Higher Astigmatism Rates Found in Children after COVID-19 Pandemic

A recent population-based cross-sectional study examining all primary schools in Hong Kong’s Education Bureau revealed a substantial increase in prevalence and severity of refractive and corneal astigmatisms in the wake of the COVID-19 pandemic.1

Ka Wai Kam, MSc, University of Hong Kong, and colleagues examined 9 years of data from 2015-2023, covering the pre-, mid-, and post-pandemic periods (2015-19, 2020, and 2021-23, respectively). Children aged 6-8 years underwent ocular exams, and parents completed questionnaires regarding lifestyle and environmental risk factors.

“Given the high prevalence of astigmatism, the potential impact of higher degrees of astigmatism may warrant dedicated efforts to elucidate the relationship between environmental and/or lifestyle factors, as well as the pathophysiology of astigmatism, in order to preserve children’s eyesight and quality of life,” Kam and colleagues wrote.1

The study was initially proposed in response to evidence of increased rates of myopia among schoolchildren. Astigmatism’s direct connection to myopia is well documented, and the latter rose sharply in children at the beginning of the COVID-19 pandemic, when lockdown measures were implemented.2

Investigators took a randomized sampling frame by stratifying all primary schools registered with the Education Bureau into 7 main groups. Potential participants with ocular trauma or congenital ocular diseases were excluded. In total, the study examined 21655 children: 11464 (52.9%) boys and 10191 (47.1%) girls.1

Examinations were conducted with an autorefractor after a cycloplegic regimen. At least two cycles of eye drops were administered, followed by two drops of cyclopentolate, 1% and tropicamide, 1% at five minutes apart during the first cycle, ten minutes after the second, and 30 minutes after the second if pupil size was less than 6.0 mm or the pupillary light reflex was still present. Flattest keratometry (K1) and steepest keratometry (K2) were measured with a noncontact partial-coherence laser interferometry.1

Before the COVID-19 pandemic in Hong Kong, the prevalence of refractive astigmatism (RA) of at least 1.0 diopter (D) was 21.4%. The data revealed that, during COVID-19, RA prevalence increased to 24.6% (difference, 1.1%; 95% CI, -1.4% to 3.7%). After restrictions were removed, prevalence continued to increase up to 30% (difference, 6.5%; 95% CI, 4.7% to 8.3%) in 2021 and 34.7% (difference, 11.2%; 95% CI, 8.2% to 14.3%) in 2022-2023.1

The prevalence of corneal astigmatism (CA) of at least 1.0 D in children was 59.7% pre-COVID-19. Kam and colleagues discovered an increase up to 66.9% (difference, 7.2%; 95% CI, 5.3%-9.1%) in 2021 that was maintained at 64.7% (difference, 5.0%; 95% CI, 1.8%-8.1%) in 2022-23. Again, a consistent increase was exhibited across all subgroups. A 20% increase to risk of RA (odds ratio [OR] 1.20; 95% CI, 1.09-1.33; P <0.001) and a 26% increase to risk of CA (OR, 1.26; 95% CI, 1.15-1.38; P <0.001) were associated with the pandemic.1

The pandemic was also linked to a 0.04 D increase in the magnitude of RA (95% CI, 0.02-0.07; P < .001), and 0.05 D in the magnitude of CA (95% CI, 0.02-0.08; P < .001).1

Additionally, results indicated a K1 decrease from 42.91 D in 2015-19 to 42.85 D in 2022-23 (difference, -0.06 D; 95% CI, -0.15 to 0.03 D), while K2 values increased from 44.15 D in 2015-19 to 44.2 D in 2021-23. Investigators indicated that increasing astigmatism resulted in steeper corneal curvature located almost entirely within the vertical meridian. The team suggests that these changes may explain some of the progression of CA.1

Both myopia and astigmatism can be directly connected to screen usage and near-work. Notably, restrictions put in place by the pandemic resulted in a switch from in-person to virtual classes, which required children to spend longer hours viewing electronic devices and engaging in intensive near work.2

“Based on the previous reports that astigmatism and myopia are highly correlated and that astigmatism may be a byproduct of myopia, the findings in our present study provided additional data on the corneal component, which is a major contributor to RA. We think that the change in corneal curvatures induced by near work takes time to develop.”1

References

1. Kam KW, Shing E, Zhang Y, et al. Prevalence and severity of astigmatism in children after COVID-19. JAMA Ophthalmology. Published online March 20, 2025. doi:10.1001/jamaophthalmol.2025.0205

2. Zhang XJ, Zhang Y, Kam KW, et al. Prevalence of myopia in children before, during, and after covid-19 restrictions in Hong Kong. JAMA Network Open. 2023;6(3). doi:10.1001/jamanetworkopen.2023.4080