Longitudinal analysis of XEN45 gel stent bleb morphology using bleb grading scales, anterior segment-OCT, in vivo confocal microscopy, and impression cytology.

PURPOSE

To characterize bleb morphology and conjunctival features after XEN45 Gel Stent surgery (XGS) using slit-lamp bleb grading, anterior segment optical coherence tomography (AS-OCT), in vivo confocal microscopy (IVCM), and impression cytology analysis (ICA), in both success and failure cases.

METHODS

Twenty-four eyes (24 patients) underwent XGS, with 20 included in the final analysis. In addition to a full ophthalmic exam, blebs were evaluated using Moorfield's Bleb Grading System (BGS), AS-OCT, IVCM, and ICA. AS-OCT metrics included bleb-wall and subepithelial cyst-like structure area and density (BECSA/BECSD, BSCSA/BSCSD), bleb height (BH), bleb thickness (BT), and epithelial thickness (BET). IVCM parameters included stromal meshwork reflectivity (SMR), goblet cell density (GCD), epithelial microcyst density and area (EMD, EMA), and dendritic cell density (DCD). ICA assessed MUC5AC and HLA-DR/cell area ratio. Success was defined as an IOP < 21 mmHg and ≥ 20% reduction at six months. Imaging parameters were correlated with surgical outcomes.

RESULTS

At six months, 11 (55%) cases were classified as successful and 9 (45%) as failures. BGS showed significantly larger blebs in the success group (88.9% with maximal diffusion area grade ≥ 3 vs. 22.1%, p < 0.05). AS-OCT detected persistent epithelial and subepithelial changes in successful blebs, with significantly higher BECSA (0.11 vs. 0.02 mm², p < 0.02). Preoperatively, successful cases showed higher GCD on IVCM (67.3 vs. 39.2 cells/mm², p = 0.25) and mucin expression on ICA (MUC5AC/cell ratio: 1.28 vs. 0.01, p = 0.11). Postoperative IVCM also showed trends toward increased EMD in both groups, though not statistically significant.

CONCLUSION

Successful XGS blebs were associated with higher preoperative goblet cell density (IVCM) and mucin expression (ICA). Postoperatively, AS-OCT parameters-especially epithelial and subepithelial changes-showed the strongest correlation with IOP, highlighting AS-OCT as the most clinically applicable tool for monitoring bleb function.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT04727411, January 22, 2021.