Beneficial effects of adjuvant intravitreal bevacizumab injection on outcomes of Ahmed glaucoma valve implantation in patients with neovascular glaucoma: systematic literature review

Methodological quality of the review: Low confidence

Authors: Hwang HB, Han JW, Yim HB, Lee NY

Region: Egypt, Saudi Arabia, Korea, Brazil, Turkey and China

Sector: Glaucoma

Sub-sector: Quality of clinical care

Equity focus: None specified

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Neovascular glaucoma (NVG) is a refractory glaucoma caused by neovascularization in the iris and the anterior chamber angle. It is secondary to retinal and anterior segment ischemia, such as that associated with proliferative diabetic retinopathy, central retinal vein occlusion, and ocular ischemic syndrome. Thus, it is important to treat both elevated intraocular pressure (IOP) and the underlying cause of the disease when managing NVG. Vascular endothelial growth factor (VEGF) is the main causative agent of neovascularization. Therefore, anti-VEGF treatment is anticipated to play an important role in the management of NVG.

Objectives:

Evaluated the effects of adjuvant intravitreal bevacizumab injection on the outcomes of Ahmed glaucoma valve (AGV) implantation in patients with neovascular glaucoma (NVG).

Main findings:

In total, the authors included six studies in the review. Three studies were retrospective and conducted in Korea, Turkey, and China, whereas the other three were prospective. Two were randomized controlled trials (RCTs). The follow-up duration ranged from 12 months to 2.4 years. The age of the patients ranged from 53.7 to 65.8 years. According to the authors, all studies had a Downs and Blacks score above 50%, fulfilling the quality criteria.

The differences in means and 95% confidence intervals of IOPR% of six studies, comparing surgery alone to adjuvant IVB with surgery in terms of the IOPR% of 1-year follow-up, forest plot showed the tendency that adjuvant bevacizumab treatment was more effective than only AGV implantation.

When the authors compared the outcomes of AGV implantation only with those of AGV implantation + adjuvant bevacizumab, a success rate in favor of AGV implantation + adjuvant bevacizumab was observed at the one-year follow-up. That is, the Mantel–Haenszel ORs of the success rates among the six studies comparing adjuvant IVB + surgery with surgery alone were in favour of adjuvant IVB.

The authors concluded that AGV implantation with adjuvant bevacizumab was more effective and had a higher success rate than surgery alone for lowering IOP in patients with NVG. The combined procedure tended to show a lower incidence of bleeding-associated complications, such as hyphema.

Methodology: 

The inclusion criteria for the published studies were as follows:

• design: controlled clinical study;
• population: patients with NVG who underwent AGV implantation;
• intervention: IVB injection before AGV implantation vs. AGV implantation alone; and
• outcome variables: including the percentage IOP reduction (IOPR%) at the 1-year follow-up was the primary outcome efficacy measure; mean value and standard deviation (SD) of the IOPR% were used when the authors reported these values directly. Complete success was defined as a target endpoint IOP without medications, and qualified success was defined as a target endpoint IOP with or without medications

The authors conducted a search of PubMed, EMBASE, and the Cochrane Library, with no date restrictions. In addition, they reviewed reference lists of original reports for additional studies.

Two authors independently extracted data and assessed the quality of included studies using a system reported by Downs and Blacks that assesses both randomized and non-randomized studies. The quantitative data were entered into a comprehensive meta-analysis software package. The pooled odds ratios (ORs) were calculated for dichotomous outcomes.

Applicability/external validity:

The authors did not discuss the generalizability of findings in the review.

Geographic focus:

The authors included studies from different income settings. However, they did not discuss how findings are applicable to low and middle-income countries.

Summary of quality assessment:

Low confidence is attributed to this review as important limitations were identified. The authors did not conduct a thorough search of the literature to ensure all relevant literature were identified. The authors did not avoid language bias and did not conduct a search for grey literature. In addition, they did not employ rigorous methods in screening of studies for inclusion.