Indmedica Home | About Indmedica | Medical Jobs | Advertise On Indmedica
Search Indmedica Web
Indmedica - India's premier medical portal

Indian Journal of Community Medicine

Prevalance of Refractive Errors in School Children (12-17 Years) of Ahmedabad City

Author(s): Sonam Sethi, G.P. Kartha

Vol. 25, No. 4 (2000-10 - 2000-12)

Deptt. of Preventive & Social Medicine, B.J. Medical College, Ahmedabad

Abstract:

Research question: What is the prevalence of Refractive Errors in school children (12-17 years) of Ahmedabad City?

Objective: To study the prevalence of refractive errors in school children (12-17 years) of Ahmedabad city by age, sex, class and type.

Study design: Cross-sectional.

Setting: Schools of Ahmedabad city.

Participants: School children aged 12-17 years studying in 7th to 12th class.

Study period: September 1997 to March 1998.

Sample size: 1,647 school children which included 828 males and 819 females.

Study variables: Refractive errors by age, sex, class and type.

Statistical analysis: Chi square test, proportions.

Results: 25.32% of the students were found to be having refractive errors. Of these 47% were females and 53% were males. The distribution of refractive errors was: Myopia - 63.5%, Hypermetropia 11.2% and astigmatism 20.4%.

Conclusions: 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 visual disability.

Keywords : Prevalence, Refractive errors, Myopia, Hypermetropia, School children, Age, Sex, Class

Introduction:

Refractive error is an optic defect, intrinsic to the eye which prevents light from being brought to a single point focus on the retina, thus reducing normal vision. Diagnosis and treatment of refractive errors is relatively simple and is one of the easiest way to reduce impaired vision. Yet, in India refractive error is the second major cause for patients to consult ophthalmologists.

Refractive errors constitute a sizeable proportion of any large eye OPD in our country. The overall incidence has been reported to vary between 21% and 25% of the patients attending eye OPD in India2. About 13% of Indian population is in the age group of 10-15 years1. Poor vision in childhood affects performance in school or at work and has a negative influence on the future life of the child. Moreover, planning of a youth's career is very much dependent on the visual acuity, especially in jobs for navy, military, railways and aviation3. This warrants early detection and treatment of refractive errors to prevent permanent disability.

Population based data concerning prevalence of refractive errors in children are not readily available for India. There have been reports of refractive errors for populations of other countries, but very little has been reported for India population.

The present study was carried out in the schools of Ahmedabad city. Students of the age group 12-17 years were chosen because refractive errors are most prevalent in this age group, occurring in as high as 20% of children by 16 years of age2.

This study presents the prevalence of refractive errors by age, sex, class, type and socio-economic status among school children of Ahmedabad city. The mean age of onset of refractive errors was computed. This information may be used for planning appropriate eye care programme for the high risk groups in order to reduce the burden of visual impairment in the population.

Material and Methods:

Ahmedabad is metropolitan city. There are approximately 260 schools in the city. For the study purpose, Naranpura, Ramdevnagar, Memnagar and Vastrapur were chosen and the schools were selected randomly. Students in the age group 12-17 years studying in classes 7th-12th were included in the study. Assuming a 20% prevalence of refractive errors based on a pilot study, the sample size was calculated to be 1526 for this cross-sectional study. However, 1714 students were selected, of these 67 students remained absent during study period and could not be examined. Students of 10th, 11th, and 12th classes were busy preparing for their examinations so their number was less.

The students were examined in their respective classes. The screening1 was done in the following way. From 6 metre distance the student was shown the E-card with four E's of standard size (6/9 of Snellen's chart). For each eye the child had to indicate the direction of open end of E. By simply rotating the card the sequence could be changed. The child either indicated the direction correctly (eye sight good) or incorrectly (eye sight not good). In case of a doubt the eye sight was recorded as not good. Children whose eye sight was not good i.e. who had a visual acquity of less than 6/9 were sent for subjective refraction. Subjective refraction was done till best corrected visual acquity was achieved. Cycloplegic refraction was advised for students in whom best corrected visual acquity could not be achieved. Those having organic defects in eye such as corneal opacity, opacity of the lens, choroid and retinal disorders were excluded. It must be mentioned that students were screened only for distant vision. Therefore, number of hypermetropics was far less than myopics.

Results:

Age, sex and class distribution:

Amongst 1,647 students who were examined, 828 were males and 819 were females. The age of the students ranged from 11 to 17 years. The mean age was 13.22 years, median and mode age was 13 years.

Table I: Sex-wise distribution of students with and without refractive errors.

Sex Refractive errors
Yes (%) No. (%)
Males 221 (26.7) 607 (73.3)
Females 196 (23.9) 623 (76.1)
Total 417 1230

In the study 417 students (25.32%) were found to have refractive errors. Of these 196 (47%) were females and 221 (53%) were males. There was no significant difference between refractive errors amongst males and females, (X2 = 1.34, p>0.25).

Out of 417 students with refractive errors, myopia was found in 265 (63.5%), hypermetropia in 47(11.2%) and astigmatism in 85 (20.4%) cases.

Table II: Class-wise distribution of students with and without refractive errors.

Class Refractive errors Total
Yes (%) No (%)
7 134 (23.3) 441 (76.7) 575
8 91 (20.7) 347 (79.3) 438
9 127 (27.1) 342 (72.9) 469
10 39 (43.8) 50 (56.2) 89
11 12 (36.4) 21 (63.6) 33
12 14 (32.6) 29 (67.4) 43
Total 417 1230 1647

Number of ammetropic of 10th to 12th standard were significantly higher (d value = 3.96, p<0.05) than the Ammetropic students of 7th to 9th standard, thereby showing that ammetropia is related to number of years of schooling.

Table III: Age-wise distribution of students with and without refractive errors.

Age Refractive errors Total
Yes (%) No (%)
11 2 (6.7) 28 (93.3) 30
12 125 (24.5) 386 (75.5) 511
13 111 (22.5) 382 (77.5) 493
14 101 (25.9) 288 (74.1) 389
15 52 (36.0) 93 (64.0) 145
16 22 (31.9) 47 (68.1) 69
17 4 (40.0) 6 (60.0) 10
Total 417 1230 1647

The refractive errors increased with age.

Table IV: Age of onset of refractive errors.

Age of onset No of cases Percentage
5 4 1.4
6 4 1.4
7 8 2.8
8 12 4.2
9 22 8.0
10 38 13.8
11 51 18.4
12 65 23.5
13 49 17.7
14 14 5.1
15 8 2.9
16 1 0.4
17 1 0.4
Total 277 100

It was found that 277(66.4%) were aware of their refractive errors, whereas, 140(33.6%) were unaware of the problem. The mean age of onset of refractive errors in these cases was 11.22 2.07 years and the median and mode age was 12 years.

Discussion:

In the present study, prevalence of refractive errors was found to be 25.3% which included 63.5% myopia, 11.2% hypermetropia and 20.4% astigmatism.

These results are similar to the study carried out by Laatkainen4. The prevalence of refractive errors varies depending on the population under study, particularly with regard to the age groups under consideration. In the present study, population consisted of age group 11-17 years. It is during this period, the children are at risk of developing refractive errors, because they are actively growing and subjected to the strain of near work due to demanding academic schedules. Such a population is likely have more number of myopics.

Refractive errors did not differ significantly between males and females5. However, in other studies6,7 refractive errors were found more commonly in girls than in boys, probably related to their rate of growth. Girls attain puberty earlier on an average and reach their final body weight 1-2 years earlier than the boys.

Sperduto8 showed that myopic prevalence rises with educational level. The present study also showed that the number of students with refractive errors increased as the students move to higher classes, implying thereby that a significant relationship exists between refractive error and educational level.

Conclusion:

The 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 visual disability.

Recommendations:

The present study shows that the adolescent age group forms the high risk group for refractive errors and most of the children are unaware of refractive errors. Due emphasis must, therefore, be laid upon the screening for refractive errors in this age group. Moreover, attention should be paid to visual hygiene. While reading illumination should be good and adequately arranged. Posture should be easy and natural. Clarity and print should be carefully supervised. An undue ocular fatigue should be avoided. Students should have as many outdoor hours as possible. Students need to be educated about signs and symptoms of refractive errors. Pre-school and school screening for detection of refractive errors should be carried out on periodic basis.

Acknowledgements:

I wish to acknowledge the guidance of Dr. V.S. Rawal, Head of the Department PSM for his constant support and encouragement. I also than WHO for providing information and software like EP16 for the computer aided analysis of observations.

References:

  1. Limburg H: Cost effective screening of school for refractive errors, W.H. Fourm 1995, 16, 173-8.
  2. Goswami A, Ahmead E, Shaha PL, Roy IS: An epidemiological pattern of cases of refractive errors, JIMA 1979, 72(10), 227-8.
  3. Mukherjee R, Seal SC: An epidemiological study of refractive errors among school children in Calcutta, JIMA 1973, 73(9-10), 159-64.
  4. Krause VLF, Krause Kaisa, Rantakallo Paule: Some differences in refractive errors upto age of 15, Acta ophthamol 1982, 60, 917-26.
  5. Blindness & visual impairment in Gujarat, State ophthalmic cell, Govt. of Gujarat, 1986-89.
  6. Tay MT et al: Myopic and educational attainment in 421116 young Singaporean males, Ann Acad Med, Singapore, 1992, 21(6): 785-91.
  7. Venkatramana K, Naduvilam T: Visual impairment in school children in Southern India, Ind. Jou. of Ophthalmol, 1997, 129-34.
  8. Elkinton AR, Khan PT: Refractive Errors, BMJ, 1988; 297: 192-5.
Access free medical resources from Wiley-Blackwell now!

About Indmedica - Conditions of Usage - Advertise On Indmedica - Contact Us

Copyright © 2005 Indmedica