Effect of AcrySof versus silicone or polymethyl methacrylate intraocular lens on posterior capsule opacification

Methodological quality of the review: High confidence

Author: Li N, Chen X, Zhang J, Zhou Y, Yao X, Du L, Wei M, Liu Y.

Region: Austria, Germany, Italy, Japan, Sweden and United Kingdom (UK)

Sector: Cataract (and glaucoma)

Sub-sector: Clinical outcomes

Equity focus: None specified

Review type: Systematic review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis methods: Not applicable

Background

Posterior capsule opacification (PCO) is the common complication of cataract surgery. A number of clinical studies have addressed the influence of different intraocular lenses (IOLs) on the incidence of PCO. Lenses are made of polymethyl methacrylate (PMMA), silicone, and acrylics have proven to be safe for implantation in patients. PMMA was the first very successful material used in IOLs; it is still widely used in Africa and Asia as it is very cheap to produce. Nevertheless, the issue of whether AcrySof IOLs were associated with significantly less PCO than other IOLs remains controversial.

Research objectives

To investigate the effect of AcrySof on the development of PCO compared with PMMA and silicone IOLs for patients with senile cataracts.  Secondary outcomes considered included Nd:YAG laser capsulotomy rate and postoperative best corrected visual acuity.

Main findings

A total of 10 randomized controlled trials comparing AcrySof IOLs with silicone or PMMA IOLs in patients with senile cataract were included in the review. These were conducted in several countries including Austria, Germany, Italy, Japan, Sweden and UK.

The results suggested that AcrySof had lower PCO scores than round-edged silicone IOLs (standard mean difference [SMD], -0.25; 95% confidence interval [CI], -0.42 to -0.08; P =0.003) and a somewhat higher PCO score than sharp-edged silicone IOLs (SMD, 0.48; 95% CI, 0.29–0.68; P<0.00001). AcrySof had a lower Nd:YAG laser capsulotomy rate than round-edged silicone IOLs (odds ratio [OR], 0.29; 95% CI, 0.14–0.62; P =0.001) and did not differ from sharp-edged IOLs (OR, 1.72; 95% CI, 0.23–13.13; P =0.60). AcrySof had a lower PCO score (SMD,-1.07; 95% CI, -1.29 to -0.85; P<0.00001) and a lower Nd:YAG laser capsulotomy rate (OR, 0.09; 95% CI,0.04–0.20; P<0.00001) than round-edged PMMA IOLs. Furthermore, there was no significant difference in best-corrected visual acuity (BCVA) between AcrySof and round-edged silicone IOLs (OR, 2.28; 95% CI, 0.66–7.82; P =0.19) or PMMA IOLs (OR, 3.20; 95% CI, 0.78–13.16; P =0.11).

Overall, authors concluded that the results of the meta-analysis support the theory that a major factor in preventing PCO development is a sharp-edged IOL design. Authors suggest that future research should be designed to differentiate between the benefits associated with materials and design in relation to PCO prevention.

Methodology

Authors inclusion criteria consisted of: (1)Randomized controlled trials; (2) patients with senile cataracts undergoing cataract surgery; (3) AcrySof IOLs intervention; (4) comparison: silicone or PMMA IOLs; (5) outcome variables: PCO Score, Nd:YAG laser capsulotomy rate, and number of eyes having BCVA of 0.5 or better; (6) articles written in English or Chinese.

A computerized systematic search was performed by two researchers independently in the PUBMED (1966-June 2006), EMBASE (1980-June 2006), Chinese Biomedicine Database (1979-June 2006), and Cochrane controlled trials register (June 2006). The search terms were posterior capsule opacification, after cataract, and secondary cataract. Literature reference proceedings were also searched. Two reviewers independently extracted data from each study into a customized form and conducted a methodological quality assessment.  The following methodological features were assessed: randomization, allocation concealment, blinding, withdrawals and drop-outs, intention-to-treat analysis, and sample size calculation.

Authors conducted a meta-analysis of the included studies; dichotomous data were presented as odds ratio with 95% CI; a p value <.05 was considered statistically significant. Heterogeneity between studies was also assessed using a chi-square test. A subgroup analysis was conducted according to the types of IOL materials and surgery.

Applicability/external validity

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

Geographic focus

Although authors did not restrict the searches to specific income settings, no low- and middle-income countries were included in the review. They only note in the review that PMMA IOLs are widely used in Africa and Asia as they are time tested and cheap to produce.

Quality assessment

Overall, there was high confidence in the conclusions about the effects of this study as minor limitations were identified. This review was based on comprehensive searches of the literature, although limited to articles written in English and in Chinese. Methods used to screen studies for inclusion and extract data were appropriately conducted minimizing bias. Authors noted that results from meta-analyses should be interpreted with caution because systems for the analysis of PCO and lengths of follow-up varied between studies; most studies reported limited information on randomization methods, and publication bias cannot be fully excluded.