The ongoing COAST trial will help to clarify the timing and energy for optimal selective laser trabeculoplasty (SLT) retreatment, Tony Realini, MD, MPH, said Sunday at the 2024 American Academy of Ophthalmology meeting in Chicago. Dr. Realini, a professor and vice chair of clinical research in the department of ophthalmology and visual sciences at West Virginia University and study chair for COAST (Clarifying the Optimal Application of SLT Therapy), provided an update on multicenter SLT clinical trials and new laser technologies during the meeting.
Background: The LiGHT Trial
Dr. Realini began with a recap of the Laser in Glaucoma and Ocular Hypertension (LiGHT) trial, a 3-year study involving 718 subjects that compared SLT to medications. “Outcomes for LiGHT were quite remarkable,” observed Dr. Realini. “Almost 80% of the SLT patients were at target without medications or surgery at 3 years, and 77% of them only needed a single SLT.” Patients in the medication group were more likely to see their glaucoma get worse (5.8% vs 3.8% for SLT), to develop cataracts that required surgery (6.9% vs 3.7% for SLT), or to require glaucoma surgery (1.8% vs none for SLT), he said.1 In addition, SLT is more cost-effective than medications, noted Dr. Realini, and the SLT cohort experienced no sight-threatening complications.
The 6-year results of LiGHT confirmed the 3-year results, with 70% of SLT eyes still medication free; 56% of the eyes were still well controlled with just the single treatment at study entry, said Dr. Realini.2 “That means that the median time to retreatment is more than 6 years, because over 50% hadn’t yet failed at the 6-year mark,” said Dr. Realini. “Again, lower glaucoma progression rates, lower trabeculectomy rates, and lower cataract surgery rates with SLT compared to medications, and again, no serious laser-related adverse events.”
These results have driven a paradigm shift in the United Kingdom regarding glaucoma care, where the National Health Service has adopted an SLT-first approach to glaucoma patients, said Dr. Realini. In the United States, the AAO’s preferred practice pattern recommends SLT as initial or adjunctive therapy.
Figure 1. Current design of the COAST trial. All participants receive a treatment with standard-energy SLT over 360° of the trabecular meshwork at the outset. At month 12, patients are randomized into either a low energy annual treatment group or a group treated with standard energy on a pro re nata basis. (Image courtesy Anthony Realini, MD.)
The COAST Trial
The COAST study, funded by the National Eye Institute, includes 2 trials intended to evaluate both the optimal energy for performing SLT and the frequency with which SLT should be repeated. In the initial study design, participants were randomized to undergo SLT either at standard energy (starting at 0.8 millijoules [mJ] and titrating to fine champagne bubbles) or to low-energy SLT (0.4 mJ), with treatment consisting of 100 treatment spots through the full 360° of the trabecular meshwork (TM) in both eyes.
“The rationale for low energy in COAST is that the TM takes a beating from age, from glaucoma, and from SLT therapy repeated as needed, and the TM eventually stops responding to SLT,” explained Dr. Realini. “You repeat it enough times and you don’t get anything, because there’s been too much cumulative damage. Low-energy SLT minimizes the only modifiable source of TM damage and may extend TM’s responsivity to repeat SLT. We may be able to repeat it more if we do it at lower energy.”
The primary endpoint of this initial 12-month trial was a comparison of eyes achieving target IOP without the need for repeat SLT. Participants were then re-randomized to either receive low-energy SLT, repeated annually, to maintain TM health and function, or to SLT at the initially assigned energy repeated only when IOP rises above target IOP, a pro re nata (PRN) approach that Dr. Realini observed is “essentially rescue therapy for the TM.” The primary endpoint for this trial is a comparison of the 4-year medication-free survival rates between groups.
The trial has since been modified, said Dr. Realini, because when 25% of the study patients reached 12 months, an interim efficacy analysis found that low-energy SLT patients were less likely than standard energy SLT patients to make it to month 12 without needing repeat SLT. “We’re kind of excited, actually, that we were able to answer one of COAST’s questions about 2 years earlier than we expected,” he said. “Initial low-energy SLT does not appear to be as effective as an initial standard-energy SLT, so the low-energy initial arm has been discontinued.”
In the modified COAST trial, all participants receive standard-energy SLT at the outset and are randomized at month 12 into either the low-energy annual treatment group or the standard-energy PRN group (Figure 1). Dr. Realini expects this revised approach will answer the question of which treatment approach is most effective.
A New Approach: Direct SLT
Dr. Realini also discussed a newer approach, direct SLT, in which laser energy is applied directly through the sclera; there is no need for gonioscopy skills to perform this procedure, he noted. The Eagle DSLT laser (Belkin Vision/Alcon) auto-focuses and auto-aligns, then delivers the full treatment in about 2 seconds, he said, and includes safety functions to ensure that the sclera, cornea, or other important nearby structures are not damaged.
“The GLAUrious study (NCT03750201) compared direct vs standard SLT, and at month 12 and every time point throughout showed absolutely comparable IOP with either technique,” he said. “It’s easier, it’s faster, there’s a much better patient experience, and there’s significant potential for low-resource areas with a high disease burden.”3 The Eagle currently is a single-platform laser and may be redundant with equipment that many surgeons already have in their offices to perform SLT, “so there will be some issues that will have to be overcome,” he said.
Communication With Patients Is Critical
After his presentation, Dr. Realini responded to several questions from the panel and audience, including one that asked why many practicing ophthalmologists still prescribe medications as a first-line treatment, rather than SLT, despite the outcomes of the LiGHT trial and other studies.
“I have absolutely come to terms with the fact that SLT is better than meds,” he said. “If you ask everybody in the room, if you were diagnosed tomorrow, everybody in the room would prefer SLT to meds. That is the ultimate meta-analysis. I think the answer is that many doctors haven’t figured out how to talk to their patients about SLT.
“Here’s my spiel: you have glaucoma, and we need to lower your pressure. There are medications — they’re safe, they’re effective, but you must take them every day and you will forget. When you do, your pressure will go up and you have a little bit more damage that day and that will be cumulative over time. Also, they have side effects that make your eyes red and irritated. There’s also a laser treatment that takes 5 minutes here in the office, doesn’t hurt, and is very effective. Most people won’t have to use drops for 5-6-7 years. When it does wear off, you can do the laser treatment again. Personally, if those were my eyes, I would do laser first. What questions can I answer for you to help you decide what’s best for you?”
References
1. Gazzard G, Konstantakopoulou E, Garway-Heath D, et al. Selective laser trabeculoplasty versus eye drops for first-line treatment of ocular hypertension and glaucoma (LiGHT): a multicentre randomised controlled trial Lancet. 2019;393(10180):1505-1516. doi:10.1016/S0140-6736(18)32213-X
2. Gazzard G, Konstantakopoulou E, Garway-Heath D, et al. Laser in Glaucoma and Ocular Hypertension (LiGHT) trial: six-year results of primary selective laser trabeculoplasty versus eye drops for the treatment of glaucoma and ocular hypertension. Ophthalmology. 2023;130(2):139-151. doi:10.1016/j.ophtha.2022.09.009
3. Congdon N, Azuara-Blanco A, Solberg Y, et al. Direct selective laser trabeculoplasty in open angle glaucoma study design: a multicentre, randomised, controlled, investigator-masked trial (GLAUrious). Br J Ophthalmol. 2023;107(1):62-65. doi:10.1136/bjophthalmol-2021-319379
