Background Intraoperative floppy iris syndrome is a variant of the small pupil syndrome that has been observed during cataract surgery in some patients currently or previously treated with alpha 1 adrenergic blockers. It is important for cataract surgeons to predict the probable complications preoperatively. Our study aims to evaluate the static and dynamic pupil characteristics of patients treated with silodosin-a selective alpha 1 adrenergic blocker-for benign prostate hypertrophy (BPH) and to compare these values with healthy subjects using an automatic quantitative pupillometry system. Methods A total of 74 BPH patients treated with silodosin for six months (group 1) and 30 healthy subjects (group 2) were enrolled in this prospective multidisciplinary cross-sectional study. Static and dynamic pupillometric measurements were obtained under optimized conditions, and the results were compared between the two groups. Results Seventy-four male patients with a mean age of 63,35 +/- 7,21 (46-77) years with BPH treated with silodosin and 30 normal male subjects with a mean age of 63,07 +/- 4,73 (52-71) years were analyzed. There were statistically significant differences between the groups with regard to scotopic pupil diameter (PD), high photopic PD, and low photopic PD (p < 0.001, for each one). The patient group had statistically significant higher values of amplitude and velocity of pupil contraction and lower values of duration of pupil contraction and latency as well as duration and velocity of pupil dilation. Conclusion The static and dynamic pupil characteristics of subjects treated with silodosin for BPH are different from those of healthy eyes. In addition, our results may have shed light on the risk for intraoperative floppy iris syndrome (IFIS) before cataract surgery; thus, surgeons can be alert and take precautions.