During the last two decades, glaucoma drainage devices (GDD) have been increasingly applied to the treatment of complicated glaucoma in which standard surgical therapy has failed. Most GDD's consist of a segment of silicone rubber attached to a rigid plastic or flexible rubber explant and evolved from the Molteno glaucoma implant, on which clinical studies first appeared in 1969. GDD's should be reserved for the most difficult cases because of the difficulty of the surgical procedure and the complications that can attend their use.