Effect of heparin-surface-modified introcuolar lenses on posterior capsular opacification: meta-analysis of randomized clinical trial

Methodological quality of the review: Medium confidence

Author: Cheng J, Ye X, Wei R, Cai J, Li Y.

Region: China

Sector: Cataract surgery

Sub-sector: None specified

Type of cataract: Age-related cataract

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis methods: Not applicable

Background

Posterior capsular opacification (PCO) is a common complication after cataract surgery. Binding heparin to the polymethylmethacrylate (PMMA) surface appears to decrease foreign-body-induced inflammation by making the intraocular lens (IOL) more hydrophilic, and therefore it may play a role in reducing PCO.

Research objectives

To evaluate the efficacy of heparin-surface-modified (HSM) PMMA IOL in preventing PCO after cataract extraction.

Main findings

Authors included 12 randomized controlled trials which compared HSM PMMA IOL against PMMA IOL in the review.

Based on the meta-analysis, authors reported that the HSM PMMA IOL appears to be as effective as conventional unmodified PMMA IOL in preventing the formation of PCO and reducing the use of Nd:YAG laser capsulotomy.

Methodology

This review is based on a search of several databases including Cochrane Library, PUBMED, MEDLINE, EMBASE and Chinese Biomedical Database (CBM) (1966 to 2006). No language restriction was imposed and reference lists of relevant trials were reviewed. Titles and abstracts resulting from the searches as well as data collection of included trials were independently reviewed by authors.

Authors included randomized control trials comparing HSM PMMA IOL against unmodified PMMA IOL in post-operative cataract patients. Outcome measures included PCO rates and Nd:YAG laser capsulotomy rates after cataract surgery. The search words used to conduct the search included words in English such as: ‘heparin surface modified’, ‘heparin surface modification’, ‘heparin coated’ and ‘heparinized’; and words in Chinese including ‘Heparin’ and ‘IOL’. Authors did not report using any grading criteria to quality assess included studies, however, studies’ background information was provided.

Authors conducted a meta-analysis and a heterogeneity test using random effects models.

Applicability/external validity

Authors did not discuss the applicability/external validity of findings.

Geographic focus

Authors covered a range of countries in the review, including from China. However, they did not discuss it further.

Quality Assessment

Overall, medium confidence was attributed to the conclusions about the effects of this study. Although authors did not contact experts/authors as part of the search strategy, the literature search was thorough with no language or date restrictions. Methods used to screen studies and extract data of included studies were appropriately conducted, minimizing the risk of bias. However, methods used to analyse findings were unclear. There are also many influencing elements to the usage of YAG laser, which were not mentioned at all at the paper. The background of studies (for instance the surgeons, the method to grade PCO, etc.), were not given and analysed, which are very much related to happening of PCO. Nevertheless, overall authors acknowledged the limitations of the study.