Methodological quality of the review: Low confidence
Author: Wang W, Yan W, Fotis K, Prasad NM, Lansingh VC, Taylor HR, Finger RP, Facciolo D, He M.
Sector: Cataract prevalence
Sub-sector: surgical rate, economic development
Type of cataract: Age-related cataract
Equity focus: None specified
Quantitative synthesis method: Narrative synthesis
Qualitative synthesis method: Not applicable
Cataract is the leading cause of blindness and surgical intervention can effectively restore visual impairment. Cataract surgical rate (CSR,) which is defined as the number of cataract operations performed per million population in 1 year, is used as a proxy indicator of access to cataract services in a country.
The aim of this study was to explore the associations between the CSR and the economic development of countries in terms of gross domestic product per capital (GDP/P) and gross national income per capita (GNI/P).
Authors reported that CSR data were retrieved successfully for 152 countries between 2005 and 2014. While some CSR data were extracted from published papers, the majority of the data were extracted from WHO and NGO reports, although authors note that further details of how these data were collected were largely unavailable. Furthermore, there were very few reports available for 2013 and 2014.
Authors noted that the CSRs reported between countries varied greatly, with the lowest being the Democratic Republic of Congo (78 per million) and the highest being France (11,080 per million). Using United Nations population estimations, the 50 countries with the largest populations and available CSR and GDP/P data between 2005 and 2009 were included in the regression analysis. The regression analysis conducted by the authors showed that of the 50 most populous countries with CSR data were significantly correlated with GDP/P (b¼0.173, Linear: y¼0.173xþ250.531; R2¼0.670, P< 0.001). The regression line indicated that countries such as Iran, India, and Nepal had CSRs that was greater than their GDP/P model estimates, while China and Saudi Arabia tended to have lower than expected CSRs when measured against the model estimates.
Between 2009 and 2014, India and Argentina maintained CSRs that were consistent with economy-based projection using the GDP/P regression line; however China, South Africa, Mexico, and the Republic of Korea were all positioned below their economy projected CSRs using this model.
For the period between 2005 and 2009, the regression analysis of the 50 most populous countries with CSR data showed that CSRs were significantly correlated with GNI/P (b ¼ 0.172, Linear: y ¼ 0.172x þ 283.132; R2 ¼ 0.656, P < 0.001). For the period between 2010 and 2014, the regression analysis of the 50 most populous countries with CSR data showed that CSRs were significantly correlated with GNI/P (b¼0.215, Linear: y¼ 0.215x þ 68.432; R2 ¼ 0.813, P < 0.001). The CSR in 13 countries decreased as GDP/P increased (Uganda, Botswana, Sierra Leone, Togo, South Africa, Congo, Vanuatu, Guatemala, Philippines, Nigeria, Lao People’s Democratic Republic, Kenya, Zambia), though it is worth noting that these countries were all relatively small by population size.
Authors state that considering this relationship, it is important to innovatively deliver low-cost services and invest strategically in capacity development to meet the cataract surgical need in low-resource settings.
Authors conducted a thorough search of databases including OVID (Medline and Embase), Pubmed, Embase.com, ISI Web of Science, and Cochrane Library databases. The websites of nongovernment organizations (NGOs) were also used to retrieve data. These included the Rapid Assessment of Avoidable Blindness (RAAB), Rapid Assessment of Cataract Surgical Services (RACSS) data, Global Burden of Disease, Global health data exchange, WHO Library Information System, IAPB website, OpenGrey, as well as the Ministry of Health websites for some countries. In addition, authors also reviewed references of included studies as part of the search strategy.
Studies published from January 2000 to December 2015 were considered for inclusion into the review. There was no language restriction in the search, and any studies meeting the inclusion criteria were included for statistical analysis. The inclusion criteria for published studies were: (1) national or population-based samples, (2) cross-sectional studies, cohort studies, or surveys with a clear sampling methodology, (3) sufficient response rate (50% or greater), and (4) samples representative of populations in a country or region. Case series of hospital and clinic data were excluded.
Countries were divided into six regions according to the WHO classification Africa, the Americas, South-East Asia, Europe, the Eastern Mediterranean, and the Western Pacific. Authors retrieved the relevant economic data in international dollar units of 2011, using the World Bank website.
Data extraction was performed using a standardized data extraction form. Extracted fields included region and country in which the study was conducted, year of publication, year of data collected, age, number of people examined and CSRs with 95% confidence intervals.
All statistical analyses were conducted using the SPSS software package. Cataract surgical rates were analyzed in two time frames: 2005-2009 and 2010 to 2014.
Authors note that CSR and economic indicators (GDP/P, GNI/P) appear to be closely associated, indicating the strong influence of resource availability on healthcare delivery.
Authors indicated that countries such as Iran, India, and Nepal had CSRs that were higher than their GDP/P model estimates, while China and Saudi Arabia tended to have lower than expected CSRs when measured against the model estimates. In addition, authors reported that the CSR in 13 countries decreased as GDP/P increased (Uganda, Botswana, Sierra Leone, Togo, South Africa, Congo, Vanuatu, Guatemala, Philippines, Nigeria, Lao People’s Democratic Republic, Kenya, Zambia), though it is worth noting that these countries were all relatively small by population size.
Overall there is low confidence in the conclusions about the effects of this study, as important limitations were identified. Authors conducted a thorough search of the literature and used appropriate methods to screen studies for inclusion. However, it is not clear from the review if methods used to extract data were rigorous enough, and authors do not report assessing the quality of included studies. Therefore, it is not clear which evidence is subject to high risk or low risk of bias.
Wang W, Yan W, Fotis K, Prasad NM, Lansingh VC, Taylor HR, Finger RP, Facciolo D, He M. Cataract Surgical Rate and Socioeconomics: A Global Study. Invest Ophthalmol Vis Sci. 2016 Nov 1;57(14):5872-5881.