(Reuters Health) - Low levels of socioeconomic development are closely linked with a high burden of vision impairment, a recent study involving 190 countries and territories suggests.
An estimated 253 million people live with vision impairment globally, including 36 million who are blind, according to the World Health Organization (WHO). These numbers could triple as populations grow and age, WHO says, even though up to 80% of all vision impairment is preventable or curable.
“This study confirms what we have long known. Poor patients in most countries suffer far more visual disability than people in wealthier countries, because those in wealthier countries can better afford the eye care they need,” said Alfred Sommer, clinical spokesperson for the American Academy of Ophthalmology and professor at the Johns Hopkins Bloomberg School of Public Health, who was not involved in the study.
The study, published in JAMA Ophthalmology, collected data on moderate-to-severe visual impairment and blindness from 2010 and analyzed it against countries’ socioeconomic indices, including Gross Domestic Product (GDP) and the Human Development Index (HDI), as well as health expenditure indicators.
A country with higher GDP or HDI – an index that incorporates education levels, life expectancy and gross national income per capita - would be expected to have a bigger eye care budget and infrastructure to reduce the prevalence of vision impairment, said study researcher Mingguang He by email. He is Professor of Ophthalmic Epidemiology in the University of Melbourne and Centre for Eye Research Australia and Director of WHO Collaborating Center for Prevention of Blindness (Australia).
But while higher healthcare spending was indeed correlated with a lower prevalence of blindness, the proportion of the population with blindness was higher in countries with higher “out of pocket” healthcare expenses – that is, higher amounts that individuals had to pay by themselves, said Omar Mahroo, an honorary senior clinical Lecturer in Ophthalmology at King’s College London who was not involved in the study.
The researchers also found that where education levels were higher, vision loss was less common.
Overall, about 89% of those that suffer from vision loss reside in low and middle-income countries, according to the International Agency for the Prevention of Blindness.
Reducing the prevalence of vision loss has been shown to increase productivity, income and provide other economic benefits. According to the UK-based non-profit Age Related Macular Degeneration (AMD) Alliance International, the cost of vision loss in 2010 totaled $3 trillion globally.
“For each $1 spent on eye care one would expect return to the economy of more than twice this amount. This makes an even stronger case to give priority to eye care in a developing country setting,” said Hugh R. Taylor, Board President of the International Council of Ophthalmology, who was not involved in the study.
The researchers acknowledge that socioeconomic indexes may not accurately represent all populations within a country, as levels of development may vary across regions.
And while the study found a link between a country’s HDI and visual impairment prevalence, it doesn’t prove a causal association, said Mauricio Avendano Pabon, a professor of public policy and global health at King’s College London.
“For example,” said Pabon, who wasn’t involved in the study, “the relationship may not be due to socioeconomic development but to other factors correlated with it, such as quality of care, exposure to pollution, etc.”
JAMA Ophthalmol 2017.