Findings from a recent study published in Ophthalmology Glaucoma compared the efficacy, duration of effect, and safety of the four most significant selective laser trabeculoplasty (SLT) treatment protocols.
Give me some background first.
As a potential first-line treatment for glaucoma and ocular hypertension (OHT), SLT improves the aqueous outflow through the trabecular meshwork while minimizing structural damage and stimulating tissue remodeling.
As the clinical treatment technique is not standardized, there tends to be variation in the treatment area, number of laser applications, and laser power setting.
Now, talk about the study.
In this multicenter, masked, and randomized controlled trial, a Swedish research team analyzed the treatment outcomes of 400 patients with glaucoma or OHT who underwent SLT with either 50±5 laser spots in 180° or with 100±10 spots in 360°.
And the laser power?
The laser power was titrated to either just below the cavitation bubble level (“standard energy”) or to a level producing cavitation bubbles at 50-75% of laser applications (“high energy”).
As such, the four SLT treatment protocols evaluated included:
- 180°/standard energy
- 180°/high energy
- 360°/standard energy
- 360°/high energy
What were the primary outcome measures?
- Reduction of intraocular pressure (IOP) 1-6 months after SLT
- Proportion of patients achieving a 20% IOP reduction without further intervention (success rate)
- Time to glaucoma treatment using a Kaplan-Meier survival analysis.
Tell me more about the cohort.
Study participants were both treatment-naive patients and patients undergoing glaucoma treatment at different stages of disease.
Findings?
SLT conducted with the 360°/high energy protocol was shown to be superior in all primary endpoints of the study.
In terms of IOP reduction 1-6 months following SLT, the four treatment protocols resulted in a decrease of (p<0.001):
- 180°/standard energy: 3.4mmHg
- 180°/high energy: 3.2mmHg
- 360°/standard energy: 4.2mmHg
- 360°/high energy: 5.4mmHg
What about the success rate?
The success rate after 6 months was significantly higher for the 360°/high energy treatment protocol at 58.3% (p<0.001), compared with:
- 30.2% ( 180°/standard energy)
- 29.3% (180°/high energy)
- 41.7% (360°/standard energy techniques)
And the time to glaucoma treatment escalation?
The median time was more than twice as long, with 360°/high energy SLT at 1,323 days (p<0.001).
In comparison, the time to glaucoma treatment escalation for the three other SLT protocols were:
- 180°/standard energy: 437 days
- 180°/high energy: 549 days
- 360°/standard energy: 620 days
Anything else?
Of note, postoperative discomfort was observed more frequently with the 360°/high energy SLT protocol; however symptoms were generally mild and temporary.
Treatment-naive eyes achieved the most IOP reduction from 360°/high energy SLT, followed by eyes with previous laser treatments, previous pharmacological treatments, and eyes that received both prior laser and medication.
Any limitations?
Yes. The study authors noted that the study did not include specific patients in their analysis, such as those with:
- A baseline IOP below 18mmHG
- Pigmentary glaucoma
- Close angle glaucoma
- Eyes that had undergone glaucoma surgery
Expert opinion?
The authors emphasized that each patient must be assessed individually.
“In some cases, such as patients with pigment dispersion glaucoma, or a history of uveitis or macular edema, a milder treatment may be appropriate.”
“Further, the entire anterior chamber angle is not always accessible, and one must settle for a slightly smaller treatment area,” they wrote..
Take home.
Based on these findings, the magnitude and duration of SLT results significantly increase—while not compromising safety—when performed using the 360°/high energy protocol.
As such, the study authors recommended that the 360°/high energy SLT protocol be considered the standard of care, as it will likely lead to fewer SLT re-treatments, a reduced medication burden of glaucoma drops, and decreased need for glaucoma surgery.