Blindness and visual impairment
Blindness and visual impairment
Key Facts
Globally, it is estimated that approximately 1.3 billion people live with some form of visual impairment.
Worldwide, the leading causes of visual impairment are uncorrected refractive errors and cataracts.
The majority of people with visual impairment are over 50 years of age.
Definitions
The Eleventh International Classification of Diseases (ICD-11, 2018) distinguishes two groups of visual impairment: those affecting distance vision, as corrected, and those affecting near vision, as corrected.
Impairments affecting distance vision:
Mild - corrected visual acuity less than 6/12;
moderate - corrected visual acuity less than 6/18;
Severe - corrected visual acuity less than 6/60;
Blindness - corrected visual acuity less than 3/60.
Impairments affecting near vision :
visual acuity less than N6 or N8 at 40 cm with existing correction.
Individual experience of visual impairment varies depending on many different factors, for example: the availability of prevention and treatment interventions, access to vision rehabilitation (including assistive products such as glasses and white canes), problems that may be encountered due to inaccessible buildings, transportation and information.
Estimates
Worldwide, it is estimated that approximately 1.3 billion people live with some form of near or far vision impairment.
In far vision, 188.5 million people have mild visual impairment and 217 million have moderate to severe visual impairment, while 36 million people are blind (1). In addition, 826 million people live with a disability affecting near vision (2).
Population growth and aging will increase the risk that more people will develop visual impairment.
Causes
Globally, the main causes of visual impairment are :
uncorrected refractive errors;
Cataracts;
age-related macular degeneration;
glaucoma;
Diabetic retinopathy;
corneal opacification;
trachoma.
The main causes of blindness are:
a non-operated cataract: 35%;
uncorrected refractive errors: 21%;
glaucoma: 8%.
The causes vary from country to country. For example, the proportion of visual impairment due to cataract is higher in low- and middle-income countries than in high-income countries. In high-income countries, diseases such as diabetic retinopathy, glaucoma, and age-related macular degeneration are more common.
In children, the causes of visual impairment vary considerably from country to country. For example, in low-income countries, congenital cataract is one of the main causes, while in high-income countries, retinopathy of prematurity is more often involved.
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