Valve Technology: Mechanics of the Ahmed Glaucoma Valve
Flow resistance, R, is the inverse of flow facility, F, and is the key element in controlling eye pressure. For steady, laminar flow, R can be thought of as the rise in pressure associated with a rise in flow rate, i.e. the slope of the pressure vs. flow curve:
The Ahmed Glaucoma Valve naturally varies its critical flow path dimension with pressure, which provides (1) reduced risk of hypotony at low pressures and (2) increased flow facility at moderate pressures.
Non-Obstructive, Self-Regulating Valve Mechanism:
The Ahmed® Glaucoma Valve has no obstruction in its path of fluid flow. For the flow to be non-obstructive, a particle large enough to pass through the lumen of the tube, will easily pass through the much larger opening of the Venturi-Flow chamber. The elastic membranes help to regulate fluid flow at all times, consistently by changing their shape. The tension on these membranes is responsible of reducing hypotony.