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William Hodge, Cindy M L Hutnik, Andrew C Crichton, Bryce Ford, Catherine M Birt, Marcelo T Nicolela, Lesya Shuba, Karim F Damji, Michael Dorey, Enitan Sogbesan, Hady Saheb, Hui Guo, Neil Klar; A Randomized Clinical Trial of SLT vs ALT in Patients Who Have Already Received 360 Degrees of SLT-The Canadian Laser Study Trial Network.. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3461.
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© ARVO (1962-2015); The Authors (2016-present)
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.
This is the first multicenter, patient-masked, RCT looking at SLT repeatability. It was a multicenter RCT performed at 7 Canadian centers and funded by The Canadian Institute for Health Research. The study recruited 137 patients and met its a priori sample size/power calculations. This is the first public presentation of this work.
We enrolled all 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.
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%-67% of what is typically obtained from laser angle surgery in laser naive eyes. We hypothesize that original SLT does cause some anatomical or physiological change to the trabecular meshwork as efficacy of BOTH SLT and ALT is reduced after initial SLT. An ongoing open label study of these patients is in progress to determine the IOP lowering effects of even further SLT treatments.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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