Longitudinal changes in bleb morphology following the PAUL Glaucoma Implant visualized using ultrasonography

To evaluate bleb morphology longitudinally using sonography following glaucoma drainage device (GDD) surgery.

Prospective observational cohort study conducted from January 2022 to March 2024, with follow-up up to 12 months postoperatively. Bleb morphology, including superior and inferior bleb height, transverse and longitudinal dimensions, and total bleb height, was assessed using 15-MHz ultrasound (Quantel Medical, Compact Touch).

Forty-eight eyes undergoing PGI implantation were prospectively enrolled. Preoperative mean IOP was 23.6 mmHg (range, 13-42) on 3.2 medications. Mean total bleb height increased from 2.33 mm (range, 0.64-6.6) at day 14 to 4.14 mm (1.21-7.66) at month 3 and remained stable through month 12 (4.21 mm; 2.13-9.4). Double-layered blebs predominated by month 1 and persisted thereafter. Mean IOP decreased to 12.7 mmHg at day 14 and remained between 13 and 15 mmHg through 12 months, while medication use declined to 0.9 drops. Mixed-model analysis showed that absolute bleb height was significantly associated with higher IOP (β = 0.86, p = 0.043), independent of time. Accelerated bleb enlargement within the first 3 months correlated with higher IOP (β = 3.57, p = 0.003), whereas later changes showed no consistent associations.

Ultrasound imaging revealed progressive bleb enlargement after PGI implantation, stabilizing by 3-6 months. In the subgroup of patients who completed the 12-month follow-up, IOP reduction remained stable throughout the first postoperative year. Absolute bleb height showed a consistent association with IOP across time, whereas early growth rate was only predictive during the early postoperative period. These findings provide the first longitudinal sonographic evidence of bleb remodelling after GDD surgery and may guide postoperative assessment and intervention timing.