Efficacy and safety of vitrectomy for congenital cataract surgery: a systematic review and meta-analysis based on randomized and controlled trials

Methodological quality of the review: Medium confidence

Author: Cao K, Wang J, Zhang J, Yusufu M, Jin S, Hou S, Zhu G, Wang B, Xiong Y, Li J, Li X, Chai L, He H, Wan XH.

Region: Not reported

Sector: Cataract surgery

Type of cataract: Paediatric cataract

Sub-sector: Risk

Equity focus: None specified

Quantitative synthesis method: Narrative synthesis and meta-analysis

Qualitative synthesis method: Not applicable

Background:

Research on administration of vitrectomy is mixed. Some researchers suggested anterior vitrectomy as a routine for primary capsulotomy and other researchers suggested that anterior vitrectomy should be done along with posterior continuous curvilinear capsulorrhexis (PCCC) for congenital cataract in children younger than five years, because age was a very important issue. Whether vitrectomy is necessary for congenital cataract surgery remains unclear.

Research objectives:

To explore the effectiveness and safety of vitrectomy for congenital cataract surgery.

Main findings:

In total, authors included 11 RCTs with 634 congenital cataract eyes in the analysis. Authors note that most studies were assessed as low risk on random sequence and selective reporting.

Based on the meta-analysis, authors state there were fewer visual axis opacification (VAO) cases in vitrectomy group compared to the control group with a relative risk (RR) of 0.15 (95% confidence interval (CI): 0.09, 0.26). Additionally, authors note that there was no heterogeneity among studies, with an I2 of 0% and a p value of 0.94. Egger’s test showed that there was no publication bias, p = 0.66.

Reviewers reported that reoperation rate in vitrectomy group was lower than that of control group either (RR = 0.40, 95% CI: 0.17, 0.94), and there was no heterogeneity (I2 = 0%, p = 0.85). Best-corrected visual acuity (BCVA) measured in LogMAR unit of vitrectomy group was smaller, with a mean difference (MD) of 0.17 (95%CI:  0.28, 0.05), and I2 was only 22%, indicating of a small heterogeneity. No statistical difference was found between two groups on intraocular lens (IOL) deposit (RR = 1.23, 95%CI: 0.70, 2.17), and the heterogeneity was small (I2 = 16%, p = 0.31). No statistical difference was found between two groups on synechiae (RR = 1.08, 95%CI: 0.60, 1.94), with a quite small heterogeneity (I2 = 3%, p = 0.38). No statistical difference was found between two groups on uveitis (RR = 0.55, 95%CI: 0.15, 2.01), and there was no heterogeneity (I2 = 0%, p = 0.94). Authors found no statistical difference on intraocular pressure (IOP) either, with a MD of 0.25 (95%CI:  1.56, 2.07), and there was no heterogeneity (I2 = 0%). Findings from the Egger’s test conducted by the authors, showed that there was no publication bias for all assessed outcomes. Low-contrast sensitivity was better in the vitrectomy group. And no evidence indicated vitrectomy could lead to a higher risk on secondary glaucoma or IOL decentration.

Based on the analysis of this review, authors concluded that vitrectomy helps lower the PCO risk and reoperation risk after congenital cataract surgery, and also, vitrectomy helps patients gain a better BCVA and achieve a better low-contrast sensitivity, with no trade-off on IOP control, IOL deposit, synechiae, uveitis and secondary glaucoma. The authors recommend performing vitrectomy during congenital cataract surgery.

Methodology:

Inclusion criteria consisted of RCTs, patients included congenital cataract children receiving IOL implantation, either with or without vitrectomy.

Authors conducted a search on PubMed, Science Direct, the Cochrane Library, the Chinese National Knowledge Infrastructure and the Wanfang Database, from inception to November 2017. Outcome measures included VAO or posterior capsule opacification (PCO); secondary surgery; best-corrected visual acuity; deposit, cells and pigments on the IOL optic; synechiae; uveitis; IOP; contrast sensitivity; secondary glaucoma; and IOL decentration.

Two reviewers extracted data and assessed paper quality independently. Risk of bias was assessed using the Cochrane Collaboration tool.

To synthesize the data, authors used MD and RR (MD = mean value of vitrectomy group minus mean value of control group) with their 95% CI to estimate continuous outcomes and categorical outcomes, respectively. Authors assessed heterogeneity across included studies using the Q test and I2 statistic. Authors applied a fixed-effects model to calculate pooled effect size of the RCTs. Additionally, authors used Egger’s test to test publication bias.

Applicability/external validity:

Authors note that for congenital cataract patients, vitrectomy helps decrease the risk of VAO and reoperation after surgery, and also helps gain better low contrast sensitivity, with no other obvious drawbacks.

Geographic focus:

Authors did not report geographical location of included studies.

Quality assessment:

Overall there is medium confidence in the conclusions about the effects of this review. Authors used appropriate methods to pool the data in the meta-analysis, extract data and assess risk of bias of included studies.

Authors excluded publication bias based on statistic test, however authors did conduct a thorough search of the literature to ensure they avoided publication bias. It’s not clear if selection bias was avoided as authors do not mention methods used to screen studies for inclusion. In addition, authors did not report limitations of the review.