Methodological quality of the review:  Medium confidence

Author: Zhou H, Zhu C, Xu W, Zhou F.

Region: Not specified

Sector: Cataract

Sub-sector: Surgery

Type of cataract: Age-related cataract

Equity focus: None specified

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Cataract surgery can effectively restore visual clarity and distance vision. The design of the traditional monofocal intraocular lenses (MF-IOLs) with a single fixed focal length can provide excellent distance vision, but the MF-IOL’s limited depth of focus means that they cannot provide clear vision at both distance and near. Accommodative IOLs (AC-IOLs) were designed to move along the visual axis to provide near, intermediate, and distance vision in pseudophakic patients. AC-IOLs were developed with the purpose of providing some adjusting capacity and some functional near-vision after cataract extraction. AC-IOLs provide useful near-vision without glasses while maintaining good distance vision.

Objectives:

Authors performed a systematic review and meta-analysis to evaluate whether accomodative intraocular lenses (AC-IOLs) are superior for cataract patients compared with monofocal IOLs (MF-IOLs).

Main findings:

Authors included a total of 12 randomized controlled trials (RCTs) and five cohort studies in the review. Authors attributed moderate and high quality to the included RCTs, and cohort studies were attributed high quality, where two studies were given 8 stars and two studies were given 7 stars on the Newcastle-Ottawa scale.

Authors results revealed that AC-IOLs improved distance-corrected near visual acuity (DCNVA) more than MF-IOLs (standard mean difference (SMD)= -1.84, 95% confidence interval (CI)=- 2.56 to -1.11, P (heterogeneity)<0.001, I²=94.2%). Authors reported no association between the two groups, indicating that the AC-IOLs and MF-IOLs were not significantly associated in terms of CDVA. Authors noted that AC-IOLs were associated with significantly greater anterior lens shift than MF-IOLs (weighted mean difference (WMD)=-0.30, 95% CI=-0.37 to -0.23, P (heterogeneity) =0.047, I²=55.5%). The pooled analysis conducted by the authors showed no significant difference between the two groups (SMD=-0.19,95%CI=-0.45 to 0.06,P heterogeneity=0.670, I²=0%) was observed, which indicates that the AC-IOLs and MF-IOLs were not significantly different in terms of contrast sensitivity. In addition, authors reported that spectacle independence was significantly better with AC-IOLs than with MF-IOLs (RR=3.07, 95% CI=1.06–8.89, P(heterogeneity)=0.007, I²=75.5%). The results from subgroup analyses were quite consistent with the overall results for distance-corrected near visual acuity, corrected distant visual acuity, pilocarpine induced IOL shift, and contrast sensitivity. However, in the subgroup analyses by the type of AC-IOLs, a significant different was observed in 1CU group for spectacle independence. Sensitivity analysis by omitting a single study in each turn revealed that the overall results were free from the influence of a single study, and the funnel plots showed no significant publication bias.

Methodology: 

The studies had to meet the following criteria to be eligible for inclusion in the meta-analysis: 1) enrolled cataract patients; 2) provide at least two comparison groups, one group received AC-IOLs, another group received MF-IOLs; 3) provide outcomes: distance corrected near visual acuity (DCNVA), corrected distant visual acuity (CDVA), pilocarpine-induced IOL shift, contrast sensitivity, and spectacle independence.

Authors searched for relevant studies up to August 2018 through the PubMed, Embase Cochrane Library, CNKI, and Wanfang databases with the following terms and their combinations: “cataract”, “intraocular lenses”, “lens implantation”, and “accommodative”. In addition, authors reviewed references of included studies as part of the search strategy. Authors did not restrict publication date and language.

Two reviewers independently screened studies for inclusion and extracted data of included studies. Authors conducted risk of bias assessment of the included RCTs using the Cochrane Collaboration’s tool, and used the Newcastle-Ottawa scale to assess the quality of cohort studies where authors could attribute a total of nine stars and the quality study was defined as a study with seven or more stars.

Authors conducted a meta-analysis by calculating the weighted mean difference/standard mean difference and 95% confidence intervals (CIs) for continuous data, and calculated the risk ratio and 95% CI for dichotomous data. Authors assessed heterogeneity using the Q-statistics and I² index. Authors used a random-effects model or fixed-effects model depending on the value of the I². Subgroup analyses were performed according to type of AC-IOL or study design and a sensitivity analysis was conducted by omitting a single study at a time.

In conclusion, authors note that despite the limitations of this meta-analysis, this study confirmed that AC-IOLs can provide cataract patients with excellent DCNVA and result in more high levels of spectacle independence than MF-IOLs. Authors note that further studies with larger data set and well-designed models are required to validate findings from tis review.

Applicability/external validity:

Authors did not discuss the generalizability of the results.

Geographic focus: Authors refer to another source where they included characteristics of included studies, including where the studies were conducted. However, this source was unreachable, therefore information on the geographical focus of included studies was not available.

Summary of quality assessment:

Medium confidence was attributed to this review as important limitations was identified within the review. Authors did not contact authors/experts as part of the search strategy to ensure that all relevant studies were included in the review. Authors used rigorous methods to screen for studies for inclusion and extract data of included studies. However, authors pooled data from cohort and RCTs into the analysis, which may not represent best practice as cohort studies differ in many aspects from RCTs and therefore impacting on the reliability of results.