Surgical interventions for age-related cataract

Methodological quality of the review: High confidence

Author: Riaz Y, Mehta JD, Wormald R, Evans JR, Foster A, Ravilla T and Snellingen T.

Region: Europe, Far East, Indian subcontinent and Africa

Sector: Age-related cataract

Sub-sector: Surgical interventions

Type of cataract: Age-related cataract

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Narrative analysis & meta-analysis

Qualitative synthesis methods: Not applicable

Background

Cataract continues to be a leading cause of blindness globally, with the majority of blinding cataract being found in low-income settings. The incidence of cataract is expected to grow due to an aging population and due to unsuccessful attempts to control this condition in low- and middle-income countries. There are currently four main types of cataract extraction surgery available: intracapsular (ICCE), extracapsular (ECCE), phacoemulsification (Phaco) and manual small incision (MSICS). ICCE is widely used in the developing world whilst Phaco is the most common method of extraction in the developed world.

Research objectives

The aim of this review was to examine the effects of the main types of surgery currently used to treat age-related cataract.

Main findings

‘The review authors searched the medical literature and identified 17 randomised controlled trials (9627 participants) investigating the different surgical interventions. Six of these trials suggested that PHACO gives a better outcome than ECCE. They suggest a better uncorrected visual acuity (UCVA) following PHACO than ECCE but the majority of the trials showed no difference in best-corrected visual acuity (BCVA) between the two groups. The costs per procedure were not markedly different between the two techniques in a UK based study, however, a Malaysian study showed ECCE to be significantly cheaper. A study comparing MSICS and ECCE, advocated MSICS as the procedure of choice due to equal costs and better visual results. Two studies compared the results of PHACO and MSICS. Phacoemulsification having a significantly higher proportion of patients with UCVA > 6/18 (81.1% versus 71%) but there was no difference in BSCVA. Trials comparing costs of PHACO and MSICS are important for future research. Manual small incision surgery offers an alternative technique in developing countries as it provides acceptable visual outcomes when compared to PHACO yet is likely to be more economical as it avoids the initial outlay of costs of PHACO. It is important to remember that the studies in this review were based in a variety of countries and situations (hospital based or cataract camps); a knowledge of the setting is vital before drawing conclusions from the data’.

Authors noted that statistical analysis in the review was challenging because of the heterogeneity of the outcome data and varying follow-up times recorded. As a result, authors suggested that for future research, standardized criteria for reporting results (especially Phaco trials) should be established. For example both UCVA and BCVA should be recorded and standard time intervals for reporting should be established. They also noted that it would be useful to assess quality of life, overall visual function and time taken to resume normal daily activities not just visual acuity alone.

Methodology

The review included randomized control trials investigating different surgical interventions for cataract extraction. The majority of trial participants were over 40 years old (with the exception of three studies where participants were over 55 years and two studies where participants were aged over 68 years). All participants were people with age-related cataract, with no restriction on demographic characteristics.

Primary outcomes of the review included: late postoperative visual acuity at one year or more after surgery (the proportion of people with a poor visual outcome after surgery and the proportion of people not achieving good functional vision).

Secondary outcomes included: (1) Early post-operative visual acuity at four to 12 weeks after surgery; (2) Complications during surgery; (3) Complications at one year or more after surgery; (4) Corneal endothelial cell loss; (5) Visual function other than visual acuity; (6) Quality of life; and (7) Costs.

The authors conducted a systematic search of literature on various databases, including CENTRAL, MEDLINE, EMBASE and National Research Register (NRR). They also checked reference lists of included studies and contacted the investigators of included trials for additional information on unreported trials. Searches were conducted without any language restrictions. At least two authors independently screened titles from searches and extracted data from included studies. The two authors independently conducted an assessment for bias, using the guidelines detailed in Chapter 6 of the Cochrane handbook for Systematic Reviews of Interventions (Higgins 2005).

Authors assessed heterogeneity of trials using a chi-squared test and if trials were too different, did not combine results. Authors pooled data for some secondary outcomes; such as complications during surgery and clinical complications in trials that compared Phaco with Posterior chamber intraocular lens (PCIOL) versus ECCE with PCIOL. As there were not enough trials included in the review, sensitivity analysis was not conducted.

Applicability/external validity

Authors noted that the trials included in the review covered a wide range of countries, from high income and low- to middle-income settings. It was noted that even within low- and middle-income settings, such as in the Indian subcontinent, there was a marked difference between results from cataract camps and hospital-based treatments and that knowledge of setting was imperative when interpreting results and assessing applicability. It noted that some studies would be more representative of ‘usual surgical practice’ and would therefore have greater external validity.

Geographic focus

The review focussed on a range of countries in Europe, Far East, Africa and the Indian subcontinent but recognizes that the majority of trials were conducted in developed countries ‘in a specialized hospital setting’. Nevertheless, authors assessed results that would be applicable /useful to low- and middle-income settings. For example, it was found that manual small incision cataract surgery offered an ‘appealing’ alternative to developing countries as it achieved a ‘similar visual outcome results to Phaco but is less expensive’.

Authors also recognized that further research was needed from developing countries which compared each of the four main surgical extraction procedures.

Quality assessment

There was high confidence in conclusions about the effects of this review as a minor limitation was identified. Although authors did not report the time period of the search conducted, this systematic review was based on comprehensive searches. Methods used to screen studies for eligibility, extract data and quality assess included studies were appropriately conducted, minimizing risk of bias.