Abstract
Purpose :
The bleb that forms after glaucoma drainage implant (GDI) surgery can be difficult to assess due its more posterior position from the limbus. This cross-sectional observational study uses B-scan ultrasound to evaluate bleb morphology and to examine the relationship between bleb characteristics and clinical outcomes after Baerveldt glaucoma implant (BGI) surgery.
Methods :
44 patients (48 eyes) who underwent Baerveldt GDI surgery were included. Glaucoma patients with ≥6 months follow-up data and no prior glaucoma surgery were recruited from June - August 2022 for imaging. B-scan images of the bleb were obtained at least 6 months after surgery using transverse and longitudinal views. Presence of aqueous flow around the implant was characterized and bleb height above and below the endplate was measured. Intraocular pressure (IOP) and number of glaucoma medications was retrospectively obtained from patient charts before and after surgery (postoperative day 1, week 1, months 3, 6, and >6). Statistical correlations between bleb height and IOP were analyzed with Spearman’s rank correlation coefficient.
Results :
Mean preoperative IOP was 26.73 ± 10.51 mmHg which decreased to 12.76 ± 5.06 mmHg at the most recent follow-up (p<0.001). Mean number of glaucoma medications decreased from 2.44 ± 1.12 to 1.40 ± 1.10 at the most recent follow-up (p<0.001). Implants were in the superotemporal quadrant in 83.3% (40/48) of eyes and inferonasal quadrant in 16.7% (8/48) of eyes. Mean follow-up time from surgery to B-scan was 25.5 ± 18.4 months. There was a significant positive association between bleb height above the endplate and IOP for both the transverse (rs = 0.36, p<0.05) and longitudinal (rs = 0.54, p<0.01) views at 6 months. There was a significant negative association between bleb height below the endplate and IOP for both the transverse (rs = -0.44, p<0.01) and longitudinal (rs = -0.40, p<0.01) views at the most recent (>6 months) visit.
Conclusions :
BGI surgery led to significant reductions in IOP and medication burden. Higher blebs overlying the endplate may be correlated with elevated IOP at 6 months after surgery. Increased bleb height under the endplate and more fluid draining beneath the implant may result in better long-term IOP control. Further prospective studies may provide insight into how bleb morphology and aqueous flow affect IOP.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.