Individuals from countries with less socioeconomic development relative to the global average may have more long-term ultraviolet radiation (UVR) exposure and, subsequently, a greater burden of cataract-related blindness, new research published in Biomedical and Environmental Sciences suggests.

“Cataracts are the most unevenly distributed noncommunicable eye disease in the world, placing the greatest burden on middle- and low-income countries, which result from the combined effects of socioeconomic and environmental factors,” the authors noted in their paper.

The investigative team from China analyzed the findings of the 2017 Global Burden of Disease Study to cull national and subnational age-standardized “year lived with disability” rates associated with cataract-related blindness. They also used information from the human development index (HDI), part of the United Nations Human Development Report, as a measure of socioeconomic status. The HDI is a composite measure of health, education and income, measured by life expectancy at birth, mean years of schooling and gross national income per capita. A higher HDI value indicates a higher level of socioeconomic development.

Finally, the investigators considered the estimated ground-level UVR exposure based on NASA’s Ozone Monitoring Instrument database.

Across 185 countries, the researchers found socioeconomic status was inversely associated with the burden of cataract blindness. Countries with a very high HDI had an 84% lower age-standardized year lived with disability rate compared with countries with a low HDI. In high-HDI countries, the rate was 76% compared with 48% in medium-HDI countries.

The investigators also observed a trend between UVR exposure and the association between socioeconomic status and cataract blindness burden. When subnational regions were considered, the negative correlation between socioeconomic status and cataract blindness burden was largely retained but lower in magnitude.

“The findings highlight that in addition to existing efforts toward eliminating cataract blindness, UVR exposure protection interventions, such as wearing glasses, wearing a cap and a reduction of outdoor activity time, must be reinforced in developing regions with high UVR exposure to achieve the global target proposed by the World Health Organization’s Global Action Plan,” the researchers wrote.

Once cataract has developed, individuals in low income countries also face hurdles to treatment. “In developing countries worldwide, over half of people with cataract blindness do not undergo cataract surgery, mainly because of a low willingness to pay for it,” the report points out.