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 Table of Contents  
Year : 2022  |  Volume : 60  |  Issue : 3  |  Page : 240-245

Comparison of ocular pathologies between children attending rural and urban schools in south india: A retrospective analysis

1 Department of Paediatric Ophthalmology, Vivekananda Mission Ashram Netra Niramay Niketan, Haldia, West Bengal, India
2 Departments of Paediatric Ophthalmology and Strabismology, Aravind Eye Hospital and PG Institute of Ophthalmology, Tirunelveli, Tamil Nadu, India
3 Department of Glaucoma Services, Aravind Eye Hospital and PG Institute of Ophthalmology, Tirunelveli, Tamil Nadu, India
4 Department of Cataract and IOL Services, Aravind Eye Hospital and PG Institute of Ophthalmology, Tirunelveli, Tamil Nadu, India
5 Department of Biostatistics, Aravind Eye Hospital and PG Institute of Ophthalmology, Tirunelveli, Tamil Nadu, India

Date of Submission27-Feb-2022
Date of Decision01-Jul-2022
Date of Acceptance08-Jul-2022
Date of Web Publication26-Sep-2022

Correspondence Address:
Sabyasachi Chakrabarty
Vivekananda Mission Ashram Netra Niramay Niketan, Thakur Bari Road, Rampur, PO Chaitanyapur, Haldia, Purba Medinipur – 721 645, West Bengal
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tjosr.tjosr_26_22

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Aims: To assess the differences in ocular morbidity with/without visual impairment between rural and urban school-going children using a two-step screening strategy. Methods: Data obtained by a hospital team from school camps conducted between the 1st of February 2019 and the 31st of December 2019, in schools with a strength of at least 1,000 students were reviewed retrospectively. The differences in ocular pathologies between the rural and urban cohorts were evaluated. A P < 0.05 was considered significant. Results: Out of 25,132 students (nurban = 12,562; nrural = 12,570), 14.44% (nurban = 1,585; nrural = 2,044; P < 0.001) were selected for evaluation by the hospital team after a primary screening by their class teachers. A statistically significant difference was noted in the frequency of refractive errors (urban = 6.8%; rural = 6.0%; P = 0.01), allergic conjunctivitis (urban = 0.2%; rural = 0.05%; P = 0.001), and amblyopia (urban = 0.03%; rural = 0.12%; P = 0.009) between urban and rural children. Simple and compound myopic astigmatism were significantly more common in urban children (p < 0.001 and 0.03 respectively). There was no significant difference in the incidence of spectacle use (P = 0.11) between the two cohorts. A Cochran--Armitage trend test revealed a statistically significant increase in the proportion of myopia with age among the children evaluated by the hospital team (p < 0.001). Conclusion: Allergic eye disease and myopic astigmatism are commoner in urban children. Routine ophthalmic screening is required to identify uncorrected refractive errors and amblyopia, especially in rural school children.

Keywords: Allergic eye disease, astigmatism, refractive error, rural versus urban children, school screening

How to cite this article:
Chakrabarty S, Ravindran M, Pillai MR, Chandrashekharan S, Pawar N, Uduman MS. Comparison of ocular pathologies between children attending rural and urban schools in south india: A retrospective analysis. TNOA J Ophthalmic Sci Res 2022;60:240-5

How to cite this URL:
Chakrabarty S, Ravindran M, Pillai MR, Chandrashekharan S, Pawar N, Uduman MS. Comparison of ocular pathologies between children attending rural and urban schools in south india: A retrospective analysis. TNOA J Ophthalmic Sci Res [serial online] 2022 [cited 2022 Nov 30];60:240-5. Available from: https://www.tnoajosr.com/text.asp?2022/60/3/240/357113

  Introduction Top

The School Eye Screening Programme is the second largest initiative under the National Programme for Control of Blindness in India.[1],[2] The major innovation in this programme is the utilization of trained school teachers as primary vision screeners.[3] This helps to overcome the paucity of trained ophthalmic personnel (Ophthalmologist density = 13/10,00,000; optometrist density = 5/10,00,000) who now have to evaluate only those who fail the screening test.[2],[4] This retrospective study summarizes the observations of such a multistaged screening project using the 'all class teacher' model and enlists the differences in the ocular pathologies between children studying in rural and urban schools.

  Materials and Methods Top

The medical records of school camps conducted by a tertiary eye hospital between the 1st of February 2019 and the 31st of December 2019 were reviewed retrospectively. De-identified data from camps conducted in schools having students from classes I to XII (aged between 5 years to 18 years) with an overall strength of at least 1,000 pupils were analyzed. This review received a certificate of approval from the Institutional Review Board (AEH,TVL-IEC/CS/2020/010) and was carried out in accordance with the tenets of the Declaration of Helsinki.

The camps were organized after obtaining a written consent from the principals of the concerned schools and the local district authorities. A primary screening was performed by class teachers, a week before the proposed visit by the hospital team. The class teachers were trained via programmes at the base hospital, which included didactic lectures on ocular ailments and hands-on training on vision screening and torch light evaluation.

The teachers were trained to perform vision screening using a simplified Snellen's chart with 4 'E'-s corresponding to a visual acuity of 6/12 at a distance of 6 m. Tumbling 'E'-s were printed on both sides of the chart but in a different order. They recorded the ability of the children to identify the direction of the 'E'-s from the test distance. Each eye was tested separately. In order to prevent the children from memorizing the order of the 'E'-s, the class teachers were instructed to use the reverse side of the chart while testing the second eye. The children were instructed to use their glasses during the screening test if they already had one. Children who failed the initial screening (unable to identify at least three out of the four 'E's correctly, uncooperative children or children with other ocular symptoms) and all children wearing glasses were selected for evaluation by the hospital team.

A written informed consent for examination by the hospital team was obtained from at least one of the parents or the legal guardian for each of these selected students. These informed consent forms also required the parent(s)/guardian(s) to declare the history of allergies and systemic illnesses in their child (ren)/ward (s).

The hospital team included an ophthalmologist and four optometrists trained in pediatric refraction. A structured, age-appropriate symptom review form was filled up for each student. All the selected students underwent a preliminary vision assessment, retinoscopy and subjective refraction at 6 m. Students with suspected uncorrected ametropias or those in whom the manifest refraction did not match the current glass power underwent a wet refraction. The ophthalmologist evaluated the final refractive correction and prescribed glasses or referred the child to the hospital if needed. The reasons for referral to the hospital were performance of a post-mydriatic test, management of a manifest strabismus and/or a suspected amblyopia or an ocular pathology requiring further evaluation.

Data obtained by the hospital team was used for analysis. The following data were included in this study: demographics, the location of the school (rural/urban), the uncorrected and best corrected visual acuities, refractive status and the final diagnoses. The principal cause of visual impairment of 6/12 or worse was recorded. The diagnosis of refractive error was used if the eyes improved to 6/9 or better with glasses. Amblyopia was diagnosed if the best corrected visual acuity did not improve beyond 6/12 in the absence of an apparent organic cause, and in the presence of a manifest strabismus, anisometropia of ≥ ±2.0 D and/or a bilateral ametropia of at least ±6 D in spherical equivalents. If the child had more than one ocular problem, both the diagnoses were considered for data analysis as two distinct entities. Medical records lacking any of the above parameters were excluded from analysis.

All statistical analyses were performed using STATA 14.0 (StataCorp, Texas, USA). Continuous variables were compared using the independent t-test. The association between categorical variables was determined by the proportion test, the χ2 test or the Fisher's exact test. The choice between a χ2 test and a Fisher's exact test depended upon satisfaction of Cochran's rule.[5] The Cochran--Armitage trend test was used to analyze the trend in the proportion of myopia by age. A P value less than 0.05 was considered significant.

  Results Top

A total of 17 schools (ten rural and seven urban) fit the selection criteria and the medical records of 3,629 students screened by the hospital team were analyzed. These children had been selected for evaluation after a primary screening of 25,132 (12,562 urban and 12,570 rural) students by their class teachers. None of the records had to be discarded for missing entries.

The demographic parameters of all the students evaluated by the hospital team are given in [Table 1]. For analysis, a rural locality was defined as an area having a population density of up to 400 per square km and being governed by a panchayat (data as per the 2011--21 decennial census). A significantly greater number of students were selected for the second stage of evaluation from rural schools [n urban = 1,585 (12.62%), nrural = 2,044 (16.26%); P < 0.001].
Table 1: Demographics of the subjects screened by the hospital team

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[Table 2] summarizes the final diagnoses in the dataset analyzed. A statistically significant difference was noted in the frequency of refractive errors (6.8% vs. 6.0%; P = 0.01), allergic conjunctivitis (0.2% vs. 0.05%; P = 0.001) and amblyopia (0.03% vs. 0.12%; P = 0.009) between the children in the urban and the rural groups respectively. The distribution of different refractive errors and the pattern of spectacle use in the children evaluated by the hospital team are summarized in [Table 3] and [Table 4], respectively. There was a statistically significant difference in the proportion simple myopic astigmatism (1.43% vs. 1.08%; P < 0.001) and compound myopic astigmatism (1.27% vs. 1.06%; P = 0.03) between urban and rural children, respectively.
Table 2: Diagnosis among urban and rural school children

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Table 3: Distribution of different refractive errors in the children

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Table 4: Distribution of spectacle usage among the two groups

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The proportion of myopia according to the age of the children evaluated by the hospital team was analyzed [Figure 1]. The Cochran-Armitage trend test showed that the proportion of myopia significantly increased with increasing age (16.7% at 5 years to 36.1% at 18 years, P < 0.001).
Figure 1: Bar graph showing the proportion of myopia with age in children evaluated by the hospital team

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  Discussions Top

There is limited evidence regarding the most cost-effective strategy for vision screening in children.[6] Although the Refractive Error Study in Children (RESC) protocol is the most robust, it requires a cluster sampling technique, dedicated enumerators for the initial enlistment, trained optometrists/ophthalmologists for all the children to be screened and limits the analysis of retrospective data.[7] A multi-staged screening technique involving school teachers as the primary screeners is an efficient alternative.[8],[9] Here, optometrists and ophthalmologists have to evaluate a limited number of selected children, thus reducing their burden.

There are two ways of implementing the multistaged screening strategy for evaluating school children. In the traditional system, a school teacher in a less demanding subject is selected by the principal for training and he/she has to screen 250 to 300 children.[8] A novel alternative strategy is to employ all the class teachers to screen. With this strategy, a teacher has to screen an average of only 52 children.[10] Our study has used data from an 'all class teacher' model of multistaged screening which is likely to be more accurate than the traditional single school teacher model.

This retrospective study analyses the differences in ocular morbidities with or without visual impairment in school-going children from rural and urban backgrounds. As this study analyses data from nonprobability samples, the skewed male: female ratios (0.62 in urban vs. 0.49 in rural children; P = 0.001) is probably the reflection of a selection bias. Another alternative hypothesis is that this gender disparity mimics the normal distribution of refractive errors in the population, myopia, and myopic astigmatism being more common in females.[11] As the demographics of all the children screened by the teachers were unavailable, the latter hypothesis could not be verified and so a gender-based analysis of ocular pathologies and their extrapolation to the entire population has been strictly avoided.

The overall prevalence of refractive errors in our study was 6.4% with a significantly greater prevalence in the urban cohort (P = 0.01). In published literature, the prevalence of refractive errors in Indian children has been reported vary between 2.65% and 10.8%.[12–14] Although the exact reason for increased rates of refractive errors in urban children is unknown, possible determinants could be an increased duration of near work or screen-time with lower opportunities for outdoor activities.[15],[16]

Myopia was the most common refractive errors in both urban and rural children (3.66% vs. 3.4%, respectively; P = 0.11). The Cochrane-Armitage trend test showed a statistically significant increase in the proportion of myopia among all ocular problems in the screened children with increasing age. The rate of increase in the proportion of myopia was nonlinear and approximately followed the polynomial y = 0.1353χ2 + 0.0601χ + 10.654. A meta-analysis on the prevalence of myopia in children in different ethnic populations has also reported a nonlinear increase in the incidence of myopia with age.[17]

Simple myopic astigmatism and compound myopic astigmatism were more frequent in urban children (P < 0.001 and P = 0.03, respectively). In most studies, the difference in the prevalence of refractive errors between urban and rural children has been attributed to a higher prevalence of myopia in the urban population.[17],[18] This contradiction might have occurred because of a difference in definitions. In contemporary literature, a diagnosis of astigmatism is used only if the cylinder power is more than two dioptres. Cases with lower degrees of astigmatism are classified as a spherical refractive error and their spherical equivalents are used for data analysis.[18] However, in our study, all cases with a cylinder power of more than 0.5 Dioptres have been classified under the diagnosis of astigmatism.

The higher rates of myopic astigmatism in urban children in our study may be linked with a greater prevalence of allergic conjunctivitis in the same group (P = 0.001). This correlates with the findings of Kim et al.[19] who found a statistically significant correlation between the risk of allergic eye disease and astigmatism or an urban habitat.

Although, the higher incidence of allergic eye disease in the urban group can be due to a greater exposure to traffic-related pollution,[20] there is limited evidence regarding the association of allergic conjunctivitis and refractive error in children.[21] Classically, a myopic astigmatism is associated with tear-film instability due to changes in the corneal surface. This results in accumulation of allergen-induced substances in the conjunctival cul-de-sac with subsequent adsorption and immune-mediated inflammation.[21] On the other hand, habitual eye-rubbing which accompanies an allergic eye disease traumatizes the corneal epithelium repeatedly and may induce changes in the corneal surface due to compressive and shear forces or may produce a progressive decline in the stromal mass and bio-mechanical resistance resulting in a myopic astigmatism.[22–25] Therefore, it is likely that one condition potentiates the other.

There was a significantly greater prevalence of amblyopia in the rural children (0.12% vs. 0.03%; P = 0.009). This may be a reflection of the difference in opportunities for routine ophthalmic screening or a knowledge gap regarding the need for a basic ophthalmic evaluation of children among parents.[26] Studies conducted on Indian children via the RESC protocol have also revealed a greater prevalence of amblyopia in rural children compared to urban children (0.78% vs. 0.57%) but the differences were statistically insignificant (p = 0.186).[12],[13] A few studies have concluded that the incidence of amblyopia is greater in urban rather than in rural children,[18],[27] However, in one of these studies, tribal children made up the rural group and the low incidence in this group could have been because many children missed their examination by the optometrist team.[27]

This study suffered from a few limitations because of its design. In the absence of demographic data on all the children screened initially by the teachers, age and gender-based speculations on the actual prevalence of diseases could not be made. Moreover, the data collected was school based rather than population based. A selection bias is inherently introduced in school based studies because many children with poor vision are unable to attend schools and are thus left out. On the other hand, if prolonged near work in schools has a causal relationship with the onset and progression of myopia, a school-based study will intrinsically over-estimate its prevalence.[16]

This study was based on data collected via a multi-staged screening strategy and so it depended heavily on the sensitivity and the false negativity rates of the primary screening. In literature, the sensitivity of screening by teachers has been reported to vary between 80.51% and 91.39% with a false negativity rate of 4.35% and 9.87%.[9],[28] As there was no provision for re-examination of the children labelled as normal by the initial screeners, the false-negativity rate could also not be calculated, and the actual disease prevalence might have been miscalculated. Finally, the cross-sectional design limited the evaluation of compliance to spectacles issued in these camps.

Despite these short-comings, this retrospective study demonstrates the pivotal role of a multi-staged screening strategy in reducing the burden of screening from trained ophthalmic personnel. It re-enforces the need for routine screening for refractive errors and amblyopia in school-going children. The study also validates the need for screening of rural children who may be affected with a potentially treatable cause for vision loss (amblyopia) but might lose out on an opportunity for treatment because of the lack of a routine ophthalmic evaluation. However, it may not always be possible to obtain co-operation from school teachers uniformly across the country and community health personnel may have to use other approaches under such circumstances.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Figure 1]

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


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