The number of blind people across the world is set to triple within the next four decades, researchers led by Professor Rupert R A Bourne, at the Vision & Eye Research Unit, Anglia Ruskin University, Cambridge, UK, suggest.
They predict cases will rise from 36m to 115m by 2050, if treatment is not improved by better funding. A growing ageing population is behind the rising numbers. Some of the highest rates of blindness and vision impairment are in South Asia and sub-Saharan Africa.
The percentage of the world's population with visual impairments is actually falling, according to the study. But because the global population is growing and more people are living well into old age, researchers predict the number of people with sight problems will soar in the coming decades.
Analysis of data from 188 countries suggests there are more than 200m people with moderate to severe vision impairment. That figure is expected to rise to more than 550m by 2050.
"Even mild visual impairment can significantly impact a person's life," said lead author Bourne. "For example, reducing their independence… as it often means people are barred from driving." He said it also limited people's educational and economic opportunities.
The worst affected areas for visual impairment are in South and East Asia. Parts of sub-Saharan Africa also have particularly high rates.
The study calls for better investment in treatments, such as cataract surgery, and ensuring people have access to appropriate vision-correcting glasses. Bourne said: "Interventions provide some of the largest returns on investment. They are some of the most easily implemented interventions in developing regions." "They are cheap, require little infrastructure and countries recover their costs as people enter back into the workforce," he said.
The charity Sightsavers, which works in more than thirty countries to try to eliminate avoidable blindness, says it is seeing a rise in conditions such as cataracts, where the eye's lens clouds over.
"Due to an ageing population and a rise in chronic disease, we expect the burden of blindness to only grow within the world's poorest countries" said Imran Khan from the charity. He said health systems in developing countries need to be improved, and more surgeons and nurses need to be trained to deliver sustainable eye health care.
Summary
Background: Global and regional prevalence estimates for blindness and vision impairment are important for the development of public health policies. We aimed to provide global estimates, trends, and projections of global blindness and vision impairment.
Methods: We did a systematic review and meta-analysis of population-based datasets relevant to global vision impairment and blindness that were published between 1980 and 2015. We fitted hierarchical models to estimate the prevalence (by age, country, and sex), in 2015, of mild visual impairment (presenting visual acuity worse than 6/12 to 6/18 inclusive), moderate to severe visual impairment (presenting visual acuity worse than 6/18 to 3/60 inclusive), blindness (presenting visual acuity worse than 3/60), and functional presbyopia (defined as presenting near vision worse than N6 or N8 at 40 cm when best-corrected distance visual acuity was better than 6/12).
Findings: Globally, of the 7·33 billion people alive in 2015, an estimated 36·0 million (80% uncertainty interval [UI] 12·9–65·4) were blind (crude prevalence 0·48%; 80% UI 0·17–0·87; 56% female), 216·6 million (80% UI 98·5–359·1) people had moderate to severe visual impairment (2·95%, 80% UI 1·34–4·89; 55% female), and 188·5 million (80% UI 64·5–350·2) had mild visual impairment (2·57%, 80% UI 0·88–4·77; 54% female). Functional presbyopia affected an estimated 1094·7 million (80% UI 581·1–1686·5) people aged 35 years and older, with 666·7 million (80% UI 364·9–997·6) being aged 50 years or older. The estimated number of blind people increased by 17·6%, from 30·6 million (80% UI 9·9–57·3) in 1990 to 36·0 million (80% UI 12·9–65·4) in 2015. This change was attributable to three factors, namely an increase because of population growth (38·4%), population ageing after accounting for population growth (34·6%), and reduction in age-specific prevalence (−36·7%). The number of people with moderate and severe visual impairment also increased, from 159·9 million (80% UI 68·3–270·0) in 1990 to 216·6 million (80% UI 98·5–359·1) in 2015.
Interpretation: There is an ongoing reduction in the age-standardised prevalence of blindness and visual impairment, yet the growth and ageing of the world's population is causing a substantial increase in number of people affected. These observations, plus a very large contribution from uncorrected presbyopia, highlight the need to scale up vision impairment alleviation efforts at all levels.
Authors
Rupert R A Bourne, Seth R Flaxman, Tasanee Braithwaite, Maria V Cicinelli, Aditi Das, Jost B Jonas, Jill Keeffe, John H Kempen, Janet Leasher, Hans Limburg, Kovin Naidoo, Konrad Pesudovs, Serge Resnikoff, Alex Silvester, Gretchen A Stevens, Nina Tahhan, Tien Y Wong, Hugh R Taylor
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[link url="http://www.thelancet.com/journals/langlo/article/PIIS2214-109X(17)30293-0/fulltext?elsca1=tlpr"]The Lancet Global Health article summary[/link]