A systematic overview of the incidence of posterior capsule opacification

Methodological quality of the review: Low confidence

Author: Schaumberg DA, Dana MR, Christen WG, Glynn RJ.

Region: Details not provided

Sector: Cataract

Sub-sector: Clinical outcomes/complications

Type of cataract: Age-related cataract

Equity focus: None specified

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis methods: Not applicable

Background

Posterior capsule opacification (PCO) is the most common long-term complication of extracapsular cataract surgery techniques and probably the most common cause of non-refractive decreased postoperative vision. Reported rates of PCO vary widely. This study is a meta-analysis of the studies addressing PCO. It aims to give a more precise estimate of the rate of PCO and explore factors that might influence it.

Research objectives

To estimate the pooled incidence of PCO after extracapsular cataract surgery.

To explore the factors that might influence the rate of PCO.

Main findings

Authors included 49 studies reporting on postoperative rates of PCO with some measure of the length to follow up.

Visually significant PCO develops in more than 25% of patients undergoing standard extracapsular cataract extraction or phacoemulsification with posterior chamber intraocular lens (IOL) implantation over the first five years after surgery. Patient characteristics, surgical techniques, and differences in research design and reporting may account for some of the variability in reported rates. However, no specific factors were identified in the authors ’analysis.

Authors noted that there is a need to standardise the measurement of PCO and methodologies in further studies.

Methodology

Authors included studies written in English, published between 1979 and 1996, which reported the sample size and postoperative rate of PCO along with some measure of the length of follow-up. Authors conducted a search of MEDLINE and of the bibliographies of relevant articles.

The methodology used to summarize the data was meta-analysis. Studies were pooled together depending on the length of follow-up reported: one, three and five years after surgery. After performing homogeneity tests (chi-square test), pooled rates were estimated using the weighted average method and reported with 95% confidence intervals. Three different weights were used for comparison: weights equal to the inverse variance and among-study variance; equal weights regardless of the study size; and weights equal to the sample size.

Both linear regression models and models weighted by the inverse total variance were used to examine the relationship of time since surgery and PCO incidence. Linear regression models for the one-year period were used to investigate other factors like type of surgery, type of IOL material, visual threshold to perform Nd:YAG capsulotomy and percentage of lost to follow-up. Separate analysis using the Mantel- Haenszel approach was used to estimate a pooled relative risk of PCO for convex posterior versus plano posterior IOL surface.

Applicability/external validity

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

Geographic focus

Authors did not focus on a specific country setting and geographical locations of included studies were not reported.

Quality assessment

Important limitations were identified in the methods used to conduct this review. The literature search, although covering bibliographies and one database, was not sufficiently comprehensive that we can be confident that relevant studies were not omitted. Methods used to select studies and extract their data were not reported. Additionally, as the authors did not report the study design of included studies in the review, the appropriateness of the meta-analysis is inconclusive. Thus, low confidence in the conclusions about the effects is attributed to this review.