SLT an evolutionary approach to glaucoma

Selective laser trabeculoplasty (SLT) is a new treatment option for glaucoma that has significant advantages over argon laser trabeculoplasty (ALT) with equal or better outcomes. Although studies are still under way, SLT may have important implications for primary glaucoma therapy.

SLT versus ALT Studies comparing ALT and SLT have found that the two procedures provide similar decreases in IOP.

A randomized, controlled clinical trial conducted by Karim Damji, MD, of the Ottawa Health Research Institute, Ottawa, and colleagues compared patients who had undergone SLT with those who had undergone ALT. Three years after the procedure, both groups were doing equally well. Patients who underwent ALT had an average IOP of 17 mm Hg, while those in the SLT group had an average IOP of 18 mm Hg.

This study included patients who had previously undergone failed ALT. Those who were randomly assigned to a second ALT procedure did not do well; however, the patients who were randomly assigned to SLT did just as well as the rest of the SLT group.

A recent study conducted by Mark Juzych, MD, of the Kresge Eye Institute, Detroit, and colleagues compared the long-term outcomes of SLT and ALT in patients with open-angle glaucoma. The researchers found similar outcomes for both success endpoints in this study: A decrease in IOP of 3 mm Hg or more with no additional medication, laser, or glaucoma surgery; and IOP reduction of 20% from baseline, with no additional medicine, laser, or glaucoma surgery.

Although outcomes are similar, SLT has a number of advantages over ALT:

SLT as primary therapy? For these reasons, many ophthalmologists are using or considering SLT as first-line therapy. The Glaucoma Laser Trial demonstrated that initial ALT was equivalent to initial medical therapy. SLT appears to be at least as efficacious as ALT with less risk, so primary SLT may be an option. However, a randomized clinical trial will be necessary to determine whether SLT has a role as primary glaucoma therapy.

A study that Madhu Nagar, MD, of the Clayton Eye Centre, Wakefield, England, presented at the 2003 American Academy of Ophthalmology annual meeting showed that primary SLT can result in a dramatic reduction in IOP. Her study compared results in four groups of patients: Patients who received SLT treatment over 90°, 180°, or 360° of the trabecular meshwork, and those being treated with prostaglandin analog medical therapy. The most aggressive SLT treatment resulted in IOP reductions comparable with what patients on the best medical therapy available experienced.

Baron Williamson, MD, of the Williamson Nelson Eye Center, Baton Rouge, LA, has also found that more aggressive SLT treatment yields better results. Demographically matched groups were treated either aggressively (439 patients) or conservatively (687 patients). The aggressive group received approximately 150 contiguous spots with 30% overlap over 360°, with sufficient energy for consistent "minibubble" formation on almost every pulse. The conservative group was treated with 50 to 75 adjacent non-overlapping spots, 180+° nasal, and the energy was varied to get no tissue response or just the occasional "minibubble."

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