Selective laser trabeculoplasty retreatment after prior argon laser trabeculoplasty: 1-year results

Abstract

Background: Argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT) are treatments for open-angle glaucoma. Many patients have previously received ALT but could benefit from further treatment. The purpose of this study was to examine whether SLT provided clinical benefit for patients who had previously received complete argon treatment. Methods: This was a prospective, partially randomized, comparison study. The study compared the effect after 1 year of SLT in patients with open-angle glaucoma (primary, pigmentary, or pseudoexfoliation) who had previously received 360° of ALT with the effect of laser treatment (ALT or SLT) given for the first time in patients with this condition. Ninety-six subjects were given 180° of laser trabeculoplasty. When both eyes qualified for treatment, the first eye treated was included in the analysis. Twenty-seven subjects were treated with SLT after previously receiving 360° of ALT therapy; the remainder were given their first laser treatment, 30 being randomly assigned by coin toss to receive SLT and 39 to receive ALT. Results: The mean intraocular pressure (IOP) before treatment was 21.5 mm Hg (SLT after ALT), 22.9 mm Hg (SLT), and 22.0 mm Hg (ALT), with no statistical difference among the groups ( p > 0.05). The mean IOP at 1 year was 16.7 mm Hg (SLT after ALT), 17.1 mm Hg (SLT), and 16.4 mm Hg (ALT). The IOP for all 3 groups was statistically significantly lower than at baseline ( p < 0.001), but there were no differences among the groups in this respect ( p > 0.05). At 1 year, the percentage IOP reductions from baseline were 23% (SLT), 19.3% (SLT after ALT), and 24% (ALT). There were no differences among the groups in the number of medications used before the laser, although there was a small but statistically significant decrease in the number of medications used before or after the laser treatment in both the SLT and the SLT after ALT group, but not the ALT group. Interpretation: SLT retreatment can produce a clinically useful decrease in IOP at 1 year, similar to that obtained by ALT, in patients who have had prior argon laser treatment. SLT may be a useful adjunctive therapy when 360° of ALT has already been performed.