Eyeworld

EW GLAUCOMA 84 by Tony Realini, M.D., M.P.H. Managing the post-op tube-shunt in glaucoma: Pearls for weathering the storm T ube-shunt implantation for glaucomatous eyes requir- ing surgical intervention for IOP reduction has be- come more popular in re- cent years. This is due at least in part to the Trabeculectomy vs. Tube Study, which demonstrated greater long-term success with tubes versus standard filtering surgery. At the an- nual meeting of the American Glau- coma Society in Dana Point, Calif., a panel of expert glaucoma surgeons shared their pearls on the post-op management of tubes. When IOP is too high "In the early post-operative period," said Jody Piltz-Seymour, M.D., Scheie Eye Institute, Philadelphia, "we should expect a transient hyper- tensive phase if we are using a non- valved implant, such as a Baerveldt [Abbott Medical Optics, Santa Ana. Calif.]. These devices have no inher- ent flow restriction and depend on the formation of a capsule around the plate to provide flow restriction, so we typically ligate the tube, stent it, or both, in order to provide short- term outflow resistance while wait- ing for the capsule to form." There are steps that can be taken to minimize this iatrogenic hypertensive phase. "We can use a valved implant," said Dr. Piltz- Seymour. "Or we can place some venting slits in the extraocular por- tion of the tube proximal to the liga- ture to give aqueous an alternate flow route. Some surgeons even place a short vicryl wick across the lumen of the tube to further facili- tate aqueous flow in the short term. The wick dissolves in the same time frame that the capsule forms." Other options include an or- phan trabeculectomy that is ex- pected to fail coincident with the development of the capsule and consideration of a steroid effect in the early post-op period, she said. Some patients don't emerge from the hypertensive phase despite these efforts. "A significant number of patients who experience an early hypertensive phase will ultimately require intervention to restore tube function," said Nathan Radcliffe, M.D., Weill Cornell Medical College, New York. "The first step here is to visual- ize the tube tip—whether it was placed in the anterior chamber, the ciliary sulcus, or the vitreous cav- ity—to be sure it is not occluded," he said. If it is occluded, various sur- gical techniques can be employed to re-establish patency, he said. In some cases, outflow obstruc- tion occurs posteriorly at the plate. "The capsule can be so fibrous that no flow across its wall is possible. Also, fibrous tissue can grow into the plate and block flow," said Dr. Radcliffe. Options for this set of is- sues include bleb needling, which can be effective in some patients, and excision of the capsule, which can also be helpful. When IOP is too low The causes of low IOP following tube implantations are numerous and varied, according to Jeffrey Kalenak, M.D., Milwaukee, Wis. "Assuming the tube is ligated and we aren't dealing with overfil- tration, one of the most common is a leak," he said. "If there's a leak, we need to fix it." "Other considerations include uveitis with ciliary shutdown, a reti- nal detachment, a cyclodialysis cleft, or a cyclitic membrane," he said. "Also, be aware that some patients do not discontinue the use of their IOP-lowering medications after sur- gery, which can be a simple solution once you identify it as the cause of the hypotony." If everything else is ruled out and overfiltration is the suspected culprit, there are several steps that can be taken to deal with low IOP, he said. "The first step is to reform the anterior chamber with viscoelastic," he said. "I prefer a 30 g needle through a new track rather than try- ing to find and use the surgical para- centesis. It's too large and the viscoelastic material prolapses out as soon as you inject it." If there are choroidals, Dr. Kalenak recommended draining them only if they have been apposi- tional for 7-10 days, as they some- times recover on their own. Finally, the tube may need to be religated or stented; in this case, he said, be prepared to deal with high IOP immediately afterward. In worst cases scenarios, the tube may need to be removed. Dealing with tube retraction "Tube retraction occurs in only about 3% of tubes, and there are three reasons why tubes retract," said Kouros Nouri-Mahdavi, M.D., University of California, Los Ange- les. "These include too short place- ment of the tube during initial surgery, posterior migration of the plate, and eye growth in kids." The diagnosis of tube retraction can be made by gonioscopy to estab- lish that the tube tip is no longer in the eye, he said. For tubes placed posteriorly, B-scan ultrasonography can reveal whether there is a pocket of fluid around the plate or not. "There are two options for tube extension," said Dr. Nouri-Mahdavi. "There are commercial tube exten- der kits that allow us to cut and splice the existing tube, adding enough length to reinsert the tip into the eye. Alternatively, a 22- gauge angiocatheter is the ideal di- ameter to serve the same purpose and is readily available in all surgical centers." In summary, successful resolu- tion of post-op complications fol- lowing tube-shunt implantation depends on correct assessment of the situation as well as appropriate steps to manage the complications. Careful examination and prompt in- tervention can quell the post-op storm and lead to smooth sailing through the post-op period. EW Editors' note: The doctors mentioned have no financial interests related to their comments. Contact information Kalenak: j.kalenak@gmail.com Nouri-Mahdavi: nouri-mahdavi@jsei.ucla.edu Piltz-Seymour: jody.seymour@hotmail.com Radcliffe: nmr9003@med.cornell.edu February 2011 October 2011 According to Dr. Piltz-Seymour, surgeons should expect a transient hypertensive phase when using a non-valved implant, such as the Baerveldt device (pictured here) Source: Steven J. Gedde, M.D. 84-88 Glaucoma_EW October 2011-DL2_Layout 1 9/29/11 4:10 PM Page 84

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