Impact of Iridotomy/Iridectomy Size on Postoperative Pupillary Block and Dysphotopsia Following DMEK

Descemet Membrane Endothelial Keratoplasty (DMEK), Dysphotopsia, Laser Iridotomy / Surgical Iridectomy, Pupillary Block After DMEK

Descemet membrane endothelial keratoplasty (DMEK) is the standard surgical treatment for corneal endothelial disorders. A postoperative pupillary block may occur despite routine preoperative laser iridotomy or intraoperative surgical iridectomy. Insufficient size or incomplete patency of the iridotomy/iridectomy (IT) may contribute to this complication, while excessively large openings may be associated with postoperative dysphotopsia. This prospective observational study investigates the association between IT size measured by anterior segment optical coherence tomography (AS-OCT) and the occurrence of postoperative pupillary block and dysphotopsia after DMEK.

Descemet membrane endothelial keratoplasty (DMEK) represents the current standard procedure for surgical treatment of corneal endothelial diseases. During DMEK, a gas bubble is placed in the anterior chamber to attach the graft. In rare cases, this may lead to postoperative pupillary block with acute intraocular pressure elevation and severe pain. To prevent this complication, preoperative Nd:YAG laser iridotomy or intraoperative surgical iridectomy is routinely performed. Nevertheless, pupillary block continues to occur in a subset of patients. One potential cause is an iridotomy or iridectomy that is too small or not fully patent, which may be misclassified as open on slit-lamp examination. Conversely, large iridotomy openings may induce postoperative dysphotopsia. Currently, no standardized recommendations exist regarding optimal IT size in the setting of DMEK, and systematic data correlating IT size with pupillary block and dysphotopsia are lacking. This study is designed as a prospective, monocentric, non-interventional observational study. Adult patients undergoing DMEK at the Department of Ophthalmology, University Hospital Leipzig, with either preoperative laser iridotomy or intraoperative surgical iridectomy are invited to participate. AS-OCT imaging of the iris is performed preoperatively or postoperatively as an additional study-related diagnostic procedure to quantify IT size. All surgical procedures and clinical follow-up examinations remain unchanged from standard care. Postoperatively, clinical outcomes including the occurrence of pupillary block are documented during routine follow-up. New postoperative dysphotopsia is assessed using a structured, German-adapted dysphotopsia questionnaire based on the instrument described by Vera et al., administered after resolution of the intracameral gas bubble and corneal edema. The primary endpoint is the occurrence of postoperative pupillary block after DMEK. The secondary endpoint is the occurrence and severity of new postoperative dysphotopsia. A total of 100 consecutive patients will be included over a planned study period of 12 months. The study aims to explore associations between IT size and postoperative complications in order to improve perioperative risk stratification in DMEK surgery.

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