Donor sclera versus bovine pericardium as patch graft material in glaucoma implant surgery and the impact of a drainage suture.

PURPOSE: To compare the use of human donor sclera with bovine pericardium as patch graft material for a glaucoma drainage device (GDD), with respect to the incidence of tube exposure, and to study the role of a drainage suture. METHODS: All GDD surgeries between 2010 and 2014 performed at the VU Medical Center were examined in this comparative, retrospective cohort study. A total of 244 cases were included; 163 in the human donor sclera cohort and 81 in the bovine pericardium cohort with a median follow-up of 31 and 36 months, respectively. The primary outcome measure was occurrence of tube exposure. Survival analysis for tube exposure was carried out and Kaplan-Meier curves compared. Secondary outcomes were postoperative intraocular pressure (IOP), number of glaucoma medications and the effect of a drainage suture. RESULTS: In the bovine pericardium cohort, eleven (13.6%) eyes developed tube exposure compared to none in the human donor sclera cohort. Their Kaplan-Meier survival curves differed significantly from each other (χ² = 21.1, p < 0.001, log-rank test). Mean IOP and number of glaucoma medications did not differ significantly between patch graft materials at three months of follow-up. The use of a drainage suture directly lowered IOP after surgery in both cohorts. Within the bovine pericardium cohort, eyes with a drainage suture experienced more tube exposure, although this difference was not statistically significant (p = 0.09). CONCLUSION: Human donor sclera leads to less tube exposure than bovine pericardium. A drainage suture directly lowers IOP after surgery. With bovine pericardium, but not with donor sclera, exposure tends to be enhanced by a drainage suture.

Postoperative pressure regulation in glaucoma shunt surgery: focal tube constriction is not the answer.

PURPOSE: To evaluate, in a laboratory setting, the accuracy and the clinical use of focal tube constriction as a means to regulate intraocular pressure after glaucoma drainage implant surgery. MATERIALS AND METHODS: A silicone tube identical to the one used in the Baerveldt and other glaucoma drainage implants was connected to a syringe-pump delivering a continuous flow of demineralized water at a rate of 2.5 microliters per minute. Focal constriction of the tube was obtained by a ring made of a shape-memory metal alloy designed for this purpose. After complete occlusion of the tube lumen by crimping the ring with calibrated pliers, the ring was opened in a stepwise manner by heating it with an argon laser beam. In a second experiment the tube lumen was constricted by placing the tube between the jaws of a micrometer. RESULTS: In both experiments a stepwise lowering of the pressure could be obtained. The resulting pressure levels, however, lacked consistency and predictability to such an extent that clinical application is not feasible. CONCLUSION: It is not possible to regulate pressure in a reliable and predictable way merely by constricting the tube lumen of glaucoma drainage implants.