EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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60 EW GLAUCOMA February 2011 October 2012 Trabeculectomy tribulations after cataract surgery by Maxine Lipner Senior EyeWorld Contributing Writer Increased bleb failure risks in phakic patients P hakic glaucoma patients with cataracts who have undergone trabeculec- tomy are at increased risk of failure in terms of IOP control after subsequent phacoemul- sification. Results published in Archives of Ophthalmology show that the shorter the time between the procedures, the more apt the trabeculectomy is to fail, according to Rahat Husain, F.R.C.Ophth., Singapore National Eye Center, Singapore. While there had been some evidence from the literature that performing cataract surgery has a negative impact in terms of IOP control in patients who have had a previous trabeculectomy, there was nothing substantial. "Good quality evidence was lacking, and few stud- ies had examined the time between the two procedures," Dr. Husain said. "That was the main crux of this paper—we wanted to look at the influence of time between tra- beculectomy and cataract surgery and whether that was important." Considering phacoemulsification effects This cohort study with 235 glau- coma participants was part of an ear- lier randomized, controlled trial on the efficacy of intraoperative 5-FU augmented trabeculectomy compared to placebo. "We had this well-designed study and had been following up these patients prospec- tively for at least 3 years," Dr. EyeWorld factoid Glaucoma is the second leading cause of blindness in the world Source: World Health Organization Husain said. "So we had the data already in there." Investigators took that data and performed a multiple regression analysis to see what fac- tors were associated with trabeculec- tomy failure. "Into that we put in the time between trabeculectomy and cataract surgery as a time dependent variable to see if that was significantly associated with failure, and indeed it was," Dr. Husain said. When investigators considered the participants, they found that just over 50% had subsequent cataract surgery. The median time between the two procedures was 21.7 months. "Our main outcome was to see if time between tra- beculectomy and cataract surgery was significantly associated with trabeculectomy failure, and we found that it was," Dr. Husain said. "It just reached statistical signifi- cance at p=.049 with a hazard ratio of 1.7 for trabeculectomy failure." These results showed that the time between trabeculectomy failure and cataract surgery was significantly associated with trabeculectomy fail- ure, with shorter times being more likely to result in earlier failure. Dr. Husain was surprised that there wasn't a stronger association. "I think that's due to the fact that most of the subjects in our trial didn't have early cataract surgery (i.e., within 6 months of trabeculec- tomy)," he said. "The average time from trabeculectomy until cataract surgery was about 2 years." That's probably why this wasn't as high a hazard ratio. "There are reasons why cataract surgery is not performed so soon after trabeculectomy," he said. "If a patient with significant cataract is due to have a trabeculectomy, most surgeons will either take out the lens first or perform combined surgery." Clinical concerns From a clinical perspective, it's important to take into account whether glaucoma patients are phakic or pseudophakic. "If they are phakic, we've shown in a previous paper that trabeculectomy in itself, certainly in East Asian patients, does result in worsening of their cataract," Dr. Husain said. "If you embark upon trabeculectomy sur- gery on someone who is phakic, you have to accept that [the patient is] going to have worsening of the Using an anti-scarring agent such as 5-FU may help to improve bleb survival in phakic patients Source: Rahat Husain, F.R.C.Ophth. cataract that can happen quite soon, and subsequent cataract surgery is going to influence the longevity of the bleb survival." Aiming to perform the surgery in pseudophakic individuals is preferable, if possible. "Essentially, I feel that performing trabeculectomy surgery in pseudophakic patients will result in more likelihood of longer-term bleb survival," Dr. Husain said. "That's what I try to do in my clinical practice." Of course, this is not always possible. In cases where the patient is still phakic, practitioners must be careful not to traumatize the bleb itself and also be as meticulous as possible. "One should try and not leave any residual soft lens matter in the eye," Dr. Husain said. "I also give post-operative steroids for longer pe- riods of time—sometimes as much as 6 months." Also, at the end of trabeculectomy surgery, Dr. Husain thinks that there's good evidence for giving an anti-scarring agent such as MMC, 5-FU, or Avastin (beva- cizumab, Genentech, San Francisco) near the site of the bleb to improve its survival. Dr. Husain hopes that practi- tioners come away from the study with the understanding of the ad- vantage of performing trabeculec- tomy in pseudophakic patients. "The take-home message is that tra- beculectomies are less likely to fail if subsequent cataract surgery is not performed—the implication being that operating on a pseudophakic eye may be preferable. More evidence for this latter statement, however, still needs to be produced. If cataract surgery needs to be per- formed after trabeculectomy, try and leave as long a time as possible before taking out the lens," he said. Going forward, Dr. Husain hopes to investigate further to relative merits and problems associ- ated with trabeculectomy surgery performed on phakic eyes, pseudophakes, and combined pha- cotrabeculectomy. "Many centers worldwide are performing phacotra- beculectomy, but the concern is that that procedure, although it obviates the need for subsequent cataract sur- gery, may result in earlier loss of IOP control, although that's controver- sial." he said. "That is something that I would like to look into." EW Reference Husain R, Liang S, Foster PJ, Gazzard G, Bunce C, Chew PT, Oen FT, Khaw PT, Seah SK, Aung T. Cataract surgery after trabeculectomy: the effect on trabeculectomy function. Arch Ophthalmol. 2012 Feb;130(2):165-70. Editors' note: Dr. Husain has no finan- cial interests related to this article. Contact information Husain: 65 6227 7255, rahathusain@hotmail.com