Astigmatism profile in the elderly population: Tehran Geriatric Eye Study.

Purpose: To determine the prevalence of astigmatism and its associated factors and examine astigmatism symmetry patterns in an elderly population.

Study Design: Population based cross-sectional study.

Methods: The present population-based cross-sectional study was conducted on an elderly population above 60 years of age in Tehran, Iran in 2019. The sampling was done using the stratified multistage random cluster sampling method. All study participants underwent a complete optometric examination and slit-lamp biomicroscopy.

Results: The prevalence of astigmatism higher than -0.50, -1.00, and -2.00 D was 83% (95% CI: 81 -84), 52 % (95% CI: 50 -54), and 19% (95% CI: 17-20), respectively. These prevalence was 79%(95% CI: 77-81), 46(95% CI: 44-49) and 14(95% CI: 13-16) in subjects without a history of ocular surgery, respectively. Based on cylinder power worse than -1.00 D, 10% (95% CI: 9-12), 20% (95% CI: 18-22), and 21% (95% CI:19-23) of study participants had with the rule, against the rule, and oblique astigmatism, respectively. According to the results of the multiple regression model, male gender, older age, low education level, pure posterior subcapsular cataract, pseudophakia, and myopia were independent factors associated with astigmatism. The prevalence of anisorule astigmatism was 57 % (95% CI: 56-59), the most common anisorule astigmatism was against the rule-oblique type with a prevalence of 36% (95% CI: 34-38).

Conclusion: The prevalence of astigmatism was high in the elderly population of Tehran. More than half of the participants in this study had anisorule astigmatism, and against the rule-oblique combination was more prevalent than other types. A posterior subcapsular cataract, a history of cataract surgery, and myopia were the associated factors of astigmatism in this study.