Visual Loss

Abstract

Tube shunt surgery use has increased significantly in recent years. Once reserved as a treatment option for more refractory types of disease, such as uveitic or neovascular glaucoma, or for eyes that had failed one or more trabeculectomies, tube shunts are now being used by some surgeons in place of trabeculectomy as a first-line surgical alternative in eyes with other less aggressive or less difficult to control forms of glaucoma. Visual loss can occur following tube shunt implantation as a result of complications during the postoperative period or from the progression of underlying disease (see Table 40.1). Although tube shunt implantation is associated with similar postoperative complications as trabeculectomy surgery, such as hypotony, hemorrhage, and failure to control IOP, there are several unique complications that may develop with the use of tube shunts, many of which may result in vision loss. Visual loss following tube shunt surgery is not uncommon. A large, systematic literature review of tube shunts by Hong and coworkers reported rates of vision loss following tube shunt surgery (defined as loss of 2 or more lines of visual acuity at last follow-up) ranging from (mean [SD]) 24 (7)% with the Ahmed™ Glaucoma Valve (New World Medical, Inc., Rancho Cucamonga, California) to 33 (18)% with the Molteno® implant (Molteno Ophthalmic Ltd., Dunedin, New Zealand). In the Tube Versus Trabeculectomy (TVT) Study, an ongoing, prospective, randomized clinical trial that is comparing the Baerveldt® 350 mm tube shunt (Abbott Medical Optics, Inc., Santa Ana, California) to trabeculectomy with mitomycin-C (MMC) in eyes with previous trabeculectomy and/or cataract surgery, vision loss (defined as loss of 2 or more lines of Snellen visual acuity) occurred in 31 of the 107 patients (29%) in the tube shunt group. The occurrence of any postoperative complication significantly increased the risk of vision loss (p < 0.001), and this risk correlated to the number of complications. Corneal decompensation has been reported to occur in up to 30% of patients during long-term follow-up after tube shunt surgery.