Is Subthreshold Nanosecond Laser Safe for AMD?
Ophthalmology, June 2019
In preclinical studies and a pilot study, the subthreshold nanosecond laser (SNL) suggested promise in patients with intermediate AMD (iAMD). Building on these findings, Guymer et al. performed a randomized trial of the efficacy and safety of SNL as treatment for iAMD. For patients without signs of late AMD on multimodal imaging (MMI), the authors observed similar progression rates for the SNL and sham groups.
This 36-month, multicenter, double-masked study included 292 patients with bilateral large drusen and no sign of atrophy as seen on optical coherence tomography. Participants were assigned randomly to receive either Retinal Rejuvenation Therapy SNL (2RT, Ellex; n = 147) or a sham procedure (n = 145) in the study eye. Each treatment was given at six-month intervals. The primary efficacy outcome was the time until occurrence of late AMD, defined by MMI.
As the speckled-beam profile of the 2RT laser causes selective RPE loss, it is biologically plausible that the laser’s effect may vary according to the degree of RPE dysfunction. To investigate this, the authors conducted a post hoc comparison of data for patients with and without reticular pseudodrusen (RPD) or pigmentary abnormalities at baseline. Adverse events were documented to assess safety.
Overall, the SNL treatment showed no significant benefit for slowing AMD progression (adjusted hazard ratio [HR], 0.61; p = .122 vs. sham). However, the post hoc analysis found evidence of effect modification based on the coexistence of RPD (adjusted interaction; p = .002). SNL treatment resulted in slower progression in the 222 participants without RPD at baseline (adjusted HR, 0.23; p = .002) and faster but nonsignificant progression in the 70 patients with RPD (adjusted HR, 2.56; p = .112). There were no significant differences in serious adverse events between the study groups. Although no serious events were related to the device, deep retinal hemorrhage occurred in 10 patients (6.8%) at the site of laser delivery.
The efficacy results suggest that SNL treatment may help to slow AMD progression in the absence of RPD, but it could hasten the AMD process in patients with coexisting RPD. Therefore, the authors recommended caution when considering studies of SNL use in patients with RPD phenotypes. Based on evidence from this study, further trials of the 2RT laser in AMD are warranted, they said. (Also see related commentary by Philip J. Rosenfeld, MD, in the same issue.)
The original article can be found here.