Eyeworld

EW GLAUCOMA 86 March 2018 Device focus by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer most of the day. In addition to hav- ing similar pressure lowering effects as SLT, transscleral SLT causes less iritis and less pressure spikes. So if you now have a way to do SLT trans- sclerally using your existing laser, no lens, in a manner more comfortable for the patient, with more rapid visual recovery, less pressure spikes, and less inflammation, it seems like a major step forward." Clinical trial Evidence in support of the efficacy comes from a prospective random- ized interventional case series that investigated transscleral SLT in 30 adult patients with POAG or PXFG. The investigators found transscleral SLT, without the use of a gonioscopy lens, to be a safer technique than SLT, with a therapeutic potential comparable to that of the conven- tional method. 1 SLT was delivered to the study group without a gonioscopy lens, while a control group received con- ventional SLT therapy that involved 100 laser spots delivered for 360 degrees of the trabecular meshwork. The study group underwent irradia- tion using the same parameters with the laser applications administered on the perilimbal sclera. Outcomes revealed similar IOP reductions be- tween study group patients and con- trols of roughly 20%. Success was defined as a decrease in IOP of at least 15% at 6 months following the treatment, with no additional med- ications, laser, or glaucoma surgery. This was achieved in 12 (85.7%) study patients and nine (69.2%) controls (P=.385). Complications were mild and transient in the study group, although significantly higher in controls (P<.0001) and included anterior chamber inflammation and superficial punctate keratitis. The authors proposed that laser coherency, lost in tissue transmis- sion, was not required to achieve the therapeutic effect, and that the mechanism of action of external irradiation was similar to that of conventional SLT. They concluded that gonioscopy was therefore not necessary for laser energy delivery in SLT. 2 While the study's outcomes support the transscleral approach, Specialists are intrigued by the simplicity of the procedure and by the evidence backing it, but they want to see more data S elective laser trabecu- loplasty (SLT) applied directly to the perilimbal sclera (transscleral SLT) is emerging as a powerful tool in lowering IOP. New evidence suggests that it may be applicable in more types of glaucoma and cause fewer complications than conven- tional SLT. In the absence of large, long-term clinical trials, however, how is transscleral SLT perceived among experienced eye doctors? EyeWorld spoke with glaucoma specialists Nathan Radcliffe, MD, clinical professor of ophthalmology, New York University Langone Medi- cal Center, New York, and Tania Tai, MD, assistant professor of ophthal- mology, New York Eye and Ear Infir- mary of Mount Sinai, Icahn School of Medicine at Mount Sinai, New York, to learn if they have embraced this novel treatment and why. SLT has been widely used to lower IOP in glaucoma patients for close to 20 years. In SLT, laser energy is fired through the cornea and into the trabecular meshwork for 360 degrees, with the help of a gonioscopy lens that is used to visualize the chamber angle. The outcome is improved aqueous drain- age that markedly lowers IOP and often relieves patients of glaucoma medications. The treatment employs an Nd:YAG laser system with 400 µm spot size, 3 nanoseconds of laser duration, at laser power settings of 0.6 mJ–1.0 mJ. "Transscleral SLT is the same as SLT. It employs the same laser using the same power settings, but the difference is that you fire the laser energy through the sclera directly at the trabecular meshwork, without a gonioprism," Dr. Radcliffe told EyeWorld. "It is a faster procedure than SLT, which is much more com- fortable for the patient. Having the gonioprism on the eye is uncomfort- able, and using it requires a cou- pling solution that blurs vision for Transscleral SLT Left eye with corneal clouding Right eye with clear cornea Two eyes now treatable with one laser technique. This patient's right eye is pictured with normal anterior segment anatomy and an open angle on gonioscopy. SLT can be applied through the traditional technique. The left eye is also pseudophakic but has a cloudy cornea from endothelial dysfunction, preventing visualization of the angle structures. While the left eye might not typically be considered a candidate for traditional SLT, it would be an excellent candidate for transscleral SLT. Source: Nathan Radcliffe, MD

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