Use of global visual acuity data in a time trade-off approach to calculate the cost utility of cataract surgery

Methodological quality of the review: Medium confidence

Author: Lansingh VC, Carter MJ.

Region: Australia, South America, Asia, Europe, India, Africa and North America

Sector: Cataract surgery

Sub-sector: Cost-utility of cataract surgery

Type of cataract: Age-related cataract

Equity focus: None specified

Review type: Cost-utility review

Quantitative synthesis method: Narrative analysis and data synthesis

Qualitative synthesis methods: Not applicable

Background

Cost-effectiveness studies can help to quantify the effect of a treatment, such as cataract surgery, in terms of quality of life perspective as well as ways to inform decision-making in healthcare. Authors also note that the time trade-off approach to calculating utility ‘better correlates with vision and quality of life issues in comparison with self-assessment scales’.

Research objectives

To determine the cost utility of cataract surgery worldwide using visual acuity (VA) outcomes and utility values determined by the time trade-off (TTO) method.

Main findings

It was not clear how many studies and types of studies were identified for inclusion in the study. Authors noted that all articles were included if the data was seen as useable, otherwise the studies were discarded. Studies included were conducted in Australia, South America, Asia, Europe, India, Africa, and North America. Authors reported the following results:

Preoperative VA correlated with increasing gross national income per capita (Pearson correlation coefficient -0.784; P <.001) and preoperative vision in developing countries is much poorer compared to developed countries. In developing countries, Uganda and Kenya were identified as having the largest differences between preoperative and postoperative VA whilst smallest differences were found in China and Ethiopia.

Data synthesis results identified that ‘Cost utility data ranged from US$3.50 to $834/quality-adjusted life years (QALY) in developing countries to US$159 to $1356/QALY in developed countries’.  One study indicated the smallest QALY gain in China (0.381) while the largest gain was identified by one study in Nepal (3.042 QALYs).

Overall, authors concluded that the Time Trade-Off (TTO) approach demonstrated that cataract surgery was extremely cost effective across developed and developing countries.

Methodology

Authors included any study where data seemed ‘useable’, otherwise they were discarded. The types and number of studies were not reported in full. Authors noted that they used MEDLINE, Scopus and Google and there were no language restrictions. Other details around the search strategy were not included in the review.

Authors used Time Trade-Off (TTO) derived utility values for a scale of VA from 20/20 to no light perception in the better-seeing eye to investigate the cost utility of cataract surgery. Authors used outcome data from a number of different studies from both developed and developing countries.

Applicability/external validity

The authors did not specifically address applicability and external validity of the study. However, authors note that some results for countries included in the study only use data from one study identified, which puts into question the accuracy of the data and may indicate that findings were not necessarily universally applicable to a country setting.

Geographic focus

The review uses data from studies conducted in Australia, South America, Asia, Europe, India, Africa, North America and therefore included studies from both low-, middle- and high-income settings and identified results specifically on low- and middle-income settings as described in section ‘Main findings’ above.

Quality assessment

Medium confidence was attributed in the conclusions of this study. It should be noted that this was a cost-utility study which sought to calculate the cost utility of cataract surgery and not systematically review the included studies. Therefore, full details of the included studies were not reported and the study largely reports relevant outcomes of included studies to calculate cost utility. Authors searched MEDLINE and Scopus for most recent data and there were no language restrictions. It is not clear if the studies included for their relevant data outcomes were screened and assessed by two reviewers independently. There was limited reporting of quality appraisal around the included reviews, although authors noted that data was not used unless it was either government data or authored by a person who had previously published in peer-reviewed ophthalmology or health economics journals.

Limitations were acknowledged by the reviewers. For example, for some countries only one study was used to calculate outcomes which would indicate that findings of those countries may be more inaccurate than those countries which offered more breadth of data. The study also only focussed on direct cataract surgery costs because there was little data available on other costs in developing countries. Authors concluded that the ‘realistic cost of utility of cataract surgery is, therefore, higher (for example, cost of QALY gained) than we have presented, although we do not believe this materially affects our conclusion’.