testing distance-corrected near visual acuity, the refractive AA50 Array 2 lens (no longer available) did not perform significantly better than the two monofocal IOLs. We assume that the rather far-dominant design of the AA50 Array 2 and its smaller near add as compared with the Tecnis ZM001 are the main reasons for this performance. Despite the clearly better outcome with the diffractive Tecnis lens, we were amazed to find that patients reached the newspaper reading equivalent of logRAD 0.4, even with standard monofocal IOLs.
Once more, this demonstrates that the optimal IOL for our patients should clearly be an individual decision on a case-by-case basis. The patient's way of life, including personal driving, visual requirements, and everyday duties, must be taken into consideration.
Alois Dexl, MD, MSc, practices at the University Eye Clinic, Paracelsus Medical University of Salzburg, Austria. Dr. Dexl states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +43 662 4482 57228; fax: +43 662 4482 3703; A.Dexl@salk.at.
Günther Grabner, MD, is Professor of Ophthalmology and Chairman at the University Eye Clinic, Paracelsus Medical University of Salzburg, Austria. Professor Grabner states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +43 662 4482 3701; fax: +43 662 4482 3724; G.Grabner@salk.at.
Wolfgang Hitzl, PhD, MSc, is a statistician at the University Eye Clinic, Paracelsus Medical University of Salzburg, Austria. Professor Hitzl states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +43 662 4482 3702; fax: +43 662 4482 3703; W.Hitzl@salk.at.
Elisabeth Kramar, MD, practices at the University Eye Clinic, Paracelsus Medical University of Salzburg, Austria. Dr. Kramar states that she has no financial interest in the products or companies mentioned. She may be reached at tel: +43 662 4482 57375; fax: +43 662 4482 3703; E.Kramar@salk.at.
Patrick Marvan, MD, practices at the University Eye Clinic, Paracelsus Medical University of Salzburg, Austria. Dr. Marvan states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +43 662 4482 58448; fax: +43 662 4482 3703; P.Marvan@salk.at.
Max Rasp, MD, practices at the University Eye Clinic, Paracelsus Medical University of Salzburg, Austria. Dr. Rasp states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +43 662 4482 57436; fax: +43 662 4482 3703; M.Rasp@salk.at.
Orang Seyeddain, MD, practices at the University Eye Clinic, Paracelsus Medical University of Salzburg, Austria. Dr. Seyeddain states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +43 662 4482 57372; fax: +43 662 4482 3703; O.Seyeddain@salk.at.
Ready to Claim Your Credits?
You have attempts to pass this post-test. Take your time and review carefully before submitting.
Good luck!
