An Ahmed Valve, or glaucoma drainage valve, is a device that is used to help lower intraocular pressure when maximum medical therapy with eye drops and laser treatment is not enough. The valve is made of silicone, and consists of a micro-tube connected to a small end-plate or reservoir. The tube is surgically inserted into the front part of the eye allowing the aqueous fluid from inside the eye to slowly drain through the tube and into the reservoir which is placed on the outside of the eye under the conjunctiva. The fluid is then naturally absorbed by the surrounding tissue. The slow drainage of fluid is not harmful to the eye and decreases the internal pressure. The valve is not visible to the naked eye after surgery.