Photoreceptor-RPE loss ratio and fundus autofluorescence patterns as predictive factors for lesion progression in geographic atrophy

Purpose: To assess the impact of the ratio between photoreceptor (PR) loss and retinal pigment epithelium (RPE) loss on the progression of geographic atrophy (GA) and to explore correlations between abnormal fundus autofluorescence (FAF) patterns and the PR-RPE loss ratio.

Design: Single-centre, retrospective case series.

Methods: Multimodal images from 87 treatment-naïve patients with GA and a follow-up of 6-24 months were included. Geographic atrophy areas on FAF images and areas of PR-RPE loss on optical coherence tomography images at baseline were manually annotated, and FAF patterns were classified. The impact of these biomarkers on GA progression through month 24 as measured on FAF was evaluated using random slope and intercept models and Spearman correlation coefficients (ρ).

Results: Mean square-root GA growth rate was 0.27 ± 0.28 mm per year. Mean PR-RPE loss ratio at baseline was 2.16 ± 1.75. Fundus autofluorescence patterns "diffuse" and "diffuse trickling" showed higher PR-RPE loss ratios at baseline and contributed statistically significantly to the slope of GA progression (p = 0.01 and p = 0.0019). Baseline GA lesion size was negatively correlated to PR-RPE loss ratios at baseline (ρ = -0.47, p < 0.0001). Overall, GA growth was higher in patients with higher PR-RPE loss ratios at baseline (ρ = 0.35, p = 0.0011), and the ratio's contribution to the slope of GA progression was statistically significant (p = 0.0001).

Conclusion: Eyes with higher PR-RPE loss ratios were more likely to exhibit FAF patterns "diffuse" and "diffuse trickling" and showed higher GA progression rates. Baseline characteristics derived from FAF and OCT images may thus offer information on lesion progression.