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

• Anterior Segment Optical Coherence Tomography (AS-OCT) (Diagnostic test): Additional anterior segment OCT imaging of the iris to quantify the size and patency of the iridotomy or iridectomy in DMEK patients, performed as a non-invasive, contact-free study-related diagnostic procedure alongside routine clinical examinations.
• Dysphotopsia Questionnaire (Other): Structured patient questionnaire to assess occurrence and severity of new postoperative dysphotopsia after DMEK.

Primary outcomes

• Occurrence of postoperative pupillary block after DMEK [Within the first five postoperative days, including day 0 (date of surgery)]: Pupillary block is defined as intraocular pressure >25 mmHg with a centrally deep anterior chamber and partial or complete peripheral angle closure.

Secondary outcomes

• Occurrence and severity of postoperative dysphotopsia [between 2 weeks and 1 year postoperatively]: Assessed using a structured dysphotopsia questionnaire based on the instrument by Vera et al., providing an ordinal severity score.

Sex: All

Inclusion Criteria:

* Adults aged ≥ 18 years
* Patients undergoing Descemet membrane endothelial keratoplasty (DMEK) at the Department of Ophthalmology, University Hospital Leipzig
* Preoperative Nd:YAG laser iridotomy or intraoperative surgical iridectomy performed as part of standard care
* Ability to provide written informed consent
* Willingness to complete the postoperative dysphotopsia questionnaire

Exclusion Criteria:

* Inability to provide informed consent or refusal to participate
* Pre-existing surgical iridectomy
* Missing or incomplete preoperative or postoperative anterior segment OCT data
* Active anterior uveitis or panuveitis at the time of surgery