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Year : 2000  |  Volume : 48  |  Issue : 3  |  Page : 195-200

Evaluation of children in six blind schools of Andhra Pradesh

International Centre for Eye Health, Institute of Ophthalmology, London, UK

Correspondence Address:
S J Hornby
International Centre for Eye Health, Institute of Ophthalmology, London, UK

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Source of Support: None, Conflict of Interest: None

PMID: 11217250

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Purpose: 1.To determine the anatomical site and underlying causes of severe visual impairment and blindness in children in special education in Andhra Pradesh, India. 2. To compare the causes of blindness in two different regions in the state. 3. To evaluate improvement with correction of refractive error and low-vision devices (LVDs)
Methods: Children in 6 schools for the blind and in 3 integrated education programmes were examined by one ophthalmologist, and were refracted and assessed for LVDs by an optometrist. The major anatomical site and underlying aetiology of severe visual impairment and blindness (SVI/BL; <6/60 in the better eye) were recorded using the standardised WHO reporting form.
Results: Two hundred and ninety one students under 16 years were examined, and after refraction, 267 (91.7%) were classified as being severely visually impaired or blind. The most common anatomical sites of SVI/BL were retina in 31.1% children; cornea in 24.3%; and whole globe in 20.2%. The aetiology was unknown in 38.2%, hereditary in 34.8% and childhood causes in 24%. 114 children (39.2%) had functional low vision (i.e. visual acuity <6/18 to light perception with navigational vision). In this group, 36 children improved with spectacles and 16 benefited by LVDs. 41 children (15.4%) were able to read N10 point though they were studying Braille.
Conclusion: Overall 37.4% of children had "avoidable" causes of blindness. The major avoidable causes were vitamin-A deficiency and cataract. Vitamin-A deficiency and congenital anomalies were more common in the dry plateau areas of the state. One in seven children could read normal print with optical support.

Keywords: Adolescent, Blindness, diagnosis, epidemiology, etiology, Child, Humans, India, epidemiology, Prevalence, Research Support, Non-U.S. Gov′t,

How to cite this article:
Hornby S J, Adolph S, Gothwal V K, Gilbert C E, Dandona L, Foster A. Evaluation of children in six blind schools of Andhra Pradesh. Indian J Ophthalmol 2000;48:195-200

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Hornby S J, Adolph S, Gothwal V K, Gilbert C E, Dandona L, Foster A. Evaluation of children in six blind schools of Andhra Pradesh. Indian J Ophthalmol [serial online] 2000 [cited 2023 Sep 27];48:195-200. Available from: https://journals.lww.com/ijo/pages/default.aspx/text.asp?2000/48/3/195/14875

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The prevalence of blindness in children aged 0-15 years has been estimated to be 0.65 per thousand children in Andhra Pradesh (data from community-based rehabilitation programme as part of comprehensive eye care (CBR/CEC).[1] Information on the major causes of blindness in children is required to design effective prevention of blindness programmes.[2] In a previous study of blind schools, which included 1, 318 pupils in nine states of India, the major causes of blindness in children were corneal scarring in 26.4% (mainly due to vitamin-A deficiency), congenital globe anomalies in 20.7% (mainly microphthalmos), and retinal disease in 19.3% (mainly dystrophies).[3] The study showed marked regional variation in the major causes of blindness in children among the nine states.[3] The study did not include Andhra Pradesh. A CBR/CEC programme in the rural population of West Godavari district of coastal Andhra Pradesh found a low proportion of childhood blindness due to vitamin-A deficiency (5.5%), while the major causes of visual loss were congenital globe anomalies (25%) and retinal diseases (22.2%).[1]

The blind school study reported in this communication, and the CBR/CEC programme in Andhra Pradesh, both used standard WHO definitions of childhood (0-15 years) and blindness (<3/60 in the better eye). Low vision was originally defined by WHO as a visual acuity of <6/18 - 3/60 in the better eye. However, many children who have a corrected visual acuity in the better eye of less than 3/60 (i.e. those who are categorised as blind) have useful residual vision and may benefit from low-vision services. Therefore, a revised "working definition" of low vision was agreed upon at a WHO consultation meeting on the Management of Low Vision in Children in 1992.[4] This new definition is visual acuity less than 6/18 to light perception, provided the child has functional vision, e.g., for navigation. Near vision is not part of the standard WHO definition of blindness but is included in the revised definition. Children have a larger range of accommodation than adults and frequently have much better near than distance vision. This has important implications for education.

Andhra Pradesh is the fifth largest Indian State (population approximately 75 million) and no blind school data are currently available. Geographically it consists of the semi-arid Deccan plateau, and a fertile coastal plain irrigated by the Krishna and Godavari rivers. Approximately 39 special schools for the blind exist in Andhra Pradesh, and although the total number of children studying in these institutions is not known it is likely to exceed 2000. The present study of children in schools for the blind was part of a larger study of congenital anomalies of the eye and was restricted geographically to four districts of the state. Previous studies of SVI/BL in children in India have not investigated the proportion of children with low vision according to the revised definition, nor have they included assessment for low-vision devices (LVDs).

The study aimed

  1. 1. to determine the anatomical site and underlying causes of severe visual impairment and blindness in children under 16 years of age in blind schools and integrated education in Andhra Pradesh, India

  2. 2. to compare causes of SVI/BL between the dry Deccan region and the fertile coastal region of Andhra Pradesh; and

  3. 3. to assess the needs of these children for spectacles and LVDs.

  Materials and Methods Top

Schools were identified from various local sources, and permission for the study was obtained from the Principal of each school. All schools for the blind and schools with integrated education in four selected districts (Hyderabad, Rangareddy, West Godavari and Krishna district) were included. Children were examined by an ophthalmologist and an optometrist on school premises. Demographic details and a brief medical and family history were recorded. If two affected siblings were present in the same school they were examined together. A child is defined by UNICEF as an individual less than 16 years old. However, this criterion has not been used as a standard in all studies.

Childhood blindness is defined as best corrected visual acuity in the better eye of less than 3/60 and severe visual impairment is less than 6/60. The WHO categories of visual impairment (monocular visual acuity in the better seeing eye) are shown in [Table - 1]. Visual acuity was assessed in each eye using a "E" tumbling visual acuity test chart. Patients who were unable to cooperate with the "E" chart, were assessed the ability to fix and follow a light. The visual status of children was recorded using WHO categories of visual impairment before and after refraction. Near vision was assessed using a chart with logmar discontinuous text in English. Those children unfamiliar with the English alphabet were asked to copy the shape of a particular letter. N10 was chosen as a cutoff, as this is equivalent to the size of print used in books for primary level education in India.

All children were refracted by an optometrist. A single test of functional vision was used to decide if the child was in the low vision category, defined as the ability to navigate around two chairs by vision alone with a visual acuity of <6/18 to light perception. Those children who were not able to cooperate with these tests due to additional handicaps were judged on their visual behaviour.

Children with "low vision" were assessed for LVDs for near vision by the optometrist. The exceptions were those who were mentally handicapped and those who were able to read N10 unaided. A trial set of stand magnifiers of increasing strength was used for assessment. Stand magnifiers up to a power of +24 Diopters (Lensel Optics, Pune, India) and a variety of hand magnifiers (up to +12.00 Diopters) are available at low cost in India, but higher power magnifiers and telescopes had to be imported from the UK. Children were assessed using the normal illumination available in the schools.

Anterior segments of the eye were examined using a light and loupe magnifier and a hand-held slitlamp. The posterior segment was examined using direct and indirect ophthalmoscope after dilatation of the pupil. The major anatomical site of visual loss and major aetiology were recorded on a proforma based on the WHO/PBL reporting form.[5] Data were later entered into a database in EPI-INFO.[6] The anatomical classification of causes of visual loss defines that part of the eye which has been damaged leading to visual loss (e.g. cornea, lens, retina, optic nerve, whole globe). Where two or more anatomical sites were involved the major site was selected, or where two sites contributed equally the most treatable condition was selected. The aetiological classification was divided into five categories depending on the time of onset of the condition leading to blindness (hereditary, intrauterine, perinatal, childhood and unknown).

  Results Top

A total of 291 students under 16 years were examined in six schools for the blind (275) and three integrated schools (16) in four districts of Andhra Pradesh. Two districts (Hyderabad and Rangareddy districts, 169 children) are situated in the dry Deccan plateau region, and two districts (West Godavari and Krishna districts, 98 children) are in the fertile coastal region. All schools were located in urban areas, but children came from both rural and urban areas to the schools. In the age group of 5-15 years (mean 11.6 years) there were 168 (62.9%) boys and 99 (37.1%) girls. The majority of children (88.4%) had no disability apart from blindness. After refraction 267 children (91.7%) were categorised to having SVI/BL according to WHO criteria [Table - 1]. Using the revised working definition of low vision, 114 children (39.2%) had functional low vision and were assessed for LVDs. Of the remainder, 68 children (23.4%) had no light perception, and 107 had light perception without navigational (functional) vision (36.8%) [Table - 1].

  Anatomical causes of visual loss Top

The anatomical causes of visual loss are shown in [Table - 2]. Retinal disorders were responsible for SVI/ BL in 83 children (31.1%), of which 76 had retinal dystrophies or albinism (28.5% of all cases). Corneal diseases (including those leading to phthisis bulbi following corneal perforation) caused SVI/BL in 65 children (24.3%). The majority of these were attributed to vitamin-A deficiency (42) or measles infection (9). Abnormalities of the whole globe was found in 54 children (20.2%) of which congenital anomalies (microphthalmos and anophthalmos) were responsible for 44 (16.5% of all cases). Disorders of the lens were responsible for 21 cases (7.9%), of which 11 children had unoperated cataract and 10 were aphakic and/or amblyopic following cataract surgery. Uveal disorders were seen in 9 cases (3.4%): coloboma (4), aniridia (1) and uveitis (4). Optic nerve disorders was detected in 13 cases (4.9% all optic atrophy). Childhood glaucoma was responsible for 18 cases (6.7%). Other causes included cortical blindness in 3 cases and one child could not be examined. Unknown causes affecting the whole globe (phthisis bulbi 8, disorganised globe 2) accounted for a further 3.7% of SVI/BL.

Results from the two geographical areas showed that the dry Deccan plateau had a higher proportion of corneal disease (28.4%) than the fertile coastal region (17.3%) and also a higher proportion of congenital abnormalities of the globe (23.1% versus 15.3%). The coastal area had a higher proportion of retinal disease (42.9%) compared with (24.3%) in the Deccan area.

  Aetiology of visual loss Top

The aetiology of SVI / BL, classified according to the time of known insult resulting in visual loss, is shown in [Table - 3]. Hereditary factors were identified in 93 cases (34.8%), in which there was a positive family history of another similarly affected individual in 78 (29.2%). There was an undetermined mode of inheritance in 52 children; 37 had presumed autosomal recessive disease; and 4 had autosomal dominant disease. Intrauterine factors were identified in one case (toxoplasmosis), and perinatal factors in 7 cases (2.6%). In 64 cases (24%) childhood factors were the cause of visual loss and in the remainder (38.2%) the aetiology was undetermined.

The coastal area had a higher proportion of blindness attributable to hereditary factors (46.9%) than the Deccan region (27.8%), while the Deccan region had a higher proportion of childhood factors (27.8%; mainly vitamin-A deficiency) compared with 17.4% in the coastal area.

  Avoidable causes Top

Overall 35.9% of children had potentially "avoidable" causes of blindness: preventable causes (19.8%) and treatable causes (16.1%). Vitamin-A deficiency was the major preventable cause of visual loss, and cataract and glaucoma were the main treatable causes [Table - 4].

  Requirements for spectacles Top

The need for optical services was assessed in all 291 children. Only 10 children (3.4%) were wearing spectacles at the time of examination. After refraction, 36 children improved visual acuity in their better eye with spectacles (12.4%). After refraction, 21 children (7.2%) improved by at least one WHO category. All children who required spectacles were in the low-vision category. The major anatomical sites for visual loss in children who benefited from spectacles are shown in the Figure.

  Requirements for low vision devices Top

Of the 114 children with functional low vision, 41 were able to read N10, of which 16 required LVDs and 25 could read N10 unaided or with their distance spectacle correction. No child had a low vision device prior to the study. The types of magnifiers prescribed were as follows: 3 hand-held magnifiers, 6 spectacle magnifiers and 7 stand magnifiers. The diagnoses of the children who were given magnifiers were aphakia (6), microphthalmos/coloboma (4), retinal dystrophy/ albinism (3) and others (3). All 6-stand magnifiers prescribed were high power (40-60D) and had to be imported, others were available locally and met approximately two thirds of the need.

  Discussion Top

With a population of approximately 75 million of which 35% are children under 16, and a prevalence of childhood blindness of 0.65 per thousand, the number of blind children in Andhra Pradesh is estimated about 17,000. However, the present study was limited geographically and was not necessarily representative of all schools for the blind in the State. There are some biases inherent in any study of children in schools for the blind. For example, children with multiple disabilities, pre-school age children, those who have died, those from lower socio-economic groups, and those from rural communities are likely to be under-represented in schools for the blind compared with population-based studies. However, for low prevalence conditions such as blindness in children population-based studies would have to be very large and therefore would be time consuming and expensive to perform. The advantages of blind school studies are that they are cheaper and quicker to perform and they can use a single observer. The results give an idea of the relative importance of different causes of blindness in children in a particular region but do not give information on the cause-specific prevalence in that population.

Amongst children attending blind schools corneal blindness was the second most common cause of SVI/ BL (24.3%) and the major preventable cause identified. Different infectious causes of corneal blindness (such as ophthalmia neonatorum) were difficult to distinguish in the end stage and without a good history. However, vitamin-A deficiency (VAD) is likely to have been an important contributing factor in many cases leading to keratomalacia. As VAD is associated with a high mortality rate, the children in schools for the blind represent only the survivors of a much larger problem. VAD is known to vary markedly between regions.[7] It is not surprising, therefore, that the more fertile coastal area of Andhra Pradesh should have a lower proportion of corneal blindness than the drier Deccan plateau. A history of measles infection was found in some cases of corneal blindness and this would be preventable by immunisation.

Retinal dystrophies (including albinism) were identified as the most common single cause of SVI/BL in this study, accounting for 26.1%. This high proportion is similar to that found by Rani et al in the neighbouring southern states of Karnataka (23.7%) and Tamil Nadu (25.5%) and higher than the neighbouring northern states of Madhya Pradesh (11.9%) and Maharastra (13.8%).[3] A higher proportion of retinal disease was found in the blind schools (31.1%) than in the community-based rehabilitation programme in Andhra Pradesh (22.1%).[1] Retinal dystrophies were also the most common cause of visual impairment in a hospital-based series of children assessed for low-vision aids in Hyderabad (personal communication, V.K. Gothwal).

Congenital abnormalities of the globe (microphthalmos, anophthalmos and coloboma) were responsible for 18% of SVI/BL. This is similar to the results of the blind school study in Madhya Pradesh (18.8%) but lower than the proportion in Karnataka (28.7%) and Tamil Nadu (20.6%). Congenital anomalies may be due to genetic disease or intrauterine factors but in the majority the aetiology is unknown. It is interesting to observe the association between VAD and congenital anomalies, including microphthalmos, which was also observed by Rahi.[7]

Other causes of SVI/BL, which require specialist ophthalmic interventions, were buphthalmos/glaucoma (6.7%) and cataract/aphakia (7.9%). The proportion of disease attributed to genetic factors in this study (34.8%) is higher than the mean for blind schools in India (23%).[8] The high proportion of genetic disease is likely to be related to the common practice of consanguineous marriage in Andhra Pradesh. A study in Srikakulam district of Andhra Pradesh in 1988 found that 33.8% of marriages were consanguineous.[9] Consanguinity has also been implicated as a risk factor for congenital anomalies of the globe.[10] Health education and genetic counselling have been shown to be effective in preventing recessive diseases such as thalassaemia in some populations, and is non-invasive and relatively inexpensive.[11] However, a WHO expert group has concluded that an attempt to discourage consanguineous marriage on genetic grounds might do more harm than good.[12]

The presence of a large proportion of children with visual loss of unknown aetiology is consistent with results from other studies using similar methods and reflects the limited investigations available and the lack of examination of family members in many cases. For example, congenital cataracts may have many different aetiologies and in the absence of a positive family history or signs consistent with congenitally acquired rubella syndrome they were classified as being of unknown aetiology.

A single test of navigational vision was used to identify those children with low vision who might benefit from spectacles and LVDs. There were 36 (31.6%) children with functional low vision who improved with spectacles correction. Those with aphakia, microphthalmos, coloboma and albinism were most likely to benefit from spectacles. A study of the need for low vision services in blind school students in East Africa provides a comparison with India.[13] In that study 63.9% of African blind school students had functional low vision and 46% could read N5-N8 print unaided or with spectacles, a further 33% could read N5-NS with LVDs. However, in Andhra Pradesh the proportion of students with functional low vision was lower (39.2%) and a lower proportion could read N10 print or better with spectacles (31.6% of the low vision group) or LVDs (18%).

In conclusion, the ophthalmologists must be made aware of the potential value of spectacles and low vision devices in the "incurably blind child". The present study demonstrates the need for ophthalmic evaluation, refraction and assessment for low vision devices prior to admission to schools for the blind because 24 (8.2%) were classified as not blind, or severely visually impaired after refraction and another 16.1% had potentially treatable disease. Integrated education has been initiated, in the state but the number of children integrated is still low. An alternative would be to encourage low-vision classes with print education in the blind schools alongside Braille classes, but this would require investment in teaching materials.

  Acknowledgements Top

Md. Ferozuddin and S.M. Farhath were invaluable in planning and coordination. We are grateful for the cooperation of the participating teachers and pupils.

  References Top

Dandona L, Williams JD, Williams BC, Rao GN. Population-based assessment of childhood blindness in southern India. Arch Ophthalmol 1998;116:545-46.  Back to cited text no. 1
Dandona L, Gilbert CE, Rahi JS, Rao GN. Planning to reduce childhood blindness in India. Indian J Ophthalmol 1998;46:117-22.  Back to cited text no. 2
Rahi JS, Gilbert CE, Foster A. Childhood blindness in India: causes in 1318 blind school students in nine states. Eye 1995;9:545-50.  Back to cited text no. 3
WHO. The management of low vision of childhood. Proceedings of the WHO/PBL Consultation. Bangkok July 1992. Geneva: WHO, 1993.  Back to cited text no. 4
Gilbert C, Foster A, Negrel AD, Thylefors B. Childhood blindness: a new form for recording causes of visual loss in children. Bull World Health Organ 1993;71:485-89.  Back to cited text no. 5
Dean AG, Dean JA, Coulombier D, Brendel KA, Smith DC, Burton A, et al. Epi Info, Version 6: A word processing, databse, and statistics program for epidemiology on microcomputers. (6.04). 1994. Atlanta Georgia, Centers for Disease Control and Prevention (CDC).  Back to cited text no. 6
Rahi JS, Sripathi S, Gilbert CE, Foster A. Childhood blindness due to vitamin A deficiency in India: Regional variations. Arch Dis Child 1995;72:330-33.  Back to cited text no. 7
Rahi JS, Sripathi S, Gilbert CE, Foster A. The importance of prenatal factors in childhood blindness in India. Developmental Medicine & Child Neurology 1997;39:449-55.  Back to cited text no. 8
Rao BD, Busi BR. Inbreeding among endogamous groups in three multicaste villages of Srikakulam District, Andhra Pradesh, India. Soc Bid 1988;35:331-36.  Back to cited text no. 9
Fujiki K, Nakajima A, Yasuda N, Tanabe U, Kabasawa K. Genetic analysis of microphthalmos. Ophthalmic Paediatrics and Genetics 1992;1:139-49.  Back to cited text no. 10
Cao A, Rosatelli MC, Galanello R. Control of beta-thalassaemia by carrier screening, genetic counselling and prenatal diagnosis; The Sardinian experience. Ciba Found Symp l996;197:137-51.  Back to cited text no. 11
Report of WHO Advisory Group on Hereditary Diseases. 1985. Document HMG/WG/85.8a.  Back to cited text no. 12
Silver J, Gilbert CE, Spoerer P, Foster A. Low vision in east African blind school students: Need for optical low vision services. Br J Ophthalmol 1995;79:814-20.  Back to cited text no. 13


  [Figure - 1]

  [Table - 1], [Table - 2], [Table - 3], [Table - 4]

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