Effectiveness of multifocal and monofocal intraocular lenses for cataract surgery and lens replacement: a systematic review and meta-analysis

Methodological quality of the review: Low confidence

Author: Khandelwal SS, Jun JJ, Mak S, Booth MS, Shekelle PG.

Region: United States of America (USA), Saudi Arabia, UK, Europe, India and China

Sector: Biomedical

Subsector: Treatment

Equity focus: Not stated

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:
Multifocal intraocular lenses (IOLs) offer the possibility of spectacle-free vision following cataract surgery, compared to standard IOLs. Existing systematic reviews have generally concluded that multifocal IOLs result in better uncorrected near vision and greater spectacle independence, but more unwanted visual phenomena, such as glare and halos, compared to monofocal IOLs. However, the certainty of evidence has been low for most outcomes, and pooled analyses have grouped together technologically obsolete lenses with newer lenses, potentially obscuring differences in performance across different lens types.

Objectives:
To assess visual outcomes in patients receiving MFIOLs compared to either monofocal IOLs or monovision, and to compare results between newer and older IOLs.

Main findings:
Authors included a total of 25 studies in the review. All of the studies were single-site, except for seven studies. Two studies were performed in the USA, four studies were performed in China, one in India and the rest in Europe. The quality of studies was graded as low.

Authors report that for both outcomes, corrected and uncorrected distance vision, comparing multifocal IOLs to monofocal IOLs, there were no statistically significant differences in vision between the multifocal and monofocal IOLs. Authors found no statistically significant differences between results for newer diffractive lenses as compared to refractive lenses.

The pooled analysis of 10 studies that reported uncorrected near vision comparing multifocal IOLs to monofocal IOLs, showed an estimate effect favouring multifocal IOLs with logMAR − 0.26 (95% CI − 0.37, − 0.15). Within these studies, authors found significant heterogeneity (I² = 94%) and no evidence of publication bias (Begg’s test P=0.86, Eggar’s test P=0.30).

Authors indicated statistically significant findings that newer diffractive lenses were better than refractive lenses (P=0.01).

Further study findings included from the random effects pooled estimate with a relative risk of 0.27 (95% CI 0.20, 0.38) favouring spectacle independence with multifocal IOLs. There was moderate heterogeneity (I²=40.2%). Begg’s and Eggar’s test for publication bias were P=.052 and .001, respectively. There was no evidence that newer diffractive lenses were better than refractive lenses or older diffractive lenses (P=0.40 and 0.16, respectively). The pooled random effects standardised mean difference was − 0.54 (95% CI − 1.12, 0.04) favouring multifocal IOLs. Authors found substantial heterogeneity (I²=87.9%), and no statistical evidence for publication bias (Begg’s test P=0.35, Eggar’stest P=0.58). There was no statistically significant difference in uncorrected distance vision.

Authors concluded that multifocal IOLs compared to standard IOLs or monovision result in better uncorrected near vision and a higher proportion of patients who achieve spectacle independence, but greater risk of unwanted visual phenomena. Newer diffractive lenses may be better than refractive lenses in near vision and quality of vision outcomes, with less risk of halos than older diffractive lenses and refractive lenses. Future research will be required to evaluate not only the potential benefits and risks but also the trade-offs of varying IOL technologies.

Methodology:
Authors conducted searches in PubMed from 1 January, 2006 to 30 April, 2017. Two team members independently screened the titles of retrieved citations. Inclusion criteria included RCTs of adults undergoing cataract extraction and comparing a multifocal lens with a standard monofocal lens or monovision and reporting spectacle independence. Additional outcomes were uncorrected and corrected distance vision, uncorrected near vision, validated measures of vision function (such as the VF-14) or quality of life. Data extraction was completed in duplicate. All discrepancies were resolved with full group discussion. RCTs were assessed for quality (risk of bias) with the Cochrane Risk of Bias tool.

The sample size, mean, and standard deviation for each treatment group were extracted from articles that reported visual acuity using Snellen or logMAR measurements. Data that reported visual acuity using Snellen charts were converted into logMAR values. A mean difference (MD) was calculated for each comparison of multifocal and monofocal lenses.

Meta-analyses were conducted for the visual acuity and quality of life outcomes using trials that reported a monofocal lens comparator. Because several trials reported comparisons of more than one intervention, two-level multilevel random effects models were estimated. For the two trials that reported a monovision comparator, a fixed-effects meta-analysis was performed. Test of heterogeneity was reported using the I² statistic.

Applicability/external validity:

Authors report that some studies did not systematically report operative events and the need for re-operation, or the need for any additional resources pre-operatively or post-operatively in patients receiving multifocal IOLs, as compared to monofocal IOLs. This review does not include newer IOLs and technologies that are currently in use or in late-phase clinical trials. However, the review has generated knowledge about the potential benefits and risks of multifocal IOLs, as compared to monofocal IOLs.

Geographic focus:
Authors indicate including studies from the USA, Saudi Arabia, UK, Europe, India and China, where findings can be applicable to those settings. However, they don’t discuss the applicability of findings to other settings.

Summary of quality assessment:
Low confidence was attributed to the overall conclusions about the effects of this review, as important limitations were identified. Authors did not conduct thorough searches of the literature to ensure that all relevant studies were identified. In addition, it is not clear from the review if authors covered a comprehensive search period to ensure that relevant literature was unlikely to be omitted.