Journal of Refractive Surgery

Review Supplemental Data

Refractive Versus Diffractive Multifocal Intraocular Lenses in Cataract Surgery: A Meta-analysis of Randomized Controlled Trials

Xian Xu, MM; Ming-Ming Zhu, MM; Hai-dong Zou, MD

Abstract

PURPOSE:

To compare the effectiveness of refractive multifocal intraocular lenses (MIOLs [refractive MIOL group]) versus diffractive MIOLs (diffractive MIOL group) in bilateral cataract surgery.

METHODS:

Data sources, including PubMed, Medline, Embase, and the Cochrane Controlled Trials Register, were used to identify potentially relevant randomized controlled trials. Eight qualified studies incorporating 1,242 eyes of 621 patients were analyzed using Rev-Manager version 5.2 software (The Cochrane Collaboration, Oxford, England). The primary measures included uncorrected distance, intermediate, and near visual acuity. Reading ability, spectacle independence, and occurrence of photic phenomena were also addressed.

RESULTS:

The refractive MIOL group exhibited better uncorrected distance visual acuity than the diffractive MIOL group (weighted mean difference [WMD] = −0.04, 95% confidence interval [CI]: −0.06 to −0.02, P < .01). However, the diffractive MIOL group performed better than the refractive MIOL group in uncorrected near visual acuity, reading acuity, reading speed, smallest print size, spectacle independence, halo, and glare rate (WMD = 0.13, 95% CI: 0.10 to 0.17, P < .01; WMD = 0.14, 95% CI: 0.08 to 0.19, P < .01; WMD = −24.14, 95% CI: −43.56 to −4.72, P = .01; WMD = 0.56, 95% CI: 0.43 to 0.69, P < .01; WMD = 0.56, 95% CI: 0.45 to 0.70, P < .01; WMD = 1.50, 95% CI: 1.16 to 1.93, P = .002; WMD = 1.39, 95% CI: 1.10 to 1.75, P = .006, respectively). There was no significant difference between the two groups in uncorrected intermediate visual acuity (WMD = −0.04, 95% CI: −0.09 to 0.00, P = .05).

CONCLUSIONS:

Refractive MIOLs can provide better distance vision, whereas diffractive MIOLs provide better near vision, reading ability, and equivalent intermediate vision, reduce unwanted photic phenomena, and allow greater spectacle independence.

[J Refract Surg. 2014;30(9):634–644.]

From the Department of Ophthalmology, Shanghai First People’s Hospital, Shanghai Jiao Tong University, Shanghai, China.

The authors have no financial or proprietary interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (XX, H-DZ); data collection (XX, M-MZ, H-DZ); analysis and interpretation of data (XX, M-MZ, H-DZ); drafting of the manuscript (XX, M-MZ, H-DZ); critical revision of the manuscript (XX, M-MZ, H-DZ); administrative, technical, or material support (H-DZ); supervision (H-DZ)

Correspondence: Hai-Dong Zou, MD, No. 100 Haining Road, Department of Ophthalmology, Shanghai First People’s Hospital, Shanghai Jiao Tong University, Shanghai 200080, China. E-mail: zouhaidong@hotmail.com

Received: March 17, 2014
Accepted: May 27, 2014
Posted Online: September 05, 2014

Abstract

PURPOSE:

To compare the effectiveness of refractive multifocal intraocular lenses (MIOLs [refractive MIOL group]) versus diffractive MIOLs (diffractive MIOL group) in bilateral cataract surgery.

METHODS:

Data sources, including PubMed, Medline, Embase, and the Cochrane Controlled Trials Register, were used to identify potentially relevant randomized controlled trials. Eight qualified studies incorporating 1,242 eyes of 621 patients were analyzed using Rev-Manager version 5.2 software (The Cochrane Collaboration, Oxford, England). The primary measures included uncorrected distance, intermediate, and near visual acuity. Reading ability, spectacle independence, and occurrence of photic phenomena were also addressed.

RESULTS:

The refractive MIOL group exhibited better uncorrected distance visual acuity than the diffractive MIOL group (weighted mean difference [WMD] = −0.04, 95% confidence interval [CI]: −0.06 to −0.02, P < .01). However, the diffractive MIOL group performed better than the refractive MIOL group in uncorrected near visual acuity, reading acuity, reading speed, smallest print size, spectacle independence, halo, and glare rate (WMD = 0.13, 95% CI: 0.10 to 0.17, P < .01; WMD = 0.14, 95% CI: 0.08 to 0.19, P < .01; WMD = −24.14, 95% CI: −43.56 to −4.72, P = .01; WMD = 0.56, 95% CI: 0.43 to 0.69, P < .01; WMD = 0.56, 95% CI: 0.45 to 0.70, P < .01; WMD = 1.50, 95% CI: 1.16 to 1.93, P = .002; WMD = 1.39, 95% CI: 1.10 to 1.75, P = .006, respectively). There was no significant difference between the two groups in uncorrected intermediate visual acuity (WMD = −0.04, 95% CI: −0.09 to 0.00, P = .05).

CONCLUSIONS:

Refractive MIOLs can provide better distance vision, whereas diffractive MIOLs provide better near vision, reading ability, and equivalent intermediate vision, reduce unwanted photic phenomena, and allow greater spectacle independence.

[J Refract Surg. 2014;30(9):634–644.]

From the Department of Ophthalmology, Shanghai First People’s Hospital, Shanghai Jiao Tong University, Shanghai, China.

The authors have no financial or proprietary interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (XX, H-DZ); data collection (XX, M-MZ, H-DZ); analysis and interpretation of data (XX, M-MZ, H-DZ); drafting of the manuscript (XX, M-MZ, H-DZ); critical revision of the manuscript (XX, M-MZ, H-DZ); administrative, technical, or material support (H-DZ); supervision (H-DZ)

Correspondence: Hai-Dong Zou, MD, No. 100 Haining Road, Department of Ophthalmology, Shanghai First People’s Hospital, Shanghai Jiao Tong University, Shanghai 200080, China. E-mail: zouhaidong@hotmail.com

Received: March 17, 2014
Accepted: May 27, 2014
Posted Online: September 05, 2014

MIOLs can be categorized as diffractive designed lenses, which are based on the Huygens–Fresnel principle, or as refractive lenses, which have additional annular aspheric structures on the anterior surface. MIOLs that use refraction, diffraction, and combinations of both have been developed in recent years. MIOLs provide better visual acuity at various distances and a degree of spectacle independence after cataract surgery.1–5 Some studies have described better intermediate vision with refractive IOLs,6 whereas others found no difference.7,8 We found that most of the relevant studies demonstrate that diffractive IOLs provide greater spectacle independence than refractive IOLs7,8; however, Chiam et al.6 did not find this difference to be statistically significant.

Despite the benefits of uncorrected visual acuity at multiple distances, MIOLs are associated with the following drawbacks: photic phenomena, such as halos and glare, and reduced contrast sensitivity.7 We found that most of the current literature demonstrates that refractive MIOLs are associated with an increase in photic phenomena compared to diffractive MIOLs.7–9 Pieh et al.10 and Percival and Setty11 stated that refractive MIOLs are associated with a lower incidence of optical symptoms compared to diffractive models,11 but Chiam et al. found that the occurrence of photic phenomena was comparable between the two groups.6

Because the results have not always been consistent, we conducted a systematic review and meta-analysis of the published randomized controlled trials to assess visual performances following the bilateral implantation of refractive IOLs and diffractive IOLs after cataract surgery.

Materials and Methods

The analysis methods and inclusion criteria were predefined and documented in a written protocol.

Search Strategy

Two independent investigators (XX, H-DZ) searched articles published from 2000 to April 4, 2014 that were limited to randomized controlled trials in PubMed, Medline, Embase, and the Cochrane Central Register of Controlled Trials using the following search terms: “cataract,” “multifocal,” “intraocular lenses,” and “phacoemulsification.” The reference lists from the primary articles and systematic reviews were scrutinized to identify additional trials. The searches were restricted to English.

Inclusion Criteria

For inclusion, the studies had to be randomized controlled trials (RCTs) that compared the postoperative visual performance of patients with refractive IOLs and diffractive IOLs. Simulation experiments with refractive and diffractive IOLs were excluded.

Patients with age-related cataracts who underwent phacoemulsification and bilateral implantation with a single type of MIOL were included. Patients with coexisting ocular pathologies, such as amblyopia, glaucoma, age-related macular degeneration, preexisting systemic disease such as diabetes, or a history of intraocular surgery that may have affected the postoperative visual outcome, were excluded.

Aside from the different types of IOLs (refractive or diffractive) that were implanted in the two groups, the patients received the same interventions.

The primary outcome measures that were collected included postoperative uncorrected distance, intermediate, and near visual acuity. Secondary outcome measures included postoperative reading ability, spectacle independence, and photic phenomena.

Data Extraction

Two independent investigators (XX, M-MZ) were involved in the data extraction using pre-defined data fields that included study quality indicators. A third investigator (H-DZ) reviewed the results and a consensus was reached. The patients’ outcomes following phacoemulsification and IOL implantation were reviewed. We extracted the following data from the eligible studies: (1) general characteristics (ie, title, first author, country of origin, journal, and year of publication); (2) methodology (ie, type of study, sequence generation, allocation concealment, masking or blinding, incomplete outcome data, and selective reporting and other sources of bias); (3) patients (ie, recruitment site, enrollment periods, inclusion criteria, exclusion criteria, and general patient characteristics); (4) interventions and control groups (ie, model of IOLs); (5) outcomes (ie, visual measurements, follow-up time, and loss of follow-up); (6) analysis (ie, statistical methods); and (7) results (ie, quantitative results, qualitative results, postoperative visual quality assessment, and adverse visual events). The corresponding authors of the individual trials were also contacted for unpublished information and unavailable data.

The mean visual acuities are reported as logMAR units and standard deviations if necessary after conversion of reported alternative visual acuity units.12,13

Assessment of Methodology Quality

Two independent investigators (XX, M-MZ) evaluated the quality of each study using the Jadad scale.14 The third investigator (H-DZ) examined the results and a consensus was reached. The Jadad score is based on a 5-point scale. High scores indicate high quality and are indicated by “yes” or “no” answers to 2 questions regarding randomization and masking and 1 question that evaluates the reporting of patient withdrawal. One point is given for each of the following: the study is described as randomized, the study is described as double-blind, and the study contains a description of withdrawals or dropouts. Two additional points are given if the method of randomization and the method of double blinding are appropriately described.

Statistical Analyses

All statistical analyses were performed with Review Manager version 5.2 (The Cochrane Collaboration, Oxford, England) using two-tailed P values and 95% confidence intervals (CIs). A P value less than .05 was considered statistically significant. Dichotomous outcomes were calculated as pooled odds ratios. For continuous outcomes, the analyses were performed using the mean differences. A fixed-effects model was used to pool the data. When substantial heterogeneity was present, a random-effect model was used.

Statistical heterogeneity was explored using the Q test with the calculated I2, which indicates the percentage of variability in the effect estimate that is attributable to heterogeneity rather than to chance.15 Insignificance indicates that the results of the different trials were similar (P ⩾ .1; I2 ⩽ 50%). We evaluated the pooled summary effects using a fixed-effect model to reduce the effects of heterogeneity between trials. Otherwise, the data were combined using the random-effect model (P < .1; I2 > 50%). When I2 was greater than 75%, subgroup analyses were used to analyze the sources of heterogeneity. Sensitivity analyses were calculated within subgroups of studies that were decided a priori and used to assess the robustness of the main conclusions and to explain the heterogeneity. To determine whether the results of the meta-analysis were unduly influenced by any outcome measures in any single study, we recomputed the meta-analysis statistic after sequentially deleting each outcome measure. Publication bias was explored by searching for asymmetry in funnel plots.16

Individual and pooled results are illustrated as point estimates and 95% CIs. Results for which the 95% CI did not include zero (for the mean differences) or 1 (for odds ratios) were considered statistically significant. Where data could not be combined, we conducted descriptive analyses.

Results

Literature Search

A total of 89 abstracts from the multiple databases were retrieved and 62 of these were retrieved based on their titles and abstracts. Only 8 RCTs,6–8,17–21 which recruited 1,242 eyes (621 patients), were included in our analysis. The trial selection process is shown in Figure 1.

Study selection process of randomized controlled trials (RCTs).

Figure 1.

Study selection process of randomized controlled trials (RCTs).

The characteristics of the RCTs included in the current meta-analysis are presented in Tables 12. All of the studies were performed in Europe. The mean age of the patients in most of the studies ranged from 45 to 85 years. The mean follow-up time period ranged from 6 weeks to 1 year (Table 1).

Characteristics of RCTs (n = 8) Included in the Meta-analysis

Table 1:

Characteristics of RCTs (n = 8) Included in the Meta-analysis

Characteristics of RCTs (n = 8) Included in the Meta-analysis

Table 2:

Characteristics of RCTs (n = 8) Included in the Meta-analysis

Quality Assessment

In five of the included RCTs, the investigators described a random component in the sequence generation process (eg, referring to a random number table17–19 or using a computerized random number generator7,20). The remainder of the studies did not describe the specific methods of the random sequence generation.

A total of four studies described their masking or blinding designs as double-blinded.7,18–20 All studies described their missing patients, but only one study had missing cases, and 3 (6%) of 50 cases were missing in that study.17

Only 4 studies used the following method or equivalent methods to achieve allocation concealment: sealed envelopes,18,19 sequential numbering,8 or maintaining the data at a central data facility.7 Therefore, we could not determine the existence of other potential factors. The quality assessments of the included studies are shown in Table A (available in the online version of this article).

Efficacy Analysis

Postoperative Uncorrected Visual Acuity

With the exception of Hutz et al.,19 the studies described postoperative binocular uncorrected distance visual acuity. The results of 7 studies16–19,21–23 (1,278 eyes of 639 patients) were logMAR transformed including the mean, standard deviation, and sample size (n). These studies had heterogeneity (P = .20; I2 = 25%). The random-effect model was used for meta-analysis. A significant difference between the two groups (weighted mean difference [WMD] = −0.04, 95% CI: −0.06 to −0.02, P < .00001) indicated that significantly better binocular uncorrected distance visual acuity was achieved with refractive IOLs than with diffractive IOLs. These results are shown in Figure 2. The funnel plot is shown in Figure A (available in the online version of this article).

Meta-analysis of postoperative binocular uncorrected distance visual acuity. MIOL = multifocal intraocular lens; SD = standard deviation; CI = confidence interval

Figure 2.

Meta-analysis of postoperative binocular uncorrected distance visual acuity. MIOL = multifocal intraocular lens; SD = standard deviation; CI = confidence interval

Three studies (352 eyes of 176 patients)6–8 compared postoperative binocular uncorrected intermediate visual acuities. The results were logMAR transformed including the mean, standard deviation, and sample size. These studies also exhibited a heterogeneity effect size of I2 = 67% (P = .03); thus, the random-effect model was used for meta-analysis. The results are shown in Figure 3. No significant difference between the two groups (WMD = −0.04, 95% CI: −0.09 to 0.00, P = .05) was observed, which indicates that the refractive IOLs and diffractive IOLs were not significantly different in terms of binocular uncorrected intermediate visual acuity.

Meta-analysis of postoperative binocular uncorrected intermediate visual acuity. MIOL = multifocal intraocular lens; SD = standard deviation; CI = confidence interval

Figure 3.

Meta-analysis of postoperative binocular uncorrected intermediate visual acuity. MIOL = multifocal intraocular lens; SD = standard deviation; CI = confidence interval

Subgroup analysis according to the different IOL types was also conducted. The studies were divided into three subgroups: refractive ReZoom versus diffractive ReSTOR (subgroup 1);6,8 refractive ReZoom versus diffractive Tecnis ZM900 (subgroup 2);7 and refractive ReZoom versus diffractive Tecnis ZMA00 (subgroup 3).8 All three subgroups were used to produce a random-effect model and the results from subgroup 1 showed that binocular uncorrected intermediate visual acuity was significantly better with the refractive IOLs than with the diffractive IOLs (WMD = −0.08, 95% CI: −0.12 to −0.04, P = .0002, n = 123); however, the results from subgroups 2 and 3 revealed no significant differences (WMD = −0.03, 95% CI: −0.07 to 0.01, P = .14, n = 31; WMD = 0.01, 95% CI: −0.06 to 0.08, P = .0002, n = 22, respectively). The results are shown in Figure 3.

Data regarding postoperative binocular uncorrected near visual acuity were collected from 6 trials (758 eyes of 379 patients).6–8,17,19,21 The results, including the mean, standard deviation, and sample size, were logMAR transformed. These studies were heterogeneous (P = .04; I2 = 53%); thus, the random-effect model was used for meta-analysis. A significant difference between the two groups (WMD = 0.13, 95% CI: 0.10 to 0.17, P < .00001) was found and indicated that the binocular uncorrected near visual acuity was significantly better with the diffractive IOLs than with the refractive IOLs.

Subgroup analysis according to the different IOL types was also conducted. The studies were divided into 4 subgroups: refractive ReZoom versus diffractive ReSTOR (subgroup 1);6,8,21 refractive ReZoom versus diffractive Tecnis ZMA00 (subgroup 2);8,21 refractive SA40 versus diffractive ReSTOR (subgroup 3);19 and refractive SA40 versus diffractive Tecnis ZM900 (subgroup 4).7,17 All 4 subgroups were included in a random-effect model and the results for subgroups 1, 2, and 3 revealed that the uncorrected near visual acuity was significantly better with the diffractive IOLs than with the refractive IOLs (WMD = 0.12, 95% CI: 0,09 to 0.14, P < .00001, n = 182; WMD = 0.15, 95% CI: 0.10 to 0.20, P < .00001, n = 78; WMD = 0.19, 95% CI: 0.10 to 0.28, P < .0001, n = 40; respectively). However, the result from subgroup 4 revealed no significant difference (WMD = 0.14, 95% CI: −0.04 to 0.32, P = .13, n = 79). These results are shown in Figure 4.

Meta-analysis of postoperative binocular uncorrected near visual acuity. MIOL = multifocal intraocular lens; SD = standard deviation; CI = confidence interval

Figure 4.

Meta-analysis of postoperative binocular uncorrected near visual acuity. MIOL = multifocal intraocular lens; SD = standard deviation; CI = confidence interval

Postoperative Reading Ability

Three studies19–21 compared the binocular reading acuities of refractive IOLs and diffractive IOLs after implantation. Reading acuities were tested with Radner Reading Charts19,22 or with the Salzburg Reading Desk.20,21,23 However, Alió et al.20 reported only the reading acuity graph or P values and did not provide detailed data. Thus, the mean and standard deviation of this study could not be calculated. We attempted to contact the author, but we were unable to obtain the corresponding data. Therefore, this study was not included in our pooled analysis. Because this exclusion could have caused measurement bias, we conducted a descriptive analysis with the result from Alió et al. and found that the diffractive multifocal groups had significantly better uncorrected reading acuity than the refractive multifocal groups at postoperative months 1 and 6 (P < .01).

Only two studies19,21 (334 total patients) used Radner Reading Charts and reported complete data. The results, including the mean, standard deviation, and sample size, were logRAD transformed. These studies had a heterogeneity effect size of I2 = 73% (P = .001); thus, the random-effect model was used for meta-analysis. We found a significant difference between the two groups (WMD = 0.14, 95% CI: 0.08 to 0.19, P < .00001) that indicated that binocular reading acuity was significantly better with the diffractive IOLs than with the refractive IOLs.

Subgroup analysis, according to illumination level, was also conducted. The studies were divided in two subgroups: a bright-light condition (subgroup 1)19,21 and a low-light condition (subgroup 2).19 Both subgroups were used to produce the random-effect model and the results from subgroup 1 revealed that binocular reading acuity was significantly better with the diffractive IOLs than with the refractive IOLs in the bright-light conditions (WMD = 0.17, 95% CI: 0.12 to 0.21, P < .00001, n = 254); however, the results from subgroup 2 revealed no significant difference (WMD = 0.06, 95% CI: −0.10 to 0.22, P = .47, n = 80). These results are shown in Figure 5.

Meta-analysis of postoperative binocular reading acuity. MIOL = multifocal intraocular lens; SD = standard deviation; CI = confidence interval

Figure 5.

Meta-analysis of postoperative binocular reading acuity. MIOL = multifocal intraocular lens; SD = standard deviation; CI = confidence interval

Reading speed was measured by recording the time required to read text with a print size of logRAD 0.4 (Snellen 20/50); this size is generally used for newspapers and books. Three studies (485 patients) compared the reading speeds of the patients with refractive IOLs and diffractive IOLs after implantation.19–21

These studies had a heterogeneity effect size of I2 = 88% (P < .00001); thus, the random-effect model was used for meta-analysis. We found a significant difference between the two groups (WMD = −24.14, 95% CI: −43.56 to −4.72, P = .01) that indicated that the reading speed of the patients with diffractive IOLs was significantly better than that of the patients with refractive IOLs.

Subgroup analysis according to the illumination level was also conducted. The studies were divided in two subgroups: a bright-light condition (subgroup 1)19–21 and a low-light condition (subgroup 2).19 Both subgroups were used in a random-effect model and the results from subgroup 1 revealed that the reading speed of the patients with the diffractive IOLs was significantly better than that of the patients with the refractive IOLs in the bright-light conditions (WMD = −18.94, 95% CI: −37.80 to −0.09, P = .05, n = 405). However, the result from subgroup 2 revealed no significant difference (WMD = −39.88, 95% CI: −108.47 to 28.71, P = .25, n = 80). The results are shown in Figure 6.

Meta-analysis of postoperative reading speed. MIOL = multifocal intraocular lens; SD = standard deviation; WPM = words per minute; CI = confidence interval

Figure 6.

Meta-analysis of postoperative reading speed. MIOL = multifocal intraocular lens; SD = standard deviation; WPM = words per minute; CI = confidence interval

The smallest print size that could be read with a minimum reading speed of 80 words per minute represents the lower limit for recreational sense-capturing reading.24,25 Two studies20,21 compared the smallest print size of the refractive IOLs and diffractive IOLs after implantation. However, the results from Alió et al.20 could not be used in the pooled analysis because only the smallest print size graph or P values were reported; no detailed data were reported, so the mean and standard deviations could not be calculated. Although we attempted to contact the author, we were unable to obtain the corresponding data. We were concerned that this would cause measurement bias, so we conducted a descriptive analysis of the study by Alió et al., which showed that the diffractive multifocal groups had uncorrected smallest print sizes that were significantly better than those of the refractive multifocal groups at postoperative months 1 and 6 (P < .01).

We analyzed one study21 that included 3 diffractive IOLs and 1 refractive IOL using the fixed-effect model for this meta-analysis (P = .62; I2 = 0%). The significant difference between the two groups (WMD = 0.56, 95% CI: 0.43 to 0.69, P < .00001, n = 174) indicated that uncorrected smallest print size was significantly better with the diffractive IOLs than with the refractive IOLs. The results are shown in Figure B (available in the online version of this article).

Postoperative Spectacle Independence and Photic Phenomenon

Data for postoperative spectacle independence were collected from 5 trials (401 patients).6–8,17,18 Additionally, these studies had a heterogeneity effect size of I2 = 41% (P = .09); thus, the random-effect model was used for meta-analysis. There was a significant difference between the two groups (WMD = 0.56, 95% CI: 0.45 to 0.70, P < .00001), which indicates that the spectacle independence was significantly better with the diffractive IOLs than with the refractive IOLs. The results are shown in Figure 7.

Meta-analysis of postoperative spectacle independence. MIOL = multifocal intraocular lens; M-H = Mantel-Haenszel random effect model IV; Random = inverse variance random effect model; CI = confidence interval

Figure 7.

Meta-analysis of postoperative spectacle independence. MIOL = multifocal intraocular lens; M-H = Mantel-Haenszel random effect model IV; Random = inverse variance random effect model; CI = confidence interval

A total of 4 studies (279 patients)6–8,17 compared postoperative halos. Additionally, these studies had a heterogeneity effect size of I2 = 32% (P = .19); thus, the random-effect model was used for meta-analysis. The significant difference between the two groups (WMD = 1.50, 95% CI: 1.16 to 1.93, P = .002) indicated that halo was significantly better with the diffractive IOLs than with the refractive IOLs. The results are shown in Figure 8.

Meta-analysis of postoperative halo. MIOL = multifocal intraocular lens; M-H = Mantel-Haenszel random effect model IV; Random = inverse variance random effect model; CI = confidence interval

Figure 8.

Meta-analysis of postoperative halo. MIOL = multifocal intraocular lens; M-H = Mantel-Haenszel random effect model IV; Random = inverse variance random effect model; CI = confidence interval

Four studies (279 patients)6–8,17 compared postoperative glares. No significant heterogeneity was observed (P = .63; I2 = 0%); thus, the fixed-effect model was used for meta-analysis. The significant difference between the two groups (WMD = 1.39, 95% CI: 1.10 to 1.75, P = .006) indicated that glare was significantly better with the diffractive IOLs than with the refractive IOLs. The results are shown in Figure 9.

Meta-analysis of postoperative glare. MIOL = multifocal intraocular lens; M-H = Mantel-Haenszel random effect model IV; Random = inverse variance random effect model; CI = confidence interval

Figure 9.

Meta-analysis of postoperative glare. MIOL = multifocal intraocular lens; M-H = Mantel-Haenszel random effect model IV; Random = inverse variance random effect model; CI = confidence interval

Discussion

This systematic review examined RCTs to compare the postoperative visual performances of refractive IOLs and diffractive IOLs. Our results revealed that the refractive MIOLs provided better distance vision acuity and that the diffractive MIOLs provided better near vision acuity, reading ability, equivalent intermediate vision, less unwanted photic phenomena, and greater spectacle independence.

MIOL implantation seeks to provide patients with good uncorrected visual acuity for both distant and close visual tasks. Refractive IOLs obtain multifocality via changes in the optical refractive power of different areas of the IOL optic. This type of MIOL is designed to direct light to a broad range of foci from near to far. Diffractive IOLs use a modified phase plate that creates a constructive interference of light rays to direct rays at either near or far foci. Thus, most diffractive IOLs are bifocal and direct approximately 41% of the light to the near image and 41% to the far image. Approximately 18% of light is lost to higher-order diffraction. In contrast, a refractive IOL focuses 100% of the available light. One of the design advantages of diffractive IOLs is that the entire lens surface contributes to both focal points, which makes IOLs relatively independent of lens decentration.26

Recent studies of the results of bilateral implantations of MIOLs in cataract surgeries demonstrate that the implantation of either refractive or diffractive6,17 MIOLs result in high levels of uncorrected distance and near visual acuity and therefore result in increased levels of spectacle independence compared to the implantation of monofocal IOLs. Binocular outcomes are generally better than uniocular outcomes, which may be the result of slight refractive differences between the eyes that result in an effect that is comparable to pseudophakic monovision or the result of more complex and less understood neurological processes. Traditionally, refractive MIOLs have performed better at intermediate distances than near distances.27,28 For this reason, refractive MIOLs have been implanted bilaterally in patients with strong intermediate vision demands (eg, computer work that mainly involves intermediate distances). The introduction of diffractive MIOLs with lower near additions has increased visual acuity at intermediate distances without decreasing near and distance visual acuities.29–31 A trend (P = .05) that suggested higher intermediate visual acuity with the refractive MIOLs was observed.

Reading is crucial in everyday life and losing this ability leads to a substantial reduction in the quality of life.32 Four parameters should be used for evaluating reading performance: reading acuity, reading distance, reading speed, and the smallest print size readable. MIOLs with a diffractive component provide comparable reading performances that are significantly better than those obtained with refractive multifocal or monofocal IOLs.20 One major factor underlying this difference could be the lower theoretic powers added. The other major factors responsible for the reduced near-visual acuities observed in the refractive groups could be that the designs of the refractive lens overemphasize distance vision and offer slight advantages in intermediate visual acuity that are accompanied by disadvantages in near-vision capabilities.

Photic phenomena are among the most frequent reasons for dissatisfaction with MIOL implantation.33,34 These effects seem to be inherent in MIOLs due to the presence of multiple images, of which only one is in focus. In general, halos are physical phenomena of light scattering that occur in patients with cataracts. This is not the case with multifocal lenses because there is an additional focus. The focused image on the retina is overlapped by a second out-of-focus image with a greater diameter that is produced by the distance or near focus. Indeed, patients are typically not disturbed by these optical effects35,36 and report that they become less noticeable over time. It has been demonstrated that halo and glare disabilities occur in eyes with monofocal and multifocal lenses and that patient age, corneal surface quality, anterior capsule margin, pupil diameter, and IOL design all affect photic phenomena.35

Our systematic review, along with other clinical studies, suggests that the diffractive IOLs result in better postoperative visual performances than refractive IOLs. However, these conclusions are inconsistent primarily due to the variety of diffractive MIOL designs that include full diffractive or hybrid apodized diffractive-refractive designs, spherical or aspheric designs, pupil-dependent or pupil-independent designs, non-tinted or yellow-tinted designs, and different near additions. We performed a search of articles from 2000 to April 4, 2014 that was limited to randomized controlled trials in PubMed, Medline, Embase, and the Cochrane Central Register of Controlled Trials using the following search terms: “cataract,” “diffractive,” “multifocal,” “intraocular lenses,” and “phacoemulsification.” Nine RCTs were included and the characteristics of these trials are presented in Tables BC (available in the online version of this article). Among these RCTs, four compared ReSTOR SN6AD3 and ReSTOR SN6AD1.37–40 The results were similar in that, compared to the eyes with the ReSTOR SN6AD3 (+4.00 diopters), the eyes that were implanted with the lower near addition ReSTOR SN6AD1 (+3.00 diopters) MIOLs exhibited better performance at intermediate distances,37,39 and similar performances in distance and near visual acuities,37–39 contrast sensitivity,37,39 quality of life,39,40 and optical quality.40 Both groups had high levels of satisfaction and spectacle independence, and the levels of visual disturbances were also similar between groups.39,40 Three other studies compared the performances of ReSTOR SN6AD3 and Acri.LISA366D (Carl Zeiss Meditec, Jena, Germany).20,21,41 Compared to the ReSTOR SN6AD3 group, the Acri.Lisa group exhibited better reading speed values (means and maximums, corrected and uncorrected), similar uncorrected distance visual acuities, and similar or better uncorrected near visual acuities.20,21,41 However, because the number of recently published RCT studies comparing different diffractive IOLs remains low, further evidence is required to draw more reliable conclusions.

Meta-analysis is a method of pooling the data from different studies and objectively re-analyzing the resulting dataset to provide a more precise interpretation to assist in clinical decision making. Possible limitations include the inappropriate pooling of data and publication biases. In our analysis, we included only the most recent series of patient data and RCTs to avoid acknowledged and unintended duplication of data, which is the optimal strategy for meta-analysis. To minimize publication bias, we conducted an electronic search and a manual search of the references of the relevant studies to identify all of the potential relevant articles. This systematic review identified 8 studies that met all of the strict inclusion criteria; therefore, the intervention groups and control groups were comparable. However, the overall qualities of the studies were not high. Only 5 studies had adequate sequence generation, 4 studies used adequate methods to achieve allocation concealment, and 4 studies made no mention of masking. Additionally, the different follow-up time periods and the insufficient reporting of postoperative adverse visual events may have caused selection bias. Several studies lacked sufficient data for analysis, involved different measurement methods, used different units of measurement, or did not use a standard questionnaire to assess the patients. All factors may have resulted in measurement bias. All of the information in this systematic review came from the published literature. Special reports and unpublished data were not included because such information could cause publication bias. Therefore, to improve the quality of RCTs in the future, further verifications of the postoperative visual performance and safety of refractive and diffractive IOLs are needed.

MIOLs can provide patients with excellent uncorrected distance and near visual acuities that result in high levels of spectacle independence. Dissatisfaction following the implantation of MIOLs is rare and is often amenable to treatment. Some cases of dissatisfaction are due to the occurrence of photic phenomena that are inherent to the design of MIOLs and are therefore more difficult to treat. Thus, preoperative patient education and the careful selection of cases, including evaluations of the corneal surfaces and individualized weighing of the benefits and side effects of MIOLs, seem to be important for achieving excellent results and complete patient satisfaction.

References

  1. Javitt JC, Wang F, Trentacost DJ, Rowe M, Tarantino N. Outcomes of cataract extraction with multifocal intraocular lens implantation: functional status and quality of life. Ophthalmology. 1997;104:589–599. doi:10.1016/S0161-6420(97)30265-6 [CrossRef]
  2. Rossetti L, Carraro F, Rovati M, Orzalesi N. Performance of diffractive multifocal intraocular lenses in extracapsular cataract surgery. J Cataract Refract Surg. 1994;20:124–128. doi:10.1016/S0886-3350(13)80150-2 [CrossRef]
  3. Vaquero M, Encinas JL, Jimenez F. Visual function with monofocal versus multifocal IOLs. J Cataract Refract Surg. 1996;22:1222–1225. doi:10.1016/S0886-3350(96)80071-X [CrossRef]
  4. Gimbel HV, Sanders DR, Raanan MG. Visual and refractive results of multifocal intraocular lenses. Ophthalmology. 1991;98:881–887; discussion 888. doi:10.1016/S0161-6420(91)32205-X [CrossRef]
  5. Javitt JC, Steinert RF. Cataract extraction with multifocal intraocular lens implantation: a multinational clinical trial evaluating clinical, functional, and quality-of-life outcomes. Ophthalmology. 2000;107:2040–2048. doi:10.1016/S0161-6420(00)00368-7 [CrossRef]
  6. Chiam PJ, Chan JH, Haider SI, Karia N, Kasaby H, Aggarwal RK. Functional vision with bilateral ReZoom and ReSTOR intraocular lenses 6 months after cataract surgery. J Cataract Refract Surg. 2007;33:2057–2061. doi:10.1016/j.jcrs.2007.07.029 [CrossRef]
  7. Cillino S, Casuccio A, Di Pace F, et al. One-year outcomes with new-generation multifocal intraocular lenses. Ophthalmology. 2008;115:1508–1516. doi:10.1016/j.ophtha.2008.04.017 [CrossRef]
  8. Gil MA, Varon C, Rosello N, Cardona G, Buil JA. Visual acuity, contrast sensitivity, subjective quality of vision, and quality of life with 4 different multifocal IOLs. Eur J Ophthalmol. 2012;22:175–187. doi:10.5301/EJO.2011.8371 [CrossRef]
  9. Alió JL, Tavolato M, De la Hoz F, Claramonte P, Rodríguez-Prats JL, Galal A. Near vision restoration with refractive lens exchange and pseudoaccommodating and multifocal refractive and diffractive intraocular lenses: comparative clinical study. J Cataract Refract Surg. 2004;30:2494–2503. doi:10.1016/j.jcrs.2004.04.052 [CrossRef]
  10. Pieh S, Weghaupt H, Skorpik C. Contrast sensitivity and glare disability with diffractive and refractive multifocal intraocular lenses. J Cataract Refract Surg. 1998;24:659–662. doi:10.1016/S0886-3350(98)80261-7 [CrossRef]
  11. Percival SP, Setty SS. Comparative analysis of three prospective trials of multifocal implants. Eye (Lond). 1991;5:712–716. doi:10.1038/eye.1991.131 [CrossRef]
  12. Khoshnood B, Mesbah M, Jeanbat V, Lafuma A, Berdeaux G. Transforming scales of measurement of visual acuity at the group level. Ophthalmic Physiol Opt. 2010;30:816–823. doi:10.1111/j.1475-1313.2010.00766.x [CrossRef]
  13. Hozo SP, Djulbegovic B, Hozo I. Estimating the mean and variance from the median, range, and the size of a sample. BMC Med Res Methodol. 2005;5:13. doi:10.1186/1471-2288-5-13 [CrossRef]
  14. Jadad AR, Moore RA, Carroll D, et al. Assessing the quality of reports of randomized clinical trials: is blinding necessary?Control Clin Trials. 1996;17:1–12. doi:10.1016/0197-2456(95)00134-4 [CrossRef]
  15. Higgins JP, Thompson SG. Quantifying heterogeneity in a meta-analysis. Stat Med. 2002;21:1539–1558. doi:10.1002/sim.1186 [CrossRef]
  16. Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ. 1997;315:629–634. doi:10.1136/bmj.315.7109.629 [CrossRef]
  17. Mester U, Hunold W, Wesendahl T, Kaymak H. Functional outcomes after implantation of Tecnis ZM900 and Array SA40 multifocal intraocular lenses. J Cataract Refract Surg. 2007;33:1033–1040. doi:10.1016/j.jcrs.2007.02.037 [CrossRef]
  18. Martínez Palmer A, Gomez Faina P, Espana Albelda A, Comas Serrano M, Nahra Saad D, Castilla Céspedes M. Visual function with bilateral implantation of monofocal and multifocal intraocular lenses: a prospective, randomized, controlled clinical trial. J Refract Surg. 2008;24:257–264.
  19. Hutz WW, Eckhardt HB, Rohrig B, Grolmus R. Reading ability with 3 multifocal intraocular lens models. J Cataract Refract Surg. 2006;32:2015–2021. doi:10.1016/j.jcrs.2006.08.029 [CrossRef]
  20. Alió JL, Grabner G, Plaza-Puche AB, et al. Postoperative bilateral reading performance with 4 intraocular lens models: six-month results. J Cataract Refract Surg. 2011;37:842–852. doi:10.1016/j.jcrs.2010.11.039 [CrossRef]
  21. 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. J Cataract Refract Surg. 2012;38:1950–1961. doi:10.1016/j.jcrs.2012.07.027 [CrossRef]
  22. Radner W, Willinger U, Obermayer W, Mudrich C, Velikay-Parel M, Eisenwort B. A new reading chart for simultaneous determination of reading vision and reading speed [article in German]. Klin Monbl Augenheilkd. 1998;213:174–181. doi:10.1055/s-2008-1034969 [CrossRef]
  23. Dexl AK, Schlogel H, Wolfbauer M, Grabner G. Device for improving quantification of reading acuity and reading speed. J Refract Surg. 2010;26:682–688. doi:10.3928/1081597X-20091119-01 [CrossRef]
  24. Rubin GS, West SK, Munoz B, et al. A comprehensive assessment of visual impairment in a population of older Americans. The SEE Study. Salisbury Eye Evaluation Project. Invest Ophthalmol Vis Sci. 1997;38:557–568.
  25. Whittaker SG, Lovie-Kitchin J. Visual requirements for reading. Optom Vis Sci. 1993;70:54–65. doi:10.1097/00006324-199301000-00010 [CrossRef]
  26. Walkow T, Liekfeld A, Anders N, Pham DT, Hartmann C, Wollensak J. A prospective evaluation of a diffractive versus a refractive designed multifocal intraocular lens. Ophthalmology. 1997;104:1380–1386. doi:10.1016/S0161-6420(97)30127-4 [CrossRef]
  27. de Vries NE, Webers CA, Verbakel F, et al. Visual outcome and patient satisfaction after multifocal intraocular lens implantation: aspheric versus spherical design. J Cataract Refract Surg. 2010;36:1897–1904. doi:10.1016/j.jcrs.2010.05.030 [CrossRef]
  28. Pepose JS, Qazi MA, Davies J, et al. Visual performance of patients with bilateral vs combination Crystalens, ReZoom, and ReSTOR intraocular lens implants. Am J Ophthalmol. 2007;144:347–357. doi:10.1016/j.ajo.2007.05.036 [CrossRef]
  29. Alfonso JF, Fernandez-Vega L, Puchades C, Montes-Mico R. Intermediate visual function with different multifocal intraocular lens models. J Cataract Refract Surg. 2010;36:733–739. doi:10.1016/j.jcrs.2009.11.018 [CrossRef]
  30. Mester U, Junker B, Kaymak H. Functional results with two multifocal intraocular lenses with different near addition [article in German]. Ophthalmologe. 2011;108:137–142. doi:10.1007/s00347-010-2220-x [CrossRef]
  31. Kohnen T, Nuijts R, Levy P, Haefliger E, Alfonso JF. Visual function after bilateral implantation of apodized diffractive aspheric multifocal intraocular lenses with a +3.0 D addition. J Cataract Refract Surg. 2009;35:2062–2069. doi:10.1016/j.jcrs.2009.08.013 [CrossRef]
  32. Stifter E, Sacu S, Weghaupt H, et al. Reading performance depending on the type of cataract and its predictability on the visual outcome. J Cataract Refract Surg. 2004;30:1259–1267. doi:10.1016/j.jcrs.2003.11.051 [CrossRef]
  33. Woodward MA, Randleman JB, Stulting RD. Dissatisfaction after multifocal intraocular lens implantation. J Cataract Refract Surg. 2009;35:992–997. doi:10.1016/j.jcrs.2009.01.031 [CrossRef]
  34. de Vries NE, Webers CA, Touwslager WR, et al. Dissatisfaction after implantation of multifocal intraocular lenses. J Cataract Refract Surg. 2011;37:859–865. doi:10.1016/j.jcrs.2010.11.032 [CrossRef]
  35. Dick HB, Krummenauer F, Schwenn O, Krist R, Pfeiffer N. Objective and subjective evaluation of photic phenomena after monofocal and multifocal intraocular lens implantation. Ophthalmology. 1999;106:1878–1886. doi:10.1016/S0161-6420(99)90396-2 [CrossRef]
  36. Pieh S, Lackner B, Hanselmayer G, et al. Halo size under distance and near conditions in refractive multifocal intraocular lenses. Br J Ophthalmol. 2001;85:816–821. doi:10.1136/bjo.85.7.816 [CrossRef]
  37. Cillino G, Casuccio A, Pasti M, Bono V, Mencucci R, Cillino S. Working-age cataract patients: visual results, reading performance, and quality of life with three diffractive multifocal intraocular lenses. Ophthalmology. 2014;121:34–44. doi:10.1016/j.ophtha.2013.06.034 [CrossRef]
  38. Santhiago MR, Netto MV, Espindola RF, et al. Comparison of reading performance after bilateral implantation of multifocal intraocular lenses with +3.00 or +4.00 diopter addition. J Cataract Refract Surg. 2010;36:1874–1879. doi:10.1016/j.jcrs.2010.05.022 [CrossRef]
  39. Santhiago MR, Wilson SE, Netto MV, et al. Visual performance of an apodized diffractive multifocal intraocular lens with +3.00-d addition: 1-year follow-up. J Refract Surg. 2011;27:899–906. doi:10.3928/1081597X-20110816-01 [CrossRef]
  40. Santhiago MR, Wilson SE, Netto MV, et al. Modulation transfer function and optical quality after bilateral implantation of a +3.00 D versus a +4.00 D multifocal intraocular lens. J Cataract Refract Surg. 2012;38:215–220. doi:10.1016/j.jcrs.2011.08.029 [CrossRef]
  41. Alió JL, Plaza-Puche AB, Piñero DP, Amparo F, Rodríguez-Prats JL, Ayala MJ. Quality of life evaluation after implantation of 2 multifocal intraocular lens models and a monofocal model. J Cataract Refract Surg. 2011;37:638–648. doi:10.1016/j.jcrs.2010.10.056 [CrossRef]
Funnel plot showing meta-analysis of postoperative binocular uncorrected distance visual acuity. SE = standard error; MD = mean difference

Figure A. Funnel plot showing meta-analysis of postoperative binocular uncorrected distance visual acuity. SE = standard error; MD = mean difference

Meta-analysis of postoperative smallest print size. MIOL = multifocal intraocular lens; SD = standard deviation; CI = confidence interval

Characteristics of RCTs (n = 8) Included in the Meta-analysis

Study Site Age (y) Eyes Patients IOL Type NA (D) Follow-up
Chiam et al.6 (2007) United Kingdom 69.0 ± 7.0 100 50 ReSTOR SA60D3 Diff+Ref +4.00 6 months
67.8 ± 8.1 100 50 Rezoom NXG1 Ref +3.50
Mester et al.17 (2007) Germany 68.3 ± 7.0 46 23 Tecnis ZM900 Diff +4.00 6 months
71.2 ± 6.7 48 24 Array SA40 Ref +3.50
Martínez Palmer et al.18 (2008) Spain 72.8 ± 4.4 52 26 Tecnis ZM900 Diff +4.00 3 months
74.4 ± 5.2 64 32 Acri.Twin Diff +4.00
71.6 ± 5.6 64 32 Rezoom NXG1 Ref +3.50
Cillino et al.7 (2008) Italy 59.7 ± 15.3 32 16 Tecnis ZM900 Diff +4.00 12 months
57.4 ± 9.0 32 16 Array SA40N Ref +3.50
64.9 ± 11.3 30 15 Rezoom NXG1 Ref +3.50
Hutz et al.19 (2006) Germany 67.0 ± 11.0 40 20 ReSTOR SA60D3 Diff+Ref +4.00 6 weeks
67.0 ± 8.0 40 20 Tecnis ZM001 Diff +4.00
74.0 ± 8.0 40 20 Array SA40N Ref +3.50
Gil et al.8 (2012) Spain 63.3 ± 9.4 24 12 ReSTOR SN6AD1 Diff+Ref +3.00 3 months
68.3 ± 8.9 26 13 ReSTOR SN60D3 Diff+Ref +4.00
68.9 ± 7.4 22 11 Tecnis ZMA00 Diff +4.00
70.1 ± 7.9 22 11 Rezoom NXG1 Ref +3.50
Alió et al.20 (2011) Spain, Austria 70.1 ± 9.1 78 39 ReSTOR SN6AD3 Diff+Ref +4.00 6 months
70.8 ± 10.3 84 42 Acri.LISA366D Diff+Ref +4.00
74.2 ±7.1 70 35 Rezoom NXG1 Ref +3.50
Rasp et al.21 (2012) Austria 74. 0 ± 7.2 60 30 Acri.LISA366D Diff+Ref +3.75 12 months
76.4 ± 8.6 56 28 ReSTOR SN6AD3 Diff+Ref +4.00
74.5 ± 7.1 52 26 Tecnis ZMA00 Diff +4.00
78.7 ± 6.2 60 30 Rezoom NXG1 Ref +3.50

Characteristics of RCTs (n = 8) Included in the Meta-analysis

Study UDVA UIVA UNVA CS SI RA RS SPS Glare Halo S PS
Chiam et al.6 (2007) NA NA NA NA NA
Mester et al.17 (2007) NA NA NA NA
Martínez Palmer et al.18 (2008) NA NA NA NA NA NA NA NA NA
Cillino et al.7 (2008) NA NA NA NA
Hutz et al.19 (2006) NA NA NA NA NA NA NA NA
Gil et al.8 (2012) NA NA NA
Alió et al.20 (2011) NA NA NA NA NA NA NA NA
Rasp et al.21 (2012) NA NA NA NA NA NA NA

10.3928/1081597X-20140814-04

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