Glaucoma drainage devices: Indications, intraoperative management and postoperative follow-up

Glaucoma drainage devices (GDD) are used for patients with secondary glaucoma, such as uveitic or neovascular glaucoma, which is uncontrolled under local therapy. They are also used in patients with conjunctival scarring, for example after a previous vitrectomy or after unsuccessful previous glaucoma surgery, such as trabeculectomy. They are also a treatment option for congenital glaucoma, aphakic glaucoma or for the treatment of iridocorneoendothelial syndromes. The conventional GDD were the Baerveldt, Molteno or Ahmed glaucoma implant, whereby the first two were valveless and the latter had a valve. Newer GDD include the PAUL glaucoma implant, the Ahmed Clear Path and the EyeWatch system. Hypotony is a feared complication after GDD surgery, and there are various options for avoiding it: external ligation of the tube or intraluminal suture obstruction. However, low IOP may still occur postoperatively. If early postoperative hypotension occurs in combination with a shallow anterior chamber, the injection of a viscoelastic can be helpful. Late hypotension is usually treated with permanent occlusion or removal of the tube. Furthermore, GDD erosion and migration can occur postoperatively, in such cases a surgical revision is required. Corneal decompensation can also occur after GDD; Descemet's membrane endothelial keratoplasty (DMEK) is the treatment of choice in many centers and is performed more frequently than a penetrating keratoplasty. Finally, double vision is a possible complication after GDI. Most patients have short-term, self-limited diplopia or can be adequately treated with prism glasses; a few require strabologic surgery.