Causes of blindness

An overview of the most common causes of blindness worldwide.

Symbolic photo: An overview of the most common causes of blindness. Credit: Ulrich Eigner


is the world’s most common cause of blindness, and is responsible for the loss of vision of 20 million people. This clouding of the lens may occur due to age, injury or be congenital. Cataracts can be treated by replacing the cloudy lens with an artificial one in a 15-minute operation.


is the second most common cause of blindness. Glaucoma can be treated with medication and alleviated by a small operation, but is not curable.

River blindness (onchocerciasis)

is a parasitic disease which causes inflammation and bleeding that leads ultimately to blindness and other disabling effects. River blindness is on the retreat worldwide thanks to the widespread distribution of the drug Mectizan.


is the most widespread infectious cause of blindness, responsible for the visual impairment of about 2.2 million people, of whom 1.2 million are irreversibly blind. It causes the inside of the eyelid to scar, turn inward and scratch the cornea, eventually leading to irreversible blindness. In its earlier stages, trachoma is treated with antibiotics and is preventable through improved hygiene and sanitation. In its final stage surgery on the eyelid is the only way to prevent the loss of sight.

Uncorrected refractive errors (URE)

About 153 million people are visually impaired, due to causes such as uncorrected refractive errors. In most cases, vision can be restored with spectacles or other vision aids. 

Childhood blindness

About 1.4 million children are blind and 12 million visually impaired due to causes like uncorrected refractive errors, Vitamin A deficiency, cataract or injury.