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H. Park, K. Park, S. Kim, T.-W. Kim, J. Jeoung, D. Kim; The Measurement of Flow Resistance in Ahmed and Molteno Implant Using Various Tube Ligation Methods. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4447.
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The tube ligation methods with or without intra- or extra-luminal stent are performed during surgery to prevent early postoperative hypotony. We would like to evaluate the flow resistance though the tube in valved and non-valved glaucoma implant using various tube ligation methods.
The Ahmed or Molteno valve was connected with the line from infusion pump and the manometer was connected between the pump and valve. The balanced salt solution was infused with 2 µl/min and the flow resistance was indirectly measured by continuous monitoring the pressure over one hour by the manometer. The experiment was done with 5 different types of tube ligation. Type 1: no ligation of Ahmed valve tube. Type 2: ligation of Ahmed valve tube with 8-0 Vicryl. Type 3: ligation of Ahmed valve tube and three strands of 8-0 nylon as extra-luminal stents with 8-0 Vicryl. Type 4: ligation of Ahmed valve tube and a 6-0 Prolene as an extra-luminal stent with 8-0 Vicryl and then Prolene was removed for partial ligation. Type 5: ligation of Molteno tube and a 6-0 Vicryl as an intra-luminal stent with 8-0 Vicryl.
The pressure was maintained under 0.143 mmHg in type 1. In type 2, the intraocular pressure increased to 6.688 mmHg without flow and after starting the flow it dropped to around 6.384 mmHg with continuous flow. In type 3, the pressure was maintained at 5.700 mmHg which dropped to 5.472 mmHg after 1st stent removal, to 5.016 mmHg after 2nd stent removal and to 4.180 mmHg after 3rd stent removal. In type 4, the pressure increased to 6.384 mmHg without flow and after starting the flow it decreased to 5.624 mmHg. In type 5 the pressure was maintained at 5.396 mmHg which decreased to 3.572 mmHg after intra-luminal stent removal.
There was a flow even with complete ligation of the tube. The tube ligation along with extra-luminal stents followed by staged removal may provide prevention of hypotony and staged control of intraocular pressure after glaucoma implant operation.
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