VISION LOSS

The age-standardised prevalence of blindness and visual impairment has decreased around the world over the past 20 years, although the total burden of vision loss changed little due to population growth, according to the Global Burdens of Disease, Injuries and Risk Factors Study (GBD Study).

Findings from the study showed the global age-standardised prevalence of blindness decreased from 0.9 per cent in 1990 to 0.5 per cent in 2010,which represented an estimated 34 million blind (defined as VA <3/60 in the better eye). In addition, the GBD Study estimated there were 200 million visually impaired (VA <6/18 to 3/60 in the better eye) people in the world in 2010, reported Rupert Bourne MD, who presented the data at the 2012 annual meeting of the Association for Research in Vision and Ophthalmology, on behalf of the 79 members of the GBD Vision Loss Expert Group.

“The long, comprehensive span of data sources used in this project gives strength to the temporal observation of a decrease in global age-standardised blindness prevalence. Despite the variability in availability of population-based data across regions, the findings from the GBD Study highlight geographic differences in the burden of blindness and vision loss, and they should be a useful source for policymakers worldwide,†said Dr Bourne, professor of ophthalmology, Vision & Eye Research Unit of Anglia Ruskin University, Cambridge, UK.

The GBD Study was commissioned with funding from the Bill & Melinda Gates Foundation in 2007. Estimation of global trends in visual impairment and blindness prevalence between 1990 and 2010, along with its uncertainties by sex, for 190 countries and territories in the 21 GBD sub-regions, was performed by accessing published and unpublished data from population-based studies of visual impairment and blindness for the period 1980 to 2012. A total of 14,908 abstracts were identified, 1,334 articles reviewed, and the information was supplemented by additional data obtained from contacting the principal investigators for some studies.

In total, 6,500 data points were extracted into the database from 259 sources. Dr Bourne noted the literature search identified relatively few studies from the 1980s, and while the number of publications increased during the 1990s, especially from Asian countries, there were still no data from six GDP regions. Analyses of the data by region showed marked reductions in age-standardised prevalence of blindness in North Africa, the Middle East, Asia, the Indian subcontinent, and sub-Saharan Africa as compared with a less marked reduction in high income and eastern and central European countries, where, among these regions, the prevalence was lowest.

Worldwide, there were 1.4 times more blind women than men, and the gender difference was even more marked in certain regions, particularly in Eastern Europe. “This discrepancy is mainly due to the reduced life expectancy for men in this region,†Dr Bourne said. Additional work is ongoing. The Visualisations Project will make the wealth of data from the GBD Study accessible to many users.

One of Dr Bourne’s PhD students, Mr John Somner, prepared an early version of such a visualisation, which was demonstrated at the meeting. In addition, cause-specific analyses of low vision and blindness are under way, future projections accounting for population growth are being done and disability weights associated with the burden of vision loss, calculated as disability-adjusted life years, will be released soon.