Evaluation of a modified protocol for selective laser trabeculoplasty

Purpose: To compare the intraocular pressure (IOP) response to a modified protocol for selective laser trabeculoplasty (SLT) to standard protocols for SLT and argon laser trabeculoplasty (ALT). Materials and Methods: A retrospective study of 318 eyes of 284 patients diagnosed with either primary open angle, pigmentary or pseudoexfoliation glaucoma who underwent laser trabeculoplasty from September 1997 to September 2005. One hundred and two patients, who underwent a modified SLT protocol with 100 overlapping laser spots over 180 degrees of trabecular meshwork were compared with 89 patients who received SLT with 100 nonoverlapping spots over 360 degrees and another 127 patients who received ALT with 50 spots over 180 degrees. IOPs were measured at baseline and postoperatively at 1 hour, 6 weeks, 4 months, and 14 months. Regression models, based on the observed data, were used to predict the fall in IOP in the 3 groups, controlling for differences in baseline pressure. Results: The IOP response to overlapping SLT was significantly worse than to nonoverlapping SLT or ALT, both of which had similar responses. Baseline IOP was the only preoperative factor that predicted response to ALT (P < 0.0001) and nonoverlapping SLT (P = 0.0019) at all follow-up times. There were no statistically significant predictive factors for IOP reduction in the overlapping SLT group. Conclusions: Overlapping application of SLT results in a poorer IOP response compared with ALT and nonoverlapping SLT.