Serial changes in the bleb wall after glaucoma drainage implant surgery: Characteristics during the hypertensive phase

Abstract

Purpose To investigate serial changes in the bleb wall using anterior segment optical coherence tomography (AS-OCT) in patients who had undergone Ahmed glaucoma valve (AGV) implantation. Methods A total of 52 patients who had undergone AGV implantation were enrolled. Reflectivity and mean thickness of the bleb wall were examined using AS-OCT at 1 day, 1 week, 1 month, 3 months and 6 months postoperatively. Intra-ocular pressure (IOP) and the number of glaucoma medications were evaluated. The hypertensive phase was defined as IOP >21 mmHg during the first 3 months after surgery. Patients were divided into two groups: hypertensive and non-hypertensive groups. Results Following AGV implantation, IOP decreased at each time-point during postoperative follow-up (p value < 0.001, all) with a peak in the first month. Mean bleb wall thickness showed a U-shaped curve postoperatively, being thinnest 1 month after the operation. Reflectivity showed an inverted U-shaped curve postoperatively, being brightest 1 month after the operation. A hypertensive phase was observed in 44 patients (84.6%). The bleb wall was significantly more reflective (130.67 ± 27.00 versus 106.57 ± 10.35; p = 0.044) in the hypertensive group than in non-hypertensive group 1 month postoperatively. Conclusions Hypertensive phase peaked at 1 month after aqueous shunt surgery. At that time, the bleb wall had the highest reflectivity. The unique IOP pattern after tube surgery is related to fibrosis of the bleb wall qualitatively. Specific modulation of wound healing may be the target for attempts to decrease the development of hypertensive phase.