|Year : 2012 | Volume
| Issue : 2 | Page : 163-167
Visual impairment in urban school children of low-income families in Kolkata, India
Sambuddha Ghosh1, Udayaditya Mukhopadhyay1, Dipankar Maji2, Gautam Bhaduri3
1 Assistant Professor, Regional Institute of Ophthalmology, Kolkata, India
2 DADHS (Public Health), Government of West Bengal, Swasthya Bhawan, Kolkata, India
3 Professor & Director, Regional Institute of Ophthalmology, Kolkata, India
|Date of Web Publication||21-Aug-2012|
Assistant Professor, Regional Institute of Ophthalmology, BB41/8, Salt Lake City, Kolkata - 700064
Source of Support: None, Conflict of Interest: None
| Abstract|| |
To evaluate pattern of visual impairment in school children from low-income families in Kolkata, India, an institutional cross-sectional study was conducted among 2570 children of 10 primary schools. Ocular examination including refraction was done and pattern of visual impairment and refractive error was studied. The age range was 6-14 years. Refractive error was seen in 14.7%. Only 4 children were already wearing correction. Myopia and hypermetropia was present in 307 (11.9%) and 65 (2.5%) children, respectively. Visual acuity of less than 6/12 in better eye was present in 109 (4.2%) and 5 (0.2%) children pre- and post-correction, respectively. Eighteen children had amblyopia. Although prevalence of refractive error in this group is less compared to school children of all income categories reported from other cities of India, it is more compared to school children of all income categories from the same city. Refractive error mostly remains uncorrected in this group.
Keywords: Child, Low-income population, Refractive error
|How to cite this article:|
Ghosh S, Mukhopadhyay U, Maji D, Bhaduri G. Visual impairment in urban school children of low-income families in Kolkata, India. Indian J Public Health 2012;56:163-7
|How to cite this URL:|
Ghosh S, Mukhopadhyay U, Maji D, Bhaduri G. Visual impairment in urban school children of low-income families in Kolkata, India. Indian J Public Health [serial online] 2012 [cited 2019 Sep 20];56:163-7. Available from: http://www.ijph.in/text.asp?2012/56/2/163/99919
The prevalence of childhood blindness in India is 0.17%.  Treatable refractive error is the major cause (33.3%) of the blindness in children, followed by preventable causes (16.6%) like vitamin A deficiency and post cataract surgery amblyopia.  Presence of uncorrected refractive error in children can lead to amblyopia. The presence of refractive error in school-going children affects their physical, mental and behavioral development as well.  Uncorrected refractive error is a major public health problem in urban school-aged children in India. 
Significantly low utilization of eye-care services relative to recommended guidelines is observed in low-income populations. They have poor access to eye and vision care and are more likely to experience adverse outcomes. , It was observed that children from lower socio-economic status groups were less likely to see an eye-care specialist or to avail screening services.  School eye screening (SES) program was initiated under National Program for Control of Blindness (NPCB) in 1994. The activities in SES include identification of schools, collection of data regarding students, training of teachers, screening of students by ophthalmic assistants/ophthalmologists, prescription of correcting lens, providing free spectacle to children from poor socioeconomic strata and referring the patients to an appropriate center if further management is needed.  SES may help us to reach children from low-income families who otherwise have poor access to vision care. In 2008-09, a total of 992085 school children were screened in West Bengal under SES. Of them, 30894 (3.1%) children had refractive error. Free spectacle was supplied to 10589 (34.3%) children with refractive error. 
These data do not reflect the particular need, if any, of a special group of children coming from low-income families. Data on the pattern of eye health problems in children from low-income families is necessary for planning any need-based program for them. No such data are available from this part of India. Our aim was to determine the pattern of eye health problems in special group like primary school children belonging to families living below poverty line in Kolkata, India, in order to provide the health managers with data for taking need-based action.
Our study was a cross-sectional survey with cluster sampling design, where the clusters were primary schools (class one to four). Assuming a 4% prevalence of refractive error in children  and considering a rate of homogeneity of 0.02, the required sample size for a precision of ±2% and a confidence interval of 95% was estimated to be 2000. The cluster size was 200. So the sample subjects were supposed to be obtained randomly from 2000/200 i.e., 10 clusters. Ten primary schools in the city of Kolkata were selected using probability proportionate to size method, out of a sampling frame of the government-funded primary schools in the city. However, schools with any slum situated within half a kilometer radius were only included in the sampling frame. Low economic status of the students was determined, in accordance with the School Eye Screening (SES) Program norm, on the basis of certification from respective heads of the institutions with reference to either Below Poverty Line (BPL) family card or family number in BPL list. A team of an ophthalmologist and two ophthalmic technicians from Regional Institute of Ophthalmology (RIO), Kolkata, went to the selected schools during the period of March 2008 to June 2009 and examined all the available children , beyond the cluster size of 200, as a part of the SES. The age of children was recorded as per school registrar. History of present and past ocular problems and treatment, and family history were obtained. The clinical examination was done by the ophthalmologist. Anterior segment of the eye was examined with torch light. Retinal examination was performed with the help of direct ophthalmoscope after dilating the pupil. The refraction was done by the ophthalmic technicians. Assessment of visual acuity for distance was done with Snellen chart and was recorded as the smallest line read with one or no errors at class room illumination, unaided (uncorrected visual acuity) as well as with spectacles (presenting visual acuity), if the child brought them. In all children with visual acuity of less than 6/6, cycloplegic refraction was performed with streak retinoscope, followed by subjective refraction on a separate occasion, till the best corrected visual acuity was achieved. Myopia was diagnosed if one or both eyes were myopic; hypermetropia if one or both eyes were hypermetropic, so long as neither eye was myopic; and emmetropia if neither eye was myopic or hypermetropic. In absence of any apparent organic lesion, bilateral amblyopia was diagnosed in eyes with best corrected visual acuity of less than 6/18 in both eyes and unilateral amblyopia was diagnosed when difference in best corrected visual acuity between two eyes was of two Snellen's lines or more. 
For all the refractive errors, except myopia >6.00 D and hypermetropia <0.5 D, glasses were prescribed. Treatment of minor eye ailments and corrective spectacles were provided at the school free of charges. Children with myopia >6.00 D or any other ocular problem were referred to the RIO, Kolkata, for further management. Data were entered into a Microsoft Excel spreadsheet and analyzed using Epitable software (version 6.04). The study was permitted by Institutional ethics committee.
The 10 schools were situated in 10 different wards of Kolkata. Total number of children examined was 2732. Among them, 2570 children belonged to low-income families. Out of those 2570 children, 1392 (54.2%) were female and 1178 (45.8%) were male. Religion-wise, 2098 (81.64%) were Hindu and 472 (18.36%) were Muslim. Age range was 6 to 14 years, median age being 11 years. Age range of both myopia and hypermetropia was 6-14 years.
Visual acuity of 6/6 in both eyes was found in 2193 (85.3%; 95% CI 84.0 to 86.7%) children; 997 (45.5%) of them were male and 1196 (54.5%) were female. Visual acuity of less than 6/6 at least in one eye was present in 377 (14.7%; 95% CI 13.3 to 16.1%) children; 181 (48%) of them were male and 196 (52%) female with no significant difference (P = 0.359). Out of these 377 children, visual acuity improved with correction in 372 children; vision did not improve in 5 children.
Loss of visual acuity was due to only refractive errors in 356 children, amblyopia with or without refractive error in 18, nystagmus in 2 and phthisis bulbi in 1.
Visual acuity of less than 6/12 in better eye was seen in 109 (4.2%; 95% CI 3.4 to 5.0%) and 5 (0.2%; 95% CI 0.02 to 0.36%) children before and after correction, respectively [Figure 1], the improvement being significant at 1% significance level. Visual acuity of less than 6/12 was observed in 247 (4.8%) eyes, 116 (4.9%, 95% CI 4.1-5.8) eyes in boys and 131 (4.7%, CI 3.9-5.5) eyes in girls. It was significantly more in girls when tested by Chi-square (P = 0.0027). The median age for eyes with visual acuity of less than 6/12 was 11 years. There was no significant difference in prevalence (P = 0.535) between either side of median age.
|Figure 1: Children having visual acuity <6/12 before and after correction (n = 109), representing number of children along y axis and visual acuity along x axis|
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There was significant difference (P = 0.043) between Muslim [29 (3.1%, 95% CI 2.0 to 4.2)] and Hindu children [84 (2.0%, 95% CI 1.6 to 2.4)] when they were compared by Chi square test by eyes with visual acuity of less than 6/18. There was no significant difference (P = 0.52) in male and female when compared similarly.
Before correction, 48 (1.9%; 95% CI 1.3 to 2.4%) children had low vision (visual acuity <6/18 but >3/60 in better eye). After correction only 2 children (0.08%; 95% CI 0 to 0.19%) had low vision (P < 0.001). Before correction, 108 out of 5140 (2.1%; 95% CI 2.5 to 1.7%) eyes had visual acuity of <6/18 but >3/60; and 5 out of 5140 (0.1%; 95% CI 0.18 to 0.01%) had visual acuity of ≤3/60. After correction only two eyes had visual acuity <6/18 but >3/60 (P < 0.001). However, 3 eyes remained with visual acuity of <3/60 even after correction. Before correction, 5 children (0.19%; 95% CI 0.02 to 0.36%) had visual acuity <6/60 in better eye that reduced to 2 children (0.08%; 95% CI 0 to 0.19%) after correction.
Out of 2570 children, 307 (11.9%; 95% CI 10.6 to 13.2%) were myopic and 65 (2.5%; 95% CI 1.9 to 3.1%) were hypermetropic. Similarity in distribution of myopia and hypermetropia in different age-groups was observed [Figure 2]. Age-groups having high prevalence of myopia had high prevalence of hypermetropia also (Spearman's rank correlation coefficient = 0.6905).
|Figure 2: Proportion of children having refractive error by age groups (n = 2570) representing age in years along x axis|
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A total of 4422 (85.8%, 95% CI 84.9 to 86.8%) out of 5139 eyes were emmetropic, one eye had phthisis bulbi]. 370 (7.2%; 95% CI 6.5 to 7.9%) eyes had simple myopia, equally distributed between male and female. 104 eyes had simple hypermetropia (62 in male and 42 in female; P = 0.004). Two hundred and eight eyes had simple myopic astigmatism (128 in female and 80 in male; P = 0.030). 26 eyes had simple hypermetropic astigmatism (12 in female and 14 in male; P = 0.41). 10 eyes had compound myopia and no eye had compound hypermetropia.
Out of 370 eyes with simple myopia, 320 (86.5%; 95% CI 82.9 to 90.0%) needed corrections less than 2Dsp, 49 (13.2%; 95% CI 9.7 to 16.8%) between 2 and 4 Dsp and only one eye needed more than 4 Dsp correction. Out of 208 eyes with simple myopic astigmatism, 201 eyes (96.6%; 95% CI 94.1 to 99.1%) were corrected by less than 2 Dcyl, 7 needed 2-4 Dcyl and none above 4 Dcyl. Out of 104 eyes with simple hypermetropia, 102 (98.1%; 95% CI 95.4 to 100%) needed correction below 2 Dsp and two eyes needed 2-4 Dsp correction. Out of 26 eyes with simple hypermetropic astigmatism, all were corrected by less than 2 Dcyl.
We observed amblyopia in 29 eyes (18 children, 11 having bilateral amblyopia and 7 having unilateral amblyopia). All the 11 cases of bilateral amblyopia were due to uncorrected refractive error. Out of 7 cases of unilateral amblyopia, 5 were due to uncorrected anisometropia and 2 cases were due to uncorrected tropia. Out of 18 children with amblyopia, 10 were Muslim which was significantly (P = 0.0002) more compared to Hindu (n = 8) when tested by Chi-square test. There was no significant difference (P = 0.553) between female (n = 11) and male (n = 7) children.
Out of 372 children who had refractive error amenable to correction, only 4 children (1.1%; 95% CI 0.02 to 2.2%) were already wearing correction. All these 4 were female Hindu; 2 of them aged 10 years and the other 2 aged 12 years.
In our study population 14.7% children had refractive error. A prevalence of 25.7% among urban and 8% among rural school children was reported from South Indian city of Hyderabad.  An estimated 25.4% of the children between 6 and 18 years wear corrective lenses in USA.  The prevalence of refractive error in our study was less. It was midway between the values in urban and rural children as reported from Hyderabad. However in a previous study from Kolkata, refractive error was reported in only 4.03% students.  The report of Government of West Bengal on SES also shows low prevalence of refractive error in school children of West Bengal.  In our study, myopia (11.9%) was 4.8 times more prevalent than hypermetropia (2.5%). A population-based study in South India with rural children with age range 7-15 years also revealed 5 times higher prevalence of myopia compared to hypermetropia.  However in another study from South India, higher prevalence of hypermetropia was reported.  But that study population comprised of children starting from 3 years of age. This probably explains the higher incidence of hypermetropia in that study. Higher incidence of myopia in urban children (51.4%) compared to rural children (16.7%) was reported from South India.  In our study, visual acuity of less than 6/12 in better eye was seen in 109 (4.2%). This is much less than compared to 9.8% reported from South India.  Low rate (2.7%) of existing spectacle use among ametropic urban school children has been reported in New Delhi.  In our study, ametropic children already using spectacle was even lower (1.1%). Low income of family and associated lack of awareness are probable reasons for such a high rate of non-users of spectacle. Although spectacle use was low, the prevalence of amblyopia in our study (0.7%) was less compared to report from South India (1.1%). 
We observed female preponderance in minor grade loss of visual acuity (<6/12), but not in major grades (<6/18). However all the spectacle users were also female. Significant difference in prevalence of amblyopia in Muslims compared to Hindus refers to greater need of awareness generation among low-income Muslim community in particular.
We could not compare our observation with other data from same category of children due to paucity of such data. However as the SES program is directed to children from all income categories, we tried to see if there is any difference between this special group from low income and children from all income categories. Our study results indicate that refractive error in urban school children from low-income families in Kolkata is less compared to school children of all income categories reported from other parts of the country. However it is more compared to school children of all income categories from the same city. It was also evident from this study that although refractive error was the principal cause of lack of visual acuity in the students, existing spectacle use before school eye screening was very low. Correction of refractive error was found to be effective to improve vision in a large proportion of children. Our observation justifies special planning with priority in SES program for school children from low-income families. Identifying schools located near slum areas may help reach these children in need.
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