الخلاصـة: حُدِّدت أسباب، ومدى انتشار العمى بين 048 29 طفلاً تقلّ أعمارهم عن 16 عاماً، ينتمون إلى جميع الأُسَر التي تضمُّها خمسة مخيّمات للنازحين داخلياً في الخرطوم، بالسودان. وفي أعقاب زيارات قام بها عاملون صحيون مدرَّبون من منزل إلى منزل، خضع 916 طفلاً لإجراءات تقيـيم إضافية، تبيَّن من خلالها إصابة 2.7% منهم بالعمى، و1.6% بضَعْف وخيم في البصر، و5.5% بضَعْف في البصر، وفق معايـير منظمة الصحة العالمية. وقُدِّر انتشار العمى بين الأطفال في المخيمات بـ 1.4 لكل 1000 من الأطفال، وتبيَّن أن الأسباب الرئيسية للإصابة بالعمى هي عتامات القرنيـة (40%) الناجمـة بشكـل أساسـي، عـن عَـوَز الفيتاميـن A، يليهـا الغَمَش amblyopia (32.5%).

ABSTRACT: The prevalence and causes of visual impairment and blindness were determined in 29 048 children < 16 years in all households of 5 camps for internally displaced people in Khartoum State, Sudan. After house-to-house visits by trained health care workers, 916 children received further assessment, 2.7% of whom were found to be blind, 1.6% to be severely visually impaired and 5.5% to be visually impaired, according to World Health Organization criteria. The prevalence of blindness in children in the camps was estimated as 1.4 per 1000 children. The leading causes of blindness were found to be corneal opacities (40.0%), mainly due to vitamin A deficiency, followed by amblyopia (32.5%).

Prévalence et causes de la cécité infantile dans les camps pour personnes déplacées de Khartoum : résultats d'une enquête auprès des ménages

RÉSUMÉ: La prévalence et les causes des déficiences visuelles et de la cécité ont été déterminées chez 29 048 enfants de moins de 16 ans dans chacun des foyers hébergés dans 5 camps pour personnes déplacées situés dans l'État de Khartoum au Soudan. À la suite d'une enquête porte à porte effectuée par des personnels de santé dûment formés, 916 enfants ont fait l'objet d'une évaluation approfondie : 2,7 % d'entre eux étaient atteints de cécité, 5,5 % de déficience visuelle partielle et 1,6 % de déficience visuelle grave, selon les critères de l'Organisation mondiale de la Santé. La prévalence de la cécité chez les enfants logés dans ces camps a été estimée à 1,4 pour 1000 enfants. Les principales causes de cécité identifiées étaient l'opacité cornéenne (40,0 %), essentiellement due à une carence en vitamine A, suivie de l’amblyopie (32,5 %).

¹Department of Community Medicine, Faculty of Medicine, University of Khartoum, Khartoum, Sudan (Correspondence to Z. Zeidan: drziedan61@hotmail.com). ²Walidain Eye Hospital, Khartoum, Sudan ³London School of Hygiene and Tropical Medicine, London, United Kingdom. Received: 28/02/05; accepted: 25/09/05

 

Introduction

Five per cent of worldwide blindness involves children younger than 15 years of age; in developing countries this age group constitutes 50% of the population. By World Health Organization (WHO) criteria, there are 1.5 million children worldwide who are blind: 1.0 million in Asia, 0.3 million in Africa, 0.1 million in Latin America and 0.1 million in the rest of the world. There are marked differences in the causes of childhood blindness in different regions due to different socioeconomic factors. In developing countries, 30% to 72% of such blindness is avoidable: 9% to 58% is preventable and 14% to 31% is treatable. The leading cause of blindness in children in developing countries is corneal opacification caused by a combination of measles, xerophthalmia and the use of traditional eye medicine [1]. Infectious diseases, malnutrition, vitamin A deficiency and measles are the main causes of avoidable blindness in children of poor countries [2].

In Sudan there is an absence of population data on the prevalence of blindness in children. However, the prevalence of blindness in all ages in Sudan was found to be 1.78%, the major causes being cataract, corneal opacities, uncorrected refractive errors, trachoma and onchocerciasis [3].

It has been found that the causes of blindness in children are the same as the causes of under-5 mortality (e.g. premature birth, measles, vitamin A deficiency, congenital rubella syndrome and meningitis) [4]. Therefore the under-5 mortality rate can be taken as a proxy indicator to estimate the prevalence of child blindness. In Sudan, the under-5 child mortality rate was found to be 104/1000 live births.

The number of displaced people in Sudan has been estimated to be about 4 million [5]. The primary reason for leaving their origin was war, followed by food insecurity, economic opportunities and employment. Approximately 340 000 internally displaced persons (IDPs) live in the 5 official camps, which are located at the peripheries of 3 large cities (Khartoum, Khartoum North and Omdurman). They live in cardboard or mud houses in poor hygiene conditions and with a lack of water supply [3]. The results of an interagency household survey in displaced camps in Khartoum indicate that the crude mortality rate for children under 5 years is near the emergency threshold of 1 per 10 000 per day. The main cause of death in all areas is diarrhoea. Other causes included chest infections, pneumonia and measles [6]. Clearly living conditions are poor in the camps and child mortality is high, which suggests visual impairment may also be high among such children.

We aimed to determine the prevalence and leading causes of visual impairment and blindness in children in the above-
mentioned camps. The outcome of this study will provide baseline information that may assist in measuring the progress of the VISION 2020 programme in fighting causes of childhood blindness in the country.

Methods

Subjects

Children under 16 years who were living in the IDP camps around Khartoum for at least a 6-month period before the study were the target population.

The 5 IDP camps in Khartoum State are Mayo Farms, Jebel Awlia, El Salaam, Wad el Bashier and Karton Kassala with a total populations of 72 621 during the study period (5–10 October 2003). Each camp was divided into 30 clusters, each having between 34 and 66 households, i.e. average population per cluster ranged between 408 and 792 individuals. Every 7th household in each cluster was visited.

The eligible children were those under 16 years who had been living in these households for a minimum period of 6 months before the survey and contracted eye problems from birth until the time of the study. Health workers who were trained in conducting field surveys to detect eligible children with eye problems or defective vision were involved in the house-to-house surveys. The health worker asked the parents whether their children had recent or previous eye problems, or if they had noticed any change in the eyesight of their children. Visual acuity was not measured during household interviews, but children with eye problems were registered and the heads of the households were given a card and requested to be present with their children on pre-determined days in the camp clinics to see the ophthalmic medical assistants and optometrists to assess their eye problems and visual acuity.

Examination in the field

Children found by the field health workers to have eye problems were later examined in the camp clinics by an examination team using portable equipment. The examining team in each camp consisted of 4 ophthalmic medical assistants, 1 optometrist, 2 medical officers, who were trained in the eye hospital, 2 health workers from the local health units of the camps, 5 medical students, a records clerk and a driver. At the camp clinic, each child was first registered by the health workers and a history was taken from each child or their parents by the health workers or medical students. Visual acuity was measured in each eye separately at 6 m and 3 m using a Snellen E chart. Impairment in visual acuity in children under 5 years was determined by showing bright objects. The following WHO categories of visual loss were used for visual acuity in the better eye: 6/18 or better – not impaired; < 6/18–6/60 – visual impairment; < 6/60–3/60 – severe visual impairment; < 3/60 – blind [7]. Trained ophthalmic medical assistants using a 4× magnifying loupe and a hand-held flashlight examined the anterior
segment of the child’s eye. Posterior segments were not examined at this level.

Acute eye problems were treated free of charge. Children with complicated eye diseases or visual acuity < 6/18 were referred to Alwaldain Eye Hospital, Omdurman Province. Transport was offered free of charge.

Examination in eye hospital

At the referral eye hospital, the ophthalmologist reviewed the field results. In children aged 5 years or more the external eye and anterior segment were examined using a slit lamp and posterior segments were examined with a direct ophthalmoscope after dilating the pupils, if necessary. A diagnosis of glaucoma was made on the basis of anterior and posterior segment signs, as visual testing was not possible. Glaucoma cases were assessed using a Schiotz tonometer to assess intraocular pressure.

Visual acuity was measured again and refraction was performed for all children. If there was difficulty measuring visual acuity in children under the age of 3 years of age, they were examined and refracted under local anaesthesia.

For each child with a visual acuity of < 6/18 in the better eye, the examining ophthalmologist sought to identify the reasons for visual loss.

All the findings were recorded on a data sheet and were entered into a database. The data were analysed using SPSS, version 10.

Results

The target population included 29 048 children under 16 years of age. Of these, 1115 children were registered by the health workers as having a history of recent or previous eye problems during the house-to-house interviews. Of these, 916 came to the camp clinics where they were examined and treated by the field team; 105 of them were found to have visual acuity < 6/18 and were referred to the eye hospital for further refraction and examination.

Out of the 105 referred to the eye hospital, 15 were found to be severely visually impaired (visual acuity < 6/60 in the better eye) and 25 blind (visual < 3/60). The prevalence of severe visual impairment among the referred children was 1.6% whereas the prevalence of blindness was 2.7% and the prevalence of blindness and severe visual impairment together was 4.4% (Table 1).

The prevalence of blindness was higher in males compared to females although this difference was not statistically significant, but it was significantly higher in the older age group than in the younger age groups in males (P < 0.05) (Table 2).

The commonest anatomical sites of visual loss in the 40 blind and severely visually impaired children were the corneas in 40% (corneal scaring), the higher centre of the brain in 32.5% (amblyopia), the lens (cataract) in 12.5%, retina in 7.5%, the whole globe in 2.5%, optic nerve in 2.5% and uvea (glaucoma) in 2.5% (Table 3).

In all, 35 (87.5%) of the blind or severely visually impaired children presented with avoidable causes of blindness and vision loss: vitamin A deficiency (22.5%), trauma (10.0%) and measles (7.5%), which are preventable causes, and amblyopia (32.5%) and cataract (12.5%), which are treatable causes (Table 4), although amblyopia is only treatable up to 9 years of age.

Of the 40 children with severe visual impairment and blindness, 23 were referred for surgery, 10/23 (43.4%) for corneal scaring and 8/23 (34.8%) for cataract surgery (Table 5).

Discussion

The prevalence of blindness in children varies between countries as it is influenced by socioeconomic status, and it is reflected by the childhood mortality rate. While eye lesions are the main causes in high-income countries, corneal scarring due to measles and vitamin A deficiency are the main causes in low-income countries [1]. In our study the prevalence of blindness and severe visual impairment in children in displaced camps in Sudan was 1.4/1000, which is consistent with the prevalence of childhood blindness in low income countries with low under-5 mortality rates, where the prevalence may be as high as 1.5 per 1000 children [8]

Our rate is similar to some population-based studies in other countries. For example, the prevalence of blindness was 1.5/1000 in the age group of 5–15 years in Chile but the main causes of blindness were not available [9]. In India it was found to be 1.2/1000 in the age group of 7–15 years, where retinal disorders, corneal opacities, congenital anomaly and amblyopia were the main causes of blindness [9]. In Nepal the prevalence of blindness was found to be 1.5/1000 in the age group of 5–15 years, but the main causes of blindness were not available [9].

Examining the main causes showed that corneal scarring (mostly related to vitamin A deficiency disorders) and lens opacity (cataract) were responsible for 40% and 13% of childhood blindness and severe visual impairment respectively. These 2 conditions are entirely avoidable (prevention for vitamin A deficiency disorders and early diagnosis and surgical treatment for cataract). Our result is consistent with the recommendations and priorities of WHO VISION 2020 initiative which identifies corneal scarring and cataract as the major causes of childhood blindness in most developing countries [7].

The majority of surgical operations that were done at the eye hospital were for corneal opacities and cataract, which suggests the need to initiate a training programme on paediatric eye surgery for the doctors, so as to prevent further complication to blindness.

Although 25 blind cases and 15 with severe visual impairment are a small number, not all cases were determined by initial screening and thus these figures are an underestimate of the number of cases. Nonetheless out data provide useful baseline information for programme planners involved in addressing childhood blindness in Sudan.

Improving vaccination for measles and distribution of vitamin A supplements will assist in prevention of severe visual impairment and blindness in the majority of children in these camps. A public health eye programme based on VISION 2020 should be established to combat childhood blindness problems focusing on the primary health care level.

Acknowledgements

This study was supported by Muslim Aid UK under their programme of Fighting Child Blindness.

Special thanks are extended to the Minister of Health, Khartoum State and the staff of the Alwaldain Eye Hospital for their great help during the study. We would also like to thank Mrs Sulafa Ahmed for her valuable help as optometrist. Finally, we thank the community leaders in all the camps in Khartoum State for their support and assistance.

References

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2. Clare CE et al. Prevalence of blindness and visual impairment in children – a review available. Ophthalmic epidemiology, 1999, 6:73–81.

3. National plans for eye care in Sudan – a five year plan 2003–2007. Khartoum, Federal Ministry of Health, 2002.

4. Tielsch JM et al. Prevalence and severity of xerophthalmia in southern Malawi. American journal of epidemiology, 1986, 124(4):561–8.

5. Sudan demographic, socioeconomic profiles for return and reintegration planning activities: IDP Household Report. Khartoum, CARE and International Organization for Migration, 2003

6. Report of Interagency household survey in IDPS Khartoum State. Khartoum, Sudan, Humanitarian Aid Commissionaire, 2004.

7. Preventing blindness in children: report of a WHO/IAPB scientific meeting, Hyderabad, India, 13–17 April 1999. Geneva, World Health Organization, 2000.

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9. Pascolini D et al. 2002 Global update of available data on visual impairment: a compilation of population-based prevalence studies. Ophthalmic epidemiology, 2004, 11, 2:67–115.