GA area measured by SD-OCT shows good correspondence with FAF-based measurements in patients enrolled in the FILLY trial

Abstract

Purpose : To compare spectral-domain optical coherence tomography (SD-OCT) and fundus autofluorescence (FAF) measurements of geographic atrophy (GA) secondary to age-related macular degeneration (AMD) in patients enrolled in the FILLY trial.

Methods : In this post-hoc explorative study, SD-OCT images from the phase 2 FILLY clinical trial were analyzed. The phase 2 FILLY trial was a sham controlled clinical study of intravitreal pegcetacoplan, targeting complement C3, for patients with GA secondary to AMD. A-scan based manual annotation of complete loss of retinal pigment epithelium (RPE) was performed on whole baseline and year one OCT volumes. The RPE-loss measured on OCT was compared to the hypofluorescent GA areas measured on FAF by the centralized reading center of the FILLY trial. The correlation between the GA areas in mm² from baseline and year 1 was reported using Pearson’s correlation coefficient (r) and coefficient of determination (R²). In addition the limits of agreement were evaluated with Bland-Altman plots.

Results : 144 OCT volumes of 144 patients at baseline and 111 OCT volumes of 111 patients at year 1 from the FILLY trial were included, resulting in a total of 12 495 manually annotated B-scans. The comparison of GA areas measured on FAF and the RPE-loss measured on OCT revealed a correlation coefficient of r = 0.97 with an R² = 0.86 at baseline and r = 0.97 with an R² = 0.81 at year 1 (Figure 1). The Bland-Altman plots comparing the GA areas assessed on both imaging modalities show a bias towards higher GA area measurements assessed by FAF as compared to OCT, especially in larger lesions at year 1. Mean difference in measured GA areas between the two imaging modalities was 0.91 ± 0.95 mm² at baseline and 1.28 ± 1.23 mm² at year 1 (Figure 2).

Conclusions : Our results show a very good correlation of GA measurement between FAF and OCT. Given the fact that OCT has become more established than FAF, this is an essential finding for the design and endpoints in future clinical trials as well as disease monitoring in clinical practice, especially once a treatment will be available.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.