Effect of Pars Plana Vitrectomy With or Without Cataract Surgery in Patients with Diabetes: A Systematic Review and Meta-Analysis

Authors: Xiao K, Dong YC, Xiao XG, Liang SZ, Wang J, Qian C, Wan GM.

Geographical coverage: Korea, the USA and Taiwan

Sector: Cataract surgery

Sub-sector: Treatment outcomes

Equity focus: Not reported

Study population: Patients with diabetes

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Diabetic retinopathy is a major microvascular complication and a leading cause of blindness in diabetic patients. Pars plana vitrectomy (PPV) has long been a standard and effective treatment for its complications. However, cataract formation, especially in phakic eyes, is a common consequence after PPV. Managing the lens during PPV has become a subject of debate, particularly given the increased risk of cataract formation and the surgical challenges associated with delaying cataract removal. Early concerns about worsening retinopathy after lens extraction have led to lens-sparing strategies. Yet, advances in surgical methods have improved outcomes with combined PPV and cataract surgery. Therefore, the combined approach is increasingly considered a viable option for diabetic patients with significant cataracts.

Objective: To evaluate the treatment outcome of PPV with or without cataract surgery.

Main findings: The review included five studies (747 eyes). Of these, one was a randomised controlled trial (RCT), one was a prospective study, and three were retrospective studies. Two of the five studies were conducted in the USA, two in Korea and one in Taiwan. A total of 325 eyes underwent PPV alone, and 422 eyes underwent PPV combined with cataract surgery.

The findings showed that postoperative visual acuity improved in both groups. In four of the five studies, no statistically significant difference in final visual outcomes was found between the two groups. Only one study found greater visual improvement in the combined surgery group, likely because those patients had more advanced cataracts at baseline. In one study, 64% of phakic eyes developed cataract after PPV, and 39% of those required cataract surgery within four years. Another study reported that 20 out of 26 eyes that were clear at baseline subsequently developed cataracts.

Certain complications were more common in the combined surgery group. A pooled analysis of three studies indicated that the PPV-alone group had a significantly lower risk of neovascular glaucoma (odds ratio [OR] = 0.36, 95% CI: 0.13–0.97, P < 0.05), iris rubeosis (OR = 0.26, 95% CI: 0.08–0.88, P < 0.05), and iris synechiae to the anterior capsule (OR = 0.17, 95% CI: 0.03–0.85, P < 0.05) compared to the combined surgery group. However, no significant differences were observed between the two groups with respect to other complications (P > 0.05).

Methodology:

Searches were conducted in PubMed, Embase, Cochrane Library, and Web of Science to identify RCTs and high-quality comparative studies evaluating the therapeutic effects of PPV alone versus PPV combined with cataract surgery in patients with diabetes. Studies published in English up to April 2019 were included. The reference lists of identified articles were also scanned for additional relevant publications.

Two reviewers independently extracted data and resolved any disagreements through discussion. The methodological quality of the included studies was assessed using the Cochrane Collaboration’s risk-of-bias tool (for RCTs) and the modified Newcastle–Ottawa Scale (for retrospective studies). Findings were synthesised using a random-effects model meta-analysis. Heterogeneity was assessed using the chi-square test and the I² statistic. A sensitivity analysis was conducted to examine the influence of any single study on the pooled estimates.

Applicability/external validity: The authors highlighted that very few trials have been published on this issue, with only one RCT identified. This limited evidence potentially weakens the strength of the review’s findings. Additionally, some of the included studies were relatively dated and may not reflect current surgical techniques, which could affect the observed complication rates. The review emphasised the need for larger, well-designed prospective studies to confirm long-term outcomes across diverse clinical settings.

Geographic focus: The review did not apply any geographic restrictions. The included studies were conducted in Korea, the USA and Taiwan.

Summary of quality assessment: Overall, there is low confidence in this review’s conclusions regarding the comparative effects of PPV alone versus combined surgery. The review employed a comprehensive search strategy with clearly defined inclusion and exclusion criteria, and study characteristics were well presented. Data extraction was performed independently by two reviewers. The findings were synthesised using a random-effects meta-analysis, and heterogeneity was assessed using the chi-square test and the I² statistic, with sensitivity analyses also conducted. Additionally, study quality was assessed using valid and reliable tools.

However, the specific findings of the quality and risk-of-bias assessments were not reported. The review also did not specify whether article screening was conducted independently by two reviewers. Furthermore, the search was restricted to English-language publications, and no list of excluded studies was provided.