a prevalence study on myopia among school going children in a rural area of south india

374 Indian Journal of Clinical Practice, Vol. 25, No. 4, September 2014

pediAtrics

A Prevalence Study on Myopia Among School Going Children in a Rural Area of South Indiak rAJendrAn*, mohAmmed hAneef, kAiLAs chAndrABhAnu, krishnAmoorthY#, mAniL muhAmmed$, rAtheesh t piLLAi

aBstract

Introduction: Myopia or short sightedness is a type of refractive error in which parallel rays coming from infinity are focused in front of retina when accommodation is at rest. It is a vision condition in which close objects are seen clearly, but objects farther away appear blurred. Myopia occurs if the eyeball is too long or cornea has too much curvature. Myopia is a common vision condition affecting nearly 30% of population. It occur more frequently among school children aged between 8 and 12 years. Because the eye continues to grow during childhood, it typically progresses until about age 20. Aims and objectives: This study aimed at finding the prevalence of myopia among the students aged 10-12 years of a school in a rural area of Kollam and the influence of environmental factors, indoor activities like reading, computer games and outdoor activities and genetic factors in development of myopia. Materials and methods: Study population included students of a nearby school. Students of age >10 years were considered, so students of 5th, 6th and 7th standard students were selected. Each of the division was considered as one strata and simple random sample of clusters had been selected from each standard. All the students of the selected division were selected to sample. Thus, a total of 68 students from that school were taken for the study. The study setting was in a rural area in Kollam district of Kerala. Results: Snellens chart along with unilateral vision blinders were used for evaluating vision. Details of factors influencing were obtained using a pretested questionnaire in a pilot study. The prevalence of myopia in school children of rural community in Kollam was found to be 51.47% in which a group of hidden myopic of 43.1% were discovered.

keywords: Myopia, refractive error, diopter

Myopia is a refractive error, which means that the eyes do not bend or refract light properly to a single focus to see images properly. In myopia, close objects look clear but distant objects look blurred. It is an eye focusing disorder, not an eye disease. Myopia is inherited and is often discovered in children when they are between the ages 8 and 12 years old. During the teenage years, when the body grows rapidly, myopia may become worse. Between the ages 20 and 40, there is usually little change. Myopia can also occur in adults.1 The incidence of myopia with in sampled population often rises with age, country, sex, race, ethnicity, occupation environment and other factors. The prevalence of myopia has been reported as high as 70-90% in some Asian countries.1-3

*Professor and Haed, Dept. of PediatricsProfessor and Head, Dept. of OphthalmologyProfessor, Dept. of Pediatrics#Assistant Professor, Dept. of Ophthalmology$Assistant professor, Dept. of PediatricsAssociate ProfessorAzeezia Institute of Medical Sciences and Research Center Meeyannoor, Kollam, KeralaAddress for correspondenceAzeezia Institute of Medical Sciences and Research CenterMeeyannoor, Kollam - 37, KeralaE-mail: [email protected]

In India, up to 41% of adult population is myopic to 1D and up to 80% to 0.5D. Myopia occurs more frequently below the age of 20 years. Risk of myopia is increased particularly in those children who have a reading habit, increased indoor activities and family history. Close reading at a distance 30 minutes and in a low illumination adds upon the progression of myopia. The risk of development of myopia further increases with the habit of reading in supine position.3

There is an increased incidence of myopia among students. Alteration in visual power is common in age group 10-12 years. Students are found to be associated with lot of near work and prolonged accommodation. So, we were keen to observe risk factors that increase the incidence of myopia in this age group. Myopia is more common in children who are constantly engaged in indoor activities like watching TV, computer, mobile and videogames. Incidence of myopia is more in children who watch TV and use computer in a low illumination. Lower levels of outdoor activities in children increase the risk of myopia. Unhealthy reading habits like reading in supine position at a distance >30 cm and in a low illumination. Genetics also play an important role in development of myopia.

Pediatrics

375Indian Journal of Clinical Practice, Vol. 25, No. 4, September 2014

Myopia is a common vision condition affecting nearly 30% of population. It occur more frequently among school children aged between 8 and 12 years. Because the eye continues to grow during childhood, it typically progress until about age 20. However, myopia may also develop in adult due to visual stress or health condition such as diabetes.2-5

Types of myopia Etiological classification: Axial myopia, curvature

myopia, positional myopia, index myopia and myopia due to excessive accommodation.

Clinical classification: Congenital myopia, simple myopia, pathological myopia and acquired myopia.

aims and oBjectiVes

This study aimed at finding the prevalence of myopia among the students aged 10-12 years of a school in a rural area of Kollam and the influence of environmental factors, indoor activities like reading, computer games and outdoor activities and genetic factors in development of myopia and find the influence of unhealthy reading habits like reading in supine position, in low illumination at a near distance for >30 minutes in development of myopia.

material and methods

Study population included students of a school in Kollam district, Kerala, India. Students of age >10 years were considered, so students of 5th, 6th and 7th standard students were selected.

Sample size, n = 4PQ/L^2

= (4 60 40)/(12 12)

= 67

We selected 68 students to equalize the number of boys and girls.

P = Prevalence rate; Q = 100-P

L = Allowable error of P (20%)

sampling technique

Each of the division was considered as one strata and simple random sample of clusters had been selected from each standard. Thus, we took 5th, 6th and 7th standard students. Each standard consists of 3 divisions each with 45-50 students. A division was selected at random from all the classes. All the students of the selected division were selected to sample. Thus, a total of 68 students from that school were taken for the study.

Visual acuity was tested using Snellen`s chart. All students were interviewed by using self-administered questionnaire. Students were placed 6 m from Snellens chart and asked to read the chart. Each eye was tested separately. From the findings of this, students were grouped as myopic and nonmyopic. This is to correlate the habits and their myopic stage.

Students who are not having 6/6 vision for at least one eye were considered as myopic.

results

From the study conducted, it was found that the prevalence of myopia is 51.47%.

According to our study, the significant risk factors were:

Reading in supine position Reading books at a distance >30 cm. Watching TV in low illumination Lower levels of outdoor activities

In a study of 68 students, we found that 35 students were myopic. Among the 35 myopic students, 20 are females and 15 are males (Figs. 1 and 2). We found that only 10 students were using spectacles. The rest did not use spectacles and had not approached the eye clinic before. Twenty-five students were having undiagnosed myopia. The cause of this hidden group was due to lack of awareness or due to poor parental education and lack of proper care and attention given to the children and may be due to lack of healthcare facilities in the community.

Most of the cases of myopia in children can be detected in the school by the teachers, if they give proper attention and care. A properly illuminated and ventilated class is a necessity and the school environment should be such that it helps in proper development of health of the child. Here we found that, the class rooms were not properly illuminated and ventilated and they were also overcrowded. The student in the last row was not able to see the blackboard due to the above-said problem. Proper awareness guidelines and medical camps should be conducted in school on myopia, so as to prevent and also detect new cases of myopia (Fig. 3 and 4).

After the interview, students were found to have many risk factors which contribute to development of myopia as well as many factors, which prevent the incidence. In our study, we found that, girls were more myopic than boys, it was true but our hypothesis was not proved since p value is >0.05. In our study, we found

Pediatrics


may cause eye strain and reduced blinking rate, signs of which include blurred vision and red or watery eyes. About 5% of population is light sensitive, experiencing discomfort from flickering light of specific frequency, colors and patterns. Some students get headache from spending excessive time in front of TV or computer. To avoid some of these problems, it is advisable not to watch TV in a dark room, to sit a little further from the TV, to angle the computer screen straight ahead and to use antiglare screen. Very close viewing of TV or computer screen may slightly increase the temperature of eye tissue due to electromagnetic radiation from screen (Figs. 7 and 8).

Playing mobile games for long time induces greater stress on the eye as mobile screen is so small and greater stress is needed to play the game. Many of the parents are not aware of these side effects that mobile phones can make, so let their children to play with these for a longer period of time.

Unhealthy reading habits have an influence in the development of myopia. This was proved by our study. Unhealthy reading habits followed by children like reading in low illumination at a near distance and for longer duration add on the progression of myopia. It has been proposed that hyperopic defocus induced by accommodative lag during near work stimulate eye growth, since imposed hyperopic defocus is a powerful stimulus for eye growth. Attempt to decrease myopic progression by decreasing the need for accommodation or accommodative lag by providing clear vision over a range of viewing distance has shown clinical significance. Reading in supine position

that the relation between myopia and family history had no significance. It may be because of number of students having family history of myopia was less in our study (Fig. 5). Indoor activities like watching TV or looking at computer at a near distance of 4 2-4 30 minutes

Time spent for continuous reading

Time spent for continuous reading

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377Indian Journal of Clinical Practice, Vol. 25, No. 4, September 2014

to poor education and lack of health professionals to properly guide them. Students who spent more time for outdoor activities have less chances of development of myopia because they spent less time for near work.

discussion

From our study, it was found that the prevalence rate of myopia among the rural school children was 51.47%. Our study found some relationship between environmental factors like indoor activities (watching TV, computer, mobile phone playing, etc.) and low levels of outdoor activities and unhealthy reading habits with myopia.

It was found that prevalence of myopia was 8.6% among school children in South India. In another study, it was found that the prevalence of myopia increased from 34% in 2,000 to 59% in 2005. In study 11, it was found that 2,317 children in age group of 5-10 years showed a prevalence of 14.02%. In study 13, it was

Figure 5. Frequency of myopia with family history.

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10

12

14

16

18 17

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67

8 8

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No.

of s

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Myopic (No)

Family member wearing spectacle

Myopic (Yes)

Figure 6. Relationship between myopia and reading distance.

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1

21

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15

20

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No.

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Reading distance >30 cm

Reading distance 30 cm

Watching TV distance 3 1-2

Pediatrics


found that 12,800 school children of age group 5-15 years brought out a prevalence of 45.7%. But in our study, we found that the prevalence is 51.47%. The reduction in prevalence of myopia is due to regional variation and due to the study conducted in rural area.1

It was found that there were no significant difference in myopia between girls and boys among Indian school children. In study 10, it was shown that prevalence of myopia in school children was 65.03%. Prevalence of myopia was more in females (60.7%) and less (39.3%) in males. In study 12, prevalence of myopia among girls was more than that of boys. According to our study, there were no significant relationship between sex and myopia (prevalence of myopia among girls is 57.17% and among boys is 42.83%). Our hypothesis is true that the prevalence of myopia is more among girls than boys. But, it was not proved because; now-a-days, boys are more interested in indoor activities like playing mobile games, computer, etc. than outdoor activities.2,3

The prevalence of myopia is 52-60%. It is associated with increasing educational pressure combined with life changes, which have reduced the time children spend outside. In study 2, it was proved that higher levels of outdoor activities were associated with more hyperopic refraction and lower myopia in 12 years old students. According to our study, we found that the prevalence of myopia decreases with increasing levels of outdoor activities. This may be due to higher outdoor activities were associated with more hyperopic refractions and lower myopia. Increased outdoor activities during summer months decrease eye growth in children.4

A study on myopia among school children in India was done by medical students of Al-Ameen Medical College. In the study conducted from 2003 to 2006 among 549 students (279 boys and 270 girls), it was found that prevalence of myopia was 8.6% among school children in South India.1

In a study conducted in Sydney, the relationship between near, mid-working distance and outdoor activities with prevalence of myopia was evaluated. In the study conducted from 2003 to 2005 among 2,367 students, it was proved that higher levels of outdoor activities were associated with more hyperopic refraction and lower myopia in 12 years old students. Students with higher levels of near work and lower levels of outdoor activities had the least hyperopic mean refraction (+0.27 D), 95% confidence interval (CI), 0.02-0.52.2

A study was conducted in Kuala Lumpur; on association between myopia and gender in Indian

school children in Kuala Lumpur children. In this study among 749 students aged between 7-18 years (49.7% boys and 50.3% girls), for right eye, 15.1% of girls are myopic and 16.9% of boys were myopic. For left eye 18.8% girls and 16.45% boys are myopic. So, the prevalence was 16%. It was found that there were no significant differences in myopia between girls and boys among Indian school children.3

A study on Myopia-major health issue among school children in East Asia published by The Lancet; it was found that the prevalence of myopia was 52-60% in school children in East Asia. It was associated with increasing educational pressure combined with life changes, which have reduced the time children spend outside.4

A study on Prevalence of myopia in Taiwanese school children was done by Dept. of Ophthalmology, National Taiwan University. This study was conducted from 2000 to 2005 among school children aged between 16 and 18 years. It was found that the prevalence of myopia increased from 34% in 2000 to 59% in 2005.5

A study on relationship of reading habit and prevalence of myopia was conducted by Dept. of Ophthalmology, Quassim University. In this study undertaken from 2000 to 2003 among 320 students aged 7-12 years, it was found that those who read book at a distance >30 cm for >30 minutes in low illumination and in supine position were more prone to develop myopia. Prevalence was found to be 46%.6

A study on prevalence of myopia in children with family history of myopia by Dept. of Ophthalmology, Singapore University, it was found that children with family history of myopia were more prone to myopia.7

A study on Reading, writing, working on computer or watching television and myopia by Dept. of Ophthalmology, Pomeranian Medical University, Poland among 5,865 school; it was proved that myopia occurs more often in those who read and write >2 hours/day, work 0.8 hours/day on computer and watch TV >2 hours/day.8

In a study on prevalence of myopia in school children by Dept. of Community; National University of Singapore, it was proved that prevalence of myopia was more in the cities than in the countryside. The prevalence of myopia in the city was 19.3% and 6.6% in the countryside.9

In study on prevalence of myopia in primary school children of Qazuin University of Iran by Mohammed

2014

Lowers FPG & HbA1c

Delays Insulin Therapy

3 Dimensional Approach To Win Over Diabetes

Sustained ImprovementIn Glycaemic Control

Pediatrics


Nijad, Shafaq Ali Rahmath and Mohammed Baraka showed that prevalence of myopia in school children was 65.03%. Prevalence of myopia was more in females (60.7%) and less (39.3%) in males.10

conclusion

It was found that the prevalence of myopia in school children of rural community in Kollam was found to be 51.47% in which a group of hidden myopic of 43.1% were discovered. The main risk factors which add to the incidence of developing myopia are reading books at a distance less than 30 cm, reading in supine position and watching TV in low illumination. Higher levels of outdoor activities will decrease the development of myopia. Further studies including other environmental and genetic etiologic factors of myopia are expected.

references

1. Gogate P, Soneji FR, Kharat J, Dulera H, Deshpande M, Gilbert C. Ocular disorders in children with learning disabilities in special education schools of Pune, India. Indian J Ophthalmol 2011;59(3):223-8.

2. Naidoo KS, Jaggernath J. Uncorrected refractive errors. Indian J Ophthalmol 2012;60(5):432-7.

3. Basu M, Das P, Pal R, Kar S, Desai VK, Kavishwar A. Spectrum of visual impairment among urban female school students of Surat. Indian J Ophthalmol 2011;59(6):475-9.

4. Mark A, Jung L, Chintal K. The Lancet Journal 2009;379(2):123.

5. Chen AH, Norazman FN, Buari NH. Comparison of visual acuity estimates using three different letter charts under two ambient room illuminations. Indian J Ophthalmol 2012;60(2):101-4.

6. Mujad F, Sawad M, Jazir A, Al-Malik H. Oman J Ophthalmol 2011;4(2):57.

7. Anamaneni S, Bindu H, Reddy KP, Vishnupriya S. Am J Ophthalmol 2005;4(3):213.

8. Jenny M.Ip, Seang-Mei Saw, Kathryn A. Rose, Ian G M Morgan, Annette. Kifley, Jie Jin Wang, et al. Euro J Sci Res 2006;28(2):174.

9. Mitchell GL, Moeschberger ML, Jones LA, Zadnik K. Br J Ophthalmol 2009;15(2):69

10. Mohammed N, Ali Rahmath S, Mohammed B. Journal of IMA 2007;105(4):169.

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a prevalence study on myopia among school going children in a rural area of south india

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