In the study, published in JAMA Ophthalmology, investigators analyzed data from 21,655 children aged 6 to 8 years who were enrolled in the Hong Kong Children Eye Study between 2015 and 2023. The mean age was 7.31 years and 52.9% of the participants were male.
Led by Ka Wai Kam, MSc, of the Department of Ophthalmology and Visual Sciences at The Chinese University of Hong Kong, the investigators used cycloplegic autorefraction and optical biometry to evaluate refractive astigmatism (RA) and corneal astigmatism (CA). RA was defined as cylindrical refractive error of at least 1 D, while CA was defined as the absolute difference between steepest (K2) and flattest (K1) keratometry of at least 1 D.
The data was categorized into three time periods:
- Prepandemic (2015 to 2019)
- During pandemic (2020)
- Postrestriction (2021 to 2023).
The investigators found that RA prevalence increased from 23.4% between 2015 and 2019 to:
- 24.6% in 2020
- 30% in 2021
- 34.7% in 2022 to 2023.
CA prevalence rose from 59.7% between 2015 and 2019 to:
- 66.9% in 2021
- 64.7% in 2022 to 2023.
The mean cylindrical power of RA increased from 0.70 D between 2015 and 2019 to 0.87 D between 2022 and 2023. Mean cylindrical power of CA rose from 1.24 D in 2015 to 2019 to 1.35 D in 2022 to 2023. The change in CA was associated with an increase in K2 (steepest meridian), which suggested changes in corneal curvature.
After adjusting for age, sex, parental astigmatism, refractive error, and family income, the risk of RA increased by 20% (odds ratio [OR] = 1.20, 95% confidence interval [CI] = 1.09–1.33, P < .001), while the risk of CA increased by 26% (OR = 1.26, 95% CI = 1.15–1.38, P < .001). The pandemic was associated with + 0.04 D increase in RA magnitude and + 0.05 D increase in CA magnitude.
The participants’ daily outdoor time decreased from 1.43 to 1.16 hours, but near work duration increased from 3.33 (2015 to 2019) to 4.91 hours per day (2020 to 2023; P < .001). The investigators noted that prolonged digital device use and reduced outdoor exposure may have contributed to the refractive changes they found.
They also noted that the increase in astigmatism occurred after the surge in myopia, which began during pandemic restrictions, and that RA and CA progression appeared to be independent of myopia development, based on adjusted regression models. Most cases remained as with-the-rule astigmatism, and changes in vertical corneal curvature may have contributed to increased CA.
The investigators cited previous research that “suggested a similar extent in the increase of astigmatism prevalence” as their study; however, they again stressed that the timing of the astigmatism increase in their study came after increases in myopia.
The investigators acknowledged limitationsof their study, including limited generalizability because the study population was predominantly Han Chinese. They also explained that pandemic period definitions may not apply to other regions with different public health responses, and smaller sample sizes in 2022 to 2023 could have affected precision. Parental astigmatism was self-reported and may have introduced potential recall bias.
“We think that the change in corneal curvatures induced by near work takes time to develop,” the study authors wrote. They concluded: “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.”
Disclosures can be found in the published study.