Prevalence of Myopia in School Children of Bangalore Region, Karnataka, India

Introduction

Uncorrected refractive error is the second greatest cause for blindness globally, accounting for distant vision issues in 108 million people.¹ According to World Health Organization, 53 million people globally, including 43% who have refractive problems that have not been corrected suffer from visual impairments.² Majority of blind people in the world reside in India. With prompt treatment, 80 percent of these individuals, or more than 12 million people could avoid going blind. Blindness in Indian children ranges from 16.3% to 37%, even though it can be avoided.³ Myopia is one of the refractive defects that is regarded as a significant global public health issue because, when not fully corrected (also known as uncorrected or undercorrected myopia), it is one of the main causes of visual impairment. The most prevalent ametropia among school children is myopia. Eye strain, diverging and squinting vision and distorted distance vision are all the consequences. The condition can cause blindness in severe situations (progressive myopia).⁴ Myopia prevalence varies significantly around the globe. For example, reports suggest a relatively low frequency in Africa and a larger prevalence in Asia.⁵

Myopia is also understood to be correlated with geographic location and type of community.¹ Studies in rural and urbanized areas are required to produce evidence for early myopia intervention for children in the future, given current knowledge of risk factors of myopia.⁵ A high degree of myopia also raises the chance of permanent vision loss owing to pathological alterations in the retina as well as the chances of developing cataracts and glaucoma. Myopia can have a significant impact on a child’s life, reducing their potential for career and financial security and ultimately resulting in social stigma. Determining the prevalence of myopia in school-age children in both urban and rural settings was the major goal of the current investigation.

Methods

Study design and settings

A cross-sectional study was used for the research. It has been applied in primary and secondary schools in urban and rural communities of Bangalore, Karnataka, India. Six schools in total were chosen for screening depending on the school setting (rural or urban). Three schools were in urban area and three were in rural area. The procedures were compiled considering the ethical guidelines of institutional ethics committee. The updated 2013 Declaration of Helsinki was also followed while conducting the study. Before starting the trial, approval was obtained from the respective school principals. The schools consented only for non-invasive procedures. Additionally, before beginning the procedure, the respective class teachers’ oral approval was sought.

School children aged 5 to 15 years of both the genders, who were willing to participate were included in the study. Children above 15 years of age, children who have had ocular surgeries, and children who had active ocular infection or inflammation during screening were excluded.

Sample size

The RESC protocol approach of estimating a portion of the population with a certain level of relative accuracy was used to determine the sample size.⁶ The formulae was n = Z ² P (1 - P)/d² . An estimate of sample size with a 95% confidence interval was made. The anticipated prevalence was 10%, the precision value was 1%, and the z-score value was 1.96.

Variables

Myopia status, defined as a spherical equivalent objective with refractive error of 0.50 D or worse in both eyes, was the most significant outcome variable of the present study. The sphere and half of the cylinder power were calculated as the spherical equivalent. Age (in years), gender (male or female), and grade level were independent factors (first grade to ninth grade).

Data collection & Ocular examination

There were twelve optometrists on the data collection team. Three days of training on how to do screening and ocular examinations was conducted for the study team. The ocular examination comprised measures of the patient’s near- and farsightedness, as well as the values for their current glass prescription and their objective and subjective refraction. The participants were asked to read monocularly while optometrists tested their visual acuity at a distance of four meters using a retro-illuminated logarithm of the minimum angle of resolution (log MAR). Children who could not correctly read the top line at a distance of four meters were brought to them until they could. Additionally, a participant with pin-hole vision who could not read 0.2 lines or more had their performance noted. All students had their right and left visual acuities tested. Children who presented wearing glasses had their visual acuity assessed both with and without their glasses (uncorrected visual acuity). The N-notation chart was used to measure near visual acuity.

Participants were unable to read 0.2 lines of visual acuity, and those who could read more than that had their refractive errors assessed using retinoscopy. Dioptre values were used to record the net value. Children whose uncorrected visual acuity was 0.2 lines or worse in both eyes underwent subjective refraction by optometrists, and those whose vision improved after refractive surgery were given glasses.3 We also verified children’s current prescriptions, which were determined by measuring the power of children’s spectacles with known trial lenses.

Statistical analysis

Microsoft Excel was used to enter the data. SPSS 20 was used to conduct the statistical analysis. For the normalcy test, data were examined. Parametric statistical tests were used since the data were normally distributed. To verify the proportion, the z-cal test was used. The proper data presentation methods included number (percent) or mean SD. Myopia’s severity and prevalence were described (95 percent Confidence Interval-CI). Statistical significance for these tests was defined as a p-value of 0.05 or lower.

Results

The study involved a total of 3038 children (6076 eyes) from six different schools. Among the six schools included, three were government (rural) and three were private (urban) schools. It was intended to have almost equal number of children included from both urban and rural schools. In total, 1476 children from rural schools and 1562 from urban schools were assessed. The age range of children included in the study was 5 to 15 years, with a mean age of 11.21±3.1 years. Equal percentage of boys and girls comprised the sample. According to several criteria, Table 1 illustrates the prevalence of myopia in school-aged children.

The prevalence of myopia was found to be 4% in the total population. Of 6076 eyes screened, 4% (241) were myopic. Of 2952 eyes screened in the rural population, 3.18% (94) were myopic and of 3124 eyes screened in the urban population, 4.71% were myopic (Figure 1). A statistical significant difference (p=0.001) existed in myopia between urban and rural school children. Myopia was significantly lower in rural school children compared to urban school children.

No significant difference was observed in the prevalence of myopia in both the genders (54% in girls vs 46% in boys, p=0.08). Prevalence of myopia in relation to different age groups was as follows: 13.2% in 5 to 8 years (p=<0.001), 42.7% in 9 to 12 years (p=0.004), 43.9% in 13 to 15 years (p=0.001).

Table 2 explains the prevalence of myopia among different age groups of school-going children.

Table 3 shows the distribution of children by myopic category among myopic children as well as the visual acuity in the better eye among myopic and total study children. In myopic children, the prevalence of moderate and severe vision impairment was 4.15 percent, 1.25 percent, and 0.12 percent overall. Additionally, it shows how myopia levels are distributed among myopic children. Majority of the children (60%) had mild myopia, followed by intermediate myopia (31.5%), while 8.5% who had extreme myopia.

As per our screening result, among 3038 participants, 2925 were emmetropes, 329 were ammetropes. Among these 329 participants, 141 were unaware of the refractive status of their eyes. Out of 141, 79 were from urban and 62 were from rural areas.

Discussion

According to the results of the vision screening conducted in the present study, school age children constitute a particularly high-risk category for refractive errors. School children’s vision screenings would help identify the correctable cause of impaired vision, particularly refractive errors, and can also aid in reducing long-term visual disability.

A child’s education and development can be significantly impacted by visual impairment. To remove this quickly curable source of visual impairment, a successful plan must be established.⁷ If a particular environmental and inherited element is selective in metropolitan Asian locations that may result in high prevalence rates of myopia, the fascinating phenomena may emerge. One of the most commonly mentioned risk factors for myopia is being close to your place of employment, and several observations lend credence to this theory. Environmental factors, such as increasing level of competition in the education system, may have had an increasing effect in recent years.⁸

Myopia was more common in urban than rural school children of Bangalore region in Karnataka. According to a study conducted in the Middle East by Amruta S et al., urban residents had a higher prevalence of myopia than rural residents. It might be a result of environmental factors that contribute to the advancement of myopia, such as urban development and academic grade level.⁹ Brighter light may slow down the progression of myopia by either causing the pupil to constrict, reducing visual blur, or inducing the release of dopamine from the retina. Axial elongation has previously been shown to be inhibited by dopamine.¹⁰

The study by Ishfaq Ahmed, Seema Mian et al in Kashmir concluded that females are more prone to myopia than males. This could be due to the limitation i.e., visual acuity examination in the rural area done by teachers of the schools included.¹¹ In the current study, as the gender ratio was similar, no statistically significant difference was observed for myopia in both the genders. So as per this study, males and females are equally prone to myopia.

Myopia was more common in children aged 8 to 12 years compared to 5 to 8 year old and 13 to 15 year old children. The average myopic advancement rate was found to be fastest in junior high school students (aged 13 to 15 years) and to be approximately 0.45 D/year in urban regions and 0.28 D/year in rural areas, according to a study conducted in Taiwan by Yung Feng Shih et al. Myopic growth in boys and girls reduced to 0.17 D/ year and 0.33 D/year, respectively, in senior high school (aged 16 to 18 years).¹²

Regarding the importance of vision screening for children during the school years, as well as how frequently it should be done, it has been suggested that children in the age range of 3 to 5 years should be tested upon entering school and then every three years after that. However, no empirical evidence was provided to back up this suggestion. Unusually, secondary school-aged children have major, undiagnosed vision disorders. Myopia can start developing in adolescence too, and this can have an impact on schooling as kids get ready for tests.

The main justification for vision screening in schools, especially for older kids, seems to have been the potential for educational disadvantage. Due to a drop in vision screening in secondary schools, it has unfortunately been impossible to determine how many kids with impaired visual acuity may have gone unnoticed.

By collecting the PGP power from the participants who were already wearing correction, we were able to examine the efficacy of screening from our study. Among the total participants included in our study, 329 were emmetropes, while 141 subjects had no idea they had refractive power [Figure No. 4 depicts this].

This shows that children may not be aware of their problem and thus screening in schools for visual disabilities is very important for early detection and treatment.

It will also be possible to detect any children who have not yet been recognized for myopia by raising awareness of the condition through screening and potential preventive measures. The WHO has advised school pupils to receive refractive procedures and vision screenings. In India, urban and rural areas appear to have different levels of uncorrected refractive error and different root causes. Because of this, refractive services should be modified to the conditions in different parts of developing countries.

In current scenario where the usage of gadgets and computers is increased, associations between screen exposure and prevalent or incident myopia, an increased myopic spherical equivalent, and longer axial length are reported. Smart device screen time alone (OR 1·26) was significantly associated with myopia.¹³

Conclusion

Urban school children in Bangalore region of Karnataka, India, showed a higher prevalence of myopia compared to rural school children. Environmental factor such as digital screen exposure may be a significant contributor to the advancement of myopia along with urban growth and academic grade level. It is important to determine the root cause for the increasing prevalence of myopia and the impediments to myopia services. It is advised that schools in both urban and rural places conduct screening of eyes for visual disabilities.

Conflicts of interest

There are no conflicts of interest