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SLT fails to reduce IOP in follow-up treatment
SLT performed after combined phaco and ab interno trabeculectomy did not lower IOP.
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Selective laser trabeculoplasty is ineffective as follow-up treatment for failed combined phacoemulsification cataract extraction and ab interno trabeculectomy, according to a study.
OSN Glaucoma Board Member Douglas J. Rhee, MD, and colleagues retrospectively reviewed the medical records of 14 eyes of 13 patients who underwent SLT at the Massachusetts Eye and Ear Infirmary between March 2010 and July 2012 after combined Trabectome (NeoMedix) and phacoemulsification failed to reduce IOP.
Rhee said he was surprised by the outcomes of the study, which appeared in the American Journal of Ophthalmology.
“We thought SLT would be more successful, which is why we conducted the study in the first place,” he said. “But we quickly learned that it was not.”
100% failure
“Selective laser trabeculoplasty is not a good follow-up therapy,” Rhee, who performed all the SLT procedures, said. “We achieved a 100% failure rate within 4 months.”
Douglas J. Rhee
Failure was defined solely as lowering of IOP less than 3 mm Hg.
Rhee said he and colleagues have undertaken a number of efforts to try to ascertain the position of ab interno trabeculectomy in the treatment algorithm for glaucoma, which has a success rate of roughly 41% at 1 year and about 25% to 30% at 2 years.
Rhee participated in one of the initial proof-of-concept case series of ab interno trabeculectomy. From 2006 to 2010, he and colleagues at the University of Southern California compared primary trabeculectomy with ab interno trabeculectomy.
In another study with other collaborators, he said, “We found that trabeculectomy performed after a failed ab interno trabeculectomy has the same success rate as primary trabeculectomy. So rather than relying on trabeculectomy for follow-up surgery, [we asked] can you perform SLT?”
In the current study, the average patient age at follow-up SLT intervention was 74.8 years (range: 69.4 to 80.3 years), with eight women and five men. Ten patients had open-angle glaucoma, and three patients had pseudoexfoliation glaucoma.
Ab interno trabeculectomy was the only incisional surgical procedure done to manage glaucoma; however, three eyes had undergone argon laser trabeculoplasty, one eye underwent SLT, and two eyes were subjected to both ALT and SLT.
SLT was performed with an Ocular Latina SLT Gonio Laser lens (Ocular Instruments) that focused the Coherent Selecta 7000 laser (Lumenis) onto the pigmented trabecular meshwork. The SLT laser is a frequency-doubled Q-switched Nd:YAG laser with a wavelength of 532 nm.
In all cases, previous ab interno trabeculectomy had ablated between 90° and 120° of nasal trabecular meshwork.
Speculated cause
Rhee surmised that the failure may be due to the fact that SLT does not allow for treatment of the entire trabecular meshwork.
“Ab interno trabeculectomy involves removal of approximately 33% to 40% of the meshwork,” he said. “However, we do not know what the results would be from some of the less-invasive angle bypass shunts,” such as the iStent (Glaukos) or the Hydrus (Ivantis).
With such outcomes for SLT, Rhee said that surgeons should use trabeculectomy for follow-up surgical intervention.
“It works just as well as trabeculectomy performed in a primary setting,” he said.
Although the current study was limited to SLT as an intervention, the literature demonstrated that ALT and SLT are equivalent as follow-up interventions in this patient population, according to Rhee.
With the study’s 100% failure rate for follow-up SLT, ab interno trabeculectomy may not be the best procedure to do first, he said. – by Bob Kronemyer
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Perspective
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Brian A. Francis, MD
This retrospective study reports the efficacy of selective laser trabeculoplasty (SLT) after failed phaco-Trabectome surgery. The concept of laser trabeculoplasty after glaucoma surgery is not new and has been explored after failed trabeculectomy.
There are a number of points that merit discussion. The first is that this is a small, retrospective case series of 14 eyes with some loss of follow-up over time. For example, the number of evaluable subjects at 6 months is one in 12. The success criteria are somewhat stringent for a noninvasive laser procedure and are similar to surgical success criteria for the Tube Versus Trabeculectomy (TVT) Study. The mean IOP did decrease, and the success rate was more than 40% at 3 months, but dropped off to 23% between 6 and 10 months.
The conclusion of the authors is that SLT after failed phaco-Trabectome is likely to fail and that incisional surgery should be considered in these patients. They do note, however, that this is a relatively high risk for failure group, with most patients having failed maximal medical therapy twice (prior to surgery and prior to laser), and that many of them had failed laser prior to surgery.
As a clinician, I would still consider SLT after failed angle-based glaucoma surgery, with the following stipulations. There must be at least 180° of intact, treatable trabecular meshwork. The patient must understand the limited chance of success and that this may be a temporary measure. Those who are poor surgical candidates or at high risk for filtration surgery may be considered. Like any other glaucoma treatment, it may be appropriate for some patients but not others. Our challenge is to try to determine which treatments are most appropriate and tailor the type of treatment to the particular patient’s needs.
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