A comparative analysis of avoidable causes of childhood blindness in Malaysia with low income, middle income and high income countries

Transcription

1 Int Ophthalmol (2015) 35: DOI /s x ORIGINAL PAPER A comparative analysis of avoidable causes of childhood blindness in Malaysia with low income, middle income and high income countries C. L. Koay D. K. Patel I. Tajunisah V. Subrayan V. C. Lansingh Received: 1 June 2013 / Accepted: 8 March 2014 / Published online: 22 March 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract To determine the avoidable causes of childhood blindness in Malaysia and to compare this to other middle income countries, low income countries and high income countries. Data were obtained from a school of the blind study by Patel et al. and analysed for avoidable causes of childhood blindness. Six other studies with previously published data on childhood blindness in Bangladesh, Ethiopia, Nigeria, Indonesia, China and the United Kingdom were reviewed for avoidable causes. Comparisons of data and limitations of the studies are described. Prevalence of avoidable causes of childhood blindness in Malaysia is 50.5 % of all the cases of childhood blindness, whilst in the poor income countries such as Bangladesh, Ethiopia, Nigeria and Indonesia, the prevalence was in excess of 60 %. China had a low prevalence, but this is largely due to the fact that most schools were urban, and thus did not represent the situation of the country. High income countries had the lowest C. L. Koay (&) D. K. Patel I. Tajunisah V. Subrayan Department of Ophthalmology, Faculty of Medicine, University Malaya, Kuala Lumpur, Malaysia chiangling@live.com.my V. C. Lansingh IAPB/VISION 2020 Latin America and Director of International Outreach in the Department of Ophthalmology, Hamilton Eye Institute at the University of Tennessee Health Science Center, Memphis, TN, USA prevalence of avoidable childhood blindness. In middle income countries, such as Malaysia, cataract and retinopathy of prematurity are the main causes of avoidable childhood blindness. Low income countries continue to struggle with infections such as measles and nutritional deficiencies, such as vitamin A, both of which are the main contributors to childhood blindness. In high income countries, such as the United Kingdom, these problems are almost non-existent. Keywords Childhood blindness Avoidable causes of childhood blindness Childhood blindness in Malaysia Introduction Childhood blindness is one of the major priorities of Vision 2020 the Right to Sight, a global initiative which was initiated in 1999 for the elimination of avoidable blindness ( Although childhood blindness only accounts for 1.4 million of cases of the global total of 45 million people with blindness, priority is given because children with blindness have a long life ahead of them [1, 2]. An estimated 500,000 children become blind each year. About 1 million children are blind in Asia, 300,000 million in Africa, 100,000 million in Latin America and 100,000 million in the rest of the world [1, 2]. The magnitude of the problem varies from high income countries to low income countries. The

2 202 Int Ophthalmol (2015) 35: estimated prevalence in high income countries is *0.3 per 1,000 children, whilst it is an estimated 1.5 per 1000 in low income countries [3, 4]. Globally, the cause of childhood blindness can be divided into avoidable and non-avoidable causes. Unavoidable causes of childhood blindness in the world include congenital abnormalities, retinal dystrophies and optic atrophy [3]. It is a well-known fact that almost half of all blindness in children, particularly those in the low to middle income groups, is due to avoidable causes such as paediatric cataracts that are amenable to cost effective interventions [4]. Together, the preventable and treatable causes of childhood blindness make up avoidable causes of childhood blindness. It is a wellknown fact that almost half of all blindness in children, particularly those in the poorest communities, is due to avoidable causes that are amenable to cost effective interventions [4]. The prevalence of blindness is higher in low income countries, where potentially blinding conditions are prevalent, such as vitamin A deficiency, harmful traditional eye remedies and cerebral malaria [5]. Preventive measures for conditions that have been controlled elsewhere, such as measles, congenital rubella or ophthalmia neonatorum, are inadequate [5]. Facilities and skilled personnel for managing conditions that require surgery are lacking [5]. In middle income countries and regions, the pattern of causes is mixed, and retinopathy of prematurity (ROP) is emerging as an important cause in Malaysia and Latin America [6]. Unavoidable causes represent the biggest group in developed countries and include hereditary retinal dystrophies, disorders of the central nervous system and congenital anomalies [7]. Due to the rarity of blindness in children, population-based surveys to determine the prevalence of blindness require very large sample sizes and are very costly. Consequently, in the period , only a few population-based studies were performed [8, 9]. Hence, most of the available data are obtained through examining children in schools for the blind. By and large, the data which are available is far from perfect, and gaps in the data are almost inevitable because of the difficulty in obtaining the data. Methods Data were obtained from the school of the blind study in Malaysia carried out by Patel et al. in Malaysia in 2007 [10]. A total of 32 schools for visually impaired children participated in the study. Detailed examinations were carried out in full detail by a research team consisting of a resident trainee ophthalmologist, an optometrist and a fellowship-trained consultant paediatric ophthalmologist. Visual acuity assessment using an ETDRS chart, and refraction was performed by a trained optometrist in children who were able to walk unaided, recognise faces or make social contact. The WHO classification system for children was used to categorise causes and also visual acuity [11]. Visual acuity of 6/6-6/18 was classified as no impairment,\6/ 18-6/60 classified as visually impaired,\6/60-3/60 as severe visual impairment and \3/60 perception to light and no perception to light were all classified as blind. [11] Anterior segment was examined with a portable slit lamp, and posterior segment examined with indirect ophthalmoscope after pupil dilation. Final diagnosis on the cause of visual impairment was made by the consultant paediatric ophthalmologist for all. Data summary was obtained using the Childhood Blindness Software version Persons under this study gave their informed consent prior to their inclusion in the study. This study was also approved by the ethics committee of University Malaya and has therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. We collated data from numerous previous studies done on childhood blindness between 2002 and 2012 in order to make a comparison between the avoidable causes of childhood blindness in Malaysia and those causes in low income, middle income and high income countries. The data available is, however, vast, and one needs to practice caution when interpreting this data. Low, middle and high income countries were categorised according to the World Bank Data [12]. Based on the World Bank data, Malaysia and China are classified as high middle income countries, Indonesia and Nigeria are lower middle income, Ethiopia and Bangladesh are low income, and the United Kingdom is a high income country. Avoidable causes of blindness include both treatable and preventable causes of blindness and include all blindness which could be treated or prevented by a known or cost effective means [1]. In contrast, unavoidable causes of blindness can neither be treated nor can they be prevented. Treatable causes include ROP, cataracts, glaucoma and uveitis. In itself, these conditions cannot be prevented from developing,

3 Int Ophthalmol (2015) 35: but timely treatment of these conditions might prevent the development of blindness. Preventable causes include ophthalmia neonatorum, adverse drug reactions, vitamin A deficiency and trauma. These conditions can be prevented altogether from happening and thus preventing the development of blindness. higher income countries, such as the United Kingdom [18], avoidable causes only made up about 20 % of all childhood blindness. ROP and cataracts seem to be important causes in middle income countries, where else in lower income countries, infections and malnutrition are the main culprits (Table 2). Results A total of 469 children in the study conducted in Malaysia were classified to have severe visual impairment/blindness (SVI/BL), 226 (50.5 %) of which had an avoidable cause of (SVI/BL). The remaining 223 (49.5 %) had unavoidable causes of (SVI/BL). ROP and cataract-/lens-related disorders made up the majority of the cases (17 % of the total 50.5 % of avoidable causes of SVI/BL) (Table 1). By comparison, in China, 30.5 % of the causes of childhood blindness were avoidable with cataracts as the most important cause. In lower income countries, we find that the prevalence of avoidable causes of childhood blindness becomes higher. For example, 53.9 % of childhood blindness in Indonesia is avoidable [13], and 74.5 % is avoidable in Nigeria [14]. Examples in the lowest income countries include Bangladesh, where 61.2 % of childhood blindness is avoidable [17] and Ethiopia (67.0 %) [15]. In comparison to Table 1 The preventable and treatable causes of blindness in Malaysia [10] Number of children Preventable causes Adverse drug reaction Trauma Ophtalmia neonatorum Vitamin A deficiency Total preventable causes Treatable causes ROP Cataract/Lens Glaucoma Uveitis Total treatable causes Total avoidable (preventable? treatable) causes % Discussion Childhood blindness in Malaysia and other parts of the world can be divided into the unavoidable and avoidable causes. The unavoidable causes made up 48.5 % of the total number of children with childhood blindness. The identified causes included hereditary causes, mainly retinal dystrophies, albinism, Stargardt s disease and corneal dystrophies. Disorders related to perinatal and neonatal included cerebral hypoxia resulting in brain damage. Other causes included neoplasms, and diseases acquired during intrauterine period such as toxoplasmosis and rubella both of which were uncommon. Avoidable causes identified were ROP, cataracts, glaucoma, uveitis, adverse drug reactions, trauma and ophtalmia neonatorum. The prevalence of avoidable causes is as such that ROP is 17.4 % in Malaysia. In the decade that preceded this current study, the prevalence of ROP increased threefold, [19] and this is thought to be due to the increasing number of preterm births, the increased survival of very low birth weight infants, and the improvements of neonatal and maternal services [20]. To curb the rising problem of ROP, in 2005, Malaysia began to adhere to a national clinical practice guideline (CPG) on ROP drafted by paediatric ophthalmologists, paediatricians and the Ministry of Health [21]. Screening was done at 4 6 weeks after birth and in infants with a birth weight B1,500 g and gestational age B32 weeks. Infants with an unstable clinical course are screened at the discretion of the attending neonatologist [21]. These criteria are similar to that of the American screening guidelines for ROP [22]. In high income countries, screening criteria are formulated for high-risk infants and are reviewed and revised as the population of infants at risk changes with time. As a result, there is now a lower prevalence of ROP in some of these countries [23].A study done in 2000 in England demonstrated that only 3 % of SVI/ BL was attributed to ROP [18]. As expected, with the lack of established paediatric care units in Bangladesh,

4 204 Int Ophthalmol (2015) 35: Table 2 The comparison between Malaysia and other selected countries [10, 13 18] Aetiology Causes of severe visual impairment and blindness Bangladesh Ethiopia Nigeria Indonesia Malaysia China United Kingdom Treatable causes (%) ROP Cataract Glaucoma Uveitis Total Preventable causes (%) Infections Ophthalmia neonatorum Vitamin A deficiency Trauma Adverse drug reaction Total Number of children examined 1, , Treatable and preventable (%) ROP was not found to be a major cause of SVI/BL in Bangladesh and represented only 1.3 % of all treatable causes [17]. This pattern was also seen in Indonesia as both these countries share similar demographics. In Indonesia, ROP was identified in only 3(1.8 %) cases (Table 2)[13]. This is because of the higher mortality of premature children, which do not survive the initial period to develop ROP. Furthermore, poor access to intensive care units further deepen the problem [13]. Interestingly, in a vast country such as China, the rates reported were acutely low. ROP was only seen in 2 % of children with SVI/BL [16]. This may be attributed to several reasons. There were twice as many cases with ROP in the urban area compared with the rural area, but the numbers were small. Many of the schools for the blind were rural based [16]. The low prevalence of ROP in Indonesia, Bangladesh and rural China, thus, reflect the lack of neonatal services. As a leading cause of surgically correctable blindness in the developing world, paediatric cataract is known to impose an enormous problem in terms of morbidity, economic loss and social burden to the country [24]. In this study, we found the lens-related disorders accounted for 17.2 % of the avoidable causes. A staggering one-third of the cases were untreated, and of those who received treatment, many were already amblyopic (Table 1) [11]. Several reasons were identified as possible factors, including the fear of surgery, a lack of awareness amongst the parents, inappropriate counselling, financial difficulty, a large family and poor parental commitment [10]. However, it is expected that as the country progresses towards becoming a high income nation, this is bound to change. In Indonesia, paediatric cataract was responsible for 13.3 % of SVI/BL [13]. The relatively low levels of the reported cases of cataracts are because the cases are most likely not brought to the attention [13]. Even if the cases are identified, it is interesting to note that in Indonesia, severe amblyopia often followed cataract surgery in all cases, and this was due to the delay in surgery, which was performed after the age of 3 [13] reflecting the level of ophthalmic care in this country. Cataract is the most common treatable cause of vision loss in Bangladesh, the rate far exceeding those of the other studies mentioned in this paper and stands at a high 27 % (Table 2). It is concluded that the problem lies in the lack of eye care services for children in Bangladesh and, therefore, many of these cataracts were not operated. In Nigeria, cataract made up 15 % of all cases of avoidable causes of SVI/BL [14]. In Ethiopia, the prevalence is *6.8 % [15]. Again, a low prevalence is observed probably due to the fact that many of the affected children are not brought to the blind

5 Int Ophthalmol (2015) 35: schools or treated. In Ethiopia, there are no specialist tertiary centres for the treatment of childhood eye disorders, and there are only 2 recently trained paediatric oriented ophthalmologists for a population of about 65 million [15]. In China, 19 % of children had SVI/BL from disorders of the lens [16]. Of these, 65 % was aphakic and/or amblyopic probably as a result of late surgery or inadequate refractive correction with 32 % having unoperated cataracts [16]. Lower income and middle income countries in Asia are plagued by several problems of paedtric cataract. Firstly, there is a lack of awareness amongst parents and caregivers regarding cataracts. Thus, these children receive medical attention too late and often are already amblyopic. Second, lower income countries lack the adequate facilities for the treatment of paediatric cataracts. Awareness in cataract in children, thus, should be a primary focus of the health ministries in these countries. A greater allocation of resource needs to be made to develop services for paediatrix cataract. Paediatric centres in the lower income countries should collaborate with those in high income countries that have the experience with paediatric cataract surgery, so that transfer of skills could be accomplished. The roles and responsibilities of each centre should be clearly defined. If possible, periodic visits, ongoing on-line consultation, and assistance with supply lines and equipment could further improve this relationship. Glaucoma/buphthalmos were other causes of treatable visual loss in Malaysia and accounted for about 7.6 % of all cases of avoidable causes of blindness. The proportion was similar to other studies found in Asia and Africa (Table 2). Glaucoma/buphthalmos was responsible for 9.3 % of childhood blindness in Nigeria [14]. Nearly half (46.2 %) of the children had previous filtration surgery. Auditing these surgeries, however, is difficult as the eyes of children respond differently from those of adults to surgical treatment [25]. In Indonesia, most of the buphthalmos/primary congenital glaucoma cases found in the study (9.1 % of SVI/BL) were in the late stage of disease at the time of presentation [13]. This prevalence is similar to studies in West Africa and Latin America but is also greater than prevalence in other countries studied in Asia [25].In the United Kingdom, less than 5 % of the cases were attributed to glaucoma [7, 18]. Screening and early detection of glaucoma with appropriate referral to the tertiary care centre are required as early treatment will affect the outcome of the vision. In Malaysia, where malnutrition is rare and where there is a good immunization programme for children, no cases of corneal scarring were reported by Patel et al. [10]. Corneal pathology, mainly scarring, was the second most common cause of SVI/BL in Bangladesh and was because of either vitamin A deficiency or ocular infections such as measles. This is consistent with other studies from developing countries [26 28]. In Bangladesh, measles remains the fifth most common cause of childhood deaths (20,000 deaths annually). In response to this, the Measles Initiative Bangladesh Campaign was recently announced and implemented [29]. This was the largest ever measles immunisation campaign which targeted approximately 33.5 million children aged 9 months to 10 years. Other controls carried out included intermittent vitamin A supplementation as part of the Expanded Programme of Immunization (EPI), home gardening and nutrition education [30]. A staggering 44.7 % of corneal scarring is the leading cause of blindness in children in schools for the blind in Ethiopia [15]. Similar to Bangladesh, corneal scarring was mainly caused by vitamin A deficiency/measles, which could have been prevented through provision of basic primary healthcare services [15]. In Nigeria, corneal scarring and phthisis bulbi together constituted a major cause of childhood blindness, which are associated with measles and vitamin A deficiency [14]. With improved immunisation coverage, the incidence of measles related corneal ulcer has been reported to be on the decline since mass distribution of vitamin A had been included in the National Programme on Immunisation (NPI) in Nigeria [30]. Indonesia still had a high incidence of this in their country [13]. Corneal staphyloma, corneal scars and phthisis bulbi were responsible for 29.7 % of SVI/BL cases and were closely related to both measles and vitamin A deficiency [13]. In China, the cases of corneal scarring were surprisingly low. Only 2.7 % of SVI/BL was attributed to vitamin A deficiency [16]. However, as the authors pointed out, this may not be the true representation of the situation in their country, as there are no schools for the blind in the sparsely populated, poorer western part of China, and many of the schools reported difficulty in recruiting younger children [13]. Thus, where malnutrition is not an issue and where effective immunization against measles is present, a cause of blindness due to scarring of the cornea can be eradicated over time.

6 206 Int Ophthalmol (2015) 35: Limitations Studies into childhood blindness inevitably have several limitations. For one, the data that obtained are retrospective. This applies for all the studies cited in this paper. Furthermore, as demonstrated in this paper, the studies cited are from different years and thus may not be an accurate head on comparison. However, where possible, the latest studies are cited to bridge the gap. In Malaysia, data collected by examining children in schools for the blind can provide valuable information on the cause of childhood blindness; it is invariably subjected to selection bias. In Patel s study, the sample obtained from the 24 schools is estimated to represent only 22.4 % of the total number of school-age children in Malaysia who are blind. Children with other physical disabilities may have been precluded from attending school. Children with other disabilities, such as those who are cortically blind (often from prematurity), children who are deaf and blind (rubella) and so on, may not have ever been brought to the schools. The reasons why these children may not have been enroled in these blind schools and, more evidently so, in schools in East Malaysia are because of parental fear, financial difficulty and social stigma associated with any physical disability [11]. Data collected for the study in Ethiopia indicated that not all regions of the country were uniformly represented as only the majority of the blind children came from only 3 out of the 5 main regions of Ethiopia indicating that regions of Somali and Gambella were undeserved [14]. In addition, the study indicated that neither the rural nor the urban population could be represented in the study. This is because despite its proximity to Addis Ababa the capital of Ethiopia, only 5.1 % of the children are seen in Semeta School for the blind. It seems that due to cultural reasons in Ethiopia, there were more males in the schools, as there is a greater value accorded to males in their society. The study conducted in Wiyata Guna School for the Blind in Indonesia accepts mainly children whose only disability is blindness (98.2 %) [13].The remainder had mild systemic disabilities. This is quite different from those of countries of high income, as they tended to take in all children regardless of the severity of their physical disability [13] Thus, it is likely that this study does not represent the whole children population in Indonesia. The study in China [16] concentrated mainly on the more affluent states of Eastern China, and, thus, rural areas were not represented. Furthermore, as in Indonesia, children with severe disabilities were often not allowed to be institutionalised in these schools [16]. Conclusion Currently, the 2 main avoidable causes of childhood blindness in Malaysia are ROP and cataract. Together, they make up 34.6 % of the total 50.5 % of avoidable childhood blindness in our country. Whilst these problems are also encountered by countries such as Indonesia, Bangladesh, Nigeria and Ethiopia, their problems seem to centre on blindness secondary to infectious processes and malnutrition. As such, in order to have prevalence found in high income countries, namely the UK, as far as ROP is concerned, screening criteria need to be adopted. As far as paediatric cataracts are concerned, ophthalmic services need to be improved in line with the development of the country. On the community level, preventive services need to be developed and/or improved, as they are at the forefront of the management of childhood blindness. These include conducting screenings to children at schools. Primary health care workers should be competent in using the direct ophthalmoscope to identify neonates with cataracts and refer accordingly. Other specific areas to be managed include immunization, counselling to prevent consensual marriages in hereditary cataract and to encourage follow-up in cases of childhood cataract. On a secondary level, the primary objective is to improve or maintain vision through the use of vision aids, including spectacle and contact lens correction as appropriated. The ophthalmologist in charge should be able to make a full diagnosis and arrange surgery at a tertiary centre that provides specialised ophthalmic care for childhood cataract surgery. Parents should be involved in the management of childhood cataracts. Tertiary care services should include the availability of a trained paediatric ophthalmologist who is well versed with the management of childhood cataracts. Other key people in the management of childhood cataract include an optometrist, anaesthetist and a paediatrician. Finally, centres providing surgical services must be properly equipped and staffed.

7 Int Ophthalmol (2015) 35: Acknowledgments Grant number: CG None of the authors have any proprietary interests or conflicts of interest related to this submission. This submission has not been published anywhere previously and that it is not simultaneously being considered for any other publication. References 1. World Health Organization. Global initiative for the elimination of avoidable blindness. Geneva: WHO, (WHO/PBL/97.61.) 2. World Health Organization. Preventing blindness in children: report of WHO/IAPB scientific meeting. Geneva: WHO, (WHO/PBL/00.77.) 3. Gilbert CE, Anderton L, Dandona L et al (1999) Prevalence of blindness and visual impairment in children a review of available data. Ophthalmic Epidemiol 6: World Bank. World development report 1993: investing in health. Oxford University Press, New York 5. Gilbert C, Rahi J, Quinn G (2003) Visual impairment and blindness in children. In: Johnson G, Minassian D, Weale W, West S (eds) Epidemiology of eye disease, 2nd edn. Arnold, London 6. Gilbert C, Rahi J, Eckstein M, O Sullivan J, Foster A (1997) Retinopathy of prematurity in middle-income countries. Lancet 350: Alagaratnam J, Sharma TK, Lim CS et al (2002) A survey of visual impairment in children attending the Royal Blind School, Edinburgh using the WHO childhood visual impairment database. Eye (Lond) 16(5): Dorairaj SK, Bandrakalli P, Shetty CRV, Misquity D, Ritch R (2008) Childhood blindness in a rural population of southern India: prevalence and etiology. Ophthalmic Epidemiol 15: Dandona R, Dandona L (2003) Childhood blindness in India: a population based perspective. Br J Ophthalmol 87: Patel DK, Tajunisah I, Gilbert C, Subrayan V (2011) Childhood blindness and severe visual impairment in Malaysia: a nationwide study. Eye (Lond) 25(4): Gilbert C, Foster A, Negrel AD, Thylefors B (1993) Childhood blindness: a new form for recording causes of visual loss in children. Bull World Health Organ 71(5): Accessed 11 May Sitorus R, Preising M, Lorenz B (2003) Causes of blindness at the Wiyata Guna school for the blind. Indonesia Br J Ophthalmol 87(9): Ezegwui IR, Umeh RE, Ezepue UF (2003) Causes of childhood blindness: results from schools for the blind in south eastern Nigeria. Br J Ophthalmol 87(1): Kello AB, Gilbert CE (2003) Causes of severe visual impairment and blindness in children in schools for the blind in Ethiopia. Br J Ophthalmol 87(5): Hornby SJ, Xiao Y, Gilbert CE et al (1999) Causes of childhood blindness in the People s Republic of China: results from 1131 blind school students in 18 provinces. Br J Ophthalmol 83: Muhit MA, Shah SP, Gilbert CE et al (2007) Causes of severe visual impairment and blindness in Bangladesh: a study of 1935 children. Br J Ophthalmol 91(8): Rahi JS, Cable N, on behalf of the British Childhood Visual Impairment Study Group (2003) Severe visual impairment and blindness in children in the UK. Lancet 362(9393): Reddy SC, Tan BC (2001) Causes of childhood blindness in Malaysia: results from a national study of blind school students. Int Ophthalmol 24: Gilbert C, Fielder A, Gordillo L et al (2005) Characteristics of infants with severe retinopathy of prematurity in countries with low, moderate, and high levels of development: implications for screening programs. Pediatrics 115:e518 e Clinical practice guidelines of Malaysia for Retinopathy of Maturity. Dec 2005 MOH/P/PAK/103.05(GU) 22. Section on Ophthalmology (2006) American Academy of Pediatrics, American Academy of Ophthalmology and American Association for Pediatric Ophthalmology and Strabismus Screening examination of premature infants for retinopathy of prematurity. Pediatrics 117: Chen Y, Li X (2006) Characteristics of severe retinopathy of prematurity patients in China: a repeat of the first epidemic. Br J Ophthalmol 90: Wilson ME, Pandey SK, Thakur J (2003) Paediatric cataract blindness in the developing world: surgical techniques and intraocular lenses in the new millennium. Br J Ophthalmol 87: Gilbert C, Foster A (2001) Childhood blindness in the context of vision 2020 the right to sight. Bull World Health Organ 79: Foster A, Gilbert C (1992) Epidemiology of childhood blindness. Eye 6: Gilbert CE, Wood M, Waddel K et al (1995) Causes of childhood blindness in east Africa: results in 491 pupils attending 17 schools for the blind in Malawi, Kenya and Uganda. Ophthalmic Epidemiol 2(2): Schwab L, Kagame K (1993) Blindness in Africa: Zimbabwe schools for the blind survey. Br J Ophthalmol 77(7): Ahmed F (1999) Vitamin A deficiency in Bangladesh: a review and recommendations for improvement. Public Health Nutr 2(1): Integration of vitamin A supplementation with immunization: policy and programme implications. Report of a meeting, Jan 1998, UNICEF, New York. Geneva, World Health Organization, 1998 (WHO/EPI/GEN/98.07)