Treatable causes of blindness in a school for the blind in Nigeria
Related content
Blindness amongst children has been attributed to many causes, most of which in developing countries occur during early childhood (e.g., vitamin A deficiency and measles infection). In industrialised countries highly specialised medical manpower and adequate facilities allow identification of babies and children with ocular disease, and treatment and follow up of children who need intervention. The opposite is the case in Nigeria, a developing country where inadequate medical manpower, a large, mainly rural population and lack of necessary facilities can result in children becoming blind (or remaining blind) from preventable or treatable causes. In Nigeria there are no known community based programmes to screen newborn babies or young children for eye conditions needing treatment.
The introduction of special education in Nigeria has, to some extent, improved the outlook for some children with severe visual impairment or blindness. However, studies undertaken in other developing countries have shown that some children in schools for the blind have conditions that could be treated. This situation may be the same in Nigeria. The present study was undertaken in Abia State, South East Nigeria, to determine the causes of blindness, and to identify children and young people who needed treatment.
Subject and methods
The Government-sponsored special education centre for the blind is in Afara, Umuahia in Abia State. The catchment area includes Abia, Imo, Rivers and Cross River States. The school in Abia has 107 students, and the study population (62 out of 107) consisted of all students, except those who were Braille-reading university students.
Ophthalmic examinations were carried out in the school by one consultant and three resident ophthalmologists. Where possible, visual acuity was measured using a Snellen chart, and categories of visual loss recorded according to the World Health Organization’s definitions. All subjects had an eye examination to determine the cause of the visual loss. Anterior segments were examined with a torch and loupe, and, where the media allowed, the fundus was examined using a direct ophthalmoscope. Pupils were dilated, if necessary, using mydrilate 1% and phenylephrine 10%.
Data were recorded on the WHO Eye Examination Record for Children with Blindness and Low Vision.1 The main anatomical site, as well as the underlying cause of visual loss for the eye were recorded. If the causes were different in the two eyes the most preventable or treatable cause was selected.
Table 1. Categories of visual impairment by sex
WHO category |
Male |
Female |
Total |
---|---|---|---|
Severe visual impairment (<6/60 – 3/60) |
3 |
– |
3 |
Blind (<3/60 – light perception) |
15 |
12 |
27 |
Totally blind (no light perception in both eyes) |
15 |
17 |
32 |
Total: |
33 |
29 |
62 |
Table 2. Causes of visual loss in 62 students (anatomical site)
Cause |
Male |
Female |
Total (%) |
---|---|---|---|
Cataract |
8 |
7 |
15 (24.2) |
Corneal scarring/staphyloma |
6 |
5 |
11 (17.7) |
Phthisis bulbi |
7 |
7 |
14 (22.6) |
Optic atrophy |
4 |
2 |
6 (9.7) |
Buphthalmos |
3 |
2 |
5 (8.1) |
Retinal conditions |
2 |
2 |
4 (6.5) |
Uveitis |
3 |
0 |
3 (4.8) |
Aphakia/amblyopia |
0 |
2 |
2 (3.2) |
Prostheses |
0 |
2 |
2 (3.2) |
Total: |
33 |
29 |
62 (100) |
Results
Of the 62 subjects, 33 (53.2%) were male and the ages ranged from 10 to 26 years (mean 18 years). The majority of students had become blind between the ages of 2 and 15 years. Twenty-one were born blind, while two did not know when they became blind.
Categories of visual impairment are shown in Table 1. Three students were severely visually impaired, 27 students (43.6%) had visual acuities of less than 3/60 to light perception, and 32 (51.6%) were totally blind.
Table 2 outlines the anatomical causes of visual loss. Cataract, diagnosed in 15 (24.2%) students, was the single commonest cause, and all were associated with nystagmus. Corneal scarring and staphylomas were seen in 11 students (17.7%). Other causes included optic atrophy in 6 (9.7%), buphthalmos in 5 (8.1%), and retinal conditions (retinitis pigmentosa and retinal detachment) in 4 students (6.5%). Phthisis bulbi from a variety of causes was seen in 14 students (22.6%) and 2 had artificial eyes. Amblyopia associated with aphakia was the cause of blindness in 2 students while 3 others had signs of old uveitis.
Twenty-one students had conditions needing treatment (33.9%). Twelve students needed cataract surgery, and several students with central corneal scars would benefit from optical iridectomies.
Discussion
Although there were 107 students in the school only 62 were examined, as the remainder, who were mainly university students, declined to be examined. Of those examined there were more males than females. This may reflect the Igbo tradition where male children are given more attention in terms of education and upbringing than their female counterparts.
About half the children examined had some residual vision, but only three had sufficient vision for independent mobility. The remainder were totally blind in both eyes but were able to find their way around due to familiarity with the environment.
The proportion of children in this blind school study who had visual loss from unoperated cataract, or amblyopia following cataract surgery was high. In other blind school studies undertaken in Africa approximately 10% of children are severely visually impaired or blind from cataract. Although the students in this study with unoperated cataract almost certainly have amblyopia, late surgery and aphakic correction offers the possibility of improving their functional vision.
Nutritional blindness and blinding infectious diseases remain a major problem in Nigeria. In this study corneal scarring and staphyloma were attributed to measles infection and vitamin A deficiency in many students. Optical iridectomy offers the possibility of improving the vision in people with central corneal scarring, and several students in this blind school were referred for this procedure. Most students with phthisis bulbi gave a history of measles infection. Vitamin A deficiency and measles are preventable causes of blindness, and the results of this study confirm the findings of other blind school studies, undertaken in African countries, which suggest that up to 70% of the causes of blindness in children are either preventable or treatable. More emphasis needs to be given to health education, for mothers in particular, to emphasise the need for measles immunisation, and the importance of a balanced diet (including breast feeding for babies) within the limits of locally available vitamin A rich foods.
Herbal remedies had been used to treat the eyes of some of the students who had measles-related causes of blindness. Health education will help parents to realise that herbal eye ‘remedies’ may be harmful.
In some of the children with glaucoma, optic atrophy, cataract and retinitis pigmentosa the condition may have been genetically determined. There is a need for genetic counselling services in developing countries.
Conclusions and recommendations
It is clear from this study that it is imperative to have children examined by an eye specialist before they are accepted into special education in order to identify those with treatable conditions. Once a child is accepted into special education they can acquire the label of being a ‘blind child’, and, if ophthalmologists or other cadres of eye care worker do not visit the school, the child is unlikely to be identified as needing treatment. While many children with cataract and corneal scarring are likely to have amblyopia, particularly if the condition has not been identified early, surgery does offer the possibility of an improvement in vision.
In order to detect treatable diseases early, such as cataract and glaucoma, screening programmes need to be introduced at the primary level of health care. For example, school screening programmes have been successfully introduced in several developing countries.
Health education is needed, aimed primarily at mothers, to reduce the incidence of preventable blindness from measles infection and vitamin A deficiency.
Acknowledgments
We deeply appreciate the cooperation of the pupils and teachers of Afara Blind School, and especially the Head Master, Mr Nkem Nwankwo. We wish to thank the members of the Nigerian Medical Association (NMA), Umuahia Zone, who sponsored the survey.
References
Gilbert C, Foster A, Negrel A-D, Thylefors B. Childhood blindness: a new form for recording causes of visual loss in children. Bull WHO 1993; 71: 485-9.