Prevalence of blindness in Ogun State, Nigeria

KAMORU SAKIRU REPORT THE OGUN STATE PREVALENCE HELD  IN 2002.

Prevalence of blindness in Ogun State, Nigeria

African Journal of Biomedical Research, Vol. 6; 63 - 67 (2003)

Original Article

THE PREVALENCE AND CAUSES OF BLINDNESS AND LOW VISION IN

OGUN STATE, NIGERIA.

FASINA F. O. AND *AJAIYEOBA A. I.

Department of Ophthalmology, University College Hospital, Ibadan, NIGERIA.

The prevalence and causes of blindness and visual impairment were determined in Yewa-North

local government area of Ogun state, Nigeria between May 15 and June 22, 2001. A population

- based survey using a random cluster sample of 1,964 persons representing usual residents

of the local government area was examined. The survey revealed that 1.22% of the populations

were blind, 1.43% unilaterally blind and 2.09% were bilaterally visually impaired. Blindness and

visual impairment were found in persons aged 45yrs and above. Blindness was found to be

2.43 times commoner in men, which was statistically significant. Cataract was the commonest

cause of blindness accounting for 37.5% of blindness and 36.6% of visual impairment. Another

important cause of visual impairment and blindness in this study was pterygium accounting for

23% and 19% of unilateral and bilateral visual impairment and 7% and 4% of unilateral and

bilateral blindness respectively. The report showed that 87.5% of the blindness and 75.7% of

the bilateral visual impairment were avoidable. These largely agreed with the pattern and

causes of blindness in other parts of sub-Saharan Africa.

Key words: prevalence, causes, Blindness, visual impairment.

* Author for correspondence

INTRODUCTION

Blindness is not only a personal tragedy;

it is an economic nightmare. An

estimated 45 million people are blind,

and 135 million people are visually

impaired world wide. Of these 90% are

from developing countries (Abiose, 1999)

The Global initiative, Vision 2020 :

the right to sight has a mission to

eliminate the main causes of avoidable

blindness in order to give all the people

of the world, particularly the millions of

needlessly blind, the right to sight by the

year 2020. To achieve this there must be

an appropriate definition of blindness,

and reliable statistics on the number of

blind persons, the distribution, the

population at risk and the causes of

blindness. Prevalence of blindness varies

from country to country and within

regions in the same country. In

developed countries, prevalence of

blindness ranges from about 0.05% to

0.2 %. Earlier in a study by Tabara et

al.(1986) revealed blindness prevalence

as high as 10% in Saudi Arabia.

Yewa - North local government area

is one of the twenty local government

areas in Ogun state - one of the 36

States of Nigeria, situated in the Southwestern

part of Nigeria. The population of

the local government according to the

1999 projected census figure (based on

the 1991 census) is 190, 853. It is

bounded in the north by Imeko - Afon

LGA, in the west by the Republic of

Benin, in the south by Yewa south and

Ipokia LGAs and in the east by Abeokuta

North and Ewekoro LGAs. There is no

form of orthodox eye care delivery

services (whether government, mission

or private owned) situated in the local

government.

The purpose of this study was to

assess accurately the prevalence and

causes of blindness in Yewa- North local

government area.

MATERIALS AND METHODS

The basic survey design was a 2-

stage random cluster sampling model.

The local government has been divided

into 8 health districts, each comprising of

70-80 villages. 4 districts were randomly

African Journal of Biomedical Research 2003 (Vol. 6) / Fashina and Ajaiyeoba

Prevalence of blindness in Ogun State, Nigeria 64

selected in each health districts making a

total of 8 villages. Each village has an

average of 50 homes and each home an

average of 6 people giving an average of

300 people per village. 8 villages were

selected making a total of 2,400 people

that were registered. The survey team

include the authors, three staff nurses,

two clerks from the local government

secretariat that helped in identification

and registration of the people, and a

driver.

The World Health organisation for

prevention of Blindness (W.H.O. /PBL)

record format and the W.H.O. definition

of blindness and visual impairment were

used.

W.H.O defined blindness as visual

acuity of less than 3/60 (20/400, 0.05) in

the better eye with best possible

correction, or a visual field loss in each

eye to less than 100 from fixation. Low

vision was defined as visual acuity of

less than 6/18 (20/60), 0.3) but equal to

or better than 3/60 in the better eye with

best possible correction.

All registered persons had visual

acuity done in front of their houses.

Those with visual acuities less than 6/18

in either eye were transported to a health

centre where ocular examinations were

performed by the authors.

Minor ailments were given prescriptions

and others were referred as indicated.

Fundus examination was performed with

the direct ophthalmoscope and where

indicated dilated fundoscopy was done.

Routine Shiotz s tonometry was done on

all individuals age 40 years and above

with visual acuity less than 6/18 in either

eye. Glaucoma suspects also had

Shiotz s tonometry performed on them.

Classification of blindness and

diagnosis were done as recommended

by the W.H.O. Precoded examination

record forms were used for recording in

accordance with the W.H.O. / PBE eye

examination format.

RESULTS

A total of 1,964 persons (children and

adult) were examined. These were 865

males and 1098 females giving a male:

female ratio of 1: 1.27. This female

preponderance occurred in all age

groups apart from the 15-29 year age

group. Children and adolescence within

the age group 0-14 formed 25 % of the

sample, whilst elderly people above

60years of age constituted 26.02%. The

age and sex distribution of the sample

population is shown in Table 1.

Of the 1964 individuals examined

during the study, 24 were blind in both

eyes whilst 28 were blind in one eye. The

prevalence of blindness and visual

impairment is shown in Table 2.

Table 1:

Age and Sex Distribution of sample population

Age range

(Years)

Male (%) Female

(%)

Total (%)

0 14 230

(11.71)

261

(13.2)

261

(13.29)

15 29 119

(6.06)

117

(5.96)

117

(5.96)

30 -44 125

(6.36)

189

(9.62)

189

(9.62)

45 59 197

(9.52)

225

(11.46)

225

(11.46)

60 and above 204

(10.39)

307

(15.63)

307

(15.63)

Total 865

(44.04)

1099

(55.96)

1099

(55.96)

Table 2

Prevalence of blindness and visual impairment

Category of

Visual loss

No. of

persons

Prevalence (%)

U B U B

Blindness

(VA<3/60) 28 24 1.43 1 . 2 2

Visual

Impairment

<6/18 but>3/60

13 41 0.66 2.09

Total 41 65 2.09 3.31

U = Unilateral; B = Bilateral

The prevalence of blindness was

1.22%, while the prevalence of visual

impairment was 2.09%. The prevalence

of blindness and visual impairment were

found to be much higher in the elderly.

Most bilateral blinds were 45 yrs of age

and above. Table 3 shows the age and

sex distribution of blindness and visual

impairment.

Cataract was the main cause of

blindness and visual impairment in this

survey. It accounted for 37.5% of

bilateral and 50% of unilateral blindness.

Cataract was responsible for blindness in

African Journal of Biomedical Research 2003 (Vol. 6) / Fashina and Ajaiyeoba

Prevalence of blindness in Ogun State, Nigeria 65

individuals aged 45 yrs and above.

These comprised 44.4% within the 45

59 years age group, while 55.5% were

60 years and above. Pterygium was a

major cause of visual impairment

accounting for 19.5% of bilateral and

23.08% of unilateral visual impairment.

However only one (1) person (4.2%) was

bilaterally blind from pterygium. which

had encroached and crossed over the

visual axes. 2 (7.1%) others were

unilaterally blind from pterygium. Other

causes of blindness found in this study

are as shown in Table 4.

DISCUSSION

This population based survey revealed a

blindness prevalence of 1.22 % in

YEWA North local government area of

Ogun State. At the same time, it gives an

estimate of the magnitude and causes of

blindness in the local government area.

A prevalence of blindness of 1.22%

found in this study is higher than the

national average of 1.0% but is lower

than the 1.92% recorded for Ikenne local

government area of the same Ogun

state(Ajibode, 1999). It is higher than the

0.5% W.H.O. (1987) estimates for

southern Nigeria. The higher rate in this

study may be partly due to the relatively

high representation of persons above the

age 40 yrs. Also is the fact that the

W.H.O. estimate was not mainly based

on population based surveys but partly

on the assumption that health services

are readily available in most parts of

southern Nigeria.

Many authors (Zubair,1996; Abiose

et. Al, 1996 and Adejor, 1993) had

confirmed that the prevalence observed

in this study lie within the figures

recorded for their community-based

studies carried out in Nigeria. Ajibode

(1999) had observed in a cross sectional

survey of Ikenne LGA in Ogun State of

Nigeria, that the prevalence of blindness

Table 3

Age and sex distribution of blindness and visual

impairment.

Age (yrs) Blindness Visual impairment

U (%) B (%) U (%) B (%)

0-14 1 (0.20) 3 (0..61) 0 (0.00) 1 ( 0 .20)

15-29 2 (0.85) 0 ( 0 . 0 0) 0 (0.00) 5 ( 2 . 12)

30-44 1 (0.32) 0 ( 0 . 0 0) 1 (0.32) 4 ( 1 . 27)

45--60 9 (2.18) 9 ( 2 . 1 8) 8 (1.94) 1 0 ( 2 .43)

> 60 15 (2.94) 1 2 ( 2 . 35) 4 (0.78) 2 1 (4.11)

Total 28 (6.49) 2 4 ( 5 . 1 4) 13 (3.04) 4 1 ( 1 0 . 1)

U = Unilateral; B = Bilateral

Table 4:

Causes of blindness and visual Impairment

Causes Blindness Visual Impairment

U (%) B (%) U (%) B (%)

Globe 2 (8.3)

Cataract 14 (50.0) 9 (37.5) 6 (46.15) 15 (36.6)

Uncorrected aphakia 1 (4.2) 2 (4.9)

Central corneal opacity 5 (17.9) 1 (7.69)

Pterygium 2 (7.1) 1 (4.2) 3 (23.08) 8 (19.5)

Glaucoma 4 (14.3) 5 (20.8) 5 (12.2)

Posterior segment (optic atrophy) 3 (10.7) 6 (25.0) 3 (23.08) 9 (22.0)

Refractive error 2 (4.9)

Total 28 (100.0) 24 (100.0) 13 (100.0) 41 (100.0)

U = Unilateral; B = Bilateral

and low vision were 1.92% and 4.81%

respectively. Similar observation was

also made by Oluyadi (1995) in his study

of Egbeda LGA of Oyo State, Nigeria

where he noted a prevalence of 1.1% for

blindness. Zubair (1996) in Asa LGA of

African Journal of Biomedical Research 2003 (Vol. 6) / Fashina and Ajaiyeoba

Prevalence of blindness in Ogun State, Nigeria 66

Kwara state also observed prevalence of

1.7% and 5.8% for blindness and low

vision respectively. In Nnewi LGA of

Anambra state, Ezepue (1984) had noted

that the prevalence of blindness and low

vision to be 2.0% and 3.3% respectively.

In Garki district of Northern Nigeria,

Budden estimated the prevalence of

blindness to be 1.5% and for

onchocerciasis endemic areas of Kaduna

state, while Abiose (1989) obtained the

prevalence of 1.8% for Kauru district of

Saminaka local government of Kaduna

state. Meanwhile Adejor (1993) in

Otukpo LGA of Benue State estimated

the prevalence to be 0.78%.

The prevalence of low vision of

2.08% is lower than that reported from

other local government areas in Nigeria.

For example Adejor (1993) in Otukpo,

Benue state reported 4.81%. In Ikenne,

Ajibode (1999) Ogun state noted 4.81%

whilst in Nnewi, Anambra state Ezepue

reported 6.8%. Our result is similar to

that of Dambatta LGA of Kano state,

where Lawal (1997) reported a

prevalence of 2.05%.

However our result is higher than 1.4%

prevalence reported from Gambia by

Faal (1989). This is probably due to

variation in magnitude and causes of low

vision in the different parts of Nigeria and

other parts of Africa.

The age distribution of blindness and

visual impairment in this study showed

that most of the blind were 45 yrs old and

above. Blindness has been found to

occur more commonly in certain age

groups than in others. In Scotland,

Vannas (1964) found the peak incidence

(63%) of blindness in the 65- 85yrs age

group. Also Chirambo (1986) in Malawi

and Tabara (1986) in Saudi Arabia

recorded the highest blindness

prevalence in the people over 60 years.

Similar findings were recorded by Forster

(1989) in Tanzania , Bucher et al (1988)

in South Africa , Whitfield et al (1990) in

Kenya and Tielsh et al (1990) in

America. These are largely age- related

blinding conditions like senile cataract,

glaucoma and macula degeneration,

which are common in this age group

This increase in the prevalence of

blindness and visual impairment amongst

the elderly in our environment is mainly

due to the high rate of cataract formation

and development of glaucoma at older

age with substantial increase in the

current rate of population growth.

Cataract was the most important cause

of blindness and low vision. The study

showed 37.5% bilateral blind for cataract

and in additional 36.6% visually impaired.

This is similar to findings in other parts of

Nigeria Abiose (1982), Adejor (1993) and

Ezepue1984) and also in other parts of

Africa - Faal et al (1989),

Chirambo(1986) and Buscher et al

(1988) and many parts of the developing

world - Taraba et al.(1986), Singh et al

(1988). Common causes of blindness in

developed countries include senile

macula degeneration, diabetic

retinopathy, cataract, glaucoma and

myopia were recorded by Vannas et al

(1964) and Lindsted (1969). Whereas the

major causes of blindness in developing

countries include cataract,

onchocerciasis, trachoma, keratitis

(measles and xerophthalmia), leprosy,

glaucoma and trauma as documented by

various workers in Africa Faal (1989)

Whitfield et al (1990) Kayembe (1985),

including Nigeria. Abiose (1982). Olurin

(1973) had documented the common

causes of blindness as cataract 39%,

chronic simple glaucoma 22%, Keratitis

(non - trachomatous) 9.7%, optic atrophy

6.7%, uveitis 5.9%, trachoma 4.2% and

trauma 2%. Adeoye (1993) in Osun

state found cataract 41% as the chief

cause of blindness. This has been

corroborated by Ayanru (1974) in the

Mid-western state of Nigeria. Our study

confirmed that cataract blindness is

indeed a problem and Akinsete (1993)

estimated the cataract backlog in Nigeria

as 600,000.

Optic atrophy was the second

predominant cause of visual loss.

Onchocerciasis was found to be the

major cause of optic atrophy. This is

similar to a population based study in

mesoendemic onchocercal communities

in Kaduna state by Abiose et al (1982) in

which onchocerciasis was responsible for

39.2% of blindness.

Other important cause of blindness in

the study was glaucoma. This is similar

African Journal of Biomedical Research 2003 (Vol. 6) / Fashina and Ajaiyeoba

Prevalence of blindness in Ogun State, Nigeria 67

to findings in other parts of Nigeria -

Adejor (1993), Ajibode (1999),Lawal

(1997). Among others causes of visual

impairment was pterygium . The reason

for the strikingly high prevalence of

pterygium in the local government area

requires further detailed study.

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Received: February 2002

Accepted: June 2002