According
to World Health Organization’s Fact Sheet –
Globally, at
least 2.2 billion people have a vision impairment or blindness, of whom at
least 1 billion have a vision impairment that could have been prevented or has
yet to be addressed.
This 1
billion people include those with moderate or severe distance vision impairment
or blindness due to unaddressed refractive error, as well as near vision
impairment caused by unaddressed presbyopia.
Globally,
the leading causes of vision impairment are uncorrected refractive errors and
cataracts.
The majority
of people with vision impairment are over the age of 50 years.
Vision
impairment Definitions
The
International Classification of Diseases 11 (2018) classifies vision impairment
into two groups, distance and near presenting vision impairment.
Distance
vision impairment:
Mild –
presenting visual acuity worse than 6/12
Moderate –
presenting visual acuity worse than 6/18
Severe –
presenting visual acuity worse than 6/60
Blindness –
presenting visual acuity worse than 3/60
Near vision
impairment:
Presenting
near visual acuity worse than N6 or M.08 with existing correction.
A person’s
experience of vision impairment varies depending upon many different factors.
This includes for example, the availability of prevention and treatment
interventions, access to vision rehabilitation (including assistive products
such as glasses or white canes), and whether the person experiences problems
with inaccessible buildings, transport and information.
Causes of
vision impairment
Globally,
the leading causes of vision impairment are:
uncorrected
refractive errors
cataract
age-related
macular degeneration
glaucoma
diabetic
retinopathy
corneal
opacity
trachoma.
There is
some variation in the causes across countries. For example, the proportion of
vision impairment attributable to cataract is higher in low- and middle-income
countries than high-income countries. In high income countries, diseases such
as diabetic retinopathy, glaucoma and age-related macular degeneration are more
common.
Among
children, the causes of vision impairment vary considerably across countries.
For example, in low-income countries congenital cataract is a leading cause,
whereas in high income countries it is more likely to be retinopathy of
prematurity.
Strategies
to address vision impairment
Effective interventions are available for health promotion, prevention, treatment and rehabilitation to address the entire range of needs associated with eye conditions and vision impairment across the life course. Some are among the most feasible and cost-effective to implement. For example, uncorrected refractive error can be corrected with glasses while cataract surgery can restore vision. Vision rehabilitation is also effective in improving functioning for people with an irreversible vision impairment.
(Source: WHO Fact Sheet)
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