An IOP control device for implantation in an eye of a patient is disclosed. The device includes a housing and a multilayer membrane. The housing is sized for implantation into the eye and includes an entrance port and an exit port. The membrane is anchored within the housing to form a flow control chamber on a first side and a fluid flow passageway on a second opposing side of the membrane. The chamber is arranged to contain a gas creating a chamber pressure, and the membrane is configured to affect flow through the passageway from the entrance port to the exit port by deflecting in response to changes in the chamber pressure. The membrane comprises a first layer having a higher permeability and a higher flexibility than the second layer, which is disposed adjacent the first layer and restricts the diffusion of gas in the chamber through the membrane.
