Astigmatism trends in adults of Hong Kong from 2015 to 2024: The Hong Kong Children Eye Study

Background/aims To investigate temporal trends in refractive and corneal astigmatism (CA) in adults and examine their association with the COVID-19 pandemic. Methods This population-based cross-sectional study included adults (≥18 years) recruited from parents participating in the Hong Kong Children’s Eye Study who underwent comprehensive ocular examinations at two academic centres (2015–2024). Refractive error of the worse eye and corresponding CA were measured using an autorefractor and optical biometry without cycloplegia. Age-standardised prevalence was calculated annually. Logistic regression assessed associations between the pandemic period and astigmatism, adjusting for age, sex, axial length and spherical equivalent. Results A total of 29 583 adults (mean age 40.6±5.6 years; 35.3% men) were included. Age-standardised prevalence of refractive astigmatism (RA) increased from 41.7% in 2015 to 46.2% in 2024 (p=0.002) and CA from 45.0% to 52.9% (p=0.002). Compared with 2015, the adjusted odds of RA in 2024 increased by 52% (OR 1.52, 95% CI 1.30 to 1.76; p=9.34×10 −8 ), and CA by 47% (OR 1.47, 95% CI 1.27 to 1.71; p = 2.38×10 −7 ). Mean refractive and CA increased by 0.11 D and 0.14 D, respectively. A shift towards moderate and severe astigmatism was observed. CA correlated strongly with K2 (β=0.891, p<0.001). Conclusions The prevalence and severity of astigmatism in adults increased following the COVID-19 pandemic, independent of axial length and spherical equivalent. Findings suggest corneal changes, especially along the steep meridian, may underlie this trend and warrant further investigation into environmental and lifestyle factors.