Selective laser trabeculoplasty (SLT) emerged in the late 1990s: a frequency-doubled, Q-switched Nd:YAG laser delivering nanosecond pulses that selectively target pigmented trabecular meshwork cells while sparing surrounding non-pigmented tissue. This selectivity made SLT safer than its precursor argon laser trabeculoplasty, repeatable and eventually positioned it as a viable first-line therapy. The landmark LiGHT trial cemented that reputation, showing that SLT provides better long-term IOP control than drops alone, reduced medication burden and reduced the need for incisional surgery over six years.¹ 

Despite its success, the procedure has practical friction points. It requires a gonioscopy lens, coupling gel and manual rotation of a gonioscopy lens while roughly 100 laser spots are applied. This process can take several minutes and be ergonomically demanding, both for patients with neck or positioning limitations and for providers performing many treatments.

Treatment settings screen allowing the doctor to choose the energy to use and the eye to treat. Click image to enlarge.

Direct Selective Laser Trabeculoplasty (DSLT)

This version of the procedure was designed specifically to remove some of these practical friction points. Rather than requiring a gonioscopy lens, DSLT is delivered non-contact, transscleral and translimbal using image-guided automation. DSLT eliminates the need for a gonio lens and coupling medium and allows 360° treatment by delivering laser pulses through the overlying limbal tissue. A lid speculum is used and, like SLT, proparacaine or tetracaine can be used to decrease some of the “feeling” of the treatment. The only commercially developed DSLT platform to date is the Voyager system Alcon).²

Initial setup to obtain limbal tracking. The goal is to place the crosshair in the middle of the white circular image and ensure the lower left box is green. Once that has been achieved, by pressing the “Next” button, limbal alignment will occur. Click image to enlarge.

Performing the Procedure

DSLT begins with placement of the lid speculum and application of proparacaine or tetracaine. The patient is positioned in the chin rest, and the device’s eye-tracking and imaging system automatically locates the limbus with assistance from the doctor. The doctor can adjust alignment and, once satisfied with alignment, with the push of a button the system applies a rapid, automated sequence of 120 laser spots in a circular pattern around the full 360° of the angle. The entire 360° of the trabecular meshwork is treated in about two to three seconds.^2,3

Show Me the Data

The pivotal study for DSLT is the GLAUrious Study—a prospective, multicenter, randomized controlled noninferiority trial that enrolled participants aged 40 and older with open-angle glaucoma or ocular hypertension on zero to three hypotensive medications, with washout IOP between 22mm Hg and 35mm Hg. In the study, 192 participants were randomized 1:1 to DSLT (n=99) or conventional SLT (n=93), with IOP followed through 12 months.²

When 156 participants were analyzed at six months, mean washout IOP reduction from baseline was 5.5mm Hg (-20.6%) after DSLT vs. 6.2mm Hg (-23.6%) after conventional SLT. The trial did not formally demonstrate statistical noninferiority at six months.²

The 12-month data mean non-washout IOP reduction from screening was 3.2mm Hg for both DSLT (-12.2%) and SLT (-9.4%), with no significant difference between groups. Over half of patients remained medication-free at 12 months—61.7% in the DSLT group and 59.5% in the SLT group. Safety outcomes were comparable between treatments, with adverse events generally mild and self-limited.²

Limbal tracking has been obtained. The next step is to initiate treatment. Click image to enlarge.

Patient Selection

The DSLT candidate resembles the standard SLT candidate: open-angle glaucoma—including pigmentary or exfoliative glaucoma—or ocular hypertension, with IOP between 22mm Hg to 35mm Hg off medication, and a gonioscopically open angle for the full 360°. Visualization of the limbus is also required, since DSLT relies on automated visualization rather than the use of a gonioscopy lens. This type of SLT is an attractive option for high-volume settings, patients who struggle with traditional slit-lamp positioning, patients who are anxious about eye contact procedures or patients whose anatomy makes gonio lens placement difficult.

Post-op Considerations

Like traditional SLT, after DSLT there are minimum postoperative restrictions. We most commonly treat both eyes the same day and joke, “You can drive yourself to breakfast or lunch right after.” We no longer do an in-office aqueous suppressant after either SLT or DLST postoperatively to prevent IOP spikes. There are no post-op medications required after DSLT. If the patient is using topical glaucoma drops preoperatively, our most common goal is to stop one glaucoma drop immediately post-laser. Glaucoma medication titration after DSLT is really patient-to-patient specific depending on target pressures and glaucoma severity.

Our follow-up schedule post-DSLT is most commonly an IOP check around eight to 12 weeks post-laser. DSLT is a very safe procedure, reinforced by zero serious ocular adverse events in the GLAUrious trial.² For patients preceding their follow-up, the most common adverse event for patients to be aware of is limbal petechial hemorrhages. Second, similar to SLT with inducing inflammation, there have been reports of post-op discomfort immediately after laser.

At the follow-up, this is another timepoint to evaluate maintaining or reducing glaucoma medications. An important point is, aligning with SLT, DSLT has a 10-day global period, so subsequent visits should be billed to insurance. Routinely, a new visual field/OCT is performed three to six months post-laser as a new baseline.

The treatment summary allows the doctor to review spots delivered, energy setting, total energy, limbal tracking, manual limbal tracking and the actual spots delivered. Click image to enlarge.

Where DSLT Wins

We believe DSLT’s number one positive attribute is convenience. From a doctor perspective, you can deliver bilateral laser trabeculoplasty in mere minutes. Gonioscopy in glaucoma is a needed skill but, for the doctor who’s becoming more proficient assessing the angle, DSLT offers a simplified, rapid, efficient way of delivering laser energy to treat the eyes’ conventional outflow pathway.

For the patient, convenience is also a winning proposition with DSLT. Performing DSLT in a clinical setting streamlines scheduling, follow-ups and transfers to a surgical facility. The patient can receive a procedural intervention bilaterally with minimum to zero post-op restrictions or worries.

Laser trabeculoplasty volumes have tripled in the US over the last decade.⁴ Optometrists currently and will continue to play a vital role in recommending laser intervention, performing laser trabeculoplasty (depending on your state of licensure) and managing glaucoma patients after laser treatment. DSLT is an added tool in the laser treatment toolbox to lower IOP and treat glaucoma. For both doctors and patients, DSLT offers another treatment option that can win with convenience. 

Dr. Ibach specializes in advanced anterior segment surgery care and pathology at Vance Thompson Vision in Sioux Falls, SD. He is a fellow of the American Academy of Optometry (AAO). He has a consulting agreement with Alcon.

Dr. Schweitzer is a cornea, glaucoma, cataract and refractive surgery specialist at Vance Thompson Vision in Sioux Falls, SD. He is a fellow of the AAO. He has a consulting agreement with Alcon.

Dr. Lighthizer is the dean, director of CE and chief of specialty care clinics at the NSU Oklahoma College of Optometry. He is a founding member and immediate past president of the Intrepid Eye Society.