September 2019

GLAUCOMA

Presentation Spotlight
Non-invasive, laser trabeculoplasty for IOP reduction


by Stefanie Petrou Binder, MD EyeWorld Contributing Writer

“We know that laser has a better safety profile than medical or surgical therapy, and it is cost effective. Evidence shows that LT in some elderly patients eliminated any further need for medical therapy.”
—Anastasios Konstas, MD


In glaucoma surgery, the less invasive, the better. Fortunately, laser and ultrasound technologies employed as primary or adjunctive therapies seem to offer viable, less invasive options. According to Anastasios Konstas, MD, PhD, in a presentation at the 23rd European Society of Cataract and Refractive Surgeons Winter Meeting, non-invasive procedures can be reasonably effective in lowering IOP while offering improved safety over more invasive surgeries.
“Today, non-invasive glaucoma procedures (NIGP) do not require eye penetration, differentiating them from MIGS, which requires small incisions and instruments entering the eye,” Prof. Konstas said. “Evidence suggests that the success of laser trabeculoplasty is greater when employed as initial therapy or early in stepwise medical therapy. The perception of limited success of this treatment in the past was influenced by the use of laser as a ‘last resort’ before filtering surgery.”

Current and emerging NIGP

NIGPs include the established argon laser trabeculoplasty (ALT) as well as more recent additions, such as selective laser trabeculoplasty (SLT) and micropulse laser trabeculoplasty (MLT). Some of the newest innovations comprise procedures such as deep wave trabeculoplasty, therapeutic ultrasound, and ultrasonic circular cyclocoagulation.
Laser trabeculoplasty (LT) was shown to be successful in lowering IOP for OAG patients. The mechanisms of LT action are not fully understood, and evidence is lacking to support the superiority of any particular form of laser. One theory on the mechanism of action of LT says that laser burns induce contracture and stretching of the adjacent tissues, thereby widening the trabecular pores. Another theory proposes a cellular mechanism action, in which LT induces cell division with subsequent renewal of cellularity. A biochemical mechanism of action suggests the renewal of MMPs on the beams and stimulation of macrophages as the means by which LT ultimately reduces IOP. These mechanisms of action are thought to work together and are not mutually exclusive.

ALT

ALT is the most tried and tested NIGP. It treats the trabecular meshwork aiming to enhance the outflow facility. IOP reduction with ALT was 24–30% a year after treatment in one investigation, however, all researchers have documented a gradual decline in efficacy over time, as with lasers overall.
Evidence suggests that primary ALT lowered IOP more than initial therapy with timolol and was at least as effective in preserving visual field and optic disc status over a period of more than 5 years. Other data shows that primary SLT had similar IOP-lowering effects as latanoprost over 12 months of follow-up. More recently, SLT employed as sole therapy was shown to be very effective, reducing IOP between 29% and 39%, with patients achieving and maintaining target IOP after 12 months and demonstrating a success rate of almost 80%.
“LT could be a very interesting choice for therapy particularly in patients with exfoliative glaucoma,” Prof. Konstas said. “We know that laser has a better safety profile than medical or surgical therapy, and it is cost effective.
Evidence shows that LT in some elderly patients eliminated any further need for medical therapy. Another study on long-term efficacy of primary ALT showed the probability of success (no additional therapy) in exfoliation patients was 80% after 2 years, 54% after 5 years, and 36% after 8 years.”

SLT

Prof. Konstas thinks that SLT may prove to be a cost-effective and successful strategy as initial or stepwise therapy, specifically in eyes with exfoliative glaucoma, as this treatment targets pigment, which is abundant in this form of glaucoma. Evidence suggests that SLT was effective in reducing IOP by almost 30% when used as initial therapy in open angle glaucoma patients and by roughly 31% when used as adjunctive therapy in exfoliation patients.
In a review of the clinical usefulness of SLT in eyes with exfoliative glaucoma, Prof. Konstas and his colleagues noted a greater IOP reduction and decreased burden of multiple medical therapies.1 “The pigment-laden trabecular meshwork enhances the absorption of laser energy and thus augments the biological effect induced by this treatment,” he explained.

Newer techniques

MLT delivers energy in repetitive microsecond pulses followed by a rest period, thereby reducing any buildup of thermal energy. There is no observable coagulative damage to the trabecular meshwork, and it seems to have a similar efficacy as SLT over a 52-week follow-up period, with less discomfort during and after the procedure, a recent study showed. An investigation in a small group of exfoliative glaucoma patients insufficiently controlled on a prostaglandin revealed a significant IOP reduction up to 12 months after MLT, with 52% of patients demonstrating at least a 20% IOP reduction.
“The reasonably good efficacy and superior safety profile it displays have made SLT increasingly popular in glaucoma practices worldwide. Expanding indications could include PACG (when some angle is visible). Although promising, today there is insufficient controlled evidence for the success of MLT,” Prof. Konstas said.

About the doctor

Anastasios Konstas, MD, PhD
Professor of ophthalmology
Aristotle University of Thessaloniki
Thessaloniki, Greece

Contact information

Konstas: konstas@med.auth.gr

Reference

1. Katsanos A, et al. A review of the clinical usefulness of selective laser trabeculoplasty in exfoliative glaucoma. Adv Ther. 2018;35:619–630.

Relevant financial interests

Konstas
: None

Non-invasive, laser trabeculoplasty for IOP reduction Non-invasive, laser trabeculoplasty for IOP reduction
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