Published date: Apr 19 2023

Journal Title: Journal of Ophthalmic and Vision Research

Issue title: April–June 2023, Volume 18, Issue 2

Pages: 157–163

DOI: 10.18502/jovr.v18i2.13181

Michael YangGavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California

Christopher YangGavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California

Ken Linlinky@hs.uci.eduGavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, California

Purpose: This study investigates the effect of one versus two fenestrations on both fluid egress and opening pressure from a non-valved glaucoma implant.

Methods: In this laboratory study, we used an in vitro closed system comprised of ligated silicone tubing connected to a fluid reservoir and manometer to simulate the tubing found in a Baerveldt glaucoma drainage implant. Fenestrations were created using an 8-0 Vicryl TG140-8 suture needle. Main outcome measures included volume of fluid egress and fenestration opening pressures, which were measured via micropipette and increasing pressure until fluid egress was observed.

Results: No significant difference was observed in fluid egress between tubing with one versus two fenestrations at pressures ≤40 mmHg. At 50 mmHg, a statistically significant difference was observed in fluid egress between tubing with one versus two fenestrations (P < 0.05). The first fenestration opened at 10.5 ± 3.77 mmHg and the second fenestration opened at 28.83 ± 5.09 mmHg (average ± standard deviation).

Conclusion: Our in vitro findings suggest there may exist a critical pressure >40 mmHg at which the second fenestration starts to play a significant role in fluid drainage. There may be no difference in the amount of fluid egress and effect on intraocular pressure between one or two tube fenestrations when preoperative intraocular pressure is ≤40 mmHg.

Keywords: Baerveldt, Drainage Implants, Fenestration, Glaucoma, Opening Pressure

1. Vinod K, Gedde SJ, Feuer WJ, Panarelli JF, Chang TC, Chen PP, et al. Practice preferences for glaucoma surgery: A survey of the American Glaucoma Society. J Glaucoma 2017;26:687–693.

2. Budenz DL, Barton K, Gedde SJ, Feuer WJ, Schiffman J, Costa VP, et al. Five-year treatment outcomes in the Ahmed Baerveldt comparison study. Ophthalmology 2015;122:308–316.

3. Christakis PG, Kalenak JW, Tsai JC, Zurakowski D, Kammer JA, Harasymowycz PJ, et al. The Ahmed versus Baerveldt Study: Five-year treatment outcomes. Ophthalmology 2016;123:2093–2102.

4. Krupin T, Podos SM, Becker B, Newkirk JB. Valve implants in filtering surgery. Am J Ophthalmol 1976;81:232–235.

5. Coleman AL, Hill R, Wilson MR, Choplin N, Kotas-Neumann R, Tam M, et al. Initial clinical experience with the Ahmed Glaucoma Valve implant. Am J Ophthalmol 1995;120:23– 31.

6. Poelman HJ, Wolfs RCW, Ramdas WD. The baerveldt glaucoma drainage device: Efficacy, safety, and place in therapy. Clin Ophthalmol 2020;14:2789–2797.

7. Honda R, Kasuga T, Murakami A, Matsuda A. Effects of the numbers and the shapes of venting slits on intraocular pressure after baerveldt glaucoma drainage implant. Curr Eye Res 2019;44:921–924.

8. Olayanju J, Borras T, Qaqish B, Fleischman D. Outflow facility in tube shunt fenestration. J Curr Glaucoma Pract 2018;12:113–118.

9. Brooks SE, Dacey MP, Lee MB, Baerveldt G. Modification of the glaucoma drainage implant to prevent early postoperative hypertension and hypotony: A laboratory study. Ophthalmic Surg 1994;25:311–331.