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 Table of Contents    
ORIGINAL ARTICLE
Year : 2018  |  Volume : 11  |  Issue : 3  |  Page : 232-236  

Changing trends in myopia among schoolchildren in Oman: Screening information over 11 years


1 Department of Research, King Khalid Eye Specialist Hospital, Riyadh, Saudi Arabia
2 Department of Noncommunicable Disease Control, Directorate General of Health Affairs, Ministry of Health, Muscat, Oman

Date of Web Publication29-Oct-2018

Correspondence Address:
Dr. Rajiv Khandekar
Department of Research, King Khalid Eye Specialist Hospital, P. O. B: 7191, Riyadh 11462
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ojo.OJO_55_2017

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   Abstract 


PURPOSE: The purpose of this study is to evaluate the changing trends in myopia over an 11-year period among Omani schoolchildren.
METHODS: This retrospective study took place from January to June 2012. National vision screening data from 1999 to 2010 were reviewed for information concerning all children in the fourth, seventh, and tenth grades of Omani public schools. Changes in the rate of myopia by gender, grade, severity, and governorate were evaluated.
RESULTS: Among 397,430 fourth-grade students, the prevalence of myopia was 2.44%. In contrast, the prevalence of myopia among 533,003 and 461,307 children in the seventh and tenth grades, respectively, was 4.41% and 7.36%. Compared to 2002, the rate of myopia in 2010 was 1.43% higher for fourth-grade students (P < 0.001). Myopia prevalence rates among seventh-grade students increased by (5.36–3.36 = 2.0) 1.11% between 1999 and 2010, but declined by 7.62% versus 6.34% = 1.28% between 1999 and 2010 for seventh- and tenth-grade students, respectively (P < 0.010 and <0.001, respectively). The risk of myopia in the fourth, seventh, and tenth grades was significantly higher for females in 2002 and 2010 (P < 0.001). The regional variation of myopia was also significant (χ2 = 495; P < 0.001). Among seventh- and tenth-grade students in 2010, the ratio of children with mild-to-moderate/severe myopia was 1.5:1 and 1:2.7, respectively.
CONCLUSION: Although the rate of myopia increased with grade, the trend over time suggests that myopia affected more children at a younger age. Female students had a significantly higher risk of myopia.

Keywords: Children, myopia, Oman, refractive errors, vision


How to cite this article:
Khandekar R, Gogri U, Al-Harby S. Changing trends in myopia among schoolchildren in Oman: Screening information over 11 years. Oman J Ophthalmol 2018;11:232-6

How to cite this URL:
Khandekar R, Gogri U, Al-Harby S. Changing trends in myopia among schoolchildren in Oman: Screening information over 11 years. Oman J Ophthalmol [serial online] 2018 [cited 2018 Dec 12];11:232-6. Available from: http://www.ojoonline.org/text.asp?2018/11/3/232/244331




   Introduction Top


Myopia in schoolchildren is a major public health problem in certain regions of the world.[1] Many countries now incorporate vision screening programs for schoolchildren based on the joint recommendations of the World Health Organization and the International Agency for the Prevention of Blindness.[2],[3] The global rise in myopia among schoolchildren is partially due to rapid urbanization and the greater number of near-distance and indoor activities available for entertainment.[4],[5],[6] Countries with a rising prevalence of myopia will soon require specific resources to treat the increased number of affected children; in addition, the allocation of these resources will need to be periodically revised to adapt to changes in the rate of myopia over time. Countries with long-standing vision screening programs and programs for managing refractive errors can provide data on changing trends of myopia in children.

In Oman, education and health-care services are provided free of charge to the local population and attendance at primary and preparatory schools is mandatory. Since 1990, national eye care and school health program developed by the Ministry of Health operates in coordination with the Ministry of Education to improve the overall health of schoolchildren in all governorates of Oman; this initiative has received international acclaim as a model for other countries in the Eastern Mediterranean Region.[3] Students aged 6–7, 9–10, 11–12, and 16–17 years old undergo annual vision and eye examinations in the first, fourth, seventh, and tenth grades, respectively. These examinations are performed by trained school nurses using illiterate E or LogMAR ophthalmological charts held at a distance of 3 m away. Children with clear vision only at close range (≤0.9 m from the chart) are re-examined with both eyes open; if their eyesight does not improve, they are considered to have defective vision and referred to a school optometrist. Students with adequate vision but who have strabismus or asthenopia are also referred for review. Fogging techniques are used to rule out accommodative spasms. For refractive errors, students with suspected myopia undergo a dynamic refraction procedure, and those with hyperopia undergo a cycloplegic refraction procedure 30 min after the administration of one drop of 1% homatropine. These children are then re-examined 48 h later to ensure that measurements have not been skewed by accommodation adjustments and that their pupils have returned to normal. Subsequently, prescriptions for any necessary spectacles or visual aids are presented to the child's schoolteachers or principal for delivery to the child and to ensure their regular use.

Data from this program are collected annually and analyzed at the national and governorate levels.[7],[8] This study aimed to review this vision screening data to evaluate trends in myopia among schoolchildren over an 11-year period. The effects of gender, governorate, and severity of myopia on overall rates of myopia were also considered.


   Methods Top


This retrospective study was performed from January to June 2012 and involved a review of national vision screening data from 1999 to 2010. All children in the fourth, seventh, and tenth grades who attended schools under the aegis of the Ministry of Education and who underwent vision screening between 1999 and 2010 were included in the study. An Oracle database maintained by the School Health Department, Directorate General of Health Affairs and the Health Information Department, Directorate General of Health Planning of the Ministry of Health in Muscat, Oman, collected the data for each school. Gender, governorate, vision in each eye, refractive status, and the final prescription for each student were recorded.

Data were analyzed using the Statistical Package for the Social Studies (SPSS), Version 11 (IBM Corp., Chicago, Illinois, USA). Percentages of myopic children each year were calculated by grade, gender, and governorate and 95% confidence intervals (CIs) were determined for prevalence. A Microsoft Excel spreadsheet, Version 2010 (Microsoft Corp., Redmond, Washington, USA), was used to plot graphs to compare the prevalence of myopia according to grade and year of screening.

The National Eye Health Care Committee of Oman provided ethical approval for this study.


   Results Top


Overall, there were 397,430 fourth grade, 533,003 seventh-grade students, and 461,307 tenth-grade students screened through the national vision screening program during the study. Vision screening of the fourth-grade students began for the first time in 2002; as such, data for the fourth-grade students were from 2002 to 2010. The prevalence of myopia was 2.44% (95% CI 2.39–2.49), for fourth-grade students, 4.41% (95% CI: 4.36–4.47) for seventh-grade students, and 7.36% (95% CI: 7.28–7.44) for tenth-grade students over the entire study period.

In 2002, there were 865 myopic children out of 43,434 4th year students (1.99%; 95% CI: 1.86–2.12). In 2010, 2409 children were myopic out of 70,455 4th year students (3.42%; 95% CI: 3.29–3.55). Thus, there was a significant rise in the prevalence of myopia over 9 years (1.43%; odds ratio [OR]: 1.74, 95% CI: 1.61–1.89; P < 0.001). In 1999, there were 1479 children with myopia among 44,063 seventh-grade students (3.36%; 95% CI: 3.19–3.52) compared to 1908 myopic children among 35,587 seventh-grade students in 2010 (5.36%; 95% CI 5.13–5.60). This rise in myopia prevalence over 11 years was significant (2%; OR: 1.63, 95% CI: 1.52–1.75; P < 0.001). In 1999, there were 2322 children with myopia among 30,464 tenth-grade students (7.62%; 95% CI: 7.32–7.92). In 2010, there were 2,613 children with myopia among 41,244 tenth-grade students (6.34%; 95% CI: 6.10–6.57). This decline in the prevalence over 11 years was significant (−1.28%; OR: 1.29, 95% CI: 1.15–1.29; P < 0.001). [Figure 1] shows the prevalence of myopia by year for fourth grade, seventh grade, and tenth grade students. The trend lines suggest that the prevalence of myopia increased among fourth- and seventh-grade students over time; however, the prevalence of myopia among tenth-grade students declined over time.
Figure 1: Myopia rates among (a) 397,430 fourth grade students, (b) 533,043, seventh-grade students and (c) 461,307 tenth grade Omani students by year of screening. The X-axis denotes the year of vision screening. Y-axis denotes rates (%) of myopia among Omani students year. The value next to the red square shows rate of myopia and upper and lower limits of the line denote 95% confidence interval. The thin line shown across the graph is the trend line depicting rising trend for fourth- and seventh-grade students and declining trend in tenth-grade students

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Gender-specific myopia rates were calculated from 2002 onward, as no gender-specific data were available for previous years. Of the 22,107 males in fourth grade in 2002, 369 were myopic 369/22107 = 1.67 and not 0.02 (1.67%); in comparison, there were 496 myopic females 496/21327 = 2.33 and not 0.02 (2.33%) out of 21,327 female fourth-grade students. In 2010, there were 1046 myopic males (2.90%) out of 36,053 male fourth-grade students, while there were 1,363 myopic females (3.96%) out of 34,419 (36,053 + 34,419 = 70455 fourth-grade female students. The risk of myopia was significantly higher among female fourth-grade students in both 2002 and 2010 (OR: 1.40, 95% CI: 1.22–1.61; P < 0.001 and OR: 1.38, 95% CI: 1.27–1.50; P < 0.001, respectively).

In 2002, there were 1,000 myopic males (4.03%) out of 24,837 male seventh-grade students and 1245 myopic females (6.18%) out of 20,133 female seventh-grade students. In 2010, there were 817 myopic males (4.57%) out of 17,877 male seventh-grade students and 1091 myopic females (6.16%) out of 17,710 female seventh-grade students. The risk of myopia was significantly higher among female seventh-grade students in both 2002 and 2010 (OR: 1.36, 95% CI: 1.25–1.48; P < 0.001 and OR: 1.37, 95% CI: 1.25–1.50; P < 0.001).

In 2002, there were 1,789 myopic males (9.88%) out of 18,116 male tenth-grade students and 2711 myopic females (15.27%) out of 17,749 female tenth-grade students. In 2010, the gender-specific information of Muscat governorate was not available. There were 1245 myopic males (5.75%) out of 21,665 male tenth-grade students and 1669 myopic females (8.52%) out of 19,579 female tenth-grade students. The risk of myopia was significantly higher among female tenth-grade students in both 2002 and 2010 (OR: 1.44, 95% CI: 1.32–1.48; P < 0.001 and OR: 1.53, 95% CI: 1.42–1.65; P < 0.001).

There were 25,035 myopic children among the 533,003 seventh-grade students (4.70%) and 37,964 myopic children among the 461,307 tenth-grade Omani children (7.90%) between 1999 and 2010. Their distribution by governorate is shown in [Table 1]. The regional variation of myopia was significant (χ2 = 495, P < 0.001).
Table 1: Distribution of seventh- and tenth-grade Omani students with myopia by Governorate from 1999 to 2010

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Of the 1908 cases of myopia among seventh-grade students in 2010, 1145 had mild myopia, 675 had moderate myopia, and 88 had severe myopia. The ratio of children with mild-to-moderate/severe myopia was 1.5:1. Among 2613 tenth-grade myopic students in 2010, 736 children had mild myopia, 1550 had moderate myopia, and 426 children had severe myopia. The ratio of children with mild-to-moderate/severe myopia was 1:2.7. Children with severe myopia were referred to eye care services for further management.


   Discussion Top


The current study presents insights into recent trends in myopia among schoolchildren in Oman. As education is free and attendance is mandatory at primary and preparatory schools in Oman, the findings of this study can be considered representative of national trends in pediatric myopia. Myopia prevalence in Omani students increased with grade. While rates of myopia decreased slightly for tenth-grade students over the 11-year period, there was an increased prevalence of myopia with time for fourth- and seventh-grade students. An increased prevalence of myopia has also been reported in studies from Finland and Hong Kong.[9],[10] The increase in myopia prevalence observed among younger students in the present study could be due to children spending an increased amount of time doing schoolwork or performing indoor activities such as watching television or playing video games; in Oman, 96% of households in urban areas have TV compared to 84% of households in rural areas, allowing children easy access.[11] In addition, the extremely hot weather during the majority of the year may further encourage children to remain indoors. An increase in near-work activity and a lack of outdoor activities can stimulate the development and progression of myopia.[5],[6],[12] Among children and adolescents, poor physical development has also been linked to myopia; the increased prevalence of myopia seen in the current study may, therefore, be linked to anthropometric parameters.[13] Further research in this field is recommended.

The prevalence of myopia in the overall cohort of the current study was higher in the tenth grade, intermediate in the seventh grade and lowest in the fourth grade. However, there was an increased prevalence of myopia among fourth- and seventh-grade students over time in the current study. This suggests that myopia seems to be affecting more children at younger ages. Fan et al. reported a higher prevalence of myopia among 11-year-old schoolchildren compared to children under 7 years old in Hong Kong.[10] This could perhaps be due to more frequent time spent engaged in outdoor activities among children of older age groups; Dirani et al. found that higher rates of total outdoor activity were significantly associated with fewer cases of myopia among teenagers in Singapore.[14]

Overall, in just over a decade, >0.55 million Omani children with myopia were detected through the national vision screening program and referred to ophthalmic services for further management. This initiative may serve to address and reduce the national prevalence of childhood blindness from avoidable causes such as myopia. However, the high rate of myopia observed among Omani schoolchildren indicates that pediatric eye care and vision aid industries should plan their marketing and manufacturing strategies accordingly to meet increased demand in the near future. Moreover, myopia was found in high percentage of tenth-grade students, regardless of year of screening; these adolescents may be potential candidates for contact lenses or refractive surgery once they become adults.

In the current study, female students in all three grades were more frequently myopic compared to males. Czepita et al. and Yang et al. also noted similar differences in myopia between genders among 6–18-year-old schoolchildren.[15],[16] Due to the local culture in Oman, participation in outdoor activities among females is lower in comparison to males, which could explain the higher rates of myopia seen among Omani female students.

The local Omani population is comprised of three different groups: African migrants, Baloch migrants, and native Omanis.[17] Marked variation in the prevalence of myopia in different governorates within Oman was observed in the current study; this may be because many of the interior governorates in Oman contain tribes which differ ethnically from the local populations of southern and eastern governorates. Although it is difficult to differentiate children based on their Kabila or tribe, further studies are recommended to review trends in myopia by ethnic subpopulation. Rudnicka et al. also reported ethnic differences among children with myopia in the UK.[18]

The main strength of the current study was that it included national data on myopia collected in a standardized manner. However, the study was subject to some limitations. The previous research has indicated differences between genders and among rural and urban subpopulations with regards to different rates of myopia and myopic progression.[5],[15],[16] However, gender-segregated data were not available for 1991–2001. Moreover, data from Muscat governorate were incomplete for 2010, and thus the data could not be analyzed according to urban or rural location. Genetic factors can also influence the early onset or increased severity of myopia.[19],[20] Unfortunately, the current study reviewed data from children between 9 and 17 years old; hence, gathering data on congenital myopia was difficult. In addition, data on severe myopia (>6 D) were not available. Further studies are suggested to confirm the role of familial traits in the prevalence and severity of myopia among Omani children.


   Conclusion Top


Overall, myopia rates among Omani schoolchildren increased with grade. However, the trend over time over the 11-year period indicated that younger students were more frequently affected by myopia. Female students had a significantly higher risk of myopia compared to males. There were significant differences in myopia rates according to governorate. Underlying causes of myopia should be identified and addressed so as to reduce the public health effects of this condition. Omani children once labeled as myopic may be assessed more frequently.

Acknowledgment

The results of this study were presented at the National Eye Healthcare Meeting to governorate representatives, and public health initiatives were recommended. The authors would like to thank the Department of School Health & Eye Health Care, Directorate General of Health Affairs, Ministry of Health for supporting this research. In addition, the contributions of H. Dass, O. Ahmed, N. Sarvanan, P. Satheesh, B. Lilamani, S. Karunanithy, M. Ahmed, M. Pathan and R. Gupta was invaluable.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Rudnicka AR, Owen CG, Nightingale CM, Cook DG, Whincup PH. Ethnic differences in the prevalence of myopia and ocular biometry in 10- and 11-year-old children: The child heart and health study in England (CHASE). Invest Ophthalmol Vis Sci 2010;51:6270-6.  Back to cited text no. 18
    
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