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Abstract
Purpose
To evaluate the flow resistance though the tube in a glaucoma drainage implant using various tube ligation methods.
Methods
To measure the flow resistance, the following tube ligation methods were designed and tested: Type 1: no ligation of Ahmed valve tube. Type 2: ligation of Ahmed valve tube with 8-0 Vicryl. Type 3: ligation of Molteno tube and a 6-0 Vicryl as an intra-luminal stent with 8-0 Vicryl. Type 4: ligation of Ahmed valve tube and three strands of 8-0 nylon as extra-luminal stents with 8-0 Vicryl. Type 5: ligation of Ahmed valve tube and a 6-0 Prolene as an extra-luminal stent with 8-0 Vicryl followed by removal of the Prolene for partial ligation.
Results
The pressure was maintained under 0.143 mm Hg in type 1. In type 2, the pressure increased to 6.688 mm Hg and dropped to approximately 6.384 mm Hg. In type 3, the pressure was maintained at 5.396 mm Hg which decreased to 3.572 mm Hg after stent removal. In type 4, the pressure was maintained at 5.700 mm Hg which dropped to 5.472 mm Hg after the 1st stent removal, to 5.016 mm Hg after the 2nd stent removal and to 4.180 mm Hg after the 3rd stent removal. In type 5, the pressure increased to 6.384 mm Hg and decreased to 5.624 mm Hg.
References
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Figure 1.
Closed manometric apparatus used in this experiment for the calibration of manometer. Pig eye is connected in series with anterior chamber (A/C) cannulator, infusion pump and manometer. (A) Pig eye is given pressured on by A/C cannulator. BSS solution is flowed into pig eye with infusion pump. (B) A/C cannulator intentionally makes intraocular pressure (IOP) of pig eye the level that we want. Intraocular pressure is internally measured by manometer and external measured by rebound tonopen. Intraocular pressures measured by manometer and rebound Tono-Pen and A/C cannulator-made pressure are compared each other. (C) Infusion pump used in this experiment. (D) Manometer used in this experiment. (E) Anterior chamber (A/C) cannulator used in this experiment. (F) Rebound Tono-Pen used in this experiment.
Figure 2.
(A) Closed manometric apparatus to measure intraluminal pressure in the tube of glaucoma drainage devices (GDD). (B) Schematic diagram of this apparatus used in this experiment. Tube is connected in series with infusion pump and manometer. (C) Ahmed valve implant is connected with a Healon needle. (D) It is observed that a Molteno tube is connected with a Healon needle. A 6-0 Vicryl stent is found in the left side of the tube.
Figure 3.
Various tube ligation and stent methods. (A) Type 1, no ligation of Ahmed valve tube. (B) Type 2, ligation of Ahmed valve tube with 8-0 Vicryl. (C) Type 3, ligation of Molteno tube and a 6-0 Vicryl as an intra-luminal stent with 8-0 Vicryl. (D) Type 4, ligation of Ahmed valve tube and three strands of 8-0 nylon as extra-luminal stents with 8-0 Vicryl. (E) Type 5, ligation of Ahmed valve tube and a 6-0 Prolene as an extra-luminal stent with 8-0 Vicryl and then Prolene is removed for partial ligation.
Figure 4.
The measurement of flow resistance in Ahmed and Molteno implant using various tube ligation methods.
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