A meta-analysis of neuroprotective effect for traditional Chinese medicine (TCM) in the treatment of glaucoma

Methodological quality of the review: Low confidence

Authors: Chao L, Na L, Bin L, Botao Z, Shuaijie L.

Region: China

Sector: Glaucoma

Sub-sector: Treatment

Equity focus:  None specified

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Glaucoma is a term for a group of eye disorders which result in damage to the optic nerve. The goals of glaucoma management are to avoid nerve damage and preserve visual field and total quality of life for patients with minimal side effects. At present, laser surgery, conventional surgery and medicine are used to treat glaucoma. Several clinical studies reported that clinical efficacy can be improved by surgery combined with traditional Chinese medicine (TCM) in the treatment of glaucoma.

Objectives:

The aim of this study was to evaluate the neuroprotective effect of surgery combined with traditional Chinese medicine (TCM) in the treatment of glaucoma by meta-analysis based on clinical controlled trial.

Main findings:

In total, the authors included 11 clinical studies, with 457 cases in the surgery + TCM and 386 subjected in the control group, in the meta-analysis. The authors found the pooled analysis of nine studies, which reported on vision recovery rate, showed that surgery combined with traditional Chinese medicine treatment procedure can significantly improve the vision recovery rate compare to control group (risk ratio (RR)=1.22, 95% confidence interval (CI):1.06~1.40, P=0.005).

The authors note that pooled analysis of six studies included paper on the meta-analysis, which reported data of visual field improvement, indicated that visual field in combined group was significantly improved compared to control group (standard mean difference (SMD)=0.26，95% CI:0.09~0.43, P=0.003).

The authors note that no significant heterogeneity was identified in the effect size of RR (I²=0.00%, P=0.647). In addition, they did not identify statistical heterogeneity in the meta-analysis (I²=39.6%, P=0.142). Based on the Begg’s funnel plot, the authors identified a small amount of asymmetry at the bottom. However, based on the Egger’s test, they noted no significant publication bias.

Methodology: 

The authors inclusion criteria for this meta-analysis was as follows:

(1) patients included in each individual study were diagnosed of glaucoma with no restriction of age and gender.

(2) The treatment was surgery + TMC in the experiment group and surgery alone or surgery + western medicine in the control group.

(3) The outcomes were vision recovery rate and visual field improvement. The study design was prospective clinical trials without restriction of randomization.

The authors searched Medline, the Cochrane central register of controlled trials, EMBASE and CNKI databases, published before January 2015. The searching term was glaucoma [MeSH]/glaucoma [text]; Chinese medical[MeSH]/Chinese medical[test]; Chinese medicine [MeSH]/Chinese medicine[test]. The authors evaluated the title and abstract of identified studies for eligibility, followed by full-text assessment of all potentially relevant trials. In addition, the authors reviewed references of included articles as part of the search strategy. All data of included studies were extracted by two reviewers independently.

In terms of statistical analysis, the authors calculated dichotomous data as risk ratio (RR) with 95% confidence interval (CI). Measurement data was demonstrated by mean with its standard difference and pooled by standard mean difference (SMD). Statistical heterogeneity of the results across the included studies was evaluated by Chi-square (χ2) test, and the inconsistency was calculated by I². The authors note that if heterogeneity was found (χ2, p<0.05 or I²>50%), the random-effect method (Dersimonian-Laird method) was used to pool the data. Otherwise, without significant heterogeneity, fixed-effect method was used. To evaluate publication bias, the authors performed the Egger’s tests.

Applicability/external validity:

The authors do not discuss the generalizability of the results in the review.

Geographic focus:

The authors note that all 11 included studies were conducted in China with a patient ethnicity “Han”.

Summary of quality assessment:

Overall, there is low confidence in the conclusions about the effects of this study. The authors did not conduct a thorough search of the literature to ensure all relevant studies were identified for inclusion. In addition, it is not clear if language bias was avoided in the review and authors restricted inclusion of studies based on publication status. Authors did not use rigorous methods to screen studies for inclusion and did not assess the methodological quality of included studies. Therefore, it is not clear if included studies have low or high risk of bias.