Methodological quality of the review: High confidence

Author: Shentu X, Zhang X, Tang X, Yu X

Region: Not reported

Sector: Cataract surgery

Sub-sector: Quality of clinical care

Type of cataract: Age-related cataract

Equity focus: None reported

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Due to recent improvements in phacoemulsification techniques, advances in surgical instruments, and the advent of the foldable intraocular lens (IOL), the C-MICS technique has gained global popularity among ophthalmologists. Prior to these advances, the C-SICS approach, which required a 2.8 to 3.2mm incision, was the most widely used surgical approach. Using the C-MICS technique can reduce the incision to less than 2.2mm.

Research objectives:

To quantitatively ascertain if a switch from C-SICS to C-MICS is necessary.

Main findings:

A total of 15 randomized controlled trials (RCTs) were included in the review, involving 1,136 eyes. Authors found no significant between-group differences detected in elapsed phaco time (EPT), balanced salt solution (BSS) use, cumulative dissipated energy (CDE), best corrected visual acuity (BCVA), laser flare photometry values or increased central corneal thickness (CCT). However, the C-MICS group showed less surgically induced astigmatism (SIA) (at postoperative day 7: p<0.01; at postoperative day 30 or more: p<0.01) and greater corneal endothelial cell loss (ECL)% (at postoperative day 60 or more: p<0.01), whereas the C-SICS group required a shorter ultrasound time (p<0.01).

Authors note that the pooled results, following the sequential omission of individual studies, all fell in the range of the confidence interval with all RCTs included, indicating robust main meta-analysis results. No publication biases were detected by the authors, except an increase in CCT at postoperative day 7 (Begg test: Z = 1.02, p = 0.308; Egger test: p = 0.048). The results of the meta-analysis showed that sample size was the main heterogeneity source of CDE and BCVA at postoperative day 30 (P<0.05).

Methodology:

Only articles that fulfilled all of the following criteria were considered for inclusion in the meta-analysis: (1) original RCTs comparing the outcomes of C-MICS with the outcomes of C-SICS; (2) subjects with no ocular diseases other than cataracts; and (3) C-MICS incision sizes of less than 2.2mm.

Systemic literature searches were performed in three databases: PubMed, Web of Science and The Cochrane Library. The search covered studies published until May 2015. The reference lists of relevant papers were then manually screened by the investigators for pertinent articles missed in the primary searches. No restrictions were applied in the search.

Two reviewers independently screened studies for inclusion, extracted data and assessed the methodological quality of included studies. All RCTs were assessed according to the Jadad scoring systems, and studies scoring or more points were considered to be of high quality.

Authors conducted a meta-analysis using Stata. The significance level of the statistics was set to P<0.01, except in the case of heterogeneity and meta-regression analyses. The means and standard deviations of continuous outcomes were used to calculate the weighted mean difference (WMD) with a 95% confidence interval (CI). Potential heterogeneities among the included studies were assessed using Cochran’s Q statistic and an I2 index score, with the significance level set at a P-value less than 0.10 or an I2 score greater than 50%. When high heterogeneity was detected among the included studies, authors used random effects model based on the DerSimonian and Laird method; otherwise, the fixed-effects model based on the inverse variance method was performed. A sensitivity analysis was used to assess the robustness of the meta-analysis results by sequentially omitting individual studies. Egger’s linear regression and Begg’s rank correlation tests were used to evaluate the potential publication bias.

Applicability/external validity:

Authors do not discuss the applicability of findings.

Geographic focus:

Authors do not report the geographical location of included studies.

Quality assessment:

Overall, there is high confidence in the conclusions about the effects of the study. Authors used appropriate methods to search, screen, extract data and assess the methodological quality of included studies.  Authors included studies which were similar enough to conduct a meta-analysis, and used appropriate methods to analyse the robustness of the results.