A new study has revealed that the proportion of vision impairment and blindness worldwide that is caused by cataract and macular degeneration varies geographically. The findings are published in The Lancet Global Health.
The team of researchers, led by Rupert Bourne of the Vision and Eye Research Unit at Anglia Ruskin University, say their study is the largest ever analysis of worldwide vision impairment and blindness.
To reach their findings, they analyzed geographical trends of the disabling conditions between 1990 and 2010, alongside their main causes.
The investigators used published and unpublished data to reach their findings, and say they defined blindness as "visual acuity in the better eye less than 3/60" and moderate and severe vision impairment (MSVI) as "visual acuity in the better eye less than 6/18 but at least 3/60."
The investigators looked specifically at cataract, glaucoma, macular degeneration, diabetic retinopathy, trachoma and uncorrected refractive error, and estimated how these conditions contributed to visual impairments in proportion to age, geographical region and year.
Significant geographic differences discovered
Results of the analysis revealed that the overall number of people who suffered blindness as a result of cataract reduced from 12.3 million in 1990 to 10.8 million in 2010.
MSVI as a result of cataract decreased from 44 million in 1990 to 35.2 million in 2010.
The largest analysis of vision impairment and blindness worldwide has revealed that the proportion of cataract and macular degeneration as a cause of these disabilities vary geographically.
Cataract or uncorrected refractive error, both of which are treatable conditions, caused 54% of blindness cases in 2010 and 71% of MSVI cases.
When looking at data from 1990, the researchers found that of the 31.8 million people who were blind, 68% have treatable or preventable causes. This had reduced to 65% of the 32.4 million who were blind in 2010.
When looking at prevalence and cause geographically, high-income regions posed cataract as the lowest cause of blindness, but macular degeneration was the highest cause in these areas.
Less than 15% of people from high-income regions suffered from blindness in 2010 as a result of cataract, but more than 40% of people were blinded by the condition in South and Southeast Asia, and Oceania.
Macular degeneration as the cause of blindness was highest in regions with older, higher-income populations, such as North America and Europe. These areas saw more than 15% of blindness caused by macular degeneration, compared with only 2.6% in South Asia.
The researchers note that in all regions, women had a higher proportion of blindness and MSVI caused by macular degeneration and cataract than men.
Commenting on the findings, Prof. Bourne says:
"Being able to study in detail the changes in cause-specific prevalence of blindness and vision impairment is important for the setting of priorities, development of policies, and for planning.
Additionally, our data will be a useful tool to help mobilize eye-care services from governments, donors and civil society."
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