Pathophysiology of intraoperative floppy iris syndrome: An unsettled debate.

Intraoperative floppy iris syndrome (IFIS)--characterized by iris blowing, prolapse, and progressive miosis during phacoemulsification surgery--poses significant challenges for eye surgeons. Despite being described almost 2 decades ago, its pathophysiology remains unclear. Initially, IFIS was thought to be a result of sympathetic signal blockage in the iris dilator muscle, since α-blockers such as tamsulosin were found to be a strong predisposing factor; however, many IFIS cases occur even in patients who discontinued α-blockers prior to cataract surgery. Several potential mechanisms through which α-blockers induces chronic changes in the iris - iris dilator atrophy, drug-melanin interaction, and loss of vascular tone - have been proposed as possible mechanisms. We address the prevailing theories on α-receptor-dependent mechanisms for IFIS and the current prophylactic measures undertaken to prevent IFIS-associated intraocular complications.