This is a retrospective extension of an initially prospective interventional multicenter 3 months clinical investigation using the VISULAS® green SLT in patients with POAG, who either needed a treatment escalation or commenced treatment and had an IOP ≥ 17mmHg at baseline, with no previous glaucoma or other ocular surgery [5].

At 12 months, 94.7% of patients from the SGT group showed an IOP reduction of ≥ 10% compared to the baseline values. Meanwhile, a ≥ 20% reduction of IOP from baseline was seen in 52.6% of the cases in the SGT group. Adverse events were mild and, in most cases, not directly related to the procedure, and only the commonly noted side effects of SLT were observed: transient IOP spikes, eye pain, or discomforts. These are known side effects of SLT with incidence comparable to the literature [14].

Success of SLT treatment is commonly defined as the proportion of eyes that achieve a reduction in IOP of ≥ 20% from baseline without an increase in glaucoma medication and/or repeat glaucoma laser or surgical procedure [7]. According to this definition, success was achieved in 52.6% of eyes in the SGT group in our study, which is similar to results reported by other SLT studies [15].

Further, our study reports 12.8% IOP reduction from baseline at 6 months and 18.8% reduction at 12 months in the SGT group. These results are similar to other documented SLT studies [16,17,18,19]. In a systematic review, Wong et al. [16] found a mean relative IOP reduction of 14.7% from a baseline IOP of 21.3 ± 4.7 mmHg, with 40.3% showing a ≥ 20% IOP reduction 12 months post-SLT. In another 2020 retrospective study, Elahi et al. [17]. documented a 17.6% reduction in IOP from baseline at 12 months, with a 27.4% success rate. In a similar 6-month study by Chadwick et al. [18], a mean relative IOP reduction of 16.7% was found 6 months post-SLT. According to the previous studies, the only identifiable factor influencing IOP post-SLT was the baseline IOP: the higher the baseline IOP, the greater the reduction in IOP observed post-procedure [7, 13, 20]. This was also noted in our study population.

Another noteworthy observation was that SLT does not have a 100% success rate and may not work on all patients. Our study had 5 patients (20%) who had uncontrolled IOP and had to be treated with secondary procedures like routine SLT/iStent/increase in glaucoma medications, and this is aligned with other studies in the literature [13, 15].

The cause for a significant number of eyes not responding sufficiently to SLT remains uncertain. Recent evidence suggests that POAG might impact not only the trabecular meshwork but also structures beyond it, such as Schlemm’s canal and the collector channels. Genetic variations also contribute to this phenomenon. Consequently, if the outflow resistance is primarily caused by issues in Schlemm’s canal or the collector channels, a targeted therapy focused on the trabecular meshwork, like SLT, may not be effective in all cases [21, 22].

The most common ocular adverse events noted during SLT include mild and transient eye discomfort or pain and post-procedure IOP spikes. The eye pain and discomfort were mainly experienced immediately after the procedure and were often associated with the use of the contact lens during the process. Additionally, transient increase in IOP is a frequently reported side effect of SLT and was noted in 3 patients out of 34 of the original cohort (8.8% – incidentally, they are all in the SGT group) in the current study, which is in accordance with the previous studies: Wong et al. found that the incidence of IOP spikes varies between 0% to 28.8% [15]. Similarly, Latina et al. reported that 24% of cases experienced transient IOP spikes of 5 mmHg or more [23].

Notably, none of the cases in this study exhibited severe uveitis, corneal edema with stromal haze, choroidal effusion, hyphema, or peripheral anterior synechiae, nor did they experience retinal complications such as cystoid macular edema or macular burns. Although these complications are rare, they have been reported in some instances following SLT [14, 15].

Limitations of our study include a retrospective design, along with a small sample size. Further, the IOP measurements in the extension study were neither masked nor taken at the same time of the day for each patient, which does not exclude the effect of diurnal variations. Also, this study was conducted exclusively on white/European patients, and most of them had mild to moderate trabecular meshwork pigmentation; therefore, the conclusions drawn from this study may not be generalizable to patients of other ethnicities or those with different degrees of trabecular meshwork pigmentation. Finally, it was focused solely on patients diagnosed with POAG. Further studies with a larger sample size, different ethnicities, and masked IOP measurements can add to our information. An important strength of the present study is the subgroup evaluation of the effect of SLT on a group without any change in glaucoma medication or treatment (stable glaucoma treatment group).

To summarize, the use of the VISULAS® green laser for SLT exhibited substantial effectiveness in lowering IOP in eyes diagnosed with primary open-angle glaucoma. Approximately half of the treated eyes achieved an additional 20% reduction in IOP, establishing clinically significant efficacy. The success rates observed in this study are comparable to those reported in the literature when using other conventional SLT lasers. Furthermore, SLT with the VISULAS® green laser demonstrated a favorable safety profile, aligning with previous reports on the safety of SLT procedures. Overall, these findings indicate that SLT with the VISULAS® green laser can be considered a viable and safe treatment option for managing IOP in patients with POAG.