Surgery for cataracts in people with age-related macular degeneration

Methodological quality of the review: High confidence

Author: Casparis H, Lindsley K, Kuo IC, Sikder S, Bressler NB.

Region: Australia

Sector: Cataract surgery

Sub-sector: AMD

Type of cataract: Age-related cataract

Equity focus: None specified

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable 

Background:

Cataract and age-related macular degeneration (AMD) are common causes of decreased vision that often occur simultaneously in people over age 50. Although cataract surgery is an effective treatment for cataract-induced visual loss, some clinicians suspect that such an intervention may increase the risk of worsening of underlying AMD and thus have deleterious effects on vision, mainly based on anecdotal events in which development of neovascular AMD (the ‘wet’ form) is noted in an eye soon after cataract surgery.

Research objectives:

The objective of this review was to evaluate the effectiveness and safety of cataract surgery in eyes with AMD.

Main findings:

Authors included only one randomized controlled trial (RCT) in the review, which enrolled 60 participants with visually significant cataract and AMD. Authors note that participants in this trial were randomized to immediate cataract surgery (n=29) or delayed cataract surgery (six months after enrollment) (n=31). The study was conducted at the Royal Victorian Eye and Ear Hospital in Melbourne, Australia.

Authors note that methods of randomization of the study were not reported and participants were not masked. Incomplete outcome data was reported and although a protocol of the included study was not available, authors mention that all assessed measures of the trial were reported.

Based on findings of the trial included, authors reported that at six months, greater mean best-corrected distance visual acuity (BCVA) was observed in the immediate surgery group compared with the delayed surgery control group (mean difference (MD) −0.15 LogMAR, 95% confidence interval (CI) −0.28 to −0.02). Authors note that there was no significant difference in the development of choroidal neovascularization (CNV) between groups (1/27 eyes in the immediate surgery group versus 0/29 eyes in the delayed surgery group). At six months, based on the results from Impact of Vision Impairment (IVI) questionnaires authors reported that the immediate surgery group fared better with quality of life outcomes than the delayed surgery group (MD in IVI logit scores 1.60, 95% CI 0.61 to 2.59). The authors did not report adverse outcomes.

Authors of the review concluded that at the time of writing, it was not possible to draw reliable conclusions from the available data to determine whether cataract surgery is beneficial or harmful in people with AMD. They also state that physicians will have to make practice decisions based on best clinical judgement until controlled trials are conducted and their findings are published.

Methodology:

Inclusion criteria consisted of RCTs and quasi-randomized trials in eyes with AMD that also had cataract and required cataract surgery. Authors included trials where cataract surgery was compared to no surgery, and authors imposed no restriction based on the type of cataract surgery. Primary outcome measure for this review was visual acuity in the operated eye a one-year follow-up; and secondary outcome measure included progression of AMD in the operated eye, vision-related quality of life and vision-threatening complications from cataract surgery. Secondary outcomes were analysed at 6 months and one, two and three years follow-up when possible.

Authors conducted a search on several databases including CENTRAL, EMBASE, LILACS, the meta Register of Controlled Trials (mRCT), ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform. There were no language or date restrictions in the search for trials. The electronic databases were last searched on 16 April 2012. In addition, authors also searched the reference lists of included studies and related observational studies and reviews.

Two reviewers independently selected studies for inclusion and extracted data of includes studies. Two authors independently assessed the included trials for bias according to the Cochrane Handbook for Systematic Reviews of Interventions.

To measure treatment effect, for dichotomous outcomes authors calculated a risk ration with 95% CIs; they calculated a mean difference with standard deviations for continuous outcomes. In case of missing data, authors conducted the primary investigators. Authors note that as only one study was included in the review, heterogeneity and reporting bias were not assessed and data was not synthesized.

Applicability/external validity:

Authors state that no study with long-term follow-up (at least one year) was identified for their search. The best available evidence for the published literature was one RCT with six months follow-up.

Geographic focus:

The included study was conducted in Australia, although as only one study was included in the review, findings may not be generalizable or applicable to other settings.

Quality assessment:

High confidence was attributed in the conclusions in relation to the intervention effects of this review. Authors conducted a thorough search of the literature to ensure that all potentially relevant studies were included in the review avoiding biases. Appropriate methods were used to screen, extract data and assess risk of bias of included studies. As only one study was included in the review authors did not draw strong conclusions.