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FEATURE
EXPANDING UTILIZATION OF SLOW-COAGULATION TSCPC This conjunctiva-sparing procedure is relatively noninvasive, safe, and effective. BY ABDELRAHMAN M. ELHUSSEINY, MD, MSC; MOHAMED M. KHODEIRY, MD; MOHAMED S. SAYED, MD; AND RICHARD K. LEE, MD, PHD
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ver the years, various cyclodestructive procedures have been developed for the treatment of glaucoma, including cyclodiathermy, cyclocryotherapy, beta irradiation, microwave therapy, ultrasonography, Nd:YAG laser therapy, semiconductor laser therapy, and surgical ciliary body resection. These techniques have not, however, gained substantial popularity because of the severe complications associated with their use. Cyclodestruction was consequently reserved primarily for eyes with endstage glaucoma, for eyes with elevated IOP and poor visual acuity potential, or for pain relief in eyes with poor or no vision. The introduction of the cyclodiode laser represents a significant advance, as it offers safer and more efficacious ciliary body ablation to control IOP. With this approach, the diode laser energy is absorbed by the ciliary body melanin pigments, and treatment can be applied to the ciliary body via an extraocular transscleral or direct intraocular approach. With traditional continuous wavetransscleral cyclophotocoagulation (CW-TSCPC), 1,750 to 2,000 mW of laser energy is applied for 2 seconds. Power is increased until an audible “pop” occurs and subsequently reduced to subthreshold levels.
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Although this technique is effective for IOP reduction, its use is limited to eyes with refractory glaucoma or low vision potential owing to severe inflammation and the high risk of complications. A recent systematic review by Souissi and colleagues summarized visionthreatening complications associated with traditional CW-TSCPC, including the loss of at least 2 lines of visual acuity (11%–55%), hypotony (3%–39%), phthisis (1.2%–9.9%), corneal decompensation (1%–10%), inflammation (1.9%–20%), and choroidal detachment (1%–20%).1 A report by the AAO reviewed literature evaluating the effectiveness and safety of traditional TSCPC that was published between the years 1968 and 2000.2 The investigators concluded that TSCPC was indicated for patients with refractory glaucoma in whom filtering surgeries had failed and for individuals with low vision potential. The report was published a quarter of a century ago—before significant advances in TSCPC, the introduction of slow-coagulation (SC) parameters, and the development of micropulse transscleral laser treatment.
SC-TSCPC In 2009, Gaasterland proposed using “popless” and SC laser parameters (1,250 mW for 4 seconds)
instead of the aforementioned traditional CW-TSCPC parameters.3 We view SC-TSCPC as the least invasive of currently available MIGS procedures. The SC parameters have rendered the TSCPC procedure safe and well tolerated, cost-efficient, reliable, and effective in reducing IOP. The low amount of energy delivered is unlikely to cause implosive “pop” ciliary body damage, suggesting a modified mechanism for IOP reduction. One hypothesis is that SC-TSCPC shrinks the ciliary processes, causes posterior movement of the peripheral iris, and improves aqueous drainage through the trabecular meshwork.4 Our retrospective case series compared the outcomes of conventional pop-titrated CW-TSCPC (n = 26 eyes) versus SC-TSCPC (n = 52 eyes) for any type or stage of glaucoma.5 The procedures were similar in terms of IOP reduction and visual acuity outcomes. The mean number of complications, however, was significantly higher in the CW-TSCPC than the SC-TSCPC group (1.46 ±1.24 vs 0.62 ±0.75). Sheheitli and colleagues6 evaluated the effectiveness of SC-TSCPC as a primary surgical intervention for medically uncontrolled glaucoma. Forty-eight eyes were divided into two groups based on preoperative IOP: (1) low IOP (≤ 21 mm Hg) and