Multifocal versus monofocal intraocular lenses for age-related cataract patients: a system review and meta-analysis based on randomized controlled trials

  • Kai Cao
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • David S. Friedman
    Affiliations
    Dana Center for Preventive Ophthalmology, The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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  • Shanshan Jin
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Mayinuer Yusufu
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Jingshang Zhang
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Jinda Wang
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Simeng Hou
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Guyu Zhu
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Bingsong Wang
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Ying Xiong
    Affiliations
    Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Jing Li
    Affiliations
    Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Xiaoxia Li
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Hailong He
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Lijing Chai
    Affiliations
    Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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  • Xiu Hua Wan
    Correspondence
    Corresponding author: Xiu Hua Wan, MD, Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, No. 17, Hougou Ally, Dongcheng District, Beijing 100005, China.
    Affiliations
    Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital of Capital Medical University, Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
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Open AccessPublished:March 05, 2019DOI:https://doi.org/10.1016/j.survophthal.2019.02.012

      Abstract

      We compare multifocal intraocular lenses (MFIOLs) to monofocal IOLs for visual acuity (VA), contrast sensitivity, and adverse events using data from 21 randomized controlled trials with 2951 subjects. There was no statistical difference between uncorrected distance VA and corrected distance VA. Compared with monofocal IOLs, MFIOLs showed a better performance on uncorrected intermediate VA measured at 60 cm and uncorrected near VA; the mean differences were -0.06 (95% confidence interval [CI]: -0.10, -0.03) and -0.13 (95% CI: -0.20, -0.07). Distance-corrected intermediate VA and distance-corrected near VA were measured wearing distance correction. MFIOLs performed better than monofocal IOLs on distance-corrected intermediate VA at 60 cm and distance-corrected near VA; the mean differences were -0.09 (95% CI: -0.12, -0.06) and -0.31 (95% CI: -0.43, -0.19). The contrast sensitivity of the MFIOL group was lower than that of the monofocal IOL group; mean difference was -0.06 (95% CI: -0.11, -0.02). More patients were spectacle free in the MFIOL group; the risk ratio was 2.86 (95% CI: 1.73, 4.73). More patients were troubled by glare and halos in the MFIOL group; the risk ratios were 1.91 (95% CI: 1.24, 2.95) and 3.08 (95% CI: 2.11, 4.49). We conclude that, compared with monofocal IOLs, MFIOLs give patients better near vision and intermediate vision at 60 cm, both corrected and uncorrected. Patients undergoing MFIOLs implantation are more likely to be spectacle free but have a higher risk of glare, halos, and lower contrast sensitivity.

      Keywords

      1. Introduction

      Modern cataract surgery entails removing the crystalline lens and replacing it with an artificial intraocular lens (IOL), a safe and effective procedure.
      • Dong F.
      • Zhao G.Q.
      • Wang Q.
      • et al.
      Clinical observation of visual quality after implantation of toric intraocular lens.
      • Luo S.
      • Lin Z.
      Stereopsis after implantation of intraocular lens in patients under 40 years old with unilateral cataract.
      • Shen Z.
      • Lin Y.
      • Zhu Y.
      • et al.
      Clinical comparison of patient outcomes following implantation of trifocal or bifocal intraocular lenses: a systematic review and meta-analysis.
      Since the first IOL appeared in London in 1950s,
      • Ridley H.
      Further observations on intraocular acrylic lenses in cataract surgery.
      • Ridley H.
      Intra-ocular acrylic lenses; a recent development in the surgery of cataract.
      many kinds of IOLs, such as monofocal, bifocal, trifocal, and so forth, have been developed. Monofocal IOLs provide patients with good vision, but only at 1 focal distance. Many patients receiving monofocal IOLs desire clearer near vision. Multifocal intraocular lenses (MFIOLs) with multiple focal distances have been FDA-approved since 1997.
      • Pearce J.L.
      Multifocal intraocular lenses.
      MFIOLs, however, are not perfect, with reports of reduced contrast and increased risk of glare and halos. Many researchers had tried to evaluate the advantages and disadvantages of different IOLs. In 2008, Li and coworkers
      • Li N.
      • Chen X.
      • Zhang J.
      • et al.
      Effect of AcrySof versus silicone or polymethyl methacrylate intraocular lens on posterior capsule opacification.
      compared IOLs made of silicone and polymethyl methacrylate; however, the focus of the comparison was different materials. In 2014, Leung and coworkers
      • Leung T.G.
      • Lindsley K.
      • Kuo I.C.
      Types of intraocular lenses for cataract surgery in eyes with uveitis.
      assessed 4 types of IOLs, but the target population was uveitis patients, and only 4 studies were included. Recently, 2 systematic reviews on IOLs published by Yoon and coworkers and Xu and coworkers
      • Yoon C.H.
      • Shin I.
      • Kim M.K.
      Trifocal versus bifocal diffractive intraocular lens implantation after cataract surgery or refractive lens exchange: a meta-analysis.
      • Xu Z.
      • Cao D.
      • Chen X.
      • et al.
      Comparison of clinical performance between trifocal and bifocal intraocular lenses: A meta-analysis.
      compared bifocal and trifocal IOLs. Calladine and coworkers
      • Calladine D.
      • Evans J.R.
      • Shah S.
      • et al.
      Multifocal versus monofocal intraocular lenses after cataract extraction.
      and De Silva and coworkers
      • de Silva S.R.
      • Evans J.R.
      • Kirthi V.
      • et al.
      Multifocal versus monofocal intraocular lenses after cataract extraction.
      compared multifocal and monofocal IOLs, respectively, in 2008 and 2016,
      • Percival S.P.B.
      • Setty S.S.
      Prospectively randomized trial comparing the pseudoaccommodation of the AMO ARRAY multifocal lens and a monofocal lens.
      • Rossetti L.
      • Carraro F.
      • Rovati M.
      • et al.
      Performance of diffractive multifocal intraocular lenses in extracapsular cataract surgery.
      but neither evaluated distance-corrected intermediate VA outcome. Besides, they included 2 kinds of MFIOLs that were no longer in use.
      It remained controversial whether MFIOLs were superior to monofocal IOLs. Our systematic review and meta-analysis provides an updated assessment of the VA, contrast sensitivity (CS), and adverse outcomes of MFIOLs and monofocal IOLs implantation in elderly cataract patients based on randomized controlled trials.

      2. Materials and methods

      2.1 Inclusion criteria

      To assess only high-quality evidence, we only included randomized controlled trials. The intervention measures were monofocal IOLs implantation and MFIOLs implantation. The target population was cataract patients aged 50 years or older.

      2.2 Databases and search strategy

      We searched databases of Pubmed, Science Direct, the Chinese National Knowledge Infrastructure, and the Wanfang Database. We used the following terms or their combinations to conduct the literature search: randomization, randomized, randomly, trial, comparison, monofocal, multifocal, IOLs, intraocular lenses. The full search strategy was shown in Method of Literature search part. We restricted the publication date to be between January 1, 1998 and December 31, 2017.

      2.3 Outcomes

      • 1.
        Visual acuity
      We compared both corrected and uncorrected binocular VA, including distance VA, intermediate VA, and near VA. We only extracted logMAR VA.
      For the measurement of distance VA, 5 studies used Early Treatment for Diabetic Retinopathy Study (ETDRS) acuity charts
      • Ferris F.R.
      • Kassoff A.
      • Bresnick G.H.
      • et al.
      New visual acuity charts for clinical research.
      (Precision Vision, IL). One study used Bailey-Lovie logMAR
      • Bailey I.L.
      • Lovie J.E.
      The design and use of a new near-vision chart.
      letter charts, and 1 study did not report the measurement tool. For the measurement of intermediate VA, 2 studies used EDTRS, 1 study used Snellen acuity with Sloan optotypes (ACP-8 Auto Chart Projector, Topcon Europe BV, Milano, Italy), and 1 study did not report the measurement tool. For the measurement of near VA, 1 study used Rosenbaum near acuity card, 2 studies used Bailey-Lovie logMAR word reading acuity charts, 2 studies used EDTRS, and another 2 studies did not mention the measurement tool.
      • 2.
        Spectacle independence (glasses free after IOLs implantation)
      • 3.
        Contrast sensitivity
      For the measurement of contrast sensitivity, 4 studies used Pelli-Robson contrast sensitivity chart to perform measurement, 2 studies used CSV-1000 (which presents sine wave gratings at 3, 6, 12, and 18 cycles/degree frequencies), and 1 study used the Vision Contrast Test System.
      • Haaskjold E.
      • Allen E.D.
      • Burton R.L.
      • et al.
      Contrast sensitivity after implantation of diffractive bifocal and monofocal intraocular lenses.
      • Jindra L.F.
      • Zemon V.
      Contrast sensitivity testing: a more complete assessment of vision.
      • 4.
        Adverse events (glare and halos)

      2.4 Data extraction

      We only extracted data measured at the last follow-up time. For categorical data, we extracted the number of events of each treatment group, such as the number of spectacle independence and the number of glare and halos. For continuous data like VA, the mean values and standard deviations were extracted.

      2.5 Assessment on risk of bias and paper quality

      We applied the risk of bias tool recommended by the Cochrane Collaboration to evaluate the risk of bias of included studies from 6 aspects: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessors, incomplete outcome data, selective outcome reporting. The risk of bias would be classified into high level, low level, or unclear according to each study's description.

      2.6 Data synthesis and statistical analysis

      We used mean deviation (MD—mean value of MFIOLs minus mean value of monofocal IOLs) with 95% confidence interval (CI) to estimate continuous outcomes, and risk ratio (RR) with 95% CI to estimate categorical outcomes. We conducted all the analyses using open source R program (version 3.4.4). The significance level was 0.05, two tailed.
      For studies with more than 2 MFIOLs treatments, we combined mean values and standard deviations of each MFIOLs group according to Formula (1) and Formula (2), respectively. For categorical data, we added up the number of events of each MFIOLs group; all aforementioned statistical methods were recommended by the Cochrane handbook. We applied funnel plot and Egger's test to check publication bias.
      • Egger M.
      • Davey S.G.
      • Schneider M.
      • et al.
      Bias in meta-analysis detected by a simple, graphical test.
      When funnel plot showed asymmetry, we conducted a trim-and-fill analysis
      • Duval S.
      • Tweedie R.
      Trim and fill: A simple funnel-plot-based method of testing and adjusting for publication bias in meta-analysis.
      as a way to adjust the effect for funnel plot asymmetry.
      N1M1+N2M2N1+N2
      (1)


      ([N]11)SD12+([N]21)SD12+N1N2N1+N2(M12+M22+2M1M2)N1+N21
      (2)


      2.7 Assessment on heterogeneity

      Before calculating the pooled MD of pooled RR, we assessed the heterogeneity across studies firstly using I2 statistic. If I2 were above 50%, a random-effects model (DerSimonian-Laird method) would be applied to do the meta-analysis,
      • Higgins J.P.
      • Thompson S.G.
      • Deeks J.J.
      • et al.
      Measuring inconsistency in meta-analyses.
      • Ioannidis J.P.
      • Patsopoulos N.A.
      • Evangelou E.
      Heterogeneity in meta-analyses of genome-wide association investigations.
      subgroup analysis, and sensitivity analysis. Otherwise, we used a fixed-effects model (Mantel-Haenszel method).
      • He C.
      • Ma H.
      Effectiveness of trigger point dry needling for plantar heel pain: a meta-analysis of seven randomized controlled trials.
      • Mantel N.
      • Haenszel W.
      Statistical aspects of the analysis of data from retrospective studies of disease.

      3. Results

      In this meta-analysis, a total of 21 randomized controlled trials and 2951 subjects were included.
      • Chen T.
      • Gao Y.
      • Liu X.L.
      • et al.
      Visual outcome with the array multifocal intraocular lens.
      • Cillino S.
      • Casuccio A.
      • Di Pace F.
      • et al.
      One-Year Outcomes with New-Generation Multifocal Intraocular Lenses.
      • Harman F.E.
      • Maling S.
      • Kampougeris G.
      • et al.
      Comparing the 1CU Accommodative, Multifocal, and Monofocal Intraocular Lenses: A Randomized Trial.
      • Javitt J.C.
      • Steinert R.F.
      Cataract extraction with multifocal intraocular lens implantation: A multinational clinical trial evaluating clinical, functional, and quality-of-life outcomes.
      • Ji J.
      • Huang X.
      • Fan X.
      • et al.
      Visual performance of Acrysof ReSTOR compared with a monofocal intraocular lens following implantation in cataract surgery.
      • Kamlesh
      • Dadeya S.
      • Kaushik S.
      Contrast sensitivity and depth of focus with aspheric multifocal versus conventional monofocal intraocular lens.
      • Labiris G.
      • Giarmoukakis A.
      • Patsiamanidi M.
      • et al.
      Mini-monovision versus multifocal intraocular lens implantation.
      • Leyland M.D.
      • Langan L.
      • Goolfee F.
      • et al.
      Prospective randomised double-masked trial of bilateral multifocal, bifocal or monofocal intraocular lenses.
      • Martinez P.A.
      • Gomez F.P.
      • Espana A.A.
      • et al.
      Visual function with bilateral implantation of monofocal and multifocal intraocular lenses: a prospective, randomized, controlled clinical trial.
      • Maxwell A.
      • Holland E.
      • Cibik L.
      • et al.
      Clinical and patient-reported outcomes of bilateral implantation of a +2.5 diopter multifocal intraocular lens.
      • Maxwell W.A.
      • Waycaster C.R.
      • D'Souza A.O.
      • et al.
      A United States cost-benefit comparison of an apodized, diffractive, presbyopia-correcting, multifocal intraocular lens and a conventional monofocal lens.
      • Nijkamp M.D.
      • Dolders M.G.T.
      • de Brabander J.
      • et al.
      Effectiveness of multifocal intraocular lenses to correct presbyopia after cataract surgery: A randomized controlled trial.
      • Peng C.
      • Zhao J.
      • Ma L.
      • et al.
      Optical performance after bilateral implantation of apodized aspheric diffractive multifocal intraocular lenses with +3.00-D addition power.
      • Puell M.C.
      • Pérez-Carrasco M.J.
      • Hurtado-Ce A.F.J.
      • et al.
      Disk halo size measured in individuals with monofocal versus diffractive multifocal intraocular lenses.
      • Rasp M.
      • Bachernegg A.
      • Seyeddain O.
      • et al.
      Bilateral reading performance of 4 multifocal intraocular lens models and a monofocal intraocular lens under bright lighting conditions.
      • Sen H.N.
      • Sarikkola A.
      • Uusitalo R.J.
      • et al.
      Quality of vision after AMO Array multifocal intraocular lens implantation.
      • Shah S.
      • Peris-Martinez C.
      • Reinhard T.
      • et al.
      Visual Outcomes After Cataract Surgery: Multifocal Versus Monofocal Intraocular Lenses.
      • Wilkins M.R.
      • Allan B.D.
      • Rubin G.S.
      • et al.
      Randomized Trial of Multifocal Intraocular Lenses versus Monovision after Bilateral Cataract Surgery.
      • Ye P.P.
      • Yao K.
      • Li X.
      • et al.
      Binocular clinical comparison study of Tecnis multifocal aspheric and monofocal spherical intraocular lenses.
      • Zeng M.
      • Liu Y.
      • Liu X.
      • et al.
      Aberration and contrast sensitivity comparison of aspherical and monofocal and multifocal intraocular lens eyes.
      • Zhao G.
      • Zhang J.
      • Zhou Y.
      • et al.
      Visual function after monocular implantation of apodized diffractive multifocal or single-piece monofocal intraocular lens: Randomized prospective comparison.
      The selection process is shown in Figure 1. Characteristics of the included studies were shown in Table 1. Subjects were aged 50 years or above. The median follow-up time was 6 months (range: 1–18).
      Table 1Characteristics of included randomized controlled trials studies
      AuthorYearSample size at baselineMean age (years)Follow-up time (months)Type of MFIOLs
      MonofocalMFIOL
      Javitt JC2000245Range (50–85)2–5.5Refractive
      Kamlesh20014053.555.73Unclear
      Leyland MD20025075.6 ± 8.374.8 ± 7.65Refractive
      Chen T200420868.6 ± 10.570.8 ± 11.712Refractive
      Sen HN20047572.4 ± 10.069.3 ± 9.91Refractive
      Nijkamp MD200415372.0 ± 8.572.0 ± 7.73Refractive
      Zeng M200712466.7 ± 7.565.3 ± 5.23Refractive
      Harman FE20089070.8 ± 11.873.5 ± 10.418Refractive
      Cillino S20086867.5 ± 9.660.6 ± 12.312Refractive
      Martines Palmer A200811474.5 ± 4.972.8 ± 5.123Diffractive
      Maxwell WA200849571.0 ± 7.869.0 ± 9.66Diffractive
      Zhao G201016167.364.76Diffractive
      Ye PP201010070.3 ± 7.768.2 ± 10.63Diffractive
      Peng C201210266.5 ± 9.065.5 ± 8.16Diffractive
      Rasp M201214375.8 ± 6.575.9 ± 7.312Refractive
      Ji J20135163.2 ± 8.963.0 ± 9.13Diffractive
      Wilkins MR201321268.7 ± 12.067.0 ± 11.24Diffractive
      Shah S201520870.8 ± 7.870.0 ± 8.36Diffractive
      Puell MC20153974.1 ± 2.173.8 ± 2.56Diffractive
      Labiris G20157559.5 ± 10.461.3 ± 9.36Refractive
      Maxwell A201732069.4 ± 8.368.7 ± 9.66Diffractive
      MFIOLs, multifocal intraocular lenses.
      Studies were ordered by publication year.
      Analysis on risk of bias (Fig. 2 and Fig. 3) showed that all studies generated the random sequence in an appropriate way. Only a few studies had a high-level risk of bias on blinding, incomplete data, or selective reporting.
      Figure thumbnail gr2
      Fig. 2‘Risk of bias’ graph about each risk of bias item.
      Figure thumbnail gr3
      Fig. 3‘Risk of bias’ summary about each risk of bias item.
      There was no statistical difference on uncorrected distance VA (UDVA) between MFIOLs and monofocal IOLs (Fig. 4); the MD was 0.02 (95% CI: 0.00, 0.03). The I2 was 21%, indicating that the heterogeneity across included studies was small. Two researchers measured uncorrected intermediate VA (UIVA) at the distance of 60 cm, and they both reported a better UIVA of patients undergoing MFIOLs implantation than those received monofocal IOLs implantation (Fig. 5); the MD was -0.06 (95% CI: -0.10, -0.03), and the I2 was 49%. There was no statistical difference on UIVA at the distance of 63 cm; the MD was 0.03 (95% CI: -0.02, 0.08). At a measured distance of 100 cm, 1 researcher reported a better UIVA of patients in the monofocal IOLs group than in the MFIOLs group; the MD was 0.07 (95% CI: 0.04, 0.10). Patients after MFIOLs implantation had a better uncorrected near VA (UNVA) than those accepting monofocal IOLs surgery (Fig. 6); the MD was -0.13 (95% CI: -0.20, -0.07). The I2 was 91%, indicating a large heterogeneity across included studies; thus, a subgroup analysis was done (Fig. 6). We split studies into 3 subgroups by the measurement distance of UNVA in each study; it turned out that no matter at the distance 30 cm, 33 cm, or 40 cm, patients undergoing MFIOLs implantation achieved a better UNVA than those accepting monofocal IOLs implantation; the MDs were -0.30 (95% CI: -0.36, -0.24), -0.08 (95% CI: -0.16, -0.01), and -0.12 (95% CI: -0.20, -0.04).
      Figure thumbnail gr4
      Fig. 4Forest plot of uncorrected distance visual acuity.
      Figure thumbnail gr5
      Fig. 5Forest plot of uncorrected intermediate visual acuity.
      Figure thumbnail gr6
      Fig. 6Forest plot of uncorrected near visual acuity.
      There was no statistical difference on corrected distance VA (CDVA) between MFIOLs and monofocal IOLs (Fig. 7). The I2 was 80%, indicating a large heterogeneity across included studies. We performed a subgroup analysis by the measurement distance of CDVA in each study (Fig. 7). We also performed a sensitivity analysis, and it turned out that no matter in which subgroup, no matter which study was omitted, there was no statistical difference on CDVA. Different studies measured distance-corrected intermediate VA at difference distances, including 60 cm, 63 cm, and 80 cm. Specifically, at the distance of 60 cm, patients' distance-corrected intermediate VA of the MFIOLs group was better than that of the monofocal IOLs group (Fig. 8); the MDs were -0.09 (95% CI: -0.12, -0.06). However, at the distances of 63 cm and 80 cm, there was no statistical difference; the MDs were 0.03 (95% CI: -0.02, 0.08) and 0.06 (95% CI: -0.05, 0.17). MFIOLs showed a better performance than monofocal IOLs on distance-corrected near VA (DCNVA) (Fig. 9); the MD was -0.31 (95% CI: -0.43, -0.19); however, the I2 was 96%, indicating a large heterogeneity across included studies. We also did a subgroup analysis (Fig. 9), splitting studies into 4 subgroups according to the measurement distance used in each study. It turned out that no matter at 30 cm, 33 cm, or 40 cm, MFIOLs showed a better performance than monofocal IOLs. The MDs were -0.38 (95% CI: -0.44, -0.32), -0.14 (95% CI: -0.18, -0.10), and -0.33 (95% CI: -0.56, -0.10). The I2 of the 40 cm subgroup was still above 50% because the CI of Peng and coworkers study did not overlap with the others. Actually, all 3 studies in the 40 cm subgroup reported a better DCNVA of MFIOLs.
      Figure thumbnail gr7
      Fig. 7Forest plot of corrected distance visual acuity.
      Figure thumbnail gr8
      Fig. 8Forest plot of distance-corrected intermediate visual acuity.
      Figure thumbnail gr9
      Fig. 9Forest plot of distance-corrected near visual acuity.
      The CS of the MFIOLs group was lower than that of the monofocal IOLs group (Fig. 10); the MD was -0.06 (95% CI: -0.11, -0.02). The heterogeneity was slightly large as the I2 was 59%, so a random-effects model was applied, and we also did a sensitivity analysis. It turned out that, after omitting study of Maxwell and coworkers, the I2 dropped to a mere 3.3%, and the CS of the MFIOLs group was still lower than monofocal IOLs group. The MD was -0.04 (-0.07, -0.01), and the conclusion remained unchanged.
      Figure thumbnail gr10
      Fig. 10Forest plot of contrast sensitivity.
      More patients in the MFIOLs group were spectacle free than those in the monofocal IOLs group (Fig. 11); the RR was 2.86 (95% CI: 1.73, 4.73). The I2 was 94%, however, indicative of a large heterogeneity. A subgroup analysis was done (Fig. 11), which showed that MFIOLs performed better than monofocal IOLs at 3, 6, or 12 months after implantation. The RR was 1.85 (95% CI: 1.20, 2.85), 4.03 (95% CI: 2.21, 7.36), and 4.03 (95% CI: 1.56, 10.41). We also did a sensitivity analysis, and it turned out that, after removing studies of Y and coworker, Maxwell and coworkers, and Maxwell and coworkers, the I2 dropped to 0% and the conclusion remained the same, with an RR of 2.83 (95% CI: 2.37, 3.39). In addition, for spectacle independence, a publication bias was found (t = 3.702, P = 0.004) by Egger's test (Table 2). We used a trim-and-fill method to adjust the effect for funnel plot asymmetry, after which the conclusion remained unchanged with an RR of 1.68 (95% CI: 1.14, 2.49). Clearly, MFIOLs performed better than monofocal IOLs on spectacle independence.
      Figure thumbnail gr11
      Fig. 11Forest plot of spectacle independence.
      Table 2Egger's test for each outcome
      Indicatorstdfp
      UDVA-0.12970.296
      UIVA-1.04220.407
      UNVA-0.77750.472
      CDVA0.98350.371
      DCIVA1.44820.284
      DCNVA-1.93140.128
      Contrast sensitivity-1.00450.409
      Spectacle independence3.702100.004
      Glare0.46930.670
      Halo0.65040.550
      UIVA, uncorrected intermediate visual acuity; UDVA, uncorrected distance visual acuity; UNVA, uncorrected near visual acuity; CDVA, corrected distance visual acuity; DCIVA, distance-corrected intermediate visual acuity; DCNVA, distance-corrected near visual acuity.
      More patients in the MFIOLs group suffered from glare than in the monofocal IOLs group (Fig. 12). The RR was 1.91 (95% CI: 1.24, 2.95), and there was no heterogeneity. Similarly, more patients were troubled with halos after MFIOLs implantation (Fig. 13). The RR was 3.08 (95% CI: 2.11, 4.49), and the I2 was 16%, indicative of a small heterogeneity.
      For all evaluated outcomes, no publication bias was found by Egger's test (Table 2) except for spectacle independence.
      For outcomes including UDVA, CDVA, UNVA, DCNVA, CS, and spectacle independence, we also did a subgroup analysis by MFIOLs types; MFIOLs were split into refractive and diffractive groups; the results were shown in the Appendix. It turned out that, for refractive MFIOLs or diffractive MFIOLs, there was no difference on UDVA and CDVA compared with monofocal IOLs. Both refractive MFIOLs and diffractive MFIOLs provided patients with a better UNVA, a better DCNVA, but a lower CS compared with monofocal IOLs.

      4. Discussion

      Cataract patients are eager for a high visual quality after IOL implantation. They want clear vision at different focal points; thus, MFIOLs were designed. There had been evidence showing that the major advantage of MFIOLs is the restoration of near vision function for cataract patients. Back in the 1990s, El-Maghraby and coworkers
      • El-Maghraby A.
      • Marzouky A.
      • Gazayerli E.
      • et al.
      Multifocal versus monofocal intraocular lenses. Visual and refractive comparisons.
      randomly allocated 77 cases to receive a 3M MFIOL or a conventional monofocal implantation. After a 4-month follow-up, 30% of the MFIOLs cases had near acuity J1, compared to only 4% of the monofocal IOLs cases. For the newly approved MFIOLs, like PanOptix from Alcon, an observational study
      • Monaco G.
      • Gari M.
      • Di Censo F.
      • et al.
      Visual performance after bilateral implantation of 2 new presbyopia-correcting intraocular lenses: Trifocal versus extended range of vision.
      also revealed the superiority of PanOptix's near vision.
      In this meta-analysis, we also found that MFIOLs provided better near vision than monofocal IOLs, especially at reading distance, which is usually 30 cm to 33 cm. Our meta-analysis showed the gap between monofocal IOLs and MFIOLs was up to 0.3 log units for UNVA and 0.38 log units for DCNVA. Given that loss of visual ability at the reading distance had a strong impact on patients' life quality, even on mobility orientation and the avoidance of falls,
      • Elliott D.B.
      • Patla A.E.
      • Furniss M.
      • et al.
      Improvements in clinical and functional vision and quality of life after second eye cataract surgery.
      MFIOLs are a better choice for cataract patients. Of course, MFIOL is not the only way to improve unaided reading ability and quality of life. Monovision by using monofocal lenses provides many advantages of the multifocal lenses without the photic adverse effects. Stock and coworkers
      • Stock R.A.
      • Thume T.
      • Paese L.G.
      • et al.
      Subjective evaluation of uncorrected vision in patients undergoing cataract surgery with (diffractive) multifocal lenses and monovision.
      reported that glare occurred less often in patients implanted with monofocal IOLs using monovision than in those implanted with bilateral MFIOLs. Mu and coworkers
      • Mu J.
      • Chen H.
      • Li Y.
      Comparison study of visual function and patient satisfaction in patients with monovision and patients with bilateral multifocal intraocular lenses.
      reported in a comparison study that patients receiving MFIOLs implantation complained of double vision, trouble in night vision, and halos more than those accepting monofocal IOL monovision.
      In this meta-analysis, we found no difference on UDVA and CDVA between MFIOLs and monofocal IOLs, no matter whether the measurement distance was 4 or 5 m. Tan and coworkers
      • Tan N.
      • Zheng D.
      • Ye J.
      Comparison of visual performance after implantation of 3 types of intraocular lenses: accommodative, multifocal, and monofocal.
      reported similar findings in their study. As to intermediate VA, retrospective studies
      • Baumuller S.
      • Anhalm H.
      • Muller M.F.
      • et al.
      Long-term visual outcome comparison of bilateral implantation of apodised diffractive versus progressive multizonal refractive multifocal intraocular lenses after cataract extraction.
      • Feng K.
      • Guo H.K.
      • Zhang Y.L.
      • et al.
      Visual quality comparison after multifocal toric intraocular lens or monofocal toric intraocular lens implantation.
      had already revealed MFIOLs' superiority over monofocal IOLs, and from this meta-analysis based on randomized controlled trials, we obtained a similar finding. Specifically, for UIVA, 4 studies were included, and only Wilkins and coworkers reported a worse UIVA of MFIOLs patients measured at 100 cm, which was reasonable because usually intermediate VA would be measured at a distance between 60 cm and 70 cm. Actually, some researchers tended to define VA measured at 100 cm as distance VA.
      • Chen W.R.
      • Meng Q.L.
      • Yang W.H.
      • et al.
      Comparative assessment of individualized multifocal intraocular lens implantation.
      Only 1 study reported the measurement of UIVA at the distance of 63 cm, and no statistical difference was found between MFIOLs and monofocal IOLs, while at the distance of 60 cm, both Peng and coworkers and Maxwell and coworkers reported a better UIVA of the MFIOLs group. The mean differences of UIVA between MFIOLs and monofocal IOLs at 100 cm, 63 cm, and 60 cm were 0.07, -0.03, and -0.07, respectively, indicating that there might be a tendency that the nearer the distance was, the better the UIVA would be; distance-corrected intermediate VA showed a similar distribution pattern as UIVA.
      Theoretically, multifocal lenses would split light among multiple focal points and lead to a reduced contrast on retinal image, which may arise functional loss of contrast sensitivity. In the 1990s, Lehmann and coworkers
      • Lehmann R.P.
      Paired comparison of contrast sensitivity in diffractive MFIOLs and conventional monofocal IOLs.
      compared contrast sensitivity in patients from the US Food and Drug Administration study of the 3M diffractive IOL and did find a decreased CS, but only in a few subjects. Olsen and coworkers
      • Olsen T.
      • Corydon L.
      Contrast sensitivity in patients with a new type of multifocal intraocular lens.
      did another comparison on CS between MFIOLs and monofocal IOLs, and it turned out that only near vision showed a 0.19 log units decrease, while for distance vision, there was no decrease. In this meta-analysis, we did observe a lower contrast sensitivity in MFIOLs patients; however, the gap between the MFIOLs group and monofocal IOLs group was only 0.06 unit; thus, the disadvantage of MFIOLs on CS was not large.
      In this meta-analysis, 12 researchers recorded the outcome of spectacle independence, and in all these studies, more MFIOL patients were free from glasses than those receiving monofocal IOLs. The pooled RR was up to 2.86, which was a large effect size. MFIOLs performed far better than monofocal IOLs on spectacle independence; however, by this meta-analysis, the disadvantage of MFIOLs on glare and halos was clear as, in every single study that recorded outcomes of glare or halos, there were more cases in the MFIOLs group. There was no heterogeneity across included studies for glare; the heterogeneity for halos was small (I2 = 16%). Unfortunately, glare, as well as halos, is a natural flaw of MFIOLs. Theoretically, multiple focal points will induce more light scatter than single focal point,
      • Holladay J.T.
      • Van Dijk H.
      • Lang A.
      • et al.
      Optical performance of multifocal intraocular lenses.
      and forward scattered light out of a glare source will generate a veil of luminance on the retina. In addition, the out-of-focus image tends to show a larger diameter than the sharp image, which forms halos.
      • Pieh S.
      • Lackner B.
      • Hanselmayer G.
      • et al.
      Halo size under distance and near conditions in refractive multifocal intraocular lenses.
      We need to acknowledge that there are many types of MFIOLs. The difference among refractive, diffractive, and segmental lenses and the difference among bifocal, trifocal, and extended depth of focus lenses are not negligible, but because of the limited number of published papers with extractable data, for some outcomes, we have to include all MFIOLs types. For outcomes such as UDVA, CDVA, UNVA, DCNVA, CS, and spectacle independence, there were enough studies, and we did a subgroup analysis by MFIOLs types; MFIOLs were split into refractive and diffractive groups; however, it seemed that, although refractive lenses were different from diffractive lenses in optical design, their performance was much alike. Both refractive MFIOLs and diffractive MFIOLs helped patients achieve a better UNVA and DCNVA compared with monofocal IOLs, while a lower CS was found in both subgroups. As a comparison between refractive MFIOLs and diffractive MFIOLs, Yildirim and coworkers
      • Yildirim K.R.
      • Gunenc U.
      • Aydin R.
      • et al.
      Visual Results Following Implantation of a Refractive Multifocal Intraocular Lens in One Eye and a Diffractive in the Contralateral Eye.
      conducted a prospective, nonrandomized study where 20 patients were implanted with refractive ReZoom NXG1 IOLs in their dominant eye, while diffractive Tecnis ZMA00 IOLs were implanted in the nondominant eye. After a 6-month follow-up, there was no statistical difference between near VA, CS, reading speed, halos, or glare.
      In conclusion, compared with monofocal IOLs aimed for emmetropia, MFIOLs have advantages in regards to near vision and intermediate vision at 60 cm, and patients having MFIOLs implanted are more likely to be spectacle free. There are drawbacks as patients undergoing MFIOLs implantation have an increased risk of glare and halos compared to those accepting monofocal IOLs implantation, as well as a slightly lower contrast sensitivity.

      5. Method of literature search

      The search strategy was (“Lenses, Intraocular”[Mesh] And comparison [ALL]); (“Multifocal Intraocular Lenses”[Mesh] AND “randomized” [ALL]); (“monofocal Intraocular lenses” and “randomized” [ALL]); (“Multifocal Intraocular Lenses”[Mesh] AND “randomly” [ALL]); (“monofocal Intraocular lenses” and “randomly” [ALL]) (“Multifocal Intraocular Lenses”[Mesh] AND “randomization” [ALL]); (“monofocal Intraocular lenses” and “randomization” [ALL]); (“Intraocular lenses” and “trial” [ALL]).

      6. Disclosures

      There is no conflict of interest.

      Acknowledgments

      Study design and concept of the article were carried out by Xiu Hua Wan, Jinda Wang, Jingshang Zhang, and Kai Cao; database search was carried out by Kai Cao, Shanshan Jin, Simeng Hou, and Guyu Zhu; data extraction was performed by Kai Cao and Shanshan Jin; data analysis was carried out by Kai Cao; manuscript writing was carried out by Kai Cao, David S. Friedman, Xiu Hua Wan, Ying Xiong, Xiaoxia Li, Jing Li, Hailong He, and Lijing Chai; English polishing was done by Mayinuer Yusufu; manuscript revision was done by David S. Friedman.
      This study was funded by Beijing New Star of Science and Technology ( H020821380190 and Z131102000413025 ), Fund of Work Committee for Women and Children of China State Department (2014108), National Natural Science Fund ( 30471861 ), Beijing Institute of Ophthalmology Leading Program (201515).

      Supplementary Data

      Figure thumbnail figs1
      Figure thumbnail figs2
      Figure thumbnail figs3
      Figure thumbnail figs4
      Figure thumbnail figs5
      Figure thumbnail figs6

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