Thesis (M.A.)--Boston University / During the past ten years argon laser trabeculoplasty (ALT) has evolved from a novel to a commonplace intervention in the management of open-angle glaucoma. Despite its widespread usage, the exact effect of ALT on the trabecular meshwork is only partially understood. Nonetheless, its effect of lowering intraocular pressure through enhancement of aqueous humor outflow is well documented. Laser photocoagulation of the trabecular meshwork focally destroys, but also diffusely stimulated trabecular meshwork cells. The laser induced shape alterations in the trabecular meshwork are thought to influence aqueous humor outflow only at very high intraocular pressure levels. It appears more probable that most of the aqueous humor outflow occurring after ALT results from laser induced metabolic changes within the cells of the trabecular meshwork. This review chronicles the history of the use of the laser in glaucoma management, the clinical experience and some of the experimental studies which have been conducted to answer the questions regarding the mechanism of action of ALT.

Purpose To investigate the efficacy of adjunctive selective laser trabeculoplasty (SLT) in reducing 24-h intraocular pressure (IOP) fluctuations and nocturnal IOP peaks. Methods In this prospective interventional case series, 157 medically treated eyes of 157 patients with primary open-angle glaucoma (POAG) who were assigned SLT to further reduce IOP were consecutively included. Each patient had a complete glaucoma work-up and 24-h IOP monitoring (6 measurements, including one in the supine position) taken before and on average 6 months after SLT. The main outcome measures were the reduction of 24-h IOP fluctuations and nocturnal peak IOP. Secondary outcome measures were success rates, factors influencing the reduction of high 24-h IOP fluctuations and nocturnal peak IOP, complications, and severe adverse events. Results Medicated mean 24-h IOP (mmHg) was statistically significantly reduced from 15.1 ± 2.6 to 13.8 ± 2.4 (P < 0.001) and IOP fluctuations from 6.5 ± 2.7 to 5.4 ± 2.6 (P < 0.001) 6 months after SLT. Ninety-four eyes (59.9%) initially had high IOP fluctuations (more than 5 mmHg). These were reduced from 8.1 ± 2.3 to 5.6 ± 2.7 at 6 months (P < 0.001). Fifty-two eyes (55.3%) had fluctuations below 5 mmHg post-SLT which was defined as success. Fifty-one patients (32.5%) had nocturnal IOP peaks. In these cases, nocturnal IOP was reduced by 19.2% from 20.1 ± 3.4 to 16.2 ± 3.3 mmHg at 6 months (P = 0.001). Conclusions The current study demonstrates that adjunctive SLT not only reduces mean 24-h IOP in treated POAG patients, but also has an additional benefit in reducing IOP fluctuations and nocturnal peak IOP.

Purpose To evaluate the effectiveness and safety of Selective Laser Trabeculoplasty (SLT) with the SLT mode of the VISULAS ® green laser in patients with primary open-angle glaucoma (POAG). Methods This prospective, interventional multicenter clinical investigation included patients with POAG who either needed a treatment escalation because the individual intraocular pressure (IOP) target was not met or treatment initiation and had an IOP ≥ 17 mmHg at baseline in the study eye. The study was conducted in five research centers across Germany. Approximately 100 laser applications were delivered to 360° of the trabecular meshwork. Glaucoma medications were not modified during the 3-month follow-up to allow evaluation of the sole effect of VISULAS ® green with SLT. Efficacy outcomes were postoperatively absolute and relative IOP changes at 1 and 3 months. Safety outcomes analyzed the rate of intra- and postoperative adverse events. Results Thirty-four eyes of 34 POAG patients were included. The overall mean number of preoperative glaucoma medications was 2.2 ± 1.4 in 29 treated eyes, 5 eyes were treatment naïve. Mean baseline IOP (mmHg) was 21.0 ± 2.69 and was reduced by − 3.53 ± 3.34 [95% CI − 4.61; − 2.45] and − 3.59 ± 3.41 [95% CI − 4.64; − 2.53] at the 1- and 3-month follow-up, respectively (p < 0.0001), with 48.5% of cases achieving a ≥ 20% IOP reduction at 3 months [95% CI = 30.8%; 66.5%]. The mean relative IOP reduction was − 16.4% and − 16.3% at 1 and 3 months, respectively (p < 0.0001). Potentially device- or procedure-related adverse events were mild to moderate and included 3 postoperative IOP-spikes and 6 reports regarding eye pain and discomfort. All were resolved without sequelae. Conclusions SLT performed with the VISULAS ® green laser achieved clinically significant additional IOP reductions in medically treated as well as in treatment naïve eyes with POAG and there were no relevant safety issues. The results are comparable to other reported SLT studies.