Uncorrected refractive errors are the leading cause of visual impairment worldwide, according to new statistics released this week by the World Health Organization.
More than 153 million people cannot see properly simply because of a lack spectacles or contact lenses.
Marking yesterday's World Sight Day, WHO released the figures this week to highlight how millions of children are missing educational opportunities and adults are excluded from productive working lives, with severe economic and social consequences.
The health body previously estimated that 161 million people were visually impaired from conditions such as cataract, glaucoma and AMD. Uncorrected ametropia has not been included in these earlier estimates.
These latest statistics add to the previous number and effectively double the estimated total number of visually impaired people, bringing it to some 314 million people globally. At least 13 million children and 45 million working-age adults are affected.
'These results reveal the enormity of the problem,' said Dr Catherine Le Galès-Camus, WHO assistant director-general for non-communicable diseases and mental health.
'This common form of visual impairment can no longer be ignored as a target for urgent action.
'Correction of refractive errors is a simple and cost-effective intervention in eye care,' said Dr Serge Resnikoff, coordinator of WHO's chronic disease prevention and management unit.
'Now that we know the extent of the problem of uncorrected refractive errors, especially in low and middle income countries, we must redouble our efforts to ensure that every person who needs help is able to receive it.'