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Cataract -- A Major Blinding Condition
Of the four diseases of greatest concern to the World Health
Organization (WHO) Program for the Prevention of
Blindness--trachoma,
onchocerciasis, xerophthalmia, and cataract--cataract alone is the
leading cause of blindness in all countries of the world. Cataract
is
the leading blinding condition in the 116 countries covered by the
Blindness Data Bank* in the WHO Program for the Prevention of
Blindness. An estimated 42 million people are affected by severe
loss
of vision, and cataract causes 17 million of these losses.
Cataract
was indicated as the prime cause of blindness in 43.6% of country
reports and accounts for 30%-50% of blindness in approximately half
the reports in which relative blindness prevalence is indicated.
It
is especially prevalent in developing countries of the tropical
belt.
Developing countries indicate cataract as the major cause of
severe visual impairment. Cataract frequency differs greatly in
different geographic areas. A population-based prevalence survey
for
blindness (defined as visual acuity less than 3/60), carried out
with
WHO assistance in various African areas not endemic for trachoma or
onchocerciasis, revealed a blindness rate of approximately 1%, with
cataract accounting for 40%-50% of visual loss. However, analysis
of
data from a blindness survey of Australian aborigenes indicates an
increased cataract rate in cases of severe trachoma scarring.
Senile cataract appears to have earlier onset in certain areas
in
Africa than in other parts of the world, with incidence becoming
significant in the 40-50-year age group. A recent report from Asia
indicated that, in a certain population group in Nepal, cataract
apparently starts at about 35 years of age. In one region of
India,
with a total cataract prevalence of 4.3% for all ages, a prevalence
rate of 1% was revealed for the 30-49-year age group and increased
markedly to 67% for ages 70 and older.
*WHO. Weekly Epidemiological Record 1982;57:145-6.
A WHO-assisted survey of blinding conditions, carried out in
several areas of Africa and Asia, detected cataract blindness in
0.3%-4% of the population. Age-specific prevalence of blindness
due
to cataract rose steadily, starting at 45 years of age. In a survey
in
North Africa, cataract contributed to blindness in 0.3% of the
total
population, in 2% of those aged 41-60 years, and in 11.6% of those
aged over 60. Cataract is expected to become even more prevalent
with
the general increase in life expectancy. In developing countries,
the
estimated 13 million persons who are blind due to cataract may
reach
30 million by the year 2000 unless efficient, full-scale treatment
programs reach all rural areas.
The present WHO strategy to combat blindness from cataract is
based on simple ocular surgery, which, in certain peripheral areas,
is
not adequate to keep up with new cases or with the backlog of
cases.
Because of the rapidly increasing impact of cataract, research on
possible prophylactic measures is gaining attention.
Reported by WHO. Weekly Epidemiological Record 1982;57:397-8.
Disclaimer
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