Abstract
Background
To investigate the prevalence and risk factors for astigmatism in 7-19-year-old students in **njiang, China.
Methods
A school-based, cross-sectional study was conducted on students who underwent refraction examination in **njiang, China, between May and December 2019. The prevalence of astigmatism was determined. Astigmatism was defined as cylinder power (C) ≤-0.75 D, undefined astigmatism as ≤-1.50 D, and high astigmatism as C ≤-3.00 D. Astigmatism types were: against-the-rule astigmatism (maximum refraction of the main meridian in 180° ± 30°), with-the-rule astigmatism (maximum refraction of the main meridian at 90°±30°), and oblique astigmatism (all other cases).
Results
Of the 71,838 students examined (51.0% boys, 7 − 19 years old), 25,945 (36.1%, 95%CI: 35.52−36.68%) had astigmatism and 1267 (1.8%, 95%CI: 1.07−2.53%) had high astigmatism. The prevalence of astigmatism was greater in Han individuals (39.6%) compared with the Hui (34.0%), Kazakh (34.0%), Kyrgyz (32.1%), and Uyghur (26.4%) populations. Among the 25,945 students with astigmatism, 19,947 had with-the-rule astigmatism (76.9%), 3405 had against-the-rule astigmatism (13.1%), and 2593 had oblique astigmatism (10.0%). Multivariable logistic regression analysis showed that ethnicity (Han individuals more susceptible), male gender, age, and refractive errors (myopia and hyperopia) were independently associated with astigmatism, high astigmatism, and with-the-rule astigmatism (all P < 0.05).
Conclusions
The prevalence of astigmatism among children and adolescents in **njiang was 36.1%, including 1.8% of high astigmatism. In this population, astigmatism was mainly of the with-the-rule astigmatism type (76.9%). Han ethnicity, male gender, and myopia or hyperopia were independently associated with a high risk of astigmatism.
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Background
Astigmatism is a refractive state in which the refractive power of the eye differs at different meridians, creating two focal lines and a minimal diffuse spot [1, 2]. In recent years, the rising annual global prevalence of astigmatism in children and adolescents has become an important clinical and public health concern. Uncorrected astigmatism significantly reduces visual function [1] and can significantly affect visual development in childhood, leading to amblyopia [2]. Previous studies reported a significant correlation between astigmatism and myopia development based on animal models and observations in longitudinal trials involving children [3, 4]. Therefore, early detection and treatment of astigmatism in children and adolescents is particularly important.
Currently, the pathogenesis of astigmatism in children and adolescents is unclear, and genetics, extraocular muscle tone, eyelid pressure, visual feedback, and environmental pollution have been implicated [5]. In addition, studies identified young age, severe refractive error (myopia or hyperopia), maternal smoking during pregnancy [6], eyelid flaps [33]. Other studies have also found correlations between high spherical powers and with-the-rule astigmatism, with against-the-rule astigmatism increasing with decreasing spherical power [34]. Studies in Taiwan and Iran [22, 23] also confirmed the relationship between astigmatic axis position and spherical refractive error. In the above multivariable analysis, we also found that myopic or hyperopic individuals were more likely to develop astigmatism in the against-the-rule and oblique astigmatism than in emmetropia. Further longitudinal studies are needed to evaluate the causal relationship between the variation of the astigmatic axis and the degree of refractive error.
The strengths of this study are as follows. First, the sample size was large, including many regions and representative ethnicities. Secondly, there are relatively few reports on astigmatism prevalence, especially in Western China, a gap closed by this study. In addition, data for several diagnostic criteria were provided in this study, which could be compared with other investigations. However, there were also some limitations in this study. First, non-cycloplegic autorefraction reduces the accuracy of the diopter number. Secondly, it was a cross-sectional study, which cannot determine the causal relationships, e.g., between age and refractive state and between astigmatism prevalence and astigmatic axis, in children and adolescents. Further longitudinal cohort studies are required to accurately and scientifically analyze astigmatism data and provide an effective scientific basis for the prevention and control of astigmatism.
Conclusions
The above large-scale school survey showed that astigmatism was relatively high among children and adolescents in **njiang, China, with astigmatism mainly being with-the-rule astigmatism, which increased with age and education level. The risk of astigmatism, high astigmatism, and with-the-rule astigmatism was increased in the Han ethnicity, males, and myopia or hyperopia cases. The possible causal relationships of refractive error (myopia or hyperopia), ethnicity, astigmatism, and the astigmatic axis must be further confirmed by multicenter longitudinal studies with large sample sizes.
Data availability
All data generated or analyzed during this study are included in this published article and its supplementary information files.
Abbreviations
- SE:
-
Spherical equivalent refraction
- C:
-
Cylinder power
- D:
-
Diopter
- NA:
-
Not available
- MEPEDS:
-
Multi-Ethnic Pediatric Eye Disease Study
- CI:
-
Confidence Interval
- VIP:
-
Vision in Preschoolers
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Acknowledgements
We thank the **njiang Uyghur Autonomous Region Primary and Secondary School Health Care Guidance Center for personnel support. We thank International Science Editing (http://www.internationalscienceediting.com) for editing this manuscript.
Funding
This research received no specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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Contributions
Yan Wang and **gyu Mu contributed to the design and conduct of the study, data collection and management, and data interpretation, and wrote the whole paper. Yunxian Gao and Yong Zhao contributed to data interpretation and critically revised the manuscript. Zhen Wang performed the statistical analysis and critically revised the manuscript. Wei Gong guided and participated in data statistical analysis and interpretation. Yining Yang contributed to the design and conduct of the study, and data collection, and critically revised the manuscript. **aolong Li, Han Qin, Batima·Mulati contributed to the design and conduct of the study, data collection, and critically revised the manuscript. All authors have read and approved the manuscript.
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This study passed the ethical review of the Traditional Chinese Medicine Hospital of **njiang Uyghur Autonomous Region (Ethics approval No 2019XE0151). All participants and their parents or guardians provided signed informed consent. All methods were performed in accordance with the relevant guidelines and regulations.
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Wang, Y., Mu, J., Yang, Y. et al. Prevalence and risk factors for astigmatism in 7 to 19-year-old students in **njiang, China: a cross-sectional study. BMC Ophthalmol 24, 116 (2024). https://doi.org/10.1186/s12886-024-03382-0
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DOI: https://doi.org/10.1186/s12886-024-03382-0