The Effect of Alpha Antagonists on Pupil Dynamics: Implications for the Diagnosis of Intraoperative Floppy Iris Syndrome

Abstract

To assess pupil dynamics quantitatively in relation to the use of α1-adrenoceptor antagonists, which contribute to the features of intraoperative floppy iris syndrome, using a new, hand-held, digital pupillometer. Prospective case-control study. We studied 15 and 25 patients administered tamsulosin and alfuzosin, respectively, as well as 25 control patients. Resting pupil diameter and subsequent contraction, latency, constriction velocity, and dilation velocity were recorded using an electronic pupillometer. All pupil measurements were performed before and after pharmacologic dilation. In predilation pupillary measurements, we detected a significant decrease in maximum pupillary diameter by 0.50±0.19 mm (P=.011) and in the mean percentage of diameter reduction after stimulation (5.23±2.42%, P=.035) in the tamsulosin group. Alfuzosin also induced a significant decrease in maximum pupillary diameter (0.49±0.17 mm, P=.005). Constriction velocity was significantly reduced by 0.70±0.20 m/s (P=.001) in the tamsulosin group and by 0.54±0.18 m/s (P=.004) in the alfuzosin group. In terms of postdilation measurements, maximum and minimum pupil diameters were reduced significantly only in the tamsulosin group (by 1.09±0.31 mm [P=.001] and by 0.89±0.36 mm [P=.016], respectively). We describe a reliable, accurate, and rapid method to acquire quantitative pupil measurements and identify the tendency for intraoperative floppy iris syndrome before cataract surgery after the use of alfuzosin and tamsulosin. This investigation also analyzed the similarities and differences induced by the 2 drugs in predilation and postdilation pupil dynamics, demonstrating that tamsulosin is more potent than alfuzosin in inducing intraoperative floppy iris syndrome.