Annals of African Medicine Annals of African Medicine Society ISSN: 1596-3519 Vol. 4, Num. 1, 2005, pp. 31-34

Annals of African Medicine, Vol. 4, No. 1, 2005, pp. 31-34

PATTERN OF BLINDNESS IN INSTITUTIONS FOR THE BLIND IN KADUNA, NIGERIA

A. V. Kehinde and S. C. Ogwurike

Department of Ophthalmology, Ahmadu Bello University Teaching Hospital, Kaduna, Nigeria

Reprint requests to: Dr. A. V. Kehinde, Department of Ophthalmology, AhmaduBelloUniversity Teaching Hospital, Kaduna, Nigeria

Abstract

Background/objective: An estimated 1.3% of the population in sub-Saharan Africa are blind. The aim of this study was to identify the causes of blindness in an institution for the blind in northern Nigeria.
Method: A prospective evaluation of 74 inmates at the Kaduna State Special Education School (KASSES) and Kaduna State Rehabilitation Centre, Kaduna.
Results: There were 53 males and 21 females between the ages of 6 – 65 years were examined. 39 inmates were seen at KASSES and 35 at the rehabilitation centre.  Measles presented as the commonest cause of blindness in 26 (35.1%) inmates. Of these, 16 were males and 10, females. This was followed by glaucoma in 14 (18.9%) inmates, 11 of which were childhood glaucomas. The third commonest causes of blindness were due to hereditary retinopathies and optic atrophy with 9 (12.2%) inmates each.
Conclusion: Measles remains a significant cause of blindness. Notable causes of blindness in the tropics such as trachoma and onchocerciasis appear to be disappearing in urban areas. The provision of potable water and improved sanitation will help to eliminate these diseases, in rural areas. There is also the need to establish low-vision aids services and eye banks to meet local needs.

Résumé

Le fond/objectif: Une évaluation de 1,3% de la population de l’Afrique sous-Saharan est aveugle. Le but de cette étude était d'identifier les causes de cécité dans une institution pour les aveugles au nord du Nigéria.
Méthode: Une évaluation éventuel de 74 aveugles à l’école pour Les élèves souffrant de difficultés d'apprentissage de l'état de Kaduna (Kaduna State Special Education School: KASSES) et le Centre de Réhabilitation de l'état de Kaduna (Kaduna State Rehabilitation Centre).
Résultats: 53 mâles et 21 femelles entre les âges de 6 - 65 ans ont été examinés. 39 aveugles ont été vus à KASSES et 35 au centre de réhabilitation. La rougeole a représenté la cause majeure de cécité parmi 26 (35,1 %) aveugles. De ceux-ci, 16 étaient des mâles et 10, les femelles.  La rougeole était suivi par le glaucome dans 14 (18,9 %) aveugles, dont 11 étaient les glaucomes d'enfance. Les troisièmes causes majeures de cécité était en raison d'héréditaire retinopathies et l'atrophie optique avec 9 (12,2 %) aveugles chacun.
Conclusion: la Rougeole reste une cause significative de cécité. Les causes notables de cécité dans les tropiques tel que trachome et onchocerciasis ont la possibilité de disparaître dans les secteurs urbains. La provision d'eau potable et une amélioration du système sanitaire aideront à éliminer ces maladies dans les secteurs ruraux. Il y a aussi le besoin d'établir les services d'aides de bas-vision et des banques des yeux pour répondre aux besoins locaux.

Introduction

Blindness is defined by the World Health Organisation (WHO), as visual acuity of less than 3/60,(20/200,0.05), or visual field of less than 10^o, and low vision is <6/18 (20/50,0.3) in the better eye with best correction. ¹ About 80% of the world’s blindness is avoidable, most of which occur in developing countries. Blinding eye diseases remain a highly prevalent and serious health problem in many developing countries. The WHO estimates that there are about 45 million blind people in the world, and about 135 million are believed to have low vision.² It is a condition with adverse social and economic burden on the family and society, particularly in developing countries faced with economic recession.

An estimated 1.3% of the population in sub-Saharan Africa are blind, ³ and the commonest causes of blindness are cataract, trachoma, onchocerciasis, glaucoma and childhood blindness. In children, corneal ulceration and scarring following measles and vitamin A deficiency, as well as harmful traditional eye practices⁴ are major causes of blindness. Cataract, genetic diseases, and congenital abnormalities are other important causes of childhood blindness.

Thirty-nine primary and secondary school students whose ages ranged between 6 - 26years were examined at the Kaduna State Special Education School, whilst 35 blind persons whose ages ranged between 10-65years were examined at the Kaduna State Rehabilitation Centre. Fifteen inmates declined to be examined at the centre.

A Snellen’s chart was used to measure visual acuity whenever possible in a brightly lit room. Eye examination was done using a pen torch and loupe for the anterior segment and a direct ophthalmoscope for the posterior segment. Refraction was done using a streak retinoscope where indicated. 1% Tropicamide and 2.5% phenylephrine were used to dilate the pupil when required. Data was entered into the WHO Eye Examination Record for blindness screening.

Results

There were 53 males (71.6%) aged 6 – 65 years (mean 26.4 years) and 21 females (28.4%) aged 10 – 65 years (mean 20.2 years). The M:F ratio was 2.5:1 (Table 1).

Two (6.7%) respondents had severe low vision and 72(97.3%) respondents were blind. Of these, 50(67.6%) respondents had visual acuity <3/60-PL and 22 respondents (29.7%) had no perception of light, NPL. Table 2 shows visual acuity in the best corrected eye by age and sex. The causes of visual impairment are shown in Table 3.

The commonest cause of visual impairment, by anatomical location in this study was phthisical/disorganised globe in 20(27%) respondents, all of which were measles related. In addition, 6 of the 8 respondents with corneal opacities lost their vision as a complication of measles. Of the remaining 2 respondents in this category, one person lost her vision following an attack of Steven-Johnson’s syndrome, and the other from exposure keratopathy whilst in coma during an attack of tetanus. Thus, measles was responsible for blindness in 26(35.1%) respondents. Glaucoma, 14(18.9%) respondents, was the second commonest cause of blindness, and optic atrophy with hereditary retinopathies caused visual loss in 9(12.2%) respondents each.  

Table 1: Age and sex of 74 inmates at institution for the blind  

Table 2: Visual acuity, age and sex of 74 inmates at institution for the blind  

PL: perception of light; NPL: no perception of light

Table 3: Causes of visual impairment in 74 inmates at institution for the blind  

Discussion

Much of the blindness in developing countries follow avoidable causes such as measles, trachoma, onchocerciasis and the use of harmful traditional eye medications.^{4 Corneal} scarring from measles related causes was found to be the leading cause of visual loss in Nigerian children.⁵ Sanford-Smith⁶ while reviewing paediatric out-patients presenting with corneal scarring at the Guinness Eye Clinic, Kaduna, found corneal ulceration in association with measles and xerophthalmia to be the leading cause followed by trauma and trachoma. Measles eye infections and malnourishment are inter-related.⁶ The effect of measles is worse in children with vitamin A deficiency. This is further compounded by increased susceptibility to viral Herpes simplex keratitis as well as bacterial infections such as staphylococcus, pseudomonas, etc. The Expanded Programme of Immunization, EPI, (now Nigerian Programme of Immunization, NPI) was formally launched in Nigeria in 1977 to immunize children from 0 – 5 years of age against the childhood killer diseases (measles, diphtheria, polio, etc). Immunization against measles is a clinically effective way of preventing measles blindness, as well as periodic administration of vitamin A. There is the need to organize mobile outreach clinics to remote villages in order to immunize young children. In addition electronic media can be used to educate mothers on appropriate weaning methods, using locally available foods rich in vitamin A.

Glaucoma rated second as a cause of blindness, 14(18.9%) respondents.  Only three of the fourteen respondents in this group were of the adult-onset type. There is a dearth of population-based studies on the prevalence and types of glaucoma in Africa. Several blindness surveys give an estimate of the prevalence of blindness from the glaucomas, in Africa.^{7 - 9} Olurin^{10 in} Nigeria, found glaucoma to account for 20% of blindness. 

The exact aetiology of primary congenital glaucoma still remains unclear. This has been due largely to a lack of knowledge about the normal development of the anterior chamber angle. Several postulations exist in literature by various workers.^{11 - 13} Surgical intervention provides the most definitive treatment for most forms of childhood glaucoma. Filtering surgery is usually employed when goniotomy and/or trabeculotomy either fails or is very unlikely to succeed. Many factors contribute to poor outcome from trabeculectomy in children, including lower scleral rigidity, more rapid healing and exuberant scarring process, and enlargement of glaucomatous eyes with thinning and distortion of intraocular anatomy. In Britain the use of low dose intra-operative beta irradiation to the surgical site has improved the success of trabeculectomy without complications.¹⁴ Subconjunctival 5-fluorouracil has been administered post operatively in children after trabeculectomy, resulting in successful filtration, but it’s administration usually requires multiple sequential anaesthesias, and is limited by corneal epithelial toxicity as in adults.^{15 Every} child whose glaucoma is well controlled after surgery (with or without adjunctive medical therapy) should have life-time follow-up. Although several inmates examined with congenital/childhood glaucoma had surgery in early childhood, defaulting on post-operative follow-up appointments led to early blindness from multifactorial causes. The control of intra-ocular pressure in all age groups and the management of vision in children in particular is the goal of long-term follow-up, after glaucoma surgery. The provision of Information and Counseling services in eye units would be useful in educating patients and parents of children with congenital and chronic eye disorders, who would require long term follow – up so that defaulting and self-discharge is reduced to the barest minimum.

Blindness associated with childhood cataract was present in 5(6.7%) respondents, four of whom had surgery in infancy. This is lower than that found by Umeh et al, who found cataract blindness of 24.2%(15 of 62 respondents) at the school for the blind, in Afara, Umuahia, Abia state, ¹⁶located in South-eastern Nigeria. There was improvement in vision from 1/60 to 3/60 with correction in one uncorrected aphakic 14-year-old boy. Cataracts in childhood not only reduce vision but also interfere with normal visual development¹⁷ Post–operative amblyopia management forms an integral part of visual rehabilitation in children.¹⁸

Five respondents, (6.7%) had corneal malformations. Two of them were brothers who had keratoglobus, with features of Marfan’s syndrome. A set of twin brothers and one unrelated female had keratoconus. Many eye clinics in developing countries lack the facilities for managing hereditary corneal dystrophy. In fact, eye banks are practically non-existent in many developing countries and response to organ donation has been very slow for socio-cultural reasons. In addition, the high cost of contact lenses when available has made it unaffordable for the average patient. Corneal grafting for keratoconus is a highly effective way of reducing blind years. A recent study demonstrated that corneal transplantation has a greater impact in sighted years in the developing world than does cataract surgery.¹⁹ The provision of low vision aid and genetic counseling services as well as the establishment of eye banks in developing countries will be of immense benefit to persons with genetically determined eye disorders, such as corneal dystrophies, hereditary chorioretinopathies and macula degeneration. 

Finally, no cases of trachoma or onchocercercal blindness were found in this study. Both diseases are essentially rural in nature. Abiose²⁰ in 1985, working in Kaduna, an urban city, found about only 8 cases of trachoma and 3 cases of onchocerciasis out of 500 children with eye disease.  In a recent survey, in 2001, Rabiu²¹ found in Katsina State, which shares a common border with Kaduna State, active trachoma in children in all of the 15 villages assessed and the presence of trichiasis in 14 of these villages. The provision of potable water and improved sanitation in urban centres has contributed to the disappearance of trachoma and onchocerciasis in these areas. The provision of these services in rural areas (and the mass distribution of Ivermectin to treat onchocerciasis) will contribute in no small measure to the elimination of avoidable blindness.

We sincerely thank the Principal of Kaduna State Special Education School (KASSES) Mrs. G. Bawa and the teaching staff as well as the Assistant Centre Manager of Kaduna State Rehabilitation Centre, Ms. Lydia Tonko, for granting their kind permission for this study.

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