Synthesis of the literature on visual acuity and complications following cataract extraction with intraocular lens implantation

Methodological quality of the review: Medium confidence

Author: Powe NR, Schein OD, Gieser SC, Tielsch JM, Luthra R, Javitt J, Steinberg EP.

Region: Details not provided

Sector: Age-related cataract

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

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

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 [Phaco], extracapsular cataract extraction [ECCE] and intracapsular cataract extraction [ICCE] with anterior chamber lens) by analysing the evidence on clinical outcomes: visual acuity and complications; and to analyse the difference in cataract surgical outcomes according to the surgical technique used.

Main findings

The review included 90 studies that addressed either visual acuity or complications following cataract extraction. Seven (8%) of the 90 included studies were cohort studies (that is, 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 pre-existing 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 oedema, 1.5%; and retinal detachment, 0.7%.

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

Methodology

Inclusion criteria consisted of clinical trials or observational studies with primary data collection published between 1975 and 1991 and addressed standard ECCE with posterior chamber IOL implantation or Phaco with posterior chamber IOL implantation. It also included  articles published in 1980 or later and addressed ICCE with flexible anterior chamber IOL implantation. A study was eligible if it 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 was not clear whether this was conducted independently. Included studies underwent a structured review to assess rigour of the methods reported in these studies conducted by two authors independently.

To compare proportions of eyes experiencing complications with Phaco 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) and for cohort studies and clinical series combined. A 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 did not clearly discuss the generalizability of findings and did not illustrate methods to assess applicability.

Geographic focus

The authors did not provide geographic focus details of included studies.

Quality assessment

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