Tamsulosin and the Intraoperative Floppy Iris Syndrome

The intraoperative floppy iris syndrome (IFIS) was first described by Chang and Campbell in 2005.¹ These authors¹ and others² observed that there was a tendency for poor pupillary dilation and the intraoperative triad of the billowing of a flaccid iris, the propensity for iris prolapse, and progressive intraoperative pupillary constriction. In the current technique ophthalmologists perform cataract surgery through a 2.5-mm incision. A widely dilated pupil is essential for complication-free surgery. Billowing of the iris into the surgical field and poor pupillary constriction are potentially catastrophic barriers to successful surgery. Intraoperative floppy iris syndrome is encountered mainly in cataract surgery and in prospective studies has been found to occur in 2% to 3% of all cataract operations and to a lesser extent in glaucoma surgery.³

The strong association of IFIS with systemic (oral) administration of the α_1a- selective adrenergic antagonist tamsulosin, the commonly prescribed medication for treatment of benign prostatic hyperplasia, has been noted.^{1 - 2} In a prospective study³ involving 167 cataract operations, nearly 90% of the eyes of patients taking tamsulosin were diagnosed with IFIS. Indeed, all drugs of this class of α₁-antagonists are associated with the development of IFIS, although drugs with an affinity for α_1a-receptors (tamsulosin and silodosin) are more commonly associated with IFIS.^{4 - 5} α₁-Receptors are present in the dilator muscle and in the smooth muscle of the arteriolar wall in the iris. Intraoperative floppy iris syndrome has also been associated with the administration of finasteride and duasteride and saw palmetto.² Women are not immune to the syndrome because tamsulosin is used in the treatment of obstruction due to renal calculi. The IFIS is not associated with iris color, diabetes mellitus, or pseudoexfoliation.¹ Successful full dilation of the pupil is proportional to the amount of pigment present (eg, blue irides will dilate more rapidly and more fully than heavily pigmented brown irides).

However, IFIS is associated with increased intraoperative risk and complications, such as iris prolapse, pupillary miosis, iris trauma, iris aspiration, iridodialysis, hyphema, posterior lens capsular rupture, and vitreous loss.⁶ Posterior capsular rupture may lead to dislocation of lens fragments into the vitreous body and vitreous loss, setting the stage for secondary complications such as retinal detachment and severe postoperative inflammation (phacoanaphylactic endophthalmitis). These untoward events are associated with the necessity of performing additional surgical procedures in the early postoperative period. Until now, however, those in the ophthalmologic community have not had good evidence about how great the risk of tamsulosin-associated IFIS might be and whether the risk is modifiable through cessation of the drugs.

In this issue of JAMA, Bell and colleagues⁷ report the results of a nested case-control analysis of a population-based retrospective cohort study using linked health care databases from Ontario, Canada. Among men aged 66 years or older who had cataract surgery between 2002 and 2007, 3550 patients (3.7%) had recent exposure to tamsulosin and 7426 (7.7%) had recent exposure to other α-blockers. Serious ophthalmologic adverse events occurred in 284 patients (0.3%) and were significantly more common among patients with recent tamsulosin exposure (adjusted odds ratio, 2.33; 95% confidence interval, 1.22-4.43).

These findings regarding the serious consequences of tamsulosin-related IFIS in the 14-day period following cataract surgery are most certainly the consequence of posterior capsular rupture, loss of lens fragments into the vitreous body, and vitreous loss. Retinal detachment is a potential consequence of these events and one of the more serious complications of IFIS. The presence of retained lens material in the vitreous body is a strong irritant and may lead to phacoanaphylactic endophthalmitis. It is not surprising that cytological study of vitreous material removed at the time of surgery for retinal detachment or retained lens material or both is invariably associated with the preoperative administration of tamsulosin and an attendant IFIS at the time of cataract surgery.

The presence of α₁-adrenoreceptor subtypes in the iris dilator muscle has been previously demonstrated.⁸ Through careful studies of these receptors, our group has proposed that the blockade of receptors in the blood vessel walls of patients taking tamsulosin is associated with vascular dysfunction in the vessels that supply the iris (unpublished data, A.H.F., December 2008 available from author). But these vessels have curious properties. For example, angiography of the iris following iridectomy reveals no flow to the remaining portion of central iris at the pupil, yet the tissue does not atrophy.

The iris arterioles⁹ are end arterioles that do not anastomose or bifurcate in the iris stroma, and the iris does not depend on its vascular supply for its nutrition. Bill¹⁰ showed that the iris obtains nutrients from the surrounding aqueous humor, which bathes the iris. The iris vasculature may provide a “skeletal” framework that supports the iris tissue rather than the traditional role of blood supply alone. This is supported by the finding that blockade of the smooth muscle adrenergic receptors in the iris vessel wall and the dilator muscle is associated with severe dysfunction and consequently a floppy iris during surgery. More importantly, impairment of the smooth muscle of the iris arteriole wall damages the skeletal framework of the iris and leads to severe dysfunction. Blockade of adrenergic receptors in the iris dilator muscle following cessation of tamsulosin does not eliminate IFIS but may merely decrease the preoperative miosis.²

Thus, discontinuation of tamsulosin appears to be unpredictable and may not reliably reduce the severity of IFIS. Chang and Campbell¹ noted the occurrence of IFIS in patients who had stopped tamsulosin for more than a year. The observations of Bell et al⁷ of the 14-day window in which complications occurred are directly related to the intraoperative difficulties produced by the IFIS.

To mitigate the potential intraoperative problems, several pharmacological and mechanical strategies have been proposed^{11 - 13} : preoperative dilation with strong cycloplegic agents such as atropine or homatropine intraoperative use and highly viscous agents, low flow of fluids into and out of the eye, iris retractors, and mechanical pupillary expansion rings.

Cataract surgery is the most commonly performed operation in the United States today.¹⁴ With nearly 2 million cataract operations performed in the United States each year,¹⁴ the magnitude of IFIS associated with tamsulosin cannot be underestimated. Although the prescribing information for tamsulosin includes IFIS as a “general precaution,” the data on the risk of this complication should be reassessed to determine whether a “black box” warning should be issued to caution the ophthalmic surgeon and the general public (men in particular) of danger to the eye of taking α₁-adrenergic blocking agents before cataract surgery.