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32 EW GLAUCOMA July 2013 February 2011 Repeatability of selective laser trabeculoplasty by Tony Realini, MD Can SLT be safely and effectively repeated when its initial effect wears off? T he ebb and flow of laser trabeculoplasty's popularity as a means of lowering intraocular pressure (IOP) in patients with open-angle glaucoma (OAG) can be pegged to a series of advances in both medical and laser technology.1 First described on the argon laser platform by Wise and Witter in a seminal paper in 1979,2 the argon laser trabeculoplasty (ALT) procedure gained a following as a result of the NIHsponsored Glaucoma Laser Trial demonstrating its safety and efficacy compared to topical medical therapy in the days of timolol and pilocarpine. With the introduction of the first prostaglandin analogue— latanoprost—in 1996, the utilization of trabeculoplasty waned. Then, with the 2001 advent of selective laser trabeculoplasty, trabeculoplasty was repopularized. SLT's differences from the older argon-based procedure—lower energy, bigger spot size, ease of teaching the skill to residents, among others—have been well described since its development more than a decade ago. One potential difference that continues to generate discussion and controversy is repeatability. ALT caused significant photocoagulative damage to the meshwork, which became cumulative with repeated therapy and led to relatively high rates of persistent IOP elevation, limiting its long-term use. SLT has been characterized as a kinder, gentler ALT, causing much less tissue damage. This has led to speculation that unlike ALT, SLT may be more safely repeatable when its effect in- variably wears off. A retrospective study published in 2010 showing efficacy of repeat SLT fueled the fire of this speculation.3 At this year's Association for Research in Vision and Ophthalmology meeting in Seattle, two groups reported additional retrospective data supporting the repeatability of SLT. frames. Repeat SLT successfully lowers IOP in African Americans at 1215 months and 21-30 months. "The average IOP continued to go down with longer follow-up, most likely because the higher IOP failures went on to incisional surgery and were removed from the analysis," Dr. Eliassi-Rad said. "In the few patients who have come to third SLT, the mean IOP has dropped from 20.8 mm Hg to 13.4 mm Hg," said Dr. Golez. "Overall, the percent IOP drop after first, second, and third SLT was remarkably consistent at 39%, 33%, and 36%, respectively." Repeat SLT in AfricanAmericans Repeat SLT in pseudoexfoliation glaucoma Data continue to emerge supporting the efficacy of repeat SLT in patients whose first procedure has worn off. These small data sets limit any meaningful conclusions about safety. However, it is worth noting that in the 12 years since SLT was introduced, there have been no cases of complications with repeat SLT reported in the medical literature, to the manufacturer, or to the FDA. Based on the data available at present, repeat SLT seems a reasonable option for therapy in patients who had a good response to initial SLT but have subsequently lost IOP control. EW Babak Eliassi-Rad, MD, Boston University, presented a retrospective analysis of 22 African-American patients who underwent repeat SLT after the IOP-lowering effects of initial SLT wore off. "These were patients on maximally tolerated medical therapy," he explained. "Most were on a prostaglandin analogue, a beta-blocker, and either a carbonic anhydrase inhibitor or an adrenergic agonist." His team collected data on both initial and repeat SLT efficacy. After initial SLT, mean IOP dropped from a baseline of 20.5 mm Hg to 18.5 mm Hg at 6-9 months post-treatment, 17.8 mm Hg at 1215 months post-treatment, and 15.4 mm Hg at 21-30 months post-treatment. When asked why patients with relatively modest responses to initial SLT underwent repeat SLT, he said, "These were patients who presented with inadequate IOP control on maximally tolerated medical therapy after an initial SLT and they were headed for the operating room. These were the patients who were highly motivated to avoid surgery and wanted to try repeat SLT." In his data set, IOP after repeat SLT dropped from a baseline of 18.9 mm Hg to 16.5 mm Hg, 16.0 mm Hg, and 15.4 mm Hg, respectively, at the same post-treatment time A bleb continued from page 31 Editors' note: Dr. Fudemberg has financial interests with Allergan (Irvine, Calif.). Dr. Myers has no financial interests related to the article. Dr. Safran has financial interests with Bausch + Lomb (Rochester, N.Y.), Ellman (Oceanside, N.Y.), and Heidelberg (Heidelberg, Germany). Dr. Smith has no financial interests related to this article. Contact information Fudemberg: sjf003@gmail.com Myers: jmyers@willseye.org Smith: olutos@yahoo.com Ernesto Golez, MD, a fellow in training under Mark Latina, MD (the developer of the SLT platform), at the Massachusetts Eye and Ear Infirmary, also presented a retrospective analysis of repeat SLT, focusing on patients with pseudoexfoliation glaucoma. Dr. Golez said, "Pseudoexfoliation glaucoma is more aggressive than primary OAG, and it generally requires more complicated treatment than POAG." Also, he added, pseudoexfoliation is a primary outflow disease related to clogging of the meshwork with pseudoexfoliation material, which should be particularly amenable to a procedure designed to improve trabecular outflow. The research team reviewed the charts of 79 eyes of 56 patients with or without prior medical therapy who had undergone initial SLT. Of these, 43 eyes (54%) remained controlled through last follow-up with no further intervention, 15 eyes (19%) underwent incisional surgery, and 21 eyes (27%) underwent repeat SLT. The average time between initial and repeat SLT was 29 months. "Initial SLT lowered mean IOP from 22.6 mm Hg to 13.9 mm Hg, with no change in the mean number of medications used," said Dr. Golez. "Repeat SLT lowered IOP from 21.5 mm Hg to 14.3 mm Hg, although there was a slightly higher rate of medication use after repeat SLT." Of the 21 eyes undergoing repeat SLT, 11 (52%) remained controlled with no further intervention, five (21%) underwent incisional surgery, and five (21%) underwent a third SLT procedure. The average time between second and third SLT was 17 months. Clinical implications References 1. Ramulu PY, Corcoran KJ, Corcoran SL, Robin AL. Utilization of Various Glaucoma Surgeries and Procedures in Medicare Beneficiaries from 1995 to 2004. Ophthalmology 2007;114:2265-70. 2. Wise JB, Witter SL. Argon laser therapy for open-angle glaucoma. A pilot study. Arch Ophthalmol 1979;97:319-22. 3. Hong BK, Winer JC, Martone JF, Wand M, Altman B, Shields B. Repeat selective laser trabeculoplasty. J Glaucoma 2009;18:1803. Editors' note: Dr. Realini has financial interests with Alcon (Fort Worth, Texas), Sucampo (Bethesda, Md.), Sensimed (Lausanne, Switzerland), and Lumenis (Yokneam, Israel). Drs. Eliassi-Rad and Golez have no financial interests related to this article. Contact information Eliassi-Rad: Babak.eliassi-rad@bmc.org Golez: docernie3g@hotmail.com