Authors: Cindy Hutnik, Andy Crichton, Bryce Ford, Marcelo Nicolela, Lesya Shuba, Catherine Birt, Enitan Sogbesan, Karim Damji, Michael Dorey, Hady Saheb, Hui Guo, Neil Klar, Darek Gozdzik, William Hodge
Author Disclosure Block: C. Hutnik: None. A. Crichton: None. B. Ford: None. M. Nicolela: None. L. Shuba: None. C. Birt: None. E. Sogbesan: None. K. Damji: None. M. Dorey: None. H. Saheb: None. H. Guo: None. N. Klar: None. D. Gozdzik: None. W. Hodge: None.

Abstract Body:

Purpose: To compare the 1 year IOP lowering effect between selective laser trabeculoplasty (SLT) and argon laser trabeculoplasty (ALT) on patients who were already treated with 360-degree SLT previously.

Study Design: This is the first multicenter, patient-masked, RCT looking at SLT repeatability.

Methods: Patients were recruited from seven Canadian academic centers. We randomly assigned eligible patients, who had previous 360-degree SLT, to receive either 180-degree SLT or 180-degree ALT. The primary outcome was IOP change from baseline to 12 months. The analysis was performed for the complete cases and repeated for the per protocol patients. This trial was registered on ClinicalTrials.gov, number NCT01687465 and was funded by CIHR.

Results: We enrolled 137 participants between February 14, 2013 to October 24, 2016. Randomization was balanced. Diagnosis included primary open angle glaucoma (POAG), pigmentary dispersion syndrome (PDS), pseudoexfoliation syndrome (PXF), and ocular hypertension (OHT). Baseline IOP was 21.67 mmHg (SD 3.15) in the SLT group and 21.77 mmHg (SD 3.35) in the ALT group. At 12-month follow-up, mean IOP reduction was 3.35 mmHg (SD 4.96) for the SLT arm and 3.36 (SD 5.06) for the ALT arm. The difference was -0.01 mmHg (95% CI, -1.86 to 1.84; p = 0.99) for the complete cases and 0.86 mmHg (95% CI, -0.68 to 2.41; p = 0.27) for the patients without protocol deviation. One patient (2%) in the SLT group and 4 (7%) in the ALT group progressed to surgery (RR 0.25 p = 0.22). No IOP spike (IOP elevation > 5 mmHg at 1 hour) was detected in either group.

Conclusions: There are two main conclusions from this study: (1) 180-degree SLT is effective when done after previous complete SLT but ALT can also be used with equal effectiveness in this setting. (2) Although both lasers were effective, IOP reduction was only about 50% of what is typically obtained from laser angle surgery in virgin eyes. An ongoing open label study of these patients is in progress to determine the IOP lowering effects of even further SLT treatments.