Interventions for preventing posterior capsule opacification

Methodological quality of the review: High confidence

Author: Findl O, Buehl W, Bauer P, Sycha T.

Region: Germany, Turkey, Israel, USA, UK, Austria, Japan, Pakistan, Sweden, Italy, Finland, India, China, Denmark and Lithuania

Sector: Age-related cataract

Sub-sector: Surgery, clinical outcome

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 capsule opacification (PCO) remains the most common long-term complication after cataract surgery. It can be treated by Nd:YAG laser capsulotomy, (Nd:YAG), although this may lead to other complications and laser treatment is not available in large parts of the developing world.

Research objectives

To summarize the effects of different interventions to inhibit PCO, including  modifications of surgical technique and intraocular lens (IOL) design, implantation of additional devices and pharmacological interventions.

Main findings

The review included 66 studies. The review was divided into three parts.

1. Influence of IOL optic material on the development of PCO. There was no significant difference in PCO development between the different IOL materials (PMMA, hydrogel, hydrophobic acrylic, silicone) although hydrogel IOLs tend to have higher PCO scores and silicone IOLs lower PCO scores than the other materials.
2. Influence of IOL optic design on the development of PCO. There was a significantly lower PCO score (-8.65 (-10.72 to -6.59), scale 0 to 100) and Nd:YAG rate (0.19 (0.11 to 0.35)) in sharp-edged than in round-edged IOLs, although not between one-piece and three-piece IOLs.
3. Influence of surgical technique and drugs on the development of PCO. There was no significant difference between different types of intraoperative/postoperative anti-inflammatory treatment except for treatment with an immunotoxin (MDX-A) which led to a significantly lower PCO rate.

Authors concluded that ‘Due to the highly significant difference between round and sharp edged IOL optics, IOLs with sharp (posterior) optic edges should be preferred. There is no clear difference between optic materials. The choice of postoperative anti-inflammatory treatment does not seem to influence PCO development.’

Authors noted that further efforts should be directed to the question of whether there was a difference between the currently widely used IOL materials (hydrophobic acrylic and silicone). There were still no prospective RCTs focusing on the effect of posterior capsule polishing, capsular tension rings and primary posterior capsulorhexis on PCO, nor on the effect of drugs on PCO. It had also become obvious that it was important to use a standardized method for quantification of PCO. A common PCO scoring method would make the comparison of different trials easier.

Methodology

Authors included only prospective, randomized and controlled trials with a follow-up time of at least 12 months. Interventions included modifications in surgical technique explicitly to inhibit PCO, modifications in IOL design (material and geometry), implantation of additional devices and pharmacological therapy compared to each other, placebo or standard treatment. Participants consisted of people with age-related cataract without prior sight threatening ocular disease (glaucoma, corneal disease, uveitis, traumatic or complicated cataract, retinal disease or history of diabetes mellitus with diabetic retinopathy) who underwent cataract surgery with implantation of an intraocular lens into the capsule bag. Primary outcome measure consisted of best corrected visual acuity (BCVA) and secondary consisted of PCO intensity and proportion of people needing capsulotomy.

Authors conducted a search on Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (January 1950 to March 2009), EMBASE (January 1980 to March 2009) and Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to March 2009). No language restrictions were applied. The electronic databases were last searched on 27 March 2009.

Two review authors independently extracted data onto forms developed by the Cochrane Eyes and Vision Group. The authors compared these and resolved discrepancies by discussion. One author entered data into RevMan (Cochrane software). Authors of included studies were contacted for missing information within a period of two months.

Authors conducted a meta-analysis. Data from studies collecting comparable outcome measures with similar follow-up times was summarized. Dichotomous outcomes were presented as odds ratios or risk ratios, and continuous outcomes as the mean difference. A random-effects model was used, unless there were fewer than three trials in a comparison when we used a fixed effect model was used. Heterogeneity was examined between trial results using a chi-square test. If detected, either by the test or clinically within the trials, it was mentioned in the results section of the review.

Applicability/external validity

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

Geographic focus

Authors included studies from all income settings but did not discuss findings in relation to low- and middle- income countries.  

Quality Assessment

This review is based a reasonably comprehensive search of the literature and appropriate methods to reduce risk of bias in terms of study selection, data extraction and analysis. No limitations were identified in the review; therefore there is high confidence in the conclusions about the effects of this study.