advertisement
Editors Selection IGR 25-4
Laser Treatment: Gonioscopy-free DSLT: a worthy alternative to conventional SLT?
Comment by Tony Realini on:
127613 Randomized Noninferiority Trial of Direct Selective Laser Trabeculoplasty in Open-Angle Glaucoma and Ocular Hypertension: GLAUrious Study, Gazzard G; Congdon N; Azuara-Blanco A et al., Ophthalmology, 2025; 132: 1091-1104
Gazzard and colleagues have recently reported the results of the pivotal GLAUrious study of direct selective laser trabeculoplasty (DSLT) for the treatment of open-angle glaucoma (OAG) or ocular hypertension (OHT). In contrast to conventional SLT, DSLT is a completely non-contact approach in which laser energy is delivered ab externo directly to the ocular surface in the limbal region and reaches the trabecular meshwork by traversing the conjunctiva, Tenon’s capsule, the episcleral, sclera, and the outer and inner walls of Schlemm’s canal. DSLT is performed using a proprietary system that autofocuses, auto-aligns, and automatically delivers 120 treatment spots around the limbus in just a few seconds. Proposed benefits of DSLT over SLT include eliminating the goniolens and coupling agent, resulting in a faster, simpler, and more patient-friendly procedure. The GLAUrious study compared DSLT to SLT in 192 participants with OAG or OHT and intraocular pressure (IOP) between 22-35 mmHg after washout of any IOP-lowering medications. Only one eye per participant was included. The study eye was the one with higher washout IOP; the non-study eye resumed topical IOP medications after washout. This introduces the possibility that some participants received topical beta-blockers in the non-study eye which may have contributed to study-eye IOP reductions via the contralateral crossover effect. The primary outcome of the study was the mean reduction in IOP from washout to month 6, and the study was designed and powered to demonstrate that DSLT was noninferior to SLT. In fact, the study results demonstrated that 6-month IOP reduction was DSLT was not non-inferior to SLT. Mean IOP reduction with SLT was 6.2 mmHg and with DSLT was 5.5 mmHg; the 95% confidence interval of the difference overlapped the prespecified noninferiority margin (-1.95 mmHg), thus noninferiority was not demonstrated. This result may have resulted from underpowering of the study, as the sample size was calculated using an assumed standard deviation (SD) that was smaller than the actual observed SD, resulting in lower than anticipated power. Irrespective of the significance of the efficacy results relative to standard SLT, there are other reasons to approach DSLT with caution. To date, fewer than 210 patients with OAH or OHT undergoing DSLT have been reported in the Pubmed-indexed literature; this is a small number that does not permit the identification of low-incidence safety issues if they exist. Second, the longest study to date is of 12 months’ duration. Given that glaucoma is a chronic condition and patients live many years with the disease, the data to date provide no information on the duration of DSLT’s effect beyond one year. In contrast, studies with up to 10 years of data are reported for SLT. Third, the GLAUrious investigators acknowledge that of the total energy delivered to the ocular surface, only about 11% reaches the trabecular meshwork—the target tissue for this therapy. It is reasonable to ask where the remaining 89% of laser energy goes, and what adverse effects such scattered laser energy may have on adjacent ocular structures. Specifically, what effect might perilimbal pigmentation (as is common among patients of African descent) have on laser energy absorption and safety? Corneal pigmentation (and presumed corneal laser absorption) has been identified as a risk factor for corneal complications of standard SLT; will perilimbal pigmentation pose a safety issue for DSLT? Even if such effects are not immediately evident at the time of treatment, what effects might limbal laser energy absorption have on limbal stem cell populations, and might corneal wound healing be impaired in the future? Finally, the benefit of performing SLT without the need for visualization of the target tissue (the TM) means that gonioscopy skills are not required to perform the procedure. However, gonioscopy is essential for determining the need for and appropriateness of SLT as a therapeutic option. This presents a situation in which providers incapable of assessing the indications for SLT can now perform SLT using DSLT, which poses a risk of adverse events related to inappropriate patient selection. For these reasons, while DSLT offers many potential benefits of standard SLT on paper, there are insufficient real-world data to support its widespread adoption before further studies are completed to more robustly characterize the procedure’s efficacy and safety.
Comments
The comment section on the IGR website is restricted to WGA#One members only. Please log-in through your WGA#One account to continue.Log-in through WGA#One
