Exploring SLT efficacy for prior incisional glaucoma surgery

Reviewed by Leah L. Kammerdiener, MD

Charleston, SC-Although microinvasive glaucoma surgery is perhaps the hottest topic in glaucoma right now, subspecialists need other tried-and-true tools in their armamentarium to lower IOP.

Selective laser trabeculoplasty (SLT) is a reasonable treatment option to lower IOP in glaucoma patients who have had previous glaucoma surgery, said Leah L. Kammerdiener, MD, a resident with Storm Eye Institute, Medical University of South Carolina (MUSC), Charleston.

“For general ophthalmologists, this can be a great way to try something before sending them back to the glaucoma surgeon or sending them off for surgery again,” Dr. Kammerdiener said.

The study was a retrospective electronic medical records review performed on patients who had SLT between February 2014 and September 2015 at MUSC. Dr. Kammerdiener and co-investigator, Allan Sharpe, MD, compared 53 patients with prior trabeculectomy with the ExPress shunt (Alcon Laboratories), Ahmed valve implantation (New World Medical), or cataract surgery with trabeculectomy with controls (also 53 patients) who had no history of glaucoma surgery.

Exclusion criteria included other intraocular surgeries except cataract extraction or those who had missing study parameters.

Each SLT treatment was 50 spots across 180° of trabecular meshwork.

About the study

Researchers analyzed IOP before SLT as well as at 1-, 6-, and 12-month intervals after SLT.

Researchers found that both the treatment and control group patients had a statistically significant drop in IOP at 1 month.

Before SLT, the mean IOP was 19.2 mm Hg in the prior glaucoma surgery group, which dropped by a mean of 9.3% (1.8 mm Hg). In the group with no prior surgery, the mean IOP was 20.6 mm Hg, which also dropped by 8.8% (1.8 mm Hg).

Thirty-five eyes in the prior glaucoma surgery group and 29 in the no prior surgery glaucoma group had a second SLT.

Overall, one or two SLT treatments led to a more than 20% IOP reduction in 28.3% and 24.5% of eyes after the first SLT in the prior glaucoma surgery and no prior glaucoma surgery groups.

“Overall, 27.9% of prior glaucoma surgery and 31.7% of no prior surgery patients had a 20% or greater IOP drop at one year,” Dr. Kammerdiener said.

Researchers also analyzed how SLT helped patients with an IOP of 21 mm Hg or higher, and they found a 15% to 20% drop.

“That’s important because if those patients are noncompliant or on maximum medical therapy and they still have higher pressures, this helps us to bring their pressures down,” she said.

Significance of study

The findings are important because little has been published about the efficacy of SLT after glaucoma surgery. However, Dr. Kammerdiener said this study helps support the use of SLT as an effective procedure following incisional glaucoma surgery.

Some ways to expand the research would be to use a larger study population with a wider range of glaucoma types, Dr. Kammerdiener said.

Her institution traditionally sees African American and white patients who have open-angle glaucoma, so the study was limited by those factors, she explained.

She also would like to see if the results from the study would remain steady after more than a year and how results would change in a prospective study.

Leah L. Kammerdiener, MD

E: lkammerdiener@gmail.com

This article was adapted from Dr. Kammerdiener’s presentation at the 2016 meeting of the American Society of Cataract and Refractive Surgery. Dr. Kammerdiener did not indicate any proprietary interest.