Pupillary Dilator Muscle Thickness as a Potential Predictor of Intraoperative Floppy Iris Syndrome

Intraoperative Floppy Iris Syndrome (IFIS) is an unpredictable complication that may occur during cataract surgery in patients diagnosed with lower urinary tract symptoms (LUTS) undergoing therapy with α1-adrenergic receptor antagonists (α1-ARAs). Of all α1-ARAs, tamsulosin is most strongly associated with the development of IFIS. IFIS is characterized by a fluttering, unstable iris, its prolapse into corneal incisions, and intraoperative progressive miosis despite pharmacologically induced mydriasis in the preoperative period. The use of α1-ARAs reduces the tone of the pupil dilator muscle and subsequently leads to its gradual atrophy, which causes laxity of the iris stroma and the development of IFIS during cataract surgery. Based on the presence of individual signs, the investigators distinguish between mild, moderate, and severe forms of IFIS. IFIS symptoms can complicate cataract surgery and increase the risk of complications during and after surgery. During cataract surgery, posterior capsule rupture with lens masses luxation into the vitreous body, damage the iris by the phacoemulsification probe, or prolapse of the vitreous body into the anterior chamber may occur. In the postoperative period, the patient may experience elevated intraocular pressure, persistent photophobia, endophthalmitis, or cystoid macular edema. Ultimately, IFIS can negatively affect the functional outcome of the surgery and leave the patient dissatisfied with permanently reduced vision quality. Anatomical changes in the iris caused by the use of α1-ARAs can be verified using anterior segment optical coherence tomography (AS-OCT). In this study, the authors used AS-OCT as the main instrument for measuring individual iris parameters prior to cataract surgery in patients undergoing α1-ARAs therapy. The goal was to determine whether there is a correlation between the degree of atrophy of the pupillary dilator muscle and the incidence of IFIS development. Among other things, the investigators also focused on measuring pupil diameter. During the study, the incidence of intraoperative complications and the relationship between the duration of α1-ARA use and the development of IFIS were evaluated. In patients, the parameters of the iris in the first eye scheduled for cataract extraction using AS-OCT Carl Zeiss Visante was measured before cataract surgery. The investigators performed AS-OCT measurements under photopic conditions with maximum artificial lighting (>300 lux) and under scotopic conditions in a dark room with the patient covered with a black non-translucent cloth (0 lux). The thickness of the pupillary dilator muscle at half the distance between the scleral spur and the edge of the pupil, the pupillary sphincter muscle at a distance of 0.75 millimeters from the edge of the pupil and the ratio to compensate for possible variability between subjects were evaluated. The investigators also used AS-OCT to measure the pupil diameter without mydriasis under photopic and scotopic conditions. Under scotopic conditions, the pupil size was assessed 30 minutes after inducing artificial mydriasis using a combination of 1% tropicamide and 10% phenylephrine hydrochloride mydriatics, which were applied three times at 10-minute intervals. The horizontal images were taken in the center of the pupil under both light conditions, performing the measurements three times and averaging the resulting values. In addition to iris and pupil parameters, patients´ age, type, and duration of α1-ARA use were determined. The investigators also monitored the development of IFIS during cataract surgery, determining its severity based on the classification established by Chang and Campbell, and the occurrence of intraoperative complications. The cataract surgeons were informed in advance about the risk group of patients. At the beginning of the cataract surgery, phenylephrine at a dose of 0.2 mg/ml was administered to the anterior chamber to induce more pronounced mydriasis and restore iris rigidity. The surgery was performed by experienced surgeons using a temporal approach with the Alcon Centurion Vision System and Alcon Constellation Vision System.