Visual impairment in school children in Southern India

V Kalikivayi; TJ Naduvilath; AK Bansal; L Dandona

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Year : 1997 | Volume : 45 | Issue : 2 | Page : 129-134

Visual impairment in school children in Southern India

V Kalikivayi, TJ Naduvilath, AK Bansal, L Dandona
Public Health Ophthalmology Service, L.V. Prasad Eye Institute, Hyderabad, India

Correspondence Address:
V Kalikivayi
Public Health Ophthalmology Service, L.V. Prasad Eye Institute, Hyderabad
India

Source of Support: None, Conflict of Interest: None

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PMID: 9475034

Abstract

This study was done to determine the prevalence of visual impairment due to refractive errors and ocular diseases in lower middle class school children of Hyderabad, India. A total of 4,029 children, which included 2,348 males and 1,681 females, in the age range of 3 to 18 years from 9 schools were screened with a detailed ocular examination protocol. Among 3,669 children in whom visual acuity could be recorded, on presentation 115 (3.1%) had visual acuity < 6/18 in the better eye (equivalent to visual impairment), while 41 (1.1%) had visual acuity of 6/60 in the better eye (equivalent to legal blindness) out of which 18 (0.5%) had visual acuity < 6/60 in the better eye (equivalent to economic blindness). Of 115 children who presented with initial visual acuity < 6/18, vision improved to ≥6/18 with refraction in 109 (94.8%). No child was legally or economically blind after refractive correction. Prevalence of hyperopia was 22.6%, myopia 8.6% and astigmatism 10.3%. The prevalence of myopia was significantly higher among children ≥10 years of age (P<0.001). The maximum, mean and median values for myopia were 10.00, 1.35 and 0.75 D in the better eye. For hyperopia these values were 8.50, 0.65 and 0.50 D. The major causes for best corrected visual acuity < 6/9 in the worse eye for 51 (1.4%) children included amblyopia in 40 (1.1%), corneal diseases in 5 (0.1%), cataract in 2 (0.05%) and others in 4 (0.1%). Out of the total, 30 (0.7%) children had strabismus. These data support the assumption that vision screening of school children in developing countries could be useful in detecting correctable causes of decreased vision, especially refractive errors, and in minimising long term permanent visual disability.

Keywords: Visual impairment, refractive errors, ocular diseases, school children, Southern India.

How to cite this article:
Kalikivayi V, Naduvilath T J, Bansal A K, Dandona L. Visual impairment in school children in Southern India. Indian J Ophthalmol 1997;45:129-34

How to cite this URL:
Kalikivayi V, Naduvilath T J, Bansal A K, Dandona L. Visual impairment in school children in Southern India. Indian J Ophthalmol [serial online] 1997 [cited 2023 Nov 28];45:129-34. Available from: https://journals.lww.com/ijo/pages/default.aspx/text.asp?1997/45/2/129/15002

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Population based data concerning the prevalence of visual impairment due to uncorrected refractive errors and ocular diseases in children are not readily available for India. Of particular importance are refractive errors, which are common and easily correctable, usually with spectacles. There have been reports on prevalence of refractive errors from other populations,[1][2][3][4][5][6][7][8][9][10][11][12][13][14] but little has been reported from the Indian population.[15] To our knowledge, there is no study available in the literature dealing with prevalence and pattern of refractive errors and eye diseases among children in Southern India. This information is important in planning appropriate eye care programs to reduce the burden of visual impairment among the younger population.

The objective of this study was to determine the prevalence of visual impairment due to refractive errors and ocular diseases among school children from a lower middle income urban population in Southern India.

Materials and methods

Ramnagar block situated in the north-east part of the city of Hyderabad was ascertained to represent the lower middle income urban population. Assuming a 5% prevalence of low vision based on crude estimates, the sample size required to estimate the prevalence of low vision in children with an absolute precision of 1% at the 95% confidence level was 4,000 with the cluster sampling design.[16] To obtain this sample, 9 schools were identified randomly from amongst the 17 schools in Ramnagar block. The total number of students in these schools was 4,618, out of which 4,029 (87.2%) were examined at a central examination site, which has been permanently established for the local population. These examinations were done between December 1993 and March 1995 by twelve qualified optometrists.

A standard examination procedure was used for each study subject. Detailed history about present and past ocular problems and treatment, history of any medical or surgical treatment, and family history were taken. Ocular examination included assessment of visual acuity for distance with Snellen chart at room illumination, and for near with near vision test types. Hirschberg test was performed to find out manifest or latent squint.

Objective refraction was performed with streak retinoscope, followed by subjective refraction, till the best corrected visual acuity was achieved. Cycloplegic refraction was performed in hyperopes aged > 4 years and Mohindra retinoscopy was used to test all children aged ≤ 4 years. Mohindra retinoscopy[17],[18] is a non-cycloplegic dynamic retinoscopy performed in a dark room at 50 cm with the eye fixating at the retinoscope light while the other eye is occluded. Subtracting 1.25 dioptres (D) from the power of the neutralising lens gives the refractive correction for distance.

As many children were not cooperative for subjective refraction, retinoscopy values were taken for the analysis of refractive errors. Myopia, hyperopia and astigmatism equal to or more than the absolute value of 0.50D were considered for the analysis.

Anterior segment of the eye was examined with slit lamp biomicroscope. Intraocular pressure was measured with Perkins applanation tonometer. If the child was not cooperative, digital tension was recorded. Retinal examination was performed with the help of direct ophthalmoscope without dilating the pupils.

For all the refractive errors, except myopia >6.00D, glasses were prescribed at the vision screening centre. Children with myopia >6.00D or any other ocular problem apart from refractive error were referred to the L.V. Prasad Eye Institute, Hyderabad for further evaluation and management.

Statistical analysis included estimation of the prevalence of various eye diseases with their 95% confidence intervals. Prevalence of eye disorders was estimated for the worse and better eye. Children were divided into two age groups, < 10 and ≥ 10 years, for comparison of prevalence. Disease prevalence was compared between groups with the test for large samples and Fisher's exact test for small samples.

Results

A total of 4,029 children were screened from nine schools. The mean age of children was 9.3±3.4 years, with a range of 3 to 18 years. There were 2,348 (58.3%) male children while 1,681 (41.7%) were females.

Presenting visual acuity could not be recorded among 360 children. Among the remaining 3,669 children, the age and sex distribution of visual acuity for the better and worse eye are given in [Table - 1] & [Table - 2]. On presentation, 115 (3.1%) children had visual acuity equivalent to visual impairment in the better eye by the WHO definition,[19] that is < 6/18; while 41 (1.1%) children had visual acuity equivalent to legal blindness as defined in US, that is ≤ 6/60, out of which 18 (0.5%) had visual acuity equivalent to economic blindness as defined in India, that is < 6/60. The prevalence of presenting visual acuity of ≤ 6/60 was significantly higher in age group ≥ 10 years as compared to age group < 10 years (p<0.001 for better eye as well as worse eye). Prevalence of presenting visual acuity of ≥6/9 was significantly higher in age group < 10 years as compared to ≥ 10 years (p=0.004, better eye) (p<0.001, worse eye).

Best corrected vision with spectacles could not be recorded in 370 children. Among the remaining 3,659 children, the age and sex distribution of visual acuity for the better and worse eye are given in [Table - 3] & [Table - 4]. The distribution of best corrected visual acuity was not significantly different between the age and sex groups.

There was no legally or economically blind child after refraction. Of the 115 children who had presenting visual acuity < 6/18 in the better eye, 109 (94.8%) improved with refraction to ≥ 6/18. Among the 188 children who presented with a visual acuity < 6/9 in the better eye, visual acuity improved with refraction in 151 (80.3%) to ≥ 6/9. Ten subjects (5.3%) were uncooperative. The causes of best corrected visual acuity <6/18 in the better eye in 6 children were amblyopia in 5 and corneal scar in 1. The causes of best corrected visual acuity < 6/9 in the better and worse eye are given in [Table - 5]. Amblyopia in 34 out of 40 children was associated with refractive error; in 4 with refractive error and strabismus, and in the remaining 2 with strabismus.

The distribution of refractive errors is shown in [Table - 6] & [Table - 7]. Refractive error could not be recorded among 42 children. Among the remaining 3,987 children, prevalence of myopia in the worse eye was 8.6%. The prevalence of myopia was found to be significantly higher among children aged ≥ 10 years compared to those < 10 years (p <0.001), whereas it did not differ significantly between males and females.

Prevalence of hyperopia in the worse eye was 22.6%. The prevalence of hyperopia was found to be significantly higher among females compared to males (p=0.001), whereas it did not differ significantly between the age groups.

Astigmatism was prevalent in 410 children (10.3%). Myopic astigmatism (7.6%) was more common than hyperopic astigmatism (2.1%). Among the prescriptions having a cylinder correction, 214 (5.4%) had with-the-rule astigmatism which included those prescriptions with minus cylinder axis oriented between 0 to 30 degrees or 150 to 180 degrees. Another 181 prescriptions (4.5%) had against-the-rule astigmatism, which included those prescriptions with minus cylinder axis located between 60 to 120 degrees. The remaining 15 (0.4%) were oblique with their minus cylinder axis either between 31 to 59 degrees or 121 to 149 degrees.

Of the total 4,029 children, strabismus was found in 30 (0.7%). Of these 30, 9 (30%) were esodeviations and 21 (70%) exodeviations. Another 23 (76.7%) had primary eso or exodeviations, 4 (13.3%) were secondary to refractive errors, and 3 (10%) were secondary to some ocular disease. Association of eso or exodeviations with refractive errors was not found to be significant. One case of juvenile glaucoma was detected amongst the children examined in this study.

One hundred and sixty seven children were referred to the referral hospital for further evaluation and management. Out of the 43 children who visited the referral hospital, 33 were correct referrals and 10 had no significant ocular disease on further evaluation.

Discussion

In the present study, vision equivalent to legal blindness was found in 1.1% children, and that equivalent to economic blindness in 0.5%. The only cause of this blindness was refractive error. There was no legally or economically blind child after refractive correction which underscores the importance of vision screening of school children.

The prevalence of myopia was found to be 8.6% in the present study. A higher prevalence has been reported in north Indian children by Chandra et al,[15] whereas lower prevalence has been reported in Melanesian school children by Garner et al[7],[8] and Grosvenor.[9] Such differences in prevalence could be due to differences in populations. A higher prevalence of myopia has also been reported in the adult population.[2],[4][5][6],[10],[13] Gordon[10] reported that myopia was seen most frequently in the age group 11 to 30 years and was less in the younger and older age groups. In the present study, prevalence of myopia was found to be significantly higher among children aged 10 years or greater compared to those aged less than 10 years. This suggests indirectly that myopia is progressive and/or that the onset of myopia may be delayed in some children. In a study by Goldschmidt,[3] myopia was seen more frequently in girls than boys. Garner et al[7] reported that there was no difference in the prevalence of myopia between girls and boys which is similar to our results.

The prevalence of hyperopia was found to be 22.6% in the present study of school children, and was significantly higher among females compared to males. The prevalence of astigmatism ≥ 0.50D and ≥ 1.25D in our study was found to be 10.3% and 2.4%, respectively.

A prevalence of 0.25% for astigmatism ≥ 1.25D has been reported in Melanesian children.[8]

The most important cause of uncorrectable visual loss in our study was found to be amblyopia, mostly caused by refractive errors, which is comparable with the results of Ingram.[20] The prevalence of amblyopia was found to be 1.1% in our study. A similar range of prevalence for amblyopia, 1.07%-1.85%, has been reported for school children in Colombia,[21] Denmark,[22] Madagascar,[23] and Saudi Arabia.[24]

Ingram reported that hyperopia was significantly associated with esotropia.[20] However, our study did not achieve significance for this association, probably due to the small number of esotropic cases.

A large number of uncorrected refractive errors were found in this school screening, causing 1.1% and 0.5% prevalence of visual acuity equivalent to legal and economic blindness, respectively. Vision improved in a large majority with refractive correction. There was no case of legal or economic blindness after refractive correction. Thirty three cases of treatable ocular disorders other than refractive errors were also detected in this screening. One has to be cautious in extrapolating the results of this school screening of urban lower middle class children to the entire population of school children in India or the rest of the developing world. However, these data validate the need for vision screening of school children in atleast some parts of the developing world. This screening could serve a useful purpose in detecting correctable causes of decreased vision early in life and minimising long term permanent visual disability.

One also has to realise that with a significant proportion of children not going to school in rural India and other parts of the developing world, a more complete assessment of visual impairment in children would be likely with population based studies not restricted to school children. This information is expected from a study being conducted by L V Prasad Eye institute.[25]

Acknowledgment

VST Industries Limited supports the examination centre at which the eye examinations were done.

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