Nearly 108 million people in the world - one out of every 90 of the world population -- are suffering from correctable vision impairment, a global study has estimated.
Uncorrected refractive error (URE) - nearsightedness, farsightedness, and other focusing problems correctable by prescription lenses - is responsible for moderate to severe vision impairment in 101 million people and blindness in seven million people worldwide, the study said.
The findings appeared in Optometry and Vision Science, official journal of the American Academy of Optometry.
"Uncorrected refractive error continues as the leading cause of vision impairment and the second leading cause of blindness worldwide," said one of the study authors Kovin Naidoo from Brien Holden Vision Institute, Durban, South Africa.
Refractive error refers to any of the common vision problems causing decreased sharpness of vision, including myopia (nearsightedness), hyperopia, (farsightedness), or astigmatism.
In developed countries, eyeglasses or contact lenses are routinely prescribed to correct these causes of impaired vision.
But millions of people around the world still have impaired vision or even blindness caused by URE.
In the study, a group of leading optometrists and ophthalmologists specialising in world blindness analysed the best available research on URE.
Pooled data from nearly 250 studies performed between 1990 and 2010 were analysed to estimate the number of people affected by blindness and visual impairment due to URE, including trends in prevalence and differences by region.
Uncorrected refractive error was found to be the leading cause of moderate to severe visual impairment, affecting an estimated 101.2 million people.
It was also the second leading cause of blindness (after cataracts), affecting another 6.8 million.
"In 2010, URE contributed 20.9 percent of all blindness and 52.9 percent of all moderate to severe vision impairment," Naidoo said.