Refractive errors

A refractive error is a very common eye disorder. It occurs when the eye cannot clearly focus the images from the outside world. The result of refractive errors is blurred vision, which is sometimes so severe that it causes visual impairment.

The three most common refractive errors are:

  1. myopia (nearsightedness): difficulty in seeing distant objects clearly;
  2. hyperopia (farsightedness): difficulty in seeing close objects clearly;
  3. astigmatism: distorted vision resulting from an irregularly curved cornea, the clear covering of the eyeball.

A fourth condition is presbyopia, which leads to difficulty in reading or seeing at arm’s length. It differs from the other disorders in that it is linked to ageing and occurs almost universally.

Refractive errors cannot be prevented, but they can be diagnosed by an eye examination and treated with corrective glasses, contact lenses or refractive surgery. WHO estimates that 153 million people worldwide live with visual impairment due to uncorrected refractive errors. This figure does not include the people living with uncorrected presbyopia, which is likely to be quite significant, according to some early evidence.

WHO, its Member States and partners are working to find ways to provide local, affordable corrective optical services to people in need, especially in poor areas with limited eye care services.

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