Subthreshold Nanosecond Laser in Age-Related Macular Degeneration: Observational Extension Study to the LEAD Clinical Trial.

Abstract Purpose To evaluate the long-term effect of subthreshold nanosecond laser (SNL) treatment on progression to late age-related macular degeneration (AMD). Design Observational extension study to a randomized, sham-controlled trial. Participants Two-hundred and twelve participants with bilateral large drusen. Methods The Laser Intervention in the Early Stages of AMD (LEAD) study is a 36-month trial where participants were randomized to receive SNL or sham treatment in one eye at 6-monthly intervals up to 30-months. After the completion of the LEAD study, the two largest recruiting sites offered remaining participants an opportunity to enrol in a 24-month observational extension study. This study thus examined all participants from these two sites that were enrolled in the LEAD study at baseline, including the additional observational data. Main Outcome Measures Time to develop late AMD defined on multimodal imaging between those randomized the SNL or sham treatment. Results Overall, there was no significant difference in rate of progression over a 60-month period in those randomized to the SNL compared to sham group (adjusted hazard ratio [HR] = 0.63; 95% confidence interval [CI] = 0.36 to 1.09; P = 0.098), similar to the findings at 36 months in the LEAD study. However, there continued to be evidence of treatment effect modification based on the coexistence of reticular pseudodrusen (RPD; adjusted interaction P = 0.007). Namely, progression was significantly slowed with SNL treatment for those without coexistent RPD (adjusted HR = 0.34; 95% CI = 0.16 to 0.71; P = 0.004), but it was not significantly different for those with RPD (adjusted HR = 1.81; 95% CI = 0.67 to 4.88; P = 0.239). Conclusions A 24-month observational extension study to the LEAD trial confirmed that SNL treatment did not significantly reduce the overall rate of progression to late AMD in a cohort with intermediate AMD. However, the persistence of a potential beneficial treatment effect in those without coexistent RPD over a longer follow-up duration of an additional 24 months without additional treatment is encouraging. These findings provide further justification for future trials to examine the potential value of SNL treatment for slowing progression in intermediate AMD.