Intraluminal Stent Optimization for the Baerveldt Glaucoma Implant: An Experimental Study.

DiSclafani, Mark; Richards, David; Schneider, Alex; Whitfield, Whitney; Ayoubi, Yasmin

PRECIS Our laboratory study determined the approximate suture diameter for use in intraluminal stenting of the Baerveldt glaucoma implant to prevent postoperative hypotony. Commercial 3-0 monofilament nylon sutures which are commonly used may vary significantly outside of this diameter. PURPOSE Postoperative hypotony is a complication of surgical treatment of glaucoma using the Baerveldt glaucoma implant (BGI). One method utilized to prevent early postoperative hypotony is intraluminal stenting of the implant with monofilament sutures. The present study attempted to determine optimal stent diameter in microns for 3-0 monofilament sutures to reduce outflow and thereby reduce the risk of postoperative hypotony using the BGI. MATERIALS AND METHODS A laboratory bench model of the anterior chamber was utilized to measure the outflow rate of balanced salt solution (BSS) through the BGI at pressures of 20 and 40▒mmHg while utilizing commercially available 3-0 monofilament nylon stents of various diameters. The BGI tube has an inner diameter of 300▒µm. Additionally, 3-0 nylon sutures were studied for variability by measuring the diameters at 10 equally spaced points along the length of each sample using a digital micrometer. RESULTS Average experimental flow rates decreased with increasing intraluminal stent diameter and increased with increasing pressure. An intraluminal stent diameter of 250▒µm yielded a flow rate of 40▒µL/min at a nominal pressure of 20▒mmHg. Diameters of the tested 3-0 monofilament nylon sutures were all within the United States Pharmacopeia (USP) diameter range of 200-250▒µm, but diameters varied significantly depending on the manufacturer. CONCLUSIONS In our laboratory model, the optimal stent diameter to reduce aqueous flow to a level approaching the normal aqueous production is at least 250▒µm. Secondarily, commercially available 3-0 monofilament nylon suture materials showed variable diameters within the USP diameter range.