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Childhood Blindness Worldwide
||I K Jalili
Childhood blindness in Western and Northern Europe
Latin America and the Caribbean (LAC)
disabilities in blindness
This chapter reviews the literature
on childhood blindness in the various world regions according to
World Bank Classification of Countries.
CHILDHOOD BLINDNESS IN EUROPE
Europe differs in many aspects, such as political,
socioeconomic, and geographical, and there is a noticeable demarcation
between countries in the Established Market Economy and
Socialist Economies countries of Eastern Europe. After
substantial political changes at the beginning of the 1990s, the
majority of central and eastern European countries started to rebuild
their healthcare systems. It is apparent that Eastern Europe represents a
highly diverse region where the difference among countries broadens year
Changing Patterns in Europe
Data on new registrations in 1968 had shown
no substantial decline in blind registrations despite the end of
registrations for those with retinopathy of prematurity (ROP). Much of the
changes and increase in those registered were due to administrative
changes and changes in the age structure of the population.
Fraser and Friedman in 1967
undertook a study of 776 children on the blind register in the UK, almost
one quarter of the total number of children registered with severe visual
These were from a variety of special schools that included blind children
with additional handicaps. This study went further than previous ones in
that all those included underwent ophthalmic and systemic examination and
investigations, in addition to detailed histories being obtained from the
families. The study revealed that the three commonest causes of blindness,
accounting for more than 50% of all cases, were retinopathy of
prematurity, retinal degenerations (retinitis pigmentosa, Leber
congenital amaurosis, and related conditions), and
congenital cataract. About 42% of the disorders were genetically
determined with 20% of all cases being autosomal dominant, 17% autosomal
recessive and 5% X-linked; 8% were thought to be multifactorial.
In mainland Europe, many differences in
childhood blindness were demonstrated. In the Previous Socialist Economies there was a prevalence of between
0.01/1000 and 0.04/1000 with the main anatomical causes being retinal
disorders and optic atrophy. This is in contrast to the highly
industrialised countries of Europe where the leading causes of childhood
serious visual loss are CNS lesions, congenital anomalies and retinal
disorders. This is a trend similar to that reported in England and
Scotland. In the middle-income countries of Europe, congenital cataract,
glaucoma and, mainly, retinopathy of prematurity are highly expressed.(4)
The prevalence of childhood blindness in the UK was assessed
by Stewart-Brown and Haslum in 1980, in a nationally representative sample
of 15,000 10-year old children. The prevalence of blindness was between
3.4 - 4.0/10,000, and partial sightedness (SVI) between 5.4 and 8.7/
Causes and Aetiologies
Genetically determined disorders
accounted for 51% of 386 subjects studied in Northern Ireland, by Bryars
and Archer in 1977 which was considered to be in excess of any
other survey at the time, (6)
with the exception of those undertaken in
These were followed in importance by pre- and perinatal complications such
as pre-eclampsic toxaemia, dysmaturity, prematurity etc. These findings
demonstrated significant differences from those reported 10 years earlier
in a study of children from selected schools by Fraser and Friedman.(3)
The rate of cataract in the
Northern Ireland study had risen from 15% to 32% and retinopathy of
prematurity had diminished
from 20% to 12%. The former was also the most common cause of blindness
or partial sight in 1980 in the UK followed by congenital glaucoma.
Similarly, but to a lesser degree, a study
by Phillips in 1987 of 99 children at the Edinburgh Royal Blind School,(9)
in a comparison to a study done in Japan by Tsukahara,(10)
confirmed hereditary causes as responsible
for between 48-58 of the 99 pupils. The major causes of blindness were
optic atrophy (15 cases), congenital cataract (12 cases), Leber congenital
amaurosis ‘retinal aplasia’ (12 cases),
often with other handicaps, and retinopathy of prematurity (11 cases).(9)
Fifteen years later, another study
at the same blind school in 2002 by Alagaratnam demonstrated a new trend
in childhood blindness,(11)
away from hereditary causes
and towards perinatal causes (40%), with prematurity forming the largest
single group, followed by hereditary factors (26%); most commonly these
were optic atrophy or retinal dystrophy. The majority of the latter were
thought to be autosomal recessive in origin. Disease or malformation of the CNS or optic
nerve was the commonest cause of visual impairment and was present in 50%
of the total examined. It is also interesting to note that although
retinopathy of prematurity
accounted for 18%, the youngest child with retinopathy of prematurity was 9 years old,
highlighting a decreasing incidence. A similar trend was demonstrated by
Schwarz et al in the City of Bradford, England in the same year.(12)
Bamashmus et al confirmed that congenital glaucoma, congenital cataract and corneal
infections were no longer causes of registration in children; instead
registration caused by brain damage has become a major contributor.(13)
A UK study of particular interest is
that of Rahi and Cable of 439 children, newly diagnosed during the year
2000, with severe visual impairment and blindness. The study identified
eligible children through both the British Ophthalmological and British
Paediatric Surveillance Units.(14)
It was pointed out that
notification by ophthalmologists and paediatricians had not been
totally independent. A child was less likely to be reported by one
specialist if another was involved in the joint care. However, a
simulated analysis of all children being treated by both specialists
suggested that 99% of eligible cases had been ascertained. The study
included only children with permanent SVI/BL at one year of follow-up,
it excluded those whose vision was better after treatment or
spontaneously. The author found that SVI/BL occurred more commonly in
the context of complex non-ophthalmic impairments and had greater
associated mortality than previously assumed. The study found 336 (76.5%)
with additional non-ophthalmic disorders, and 10% of all children studied
(439) died from the additional disorder within one year of the diagnosis
of blindness. Similar mortality rates were reported in Swedish children
(13%) the majority of whom died from respiratory causes.(15)
Rahi et al
concluded that children of low
birth weight, and from ethnic minorities, had the highest rates of SVI/BL,
with those from the most deprived socio-economic groups being
over-represented. Three-quarters of those studied had disorders that were
neither preventable nor treatable; the major anatomical site affected
being the cerebral/visual pathways (77%). These were more frequent in
those with SVI/BL plus, than in those with isolated SVI/BL. Conversely,
retinal disorders, (particularly retinal dystrophies and albinism) and
glaucoma were more important in those with isolated visual loss than in
those with SVI/BL plus. Hereditary disorders were found to affect 46%
(n=32) of south Asian children (Indian, Pakistani or Bangladeshi) compared
with 29% (n=86) of white, 33% (n=6) of black, and 33% (n=9) of other
ethnic groups. It was also found that the prevalence of blindness in this
study was greater than anticipated from published yearly rates of
notification to the British registers of blindness over the previous two
decades. The trends reflected the changing picture of chronic disease and
disability in childhood more broadly, in particular the associations with
low birth weight, ethnic origin and socio-economic deprivation. The author
concluded that the scope for intervention against blindness in children
in the UK, and other industrialised countries, was very limited.
A survey in the Republic of Ireland of 172
children (93 males and 79 females) between 1989 and1990, showed that 56%
of the causes were congenital. Of these, 40% were due to prenatal factors
and 16% genetic. The commonest perinatal conditions were birth asphyxia in
11% of cases and retinopathy of prematurity in 11% of cases. (16)
Aetiological factors are shown in Table 22.6.
North European/ Scandinavian
Significant differences in the prevalence
of blindness were reported in Denmark, Iceland, Finland, Norway and
Southern Sweden in 1993 despite identical classification criteria. The
reported number was 2527 visually impaired children from the total <17
years child population of 3,818,000 which formed 22% of the total
population of these countries. The prevalence rate in these countries
varied from 0.15/1000 to 0.41/1000 (blindness) and 0.48/ 1000
to 1.05/1000 (visual impairment). This variation was attributed mainly to
under registration in the countries with the lowest rates. Visual
impairment had been reported before the age of 3 years in 50% of cases.
Prenatal factors, including genetic
conditions, accounted for 66% of the cases in the Nordic Countries but in
children without additional impairment the percentage was 74%. Genetic
factors accounted for a little over half of prenatal cases and in 40% of
cases of prenatal aetiology the causes were unknown. Compared with a
previous prevalence study in 1992, the relative impact of retinopathy of
prematurity had dropped
from the third most frequent cause (10%) in the prevalence study, to
seventh (4%) in the incidence study.
The predominant causes in the Nordic
countries were congenital malformations, neuro-ophthalmic disorders and
retinal conditions. Optic atrophy was the single most common cause.
retinopathy of prematurity
was the principle cause for severe visual impairment. Congenital cataract
was also an important cause. Visual impairment due to brain damage, which
was referred to as cerebral amblyopia, accounted for 23% of cases
affected, with different proportions in the five countries, with a range
between 36% in Sweden to only 10% in Finland. The authors noted a trend
towards an increase in multiply impaired children from 30-50% in the
earlier study, to 61% in this study.
Other studies in Sweden, comparing the
current trend in childhood blindness to that in 1980, also reached the same conclusions of
the presence of a shift from prenatal to perinatal causation noted above.
Data from Greenland compares to the
findings in the Nordic counties.
Only 38 cases of congenital visual
impairment were reported in the Inuit population of Greenland over a
period of 40 years (1950-1989) representing an incidence of 0.86/1000
live born children. The two most common causes of blindness were optic
atrophy and cerebral visual impairment due to brain disorders of various
aetiologies. retinopathy of prematurity and congenital cataract were rare causes. Fifteen out of
the 38 cases were of unknown aetiology. Genetic disorders accounted for
18.4% of cases, significantly lower than the 66% found in the Nordic
There were 25 cases of
genetic visual impairment. The causation of the isolated cases of aniridia,
lens ectopia, and Down syndrome, was attributed to new mutations, while
inbreeding was a possible contributory factor in a few autosomal recessive conditions.(27)
The figures date back to 1980 when Van Der
Pol reported in a study of 1334 pupils in 11 Dutch institutions for
visually handicapped children that the pattern of blindness had not
changed in ten years, and that congenital cataracts, retinal degenerations
and disorders of the optic nerve were still the three most common causes
of childhood blindness in the country.(28)
The proportion of blind children in
Germany, which applies to the rest of the industrialised countries, from
the total blind population, has dropped significantly in the past 100
years from 12% in the 19th Century to about 5% at the present
time. Until 1901 it ranged between 9.6% - 26% in the various studies in
Germany, came down to 8.8% in 1926 and 0.1-12.6% in 1952, reaching a
constant rate from 1973 onwards. Currently it averages 3.9%.
The causes also varied as expected. (29)
Schmidt et al (30)
highlighted the changes in the course of childhood blindness including the significant
reduction in the number of blind children since the 1960s and especially
since the 1970s. Corneal causes secondary to infections, which formed 25%
of childhood blindness until 1940, had dropped to 2%. There was also an obvious reduction
in blindness due to uveitis from infections and chorioretinitis, and the
total eradication of blindness from trauma, with no case of sympathetic ophthalmia since 1950. The incidence of congenital cataract and
congenital glaucoma remained unchanged, although they were rarely
associated with blindness as a result of improvement in the management of
The incidence of blindness caused by
retinal detachment and retinoblastoma remained unchanged, though rare. The
commonest causes of morbidity were optic atrophy (20%) and retinal
degenerations (16%-19%) whose incidence has remained constant and high. On
the other hand, a major increase was noted in ocular malformations and
developmental anomalies including retinopathy of prematurity. The latter was responsible for 38%
of childhood blindness.
In a more recent study in southern Germany
(1996), Haassler et al reported the aetiologies of visual impairment and
mental retardation in 239 multi-handicapped blind and partially sighted
children born between 1981 and 1987.(31)
heterogeneity was found. The commonest causes were due to perinatal
factors and late gestation (41%). Amongst these, lesions in the visual
pathways in preterm children were very frequent and were explained by periventricular keratomalacia
in the majority of instances. The distribution of the major aetiological
groups was different from populations with isolated mental retardation and
populations of isolated visual impairment, but similar to the Swedish
population with spastic quadriplegia. The prevalence of visual impairment was
found to be low at 0.67/1000 live births.
Figures from Switzerland date back to 1987 when 262
children with blindness and visual impairment were examined; children with
severe brain damage and multiple handicaps were not included in the study.
Congenital malformations accounted for 53% of the cases, retinopathy
of prematurity for 25%,
infections for 10% and tumours for 10%. In the visually impaired group,
metabolic disorders, and accidents were additional causes.
In France, data in English is scarce. In
the mid-1990s, cataract and congenital nystagmus were the main causes of
blindness found in a study of 340 children and adolescents in two
specialised schools in northern France.(34)
Figures from countries that belong to the
PSE Group are available from four countries; namely the Czech Republic,
Slovakia, Poland and Hungary.(4),
In the Czech Republic 42% of childhood blindness is caused by
retinopathy of prematurity, and in
Poland retinopathy of prematurity contributes to 19% of cases. In the
latter, a 70% increase in the number of visually disabled children took
place in the 20 years between 1979 and 1999 with the major cause being
optic nerve atrophy (21.66%). Hereditary factors accounted for the
majority of cases in Hungary and Slovakia at 50% in the former and 90% and
48% in the latter in one blind school and hospital admissions
In Hungary there was relatively more autosomal dominant than autosomal
recessive and sex-linked conditions,
while acquired causes accounted for about 40% of the cases.
Prevalence of severe visual
handicap was 0.43 / 1000 in 1983-1984.
CHILDHOOD BLINDNESS IN NORTH AMERICA
In North America
the picture, including the changing trends, are in line with
the rest of the Established Market Economies countries. Earlier studies in 1965 in Canada by
MacDonald revealed that approximately 30% of a total number of 24,605 on
the blind register (of whom 1,865 were aged 0-8 years) had genetically
determined eye diseases, with the predominance in cataract (41% of all
cases of cataract), together with retinal lesions.(42)
The incidence of acquired
causes of visual impairment had dropped by two thirds from 6 /100,000 to 2
/100,000 between 1960 and 1989 as reported from analysing data on children
younger than 19 years of age with visual impairment equal to and less than
The quality of information began to improve in the early 1970s when
(13%), optic atrophy (12%) and nystagmus (10%) surfaced as the three most
common causations of childhood blindness in 1046 children under the age of 20 years.(44)
retinopathy of prematurity formed a small group at that time (6%).(43)
Earlier data were not sufficient to establish the aetiologies of these
conditions, whether hereditary or environmental. The predominance of
genetic causations was later established by Robinson and Jan
in a retrospective analysis of
data in 1989. These were followed by tumours, injuries, infections and
autoimmune disorders. Acquired causes formed 25% of the aetiologies, whilst
optic nerve atrophy together with retinal disorders rose to 90% of all
ocular pathology. They also demonstrated that the percentage of children
with neurological disorders had increased in the previous 30 years because
more children with profound brain damage had survived.(43)
In the highly inbred region of
Newfoundland and Labrador, single gene disorders accounted for 30% of
total blindness in children (and also adults) and congenital defects for
another 10-11% in 1986.(45)
There is a general lack of
comprehensive information available for children in the USA in the recent
There is no national Registry of the blind in the USA, and most of the
schools for the blind do not keep data regarding the cause of blindness in
Of the few early studies available on the causes of childhood blindness were those of
Delaney in 1962,(48)
Gillespie et al in 1963, (49)
Hilgartner in 1967,
and DeCarlo in 1999.52)
was based on the records of 834 pupils in Pennsylvania in 1962. He found
retinopathy of prematurity to be the largest single cause of childhood
307 (36.9%) of pupils, an expected finding for that period of time, and
he anticipated a 30% reduction in the following decade. Congenital
cataract was found to affect 99 (11.9%) of pupils followed by optic
atrophy in 79 (9%) of pupils.
studied the records of pupils
attending the Texas State School for the Blind during several periods;
1929-30, 1939-40, 1948-49 and 1966-67. Over that period of time the three
main conditions to have declined in importance were noted as sympathetic
ophthalmia, ophthalmia neonatorum, and syphilis. As with the Delaney study, the greatest
problem found in the later period of the study was retinopathy of
prematurity, with the numbers
entering the school with this diagnosis rising from 1 in 1955 to 10 in
1966. He also noted that congenital conditions had remained at more or
less the same percentage during the preceding 37 years, the causes of
which included congenital cataract, albinism, microphthalmos, congenital
dislocated lens and congenital absence of the anterior segment of the
Along with the rest of the Established
Market Economies countries, a
further change in the trend of blindness also took place in the USA, that
is a shift to optic nerve pathologies as demonstrated by De Carlo in his
retrospective study of the medical records of 123 students at the Alabama
school for the blind between 1996-1997.(52)
Optic nerve pathologies constituted 30.9% (optic atrophy 13%; Leber's
optic atrophy 4.1%; optic nerve hypoplasia 5.7%; and glaucoma 8.1%). Other
common causes included congenital malformations (other than aniridia)
12.2%; cataracts/aphakia 13.8%; albinism 13.0%; and retinitis pigmentosa
8.1%. Nystagmus, chorioretinitis, and other conditions accounted for the
remaining 22% of diagnoses. Visual acuities ranged from 6/6 to NLP, with
44.3% having acuity better than 6/60; 26.2% having 6/60 to <3/60; 13.1%
having measurable acuity of 3/60 or worse; 9% having LP; and 7.4% having
revealed that in 1990, data on legal blindness in the USA indicated that
approximately 2,600 children under 5 years of age and approximately
51,000 between the ages of 5-19 were legally blind. Among the children
under 5 years, prenatal cataract was the leading cause of legal blindness,
accounting for 16% of all cases. This was followed by optic atrophy (12% of all
cases) and retinopathy of prematurely (9% of all cases).
noted that of those blind
schools in the USA that did keep information on the causes of blindness,
the top three causes were cortical visual impairment, retinopathy of
prematurity and optic nerve
hypoplasia. There had been a
significant increase in both cortical vision loss and retinopathy of
prematurity in the preceding
10 years. It was noted that there were marked regional differences both in
the prevalence and causes of paediatric blindness, but as with elsewhere
studied these were based on socioeconomic factors. As noted earlier,
there is no national registry of the blind in the USA and the authors
concluded that there was a need for more complete and uniform data based
on the WHO reporting format.
CHILDHOOD BLINDNESS IN AUSTRALIA
Australia, Fraser undertook a study into the causes of blindness in two
schools in South Australia with a total of 50 pupils
between the ages of 5-18 years.
Several were the offspring of immigrants (27 of the 100 parents had been
born outside Australia and three of the children). Of the 50 children
examined, 25 had acquired, prenatal causes of blindness of which the major
cause (20%; 10 cases) was due to prenatal rubella, followed by retrolental
fibroplasias (retinopathy of prematurity) (10%; 5 cases). The number of children affected by
genetic causes of blindness was 17 (34%) of which retinal aplasia (Leber
produced the highest number (n = 6). Blindness from uncertain causes was
recorded in 8 children. Of the 10 children diagnosed as rubella embryopathy, 5 were severely deaf and
four had milder hearing loss whilst 6
of the 10 had been born in 1958 suggesting a particularly severe epidemic
in the second half of 1957. One of the other interesting features noted
was the presence of 2 children in this small series with sex-linked
myopia. Another large unconnected group was also found in South Australia
leading Fraser to conclude that the prevalence of this condition was
unusually high in males in this region and possibly attributable to
CHILDHOOD BLINDNESS IN LATIN AMERICA (LAC)
Whilst Central, and South America
(including the Caribbean) cover an area of extreme diversity
geographically and socioeconomically, very little is known about the
magnitude of childhood blindness within the region.(46)
In 1988, Foster
indicated that 25% of childhood blindness in Latin America resulted from corneal scarring
as a consequence of malnutrition and ocular infections, occurring mainly
in the rural areas.(54)
Gilbert et al highlighted that
retinopathy of prematurity was becoming a major cause of potentially preventable blindness in
middle income countries, in essence a second epidemic, in middle income
countries that have introduced neonatal intensive care services.
In Cuba for example, retinopathy of prematurity accounted for 38.6% of
childhood blindness. The true size of the
problem is not known, as many of these countries do not have blind
A study which does not fall easily into the
above two categories is one by Moriarty in1988 in Jamaica of
108 children aged 5-15 years.(57)
This study showed similarities to that of Fraser’s(3)
in the UK in that the rate of hereditary disease was 48% (UK 50%).
Moriarty highlighted that, in Jamaica, rubella often affects those of
childbearing age, being the leading preventable cause of childhood
for 22% of children examined. This is in contrast to the studies in
Cyprus, Lebanon, Saudi Arabia and Nigeria, where rubella is usually
contracted at a pre-childbearing age. The major difference between this
study and Fraser’s UK study is the total absence of blindness from
perinatal causes in Jamaica resulting from the lack of premature babies
care. Whilst there was little consanguinity in the Jamaican population,
the village population is endogamous and the social practice whereby a man
may father children by several women makes it difficult to establish
precise lines of heredity. It is interesting to note also that the recent
economic climate in Jamaica, which had been characterised by increasing
poverty, unemployment and rising food prices, led to an increase in
hospitalisation for malnutrition and
vitamin A deficiency in addition to the reappearance
of xerophthalmia after an absence of ten years.
In a study by Gilbert et al in 1994
of 421 children in Chile in ten schools for the blind, 318 (76%)
were found with severe visual loss. (58)
Of these, 29.6% were attributable to hereditary factors; 22.5% to
perinatal factors; 11.2% to childhood factors and 8.2% to intra-uterine
factors. Aetiology could not be determined in 28.5%. retinopathy of
prematurity accounted for
17.6% of all children with severe visual loss suggesting that it was
becoming an increasingly important cause of blindness. It was also
estimated that 50% of children had avoidable blindness.
Rojas et al studied 202
children at the school for the blind in Lima, the referral centre for all
severely visually impaired Peruvian children. Some 53% of blindness was
caused by congenital and hereditary disorders. The leading causes are leucoma (15.3%), congenital glaucoma, congenital cataract and retinal degenerations
(11.9% each), and optic atrophy and retinoblastoma (8.4% each). The
latter reflected the advanced stage of the disease in these children.
Measles was the cause of the leucoma in 51% of that category; a finding
similar to that reported by Olurin in Nigeria. Measles accounted for 10%
Onchocerciasis in Latin American
Onchocerciasis remains a problem in 6 countries in Central
and South America (Brazil, Colombia, Ecuador, Guatemala, Mexico and
Venezuela) in localised areas affecting the extremely poor.(46),(61)
However, it is not perceived to be a serious health problem in these
OEPA has been active in these countries since 1990.
CHILDHOOD BLINDNESS IN
In Sub-Saharan Africa (SSA) (and also
Asia), the picture of childhood blindness is very different from the countries visited so
far. An IAPB Report(63)
in 1984 stated, “ignorance, poverty,
superstition, adverse cultural practices and some fatalistic indifference,
contributed to the gravity of the problem in Africa”. Seventy percent of
blindness in SSA was due to corneal scarring, the main causes of which
were xerophthalmia and measles, a pattern that echoes in many African
countries including Malawi, Kenya, Tanzania, Ethiopia and Nigeria.
Reduction in corneal scarring from improved measles immunisation coverage
rates has been achieved in some African countries such as Ethiopia and
Childhood blindness was preventable
in 50.7% of the cases and an additional 17.3% were blind from causes that
were potentially treatable. These figures for avoidable/preventable
blindness were reported across the board in SSA including Malawi (67.2%)
and Uganda (56.7%), Kenya (28.6%) and South Africa (38.8%).
The above report split the causes of
blinding conditions geographically,(63)
showing onchocerciasis present in most countries between the latitudes 15º
north and 15º south, the worst areas being the savannah zones. Trachoma
was endemic in the Sahelian belt and the Sudan as well as many countries
in central and southern Africa. Congenital cataract was common throughout Africa and this,
combined with congenital glaucoma, was found to account for blindness prevalence ranging
from 1% in East Africa, to 4-16% in West Africa, thus demonstrating wide
regional differences, although the reasons for this are unclear.
Measles remains a
major problem in Africa and many other developing countries. It affects 30
million children a year, causes up to 1 million deaths annually and is the
single leading cause of childhood blindness in low-income countries.
Olurin in Nigeria in 1970, in a study of 140 children (age
range 2 months to 14 years),
found the major pathology to be keratitis (21%) of which the largest
was measles. This was followed by cataracts (19%), (only 5 of the 26 cases
being genetic in origin), and optic atrophy (14%; all due to acquired
causes). Thirty-three years later Ezegwui et al
studied 142 residents of 3 schools for the blind in southeast Nigeria.
Childhood factors from corneal scarring, predominantly as a result of
measles, have remained a major cause of blindness in the country. It is
interesting to note that hereditary factors had increased from 12.7% in
the 15 years plus cohort, to 19.6% in the <15 years cohort. However, in
another study in 2002, by Akinsola et al,
of 26 children below the age of 16 years with visual impairment in a
blind school in Lagos, Nigeria, there were very few cases of corneal scar
(measles-/vitamin A deficiency). Hereditary conditions formed 38.5% of the cases,
intrauterine factors 23.1%, other causes 15.4%, and in 23% the cause was
unknown. Retinal dystrophy was the most common cause of low vision and
blindness, while congenital cataract and glaucoma were the major causes of avoidable
blindness. Anatomical sites of diseases leading to low vision and
blindness in these children were retina (30.8%), lens (23.1%), glaucoma
(19.2%), cornea (11.5%) and optic nerve (7.7%).
Chirambo’s study in 1976 of 270
students attending 17 blind schools in Malawi, found that 73% of the total
number were blind before the age of 3 years.(74)
The most common cause for the blindness was ocular infections (75.2%).
Measles as a single cause was responsible for 43.7% of the cases, and
smallpox for 5.2%. Bacterial infections were incriminated in 26.3% of
cases. Hereditary factors as causes of blindness were found in only 7.8%
of the cases. These included congenital cataract (2.6%), optic atrophy of unknown origin
(3%), and microphthalmos (1.5%). Similar findings were reported by Benezra
and Chirambo in 1977 who estimated the prevalence of blindness in children
< 5 years as 0.34/1,000 children. Direct ocular infections were
responsible for blindness in 32% of the cases (bacterial infections 20%
and measles 12%).(75)
Traditional eye medicines (TEM) added to
the severity of the ocular morbidity, leading to total melting of the
cornea and protrusion of the uvea in all cases. Congenital conditions
(excluding retinoblastoma) formed 30.8% of the total, 11 of these were
cases of congenital cataract. A high incidence of cortical blindness (9.3%) was noted.
Trauma was implicated in 5.3%, while retinoblastoma was found in 8%.
All cases of bilateral blindness in this
age group in Malawi in 1983 were considered to be due to vitamin A
deficiency. The disease was not only a leading cause of blindness in this
area, but may have an important impact on child survival as well.
Central African Republic
causes of blindness in the CAR in 30 children were; corneal scarring
(17%), congenital cataract and optic atrophy (13.5% each), iritis and microphthalmos (10%
each), glaucoma (7%), and trachoma and phthisis bulbae (3.5% each).
This is a country with a low socio-economic
status in which children make up almost 50% of its 65 million inhabitants.
An U5MR of 176/1000 live births is an unacceptably high figure, even by
sub-Saharan standards. A study covering three blind schools visited in
2001 found that the causes of childhood blindness were attributable mainly to
vitamin A deficiency and
measles (49.8%); whilst hereditary disease, such as retinal dystrophies
accounted for only 3.4%. (67)
It was estimated that 70% of blindness was due to either corneal opacity
or phthisis bulbi; and in 40% of patients with non-congenital bilateral
corneal opacities or phthisis bulbi, which was preceded by measles.(78)
O’Sullivan in 1997 documented hereditary
causation in 33% of the 1,311 children examined whilst acquired
conditions accounted for only 11.5%. (69)
In 41.5% it was not possible to determine the underlying cause, although
it was estimated that in 38.8% of those studied the cause was avoidable.
There were major variations in causes between the different ethnic
groups, the major difference being the higher proportion of retinopathy of
prematurity in white
and Indian children.
in Sub-Saharan Africa
There has been controversy over the major
causes of corneal scarring in Africa, with debate centring on vitamin A
keratitis caused by human alpha herpes virus 1 or 2; the use of
traditional eye medicine;
measles; and exposure keratopathy. There is a close correlation between
measles and vitamin A deficiency that can result in xerophthalmia, with corneal
ulceration, keratomalacia and subsequent corneal scarring or phthisis bulbae. Herpes simplex keratitis predisposed to 20% of measles related
corneal ulcer in Tanzania.(66)
The importance of these conditions varies geographically and temporally
depending on famine, measles epidemics and the availability of eye
The pathogenesis of corneal scarring and
the ensuing blindness in Africa have been well explained in the literature.(54),66)
Whatever the cause, corneal ulceration leading to corneal scarring was
found to be responsible for 70% of childhood blindness and 1-4% of African children with
acute measles will develop corneal ulceration. In Tanzania 84% of
bilateral corneal ulcers were found to be due to vitamin A deficiency (79)
and in northern Kenya, corneal scarring from xerophthalmia (and trachoma)
was the main cause of blindness not only in children but also up to the
age of 35 years.(80)
BLINDNESS IN ASIA
Asia is a vast and diverse continent whose
countries fall into five different categories of the World Bank ranks
which vary from the technically advanced Japan, rapidly growing China and
India, and the developing countries. These rates of development are
reflected in the causation of childhood blindness.(2),
The lack of blind registration creates
difficulties in assessing the prevalence of childhood blindness in Asia, together with the
significant scarcity of surveys of blind schools. The socioeconomic
diversity in this continent produces a vivid mix of causations ranging
from those seen in Europe to those seen only in the poorest countries such
as nutritional blindness, as is the case in many parts of South East Asia.
In the middle, there are many countries that have overcome the odds and
achieved good progress in combating this problem, such as Sri Lanka,
Myanmar, and Korea.(82)
The magnitude of vitamin A
considerable with 83 million school-aged children (23.4%), of whom 9
million (10.9%) were found to have mild xerophthalmia (night blindness or Bitot’s spots). Fortunately, potentially blinding corneal xerophthalmia is
negligible in these children.
an economic entity group in its own right,
estimates of the number of
children with SVI/BL in 1995 was at least 200,000 from a total blind
population of the world of 5 millions. Of these, approximately 15,000 were
in schools for the blind (84)
confirming that only 5-10% of
blind children in India are in special educational establishments.(85)
Significant interstate variations were
recorded in the prevalence of SVI/BL ranging from 7.5% in Kerala to 26.7%
in Madhya Pradesh. In addition, major differences were found between
urban and rural locations where the percentage was 7.5% in the capital
city blind school compared with 30.4% in a blind school in a rural area of
the Tamil Nadu state. (86)
In two population based studies of 6,935 children at or below the age of 15
years in the southern Indian state of Andhara Pradesh, the prevalence of
SVI/BL was found to be 0.17%.
The causes of childhood blindness in India appear to have
changed little in the span of 28 years since Jain’s study in 1968.(88)
In a more recent study by Sil and Gilbert in 2001 of 2,283 children in 11
Indian states, 50% of cases were still either preventable or treatable.
The single most important disease causing SVI/BL in India is vitamin A
affecting 18.6% of children.85),
Anterior segment pathologies remain the
major cause of blindness. A study in 1993 found that corneal
scarring/phthisis bulbi formed 38.4% of the cases of SVI/BL followed by
retinal causes at 22.6%. The latter was mainly made up of retinal
Hereditary factors account for 26%-29.8%. (89)
Retinal blindness formed 22.6% of the causes of blindness and was made up
mainly of retinal dystrophies accounting for between 60-75% of hereditary
causes (21.3%). Congenital eye anomalies were another important cause.(87)
This trend was confirmed by another
study 2 years later where the major causes of SVI/BL were corneal
staphyloma, scar and phthisis bulbi (mainly attributable to vitamin A
microphthalmos, anophthalmos and coloboma, 20.7%; retinal dystrophies and
albinism 19.3%; and cataract, uncorrected aphakia and amblyopia 12.3%.
Avoidable Blindness in India
Of the 50% avoidable blindness in India,
preventable causes formed 30% of cases and treatable 20%.(85)
Refractive errors are an important cause and formed 33.3% of cases in the
state of Andhara Pradesh, 16.6% of which were due to preventable causes
(8.3% each due to vitamin A deficiency and amblyopia after cataract surgery).(87)
Priorities for action to reduce childhood blindness in the context of Vision 2020 were
considered to be refractive error, cataract related amblyopia, and corneal
It has been suggested that this mixed pattern puts the population in India
in an intermediate position between the developing countries and
industrialised countries. (90)
Bangladesh, known as earth of mud and
water, is one of the poorest countries in the world where in
most parts diarrhoeal diseases are prevalent. In
a survey conducted in 1976 of a few union councils of the districts of
Chittagong, Comilla and Noakhali, in a population of 114,624, 1,085 cases
of blindness were identified (243 children and 842 adults).(91)
The most common cause of
blindness in children was corneal infection (cataract in adults), followed
by trauma in 26.7% of children versus 10.2% in adults. (92)
There has also been an emphasis
on research evaluating the prevalence and magnitude of nutritional
blindness from vitamin A deficiency in Bangladesh.(56),(92), (93)
A prevalence of 1.09 / 1000 and 0.64/1000 in the urban and rural
population respectively was found in a nationwide survey conducted in
1985 on 22,000 children aged 3 months to 6 years in rural and slum urban
Night blindness combined with conjunctival xerosis and Bitot’s spots were
present in 1.69/1000 persons and all combined stages of active
xerophthalmia were seen in 0.06/1000.(94)
Night blindness alone was found in only 0.03/ 1000 and males had a
significantly higher prevalence than females at 2.9/1000 and 1.2/1000
respectively. The rate of corneal scarring from keratomalacia was 0.31/1000,
whilst corneal opacities from other causes were seen in 2.25/1000
An intervention programme was
conducted between 1986 and 1989 in the northern Ranjpure district of
Bangladesh to reduce the morbidity of nutritional blindness. The efficacy
of the programme was evaluated in two cross sectional studies in 1986 and
1989 and concentrated on children < 9 years of age.(93)
A reduction in the prevalence of night blindness from 50.7% to 26.7% was
found over the period. However, the post intervention prevalence varied
between areas. There was no statistically significant difference in the
sex ratio. Higher father income, higher mother literacy, and smaller
family size were associated with low prevalence of night blindness in the
1989 cross-sectional study.
The pattern of childhood blindness seen in Sri Lanka was
typical of a growing number of South East Asian countries undergoing
rapid development, where vitamin A deficiency was not a significant cause of visual
In a study of 226 children
with blindness or severe visual impairment, cataract was found to be
responsible for 17% and was the commonest avoidable cause of SVI/BL.
Bilateral microphthalmos accounted for one-quarter of those examined.(95)
Nepal is another poor country in Asia where
vitamin A deficiency
is common and a major cause of blindness and loss of vision among children
in the eastern plains of the country.(97)
Active or past xerophthalmia was found in 15.4% of 4601 children aged
0-10 years by Hennig et al.(98)
The peak age for active corneal
xerophthalmia was 3 years and that of non-corneal xerophthalmia was 5
years. Prevalence of blindness in children under 15 was found to be
0.63/1000 children in a nationwide survey reported in 1988.(56)
Trachoma is another ocular disease that is prevalent in Nepal, especially
the follicular type. Intense inflammatory trachoma was relatively rare and
scarring was absent in the preschool population. It was concluded that the
population studied were not at high risk of repeat infections leading to
blindness in adulthood.
A survey in the only available
school for the blind in Eastern Nepal was conducted by Panda et al in 1999
and reported that 41.25% of causations were retinal in origin. Avoidable
conditions formed 46.25% of cases, with 38.75% being preventable and the remainder
treatable. Lenticular causes formed only 4% of the eye conditions.
only study available from Indonesia was that of 16 students in a school
for the blind in Bandung in 2003; 96.4% of the students were blind and 3%
severely visually impaired.(103)
The main causes of SVI/BL were corneal pathologies (staphyloma, scarring
and phthisis bulbi) followed by retinal dystrophies at 20.6% (mainly Leber
and early onset retinitis pigmentosa). Congenital cataract formed 13.3% of the series and microphthalmos / anophthalmos 10.9%. The whole globe was the main
anatomical site of primary pathology
(32.7%) followed by the
retina (20.6%), cornea 17.6%, lens (13.3%), optic nerve (6.1%) and uvea
(4.3%). Hereditary and infective causes constituted 42.4% and 29.7%
Ocular toxoplasmosis was found
to be a common sight-threatening disease in Indonesia among children in a
laboratory study evaluating 41 children under the age of 12 years, 56 of
whom were blind.(104)
A study by Reddy in 2001 in Malaysia found
that hereditary causes were responsible for 29.5%, whilst intrauterine
factors and perinatal factors were responsible for only 4.5% and 9%
respectively. The aetiology was unknown in 49.1% of cases which included
congenital anomalies of the globe. The author concluded that perinatal
screening for intrauterine factors and hereditary diseases would help in
reducing the prevalence in this region.(105)
Thailand and the Philippines
Gilbert and Foster in 1993 examined 256
children in schools for the blind in Thailand (1 school) and the
Philippines (3 schools).(106)
The causes of visual loss were similar in both regions with perinatal
factors accounting for 20% and 23%, and hereditary disease 13.8% and 17.7%
in Thailand and the Philippines respectively. In the total study, 15% of
children were blind as a result of retinopathy of prematurity and 9% from corneal scarring
attributed to vitamin A deficiency. A total of 58% of children were suffering from
avoidable causes of visual loss.
An earlier study of 129
students between the ages of 3 to 19
years (the predominant age group being 6-15 years) from the School for the
Blind in Khon Kaen, Thailand found that pathologies affecting the whole
eye were the leading cause of blindness (36.2%) and that nearly half of
the cases of blindness were preventable or treatable. Only 26 students
(20.5%) had positive family histories. The M/F ratio was 2.63:1. Of all
the students seen, 26 students (20.5%) were suitable for treatment that
succeeded in improving vision in 42% of them. (107)
Vitamin A deficiency has been
evaluated in the above two countries in separate studies. (108), (109)
Vitamin A deficiency was considered an important public health
problem by Bloem
et al in rural Thailand,(108)
demonstrated in the prevalence of night blindness, Bitot’s spots, and
deficient serum retinal levels. The prevalence of night blindness was 1.3%
and Bitot’s spots 0.4% in children aged 1-5 years in rural areas, while
this pathology was absent in urban regions. Of the children between 1-8
years, 9.6% had deficient retinal levels. In the Philippines a
survey of vitamin A deficiency was conducted in 1991 on the island of Mindanao on 248
preschool children in five randomly selected rural communities on the
outskirts of Davao City. (109)
Subclinical levels were found in 29% and clinical levels in 6%. A recent
history of diarrhoeal disease, reported night blindness, maternal
education of less than nine years, and infrequent consumption of eggs,
mangoes, and liver were associated with an increased risk of vitamin A
In Vietnam, trachoma and xerophthalmia are
very common and retinopathy of prematurity is emerging as a cause of visual morbidity. The risk
and severity of retinopathy of prematurity appears to be higher in larger and older infants in
Vietnam than the rest of the world.(110)
A study by Hu in 1987 revealed the
results of a mass screening of 700,000 people with more than 5,000
pedigrees of genetic eye disease. Unfortunately this did not contain a
breakdown of the age groups studied.(111)
It is interesting to note however that as early as 1978 a clinic for
genetic eye disease had been established with a genetic counselling
Another study conducted in 1999 of 1245
blind school students between the ages of 5 to 15 years from 36 blind
schools in 18 provinces by Hornby et al, (112)
found 91% of the students in the SVI/BL WHO category. The commonest
anatomical sites for visual impairment were the whole globe (essentially
microphthalmia) in 25.5%, retina (mainly retinal dystrophies) in 24.9%,
lens in 8%, optic nerve in 13.6%, and glaucoma in 9%.
Corneal conditions were not a
significant cause of visual morbidity. Hereditary factors contributed to
30.7% of cases and childhood causes to 14%. An earlier study in 1992
reported that hereditary conditions formed 84.46% of the causes of
blindness and low vision in China. (113)
A similar pattern was demonstrated in a
more recent study undertaken in 2002 by Shi-Yu and Zuomin-Xu who assessed
385 children attending seven blind schools in Eastern China between April
1998 and May 1999 using the WHO examination record. Of the 385 children
examined 356 (92.5%) were blind or severely visually impaired with the
commonest anatomical sites being the lens (27.5%), followed by the retina
(22.5%), and the whole globe (15.2%). Hereditary factors were found in
35.1% followed by prenatal factors in 6.2% (ie drugs or alcohol taken
during pregnancy) and meningitis in 5.3% of cases. (114)
Avoidable Blindness in China
Avoidable blindness in China ranged between
36.5% to 46.5% of cases of blindness. Potentially preventable cases formed
15% to 23% and potentially treatable 22.5% to 24.4%.(85),
These results reveal that this country has
gained from improvements in health and socioeconomic status so that
nutritional and infective causes of blindness are uncommon and hereditary
factors are very much to the fore.
It was concluded that the results reflected
the improved health and socioeconomic
status of China; although it was felt that
it might also reflect a bias, with higher socioeconomic students over
represented as a result of a bias in admission to, and location of blind
schools. The study demonstrated a shift from nutritional infective causes
to hereditary and unknown factors in childhood blindness.(113) (114)
Vitamin A Deficiency in China
The prevalence and spatial distribution of
vitamin A deficiency in China among children under six years of age were addressed by Lin
et al who studied 8,600 children under 6 years of age in 14 cities and 28
counties of 14 provinces using a stratified cluster sampling for survey,(115)
including interview with
questionnaire for their family information and nutritional status. Vitamin
A deficiency was found to exist in children, especially in the remote and
poverty stricken rural areas of China and it was recommended that vitamin
A supplementation was urgently needed for the children in these regions.
In this survey, 8 cases of night blindness and seven cases of
xerophthalmia were found among the children at ages of 2-5 and 61 mothers
of the children in this group were also found to be suffering from night
blindness. All the cases of night blindness and xerophthalmia, both in
children and mothers, were living in rural areas.
The prevalence of vitamin A deficiency was 15.0% in the
rural areas and 5.8% in urban areas, in contrast to 23.3% in the
poverty-stricken counties. In the coastal, inland and remote areas, the
prevalence was 5.8%, 11.5% and 16.8% respectively. There was a
significant difference in serum levels of vitamin A between ages, but no
significant difference between genders. Babies under six months of age
accounted for 33.4%, and those at ages of 4-5 years for 8%.
In Mongolia a study by Bulgan and Gilbert
found a prevalence estimate that was lower than anticipated together
with a pattern of SVI/BL similar to that found in blind school children in
China and very different from other Asian countries.(116)
A total of 64 students were examined who had been referred from a variety
of sources in 10 of the 18 provinces of Mongolia. The source of referral
was; family doctors (52); home visits (3); hospital records (4) and
schools for the blind (5). Lesions of the lens were the most common cause
(34%), followed by central nervous system disorders (19%) and retinal conditions
(12.5%). Whilst 27% of causes were hereditary, 17% of children were blind
following acquired conditions, meningococcal meningitis being the most
common preventable cause. Other preventable causes were rare and the
authors concluded that better management of conditions requiring surgery
and low visual aids were necessary.
Japan is the only Asian country which
belongs to the Established Market Economies rank of countries.(2),
The two studies by Nakajima(117)
in Japan have shed light on
in that country. Nakajima’s study in 1982 revealed that the prevalence of
blindness among school children dropped from 0.65/1000 in 1900 to
0.08/1000 by 1980.(117)
Changing Pattern of Blindness in Japan
Blindness from infection and malnutrition
were replaced by congenital causes.
One of the major differences in Japan was
the role of consanguinity. According to Nakajima, the rate of first cousin
marriage in 1950 was 5%; this had dropped to 0.1% by 1980.(117)
Tsukara’s study in 1985 of 67 pupils
at Yamanashi Blind School found 5 of the pupils were the product of first
cousin marriages and there was a history of consanguinity in 12.2% of
those blind from hereditary causes.(10)
This study found that hereditary causes were very probable in 41.8% of
cases; probable in 10.4%; and possible in 20.9%. This broke down into an
incidence of autosomal recessive inheritance being very probable in 42.9%;
probable in 14.3%; and autosomal dominant in 10.2%. When compared to
Phillips and Fraser’s study, the pattern of hereditary diseases was fairly
similar with cataract being the main cause followed by retinitis
degeneration and retinopathy of prematurity. (9)
There were no cases of blindness associated
with multiple handicaps in Yamanashi School.
on Interpreting Data from Blind Schools Surveys
Whilst examining the above figures, it is
necessary to point out that in some developing countries, only about 10%
of blind children are in blind schools and
therefore the surveys of blind school
pupils are potentially biased. This must of course be balanced against the
advantages of one examiner using a standard method and examining a large
number of children in a relatively short period of time.(58)
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