Intraoperative floppy iris syndrome (IFIS) is a recently described condition observed during cataract surgery. It has been hypothesized that irreversible atrophy of the iris dilator muscle associated with α1-adrenergic receptor antagonists (α1-ARA) is responsible for IFIS. However the prevalence of IFIS in Korean population is not reported. The purpose of this study is to evaluate the prevalence and clinical manifestations of IFIS in relation to iris anatomical change in Korean patients taking α1-ARA.