Intraluminal Stent Optimization for the Baerveldt Glaucoma I
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This 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.

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.

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 40mmHg while utilizing commercially available 3-0 monofilament nylon stents of various diameters. The BGI tube has an inner diameter of 300microm. 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.

--Average experimental flow rates decreased with increasing intraluminal stent diameter and increased with increasing pressure.

--An intraluminal stent diameter of 250microm yielded a flow rate of 40microL/min at a nominal pressure of 20mmHg.

--Diameters of the tested 3-0 monofilament nylon sutures were all within the United States Pharmacopeia (USP) diameter range of 200-250microm, but diameters varied significantly depending on the manufacturer.

To summarize, the ideal stent diameter for reducing aqueous flow to a level closer to normal aqueous output is at least 250 micrometers. Second, within the USP diameter range, commercially available 3-0 monofilament nylon suture materials showed variable diameters.