Selective laser trabeculoplasty (SLT) is as effective as medication in controlling IOP,1 which is why many physicians have adopted it as a first-line treatment to manage glaucoma without the compliance problems associated with medications. SLT is also a valuable adjunct to microinvasive glaucoma surgeries (MIGS) in reducing IOP enough to reduce or eliminate medications.
What are the advantages of combining SLT and MIGS?
Mark J. Gallardo, MD: SLT alone can reduce IOP by about 20% to 30% in most patients,2-4 with efficacy comparable to prostaglandin analogues.1 If we reduce IOP by 25%, that might be enough to move a patient from two medications to one, but may not eliminate medications completely. Likewise, various MIGS devices can reduce IOP and medication use, but they do not always lower IOP enough for patients to be medication-free. If the goal is to get a patient off medications—to avoid compliance problems, address intolerance, or reduce expenses, for example—then we may be able to achieve that with the cumulative effects of both MIGS and SLT.
Savak "Sev" Teymoorian, MD, MBA: Many of us have seen the benefits of using SLT before a MIGS intervention, from SLT’s value over medications as a first-line therapy to its diagnostic advantage in helping to identify which mechanism is creating the greatest outflow resistance. SLT also has the advantage of reducing IOP after MIGS if we need to take it down an extra few points. In my experience, using SLT after MIGS can be a better approach than returning patients to a medication after MIGS.
Like MIGS, SLT is a step in the treatment paradigm between medications. MIGS and SLT are natural partners in reducing IOP without the risk of traditional glaucoma surgeries, such as trabeculectomy or tube shunts, or the compliance issues of medications. When we are already discussing MIGS surgery for glaucoma, possibly in addition to cataract surgery, the idea of augmenting the IOP-lowering effects of those surgeries with a laser treatment makes sense to patients as well. My patients tend to do well with the combination.
What synergistic effects can SLT and ABiC achieve together?
Dr. Gallardo: When you look at how each procedure manipulates the outflow system, it makes sense to combine the two procedures to fully treat the entire conventional outflow system. SLT is known to modify the architecture of the trabecular columns in an atraumatic fashion (unlike argon laser trabeculoplasty), which ultimately leads to an increase in the spaces between these columns and effectively reduces the outflow resistance. Ab interno canaloplasty (ABiC; Ellex) treats the outflow system as well, but addresses areas SLT is unable to reach. Upon circumnavigating the canal with the Ellex iTrack catheter, herniations of the trabecular meshwork-Schlemm canal inner wall complex, which obstruct collector channels, are lysed.
Viscodilation during the procedure also leads to other architectural changes of the conventional outflow system: the spaces between the trabecular columns are expanded, microperforations are created in the inner wall of Schlemm canal, and the canal itself and collector channels are dilated. By coupling both procedures, we are positively manipulating and modifying pathologic changes that occur in the conventional outflow system in glaucoma patients.
Dr. Teymoorian: The ABiC procedure works on all aspects of aqueous outflow, so it makes sense to combine it with SLT to further improve function of the trabecular meshwork, where most aqueous outflow occurs. The ideal result in any procedural intervention is to restore the anatomy back to its natural state. With glaucoma patients, this is achieved by improving the flow of aqueous from the anterior chamber to eventually the collector channels. Both SLT and ABiC aim to meet this goal; therefore, they complement each other very well by working in synergy.
The iTrack pulls trabecular meshwork herniations into the collector channels, breaks inner lumen adhesions, and opens the canal’s stenotic segments. We slowly withdraw the iTrack after it navigates 360° of Schlemm canal, with the technician delivering one or two clicks of viscoelastic about every clock-hour. Herniated inner wall tissue is drawn from the collector channels, compressed tissue planes of the trabecular meshwork are separated, and the collector channels are flushed.
Dr. Gallardo: An important distinction of ABiC is that it restores the natural outflow process, whereas other MIGS procedures and traditional glaucoma surgeries physically alter or bypass the mechanisms of aqueous outflow. Unlike other MIGS procedures that treat only one aspect of aqueous outflow, ABiC works by enhancing function of the eye’s outflow mechanisms—the collector channels, the trabecular meshwork, and Schlemm canal. This comprehensive approach ensures that we address the area of maximum outflow resistance for each patient, no matter where it resides.
SLT has a similarly restorative effect. SLT stimulates cellular regeneration in the trabecular meshwork to make it healthier and more porous, improving aqueous outflow. This effect is synergistic with ABiC’s enhancement of the natural outflow channels. Neither technology damages tissue, alters the eye’s mechanics, or involves implanting a device in the eye.
What patients are best suited for SLT after MIGS?
Dr. Teymoorian: A typical case where I might use SLT after MIGS is a patient who is on two or three drops, has uncontrolled glaucoma, and is intolerant to the medications or is having trouble paying for them. In this situation, a combination of procedures is needed to achieve the necessary IOP reduction. I would use SLT as both a therapeutic and also a diagnostic tool. If a session of SLT reduces IOP, then it also demonstrates the viability of the natural outflow channel. This supports the thought process that ABiC will deliver its expected efficacy. ABiC has been shown to have low complication rates like other MIGS procedures,5 and it reduces IOP about 30% while cutting patients’ medication burden in half.6
ABiC and iTrack are trademarks of Ellex. © Ellex 2017. All other brand/product names are the trademarks of their respective owners.
1. Freitas AL, Ushida M, Almeida I, et al. Selective laser trabeculoplasty as an initial treatment option for open-angle glaucoma. Arq Bras Oftalmol. 2016;79(6):417-421.
2. Nagar M, Ogunyomade A, O’Brart DP, et al. A randomised, prospective study comparing SLT with latanoprost for the control of intraocular pressure in ocular hypertension and open angle glaucoma. Br J Ophthalmol. 2005;89(11):1413-1417.
3. Melamed S, Simon GJB, Levkovitch-Verbin H. Selective laser trabeculoplasty as primary treatment for open-angle glaucoma. Arch Opthalmol. 2003;121(7):957-960.
4. Katz LJ, Steinmann WC, Kabir A, et al. Selective laser trabeculoplasty versus medical therapy as initial treatment of glaucoma: a prospective, randomized trial. J Glaucoma. 2012;21(7):460-468.
5. Khaimi MA. Canaloplasty: a minimally invasive and maximally effective glaucoma treatment. J Ophthalmol. 2015;2015:485065.
6. Khaimi MA, Gallardo MJ. 228-eye ABiC 12-month case series data. Presented at ASCRS; May 6-10, 2016; New Orleans, LA.