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K Lim, T Bufidis, E Eslah, IE Murdoch, PT Khaw, K Barton; Early Flow Control in a Non-valved Glaucoma Drainage Device: Intraluminal Stent Suture in Isolation . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3357.
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Purpose:When implanting non-valved glaucoma drainage devices (GDD), an external occlusive vicryl ligature is often used to prevent drainage. Profound hypotony may still occur when the ligature opens, especially with larger implants such as the Baerveldt 350 and Mitomycin C (MMC) exposure. The aim is firstly to described the clinical intraocular pressure (IOP) profile of a 3/0 supramid suture used as a stent without an occlusive ligature when implanting the Baerveldt 350 GDD after MMC exposure and secondly to determine, experimentally, the flow resistance provided by this technique and if IOP can be titrated by variation in the intraluminal suture length. Methods:1) 20 patients with recalcitrant glaucoma were implanted with Baerveldt 350 GDDs after exposure to MMC. The lumen was occluded using a supramid suture with an intraluminal length of 10 mm. Postoperative examinations were carried out at regular intervals. 2) 6 Baerveldt tubes stented with supramid sutures were examined using a flow rig consisting of a microsyringe pump and pressure transducer. Tubes were infused with either balanced salt solution (BSS) or BSS containing normal aqueous concentrations of albumin at a flow rate of 2 ml/min. Back pressures were computer monitored under these circumstances using 5 different lengths of intraluminal occlusion. Results:1) The preoperative IOP was 32±2 (mean±SEM) mmHg. Postoperative IOPs were 14.5±2.1, 12.3±2.1, 14.7±2.3, 15.5±1.8, 17.6±2.4, 15.8±2.1, 15.3±1.5 at 1, 7, 14, 28 days, 2, 3 and 4 months respectively. There were no cases of hypotony (IOP < 6 mmHg) on postoperative day 1. Although there were 3 cases on day 7, no IOP was < 3 mmHg and there were no sequelae of hypotony. 2) Intraluminal stenting provided no significant back pressure when perfused with BSS alone, but back pressure became substantial and linearly related to intraluminal length when perfused with BSS containing 22.4 mg/100ml albumin. Pressures were measured at 6.5±0.9, 4.4±1.0, 3.4±0.6, 2.6±0.7, 1.3±0.9 mmHg (mean SD) using occlusion lengths of 10, 8, 6, 4 and 2 mm respectively. Conclusion:A supramid stent suture can be used safely without an adjunctive occlusive ligature when implanting a Baerveldt 350 GDD with MMC exposure. An intraluminal length of 10 mm prevents early hypotonous sequelae. Significant back pressures were seen when this technique was examined experimentally. The difference in resistance produced by albumin demonstrates the importance of emulating physiological conditions in GDD flow studies.
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