A Case of Intraocular Pressure Elevation Secondary to Pupillary Occlusion.

We report a case of acute intraocular pressure (IOP) elevation caused by pupillary occlusion in a Japanese man in his 90s. The patient presented with a left frontal headache and vomiting, and ophthalmologic evaluation revealed marked IOP elevation, a shallow anterior chamber, and pupillary membrane formation obscuring the lens. While anterior segment optical coherence tomography (AS-OCT) was unable to confirm the lens position, ultrasound biomicroscopy (UBM) clearly demonstrated the absence of lens displacement or intraocular mass. Yttrium aluminum garnet (YAG) laser membranotomy promptly deepened the anterior chamber and lowered IOP, followed by successful cataract surgery. Differentiation from pupillary seclusion, another cause of secondary angle closure, is critical, as it requires distinct therapeutic approaches. This case highlights the diagnostic and therapeutic considerations in managing rare causes of acute glaucoma and serves as an instructive example for ophthalmology trainees.