Eyeworld

EW GLAUCOMA 34 May 2018 Research highlight by Maxine Lipner EyeWorld Senior Contributing Writer didn't appear so may have thicker tissue that may preclude the ability of trypan blue to diffuse into the bleb. Similarly, bottle height might affect the speed of trypan blue diffu- sion into the filtering bleb. Preemptive procedures "Despite these weaknesses we theo- rized that the use of trypan blue is able to detect whether or not there is normal physiological flow into the filtering bleb," he said. "As a result, it might be a sign of bleb health intraoperatively." This could have important clinical implications. "For example, if you have a patient who has poor bleb staining, you can tell them beforehand that you would like consent for bleb needling with mitomycin-C in combination with the cataract surgery," Dr. Yung said. In eyes with poor intraocular bleb staining, practitioners may elect to do such bleb needling at the time of the cataract procedure to reduce the need for additional medications or subsequent glaucoma surgery. Although the study is limited by population size, Dr. Yung hopes that practitioners come away from this with the message that the intensity of the bleb staining with trypan blue during cataract surgery showed a trend toward IOP-lowering medica- tions and surgical interventions in eyes that had less bleb staining. Dr. Yung views this as an example of a use for trypan blue separate from the classic capsular staining. While prior bleb staining has been done using ICG or fluores- cein, he thinks that because trypan blue is commercially available and approved for cataract surgery, it is a natural option. "I think that this can potentially help guide us in terms of choosing what kind of sur- gery we should perform on patients who have had a prior filtering bleb," he concluded. EW Reference 1. Yung ES, et al. Trypan blue for the assess- ment of filtering bleb function during cataract surgery. J Glaucoma. 2018;27:246–250. Editors' note: Dr. Yung has no financial interests related to this comments. Contact information Yung: Cal.edyung@gmail.com significant changes," Dr. Yung said. "However, when it came to the need for additional IOP-lowering medi- cations, there was a trend toward a lower need for additional intraocu- lar pressure medications to control the pressure adequately, with a P value of less than 0.1." Investigators determined that for patients with significant bleb staining, there were none who re- quired additional glaucoma surgical intervention. However, for those who had minimal to mild staining of the bleb, it was a different story. "There were two patients who did require additional filtering proce- dures that were noted during our study," Dr. Yung said. "There was a trend toward an additional need for greater medications in that group, as well as a greater need for glaucoma surgical intervention." This was not statistically significant but warrants further investigation, he noted. The hypothesis is that using trypan blue allows investigators to gauge the degree of physiological flow between the anterior chamber and the filtering bleb, Dr. Yung ex- plained. He acknowledged that there may be weaknesses to this particu- lar technique, such as the fact that certain blebs that did filter well but increased intraocular pressure after cataract surgery." Included were patients older than 21 who had a history of either primary open angle glaucoma or secondary glaucoma, who had undergone a prior trabeculectomy with mitomycin-C, and who were scheduled for phacoemulsification. "These patients underwent a trabe- culectomy that took place at least 1 year prior to the scheduled cataract surgery," Dr. Yung said. During the procedure, investi- gators made a clear corneal incision for paracentesis wound. "We went in with an air bubble and injected a full vial of 0.5 milliliters of trypan blue into the anterior chamber, which was left in place for at least 10 seconds, with the eye kept at a pressure of 21 mm Hg during this time," Dr. Yung said. "We proceeded to irrigate the anterior chamber with sterile balanced salt solution and obtained photographs of the bleb at the time of irrigation and a second time at the conclusion of the case." Otherwise, phacoemulsification was carried out as usual. A total of 14 eyes of 14 patients were included in the final analysis. "It was inadequately powered to be able to detect the statistically What this may mean for filtering blebs during cataract surgery M ultiple studies have found an increased rate of failure in the exist- ing filtering bleb after a cataract surgery in patients who have had a trabeculec- tomy, according to Edward Yung, MD, Pacific Eye Institute, Upland, California. However, in a study published in the Journal of Glauco- ma, 1 investigators found that use of trypan blue during the cataract procedure may help point out cases where preemptive treatment can lower the need for medications as well as further surgery. Honing in on precarious patients The aim was to determine which pa- tients were at heightened risk with such procedures for raised intraocu- lar pressure that required additional intervention. "No studies have tried to predict whether or not a cataract surgery will cause failure in certain populations," Dr. Yung said. "We tried to figure out which patients are at risk of developing scarring and Going with the trypan blue flow For patients with minimal to mild bleb staining, additional glaucoma surgical intervention may be needed. Source: Edward Yung, MD

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