Rigor of research methods in studies of the effectiveness and safety of cataract extraction with intraocular lens implantation.

Author: Powe N, Schein O, Gieser S, Tielsch J, Luthra R, Javitt J, Steinberg E.

Region: Details not provided

Sector: Age-related cataract

Sub-sector: clinical outcomes (visual acuity, complications)

Equity focus: None specified

Review Type: Effectiveness Review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis methods: Not applicable


Cataract extraction with intraocular lens (IOL) implantation is highly effective and successful. However, some of the complications from cataract surgery can result in significant visual impairment as well as additional health care costs.

Research Objectives

To report the best available evidence on the effectiveness of cataract surgical techniques (Phacoemulsification, ECCE and ICCE with anterior chamber lens ) by analyzing the evidence on clinical outcomes: visual acuity and complications; and to analyze the difference in cataract surgical outcomes according to the surgical technique used.

Main Findings

90 studies that addressed either visual acuity or complications following cataract extraction were included in the review. Seven (8%) of the 90 included studies were cohort studies (i.e., they compared outcomes in two or more groups of patients). The remaining 83 studies (92%) were clinical series.

The pooled percentage of eyes (weighted by sample size) with postoperative visual acuity of 20/40 or better was 95.5% (95% confidence interval [CI], 95.1% to 95.9%) among eyes without preexisting ocular comorbidity, and 89.7% (95% CI, 89.3% to 90.2%) for all eyes.

The pooled percentage of eyes experiencing complications (weighted by sample size and, when pertinent, by quality score of the individual studies but not adjusted for variation in duration of follow-up) ranged from 0.13% for endophthalmitis to 19.7% for posterior capsule opacification. Pooled proportions of eyes with other complications were as follows: bullous keratopathy,0.3%; intraocular lens malposition/dislocation, 1.1%;clinically apparent cystoid macular edema, 1.5%; and retinal detachment, 0.7%.

Overall, authors concluded that modern cataract surgery results in excellent visual acuity and is a safe procedure regardless of the extraction technique used. For future research, authors suggest the standardization of the visual acuity measurement; better reporting of the number of eyes and patients; report other measures of overall functional status besides VA and post-surgery recovery time and uncorrected VA to be considered as outcomes.


Inclusion criteria consisted of clinical trials or observational studies with primary data collection published between 1975 and 1991 and addressed standard extracapsular cataract extraction with posterior chamber IOL implantation or phacoemulsification with posterior chamber IOL implantation; or article published in 1980 or later and addressed intracapsular cataract extraction with flexible anterior chamber IOL implantation. Study was eligible if also addressed either visual acuity or complications of cataract surgery and was written in English.

Authors conducted a two-phased computerized search of Medline database, the first search was supplemented with a second computerized search performed by an experienced librarian, a search of the bibliographies of published and unpublished studies, a search of the bibliographies of articles included in the review, and a search of the references in the included studies.  Study selection and data abstraction was conducted by two authors; however it is not clear whether this was conducted independently. Included studies underwent a structured review to assess rigor of the methods reported in these studies conducted by two authors independently.

To compare proportions of eyes experiencing complications with PE vs ECCE pooled results and the corresponding 95% CI were calculated separately for cohort studies (using the pooled log-odds ratio method of Mantel-Haenszel’1) and for cohort studies and clinical series combined. Test of homogeneity for consistency of treatment effects was used to assess the appropriateness of pooling of results of cohort studies.

Applicability/external validity

The review does not clearly discuss the generalizability of findings and does not illustrate methods to assess applicability.

Geographic focus

Geographic focus details of included studies not provided.

Quality Assessment

Authors used rigorous methods to select studies, extract data and quality assess included studies; and methods used to analyze findings were clearly reported. However this review has some limitations. The search for literature, while covering reference/bibliographies lists and contacting authors for additional trials, authors did not avoid language bias and conducted a search on a single database only. Therefore, medium confidence was attributed in the conclusions about the effects of this study.

Publication Details Powe N, Schein O, Gieser S, Tielsch J, Luthra R, Javitt J, Steinberg E. Rigor of research methods in studies of the effectiveness and safety of cataract extraction with intraocular lens implantation. Cataract Patient Outcome Research Team. Arch. Ophthalmol. 1994;112:239-52. Source