COMMENTARY

Open-Angle Glaucoma Treated With MicroPulse Laser

Shuchi B. Patel, MD

Disclosures

April 19, 2016

MicroPulse Laser Trabeculoplasty for the Treatment of Open-Angle Glaucoma

Lee JW, Yau GS, Yick DW, Yuen CY
Medicine (Baltimore). 2015;94:e2075

Study Summary

The aim of this study was to investigate the safety and efficacy of using MicroPulse laser trabeculoplasty (MLT), first developed by IRIDEX (Mountain View, California), in the treatment of open-angle glaucoma.

A single session of unilateral MLT treatment was delivered using a 577-nm diode laser to 360º of the trabecular meshwork (TM) to reduce intraocular pressure (IOP) or medication load. This prospective cohort included patients aged 18 years or older with an open angle on gonioscopy and with glaucomatous optic neuropathy evident from optical coherence tomography.

Follow-up was done for at least 6 months, while medications were titrated up or down at 1 month after laser to achieve a 25% IOP reduction from presentation or an IOP < 18 mm Hg, whichever was lower. The following were compared: IOP, on presentation, pre-MLT, day 1, 1 week, 1 month, 3 months, and 6 months after MLT; and the number of medications, on pre-MLT, 3 months, and 6 months after MLT.

The adverse effects noted included mild uveitis that required no treatment in 7.5% of patients, with no loss of Snellen visual acuity in any of the patients at 6 months. During the first 6 months, only 2.1% required a repeated laser trabeculoplasty. Both the IOP and the number of medications were significantly reduced at all time intervals following MLT compared with the pre-MLT level. At 6 months, the IOP was reduced by 19.5%, while there was a 21.4% reduction in medication use compared with pretreatment levels. The MLT success rate for achieving at least a 25% reduction or an IOP of < 18 mm Hg was 72.9%.

Viewpoint

MicroPulse laser technology uses a duty-cycle algorithm that delivers subthreshold treatment to ocular tissues without scar formation. This makes it safe for use in various retinal pathologies,[1] even those that require application of the laser directly over the fovea, and glaucoma.

MicroPulse technology can be used for the treatment of open-angle glaucoma using a laser trabeculoplasty procedure that delivers laser energy at low-irradiance 300-ms pulses to the pigmented cells in the TM. The mechanism of action is thought to be that the laser stimulates a release of cytokines that increases the permeability of the TM and reduces IOP.

Compared with argon laser trabeculoplasty (ALT) and similar to selective laser trabeculoplasty (SLT), MLT causes no structural damage to the TM. Compared with SLT, due to only a 15% active duty cycle of the MLT versus 100% with SLT, MLT has a potential advantage of not destroying the pigmented TM cells.[2]

There are limited direct comparisons of the efficacy of MLT versus SLT or ALT, but this study shows success rates similar to that seen in studies of ALT and SLT[3,4] in lowering IOP, with the potential benefit of causing less structural and histologic damage to ocular tissues. This also may make the procedure repeatable more often than SLT, with sustained efficacy of the repeated treatments.

The procedure is performed in a similar fashion to SLT, with a spot size of 300 microns and confluent placement of the spots, making it easily adaptable by physicians already performing laser trabeculoplasty.

The limitations of applying this procedure to clinical practice probably are not due to the adaptability of the procedure by physicians, adverse effects, or questionable efficacy, but rather to the cost of acquiring the laser. Physicians who already own an argon laser or a Q-switched YAG may find the investment in a new laser that produces similar results to be cost-prohibitive. On the other hand, for a multispecialty group or a comprehensive ophthalmologist offering both retina and glaucoma care to patients, the laser could prove to be useful because it may be used for retinal cases that other lasers are not as suited for; in those practices, this laser may be a good investment. And as opposed to SLT, which has no other treatment roles, MLT may be preferred for its diverse use.

Given the comparable success rates of MLT to SLT and ALT, this is another procedure that can be added to bridge the gap in treatment from medical management to surgical intervention. Head-to-head studies comparing MLT with ALT and SLT should be performed to help further elucidate the role of MLT in clinical practice.

Abstract

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